WO2003082908A2

WO2003082908A2 - Use of the p17 protein of hiv in isolated form for the preparation of a medicament for administration to hiv seropositive patients, as well as pharmaceutical compositions comprising said protein

Info

Publication number: WO2003082908A2
Application number: PCT/EP2003/003177
Authority: WO
Inventors: Arnaldo Caruso
Original assignee: Medestea Internazionale S.R.L.
Priority date: 2002-03-29
Filing date: 2003-03-27
Publication date: 2003-10-09
Also published as: WO2003082908A3; AU2003219101A8; ITTO20020286A1; AU2003219101A1; ITTO20020286A0

Abstract

The invention relates to a medicament for booster antigen use in HIV seropositive patients which uses, as active ingredient, the p17 protein of HIV or variants thereof in isolated or DNA form, containing sequences encoding for p17 or its variants which, if administered alone or combined with anti-inflammatory cytokines and molecules or DNA encoding for anti-inflammatory cytokines, are able to evoke or increase the serum titre of the anti-HIV-p17 antibodies that are capable of neutralizing the immunostimulating activity of the viral protein.

Description

Use of the p!7 protein of HIV in isolated form for the preparation of a medicament for administration to HIV seropositive patients, as well as pharmaceutical compositions comprising said protein

The present invention relates to the use of the pl7 protein in isolated form, (that is, produced by purification or by a recombinant method) for the preparation of a medicament for administration to patients who are seropositive with respect to the human acquired immunodeficiency virus (HIV) .

AIDS comprises a group of clinical syndromes caused by the HIV retrovirus. HIV infects preferentially cells which express the CD4 antigen on their surfaces and hence T helper lymphocytes and macrophages, but also dendrite cells.

Infection by HIV can be blocked in vitro by means of antibodies produced from the serum of infected individuals.

Over the years, various HIV neutralizing antibodies have also been developed; for the most part, these react with the protein products of the env gene.

These protein products have been used as immunogens in various forms, for example, as glycoprotein extracts, recombinant proteins, and synthetic peptides.

The products of env have conventionally been considered to be the HIV proteins that are most immunogenic and most suitable for stimulating an immune response protective against HIV.

However, researchers have also turned their attention to the proteins encoded by other HIV genes, for example, the gag gene. As is known, the gag gene encodes for a precursor polyprotein having a molecular weight of about 55,000 (p55) which is cut by the protease of pol into the polypeptides p24, pl7 and pl5 which constitute the structural proteins of the virion core.

Some studies have indicated that the products of the gag gene may also be the target of a neutralizing immune response .

In particular, it has been described that the pl7 protein of HIV may be the target of antibodies neutralizing the replication of HIV (for example, Papsidero, L.D., M. Sheu, and F. . Ruscetti, 1989, J. Virol. 63:267-272. Naylor, P.H. , C.W. Naylor, M. Badamchian, S. ada, A.L. Goldstein, S.-S. Wang, D.-K. Sun, A.H Thornton, P.S. Sarin, 1987, Proc. Natl. Acad. Sci. USA 84:2951-2955. Kageyama, S., T. Katsumoto, K. Taniguchi, S.I. Ismail, T. Shi men, F. Sasa, M. Gao, S. Owatari, N. Wakamiya, H. Tsuchie, S. Ueda, K. Shiraki, T. Kurimura, 1996, Acta Virol. £0:195-200. Buratti, E., S.G. Tisminetzky, P. D'Agaro, F.E. Baralle, 1997, J. Virol. 71:2457-2462.). Various researchers have also found that high levels of anti-pl7 antibodies are correlated with slower progression of the disease (for example, Jiang, J.- D., F.-N. Chu, P.H. Naylor, J.E. Kirkley, J. Mandali, J.I. Fallace, P.S. Sarin, A.L. Goldstein, J.F. Holland, J.G. Bekesi, 1992, J. Acquir. Immune Defic. Syndr. 5:382-390. Janvier, B., F. Mallet, V. Cheynet, P. Dal bon, G. Fernet, J.M. Besnier, P. Choutet, A. Goudeau, B. Mandrand, F. Barin, 1993, J. Acquir. Immune Defic. Syndr. 6:898-903. Binley, J.M., P.J. lasse, Y. Cao, I. Jones, M. Markowitz, D.D. Ho, J.P. Moore, 1997, J. Virol. 71:2799-2809. Moreover, it has been documented that, in AIDS, the affinity of the anti-pl7 antibodies, and hence their neutralizing capacity, is considerably reduced during the progression of the disease (for example, Chargelegue, D., CM. Stanley, CM. O'Toole, B.T. Colvin, M.W. Steward, 1995, Clin. Exp. Immunol. 99:175- 181. Chargelegue, D., B.T. Colvin, CM. O'Toole, 1993, AIDS 7, Suppl. 2:S87-S90) .

