AU4700096A - Immunogenic compositions containing recombinant attenuated poxviruses expressing htlv antigens - Google Patents

Description

Immunogenic compositions containing recombinant attenuated poxviruses expressing HTLV antigens. RELATED APPLICATIONS

This application is a continuation-in-part of

application Serial No. 08/105,483, filed August 12, 1993, which in turn is a continuation of application Serial No.

07/847,951, filed March 6, 1992, which in turn is a

continuation-in-part of application Serial No.

07/713,967, filed June 11, 1991, which in turn is a

continuation-in-part of application Serial No.

07/666,056, filed March 7, 1991, now allowed application

Serial No. 08/036,217, filed March 24, 1993, and issued

November 15, 1994 as U.S. Patent No. 5,364,773.

Reference is made to application Serial No. 08/223,842, filed April 6, 1994, as a continuation-in-part of

application Serial No. 07/897,382, filed June 11, 1992, which in turn is a continuation-in-part of application

Serial No. 07/715,921, filed June 14, 1991. Mention is

also made of co-pending application Serial No.

08/184,009, filed January 19, 1994 as a continuation-in- part of application Serial No. 08/007,115, filed January

20, 1993. Each of the aforementioned and above- referenced applications and patent are hereby

incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a modified poxvirus and to methods of making and using the same; for

instance, a vaccinia virus or avipox (e.g. canarypox or fowlpox), e.g., ("HTLV") modified recombinant poxvirus- human T-cell leukemia virus, such as an attenuated

recombinant, especially a NYVAC or ALVAC HTLV

recombinant. More in particular, the invention relates to improved vectors for the insertion and expression of foreign genes for use as safe immunization vehicles to

elicit an immune response against HTLV virus. Thus, the invention relates to a recombinant poxvirus, which virus expresses gene products of HTLV and to immunogenic compositions which induce an immunological response against HTLV infections when administered to a host, or in vitro (e.g., ex vivo modalities) as well as to the products of expression of the poxvirus which by

themselves are useful for eliciting an immune response e.g., raising antibodies, which antibodies are useful against HTLV infection, in either seropositive or

seronegative individuals, or which expression products or antibodies elicited thereby, isolated from an animal or human or cell culture as the case may be, are useful for preparing a diagnostic kit, test or assay for the

detection of the virus, or of infected cells, or, of the expression of the antigens or products in other systems. The isolated expression products are especially useful in kits, tests or assays for detection of antibodies in a system, host, serum or sample, or for generation of antibodies.

Several publications are referenced in this

application. Full citation to these references is found at the end of the specification immediately preceding the claims or where the publication is mentioned; and each of these publications is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

Vaccinia virus and more recently other poxviruses have been used for the insertion and expression of foreign genes. The basic technique of inserting foreign genes into live infectious poxvirus involves

recombination between pox DNA sequences flanking a foreign genetic element in a donor plasmid and homologous sequences present in the rescuing poxvirus (Piccini et al., 1987).

Specifically, the recombinant poxviruses are

constructed in two steps known in the art and analogous to the methods for creating synthetic recombinants of poxviruses such as the vaccinia virus and avipox virus described in U.S. Patent Nos. 4,769,330, 4,772,848, 4,603,112, 5,100,587, and 5,179,993, the disclosures of which are incorporated herein by reference.

First, the DNA gene sequence to be inserted into the virus, particularly an open reading frame from a non-pox source, is placed into an E. coli plasmid construct into which DNA homologous to a section of DNA of the poxvirus has been inserted. Separately, the DNA gene sequence to be inserted is ligated to a promoter. The promoter-gene linkage is positioned in the plasmid construct so that the promoter-gene linkage is flanked on both ends by DNA homologous to a DNA sequence flanking a region of pox DNA containing a nonessential locus. The resulting plasmid construct is then amplified by growth within E. coli bacteria (Clewell, 1972) and isolated (Clewell et al., 1969; Maniatis et al., 1982).

Second, the isolated plasmid containing the DNA gene sequence to be inserted is transfected into a cell culture, e.g. chick embryo fibroblasts, along with the poxvirus. Recombination between homologous pox DNA in the plasmid and the viral genome respectively gives a poxvirus modified by the presence, in a nonessential region of its genome, of foreign DNA sequences. The term "foreign" DNA designates exogenous DNA, particularly DNA from a non-pox source, that codes for gene products not ordinarily produced by the genome into which the

exogenous DNA is placed.

Genetic recombination is in general the exchange of homologous sections of DNA between two strands of DNA. In certain viruses RNA may replace DNA. Homologous sections of nucleic acid are sections of nucleic acid (DNA or RNA) which have the same sequence of nucleotide bases.

Genetic recombination may take place naturally during the replication or manufacture of new viral genomes within the infected host cell. Thus, genetic recombination between viral genes may occur during the viral replication cycle that takes place in a host cell which is co-infected with two or more different viruses or other genetic constructs. A section of DNA from a first genome is used interchangeably in constructing the section of the genome of a second co-infecting virus in which the DNA is homologous with that of the first viral genome.

However, recombination can also take place between sections of DNA in different genomes that are not perfectly homologous. If one such section is from a first genome homologous with a section of another genome except for the presence within the first section of, for example, a genetic marker or a gene coding for an

antigenic determinant inserted into a portion of the homologous DNA, recombination can still take place and the products of that recombination are then detectable by the presence of that genetic marker or gene in the recombinant viral genome. Additional strategies have recently been reported for generating recombinant

vaccinia virus.

Successful expression of the inserted DNA genetic sequence by the modified infectious virus requires two conditions. First, the insertion must be into a

nonessential region of the virus in order that the modified virus remain viable. The second condition for expression of inserted DNA is the presence of a promoter in the proper relationship to the inserted DNA. The promoter must be placed so that it is located upstream from the DNA sequence to be expressed.

Vaccinia virus has been used successfully to

immunize against smallpox, culminating in the worldwide eradication of smallpox in 1980. In the course of its history, many strains of vaccinia have arisen. These different strains demonstrate varying immunogenicity and are implicated to varying degrees with potential

complications, the most serious of which are post- vaccinial encephalitis and generalized vaccinia

(Behbehani, 1983).

With the eradication of smallpox, a new role for vaccinia became important, that of a genetically

engineered vector for the expression of foreign genes. Genes encoding a vast number of heterologous antigens have been expressed in vaccinia, often resulting in protective immunity against challenge by the

corresponding pathogen (reviewed in Tartaglia et al., 1990a).

The genetic background of the vaccinia vector has been shown to affect the protective efficacy of the expressed foreign immunogen. For example, expression of Epstein Barr Virus (EBV) gp340 in the Wyeth vaccine strain of vaccinia virus did not protect cottontop tamarins against EBV virus induced lymphoma, while expression of the same gene in the WR laboratory strain of vaccinia virus was protective (Morgan et al., 1988).

A fine balance between the efficacy and the safety of a vaccinia virus-based recombinant vaccine candidate is extremely important. The recombinant virus roust present the immunogen(s) in a manner that elicits a protective immune response in the vaccinated animal but lacks any significant pathogenic properties. Therefore attenuation of the vector strain would be a highly desirable advance over the current state of technology.

A number of vaccinia genes have been identified which are non-essential for growth of the virus in tissue culture and whose deletion or inactivation reduces virulence in a variety of animal systems.

The gene encoding the vaccinia virus thymidine kinase (TK) has been mapped (Hruby et al., 1982) and sequenced (Hruby et al., 1983; Weir et al., 1983).

Inactivation or complete deletion of the thymidine kinase gene does not prevent growth of vaccinia virus in a wide variety of cells in tissue culture. TK- vaccinia virus is also capable of replication in vivo at the site of inoculation in a variety of hosts by a variety of routes.

It has been shown for herpes simplex virus type 2 that intravaginal inoculation of guinea pigs with TK- virus resulted in significantly lower virus titers in the spinal cord than did inoculation with TK⁺ virus

(Stanberry et al., 1985). It has been demonstrated that herpesvirus encoded TK activity in vitro was not

important for virus growth in actively metabolizing cells, but was required for virus growth in quiescent cells (Jamieson et al., 1974).

Attenuation of TK- vaccinia has been shown in mice inoculated by the intracerebral and intraperitoneal routes (Buller et al., 1985). Attenuation was observed both for the WR neurovirulent laboratory strain and for the Wyeth vaccine strain. In mice inoculated by the intradermal route, TK- recombinant vaccinia generated equivalent anti-vaccinia neutralizing antibodies as compared with the parental TK⁺ vaccinia virus, indicating that in this test system the loss of TK function does not significantly decrease immunogenicity of the vaccinia virus vector. Following intranasal inoculation of mice with TK- and TK⁺ recombinant vaccinia virus (WR strain), significantly less dissemination of virus to other locations, including the brain, has been found (Taylor et al., 1991a).

Another enzyme involved with nucleotide metabolism is ribonucleotide reductase. Loss of virally encoded ribonucleotide reductase activity in herpes simplex virus (HSV) by deletion of the gene encoding the large subunit was shown to have no effect on viral growth and DNA synthesis in dividing cells in vitro , but severely compromised the ability of the virus to grow on serum starved cells (Goldstein et al., 1988). Using a mouse model for acute HSV infection of the eye and

reactivatable latent infection in the trigeminal ganglia, reduced virulence was demonstrated for HSV deleted of the large subunit of ribonucleotide reductase, compared to the virulence exhibited by wild type HSV (Jacobson et al., 1989).

Both the small (Slabaugh et al., 1988) and large (Schmidtt et al., 1988) subunits of ribonucleotide reductase have been identified in vaccinia virus.

Insertional inactivation of the large subunit of

ribonucleotide reductase in the WR strain of vaccinia virus leads to attenuation of the virus as measured by intracranial inoculation of mice (Child et al., 1990).

The vaccinia virus hemagglutinin gene (HA) has been mapped and sequenced (Shida, 1986). The HA gene of vaccinia virus is nonessential for growth in tissue culture (Ichihashi et al., 1971). Inactivation of the HA gene of vaccinia virus results in reduced neurovirulence in rabbits inoculated by the intracranial route and smaller lesions in rabbits at the site of intradermal inoculation (Shida et al., 1988). The HA locus was used for the insertion of foreign genes in the WR strain

(Shida et al., 1987), derivatives of the Lister strain (Shida et al., 1988) and the Copenhagen strain (Guo et al., 1989) of vaccinia virus. Recombinant HA- vaccinia virus expressing foreign genes have been shown to be immunogenic (Guo et al., 1989; Itamura et al., 1990;

Shida et al., 1988; Shida et al., 1987) and protective against challenge by the relevant pathogen (Guo et al., 1989; Shida et al., 1987).

Cowpox virus (Brighton red strain) produces red (hemorrhagic) pocks on the chorioallantoic membrane of chicken eggs. Spontaneous deletions within the cowpox genome generate mutants which produce white pocks (Pickup et al., 1984). The hemorrhagic function (u) maps to a 38 kDa protein encoded by an early gene (Pickup et al., 1986). This gene, which has homology to serine protease inhibitors, has been shown to inhibit the host

inflammatory response to cowpox virus (Palumbo et al., 1989) and is an inhibitor of blood coagulation. The u gene is present in WR strain of vaccinia virus (Kotwal et al., 1989b). Mice inoculated with a WR vaccinia virus recombinant in which the u region has been inactivated by insertion of a foreign gene produce higher antibody levels to the foreign gene product compared to mice inoculated with a similar recombinant vaccinia virus in which the u gene is intact (Zhou et al., 1990). The u region is present in a defective nonfunctional form in Copenhagen strain of vaccinia virus (open reading frames B13 and B14 by the terminology reported in Goebel et al., 1990a,b).

Cowpox virus is localized in infected cells in cytoplasmic A type inclusion bodies (ATI) (Kato et al., 1959). The function of ATI is thought to be the

protection of cowpox virus virions during dissemination from animal to animal (Bergoin et al., 1971). The ATI region of the cowpox genome encodes a 160 kDa protein which forms the matrix of the ATI bodies (Funahashi et al., 1988; Patel et al., 1987). Vaccinia virus, though containing a homologous region in its genome, generally does not produce ATI. In WR strain of vaccinia, the ATI region of the genome is translated as a 94 kDa protein (Patel et al., 1988). In Copenhagen strain of vaccinia virus, most of the DNA sequences corresponding to the ATI region are deleted, with the remaining 3' end of the region fused with sequences upstream from the ATI region to form open reading frame (ORF) A26L (Goebel et al., 1990a, b).

A variety of spontaneous (Altenburger et al., 1989; Drillien et al., 1981; Lai et al., 1989; Moss et al., 1981; Paez et al., 1985; Panicali et al., 1981) and engineered (Perkus et al., 1991; Perkus et al., 1989;

Perkus et al., 1986) deletions have been reported near the left end of the vaccinia virus genome. A WR strain of vaccinia virus with a 10 kb spontaneous deletion (Moss et al., 1981; Panicali et al., 1981) was shown to be attenuated by intracranial inoculation in mice (Buller et al., 1985). This deletion was later shown to include 17 potential ORFs (Kotwal et al., 1988b). Specific genes within the deleted region include the virokine NIL and a 35 kDa protein (C3L, by the terminology reported in

Goebel et al., 1990a,b). Insertional inactivation of NIL reduces virulence by intracranial inoculation for both normal and nude mice (Kotwal et al., 1989a). The 35 kDa protein is secreted like NIL into the medium of vaccinia virus infected cells. The protein contains homology to the family of complement control proteins, particularly the complement 4B binding protein (C4bp) (Kotwal et al., 1988a). Like the cellular C4bp, the vaccinia 35 kDa protein binds the fourth component of complement and inhibits the classical complement cascade (Kotwal et al., 1990). Thus the vaccinia 35 kDa protein appears to be involved in aiding the virus in evading host defense mechanisms.

The left end of the vaccinia genome includes two genes which have been identified as host range genes, K1L (Gillard et al., 1986) and C7L (Perkus et al., 1990).

Deletion of both of these genes reduces the ability of vaccinia virus to grow on a variety of human cell lines (Perkus et al., 1990).

Two additional vaccine vector systems involve the use of naturally host-restricted poxviruses, avipox viruses. Both fowlpoxvirus (FPV) and canarypoxvirus (CPV) have been engineered to express foreign gene products. Fowlpox virus (FPV) is the prototypic virus of the Avipox genus of the Poxvirus family. The virus causes an economically important disease of poultry which has been well controlled since the 1920^,s by the use of live attenuated vaccines. Replication of the avipox viruses is limited to avian species (Matthews, 1982) and there are no reports in the literature of avipoxvirus causing a productive infection in any non-avian species including man. This host restriction provides an

inherent safety barrier to transmission of the virus to other species and makes use of avipoxvirus based vaccine vectors in veterinary and human applications an

attractive proposition.

FPV has been used advantageously as a vector

expressing antigens from poultry pathogens. The

hemagglutinin protein of a virulent avian influenza virus was expressed in an FPV recombinant (Taylor et al., 1988a). After inoculation of the recombinant into chickens and turkeys, an immune response was induced which was protective against either a homologous or a heterologous virulent influenza virus challenge (Taylor et al., 1988a). FPV recombinants expressing the surface glycoproteins of Newcastle Disease Virus have also been developed (Taylor et al., 1990; Edbauer et al., 1990).

Despite the host-restriction for replication of FPV and CPV to avian systems, recombinants derived from these viruses were found to express extrinsic proteins in cells of nonavian origin. Further, such recombinant viruses were shown to elicit immunological responses directed towards the foreign gene product and where appropriate were shown to afford protection from challenge against the corresponding pathogen (Tartaglia et al., 1993a,b; Taylor et al., 1992; 1991b; 1988b).

Human T-cell leukemia/lymphoma virus type I (HTLV-I) and human immunodeficiency virus (HIV), retroviruses which causes adult T-cell leukemia (ATL) and tropical spastic paraparesis/HTLV-I-associated myelopathy

(TSP/HAM), and acquired immunodeficiency syndrome (Gallo, 1987; Poiesz, 1980; Hinuma, 1981; Barre-Siniussi, 1983; Popovic, 1984; Gallo, 1986), respectively, are

transmitted by close contact (e.g., sexual intercourse, mother-to-child) and transfusion of blood or blood products. However, in contrast to HIV-1, evidence exists that HTLV-I is not transmitted efficiently by

contaminated cryopreserved faction VIII preparations, suggesting that HTLV-I transmission occurs mostly via infected cells rather. than from cell-free virus. This is also supported by earlier results showing that in vitro transmission of cell-free HTLV-I is far less efficient than by coculturing infected cells with target cells (De Rossi, 1985) and, by the relatively small variation in HTLV-I (Gallo, 1987; Gessain, 1992), suggesting provirus rather than virus transmission.

HTLV-I is genetically more complex than other animal oncornavirus and is the only human oncornavirus known in addition to HTLV-II (Kalyanaraman, 1982). The genetic complexity of HTLV-I more closely resembles that of HIV (Gallo, 1986). In fact, HTLVs and HIVs share regulatory proteins with similar function (tax/tat, rex/rev) and a number of auxiliary genes [vpf, vif, nef, vpu for HIV-1 (Haseltine, 1989), P12¹, p13¹¹, p30¹¹ and p21^rex (Kiyokawa, 1985; Koralnik, 1993) for HTLV-I], which may be involved in adaptation of these pathogens for infecting human T-cells. Both viruses infect CD4⁺ T-cells in vivo and in vitro (6, 13, 14), but the HTLVs also infect other T-cell subtypes.

Genetic and immunological variation (LaRosa, 1990; Rusche, 1988) is a concern in product development with respect to HIV (e.g., vaccine development), whereas in the case of HTLV-I, genetic variation is very low

(Gassain, 1992; Paine, 1991; Schulz, 1991; Komourian, 1991). However, the discovery of other genetically distinct HTLV-I types from the equatorial area of Zaire (Gessain, 1992) and Melanesia (Gessain, 1993; Sherman, 1992), in addition to the cosmopolitan HTLV-I and HTLV-II (9), have provided a spectrum of genetic variants

(variation ranges from 3 to 30% in the envelope gene) that can be used in challenge experiments of immunized rabbits. Preliminary experiments have shown that

although cross-neutralization among the African,

cosmopolitan and Melanesian HTLVs can be detected

(Benson, 1994), titers are low against heterologous viruses, indicating that if neutralizing antibodies are important in protection against natural HTLV infection, a vaccine should be composed of more than one genetic variant. An effective means to express HTLV-I products would be beneficial, for instance, as an immunological composition or vaccine composition, or as a means to prepare such compositions, or for preparing HTLV-I products or antibodies thereto for assays, kits or tests, especially considering areas of the world where HTLV-I is endemic, such as parts of Japan, the Caribbean, parts of Africa and South America. For instance, a highly

attenuated poxvirus HTLV-I_env alone or in combination with a subunit boost of the purified HTLV-I precursor envelope protein (gp63) would be useful as an immunological or vaccine composition or to prepare antigens or antibodies for assays, kits or tests.

Rabbits are very sensitive to HTLV-I infection but do not develop diseases resembling human ATL or TSP/HAM (Miyoshi, 1985). However, HTLV-I infection of rabbits represents an economical and efficient animal model for vaccine studies.