US patent 5,185,147 presents some isolated polypeptide sequences based on the aminoterminal region of pl7 which are described as being able to evoke anti-pl7 antibodies which interact with the viral particle of HIV, modifying its infecting capacity in vitro. However, as is known from electron microscopy studies (for example, Andreassen, H., H. Bohr, J. Bohr, S. Brunak, T. Bugge, R.M.J. Cotterill, C Jacobsen, P. Kush, B. Lautrup, S.B. Petersen, T. Saemark, and K. Ulrich, 1990, J. Acquir. Immune Def. Syndr. 3_:615- 622) , the pl7 protein is located inside the viral particle and is not therefore available for interaction with anti-pl7 antibodies. The modification of the infecting capacity in vitro of the viral particle of HIV observed in this study is therefore attributable to an interaction not between the antibodies and the infecting viral particle but, probably, between the antibodies and the protein isolated from the context of the viral particle. This presupposes a biological activity of pl7 that has been secreted into the cell micro-environment or released as a result of cell lysis.

In fact, recent data show that pl7, produced in recombinant form and purified, can increase the lymphocyte proliferation induced by mitogenic stimuli and positively influence infection of PBMCs by HIV in vitro (De Francesco, M. , A. Caruso, F. Fallacara, A. Canaris, F. Dima, C Poiesi, S. Licenziati, M. Corulli, F. Martinelli, S. Fiorentini, and A. Turano, 1998, AIDS 12:245-252). The present invention illustrates the presence of pl7 released from cells infected with HIV into culture supernatant and relates to the capacity of recombinant pl7 to synergize with IL-2 in inducing the production of pro- inflammatory cytokines, specifically IFN-γ and TNF-α, by PBMCs (peripheral blood mononucleated cells) . Inoculation of the recombinant pi7 protein into mice has given rise to antibodies that are capable of inhibiting the pro- inflammatory activity of pl7. On the basis of the results obtained, it is therefore proposed to use the pl7 protein for the preparation of a medicament for administration to HIV-seropositive patients. This medicament has the effect of inducing the formation or increasing the serum titre of the anti-pl7 antibodies which can neutralize the immunostimulating activity which pl7, produced during viral infection in HIV seropositive patients, exerts at cell level .

To solve the problem of whether HIV pl7 is released by cells infected by the human retrovirus and is hence capable per se of exerting biological activity on human cell systems, the inventor has defined an immuno-enzymatic test for the capture and quantification of pl7 in liquid media.

In particular, as described in greater detail in the section relating to the examples, the quantification of pl7 in the supernatant of cultures of human lymphocytes infected with HIV-1 by the ELISA capture method has demonstrated the spontaneous release of the viral protein into the extracellular micro-environment by infected cells only 2-3 days after infection, in the absence of cytopathic or cytolytic effects. The concentration of pi7 released into the supernatant was equal to some tens of ng/ml and therefore perfectly compatible with the doses shown by the inventor to be biologically active. HIV pl7 in recombinant form was found to be capable of increasing the state of activation of the HIV target CD4⁺ lymphocytes. As described in the section relating to the examples, in cultures of PBMCs stimulated with PHA, pl7 brought about an increase in the percentage of CD4⁺ lymphocytes expressing the lymphocyte activation marker CD17 in comparison with cells stimulated with PHA alone. It is known from the literature that the cell-activation state has an enormous effect on the replicative capacity of HIV which is low when the cell is in a state of quiescence. During infection by HIV, high levels of activation of the immune system have been shown to be harmful since they favour an increase in the replication of the virus, as was observed during the vaccination of seropositive patients with booster antigens (Stanley, S.K., Ostrowsky, M.A., Justement, J.S., Gantt, K. , Hedayati, S., Mannix, M. , Roche, K. , Schartzentruber, D.J., Fox, C.H., Fauci, A.S., 1996, New Engl. J. Med. 334,1222-1230) . Moreover, as will be described in greater detail in the section relating to the examples, the inventor has also found that pl7 has the capacity to increase the production of pro-inflammatory cytokines with pro-HIV action, such as IFN-γ and TNF-α.

It is widely known that these pro-inflammatory cytokines exert an activity favouring the replication of HIV. In particular TNF-α induces the transcription of HIV-1 both in lymphocytes and in macrophages, by activating NF-κB (Osborn, L., Kunkel, S., Nabel, G.J., 1989, Proc. Natl. Acad. Sci . USA 86, 2336-2340) . TNF-α is therefore implicated in the pathogenesis of the viral infection and is also capable of acting by autocrinous stimulation mechanisms since macrophages infected by HIV-1 produce greater levels of TNF-α which in turn favour viral production (Poli, G., Fauci, A.S., 1992, AIDS Res Hum Retroviruses . 8, 191-197; Merrill, J.E., Koyanagi, Y., Chen, I.S., 1989, J. Virol. 63, 4404-4408) . Moreover, increases in the production of TNF-α lead to an activation of the immune system which favours the replication and/or reactivation of HIV (Lederman, M.M., Kalish, L.A., Asmuth, D., Fiebig, E., Mileno, M., Busch, M.P. ,2000, AIDS 14, 951-958). TNF-α also performs an important role in the depletion of the CD4⁺ lymphocytes which is observed during infection by HIV (Lazdins, J.K., Grell, M., Walker, M.R., Woods-Cook, K. , Scheurich, P., Pfizenmaier, K.,1997, J. Exp. Med. 185, 81-90) inducing apoptotic mechanisms (Finkel, ,T.H., Tudor-Williams, G., Banda, N.K., Cotton, M.F., Curiel, T., Monks, 0., Baba, T.W., Ruprecht, R.M., Kupfer, A., 1995, Nat. Med. 1, 129- 134) . Data obtained recently also supports the evidence that the persistent activation induced by high systemic levels of TNF-α during HAART is associated with therapeutic failure (Aukrust, P., Muller, F., Lien, E., Nordoy, I., Nina-Beate, L., Kvale, D., Espervik, T., Froland, S., 1999, J. Infect. Dis. 179, 74-82) . IFN-γ also performs an important role in the development of inflammatory responses and promotes the production of other molecules which act as inducers of the replication of HIV-1, for example, IL-6 (Zaitseva, M. , Lee, S., Lapham, C, Taffs, R., King, L., Romantseva, T., Manischewitz, J. Golding, H., 2000, Blood 96, 3109-3117) . IFN-γ belongs to a group of cytokines which have pleiotropic effects, thus contributing to the activation of the immune system. It has recently been shown that IFN-γ increases the expression of the co-receptors of HIV CXCR4 and CCR5 on the CD4⁺ lymphocytes after stimulation with bacterial antigens. These results suggest that the infections which are observed in seropositive patients may increase the viral load by modulation of the co-receptors of HIV mediated by pro-inflammatory cytokines (Juffermans, N.P., Paxton, W.A., Dekkers, P.E.P., Verbon, A., de Jonge, E., Speelman, p., van Deventer, S.J.H., van der Poll T., 2000, Blood 96, 2649-2654). In fact, the levels of IFN-γ were found to be extremely high in HIV seropositive patients in comparison with patients who were seronegative with respect to the human retrovirus (for example, Fuchs, D., A. Hausen, G. Reibnegger, et al., 1989, J. Acquir. Immune Defic. Syndr. 2:158-162), and the percentage of lymphocytes producing this cytokine was increased in patients infected by HIV (for example, Caruso, A., A. Canaris, S. Licenziati, A. Cantalamessa, S. Folghera, M.A. Lonati, G. De Panfilis, G. Garotta, A. Turano, 1995, J. Acquir. Immune Defic. Syndr. 1J: 462-470) .

The inventor therefore checked whether the inoculation of recombinant pl7 into Balb/c mice was able to evoke antibodies neutralizing the biological activity of pl7. As described in detail in the examples section, all of the mice immunized with the recombinant pl7 developed anti-pl7 antibodies with serum titres variable from 1:8,000 to 1:64,000. In all cases, the antibodies thus obtained were able to inhibit all of the biological activities exerted by the pl7 of the human cells.

On the basis of the results obtained, it appears that recombinant pl7 is suitable for use as an immunogen which can evoke the formation of antibodies neutralizing the biological activity of HIV pl7. If the recombinant pl7 is inoculated into HIV seropositive patients, it can act as a booster antigen in order to increase the serum titre and/or the affinity, and hence the neutralizing activity, of the anti-pl7 antibodies.

The inventor has found experimentally that the activity of pl7 lies in the amino-acid portion included between position 9 and position 22 of the HIV pl7 protein. The numbering used herein for the amino-acid residues of the sequence of pl7 is in accordance with that proposed in Ratner et al (1985), Nature 313:277. In fact, anti-pl7 monoclonal antibodies capable of interfering with the herein-described biological activities of the viral protein are directed towards the above-described amino-acid sequence, as demonstrated by "epitope mapping" tests (data not given) .

It has also been shown that this amino-acid sequence is not recognized by non-neutralizing anti-pl7 monoclonal antibodies (data not given) .

It has also been found by the inventor that variants of the pl7 protein that are characteristic of other strains of HIV have mutations which do not, however, significantly alter its recognition by antibodies neutralizing the biological activity of pl7 (data not given) .

Amongst these variants, the sequences of the pl7 of viral strains that are prevalent in Africa (clade C) are mentioned purely by way of illustration. The pl7 of viral strains that are prevalent in specific geographical areas enable antibodies with greater affinity with respect to the corresponding pl7 to be obtained and are therefore particularly suitable for use as booster antigens for use in these geographical areas .