It can thus be appreciated that provision of an HTLV recombinant poxvirus, and of compositions and products therefrom particularly NYVAC or ALVAC based HTLV

recombinants and compositions and products therefrom, especially such recombinants containing coding for any or all of HTLV_env, and compositions and products therefrom would be a highly desirable advance over the current state of technology.

OBJECTS AND SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide modified recombinant viruses, which viruses have enhanced safety, and to provide a method of making such recombinant viruses.

It is an additional object of this invention to provide a recombinant poxvirus antigenic, vaccine or immunological composition having an increased level of safety compared to known recombinant poxvirus vaccines. It is a further object of this invention to provide a modified vector for expressing a gene product in a host, wherein the vector is modified so that it has attenuated virulence in the host.

It is another object of this invention to provide a method for expressing a gene product in a cell cultured in vitro using a modified recombinant virus or modified vector having an increased level of safety.

These and other objects and advantages of the present invention will become more readily apparent after consideration of the following.

In one aspect, the present invention relates to a modified recombinant virus having inactivated virus-encoded genetic functions so that the recombinant virus has attenuated virulence and enhanced safety. The functions can be non-essential, or associated with virulence. The virus is advantageously a poxvirus, particularly a vaccinia virus or an avipox virus, such as fowlpox virus and canarypox virus. The modified

recombinant virus can include, within a non-essential region of the virus genome, a heterologous DNA sequence which encodes an antigen or epitope derived from HTLV such as HTLV_env.

In another aspect, the present invention relates to an antigenic, immunological or vaccine composition or a therapeutic composition for inducing an antigenic or immunological response in a host animal inoculated with the composition, said vaccine including a carrier and a modified recombinant virus having inactivated

nonessential virus-encoded genetic functions so that the recombinant virus has attenuated virulence and enhanced safety. The virus used in the composition according to the present invention is advantageously a poxvirus, particularly a vaccinia virus or an avipox virus, such as fowlpox virus and canarypox virus. The modified

recombinant virus can include, within a non-essential region of the virus genome, a heterologous DNA sequence which encodes an antigenic protein, e.g., derived from HTLV, such as HTLV_env.

In yet another aspect, the present invention relates to an immunogenic composition containing a modified recombinant virus having inactivated nonessential virus-encoded genetic functions so that the recombinant virus has attenuated virulence and enhanced safety. The modified recombinant virus includes, within a non-essential region of the virus genome, a heterologous DNA sequence which encodes an antigenic protein (e.g., derived from HTLV, such as HTLV_env) wherein the

composition, when administered to a host, is capable of inducing an immunological response specific to the antigen.

In a further aspect, the present invention relates to a method for expressing a gene product in a cell in vitro by introducing into the cell a modified recombinant virus having attenuated virulence and enhanced safety. The modified recombinant virus can include, within a nonessential region of the virus genome, a heterologous DNA sequence which encodes an antigenic protein, e.g.

derived from HTLV such as HTLV_env. The cells can then be reinfused directly into the individual or used to amplify specific reactivities for reinfusion (Ex vivo therapy).

In a further aspect, the present invention relates to a method for expressing a gene product in a cell cultured in vitro by introducing into the cell a modified recombinant virus having attenuated virulence and

enhanced safety. The modified recombinant virus can include, within a non-essential region of the virus genome, a heterologous DNA sequence which encodes an antigenic protein, e.g., derived from HTLV such as

HTLV_env. The product can then be administered to

individuals or animals to stimulate an immune response. The antibodies raised can be useful in individuals for the prevention or treatment of HTLV and, the antibodies from individuals or animals or the isolated in vitro expression products can be used in diagnostic kits, assays or tests to determine the presence or absence in a sample such as sera of HTLV or antigens therefrom or antibodies thereto (and therefore the absence or presence of the virus or of the products, or of an immune response to the virus or antigens).

In a still further aspect, the present invention relates to a modified recombinant virus having

nonessential virus-encoded genetic functions inactivated therein so that the virus has attenuated virulence, and wherein the modified recombinant virus further contains DNA from a heterologous source in a nonessential region of the virus genome. The DNA can code for HTLV such as HTLV_env. In particular, the genetic functions are

inactivated by deleting an open reading frame encoding a virulence factor or by utilizing naturally host

restricted viruses. The virus used according to the present invention is advantageously a poxvirus,

particularly a vaccinia virus or an avipox virus, such as fowlpox virus and canarypox virus. Advantageously, the open reading frame is selected from the group consisting of J2R, B13R + B14R, A26L, A56R, C7L - K1L, and I4L (by the terminology reported in Goebel et al., 1990a,b); and, the combination thereof. In this respect, the open reading frame comprises a thymidine kinase gene, a hemorrhagic region, an A type inclusion body region, a hemagglutinin gene, a host range gene region or a large subunit, ribonucleotide reductase; or, the combination thereof. A suitable modified Copenhagen strain of vaccinia virus is identified as NYVAC (Tartaglia et al., 1992), or a vaccinia virus from which has been deleted J2R, B13R+B14R, A26L, A56R, C7L-K11 and I4L or a

thymidine kinase gene, a hemorrhagic region, an A type inclusion body region, a hemagglutinin gene, a host range region, and a large subunit, ribonucleotide reductase (See also U.S. Patent No. 5,364,773). Alternatively, a suitable poxvirus is an ALVAC or, a canarypox virus (Rentschler vaccine strain) which was attenuated, for instance, through more than 200 serial passages on chick embryo fibroblasts, a master seed therefrom was subjected to four successive plaque purifications under agar from which a plaque clone was amplified through five

additional passages.

The invention in yet a further aspect relates to the product of expression of the inventive recombinant poxvirus and uses therefor, such as to form antigenic, immunological or vaccine compositions for treatment, prevention, diagnosis or testing.

These and other embodiments are disclosed or are obvious from and encompassed by the follow detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description, given by way of example, but not intended to limit the invention solely to the specific embodiments described, may best be understood in conjunction with the accompanying drawings, in which:

FIG. 1 schematically shows a method for the

construction of plasmid pSD460 for deletion of thymidine kinase gene and generation of recombinant vaccinia virus vP410;

FIG. 2 schematically shows a method for the

construction of plasmid pSD486 for deletion of

hemorrhagic region and generation of recombinant vaccinia virus vP553;

FIG. 3 schematically shows a method for the

construction of plasmid pMP494Δ for deletion of ATI region and generation of recombinant vaccinia virus vP618;

FIG. 4 schematically shows a method for the

construction of plasmid pSD467 for deletion of

hemagglutinin gene and generation of recombinant vaccinia virus vP723; FIG. 5 schematically shows a method for the

construction of plasmid pMPCK1Δ for deletion of gene cluster [C7L - K1L] and generation of recombinant

vaccinia virus vP804;

FIG. 6 schematically shows a method for the

construction of plasmid pSD548 for deletion of large subunit, ribonucleotide reductase and generation of recombinant vaccinia virus vP866 (NYVAC);

FIG. 7 schematically shows a method for the

construction of plasmid pRW842 for insertion of rabies glycoprotein G gene into the TK deletion locus and generation of recombinant vaccinia virus vP879;

FIG. 8 shows the DNA sequence (SEQ ID NO: 27) of a canarypox PvuII fragment containing the C5 ORF.

FIGS. 9A and 9B schematically show a method for the construction of recombinant canarypox virus vCP65 (ALVAC-RG);

FIG. 10 shows schematically the ORFs deleted to generate NYVAC;

FIGS. 11A to 11D show graphs of rabies neutralizing antibody titers (RFFIT, IU/ml), booster effect of HDC and vCP65 (10^5,5 TCID₅₀) in volunteers previously immunized with either the same or the alternate vaccine (vaccines given at days 0, 28 and 180, antibody titers measured at days 0, 7, 28, 35, 56, 173, 187 and 208); and

FIGS. 12 and 13 show serological analyses of animals inoculated With ALVAC, R-ALVAC (ALVAC-HTLV; vCP203), NYVAC, R-NYVAC (NYVAC-HTLV; vP1181) and challenged with HTLV-infected cells or blood.

DETAILED DESCRIPTION OF THE INVENTION

To develop a new vaccinia vaccine strain, NYVAC (vP866), the Copenhagen vaccine strain of vaccinia virus was modified by the deletion of six nonessential regions of the genome encoding known or potential virulence factors. The sequuntial deletions are detailed below (See U.S. Patent No. 5,364,773). All designations of vaccinia restriction fragments, open reading frames and nucleotide positions are based on the terminology

reported in Goebel et al., 1990a, b.

The deletion loci were also engineered as recipient loci for the insertion of foreign genes.

The regions deleted in NYVAC are listed below. Also listed are the abbreviations and open reading frame designations for the deleted regions (Goebel et al., 1990a,b) and the designation of the vaccinia recombinant (vP) containing all deletions through the deletion specified:

(1) thymidine kinase gene (TK; J2R) vP410;

(2) hemorrhagic region (u; B13R + B14R) vP553;

(3) A type inclusion body region (ATI; A26L) vP618;

(4) hemagglutinin gene (HA; A56R) vP723;

(5) host range gene region (C7L - K1L) vP804; and (6) large subunit, ribonucleotide reductase (I4L) vP866 (NYVAC).

NYVAC is a genetically engineered vaccinia virus strain that was generated by the specific deletion of eighteen open reading frames encoding gene products associated with virulence and host range. NYVAC is highly attenuated by a number of criteria including i) decreased virulence after intracerebral inoculation in newborn mice, ii) inocuity in genetically (nu⁺/nu⁺) or chemically (cyclophosphamide) immunocompromised mice, iii) failure to cause disseminated infection in

immunocompromised mice, iv) lack of significant

induration and ulceration on rabbit skin, v) rapid clearance from the site of inoculation, and vi) greatly reduced replication competency on a number of tissue culture cell lines including those of human origin.

Nevertheless, NYVAC based vectors induce excellent responses to extrinsic immunogens and provided protective immunity.

TROVAC refers to an attenuated fowlpox that was a plaque-cloned isolate derived from the FP-1 vaccine strain of fowlpoxvirus which is licensed for vaccination of 1 day old chicks. ALVAC is an attenuated canarypox virus-based vector that was a plaque-cloned derivative of the licensed canarypox vaccine, Kanapox (Tartaglia et al., 1992). ALVAC has some general properties which are the same as some general properties of Kanapox. ALVAC-based recombinant viruses expressing extrinsic immunogens have also been demonstrated efficacious as vaccine vectors (Tartaglia et al., 1993 a,b). This avipox vector is restricted to avian species for productive

replication. On human cell cultures, canarypox virus replication is aborted early in the viral replication cycle prior to viral DNA synthesis. Nevertheless, when engineered to express extrinsic immunogens, authentic expression and processing is observed in vitro in

mammalian cells and inoculation into numerous mammalian species induces antibody and cellular immune responses to the extrinsic immunogen and provides protection against challenge with the cognate pathogen (Taylor et al., 1992; Taylor et al., 1991). Recent Phase I clinical trials in both Europe and the United States of a canarypox/rabies glycoprotein recombinant (ALVAC-RG) demonstrated that the experimental vaccine was well tolerated and induced protective levels of rabiesvirus neutralizing antibody titers (Cadoz et al., 1992; Fries et al., 1992).

Additionally, peripheral blood mononuclear cells (PBMCs) derived from the ALVAC-RG vaccinates demonstrated

significant levels of lymphocyte proliferation when stimulated with purified rabies virus (Fries et al., 1992).

NYVAC, ALVAC and TROVAC have also been recognized as unique among all poxviruses in that the National

Institutes of Health ("NIH") (U.S. Public Health Service), Recombinant DNA Advisory Committee, which issues

guidelines for the physical containment of genetic material such as viruses and vectors, i.e., guidelines for safety procedures for the use of such viruses and vectors which are based upon the pathogenicity of the particular virus or vector, granted a reduction in physical containment level: from BSL2 to BSL1. No other poxvirus has a BSL1 physical containment level. Even the Copenhagen strain of vaccinia virus - the common smallpox vaccine - has a higher physical containment level;

namely, BSL2. Accordingly, the art has recognized that NYVAC, ALVAC and TROVAC have a lower pathogenicity than any other poxvirus.

The entire envelope protein of the human T-cell leukemia/lymphoma virus type I (HTLV-I)₁₇₁₁, obtained from the DNA of a West African healthy HTLV-I-infected

patient, was expressed in the highly attenuated poxvirus vaccine vectors ALVAC and NYVAC. Generation and

expression of NYVAC- and ALVAC-based HTLV-I_env recombinant viruses: HTLV-I_env sequences were derived from plasmid p17-11 which contains the SstI-SstI 8.5 kb HTLV-I genomic DNA. The poxvirus/HTLV-I_env expression cassette was constructed by fusing the env sequences in a precise ATG for ATG configuration with the vaccinia virus

early/immediate I3L promoter. Insertion plasmid pMAW018 was generated by inserting the I3L/HTLV-I_env expression cassette into the generic insertion plasmid pSPHA6.

Plasmid pMAW018 was used in in vitro recombination assays with NYVAC (vP866) as the rescuing virus to yield NYVAC HTLV-I_env (vP1181). Recombination with this plasmid inserted the I3L/HTLV-I_env expression cassette into the NYVAC HA locus. Insertion plasmid pMAW107 was generated by inserting the I3L/HTLV-I_env expression cassette into the generic insertion plasmid pVQC5LSP6. Plasmid pMAW017 was used in standard in vitro recombination assays with ALVAC (vCPpp) as rescue virus to yield ALVAC HTLV-I_env (vCP203). This insertion placed the I3L/HTLV-I_env

expression cassette into the ALVAC C5 locus.

These recombinants were used to immunize New Zealand white rabbits. Immunization regimens included

inoculation of the poxvirus recombinant alone as well as prime-boost protocols using gp63 HTLV-I envelope precursor protein in Alum as the subunit boost. Of course, gp63 HTLV envelope precursor can also be

administered with or after the inventive recombinants. All animals were exposed to a HTLV-I cell-associated challenge (5 × 10⁴ cells) from a primary culture of the HTLV-I_BOU isolate. The results indicated that two inoculations of 10⁷ pfu of the ALVAC-based HTLV-I_env vaccine candidate protected animals against viral

challenge 5 months following the last immunization.

However, a combination protocol with ALVAC-env and two additional boosts of gp63 surprisingly failed to confer protection suggesting that administration of the subunit preparation might be deleterious. More importantly, even a periodic vaccination immunization or administration regimen, e.g., triannual or biannual, of the inventive recombinants or of compositions containing such

recombinants or expression products thereof for either animals such as rabbits or humans, is comprehended by the 5 month protection; for instance, even to assist in preventing animal populations such as domesticated animal populations, e.g., rabbit populations, from being HTLV infected or carriers, (the possibility of HTLV infected or carrier animals from the susceptibility of rabbits to HTLV and the possibility of close contact between man and animals or among animals.

Further, in the case of the NYVAC HTLV-I_env

recombinant, protection was afforded as early as 2 months following the first immunization. The protected animals in the NYVAC and A1VAC trials were rechallenged 5 months following the initial challenge exposure with 5 ml of blood from an HTLV-I_BOU-infected animal, and subsequently become infected. However, the expression by and

protection conferred by the recombinants demonstrates their utility and the utility of their expression

products in compositions and methods.

Clearly based on the attenuation profiles of the NYVAC, ALVAC, and TROVAC vectors and their demonstrated ability to elicit both humoral and cellular immunological responses to extrinsic immunogens (Tartaglia et al., 1993a,b; Taylor et al., 1992; Konishi et al., 1992) such recombinant viruses offer a distinct advantage over previously described vaccinia-based recombinant viruses.

The administration procedure for recombinant virus or expression product thereof, compositions of the invention such as immunological, antigenic or vaccine compositions or therapeutic compositions can be via a parenteral route (intradermal, intramuscular or

subcutaneous). Such an administration enables a systemic immune response.

More generally, the inventive antigenic,

immunological or vaccine compositions or therapeutic compositions (compositions containing the poxvirus recombinants of the invention) can be prepared in

accordance with standard techniques well known to those skilled in the pharmaceutical art. Such compositions can be administered in dosages and by techniques well known to those skilled in the medical arts taking into

consideration such factors as the age, sex, weight, and condition of the particular patient, and the route of administration. The compositions can be administered alone, or can be co-administered or sequentially

administered with compositions of the invention or with other immunological, antigenic or vaccine or therapeutic compositions in seropositive individuals. The

compositions can be administered alone, or can be co-administered or sequentially administered with

compositions of the invention or with other antigenic, immunological, vaccine or therapeutic compositions in seronegative individuals. Such other compositions can include purified antigens from HTLV or from the

expression of such antigens by a recombinant poxvirus or other vector system or, such other compositions can include a recombinant poxvirus which expresses other HTLV antigens or biological response modifiers again taking into consideration such factors as the age, sex, weight, and condition of the particular patient, and, the route of administration.

Examples of compositions of the invention include liquid preparations for orifice, e.g., oral, nasal, anal, vaginal, etc., administration such as suspensions, syrups or elixirs; and, preparations for parenteral,

subcutaneous, intradermal, intramuscular or intravenous administration (e.g., injectable administration) such as sterile suspensions or emulsions. In such compositions the recombinant poxvirus may be in admixture with a suitable carrier, diluent, or excipient such as sterile water, physiological saline, glucose or the like.

Further, the products of expression of the inventive recombinant poxviruses can be used directly to stimulate an immune response in either seronegative or seropositive individuals or in animals. Thus, the expression products can be used in compositions of the invention instead or in addition to the inventive recombinant poxvirus in the aforementioned compositions.

Additionally, the inventive recombinant poxvirus and the expression products therefrom stimulate an immune or antibody response in humans and animals and therefore those products are antigens. From those antibodies or antigens, by techniques well-known in the art, monoclonal antibodies can be prepared and, those monoclonal

antibodies or the antigens, can be employed in well known antibody binding assays, diagnostic kits or tests to determine the presence or absence of particular HTLV antigen(s) and therefore the presence or absence of the virus or expression of the antigen(s) (in HTLV or other systems), or to determine whether an immune response to the virus or antigen(s) has simply been stimulated.

Those monoclonal antibodies or the antigens can also be employed in immunoadsorption chromatography to recover or isolate HTLV or expression products of the inventive recombinant poxvirus. More in particular, the inventive recombinants and compositions have numerous utilities, including:

(i) inducing an immunological response in

seronegative individuals (use as or as part of a vaccine regimen);

(ii) therapy in seropositive individuals; and (iii) a means for generating HTLV protein in

vitro without the risk of virus infection. The products of expression of the inventive

recombinant poxvirus can be used directly to stimulate an immune response in either seronegative or seropositive individuals or in animals. Thus, the expression products can be used in compositions of the invention instead of or in addition to the inventive recombinant poxvirus.