On the basis of the sequence data contained in gene data banks (for example, GenBank) relating to the sequence of the pl7 of strains from different geographical areas, the inventor has thus obtained a series of pl7 proteins of different strains of HIV which have some amino-acid variations in the polypeptide sequence disposed between amino-acids 9 and 22, but which share the immunological property of reacting with neutralizing antibodies directed against the pl7 of the corresponding strain of HIV. The polypeptide sequences of the pi7 of strains of HIV coming from different geographical areas are represented by the general formula: NH₂-X¹-Gly-X²-X³-Leu-Asp-X⁴-Trp-Glu-X⁵- Ile-X⁶-Leu-Arg-COOH, in which X¹ is an amino-acid residue selected from Ser and Arg, X² is an amino-acid residue selected from Gly, Glu and Ser, X³ is an amino-acid residue selected from Glu, Lys, Asp and Arg, X⁴ is an amino-acid residue selected from Arg, Ala, Lys, Thr, Ser, Glu, Asp and Gin, X⁵ is an amino-acid residue selected from Lys, Arg and Ser, and X⁶ is an amino-acid residue selected from Arg and Gin.

All of the amino-acids identified in the present description are in the L configuration. The abbreviations used for the amino-acid residues are in accordance with the standard nomenclature.

Within this group the pl7 which has, between amino-acids 9- 22, the amino-acid sequence indicated below: NH₂-Ser-Gly- Gly-Glu-Leu-Asp-Arg-Trp-Glu-Lys-Ile-Arg-Leu-Arg-COOH, constitutes a preferred immunogenic form of the invention. This pl7 corresponds to that of the laboratory strain BH10 of HIV-1 which is representative of strains that are widespread in Europe and America (clade B) .

The various forms of recombinant pl7 have the capacity to evoke a neutralizing immune response when administered to a patient infected with the corresponding strain of HIV and are therefore suitable for use as booster antigens in medicament form.

Within the scope of the present description, the term "medicament" is intended to define a pharmaceutical composition comprising a recombinant HIV pl7 according to the invention, as active ingredient, and a pharmaceutically acceptable vehicle, this composition being able to induce an active immunity in a patient - for example a mammal, including a human being - to whom it is administered in an effective quantity that is capable of blocking the pro- inflammatory activity of the pl7 which is produced in the course of a natural infection (endogenous pi7) .

A second subject of the invention is therefore a medicament composition comprising a pl7 protein of the invention and a pharmaceutically acceptable vehicle. A composition of this type is also suitable for use as an inoculum for administration to a non-human mammal in order to give rise to antibodies which immunoreact with HIV, in particular, antibodies neutralizing the biological activities of HIV pl7.

When used in a medicament or inoculum composition, the composition of the invention may also contain further ingredients including, for example, an antigenic adjuvant, that is, a substance which can increase the efficacy or the immunogenicity of an antigen.

Since some of the adjuvants usable in animals are not usable in man, the adjuvants of the medicament may be the same or different .

Alum (aluminium hydroxide), Freund's incomplete adjuvant, ISCOM, RIBI, and the compound MF59 recently described by Graham B.S., et al (Ann. Int. Med. 1996 125: 270-279) are mentioned by way of example as adjuvants usable in a medicament .

The medicament of the present invention contains an effective quantity of HIV pl7. The effective quantity of p!7 per unitary dose depends on well-known criteria which relate, amongst other things, to the species to which the subject to be inoculated belongs, to the body weight of the subject to be inoculated, and to the preselected administration regime. The medicaments and the inocula typically contain quantities of pl7 variable from 10 to 1000 micrograms/kg for use in mammals of average size (goats, dogs, monkeys) and in man, and from about 10 micrograms to about 500 micrograms per dose inoculated into small animals (mice, rats, rabbits, hamsters) . These quantities are based on the weight of the unmodified pl7.

The inoculation of the HIV pl7 protein into an HIV seropositive patient could lead to potentially dangerous side effects due to the intrinsic pro-inflammatory activity of the unmodified molecule. The medicament containing pl7 could be administered by a subcutaneous local route or by a topical route with suitable vehicles (for example, liposomes) thus limiting the potential side effects which may arise in administration by deeper (intramuscular) or systemic (intravenous) routes. Alternatively, the medicament could be administered in association with anti- retroviral drugs (for example, HAART) to limit, for the brief period for which the pl7 is present in active form in the organism infected with HIV, the effects which a pro- inflammatory microenvironment may have on the reactivation of the replication of the human retrovirus.

The inventor has shown experimentally that IL-4, an anti- inflammatory cytokine, can inhibit the pro-inflammatory effects of pl7. As described in greater detail in the examples, the presence of IL-4 in cultures of PBMCs stimulated with IL-2 and P17 considerably reduced the secretion of IFN-γ and TNF-α in the supernatant. Corticosteroids perform an anti-inflammatory activity which has only recently been shown to be dependent on the transformation of the cytokine pattern of an individual from Th-1 (producing mainly IFN-γ and TNF-α) to Th-2 (producing mainly IL-4, (for example Franchimont, D., J. Galon, M. Gadina, R. Visconti, V.-J. Zhou, M. Aringer, D.M. Frucht, G.P. Chrousos, J.J. O'Shea, 2000, J. Immunol. 164:1768- 1774) . These substances have also been used in therapy in HIV seropositive patients in whom they were found to be capable of inhibiting cell apoptosis and thus bringing about an increase in the count of CD4⁺ lymphocytes in circulation (for example, Andrieu, J.M., W. Lu, R. Levy, 1995, J. Infect. Dis. 171:523-530) . Moreover, short-term treatments with corticosteroids in HIV seropositive patients reduced cell activation, as is shown by the reduction of the serum levels of neopterine and of the TNF-receptor 2 with which a significant reduction in plasmatic viraemia was also associated (for example, Kilby, J.M., P.B. Tabereauts, V. Mulanovich, G.M. Shaw, R.P. Bucy, M.S. Saag, 1997, AIDS Res. Hum. Retroviruses 13:1533-1537) .

The inventor has been able to demonstrate, as described in detail in the examples section, that the addition of dexamethasone to PBMC cultures stimulated with IL-2 and pl7 achieved the same anti-inflammatory effects as IL-4. In particular, the levels of IFN-γ and TNF-α in the supernatant were drastically reduced to concentrations of the glucocorticoid equal to 10^"7 M.

In the light of the results given, it is possible to formulate a medicament composed of pl7 as booster antigen and of a glucocorticoid as anti-inflammatory drug. The presence of the glucocorticoid is actually beneficial for the purposes of the use of the pl7 protein as a booster antigen for reinforcing and strengthening a specific and neutralizing antibody response. In fact, it is known from the literature that glucocorticoids greatly suppress the cell-mediated immune response, whereas the humoral (antibody) responses are actually increased (for example, Akdis, CA. , T. Blescken, M. Akdis, S.S. Alkan, CH. Heusser, K. Blaser, 1997, Eur. J. Immunol. 9:2351-2357) .

The following examples are provided for illustrative purposes and are not intended to limit the scope of the present invention in any way.

EXAMPLES

Example 1 : Production of recombinant p!7

The sequence encoding the pl7 protein of the isolated BH-10 of HIV-1 (amino-acids 1-132, Ratner, L., W. Haseltine, R. Patarca, K.J. Livak, B. Starcich, S.F. Josephs, E.R. Doran, J.A. Rafalski, E.A. Whitehorn, K. Baumeister, L. Ivanoff, S.R. Petteway, M.L. Pearson, J.A. Lautenberger, T.S. Papas, J. Ghrayeb, N.T. Chang, R.C Gallo, and F. Wong-Staal, 1985, Nature 313 :277-284) was amplified by PCR with the use of the following primers: pl7for 5'-CGT GGA TCC ATG GGT GCG AGA GCGT-3'; pl7rev 5'-CGT GGA TCC TCA GTA ATT TTG GCT-3⁷ and cloned in the Ba-riHI site of the plasmid pGEX-2T (Pharmacia, Uppsala, Sweden) which allowed fusion with the NH₂-terminal end of the enzyme glutathione S-transferase (GST) . The oligonucleotide sequences used were based on the HIVBHIO entry of the databank GenBank which corresponds to the complete genome of the isolated BH-10 of HIV-1. The correct gene sequence of the pl7 cloned was confirmed with the use of pGEX sequencing primers (Pharmacia) , an automatic DNA sequencer (ABI PRISM 310; Perkin Elmer, Foster City, CA) and the ABI PRISM Big Dye Terminator Cycle Sequencing Ready Reaction Kit with AmpliTaq DNA polymerase FS (Perkin Elmer) . The GST fusion proteins were expressed in Escherichia coli and purified with the use of Sepharose 4B glutathione pearls (Pharmacia) . The viral protein was cut by GST whilst it was still bound to glutathione-agarose pearls, as described in Gearing, D.P., N.A. Nicola, D. Metcalf, S. Foote, T.A. Willson, N.M. Gough, and R.L. Williams, 1989, BioTechnology 7:1157-1161.

The pl7 protein was further purified by FPLC in inverse phase, achieving a purity greater than 98%.

The absence of contamination by endotoxins in the preparation of recombinant HIV-1 pl7 (<0.1 units of endotoxins/ml) was confirmed by the test based on the Limulus amoebocytes (Whittaker Bioproducts, Inc., Walkersville, Maryland, United States of America) . The purified HIV-1 pl7 was also biotinylated with the use of AH- NHS-Biotin (SPA, Milan, Italy) in accordance with the producer' s instructions .

Example 2 : Culture of peripheral blood mononucleated cells (PBMCs)

The PBMCs were isolated, by Ficoll-Hypaque density gradient (Pharmacia) , from heparinized blood just collected from healthy patients. The cells were seeded in culture plates with 96 wells with U-shaped bases (Nunc, Roskild, Denmark) at a density of 10⁶ cells/ml and were cultivated for the number of days indicated at 37°C in RPMI-1640 medium (Sigma, St. Louis, MO) supplemented with 10% of human AB serum inactivated by heating (Sigma) , 100 U/ml penicillin, and 100 μg/ml streptomycin complete medium.