Additionally, the inventive recombinant poxvirus and the expression products therefrom stimulate an immune or antibody response in humans and animals. From those antibodies, by techniques well-known in the art,

monoclonal antibodies can be prepared and, those

monoclonal antibodies or the expression products of the inventive poxvirus and composition can be employed in well known antibody binding assays, diagnostic kits or tests to determine the presence or absence of particular HTLV antigen(s) or antibody(ies) and therefore the presence or absence of the virus, or to determine whether an immune response to the virus or antigen(s) has simply been stimulated. Those monoclonal antibodies can also be employed in immunoadsorption chromatography to recover, isolate or detect HTLV or expression products of the inventive recombinant poxvirus. Methods for producing monoclonal antibodies and for uses of monoclonal

antibodies, and, of uses and methods for HTLV antigens - the expression products of the inventive poxvirus and composition - are well known to those of ordinary skill in the art. They can be used in diagnostic methods, kits, tests or assays, as well as to recover materials by immunoadsorption chromatography or by

immunoprecipitation.

Monoclonal antibodies are immunoglobulins produced by hybridoma cells. A monoclonal antibody reacts with a single antigenic determinant and provides greater

specificity than a conventional, serum-derived antibody. Furthermore, screening a large number of monoclonal antibodies makes it possible to select an individual antibody with desired specificity, avidity and isotype. Hybridoma cell lines provide a constant, inexpensive source of chemically identical antibodies and

preparations of such antibodies can be easily

standardized. Methods for producing monoclonal

antibodies are well known to those of ordinary skill in the art, e.g., Koprowski, H. et al., U.S. Patent No.

4,196,265, issued April 1, 1989, incorporated herein by reference.

Uses of monoclonal antibodies are known. One such use is in diagnostic methods, e.g., David, G. and Greene, H. U.S. Patent No. 4,376,110, issued March 8, 1983;

incorporated herein by reference. Monoclonal antibodies have also been used to recover materials by

immunoadsorption chromatography, e.g., Milstein, C. 1980, Scientific American 243:66, 70, incorporated herein by reference.

Furthermore, the inventive recombinant poxvirus or expression products therefrom can be used to stimulate a response in cells in vitro or ex vivo for subsequent reinfusion into a patient. If the patient is

seronegative, the reinfusion is to stimulate an immune response, e.g., an immunological or antigenic response such as active immunization. In a seropositive

individual, the reinfusion is to stimulate or boost the immune system against HTLV.

Accordingly, the inventive recombinant poxvirus has several utilities: In antigenic, immunological or vaccine compositions such as for administration to seronegative individuals. In therapeutic compositions in seropositive individuals in need of therapy to stimulate or boost the immune system against HTLV. In vitro to produce antigens which can be further used in antigenic, immunological or vaccine compositions or in therapeutic compositions. To generate antibodies (either by direct administration or by administration of an expression product of the inventive recombinant poxvirus) or

expression products or antigens which can be further used: in diagnosis, tests or kits to ascertain the presence or absence of antigens in a sample such as sera, for instance, to ascertain the presence or absence of HTLV in a sample such as sera or, to determine whether an immune response has elicited to the virus or, to

particular antigen (s) ; or , in immunoadsorption

chromatography, immunoprecipitation and the like. With respect to the use of recombinant antigens in assays, kits or tests, reference is made to European Patent

Application No. 89 202 922.4, filed November 20, 1989, entitled, "Skin Test and Test Kit For Aids," NTIS

publication No. P890-238429 entitled, "Cloning and

Expression of HTLV-III DNA," published in about November, 1990 (Chang, USSN 06/693,866, filed January 23, 1985), each of which is incorporated herein by reference, and, as to assays employing antigens, reference is made to Essex, et al., U.S. Patent No. 4,725,669, incorporated herein by reference.

Other utilities also exist for embodiments of the invention.

A better understanding of the present invention and of its many advantages will be had from the following examples, given by way of illustration.

EXAMPLES DNA Cloning and Synthesis. Plasmids were

constructed, screened and grown by standard procedures (Maniatis et al., 1982; Perkus et al., 1985; Piccini et al., 1987). Restriction endonucleases were obtained from Bethesda Research Laboratories, Gaithersburg, MD, New England Biolabs, Beverly, MA; and Boehringer Mannheim Biochemicals, Indianapolis, IN. Klenow fragment of E. coli polymerase was obtained from Boehringer Mannheim Biochemicals. BAL-31 exonuclease and phage T4 DNA ligase were obtained from New England Biolabs. The reagents were used as specified by the various suppliers.

Synthetic oligodeoxyribonucleotides were prepared on a Biosearch 8750 or Applied Biosystems 380B DNA

synthesizer as previously described (Perkus et al.,

1989). DNA sequencing was performed by the dideoxy-chain termination method (Sanger et al., 1977) using Sequenase (Tabor et al., 1987) as previously described (Guo et al., 1989). DNA amplification by polymerase chain reaction (PCR) for sequence verification (Engelke et al., 1988) was performed using custom synthesized oligonucleotide primers and GeneAmp DNA amplification Reagent Kit (Perkin Elmer Cetus, Norwalk, CT) in an automated Perkin Elmer Cetus DNA Thermal Cycler. Excess DNA sequences were deleted from plasmids by restriction endonuclease

digestion followed by limited digestion by BAL-31

exonuclease and mutagenesis (Mandecki, 1986) using synthetic oligonucleotides.

Cells, Virus, and Transfection. The origins and conditions of cultivation of the Copenhagen strain of vaccinia virus has been previously described (Guo et al., 1989). Generation of recombinant virus by recombination, in situ hybridization of nitrocellulose filters and screening for B-galactosidase activity are as previously described (Piccini et al., 1987).

The origins and conditions of cultivation of the Copenhagen strain of vaccinia virus and NYVAC has been previously described (Guo et al., 1989; Tartaglia et al., 1992). Generation of recombinant virus by recombination, in situ hybridization of nitrocellulose filters and screening for B-galactosidase activity are as previously described (Panicali et al., 1982; Perkus et al., 1989). The parental canarypox virus (Rentschler strain) is a vaccinal strain for canaries. The vaccine strain was obtained from a wild type isolate and attenuated through more than 200 serial passages on chick embryo

fibroblasts. A master viral seed was subjected to four successive plague purifications under agar and one plaque clone was amplified through five additional passages after which the stock virus was used as the parental virus in in vitro recombination tests. The plaque purified canarypox isolate is designated ALVAC.

The strain of fowlpox virus (FPV) designated FP-1 has been described previously (Taylor et al., 1988a). It is an attenuated vaccine strain useful in vaccination of day old chickens. The parental virus strain Duvette was obtained in France as a fowlpox scab from a chicken. The virus was attenuated by approximately 50 serial passages in chicken embryonated eggs followed by 25 passages on chicken embryo fibroblast cells. The virus was subjected to four successive plaque purifications. One plaque isolate was further amplified in primary CEF cells and a stock virus, designated as TROVAC, established.

NYVAC, ALVAC and TROVAC viral vectors and their derivatives were propagated as described previously

(Piccini et al., 1987; Taylor et al., 1988a,b). Vero cells and chick embryo fibroblasts (CEF) were propagated as described previously (Taylor et al., 1988a, b).

As to NYVAC and especially Examples 1 to 6,

reference's made to U.S. Patent No. 5,364,773,

incorporated herein by reference. EXAMPLE 1 - CONSTRUCTION OF PLASMID pSD460 FOR

DELETION OF THYMIDINE KINASE GENE (J2R)

Referring now to FIG. 1, plasmid pSD406 contains vaccinia HindIII J (pos. 83359 - 88377) cloned into pUC8. pSD406 was cut with HindIII and PvuII, and the 1.7 kb fragment from the left side of HindIII J cloned into pUC8 cut with HindIII/SmaI, forming pSD447. pSD447 contains the entire gene for J2R (pos. 83855 - 84385). The initiation codon is contained within an NlaIII site and the termination codon is contained within an SspI site. Direction of transcription is indicated by an arrow in FIG. 1.

To obtain a left flanking arm, a 0.8 kb

HindIII/EcoRI fragment was isolated from pSD447, then digested with NlaIII and a 0.5 kb HindIII/NlaIII fragment isolated. Annealed synthetic oligonucleotides

were ligated with the 0.5 kb HindIII/NlaIII fragment into pUC18 vector plasmid cut with HindIII/EcoRI, generating plasmid pSD449.

To obtain a restriction fragment containing a vaccinia right flanking arm and pUC vector sequences, pSD447 was cut with SspI (partial) within vaccinia sequences and HindIII at the pUC/vaccinia junction, and a

2.9 kb vector fragment isolated. This vector fragment was ligated with annealed synthetic oligonucleotides

generating pSD459. To combine the left and right flanking arms into one plasmid, a 0.5 kb HindIII/Smal fragment was isolated from pSD449 and ligated with pSD459 vector plasmid cut with HindIII/Smal. generating plasmid pSD460. pSD460 was used as donor plasmid for recombination with wild type

parental vaccinia virus Copenhagen strain VC-2. ³²P labelled probe was synthesized by primer extension using

MPSYN45 (SEQ ID NO:3) as template and the complementary

20mer oligonucleotide MPSYN47 (SEQ ID NO: 5)

(5' TTAGTTAATTAGGCGGCCGC 3') as primer. Recombinant virus vP410 was identified by plaque hybridization.

EXAMPLE 2 - CONSTRUCTION OF PLASMID pSD486 FOR DELETION

OF HEMORRHAGIC REGION (B13R + B14R)

Referring now to FIG. 2, plasmid pSD419 contains vaccinia SalI G (pos. 160,744-173,351) cloned into pUC8. pSD422 contains the contiguous vaccinia SalI fragment to the right, SalI J (pos. 173,351-182,746) cloned into pUC8. To construct a plasmid deleted for the hemorrhagic region, U, B13R - B14R (pos. 172,549 - 173,552), pSD419 was used as the source for the left flanking arm and pSD422 was used as the source of the right flanking arm. The direction of transcription for the u region is indicated by an arrow in FIG. 2.

To remove unwanted sequences from pSD419, sequences to the left of the NcoI site (pos. 172,253) were removed by digestion of pSD419 with NcoI/SmaI followed by blunt ending with Klenow fragment of E . coli polymerase and ligation generating plasmid pSD476. A vaccinia right flanking arm was obtained by digestion of pSD422 with

HpaI at the termination codon of B14R and by digestion with Nrul 0.3 kb to the right. This 0.3 kb fragment was isolated and ligated with a 3.4 kb HincII vector fragment isolated from pSD476, generating plasmid pSD477. The location of the partial deletion of the vaccinia u region in pSD477 is indicated by a triangle. The remaining B13R coding sequences in pSD477 were removed by digestion with ClaI/HpaI, and the resulting vector fragment was ligated with annealed synthetic oligonucleotides SD22mer/SD20mer

(SEQ ID NO:6/SEQ ID NO: 7)

generating pSD479. pSD479 contains an initiation codon (underlined) followed by a BamHI site. To place E . coli Beta-galactosidase in the B13-B14 (u) deletion locus under the control of the u promoter, a 3.2 kb BamHI fragment containing the Beta-galactosidase gene (Shapira et al., 1983) was inserted into the BamHI site of pSD479, generating pSD479BG. pSD479BG was used as donor plasmid for recombination with vaccinia virus vP410. Recombinant vaccinia virus vP533 was isolated as a blue plaque in the presence of chromogenic substrate X-gal. In vP533 the B13R-B14R region is deleted and is replaced by Beta- galactosidase.

To remove Beta-galactosidase sequences from vP533, plasmid pSD486, a derivative of pSD477 containing a polylinker region but no initiation codon at the u deletion junction, was utilized. First the ClaI/HpaI vector fragment from pSD477 referred to above was ligated with annealed synthetic oligonucleotides SD42mer/SD40mer (SEQ ID NO:8/SEQ ID NO:9)

generating plasmid pSD478. Next the EcoRI site at the pUC/vaccinia junction was destroyed by digestion of pSD478 with EcoRI followed by blunt ending with Klenow fragment of E. coli polymerase and ligation, generating plasmid pSD478E". pSD478E" was digested with BamHI and

HpaI and ligated with annealed synthetic oligonucleotides generating plasmid pSD486. pSD486 was used as donor plasmid for recombination with recombinant vaccinia virus vP533, generating vP553, which was isolated as a clear plaque in the presence of X-gal.

EXAMPLE 3 - CONSTRUCTION OF PLASMID pMP494Δ

FOR DELETION OF ATI REGION (A26L)

Referring now to FIG. 3, pSD414 contains SalI B cloned into pUC8. To remove unwanted DNA sequences to the left of the A26L region, pSD414 was cut with XbaI within vaccinia sequences (pos. 137,079) and with HindIII at the pUC/vaccinia junction, then blunt ended with

Klenow fragment of E. coli polymerase and ligated, resulting in plasmid pSD483. To remove unwanted vaccinia DNA sequences to the right of the A26L region, pSD483 was cut with EcoRI (pos. 140,665 and at the pUC/vaccinia junction) and ligated, forming plasmid pSD484. To remove the A26L coding region, pSD484 was cut with NdeI

(partial) slightly upstream from the A26L ORF (pos.

139,004) and with HpaI (pos. 137,889) slightly downstream from the A26L ORF. The 5.2 kb vector fragment was isolated and ligated with annealed synthetic

oligonucleotides ATI3/ATI4 (SEQ ID NO:12/SEQ ID NO: 13)

reconstructing the region upstream from A26L and

replacing the A26L ORF with a short polylinker region containing the restriction sites BglII, EcoRI and HpaI, as indicated above. The resulting plasmid was designated pSD485. Since the BglII and EcoRI sites in the

polylinker region of pSD485 are not unique, unwanted

BglII and EcoRI sites were removed from plasmid pSD483 (described above) by digestion with BglII (pos. 140,136) and with EcoRI at the pUC/vaccinia junction, followed by blunt ending with Klenow fragment of E. coli polymerase and ligation. The resulting plasmid was designated pSD489. The 1.8 kb ClaI (pos. 137, 198)/EcoRV (pos.

139,048) fragment from pSD489 containing the A26L ORF was replaced with the corresponding 0.7 kb polylinker-containing ClaI/EcoRV fragment from pSD485, generating pSD492. The BglII and EcoRI sites in the polylinker region of pSD492 are unique.

A 3.3 kb BglII cassette containing the E . coli Beta-galactosidase gene (Shapira et al., 1983) under the control of the vaccinia 11 kDa promoter (Bertholet et al., 1985; Perkus et al., 1990) was inserted into the

BglII site of pSD492, forming pSD493KBG. Plasmid

pSD493KBG was used in recombination with rescuing virus vP553. Recombinant vaccinia virus, vP581, containing Beta-galactosidase in the A26L deletion region, was isolated as a blue plaque in the presence of X-gal.

To generate a plasmid for the removal of Beta-galactosidase sequences from vaccinia recombinant virus vP581, the polylinker region of plasmid pSD492 was deleted by mutagenesis (Mandecki, 1986) using synthetic oligonucleotide MPSYN177 (SEQ ID NO: 14)

(5' AAAATGGGCGTGGATTGTTAACTTTATATAACTTATTTTTTGAATATAC 3 ' ) . In the resulting plasmid, pMP494Δ, vaccinia DNA encompassing positions [137,889 - 138,937], including the entire A26L ORF is deleted. Recombination between the pMP494Δ and the Beta-galactosidase containing vaccinia recombinant, vP581, resulted in vaccinia deletion mutant vP618, which was isolated as a clear plaque in the presence of X-gal.

EXAMPLE 4 - CONSTRUCTION OF PLASMID pSD467 FOR

DELETION OF HEMAGGLUTININ GENE (A56R)

Referring now to FIG. 4, vaccinia SalI G restriction fragment (pos. 160,744-173,351) crosses the HindIII A/B junction (pos. 162,539). pSD419 contains vaccinia SalI G cloned into pUC8. The direction of transcription for the hemagglutinin (HA) gene is indicated by an arrow in FIG. 4. Vaccinia sequences derived from HindIII B were removed by digestion of pSD419 with HindIII within vaccinia sequences and at the pUC/vaccinia junction followed by ligation. The resulting plasmid, pSD456, contains the HA gene, A56R, flanked by 0.4 kb of vaccinia sequences to the left and 0.4 kb of vaccinia sequences to the right. A56R coding sequences were removed by cutting pSD456 with RsaI (partial; pos. 161,090) upstream from

A56R coding sequences, and with EagI (pos. 162,054) near the end of the gene. The 3.6 kb RsaI/EagI vector

fragment from pSD456 was isolated and ligated with annealed synthetic oligonucleotides MPSYN59 (SEQ ID

NO:15), MPSYN62 (SEQ ID NO:16), MPSYN60 (SEQ ID NO:17), and MPSYN61 (SEQ ID NO: 18)

reconstructing the DNA sequences upstream from the A56R ORF and replacing the A56R ORF with a polylinker region as indicated above. The resulting plasmid is pSD466. The vaccinia deletion in pSD466 encompasses positions

[161,185-162,053]. The site of the deletion in pSD466 is indicated by a triangle in FIG. 4.

A 3.2 kb BglII/BamHI (partial) cassette containing the E . coli Beta-galactosidase gene (Shapira et al., 1983) under the control of the vaccinia 11 kDa promoter (Bertholet et al., 1985; Guo et al., 1989) was inserted into the BglII site of pSD466, forming pSD466KBG.

Plasmid pSD466KBG was used in recombination with rescuing virus vP618. Recombinant vaccinia virus, vP708, containing Beta-galactosidase in the A56R deletion, was isolated as a blue plaque in the presence of X-gal.

Beta-galactosidase sequences were deleted from vP708 using donor plasmid pSD467. pSD467 is identical to pSD466, except that EcoRI. SmaI and BamHI sites were removed from the pUC/vaccinia junction by digestion of pSD466 with EcoRI/BamHI followed by blunt ending with

Klenow fragment of E. coli polymerase and ligation.

Recombination between vP708 and pSD467 resulted in recombinant vaccinia deletion mutant, vP723, which was isolated as a clear plaque in the presence of X-gal.

EXAMPLE 5 - CONSTRUCTION OF PLASMID pMPCSKlΔ FOR

DELETION OF OPEN READING FRAMES [C7L-K1L] Referring now to FIG. 5, the following vaccinia clones were utilized in the construction of pMPCSK1Δ. pSD420 is SalI H cloned into pUC8. pSD435 is KpnI F cloned into pUC18. pSD435 was cut with SphI and

religated, forming pSD451. In pSD451, DNA sequences to the left of the SphI site (pos. 27,416) in HindIII M are removed (Perkus et al., 1990). pSD409 is HindIII M cloned into pUC8.

To provide a substrate for the deletion of the [C7L-K1L] gene cluster from vaccinia, E. coli Beta-galactosidase was first inserted into the vaccinia M2L deletion locus (Guo et al., 1990) as follows. To

eliminate the BglII site in pSD409, the plasmid was cut with BglII in vaccinia sequences (pos. 28,212) and with BamHI at the pUC/vaccinia junction, then ligated to form plasmid pMP409B. pMP409B was cut at the unique SphI site

(pos. 27,416). M2L coding sequences were removed by mutagenesis (Guo et al., 1990; Mandecki, 1986) using synthetic oligonucleotide

The resulting plasmid, pMP409D, contains a unique BglII site inserted into the M2L deletion locus as indicated above. A 3.2 kb BamHI (partial)/BglII cassette containing the E. coli Beta-galactosidase gene (Shapira et al., 1983) under the control of the 11 kDa promoter (Bertholet et al., 1985) was inserted into pMP409D cut with BglII. The resulting plasmid, pMP409DBG (Guo et al., 1990), was used as donor plasmid for recombination with rescuing vaccinia virus vP723. Recombinant vaccinia virus, vP784, containing Beta-galactosidase inserted into the M2L deletion locus, was isolated as a blue plaque in the presence of X-gal.

A plasmid deleted for vaccinia genes [C7L-K1L] was assembled in pUC8 cut with SmaI. HindIII and blunt ended with Klenow fragment of E . coli polymerase. The left flanking arm consisting of vaccinia HindIII C sequences was obtained by digestion of pSD420 with XbaI (pos.

18,628) followed by blunt ending with Klenow fragment of E. coli polymerase and digestion with BglII (pos.

19,706). The right flanking arm consisting of vaccinia HindIII K sequences was obtained by digestion of pSD451 with BglII (pos. 29,062) and EcoRV (pos. 29,778). The resulting plasmid, pMP581CK is deleted for vaccinia sequences between the BglII site (pos. 19,706) in HindIII C and the BglII site (pos. 29,062) in HindIII K. The site of the deletion of vaccinia sequences in plasmid pMP581CK is indicated by a triangle in FIG. 5.

To remove excess DNA at the vaccinia deletion junction, plasmid pMP581CK, was cut at the NcoI sites within vaccinia sequences (pos. 18,811; 19,655), treated with Bal-31 exonuclease and subjected to mutagenesis (Mandecki, 1986) using synthetic oligonucleotide MPSYN233 (SEQ ID NO:20)

5'-TGTCATTTAACACTATACTCATATTAATAAAAATAATATTTATT-3'.

The resulting plasmid, pMPCSK1Δ, is deleted for vaccinia sequences positions 18,805-29,108, encompassing 12 vaccinia open reading frames [C7L - K1L]. Recombination between pMPCSK1Δ and the Beta-galactosidase containing vaccinia recombinant, vP784, resulted in vaccinia deletion mutant, vP804, which was isolated as a clear plaque in the presence of X-gal.

EXAMPLE 6 - CONSTRUCTION OF PLASMID pSD548

FOR DELETION OF LARGE SUBUNIT,

RIBONUCLEOTIDE REDUCTASE (I4L)

Referring now to FIG. 6, plasmid pSD405 contains vaccinia HindIII I (pos. 63,875-70,367) cloned in pUC8. pSD405 was digested with EcoRV within vaccinia sequences (pos. 67,933) and with SmaI at the pUC/vaccinia junction, and ligated, forming plasmid pSD518. pSD518 was used as the source of all the vaccinia restriction fragments used in the construction of pSD548.

The vaccinia I4L gene extends from position 67,371-65,059. Direction of transcription for I4L is indicated by an arrow in FIG. 6. To obtain a vector plasmid fragment deleted for a portion of the I4L coding

sequences, pSD518 was digested with BamHI (pos. 65,381) and HpaI (pos. 67,001) and blunt ended using Klenow fragment of E. coli polymerase. This 4.8 kb vector fragment was ligated with a 3.2 kb Smal cassette

containing the E. coli Beta-galactosidase gene (Shapira et al., 1983) under the control of the vaccinia 11 kDa promoter (Bertholet et al., 1985; Perkus et al., 1990), resulting in plasmid pSD524KBG. pSD524KBG was used as donor plasmid for recombination with vaccinia virus vP804. Recombinant vaccinia virus, vP855, containing Beta-galactosidase in a partial deletion of the I4L gene, was isolated as a blue plaque in the presence of X-gal.

To delete Beta-galactosidase and the remainder of the I4L ORF from vP855, deletion plasmid pSD548 was constructed. The left and right vaccinia flanking arms were assembled separately in pUC8 as detailed below and presented schematically in FIG. 6.

To construct a vector plasmid to accept the left vaccinia flanking arm, pUC8 was cut with BamHI/EcoRI and ligated with annealed synthetic oligonucleotides

518A1/518A2 (SEQ ID NO:21/SEQ ID NO:22)

forming plasmid pSD531. pSD531 was cut with RsaI

(partial) and BamHI and a 2.7 kb vector fragment

isolated. pSD518 was cut with BglII (pos. 64,459)/ RsaI

(pos. 64,994) and a 0.5 kb fragment isolated. The two fragments were ligated together, forming pSD537, which contains the complete vaccinia flanking arm left of the

I4L coding sequences.

To construct a vector plasmid to accept the right vaccinia flanking arm, pUC8 was cut with BamHI/EcoRI and ligated with annealed synthetic oligonucleotides

forming plasmid pSD532. pSD532 was cut with RsaI

(partial)/EcoRI and a 2.7 kb vector fragment isolated. pSD518 was cut with RsaI within vaccinia sequences (pos.

67,436) and EcoRI at the vaccinia/pUC junction, and a 0.6 kb fragment isolated. The two fragments were ligated together, forming pSD538, which contains the complete vaccinia flanking arm to the right of I4L coding

sequences.

The right vaccinia flanking arm was isolated as a 0.6 kb EcoRI/BglII fragment from pSD538 and ligated into pSD537 vector plasmid cut with EcoRI/BglII. In the resulting plasmid, pSD539, the I4L ORF (pos. 65,047-67,386) is replaced by a polylinker region, which is flanked by 0.6 kb vaccinia DNA to the left and 0.6 kb vaccinia DNA to the right, all in a pUC background. The site of deletion within vaccinia sequences is indicated by a triangle in FIG. 6. To avoid possible recombination of Beta-galactosidase sequences in the pUC-derived portion of pSD539 with Beta-galactosidase sequences in recombinant vaccinia virus vP855, the vaccinia I4L deletion cassette was moved from pSD539 into pRC11, a pUC derivative from which all Beta-galactosidase sequences have been removed and replaced with a polylinker region (Colinas et al., 1990). pSD539 was cut with EcoRI/PstI and the 1.2 kb fragment isolated. This fragment was ligated into pRCll cut with EcoRI/PstI (2.35 kb), forming pSD548. Recombination between pSD548 and the Beta-galactosidase containing vaccinia recombinant, vP855, resulted in vaccinia deletion mutant vP866, which was isolated as a clear plaque in the presence of X-gal.

DNA from recombinant vaccinia virus vP866 was analyzed by restriction digests followed by

electrophoresis on an agarose gel. The restriction patterns were as expected. Polymerase chain reactions (PCR) (Engelke et al., 1988) using vP866 as template and primers flanking the six deletion loci detailed above produced DNA fragments of the expected sizes. Sequence analysis of the PCR generated fragments around the areas of the deletion junctions confirmed that the junctions were as expected. Recombinant vaccinia virus vP866, containing the six engineered deletions as described above, was designated vaccinia vaccine strain "NYVAC."

EXAMPLE 7 - INSERTION OF A RABIES

GLYCOPROTEIN G GENE INTO NYVAC

The gene encoding rabies glycoprotein G under the control of the vaccinia H6 promoter (Taylor et al.,

1988a,b) was inserted into TK deletion plasmid pSD513. pSD513 is identical to plasmid pSD460 (FIG. 1) except for the presence of a polylinker region.

Referring now to FIG. 7, the polylinker region was inserted by cutting pSD460 with SmaI and ligating the plasmid vector with annealed synthetic oligonucleotides

to form vector plasmid pSD513. pSD513 was cut with SmaI and ligated with a SmaI ended 1.8 kb cassette containing the gene encoding the rabies glycoprotein G gene under the control of the vaccinia H6 promoter (Taylor et al., 1988a,b). The resulting plasmid was designated pRW842. pRW842 was used as donor plasmid for recombination with NYVAC rescuing virus (vP866). Recombinant vaccinia virus vP879 was identified by plaque hybridization using ³²P-labelled DNA probe to rabies glycoprotein G coding sequences.

The modified recombinant viruses of the present invention provide advantages as recombinant vaccine vectors. The attenuated virulence of the vector

advantageously reduces the opportunity for the

possibility of a runaway infection due to vaccination in the vaccinated individual and also diminishes

transmission from vaccinated to unvaccinated individuals or contamination of the environment.

The modified recombinant viruses are also

advantageously used in a method for expressing a gene product in a cell cultured in vitro by introducing into the cell the modified recombinant virus having foreign DNA which codes for and expresses gene products in the cell.

EXAMPLE 8 - CONSTRUCTION OF ALVAC RECOMBINANTS

EXPRESSING RABIES VIRUS GLYCOPROTEIN G

This example describes the development of ALVAC, a canarypox virus vector and, of a canarypox-rabies

recombinant designated as ALVAC-RG (vCP65) and its safety and efficacy.

Cells and Viruses. The parental canarypox virus (Rentschler strain) is a vaccinal strain for canaries. The vaccine strain was obtained from a wild type isolate and attenuated through more than 200 serial passages on chick embryo fibroblasts. A master viral seed was subjected to four successive plaque purifications under agar and one plaque clone was amplified through five additional passages after which the stock virus was used as the parental virus in in vitro recombination tests. The plaque purified canarypox isolate is designated

ALVAC.

Construction of a Canarypox Insertion Vector. An 880 bp canarypox PvuII fragment was cloned between the PvuII sites of pUC9 to form pRW764.5. The sequence of this fragment is shown in FIG. 8 (SEQ ID NO. 27) between positions 1372 and 2251. The limits of an open reading frame designated as C5 were defined. It was determined that the open reading frame was initiated at position 166 within the fragment and terminated at position 487. The C5 deletion was made without interruption of open reading frames. Bases from position 167 through position 455 were replaced with the sequence (SEQ ID NO: 28)

GCTTCCCGGGAATTCTAGCTAGCTAGTTT. This replacement sequence contains HindIII. Smal and EcoRI insertion sites followed by translation stops and a transcription termination signal recognized by vaccinia virus RNA polymerase (Yuen et al., 1987). Deletion of the C5 ORF was performed as described below. Plasmid pRW764.5 was partially cut with RsaI and the linear product was isolated. The RsaI linear fragment was recut with BglII and the pRW764.5 fragment now with a RsaI to BglII deletion from position 156 to position 462 was isolated and used as a vector for the following synthetic oligonucleotides:

RW145 (SEQ ID NO:29):

ACTCTCAAAAGCTTCCCGGGAATTCTAGCTAGCTAGTTTTTATAAA RW146 (SEQ ID NO: 30):

GATCTTTATAAAAACTAGCTAGCTAGAATTCCCGGGAAGCTTTTGAGAGT

Oligonucleotides RW145 and RW146 were annealed and inserted into the pRW 764.5 RsaI and BglII vector described above. The resulting plasmid is designated pRW831.

Construction of Insertion Vector Containing the Rabies G Gene. Construction of pRW838 is illustrated below. Oligonucleotides A through E, which overlap the translation initiation codon of the H6 promoter with the ATG of rabies G, were cloned into pUC9 as pRW737.

Oligonucleotides A through E contain the H6 promoter, starting at NruI. through the HindIII site of rabies G followed by BglII. Sequences of oligonucleotides A through E ((SEQ ID NO: 31)-(SEQ ID NO:35)) are:

The diagram of annealed oligonucleotides A through E is as follows:

Oligonucleotides A through E were kinased, annealed (95°C for 5 minutes, then cooled to room temperature), and inserted between the PvuII sites of pUC9. The resulting plasmid, pRW737, was cut with HindIII and BglII and used as a vector for the 1.6 kbp HindIII-BglII fragment of ptg155PRO (Kieny et al., 1984) generating pRW739. The ptg155PRO HindIII site is 86 bp downstream of the rabies G translation initiation codon. BglII is downstream of the rabies G translation stop codon in ptgl55PR0. pRW739 was partially cut with NruI. completely cut with BglII, and a 1.7 kbp NruI-BglII fragment, containing the 3 ' end of the H6 promoter previously described (Taylor et al., 1988a,b; Guo et al., 1989; Perkus et al., 1989) through the entire rabies G gene, was inserted between the NruI and BamHI sites of pRW824. The resulting plasmid is designated pRW832.

Insertion into pRW824 added the H6 promoter 5' of NruI. The pRW824 sequence of BamHI followed by SmaI is (SEQ ID NO: 36): GGATCCCCGGG. pRW824 is a plasmid that contains a nonpertinent gene linked precisely to the vaccinia virus H6 promoter. Digestion with NruI and BamHI completely excised this nonpertinent gene. The 1.8 kbp pRW832 SmaI fragment, containing H6 promoted rabies G, was inserted into the SmaI of pRW831, to form plasmid pRW838.

Development of ALVAC-RG. Plasmid pRW838 was

transfected into ALVAC infected primary CEF cells by using the calcium phosphate precipitation method

previously described (Panicali et al., 1982; Piccini et al., 1987). Positive plaques were selected on the basis of hybridization to a specific rabies G probe and

subjected to 6 sequential rounds of plaque purification until a pure population was achieved. One representative plaque was then amplified and the resulting ALVAC

recombinant was designated ALVAC-RG (vCP65) (see also

Figs. 9A and 9B). The correct insertion of the rabies G gene into the ALVAC genome without subsequent mutation was confirmed by sequence analysis.

Immunofluorescence. During the final stages of assembly of mature rabies virus particles, the

glycoprotein component is transported from the golgi apparatus to the plasma membrane where it accumulates with the carboxy terminus extending into the cytoplasm and the bulk of the protein on the external surface of the cell membrane. In order to confirm that the rabies glycoprotein expressed in ALVAC-RG was correctly

presented, immunofluorescence was performed on primary CEF cells infected with ALVAC or ALVAC-RG. Immunofluorescence was performed as previously described (Taylor et al., 2990) using a rabies G monoclonal antibody. Strong surface fluorescence was detected on CEF cells infected with ALVAC-RG but not with the parental ALVAC.

Immunoprecipitation. Preformed monolayers of primary CEF, Vero (a line of African Green monkey kidney cells ATCC # CCL81) and MRC-5 cells (a fibroblast-like cell line derived from normal human fetal lung tissue ATCC # CCL171) were inoculated at 10 pfu per cell with parental virus ALVAC and recombinant virus ALVAC-RG in the presence of radiolabelled ³⁵S-methionine and treated as previously described (Taylor et al., 1990).

Immunoprecipitation reactions were performed using a rabies G specific monoclonal antibody. Efficient

expression of a rabies specific glycoprotein with a molecular weight of approximately 67 kDa was detected with the recombinant ALVAC-RG. No rabies specific products were detected in uninfected cells or cells infected with the parental ALVAC virus.

Sequential Passaging Experiment. In studies with ALVAC virus in a range of non-avian species no

proliferative infection or overt disease was observed (Taylor et al., 1991b). However, in order to establish that neither the parental nor recombinant virus could be adapted to grow in non-avian cells, a sequential

passaging experiment was performed.

The two viruses, ALVAC and ALVAC-RG, were inoculated in 10 sequential blind passages in three cell substrates:

(l) Primary chick embryo fibroblast (CEF) cells

produced from 11 day old white leghorn embryos;

(2) Vero cells - a continuous line of African Green monkey kidney cells (ATCC # CCL81); and

(3) MRC-5 cells - a diploid cell line derived from human fetal lung tissue (ATCC # CCL171).

The initial inoculation was performed at an m.o.i. of 0.1 pfu per cell using three 60mm dishes of each cell substrate containing 2 X 10⁶ cells per dish. One dish was inoculated in the presence of 40μg/ml of Cytosine arabinoside (Ara C), an inhibitor of DNA replication. After an absorption period of 1 hour at 37°C, the

inoculum was removed and the monolayer washed to remove unabsorbed virus. At this time the medium was replaced with 5ml of EMEM + 2% NBCS on two dishes (samples to and t7) and 5ml of EMEM + 2% NBCS containing 40 μg/ml Ara C on the third (sample t7A). Sample to was frozen at -70°C to provide an indication of the residual input virus. Samples t7 and t7A were incubated at 37°C for 7 days, after which time the contents were harvested and the cells disrupted by indirect sonication.

One ml of sample t7 of each cell substrate was inoculated undiluted onto three dishes of the same cell substrate (to provide samples to, t7 and t7A) and onto one dish of primary CEF cells. Samples to, t7 and t7A were treated as for passage one. The additional

inoculation on CEF cells was included to provide an amplification step for more sensitive detection of virus which might be present in the non-avian cells.

This procedure was repeated for 10 (CEF and MRC-5) or 8 (Vero) sequential blind passages. Samples were then frozen and thawed three times and assayed by titration on primary CEF monolayers.

Virus yield in each sample was then determined by plaque titration on CEF monolayers under agarose.

Summarized results of the experiment are shown in Tables 1 and 2.

The results indicate that both the parental ALVAC and the recombinant ALVAC-RG are capable of sustained replication on CEF monolayers with no loss of titer. In Vero cells, levels of virus fell below the level of detection after 2 passages for ALVAC and 1 passage for ALVAC-RG. In MRC-5 cells, a similar result was evident, and no virus was detected after 1 passage. Although the results for only four passages are shown in Tables 1 and 2 the series was continued for 8 (Vero) and 10 (MRC-5) passages with no detectable adaptation of either virus to growth in the non-avian cells.

In passage 1 relatively high levels of virus were present in the t7 sample in MRC-5 and Vero cells.

However this level of virus was equivalent to that seen in the to sample and the t7A sample incubated in the presence of Cytosine arabinoside in which no viral replication can occur. This demonstrated that the levels of virus seen at 7 days in non-avian cells represented residual virus and not newly replicated virus.

In order to make the assay more sensitive, a portion of the 7 day harvest from each cell substrate was

inoculated onto a permissive CEF monolayer and harvested at cytopathic effect (CPE) or at 7 days if no CPE was evident. The results of this experiment are shown in Table 3. Even after amplification through a permissive cell substrate, virus was only detected in MRC-5 and Vero cells for two additional passages. These results

indicated that under the conditions used, there was no adaptation of either virus to growth in Vero or MRC-5 cells.

Inoculation of Macaques. Four HIV seropositive macaques were initially inoculated with ALVAC-RG as described in Table 4. After 100 days these animals were re-inoculated to determine a booster effect, and an additional seven animals were inoculated with a range of doses. Blood was drawn at appropriate intervals and sera analyzed, after heat inactivation at 56°C for 30 minutes, for the presence of anti-rabies antibody using the Rapid Fluorescent Focus Inhibition Assay (Smith et al., 1973).

Inoculation of Chimpanzees. Two adult male

chimpanzees (50 to 65 kg weight range) were inoculated intramuscularly or subcutaneously with 1 X 10⁷ pfu of vCP65. Animals were monitored for reactions and bled at regular intervals for analysis for the presence of anti-rabies antibody with the RFFI test (Smith et al., 1973). Animals were re-inoculated with an equivalent dose 13 weeks after the initial inoculation.