Example 3 : Quantification of the p!7 in the supernatant of PBMCs infected with HIV Before defining the biological activity of pl7 as a separate protein entity, it is necessary to demonstrate that the pl7 is actually released into the supernatant during the infection of human cells with HIV. The inventor has defined an immuno-enzymatic test for the capture of HIV pl7 in order to quantify the viral protein in the supernatant of the cell culture. The test consists in the binding of mouse anti-pl7 polyclonal antibodies to the bases of wells of plates with 96 wells at a concentration of 1 μg/well. This is achieved by the incubation, for 12 hours at ambient temperature, of plates containing, in each well, the antibodies, diluted in 200 μl of carbonate buffer at pH 8.0. After several washings with phosphate buffer saline (PBS) , respective quantities of recombinant pl7 increasing from 100 pg to 1 μg, diluted in PBS, were deposited in each well in order to produce a standard reference curve. PBS alone was used as background of the reaction. The supernatant drawn both from the cell cultures infected with HIV and from the non-infected cultures (negative control) was deposited in other wells. After incubation for 1 hour at 37°C and respective washings with PBS, an anti-pl7 monoclonal antibody, previously conjugated to biotin in accordance with widely standardized methods and with commercially available kits (for example, the biotinylation kit supplied by the firm Pierce, Rockford, Illinois, USA) , was added to each well. A further incubation for 1 hour at 37°c and washings with PBS were then performed prior to the addition of streptavidine marked with the enzyme peroxidase which constituted the detector system. Upon completion of the incubation, which was for 1 hour at 37°c, washings were performed prior to the addition of the reaction substrate, which permitted the development of the colour, which was quantified by spectrophotometry. The method showed a sensitivity equal to 100 pg/ml of HIV pl7 protein. The availability of an immuno-enzymatic test for quantifying the HIV pl7 enabled it to be established that PBMCs (5 x 10⁶) pre-stimulated with PHA (5 mg/ml) for 48 hours and then infected with an inoculation of HIV as by a standardized method (for the technical details, refer to: De Francesco, M.A., A. Caruso, F. Fallacara, A.D. Canaris, F. Dima, C Poiesi, S. Licenziati, M. Corulli, F. Martinelli, S. Fiorentini, A. Turano, 1998, AIDS 12:245-252) were able to release the pl7 into the supernatant of the cell culture. The viral protein was quantifiable in the supernatant as early as 2 days after infection and reached a maximum peak, with quantities of pl7 of about 12 ng/ml, 6 days after infection.

Example 4 : Effects of p!7 on the expression of the activation marker CD71 on PBMCs stimulated with PHA

In order to establish whether pl7 can influence the activation state of the CD4⁺ T lymphocytes, which is a fundamental requirement for more efficient replication of HIV-1, tests were performed to assess the expression of the activation marker CD71 at individual cell level by flow cytofluorometry. The PBMCs were put in culture and stimulated with phytohaemoagglutinin (PHA) at a concentration of 5 μg/ml for 24 hours in the absence and in the presence of pl7. In all of the cultures tested, the PHA induced the expression de novo of the marker CD71 in the CD4⁺ T lymphocytes after 24 hours of stimulation. The percentage of CD4⁺ cells activated (CD4⁺CD71⁺) varied from a minimum of 12% to a maximum of 25%. The addition of pl7 in different doses increased the percentage of CD4⁺ T lymphocytes activated (CD71⁺) . A maximum effect was found at pl7 concentrations of 50 ng/ml. At this concentration, the increase in the percentage of CD4⁺CD71⁺ cells in comparison with the cultures stimulated with PHA alone varied from 54% to 92%. Example 5 : effect of p!7 on the secretion of TNF-α and INF-Y by PBMCs stimulated with IL-2.

In order to asses whether pl7 can influence the production of some pro-inflammatory cytokines, that is, TNF-α and INF-γ, which are well known to create an environment more suitable for the replication of HIV-1, a series of tests was performed to measure the secretion of these cytokines by PBMCs in culture, stimulated with IL-2 in the absence and in the presence of pl7. Various doses of IL-2 of from 2.5 to 100 U/ml were tested.

In all of the patients analyzed, a dose of 20 U/ml led to a considerable induction of the secretion both of TNF-α and of INF-γ in the supernatant of the PBMC cultures. The addition of pl7 at various doses increased the production of these cytokines by the PBMCs treated with IL-2. The maximum increase was found at a pl7 concentration of 50 ng/ml, although pl7 was biologically active at low concentrations down to 5 ng/ml. At a pl7 concentration of 50 ng/ml, the increase was more pronounced for TNF-α (from 36 to more than 100%) than for INF-γ (from 29 to 50%) .

Example 6 : Immunization of Balb/c mice with purified recombinant p!7 and evaluation of the antibody response

Female Balb/c mice were sensitized with 100 μg of pl7 of Example 1 emulsified in Freund's complete adjuvant and subjected to boosters at 15-days intervals with 100 μg of protein in incomplete adjuvant. 3 days after booster No. 4, the mice were bled and the resulting serum was frozen at - 80°c.

The specificity of the polyclonal antibodies thus obtained was determined by ELISA and Western Blot. Briefly, 96-well polystyrene microtitration plates were coated with pl7 (0.25 μg/well) in carbonate buffer. After washing with PBS containing 0.05% of Tween-20 (v/v) , the sera were added to the pl7-coated wells. After incubation for 1 hour at 37°C and washing, the binding of the antibodies to pl7 was measured with the use of goat anti-mouse IgG antibodies conjugated to horse radish peroxidase (Dako, Glostrup, Denmark) , followed by the addition of o-phenylenediamine as substrate for the colorimetric reaction.

The reactivity of the antibodies with the natural pl7 was assessed by Western blot analysis with the use of commercial kits for the Western blot analysis of HIV-1 (Sanofi Diagnostic Pasteur, Marnes La Coquette, France) .

Example 7 : Tests on neutralization of p!7 of HIV-1

It was checked whether the anti-pl7 antibodies obtained in Example 5 could influence the biological activity of pl7.

The PBMCs were cultivated in triplicate in plates having 96 wells with U-shaped bases in complete medium with PHA (at a concentration of 5 μg/ml) in the presence or in the absence of purified recombinant pl7 at a concentration of 50 ng/ml. The inhibition of the activity which pl7 exerts on the expression of the activation marker CD71 on the surface of the CD4⁺ T lymphocytes was achieved by the addition of the anti-pl7 polyclonal antibodies at dilutions of between 1:50 and 1:10,000.

The PBMCs were also cultivated in triplicate in plates with 96 wells with U-shaped bases in complete medium with IL-2 (at a concentration of 20 U/ml) in the presence or in the absence of various concentrations of purified recombinant pl7 (between 2.5 and 100 ng/ml). The inhibition of the secretion of TNF-α and INF-γ was achieved by the addition of the anti-pl7 polyclonal antibodies at dilutions of between 1:50 and 1:10,000. 3 days after cell activation, the supernatant of the culture were collected and checked for the presence of TNF-α and INF-γ.

The antibodies obtained in Example 5 were able to block the effects of pl7 on the expression of the CD71 activation marker by CD4⁺ T lymphocyte cells. In fact, the addition of the serum of the mice immunized with the pl7 at a final dilution of 1:50 completely blocked the ability of the pl7 to increase the percentage of CD4⁺CD71⁺ cells, returning it to the levels observed when the cells were stimulated with PHA alone (data not shown) . Similarly, the PBMC cells stimulated with IL-2 and pl7 reduced the production of TNF-α and INF-γ to levels comparable with those obtained in cultures stimulated with IL-2 alone when the serum of the mice immunized with the pl7 was added to the cultures at a final dilution of 1:50, at the start of the stimulation with the mitogen (data not given) .

In the absence of pl7, the addition of the anti-pl7 polyclonal antibodies at the start of the stimulation with the mitogen did not interfere with the synthesis of the pro- inflammatory cytokines.

Example 8 : Effect of IL-4 on the pro-inflammatory activity of p!7

In view of the pro-inflammatory activity (Th-1) of pl7, it was desired to assess the ability of a conventional anti- inflammatory cytokine (Th-2) such as interleukin (IL-4) to interfere with the biological functions of the viral protein. The addition of IL-4 to cultures of PBMCs stimulated with IL-2 reduced both the production of INF-γ and that of TNF-α. The reduction in the secretion of INF-γ was between 62 and 83%, whereas the reduction in the secretion of TNF-α was between 68 and 84% (data not given) .

To check whether IL-4 was able to oppose the pro- inflammatory effects of pl7, the cytokine was added to PBMCs at the start of the culture, simultaneously with IL-2 and pl7.

After 72 hours in culture, the supernatant were collected and analyzed for the secretion of TNF-α and INF-γ.

In all of the tests performed, the results obtained showed that IL-4 was able to interfere with the ability of pl7 to induce an increase in the secretion of TNF-α and INF-γ by PBMCs stimulated with IL-2, with a reduction of close to or more than 100% in the quantity of the two cytokines in the supernatant .

Example 9 : Effect of dexamethasone on the pro-inflammatory activity of p!7

Various anti-inflammatory molecules act by inducing a change of the cytokine pattern from Th-1 to Th-2 and, amongst these is dexamethasone. It was therefore desired to assess whether the addition of dexamethasone to PBMCs stimulated with IL-2 in the presence of pl7 could have the same effect on the production of the pro-inflammatory cytokines INF-γ and TNF-α as was observed with IL- .

The addition of dexamethasone at concentrations equal to 10^~7 M to PBMC cultures stimulated with IL-2 reduced both the production of INF-γ and that of TNF-α. The reduction in the secretion of INF-γ was between 76 and 94%, whereas the reduction in the secretion of TNF-α was between 88% and 100% (data not given) .