Inoculation of Mice. Groups of mice were inoculated with 50 to 100 μl of a range of dilutions of different batches of vCP65. Mice were inoculated in the footpad. On day 14, mice were challenged by intracranial

inoculation of from 15 to 43 mouse LD₅₀ of the virulent CVS strain of rabies virus. Survival of mice was

monitored and a protective dose 50% (PD₅₀) calculated at 28 days post-inoculation.

Inoculation of Dogs and Cats. Ten beagle dogs, 5 months old, and 10 cats, 4 months old, were inoculated subcutaneously with either 6.7 or 7.7 log₁₀ TCID₅₀ of ALVAC-RG. Four dogs and four cats were not inoculated. Animals were bled at 14 and 28 days post-inoculation and anti-rabies antibody assessed in an RFFI test. The animals receiving 6.7 log₁₀ TCID₅₀ of ALVAC-RG were challenged at 29 days post-vaccination with 3.7 log₁₀ mouse LD₅₀ (dogs) or 4.3 log₁₀ mouse LD₅₀ (cats) of the NYGS rabies virus challenge strain.

Inoculation of Squirrel Monkeys. Three groups of four squirrel monkeys (Saimiri sciureus) were inoculated with one of three viruses (a) ALVAC, the parental

canarypox virus, (b) ALVAC-RG, the recombinant expressing the rabies G glycoprotein or (c) vCP37, a canarypox recombinant expressing the envelope glycoprotein of feline leukemia virus. Inoculations were performed under ketamine anaesthesia. Each animal received at the same time: (1) 20 μl instilled on the surface of the right eye without scarification; (2) 100 μl as several droplets in the mouth; (3) 100 μl in each of two intradermal

injection sites in the shaven skin of the external face of the right arm; and (4) 100 μl in the anterior muscle of the right thigh.

Four monkeys were inoculated with each virus, two with a total of 5.0 log₁₀ pfu and two with a total of 7.0 log₁₀ pfu. Animals were bled at regular intervals and sera analyzed for the presence of antirabies antibody using an RFFI test (Smith et al., 1973). Animals were monitored daily for reactions to vaccination. Six months after the initial inoculation the four monkeys receiving ALVAC-RG, two monkeys initially receiving vCP37, and two monkeys initially receiving ALVAC, as well as one naive monkey were inoculated with 6.5 log₁₀ pfu of ALVAC-RG subcutaneously. Sera were monitored for the presence of rabies neutralizing antibody in an RFFI test (Smith et al., 1973).

Inoculation of Human Cell Lines with ALVAC-RG. In order to determine whether efficient expression of a foreign gene could be obtained in non-avian cells in which the virus does not productively replicate, five cell types, one avian and four non-avian, were analyzed for virus yield, expression of the foreign rabies G gene and viral specific DNA accumulation. The cells

inoculated were:

(a) Vero, African Green monkey kidney cells, ATCC # CCL81;

(b) MRC-5, human embryonic lung, ATCC # CCL 171;

(c) WISH human amnion, ATCC # CCL 25;

(d) Detroit-532, human foreskin, Downs's syndrome, ATCC # CCL 54; and

(e) Primary CEF cells.

Chicken embryo fibroblast cells produced from 11 day old white leghorn embryos were included as a positive control. All inoculations were performed on preformed monolayers of 2 X 10⁶ cells as discussed below.

A. Methods for DNA analysis.

Three dishes of each cell line were inoculated at 5 pfu/cell of the virus under test, allowing one extra dish of each cell line un-inoculated. One dish was incubated in the presence of 40 μg/ml of cytosine arabinoside (Ara C). After an adsorption period of 60 minutes at 37°C, the inoculum was removed and the monolayer washed twice to remove unadsorbed virus. Medium (with or without Ara C) was then replaced. Cells from one dish (without Ara C) were harvested as a time zero sample. The remaining dishes were incubated at 37°C for 72 hours, at which time the cells were harvested and used to analyze DNA

accumulation. Each sample of 2 X 10⁶ cells was resuspended in 0.5 ml phosphate buffered saline (PBS) containing 40 mM EDTA and incubated for 5 minutes at 37°C. An equal volume of 1.5% agarose prewarmed at 42°C and containing 120 mM EDTA was added to the cell suspension and gently mixed. The suspension was transferred to an agarose plug mold and allowed to harden for at least 15 min. The agarose plugs were then removed and incubated for 12-16 hours at 50°C in a volume of lysis buffer (1% sarkosyl, 100 μg/ml proteinase K, 10 mM Tris HCl pH 7.5, 200 mM EDTA) that completely covers the plug. The lysis buffer was then replaced with 5.0 ml sterile 0.5 X TBE (44.5 mM Tris-borate, 44.5 mM boric acid, 0.5 mM EDTA) and equilibrated at 4°C for 6 hours with 3 changes of TBE buffer. The viral DNA within the plug was fractionated from cellular RNA and DNA using a pulse field electrophoresis system. Electrophoresis was performed for 20 hours at 180 V with a ramp of 50-90 sec at 15°C in 0.5 X TBE. The DNA was run with lambda DNA molecular weight

standards. After electrophoresis the viral DNA band was visualized by staining with ethidium bromide. The DNA was then transferred to a nitrocellulose membrane and probed with a radiolabelled probe prepared from purified ALVAC genomic DNA.

B. Estimation of virus yield.

Dishes were inoculated exactly as described above, with the exception that input multiplicity was 0.1 pfu/cell. At 72 hours post infection, cells were lysed by three successive cycles of freezing and thawing. Virus yield was assessed by plaque titration on CEF monolayers.

C. Analysis of expression of Rabies G gene.

Dishes were inoculated with recombinant or parental virus at a multiplicity of 10 pfu/cell, allowing an additional dish as an uninfected virus control.

After a one hour absorption period, the medium was removed and replaced with methionine free medium.

After a 30 minute period, this medium was replaced with methionine-free medium containing 25 uCi/ml of

³⁵S-Methionine. Infected cells were labelled overnight (approximately 16 hours), then lysed by the addition of buffer A lysis buffer.

Immunoprecipitation was performed as previously described (Taylor et al., 1990) using a rabies G specific monoclonal antibody.

Results: Estimation of Viral Yield. The results of titration for yield at 72 hours after inoculation at 0.1 pfu per cell are shown in Table 5. The results indicate that while a productive infection can be attained in the avian cells, no increase in virus yield can be detected by this method in the four non-avian cell systems.

Analysis of Viral DNA Accumulation. In order to determine whether the block to productive viral

replication in the non-avian cells occurred before or after DNA replication, DNA from the cell lysates was fractionated by electrophoresis, transferred to

nitrocellulose and probed for the presence of viral specific DNA. DNA from uninfected CEF cells, ALVAC-RG infected CEF cells at time zero, ALVAC-RG infected CEF cells at 72 hours post-infection and ALVAC-RG infected CEF cells at 72 hours post-infection in the presence of 40 μg/ml of cytosine arabinoside all showed some

background activity, probably due to contaminating CEF cellular DNA in the radiolabelled ALVAC DNA probe preparation. However, ALVAC-RG infected CEF cells at 72 hours post-infection exhibited a strong band in the region of approximately 350 kbp representing ALVAC-specific viral DNA accumulation. No such band is

detectable when the culture is incubated in the presence of the DNA synthesis inhibitor, cytosine arabinoside. Equivalent samples produced in Vero cells showed a very faint band at approximately 350 kbp in the ALVAC-RG infected Vero cells at time zero. This level represented residual virus. The intensity of the band was amplified at 72 hours post-infection indicating that some level of viral specific DNA replication had occurred in Vero cells which had not resulted in an increase in viral progeny. Equivalent samples produced in MRC-5 cells indicated that no viral specific DNA accumulation was detected under these conditions in this cell line. This experiment was then extended to include additional human cell lines, specifically WISH and Detroit-532 cells. ALVAC infected CEF cells served as a positive control. No viral

specific DNA accumulation was detected in either WISH or Detroit cells inoculated with ALVAC-RG. It should be noted that the limits of detection of this method have not been fully ascertained and viral DNA accumulation may be occurring, but at a level below the sensitivity of the method. Other experiments in which viral DNA replication was measured by ³H-thymidine incorporation support the results obtained with Vero and MRC-5 cells.

Analysis of Rabies Gene Expression. To determine if any viral gene expression, particularly that of the inserted foreign gene, was occurring in the human cell lines even in the absence of viral DNA replication, immunoprecipitation experiments were performed on ³⁵S-methionine labelled lysates of avian and non-avian cells infected with ALVAC and ALVAC-RG. The results of

immunoprecipitation using a rabies G specific monoclonal antibody illustrated specific immunoprecipitation of a 67 kDa glycoprotein in CEF, Vero and MRC-5, WISH and Detroit cells infected with ALVAC-RG. No such specific rabies gene products were detected in any of the uninfected and parentally infected cell lysates.

The results of this experiment indicated that in the human cell lines analyzed, although the ALVAC-RG

recombinant was able to initiate an infection and express a foreign gene product under the transcriptional control of the H6 early/late vaccinia virus promoter, the

replication did not proceed through DNA replication, nor was there any detectable viral progeny produced. In the Vero cells, although some level of ALVAC-RG specific DNA accumulation was observed, no viral progeny was detected by these methods. These results would indicate that in the human cell lines analyzed the block to viral

replication occurs prior to the onset of DNA replication, while in Vero cells, the block occurs following the onset of viral DNA replication.

In order to determine whether the rabies

glycoprotein expressed in ALVAC-RG was immunogenic, a number of animal species were tested by inoculation of the recombinant. The efficacy of current rabies vaccines is evaluated in a mouse model system. A similar test was therefore performed using ALVAC-RG. Nine different preparations of virus (including one vaccine batch (J) produced after 10 serial tissue culture passages of the seed virus) with infectious titers ranging from 6.7 to 8.4 log₁₀ TCID₅₀ per ml were serially diluted and 50 to 100 μl of dilutions inoculated into the footpad of four to six week old mice. Mice were challenged 14 days later by the intracranial route with 300 μl of the CVS strain of rabies virus containing from 15 to 43 mouse LD₅₀ as determined by lethality titration in a control group of mice. Potency, expressed as the PD₅₀ (Protective dose 50%), was calculated at 14 days post-challenge. The results of the experiment are shown in Table 6. The results indicated that ALVAC-RG was consistently able to protect mice against rabies virus challenge with a PD₅₀ value ranging from 3.33 to 4.56 with a mean value of 3.73 (STD 0.48). As an extension of this study, male mice were inoculated intracranially with 50 μl of virus containing 6.0 log₁₀ TCID₅₀ of ALVAC-RG or with an

equivalent volume of an uninfected cell suspension. Mice were sacrificed on days l, 3 and 6 post-inoculation and their brains removed, fixed and sectioned.

Histopathological examination showed no evidence for neurovirulence of ALVAC-RG in mice.

In order to evaluate the safety and efficacy of ALVAC-RG for dogs and cats, a group of 14, 5 month old beagles and 14, 4 month old cats were analyzed. Four animals in each species were not vaccinated. Five animals received 6.7 log₁₀ TCID₅₀ subcutaneously and five animals received 7.7 log₁₀ TCID₅₀ by the same route.

Animals were bled for analysis for anti-rabies antibody. Animals receiving no inoculation or 6.7 log₁₀ TCID₅₀ of ALVAC-RG were challenged at 29 days post-vaccination with 3.7 log₁₀ mouse LD₅₀ (dogs, in the temporal muscle) or 4.3 log₁₀ mouse LD₅₀ (cats, in the neck) of the NYGS rabies virus challenge strain. The results of the experiment are shown in Table 7.

No adverse reactions to inoculation were seen in either cats or dogs with either dose of inoculum virus. Four of 5 dogs immunized with 6.7 log₁₀ TCID₅₀ had antibody titers on day 14 post-vaccination and all dogs had titers at 29 days. All dogs were protected from a challenge which killed three out of four controls. In cats, three of five cats receiving 6.7 log₁₀ TCID₅₀ had specific antibody titers on day 14 and all cats were positive on day 29 although the mean antibody titer was low at 2.9 IU. Three of five cats survived a challenge which killed all controls. All cats immunized with 7.7 log₁₀ TCID₅₀ had antibody titers on day 14 and at day 29 the Geometric Mean Titer was calculated as 8.1

International Units.

The immune response of squirrel monkeys (Saimiri sciureus) to inoculation with ALVAC, ALVAC-RG and an unrelated canarypox virus recombinant was examined.

Groups of monkeys were inoculated as described above and sera analyzed for the presence of rabies specific

antibody. Apart from minor typical skin reactions to inoculation by the intradermal route, no adverse

reactivity was seen in any of the monkeys. Small amounts of residual virus were isolated from skin lesions after intradermal inoculation on days two and four post-inoculation only. All specimens were negative on day seven and later. There was no local reaction to intramuscular injection. All four monkeys inoculated with ALVAC-RG developed anti-rabies serum neutralizing

antibodies as measured in an RFFI test. Approximately six months after the initial inoculation all monkeys and one additional naive monkey were re-inoculated by the subcutaneous route on the external face of the left thigh with 6.5 log₁₀ TCID₅₀ of ALVAC-RG. Sera were analyzed for the presence of anti-rabies antibody. The results are shown in Table 8.

Four of the five monkeys naive to rabies developed a serological response by seven days post-inoculation with ALVAC-RG. All five monkeys had detectable antibody by 11 days post-inoculation. Of the four monkeys with previous exposure to the rabies glycoprotein, all showed a

significant increase in serum neutralization titer between days 3 and 7 post-vaccination. The results indicate that vaccination of squirrel monkeys with ALVAC-RG does not produce adverse side-effects and a primary neutralizing antibody response can be induced. An anamnestic response is also induced on re-vaccination. Prior exposure to ALVAC or to a canarypox recombinant expressing an unrelated foreign gene does not interfere with induction of an anti-rabies immune response upon re-vaccination.

The immunological response of HIV-2 seropositive macaques to inoculation with ALVAC-RG was assessed.

Animals were inoculated as described above and the presence of anti-rabies serum neutralizing antibody assessed in an RFFI test. The results, shown in Table 9, indicated that HIV-2 positive animals inoculated by the subcutaneous route developed anti-rabies antibody by 11 days after one inoculation. An anamnestic response was detected after a booster inoculation given approximately three months after the first inoculation. No response was detected in animals receiving the recombinant by the oral route. In addition, a series of six animals were inoculated with decreasing doses of ALVAC-RG given by either the intra-muscular or subcutaneous routes. Five of the six animals inoculated responded by 14 days post-vaccination with no significant difference in antibody titer.

Two chimpanzees with prior exposure to HIV were inoculated with 7.0 log₁₀ pfu of ALVAC-RG by the

subcutaneous or intra-muscular route. At 3 months post-inoculations both animals were re-vaccinated in an identical fashion. The results are shown in Table 10.

No adverse reactivity to inoculation was noted by either intramuscular or subcutaneous routes. Both chimpanzees responded to primary inoculation by 14 days and a strongly rising response was detected following re-vaccination.

EXAMPLE 9 - IMMUNIZATION OF HUMANS USING CANARYPOX

EXPRESSING RABIES GLYCOPROTEIN

(ALVAC-RG; vCP65)

ALVAC-RG (vCP65) was generated as described in Example 9 and FIGS. 9A and 9B. For scaling-up and vaccine manufacturing ALVAC-RG (vCP65) was grown in primary CEF derived from specified pathogen free eggs. Cells were infected at a multiplicity of 0.1 and

incubated at 37°C for three days.

The vaccine virus suspension was obtained by

ultrasonic disruption in serum free medium of the infected cells; cell debris were then removed by

centrifugation and filtration. The resulting clarified suspension was supplemented with lyophilization

stabilizer (mixture of amino-acids), dispensed in single dose vials and freeze dried. Three batches of decreasing titer were prepared by ten-fold serial dilutions of the virus suspension in a mixture of serum free medium and lyophilization stabilizer, prior to lyophilization.

Quality control tests were applied to the cell substrates, media and virus seeds and final product with emphasis on the search for adventitious agents and inocuity in laboratory rodents. No undesirable trait was found.

Preclinical data. Studies in vitro indicated that VERO or MRC-5 cells do not support the growth of ALVAC-RG (vCP65); a series of eight (VERO) and 10 (MRC) blind serial passages caused no detectable adaptation of the virus to grow in these non avian lines. Analyses of human cell lines (MRC-5, WISH, Detroit 532, HEL, HNK or EBV-transformed lymphoblastoid cells) infected or

inoculated with ALVAC-RG (vCP65) showed no accumulation of virus specific DNA suggesting that in these cells the block in replication occurs prior to DNA synthesis.

Significantly, however, the expression of the rabies virus glycoprotein gene in all cell lines tested

indicating that the abortive step in the canarypox replication cycle occurs prior to viral DNA replication. The safety and efficacy of ALVAC-RG (vCP65) were documented in a series of experiments in animals. A number of species including canaries, chickens, ducks, geese, laboratory rodents (suckling and adult mice), hamsters, guinea-pigs, rabbits, cats and dogs, squirrel monkeys, rhesus macaques and chimpanzees, were inoculated with doses ranging from 10⁵ to 10⁸ pfu. A variety of routes were used, most commonly subcutaneous,

intramuscular and intradermal but also oral (monkeys and mice) and intracerebral (mice).

In canaries, ALVAC-RG (vCP65) caused a "take" lesion at the site of scarification with no indication of disease or death. Intradermal inoculation of rabbits resulted in a typical poxvirus inoculation reaction which did not spread and healed in seven to ten days. There was no adverse side effects due to canarypox in any of the animal tests. Immunogenicity was documented by the development of anti-rabies antibodies following

inoculation of ALVAC-RG (vCP65) in rodents, dogs, cats, and primates, as measured by Rapid Fluorescent Focus Inhibition Test (RFFIT). Protection was also

demonstrated by rabies virus challenge experiments in mice, dogs, and cats immunized with ALVAC-RG (vCP65).

Volunteers. Twenty-five healthy adults aged 20-45 with no previous history of rabies immunization were enrolled. Their health status was assessed by complete medical histories, physical examinations, hematological and blood chemistry analyses. Exclusion criteria

included pregnancy, allergies, immune depression of any kind, chronic debilitating disease, cancer, injection of immune globins in the past three months, and

seropositivity to human immunodeficiency virus (HIV) or to hepatitis B virus surface antigen.

Study design. Participants were randomly allocated to receive either standard Human Diploid Cell Rabies Vaccine (HDC) batch no E0751 (Pasteur Merieux Serums & Vaccine, Lyon, France) or the study vaccine ALVAC-RG (vCP65).

The trial was designated as a dose escalation study. Three batches of experimental ALVAC-RG (vCP65) vaccine were used sequentially in three groups of volunteers

(Groups A, B and C) with two week intervals between each step. The concentration of the three batches was 10^3.5, 10^4.5, 10^5.5 Tissue Culture Infectious Dose (TCID₅₀) per dose, respectively.

Each volunteer received two doses of the same vaccine subcutaneously in the deltoid region at an interval of four weeks. The nature of the injected vaccine was not known by the participants at the time of the first injection but was known by the investigator.

In order to minimize the risk of immediate

hypersensitivity at the time of the second injection, the volunteers of Group B allocated to the medium dose of experimental vaccine were injected 1 h previously with the lower dose and those allocated to the higher dose (Group C) received successively the lower and the medium dose at hourly intervals.

Six months later, the recipients of the highest dosage of ALVAC-RG (vCP65) (Group C) and HDC vaccine were offered a third dose of vaccine; they were then

randomized to receive either the same vaccine as

previously or the alternate vaccine. As a result, four groups were formed corresponding to the following

immunization scheme: 1. HDC , HDC - HDC; 2 . HDC, HDC - ALVAC-RG (vCP65); 3. ALVAC-RG (vCP65) , ALVAC-RG (vCP65) - HDC; 4. ALVAC-RG (vCP65), ALVAC-RG (vCP65), ALVAC-RG (vCP65).

Monitoring of Side Effects. All subjects were monitored for 1 h after injection and re-examined every day for the next five days. They were asked to record local and systemic reactions for the next three weeks and were questioned by telephone two times a week. Laboratory Investigators. Blood specimens were obtained before enrollment and two, four and six days after each injection. Analysis included complete blood cell count, liver enzymes and creatine kinase assays.

Antibody assays. Antibody assays were performed seven days prior to the first injection and at days 7, 28, 35, 56, 173, 187 and 208 of the study.

The levels of neutralizing antibodies to rabies were determined using the Rapid Fluorescent Focus Inhibition test (RFFIT) (Smith et al., 1973). Canarypox antibodies were measured by direct ELISA. The antigen, a suspension of purified canarypox virus disrupted with 0.1% Triton X100, was coated in microplates. Fixed dilutions of the sera were reacted for two hours at room temperature and reacting antibodies were revealed with a peroxidase labelled anti-human IgG goat serum. The results are expressed as the optical density read at 490nm.

Analysis. Twenty-five subjects were enrolled and completed the study. There were 10 males and 15 females and the mean age was 31.9 (21 to 48). All but three subjects had evidence of previous smallpox vaccination; the three remaining subjects had no typical scar and vaccination history. Three subjects received each of the lower doses of experimental vaccine (10^3.5 and 10^4.5

TCID₅₀), nine subjects received 10^5.5 TCID₅₀ and ten received the HDC vaccine.

Safety (Table 11). During the primary series of immunization, fever greater than 37.7°C was noted within 24 hours after injection in one HDC recipient (37.8°C) and in one vCP65 10^5.5 TCID₅₀ recipient (38°C). No other systemic reaction attributable to vaccination was

observed in any participant.

Local reactions were noted in 9/10 recipients of HDC vaccine injected subcutaneously and in 0/3, 1/3 and 9/9 recipients of vCP65 10^3.5, 10^4.5, 10^5.5 TCID₅₀,

respectively. Tenderness was the most common symptoms and was always mild. Other local symptoms included redness and induration which were also mild and transient. All symptoms usually subsided within 24 hours and never lasted more than 72 hours.

There was no significant change in blood cell counts, liver enzymes or creatine kinase values.

Immune Responses: Neutralizing Antibodies to Rabies (Table 12). Twenty eight days after the first injection all the HDC recipients had protective titers (≥0.5

IU/ml). By contrast none in groups A and B (10^3,5 and 10^4.5 TCID₅₀) and only 2/9 in group C (10^5.5 TCID₅₀) ALVAC-RG (vCP65) recipients reached this protective titer.

At day 56 (i.e. 28 days after the second injection) protective titers were achieved in 0/3 of Group A, 2/3 of Group B and 9/9 of Group C recipients of ALVAC-RG (vCP65) vaccine and persisted in all 10 HDC recipients.

At day 56 the geometric mean titers were 0.05, 0.47, 4.4 and 11.5 IU/ml in groups A, B, C and HDC

respectively.

At day 180, the rabies antibody titers had

substantially decreased in all subjects but remained above the minimum protective titer of 0.5 IU/ml in 5/10 HCD recipients and in 5/9 ALVAC-RG (vCP65) recipients; the geometric mean titers were 0.51 and 0.45 IU/ml in groups HCD and C, respectively.

Antibodies to the Canarypox virus (Table 13). The pre-immune titers observed varied widely with titers varying from 0.22 to 1.23 O.D. units despite the absence of any previous contact with canary birds in those subjects with the highest titers. When defined as a greater than two-fold increase between preimmunization and post second injection titers, a seroconversion was obtained in 1/3 subjects in group B and in 9/9 subjects in group C whereas no subject seroconverted in groups A or HDC. Booster Injection. The vaccine was similarly well tolerated six months later, at the time of the booster injection: fever was noted in 2/9 HDC booster recipients and in 1/10 ALVAC-RG (vCP65) booster recipients. Local reactions were present in 5/9 recipients of HDC booster and in 6/10 recipients of the ALVAC-RG (vCP65) booster.

Observations. Figs. 11A-11D show graphs of rabies neutralizing antibody titers (Rapid Fluorescent Focus Inhibition Test or RFFIT, IU/ml): Booster effect of HDC and vCP65 (10^5.5 TCID₅₀) in volunteers previously

immunized with either the same or the alternate vaccine. Vaccines were given at days 0, 28 and 180. Antibody titers were measured at days 0, 7, 28, 35, 56, 173, and 187 and 208.

As shown in FIGS. 11A to 11D, the booster dose given resulted in a further increase in rabies antibody titers in every subject whatever the immunization scheme.

However, the ALVAC-RG (vCP65) booster globally elicited lower immune responses than the HDC booster and the

ALVAC-RG (vCP65), ALVAC-RG (vCP65) - ALVAC-RG (vCP65) group had significantly lower titers than the three other groups. Similarly, the ALVAC-RG (vCP65) booster

injection resulted in an increase in canarypox antibody titers in 3/5 subjects who had previously received the HDC vaccine and in all five subjects previously immunized With ALVAC-RG (vCP65).

In general, none of the local side effects from administration of vCP65 was indicative of a local

replication of the virus. In particular, lesions of the skin such as those observed after injection of vaccine were absent. In spite of the apparent absence of

replication of the virus, the injection resulted in the volunteers generating significant amounts of antibodies to both the canarypox vector and to the expressed rabies glycoprotein.

Rabies neutralizing antibodies were assayed with the Rapid Fluorescent Focus Inhibition Test (RFFIT) which is known to correlate well with the sero neutralization test in mice. Of 9 recipients of 10^5.5 TCID₅₀, five had low level responses after the first dose. Protective titers of rabies antibodies were obtained after the second injection in all recipients of the highest dose tested and even in 2 of the 3 recipients of the medium dose. In this study, both vaccines were given subcutaneously as usually recommended for live vaccines, but not for the inactivated HDC vaccine. This route of injection was selected as it best allowed a careful examination of the injection site, but this could explain the late

appearance of antibodies in HDC recipients: indeed, none of the HDC recipients had an antibody increase at day 7, whereas, in most studies where HDC vaccine is give intramuscularly a significant proportion of subjects do (Klietmann et al., Int'l Green Cross - Geneva, 1981;

Kuwert et al., Int'l Green Cross - Geneva, 1981).

However, this invention is not necessarily limited to the subcutaneous route of administration.

The GMT (geometric mean titers) of rabies

neutralizing antibodies was lower with the

investigational vaccine than with the HDC control

vaccine, but still well above the minimum titer required for protection. The clear dose effect response obtained with the three dosages used in this study suggest that a higher dosage might induce a stronger response.

Certainly from this disclosure the skilled artisan can select an appropriate dosage for a given patient.

The ability to boost the antibody response is another important result of this Example; indeed, an increase in rabies antibody titers was obtained in every subject after the 6 month dose whatever the immunization scheme, showing that preexisting immunity elicited by either the canarypox vector or the rabies glycoprotein had no blocking effect on the booster with the

recombinant vaccine candidate or the conventional HDC rabies vaccine. This contrasts findings of others with vaccinia recombinants in humans that immune response may be blocked by pre-existing immunity (Cooney et al.;

Etinger et al.).

Thus, this Example clearly demonstrates that a non- replicating poxvirus can serve as an immunizing vector in humans, with all of the advantages that replicating agents confer on the immune response, but without the safety problem created by a fully permissive virus. And, from this disclosure such as this Example and other

Examples suitable dosages and modes or routes for

administration or immunization of recombinants containing either rabies or other coding, or expression products thereof, are within the ambit of the skilled artisan as well modes for in vitro expression.

EXAMPLE 10 - COMPARISON OF THE LD₅₀ OF ALVAC AND

NYVAC WITH VARIOUS VACCINIA VIRUS STRAINS

Mice. Male outbred Swiss Webster mice were

purchased from Taconic Farms (Germantown, NY) and

maintained on mouse chow and water ad libitum until use at 3 weeks of age ("normal" mice). Newborn outbred Swiss Webster mice were of both sexes and were obtained following timed pregnancies performed by Taconic Farms. All newborn mice used were delivered within a two day period.

Viruses. ALVAC was derived by plaque purification of a canarypox virus population and was prepared in primary chick embryo fibroblast cells (CEF). Following purification by centrifugation over sucrose density gradients, ALVAC was enumerated for plaque forming units in CEF cells. The WR(L) variant of vaccinia virus was derived by selection of large plaque phenotypes of WR (Panicali et al., 1981). The Wyeth New York State Board of Health vaccine strain of vaccinia virus was obtained from Pharmaceuticals Calf Lymph Type vaccine Dryvax, control number 302001B. Copenhagen strain vaccinia virus VC-2 was obtained from Institut Merieux, France.

Vaccinia virus strain NYVAC was derived from Copenhagen VC-2. All vaccinia virus strains except the Wyeth strain were cultivated in Vero African green monkey kidney cells, purified by sucrose gradient density

centrifugation and enumerated for plaque forming units on Vero cells. The Wyeth strain was grown in CEF cells and enumerated for plaque forming units in CEF cells.

Inoculations. Groups of 10 normal mice were

inoculated intracranially (ic) with 0.05 ml of one of several dilutions of virus prepared by 10-fold serially diluting the stock preparations in sterile phosphate-buffered saline. In some instances, undiluted stock virus preparation was used for inoculation. Groups of 10 newborn mice, 1 to 2 days old, were inoculated ic similarly to the normal mice except that an injection volume of 0.03 ml was used.

All mice were observed daily for mortality for a period of 14 days (newborn mice) or 21 days (normal mice) after inoculation. Mice found dead the morning following inoculation were excluded due to potential death by trauma.

The lethal dose required to produce mortality for 50% of the experimental population (LD₅₀) was determined by the proportional method of Reed and Muench.

Comparison of the LD₅₀ of ALVAC and NYVAC with

Various Vaccinia Virus Strains for Normal. Young Outbred Mice by the ic Route. In young, normal mice, the

virulence of NYVAC and ALVAC were several orders of magnitude lower than the other vaccinia virus strains tested (Table 14). NYVAC and ALVAC were found to be over 3,000 times less virulent in normal mice than the Wyeth strain; over 12,500 times less virulent than the parental VC-2 strain; and over 63,000,000 times less virulent than the WR(L) variant. These results would suggest that NYVAC is highly attenuated compared to other vaccinia strains, and that ALVAC is generally nonvirulent for young mice when administered intracranially, although both may cause mortality in mice at extremely high doses (3.85×10⁸ PFUs, ALVAC and 3×10⁸ PFUs, NYVAC) by an undetermined mechanism by this route of inoculation.

Comparison of the LD₅₀ of ALVAC and NYVAC with

Various Vaccinia Virus Strains for Newborn Outbred Mice by the ic Route. The relative virulence of 5 poxvirus strains for normal, newborn mice was tested by titration in an intracranial (ic) challenge model system (Table 15). With mortality as the endpoint, LD₅₀ values

indicated that ALVAC is over 100,000 times less virulent than the Wyeth vaccine strain of vaccinia virus; over 200,000 times less virulent than the Copenhagen VC-2 strain of vaccinia virus; and over 25,000,000 times less virulent than the WR-L variant of vaccinia virus.

Nonetheless, at the highest dose tested, 6.3×10⁷ PFUs, 100% mortality resulted. Mortality rates of 33.3% were observed at 6.3×10⁶ PFUs. The cause of death, while not actually determined, was not likely of toxicological or traumatic nature since the mean survival time (MST) of mice of the highest dosage group (approximately 6.3 LD₅₀) was 6.7 ± 1.5 days. When compared to WR(L) at a

challenge dose of 5 LD₅₀, wherein MST is 4.8 ± 0.6 days, the MST of ALVAC challenged mice was significantly longer (P=0.001).

Relative to NYVAC, Wyeth was found to be over 15,000 times more virulent; VC-2, greater than 35,000 times more virulent; and WR(L), over 3,000,000 times more virulent. Similar to ALVAC, the two highest doses of NYVAC, 6×10⁸ and 6×10⁷ PFUs, caused 100% mortality. However, the MST of mice challenged with the highest dose, corresponding to 380 LD₅₀, was only 2 days (9 deaths on day 2 and 1 on day 4). In contrast, all mice challenged with the highest dose of WR-L, equivalent to 500 LD₅₀, survived to day 4.

EXAMPLE 11 - EVALUATION OP NYVAC (vP866)

AND NYVAC-RG (vP879)

Immunoprecipitations. Preformed monolayers of avian or non-avian cells were inoculated with 10 pfu per cell of parental NYVAC (vP866) or NYVAC-RG (vP879) virus. The inoculation was performed in EMEM free of methionine and supplemented with 2% dialyzed fetal bovine serum. After a one hour incubation, the inoculum was removed and the medium replaced with EMEM (methionine free) containing 20 μCi/ml of ³⁵S-methionine. After an overnight incubation of approximately 16 hours, cells were lysed by the addition of Buffer A (1% Nonidet P-40, 10 mM Tris pH7.4, 150 mM NaCl, 1 mM EDTA, 0.01% sodium azide, 500 units per ml of aprotinin, and 0.02% phenyl methyl sulfonyl

fluoride). Immunoprecipitation was performed using a rabies glycoprotein specific monoclonal antibody

designated 24-3F10 supplied by Dr. C. Trinarchi, Griffith Laboratories, New York State Department of Health,

Albany, New York, and a rat anti-mouse conjugate obtained from Boehringer Mannheim Corporation (Cat. #605-500).

Protein A Sepharose CL-48 obtained from Pharmacia LKB Biotechnology Inc., Piscataway, New Jersey, was used as a support matrix. Immunoprecipitates were fractionated on 10% polyacrylamide gels according to the method of

Dreyfuss et. al. (a984). Gels were fixed, treated for fluorography with 1M Na-salicylate for one hour, and exposed to Kodak XAR-2 film to visualize the

immunoprecipitated protein species.

Sources of Animals. New Zealand White rabbits were obtained from Hare-Marland (Hewitt, New Jersey). Three week old male Swiss Webster outbred mice, timed pregnant female Swiss Webster outbred mice, and four week old Swiss Webster nude (nu⁺nu⁺) mice were obtained from

Taconic Farms, Inc. (Germantown, New York). All animals were maintained according to N1H guidelines. All animal protocols were approved by the institutional IACUC. When deemed necessary, mice which were obviously terminally ill were euthanized.

Evaluation of Lesions in Rabbits. Each of two rabbits was inoculated intradermally at multiple sites with 0.1 ml of PBS containing 10⁴, 10⁵, 10⁶, 10⁷, or 10⁸ pfu of each test virus or with PBS alone. The rabbits were observed daily from day 4 until lesion resolution. Indurations and ulcerations were measured and recorded.

Virus Recovery from Inoculation Sites. A single rabbit was inoculated intradermally at multiple sites of 0/1 ml of PBS containing 10⁶, 10⁷, or 10⁸ pfu of each test virus or with PBS alone. After 11 days, the rabbit was euthanized and skin biopsy specimens taken from each of the inoculation sites were aseptically prepared by mechanical disruption and indirect sonication for virus recovery. Infectious virus was assayed by plaque

titration on CEF monolayers.

Virulence in Mice. Groups of ten mice, or five in the nude mice experiment, were inoculated ip with one of several dilutions of virus in 0.5 ml of sterile PBS.

Reference is also made to Example 11.

Cyclophosphamide (CY) Treatment. Mice were injected by the ip route with 4 mg (0.02 ml) of CY (SIGMA) on day -2, followed by virus injection on day 0. On the

following days post infection, mice were injected ip with CY: 4 mg on day 1; 2 mg on days 4, 7 and 11; 3 mg on days 14, 18, 21, 25 and 28. Immunosuppression was indirectly monitored by enumerating white blood cells with a Coulter Counter on day 11. The average white blood cell count was 13,500 cells per μl for untreated mice (n=4) and 4,220 cells per μl for CY-treated control mice (n=5).

Calculation of LD₅₀. The lethal dose required to produce 50% mortality (LD₅₀) was determined by the

proportional method of Reed and Muench (Reed and Muench 1938).

Potency Testing of NYVAC-RG in Mice. Four to six week old mice were inoculated in the footpad with 50 to 100 μl of a range of dilutions (2.0 - 8.0 log₁₀ tissue culture infective dose 50% (TCID₅₀)) of either W-RG (Kieny et al., 1984), ALVAC-RG (Taylor et al., 1991b), or the NYVAC-RG. Each group consisted of eight mice. At 14 days post-vaccination, the mice were challenged by intracranial inoculation with 15 LD₅₀ of the rabies virus CVS strain (0.03 ml). On day 28, surviving mice were counted and protective does 50% (PD₅₀) calculated.

Derivation of NYVAC (vP866). The NYVAC strain of vaccinia virus was generated from VC-2, a plaque cloned isolate of the COPENHAGEN vaccine strain. To generate NYVAC from VC-2, eighteen vaccinia ORFs, including a number of viral functions associated with virulence, were precisely deleted in a series of sequential manipulations as described earlier in this disclosure. These deletions were constructed in a manner designed to prevent the appearance of novel unwanted open reading frames. FIG. 10 schematically depicts the ORFs deleted to generate NYVAC. At the top of FIG. 10 is depicted the HindIII restriction map of the vaccinia virus genome (VC-2 plaque isolate, COPENHAGEN strain). Expanded are the six regions of VC-2 that were sequentially deleted in the generation of NYVAC. The deletions were described earlier in this disclosure (Examples 1 through 6). Below such deletion locus is listed the ORFs which were deleted from that locus, along with the functions or homologies and molecular weight of their gene products.

Replication Studies of NYVAC and ALVAC on Human Tissue Cell Lines. In order to determine the level of replication of NYVAC strain of vaccinia virus (vP866) in cells of human origin, six cell lines were inoculated at an input multiplicity of 0.1 pfu per cell under liquid culture and incubated for 72 hours. The COPENHAGEN parental clone (VC-2) was inoculated in parallel.

Primary chick embryo fibroblast (CEF) cells (obtained from 10-11 day old embryonated eggs of SPF origin,

Spafas, Inc., Storrs, CT) were included to represent a permissive cell substrate for all viruses. Cultures were analyzed on the basis of two criteria: the occurrence of productive viral replication and expression of an

extrinsic antigen.

The replication potential of NYVAC in a number of human derived cells are shown in Table 16. Both VC-2 and NYVAC are capable of productive replication in CEF cells, although NYVAC with slightly reduced yields. VC-2 is also capable of productive replication in the six human derived cell lines tested with comparable yields except in the EBV transformed lymphoblastoid cell line JT-1 (human lymphoblastoid cell line transformed with Epstein-Barr virus, see Rickinson et al., 1984). In contrast, NYVAC is highly attenuated in its ability to productively replicate in any of the human derived cell lines tested. Small increases of infectious virus above residual virus levels were obtained from NYVAC-infected MRC-5 (ATCC #CCL171, human embryonic lung origin), DETROIT 532 (ATCC #CCL54, human foreskin, Downs Syndrome), HEL 299 (ATCC #CCL137, human embryonic lung cells) and HNK (human neonatal kidney cells, Whittiker Bioproducts, Inc.

Walkersville, MD, Cat #70-151) cells. Replication on these cell lines was significantly reduced when compared to virus yields obtained from NYVAC-infected CEF cells or with parental VC-2 (Table 16). It should be noted that the yields at 24 hours in CEF cells for both NYVAC and VC-2 is equivalent to the 72-hour yield. Allowing the human cell line cultures to incubate an additional 48 hours (another two viral growth cycles) may, therefore, have amplified the relative virus yield obtained.

Consistent with the low levels of virus yields obtained in the human-derived cell lines, MRC-5 and

DETROIT 532, detectable but reduced levels of NYVAC-specific DNA accumulation were noted. The level of DNA accumulation in the MRC-5 and DETROIT 532 NYVAC-infected cell lines relative to that observed in NYVAC-infected CEF cells paralleled the relative virus yields. NYVAC- specific viral DNA accumulation was not observed in any of the other human-derived cells.

An equivalent experiment was also performed using the avipox virus, ALVAC. The results of virus

replication are also shown in Table 16. No progeny virus was detectable in any of the human cell lines consistent with the host range restriction of canarypox virus to avian species. Also consistent with a lack of productive replication of ALVAC in these human-derived cells is the observation that no ALVAC-specific DNA accumulation was detectable in any of the human-derived cell lines.

Expression of Rabies Glycoprotein by NYVAC-RG

(vP879) in Human Cells. In order to determine whether efficient expression of a foreign gene could be obtained in the absence of significant levels of productive viral replication, the same cell lines were inoculated with the NYVAC recombinant expressing the rabies virus

glycoprotein (vP879, Example 7) in the presence of ³⁵S-methionine. Immunoprecipitation of the rabies

glycoprotein was performed from the radiolabelled culture lysate using a monoclonal antibody specific for the rabies glycoprotein. Immunoprecipitation of a 67kDa protein was detected consistent with a fully glycosylated form of the rabies glycoprotein. No serologically crossreactive product was detected in uninfected or parental NYVAC infected cell lysates. Equivalent results were obtained with all other human cells analyzed.

Inoculations on the Rabbit Skin. The induction and nature of skin lesions on rabbits following intradermal (id) inoculations has been previously used as a measure of pathogenicity of vaccinia virus strains (Buller et al., 1988; Child et al., 1990; Fenner, 1958, Flexner et al., 1987; Ghendon and Chernos 1964). Therefore, the nature of lesions associated with id inoculations with the vaccinia strains WR (ATCC #VR119 plaque purified on CV-1 cells, ATCC #CCL70, and a plaque isolate designated L variant, ATCC #VR2035 selected, as described in Panicali et al., 1981)), WYETH (ATCC #VR325 marketed as DRYVAC by Wyeth Laboratories, Marietta, PA), COPENHAGEN (VC-2), and NYVAC was evaluated by inoculation of two rabbits (A069 and A128). The two rabbits displayed different overall sensitivities to the viruses, with rabbit A128 displaying less severe reactions than rabbit A069. In rabbit A128, lesions were relatively small and resolved by 27 days post-inoculation. On rabbit A069, lesions were intense, especially for the WR inoculation sites, and resolved only after 49 days. Intensity of the lesions was also dependent on the location of the

inoculation sites relative to the lymph drainage network. In particular, all sites located above the backspine displayed more intense lesions and required longer times to resolve the lesions located on the flanks. All lesions were measured daily from day 4 to the

disappearance of the last lesion, and the means of maximum lesion size and days to resolution were

calculated (Table 17). No local reactions were observed from sites injected with the control PBS. Ulcerative lesions were observed at sites injected with WR, VC-2 and WYETH vaccinia virus strains. Significantly, no

induration or ulcerative lesions were observed at sites of inoculation with NYVAC.

Persistence of Infectious Virus at the Site of

Inoculation. To assess the relative persistence of these viruses at the site of inoculation, a rabbit was

inoculated intradermally at multiple sites with 0.1 ml PBS containing 10⁶, 10⁷ or 10⁸ pfu of VC-2, WR, WYETH or NYVAC. For each virus, the 10⁷ pfu dose was located above the backspine, flanked by the 10⁶ and 10⁸ doses. Sites of inoculation were observed daily for 11 days. WR elicited the most intense response, followed by VC-2 and WYETH (Table 18). Ulceration was first observed at day 9 for WR and WYETH and day 10 for VC-2. Sites inoculated with NYVAC or control PBS displayed no induration or

ulceration. At day 11 after inoculation, skin samples from the sites of inoculation were excised, mechanically disrupted, and virus was titrated on CEF cells. The results are shown in Table 18. In no case was more virus recovered at this timepoint than was administered.

Recovery of vaccinia strain, WR, was approximately 10⁶ pfu of virus at each site irrespective of amount of virus administered. Recovery of vaccinia strains WYETH and VC-2 was 10³ to 10⁴ pfu regardless of amount administered. No infectious virus was recovered from sites inoculated with NYVAC.

Inoculation of Genetically or Chemically Immune Deficient Mice. Intraperitoneal inoculation of high doses of NYVAC (5 X 10⁸ pfu) or ALVAC (10⁹ pfu) into nude mice caused no deaths, no lesions, and no apparent disease through the 100 day observation period. In contrast, mice inoculated with WR (10³ to 10⁴ pfu), WYETH (5 × 10⁷ or 5 × 10⁸ pfu) or VC-2 (10⁴ to 10⁹ pfu)

displayed disseminated lesions typical of poxviruses first on the toes, then on the tail, followed by severe orchitis in some animals. In mice infected with WR or WYETH, the appearance of disseminated lesions generally led to eventual death, whereas most mice infected with VC-2 eventually recovered. Calculated LD₅₀ values are given in Table 19.

In particular, mice inoculated with VC-2 began to display lesions on their toes (red papules) and 1 to 2 days later on the tail. These lesions occurred between 11 and 13 days post-inoculation (pi) in mice given the highest doses (10⁹, 10⁸, 10⁷ and 10⁶ pfu), on day 16 pi in mice given 10⁵ pfu and on day 21 pi in mice given 10⁴ pfu. No lesions were observed in mice inoculated with 10³ and 10² pfu during the 100 day observation period. Orchitis was noticed on day 23 pi in mice given 10⁹ and 10⁸ pfu, and approximately 7 days later in the other groups (10⁷ to 10⁴ pfu). Orchitis was especially intense in the 10⁹ and 10⁸ pfu groups and, although receding, was observed until the end of the 100 day observation period. Some pox-like lesions were noticed on the skin of a few mice, occurring around 30-35 days pi. Most pox lesions healed normally between 60-90 days pi. Only one mouse died in the group inoculated with 10⁹ pfu (Day 34 pi) and one mouse died in the group inoculated with 10⁸ pfu (Day 94 pi). No other deaths were observed in the VC-2

inoculated mice.

Mice inoculated with 10⁴ pfu of the WR strain of vaccinia started to display pox lesions on Day 17 pi. These lesions appeared identical to the lesions displayed by the VC-2 injected mice (swollen toes, tail). Mice inoculated with 10³ pfu of the WR strain did not develop lesions until 34 days pi. Orchitis was noticed only in the mice inoculated with the highest dose of WR (10⁴ pfu). During the latter stages of the observation period, lesions appeared around the mouth and the mice stopped eating. All mice inoculated with 10⁴ pfu of WR died or were euthanized when deemed necessary between 21 days and 31 days pi. Four out of the 5 mice injected with 10³ pfu of WR died or were euthanized when deemed necessary between 35 days and 57 days pi. No deaths were observed in mice inoculated with lower doses of WR (1 to 100 pfu).

Mice inoculated with the WYETH strain of vaccinia virus at higher doses 5 × 10⁷ and 5 × 10⁸ pfu) showed lesions on toes and tails, developed orchitis, and died. Mice injected with 5 × 10⁶ pfu or less of WYETH showed no signs of disease or lesions.

As shown in Table 19, CY-treated mice provided a more sensitive model for assaying poxvirus virulence than did nude mice. LD₅₀ values for the WR, WYETH, and VC-2 vaccinia virus strains were significantly lower in this model system than in the nude mouse model. Additionally, lesions developed in mice injected with WYETH, WR and VC-2 vaccinia viruses, as noted below, with higher doses of each virus resulting in more rapid formation of lesions. As was seen with nude mice, CY-treated mice injected with NYVAC or ALVAC did not develop lesions. However, unlike nude mice, some deaths were observed in CY-treated mice challenged with NYVAC or ALVAC, regardless of the dose. These random incidences are suspect as to the cause of death.

Mice injected with all doses of WYETH (9.5 × 10⁴ to 9.5 × 10⁸ pfu) displayed pox lesions on their tail and/or on their toes between 7 and 15 days pi. In addition, the tails and toes were swollen. Evolution of lesions on the tail was typical of pox lesions with formation of a papule, ulceration and finally formation of a scab. Mice inoculated with all doses of VC-2 (1.65 × 10⁵ to 1.65 × 10⁹) also developed pox lesions on their tails and/or their toes analogous to those of WYETH injected mice. These lesions were observed between 7-12 days post inoculation. No lesions were observed on mice injected with lower doses of WR virus, although deaths occurred in these groups.

Potency Testing of NYVAC-RG. In order to determine that attenuation of the COPENHAGEN strain of vaccinia virus had been effected without significantly altering the ability of the resulting NYVAC strain to be a useful vector, comparative potency tests were performed. In order to monitor the immunogenic potential of the vector during the sequential genetic manipulations performed to attenuate the virus, a rabiesvirus glycoprotein was used as a reporter extrinsic antigen. The protective efficacy of the vectors expressing the rabies glycoprotein gene was evaluated in the standard N1H mouse potency test for rabies (Seligmann, 1973). Table 20 demonstrates that the PD₅₀ values obtained with the highly attenuated NYVAC vector are identical to those obtained using a

COPENHAGEN-based recombinant containing the rabies glycoprotein gene in the tk locus (Kieny et al., 1984) and similar to PD₅₀ values obtained with ALVAC-RG, a canarypox based vector restricted to replication to avian species. Observations. NYVAC, deleted of known virulence genes and having restricted in vitro growth

characteristics, was analyzed in animal model systems to assess its attenuation characteristics. These studies were performed in comparison with the neurovirulent vaccinia virus laboratory strain, WR, two vaccinia virus vaccine strains, WYETH (New York City Board of Health) and COPENHAGEN (VC-2), as well as with a canarypox virus strain, ALVAC (See also Example 11). Together, these viruses provided a spectrum of relative pathogenic potentials in the mouse challenge model and the rabbit skin model, with WR being the most virulent strain, WYETH and COPENHAGEN (VC-2) providing previously utilized attenuated vaccine strains with documented

characteristics, and ALVAC providing an example of a poxvirus whose replication is restricted to avian

species. Results from these in vivo analyses clearly demonstrate the highly attenuated properties of NYVAC relative to the vaccinia virus strains, WR, WYETH and COPENHAGEN (VC-2) (Tables 14-20). Significantly, the LD₅₀ values for NYVAC were comparable to those observed with the avian host restricted avipoxvirus, ALVAC. Deaths due to NYVAC, as well as ALVAC, were observed only when extremely high doses of virus were administered via the intracranial route (Example 11, Tables 14, 15, 19). It has not yet been established whether these deaths were due to nonspecific consequences of inoculation of a high protein mass. Results from analyses in immunocompromised mouse models (nude and CY-treated) also demonstrate the relatively high attenuation characteristics of NYVAC, as compared to WR, WYETH and COPENHAGEN strains (Tables 17 and 18). Significantly, no evidence of disseminated vaccinia infection or vaccinial disease was observed in NYVAC-inoculated animals or ALVAC-inoculated animals over the observation period. The deletion of multiple

virulence-associated genes in NYVAC shows a synergistic effect with respect to pathogenicity. Another measure of the inocuity of NYVAC was provided by the intradermal administration on rabbit skin (Tables 17 and 18).

Considering the results with ALVAC, a virus unable to replicate in nonavian species, the ability to replicate at the site of inoculation is not the sole correlate with reactivity, since intradermal inoculation of ALVAC caused areas of induration in a dose dependent manner.

Therefore, it is likely that factors other than the replicative capacity of the virus contribute to the formation of the lesions. Deletion of specific

virulence-associated genes in NYVAC prevents lesion occurrence.

Together, the results in this Example and in

foregoing Examples, including Example 10, demonstrate the highly attenuated nature of NYVAC relative to WR, and the previously utilized vaccinia virus vaccine strains, WYETH and COPENHAGEN. In fact, the pathogenic profile of

NYVAC, in the animal model systems tested, was similar to that of ALVAC, a poxvirus known to productively replicate only in avian species. The apparently restricted

capacity of NYVAC to productively replicate on cells derived from humans (Table 16) and other species,

including the mouse, swine, dog and horse, provides a considerable barrier that limits or prevents potential transmission to unvaccinated contacts or to the general environment in addition to providing a vector with reduced probability of dissemination within the

vaccinated individual.

Significantly, NYVAC-based vaccine candidates have been shown to be efficacious. NYVAC recombinants

expressing foreign gene products from a number of

pathogens have elicited immunological responses towards the foreign gene products in several animal species, including primates. In particular, a NYVAC-based

recombinant expressing the rabies glycoprotein was able to protect mice against a lethal rabies challenge. The potency of the NYVAC-based rabies glycoprotein recombinant was comparable to the PD₅₀ value for a

COPENHAGEN-based recombinant containing the rabies glycoprotein in the tk locus (Table 20). NYVAC-based recombinants have also been shown to elicit measles virus neutralizing antibodies in rabbits and protection against pseudorabies virus and Japanese encephalitis virus challenge in swine. The highly attenuated NYVAC strain confers safety advantages with human, animal, medical and veterinary applications (Tartaglia et al., 1992).

Furthermore, the use of NYVAC as a general laboratory expression vector system may greatly reduce the

biological hazards associated with using vaccinia virus.

By the following criteria, the results of this

Example and the Examples herein, including Example 10, show NYVAC to be highly attenuated: a) no detectable induration or ulceration at site of inoculation (rabbit skin); b) rapid clearance of infectious virus from intradermal site of inoculation (rabbit skin); c) absence of testicular inflammation (nude mice); d) greatly reduced virulence (intracranial challenge, both three-week old and newborn mice); e) greatly reduced

pathogenicity and failure to disseminate in

immunodeficient subjects (nude and cyclophosphamide treated mice); and f) dramatically reduced ability to replicate on a variety of human tissue culture cells.

Yet, in spite of being highly attenuated, NYVAC, as a vector, retains the ability to induce strong immune responses to extrinsic antigens.

EXAMPLE 12 - GENERATION OF A NYVAC

RECOMBINANT EXPRESSING HTLV-I ENV

NYVAC and ALVAC HTLV-I envelope recombinant vaccines were constructed using plasmid DNA from the HTLV-I₁₇₁₁ molecular clone obtained from a culture of primary cells of a West African patient (Cardoso, 1989).

Phylogenetically HTLV-I₁₇₁₁ belongs to the cosmopolitan family of HTLV-I (Gessain, 1992).

A donor plasmid containing the I3L-promoted human T-cell lymphotropic virus type I (HTLV-I) envelope gene was generated by the following procedure. A 100 bp PCR fragment, PCR-HTLV 18, containing the I3L promoter fused to the 5'-end of the HTLV-I envelope gene, was generated from the plasmid, pMM102, with the oligonucleotide primers, MW093 (SEQ ID NO: 37; 5'- ATCATCGGTACCACATCATGCAGTGGTTAAAC-3') and MW110 (SEQ ID NO:38; 5'-GGCGAGAAACTTACCCATGATTAAACCTAAATAATTG-3'). A 1,500 bp PCR fragment, pCR-HTLV21, containing the 3'-end of the I3L promoter fused to the entire HTLV-I envelope gene, was generated from the plasmid, pl7-SST (containing entire HTLV-I nucleotide sequence), with the

oligonucleotide primers, MW113 (SEQ ID NO: 39; 5'-CAATTATTTAGGTTTAATCATGGGTAAGTTTCTCGCC-3') and MW116 (SEQ ID NO:40; 5'-ATCATCTCTAGAATAAAAATTACAGGGATGACTCAGGG-3'). A 1,600 bp PCR fragment, PCR-HTLV24, containing the I3L-promoted envelope gene, was generated by using the PCR fragments, PCR-HTLV18 and PCR-HTLV21, as templates in a PCR reaction with the oligonucleotide primers, MW093 (SEQ ID NO:37) and MW116 (SEQ ID NO:40). The I3L-promoted envelope gene was then cloned into pBSK. This was accomplished in 3 steps. 1) The 13L promoter and the 5'-end of the envelope gene was cloned into pBSK. This was accomplished by digesting the 1,600 bp PCR fragment, PCR-HTLV24, with KpnI and cloning the resulting 1,100 bp fragment into the KpnI site of pBSK. The plasmid

generated by this manipulation was called pMAW015. 2) The 3 '-end of the envelope gene was cloned into pBSK. This was accomplished by digesting the 1,600 bp PCR fragment, PCR-HTLV24, with KpnI and Xbal and cloning the resulting 530 bp fragment into the 2,900 by KpnI-XbaI fragment of pBSK. The plasmid generated by this

manipulation was called pMAW013. 3) The I3L promoter and the 5'-end of the envelope gene was then cloned upstream from the 3'-end of the envelope gene. This was accomplished by cloning the 1,100 bp KpnI fragment of pMAW015, containing the I3L promoter and the 5'-end of the envelope gene, into the KpnI site of pMAW013. The plasmid generated by this manipulation is called pMAW016.

The I3L-promoted envelope gene was then cloned between canarypox C5 flanking arms. This was

accomplished by cloning the 1,600 bp partial KpnI-XbaI fragment of pMAW16, containing the I3L-promoted envelope gene, into the 4,800 bp KpnI-XbaI fragment of pVQC5LSP6. The plasmid generated by this manipulation is called pMAW017.

pC5LSP was digested with BamHI and ligated to annealed oligonucleotides CP32 (SEQ ID NO:41) (5'-GATCTTAATTAATTAGTCATCAGGCAGGGCGAGAACGA

GACTATCTGCTCGTTAATTAATTAGGTCGACG-3') and CP33 (SEQ ID NO:42) (5'-GATCCGTCGACCTAATTAATTAACGAGCACATAGTCTCGTTCTCGCCCTGCCTGATGACTAATTAATTAA-3') to generate pVQC5LSP6.

pC5L was digested within the polylinker with Asp718 and NotI, treated with alkaline phosphatase and ligated to kinased and annealed oligonucleotides CP26 (SEQ ID NO: 43)

(5'- GTACGTGACTAATTAGCTATAAAAAGGATCCGGTACCCTCGAGTCTAGAATCGATCCCGGGTTTTTATGACTAGTTAATCAC -3') and CP27 (SEQ ID NO:44)

(5'- GGCCGTGATTAACTAGTCATAAAAACCCGGGATCGATTCTAGACTCGAGGGTACCGGATCCTTTTTATAGCTAATTAGTCAC -3') (containing a

disabled Asp718 site, translation stop codons in six reading frames, vaccinia early transcription termination signal (Yuen and Moss, 1987), BamHI, KpnI, XhoI, XbaI, Clal . and Smal restriction sites, vaccinia early

transcription termination signal, translation stop codons in six reading frames, and a disabled Notl site)

generating plasmid pC5LSP.

The C5L insertion plasmid was derived as follows. Using the cosmid vector pVK102 (Knauf and Nester, 1982), a genomic library for vCP65 (ALVAC-based rabies G

recombinant with rabies in C5 locus) was constructed. This library was probed with the 0.9 kb PvuII

canarypoxvirus genomic fragment contained within pRW764.5 (C5 locus). These canarypox DNA sequences contain the original insertion locus. A clone containing a 29 kb insert was grown up and designated pHCOS1. From this cosmid containing C5 sequences, a 3.3 kb Cla fragment was subcloned. Sequence analysis from this ClaI fragment was used to extend the map of the C5 locus from 1-1372.

The C5 insertion vector, pC5L, was constructed in two steps. The 1535 bp left arm was generated by PCR amplification using oligonucleotides C5A (SEQ ID NO: 45) (5'-ATCATCGAATTCTGAATGTTAAATGTTATACTTTG) and C5B (SEQ ID NO: 46) (GGGGGTACCTTTGAGAGTACCACTTCAG-3'). The template DNA was vCP65 genomic DNA. This fragment was cloned into EcoRI/Smal digested pUC8. The sequence was confirmed by standard sequencing protocols. The 404 bp right arm was generated by PCR amplification using oligonucleotides C5C (SEQ ID NO: 47) (5'-ATCATCCTGCAGGTATTCTAAACTAGGAATAGATG-3') and C5DA (SEQ ID NO: 48) (5'-ATCATCCTGCAGGTATTC

TAAACTAGGAATAGATG-3'). This fragment was then cloned into the vector previously generated containing the left arm digested with SmaI/PstI. The entire construct was confirmed by standard sequence analysis and designated pC5L. This insertion plasmid enables the insertion of foreign genes into the C5 locus.

The I3L-promoted envelope gene was then cloned between vaccinia HA flanking arms. This was accomplished by cloning the 1,600 bp partial KpnI-XbaI fragment of pMAW017, containing the I3L-promoted envelope gene, into the 3,600 bp KpnI-XbaI fragment of pSPHAH6. The plasmid generated by this manipulation is called pMAW018.

Plasmid pSPHAH6 was derived as follows. Plasmid pMP2VCL (containing a polylinker region within vaccinia sequences upstream of the K1L host range gene) was digested within the polylinker with HindIII and XhoI and ligated to annealed oligonucleotides SPHPRHA A through D

generating pSP126 containing a HindIII site, H6 promoter -124 through -1 (Perkus et al., 1989) and XhoI, KpnI, SmaI, SacI and EcoRI sites.

Plasmid pSD544 (containing vaccinia sequences surrounding the site of the HA gene replaced with a polylinker region and translation termination codons in six reading frames) was digested with XhoI within the polylinker, filled in with the Klenow fragment of DNA polymerase I and treated with alkaline phosphatase.

SP126 was digested with HindIII. treated with Klenow and the H6 promoter isolated by digestion with SmaI.

Ligation of the H6 promoter fragment to pSD544 generated pSPHAH6 which contained the H6 promoter in the polylinker region (in the direction of HA transcription). This insertion plasmid enables the replacement of the vaccinia HA gene (A56; Goebel et al., 1990a,b) with foreign genetic material.

pMAW018 was used in in vitro recombination

experiments with NYVAC as the rescuing virus to yield vP1181. EXAMPLE 13 - GENERATION OF A NYVAC

RECOMBINANT EXPRESSING HTLV-I ENV

pMAW017, obtained as described in Example 12, was used in in vitro recombination experiments with ALVAC as the rescuing virus to yield vCP203.

EXAMPLE 14 - ANALYSIS OF ALVAC AND NYVAC

RECOMBINANTS EXPRESSING ENTIRE HTLV,₁₁₇₁ ENVELOPE (gP 46, gp21.

The HTLV-I cell-associated challenge was prepared using a short-term coculture of human cord blood cells infected with HTLV-I_BOU, a West Indican isolate which also belongs to the cosmopolitan HTLV type (Gassain, 1992). Four rabbit pairs were inoculated with 8×10⁴, 4×10⁴, 2×10⁴ and 1×10⁴ HTLV-I_BOU-infected human cells by the intravenous (I.V.) route as indicated in Table 22. To ascertain the virological status after viral exposure of the inoculated animals, virus isolation was performed several times from purified peripheral blood mononuclear cells (PBMC) either by direct culture or by cocultivation with human cord blood cells.

As shown in Table 22, each pair of rabbits

inoculated with 8 or 4×10⁴ cells become infected after viral exposure. Only one of two animals were infected using 2×10⁴ cells whereas none of the rabbits were infected using 1×10⁴ as judged by virus isolation and polymerase chain reaction (PCR). Thus, a dose of 5×10⁴ cells was chosen to challenge the vaccinated animals.

Since only 30% of the HTLV-I_BOU-infected human cells used in the in vitro titration study were stained by a

monoclonal antibody against the HTLV-I p19 gag antigen in an immunofluorescence assay, the challenge does

correspond to approximately 1.5×10⁴ cells expressing virus.

Twelve animals were used in the ALVAC HTLV-I_env

(vcP203) trials (Table 21). Eight animals (groups 1 and 2) were immunized with two doses (10⁷ pfu) of recombinant ALVAC HTLV-I_env ("R-ALVAC") (vCP203) by the intramuscular (I.M.) route, 1 month apart. As a control the remaining four animals (group 3) received the non-recombinant ALVAC vector. The animals in group 1 also received two doses each of 100 μg of purified, baculovirus expressed (Arp, 1993) HTLV-I envelope precursor gp63 formulated in Alum at 4 and 5 months, respectively, following the initial inoculation (Table 21). Six months after the first inoculation all 12 animals were challenged with 5×10⁴ HTLV-I_BOU-infected cells by the I.V. route. Viral

infection was monitored by viral isolation from primary rabbit culture or by cocultivation with human cord blood cells, as well as by PCR analysis of rabbit PBMC DNA. The primers pair used for PCR was TIER: 5'

TATCCTTGCAGGACCATGCATC 3' (SEQ ID NO: 53) and tier:

AAGCAGGAAGAGCAGGAGCG 3' (SEQ ID NO: 54) which amplified the HTLV-I envelop gene fragment spanning nucleotides 6569 to 6921. Three of the four control animals

immunized with the non-recombinant ALVAC became infected. In group 1, which received the combination protocol consisting of priming with R-ALVAC (vCP203) and boosting with the gp46 subunit preparation, three of the four animals became infected as judged by virus isolation and PCR analysis. However, all four animals in group 2, which received only two doses of R-ALVAC (vCP203) at 0 and 28 days, were protected as judged by the inability to detect HTLV-I by virus isolation and PCR (Table 21).

Animal 34438 was PCR positive on one occasion, but virus was never isolated from its PBMC nor from its spleen (collected post-mortem).

These data indicated that immunization with R-ALVAC (vCP203) alone was sufficient to elicit a protective immune response in rabbits against a HTLV-I challenge exposure. Further, prime/boost protocol utilizing the R-ALVAC (vCP203) to prime HTLV-I-specific immune responses and a baculovirus gp63 subunit preparation as a booster inoculation did not serve to confer protection and, while not wishing to be necessarily bound by any one particular theory, this suggests that administration of the gp63 subunit preparation negated the protective efficacy of R-ALVAC (vCP203) observed in group 1. The serological analysis of the animals in this protocol (Fig. 12) was consistent with the virus isolation and PCR data. In fact, seroconversion to HTLV-I was observed only in the infected animals in groups 1 and 3 (Fig. 12).

Detection of antibodies against HTLV-I in the sera of animals in the ALVAC env prime boost protocol is shown in Fig. 12. The upper portion of Fig. 12 represents the vaccination protocol for each animal group. The numbers represent the time (months) of each inoculation. The Western blot was performed using strips from Cellular Products (Buffalo, NY) and the sera from the immunized animals are as follows: A, 1 week after the first ALVAC boost; B, after the second protein boost; C, at time of challenge; and D, 4 months after live virus challenge.

To explore the potential of the NYVAC HTLV-I_env

(vP1181), four animals were immunized with two I.M.

administrations of 10⁷ pfu of R-NYVAC (vP1181) at 0 and 1 month. Four additional animals served as controls receiving the non-recombinant NYVAC vector under the same dosing schedule. All rabbits were challenged 1 month following the second immunization. Virus isolation and PCR analysis following challenge exposure to 5×10⁴ HTLV-I_BOU-infected cells, revealed that all the vaccinated animals were protected again the cell-associated viral challenge, whereas all the controls became infected. As expected, only the control animals seroconverted against viral antigen (Fig. 13). Thus, the NYVAC recombinant elicited an immune response sufficient to clear viral infection in the animal exposed to HTLV-I in a short-time after immunization (see Table 23 and Fig. 13).

Serological response in the NYVAC env vaccinated and challenged animals is shown in Fig. 13. The outline of the vaccination protocol is displayed at the top of Fig. 13. The numbers represent the time (months) of each inoculation. The sera tested in Western blot were obtained at the following times: A, before immunization; B, 1 weeks after the first boost; and C, 4 months after challenge.

As a means of evaluation the duration of immunity conferred by R-ALVAC and R-NYVAC (vCP203 and vP1181), all animals deemed protected following the initial challenge exposure were rechallenged 5 months following the first challenge with HTLV-I_BOU-infected cells. The second challenge consisted of 5 ml of heparinized blood from the 34549 HTLV-I_BOU-infected animal (see Table 21). Roughly 1 to 10% of rabbit PBMC are usually infected by HTLV-I, and assuming this range in the challenge blood, the challenge dose would be 1 to 2 logs higher than the first challenge dose. Rabbit blood was used as challenged rather than human cells infected with HTLV-I^BOU to avoid a readout of the experimental results due to an immune response directed against human cells. Four naive animals were used as controls. Viral isolation and PCR analysis revealed that all the vaccinated animals, as well as the control animals, became infected by this HTLV-I challenge exposure (Tables 21 and 23). Neutralizing antibodies were measured in all the ALVAC and NYVAC recombinants vaccinated animals, as well as in the controls using a syncytium inhibition assay with C91/PL and 8166 cells as previously described (Benson, 1994). A consistent pattern was observed inasmuch as neutralizing antibodies were not detectable in all animals before viral challenge and only the animals that became infected (as judged by virus isolation and PCR) developed detectable HTLV-I specific neutralizing antibodies.

These results support previous findings which demonstrated the ability of NYVAC and ALVAC-based

recombinants to effectively prime protective immune responses against retrovirus challenges (Tartaglia, 1992; Piccini, 1987, Tartaglia, 1993). For example, an ALVAC-based recombinant expressing the feline leukemia virus (FeLV) env and gag proteins was shown to protect cats from developing a persistent viremia following an

occasional FeLV challenge exposure (Tartaglia, 1993). Further, pilot studies using NYVAC and ALVAC-based HIV-2 recombinants in rhesus macaques have been shown to afford protection from infection by a live HIV-2 challenge

(Franchini) and, similarly, partial protection was observed in animals immunized with NYVAC and ALVAC-based HIV-1 recombinants following challenge with HIV-2

(Abimiku). These results are also in agreement with an earlier report (Shida, 1987) which demonstrated that a mildly attenuated recombinant vaccinia virus expressing the HTLV-I envelope gene could protect rabbits from challenge with live HTLV-I infected human cells. Thus, surprisingly the efficacy of the NYVAC and ALVAC HTLV recombinants is not affected by the more highly

attenuated and safer nature of the NYVAC and ALVAC poxvirus vectors employed in the HTLV recombinants.

The observation that boosting with recombinant gp63 resulted in a lack of protection in the rabbits is, without wishing to necessarily be bound by any one particular theory, possibly due to the recombinant gp63 protein being processed and presented in a manner quite different from that of the envelope protein expressed by the NYVAC and ALVAC poxvirus-infected cells. Another possibility, again, without wishing to be bound by why one particular theory, is that the immunosuppressive region within the transmembrane portion of the non-native recombinant gp63 immunogen might have exerted a strong negative effect on the anti-HTLV-I cell-mediated immune response induced by the NYVAC or ALVAC vectors. However, earlier studies with recombinant, non-native E. coli-derived ß-galactosidase (ß-gal) fusion proteins

containing either the amino- or carboxy-terminal halves of gp63, when immunized as a mixture, was protective in cynomologous monkey (Nakamura, 1987). Besides the species difference, the immunization protocol used 1-2 milligrams of recombinant protein in Complete Freud's adjuvant followed by boosts in Incomplete Freud's

adjuvant with different injection routes, including I.V. administration. Thus, the immunization regimen is not directly comparable. However, it is interesting to note that the immunization protocol with the E. coli-derived β-gal fusion proteins generated only minimal anti-HTLV-I and neutralizing antibody titers. This suggests, without wishing to necessarily be bound by any one particular theory, that strong antibody responses might not be necessary for protection from live HTLV-I-infected cell challenge.

As has been documented in various retroviral

immunization studies cited above and, without wishing to be necessarily bound by any one theory, as strongly supported here, a general trend discerned from all of these studies (both above-cited and herein), may be that protection from retroviral challenge can be observed in the presence of very low or no detectable virus-specific neutralizing activity at the time of challenge (Clark, 1991; Pedersen, 1986; Earl, 1986; Miyazawa, 1992; Issel, 1992); hence, sufficient for protection against

retroviruses is proper cellular priming of the immune system.

The fact that the initially protected rabbits failed to resist subsequent challenge with transfused blood from an infected rabbit is possibly due to the 10-100-fold greater infected cell load contained in the transfused challenge dose overwhelming the rabbits' capacity to fend off the infection. However, without necessarily wishing to be bound by any one theory, it is also possible that the HTLV-I may have become adapted to more efficient replication upon passage in rabbits; but this is merely an unproven theory with the greater infected cell load being a fact.

Nonetheless, the results presented here demonstrate the ability of the NYVAC and ALVAC-HTLV recombinants and products therefrom to be employed in the compositions and utilities aforementioned, for instance, immunological, antigenic or vaccine compositions, or for use in

preparing antigens or antibodies for assays, kits or tests, and, for example, as suitable for uses in vaccine or immunization strategies capable of preventing

infection by a cell associated retrovirus such as HTLV-I.

Having thus described in detail preferred embodiments of the present invention, it is to be understood that the invention defined by the appended claims is not to be limited by particular details set forth in the above description as many apparent variations thereof are possible without departing from the spirit or scope thereof.

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Claims (26)

WHAT IS CLAIMED IS:

1. A modified recombinant virus, said

modified recombinant virus having virus-encoded genetic functions inactivated therein so that the virus has attenuated virulence, yet retained efficacy; said virus further comprising exogenous DNA in a nonessential region of the virus genome, said exogenous DNA encoding at least one HTLV virus epitope.

2. The virus of claim 1 wherein said virus is a poxvirus.

3. The virus of claim 2 wherein the poxvirus is a vaccinia virus.

4. The virus of claim 3 wherein the genetic functions are inactivated by deleting at least one open reading frame.

5. The virus of claim 4 wherein the deleted genetic functions include a C7L-K1L open reading frame, or, a host range region.

6. The virus of claim 5 wherein at least one additional open reading frame is deleted; and, the additional open reading frame is selected from the group consisting of: J2R, B13R + B14R, A26L, A56R, and I4L.

7. The virus of claim 5 wherein at least one additional open reading frame is deleted; and, the additional open reading frame is selected from the group consisting of: a thymidine kinase gene, a hemorrhagic region, an A type inclusion body region, a hemagglutinin gene, and a large subunit, ribonucleotide reductase.

8. The virus of claim 6 wherein J2R, B13R + B14R, A26L, A56R, C7L - K1L and I4L are deleted from the virus.

9. The virus of claim 7 wherein a thymidine kinase gene, a hemorrhagic region, an A type inclusion body region, a hemagglutinin gene, a host range region, and a large subunit, ribonucleotide reductase are deleted from the virus.

10. The virus of claim 8 which is a NYVAC recombinant virus.

11. The virus of claim 9 which is a NYVAC recombinant virus.

12. The virus of claim 10 wherein the exogenous DNA codes for HTLV_env or HTLV₁₁₇₁.

13. The virus of claim 11 wherein the exogenous DNA codes HTLV_env or HTLV₁₁₇₁.

14. The virus of claim 12 is vP1181.

15. A modified recombinant avipox virus which is modified so that it has attenuated virulence in a host; and, which contains exogenous DNA in a nonessential region of the virus genome, said exogenous DNA encoding at least one HTLV virus epitope.

16. The virus of claim 15 wherein said virus is a canarypox virus.

17. The virus of claim 16 wherein the canarypox virus is a Rentschler vaccine strain which was attenuated through more than 200 serial passages on chick embryo fibroblasts, a master seed therefrom was subjected to four successive plaque purifications under agar, from which a plaque clone was amplified through five

additional passages.

18. The virus of claim 17 which is an ALVAC recombinant virus.

19. The virus of claim 16 wherein the exogenous DNA codes for HTLV_env or HTLV₁₁₇₁.

20. The virus of claim 17 wherein the exogenous DNA codes for HTLV_env or HTLV₁₁₇₁.

21. The virus of claim 20 which is vCP203.

22. A method for treating a patient in need of immunological treatment or of inducing an immunological response in an individual or animal comprising

administering to said patient or individual or animal a composition comprising a virus as claimed in any one of claims 1, 12, 14, 15, 17, 19 or 21 in admixture with a suitable carrier.

23. A composition for inducing an immunological response comprising a virus as claimed in any one of claims 1, 12, 14, 15, 17, 19 or 21 in

admixture with a suitable carrier.

24. A method for expressing a gene product in a cell cultured in vitro comprising introducing into the cell a virus as claimed in any one of claims 1, 12, 14, 15, 17, 19 or 21.

25. An HTLV virus antigen prepared from in vitro expression of a virus as claimed in any one of claims 1, 12, 14, 15, 17, 19 or 21.

26. An antibody elicited by in vivo expression of an antigen from a virus as claimed in any one of claims 1, 12, 14, 15, 17, 19 or 21 or, by administration of an HTLV associated antigen from in vitro expression of the virus.