In order to check whether dexamethasone was able to oppose the pro-inflammatory effects of pl7, the glucocorticoid was added to PBMCs subsequently stimulated with IL-2 and pl7.

After 72 hours in culture, the supernatant s were collected and analyzed for the secretion of TNF-α and INF-γ.

In all of the tests performed, the results obtained showed that dexamethasone was able to interfere with the ability of pl7 to induce an increase in the secretion of TNF-α and INF-Y by the PBMCs stimulated with IL-2, with a reduction which varied from 88 to 100% and from 77 to 89%, respectively, in the quantity of the two cytokines in the supernatant .

Claims

1. A medicament comprising, as active component, the pl7 protein of HIV in isolated form and, optionally, one or more synthetic peptides derived therefrom, the pl7 protein being able to generate or reinforce an immune response neutralizing the immunostimulating activity which the pl7 protein of HIV exerts on human cells.

2. A medicament according to Claim 1, in which the sequence comprised between amino-acids 9-22 (the functional epitope) of the pl7 protein is NH₂-X¹-Gly-X²-X³-Leu-Asp-X-Trp-Glu-X⁵- Ile-X⁶-

Leu-Arg-COOH, where X¹ is an amino-acid residue selected from Ser and Arg, X² is an amino-acid residue selected from Gly, Glu and Ser, X³ is an amino-acid residue selected from Glu, Lys, Asp and Arg, X⁴ is an amino-acid residue selected from Arg, Ala, Lys, Thr, Ser, Glu, Asp and Gin, X⁵ is an amino- acid residue selected from Lys, Arg and Ser, and X⁶ is an amino-acid residue selected from Arg and Gin.

3. A medicament according to Claim 2 in which the amino-acid sequence is NH₂-Ser-Gly-Gly-Glu-Leu-Asp-Arg-Trp-Glu-Lys-Ile- Arg-Leu-Arg-COOH.

4. A medicament according to any one of Claims 1 to 3 , comprising, as active component, the pl7 protein of HIV in combination with one or more synthetic peptides derived therefrom having an amino-acid sequence corresponding to amino-acids 9 to 22 of the pl7 protein of HIV as defined in Claim 2 or Claim 3.

5. A medicament according to Claim 4 in which the one or more peptides are conjugated to a carrier and/or are in the form of branched peptides.

6. A medicament according to any one of Claims 1 to 5 in which the pl7 protein is in inactivated form.

7. A medicament according to any one of Claims 1 to 6 , further comprising a further component selected from recombinant anti-inflammatory cytokines and other anti- inflammatory molecules or parts thereof capable of maintaining and /or increasing the humoral response and at the same time of reducing the inflammatory response induced by the pi7 protein.

8. A medicament according to Claim 7 in which the recombinant cytokines are selected from the group which consists of IL-4, IL-10, IL-13, and combinations thereof.

9. A medicament according to Claim 7 or Claim 8 in which the anti-inflammatory molecules are selected from dexamethasone, betamethasone, prednisone, prednisolone, and combinations thereof .

10. A medicament comprising, as active component, a DNA molecule comprising the DNA sequence encoding for the pl7 protein of HIV or mutants thereof, inserted in an expression vecto .

11. A medicament according to Claim 10 in which the pl7 protein is as defined in Claim 2 or Claim 3.

12. A medicament according to Claim 10 or Claim 11, further comprising DNA molecules inserted in expression vectors encoding for anti-inflammatory cytokines or parts thereof which inhibit the inflammatory response induced by the viral pl7 protein.

13. A medicament according to any one of Claims 1 to 12 , further comprising a pharmaceutically acceptable vehicle.

14. A medicament according to Claim 13 in which the pharmaceutically acceptable vehicle contains an adjuvant capable of increasing the immune response.

15. A medicament according to Claim 14 in which the adjuvant is selected from ISCOM, RIBI, Freund's incomplete adjuvant, compound MF59, and mixtures thereof.

16. A medicament according to any one of Claims 13 to 15, further comprising delivery systems.

17. A medicament according to Claim 16 in which the delivery systems are selected from nanoparticles, herpetic vectors, erythrocytes, bacteria, and combinations thereof.

18. A medicament according to any one of Claims 13 to 17, further comprising inhibitors of viral replication.

19. A medicament according to any one of Claims 13 to 18 for use as a booster antigen or inoculum suitable for generating or reinforcing an immune response neutralizing the immunostimulating activity which the pl7 protein of HIV exerts on human cells .

20. Use of the pl7 protein of HIV for the preparation of a medicament suitable for generating or reinforcing an immune response neutralizing the immunostimulating activity which the pl7 protein of HIV exerts on human cells.

21. Use according to Claim 20 for the preparation of a medicament according to any one of Claims 1 to 12.

22. Use according to Claim 20 or Claim 21 for the preparation of a medicament for administration by a mucosal route .

23. Use according to Claim 20 or Claim 21 for the preparation of a medicament for administration by a nasal, oral, vaginal and/or rectal route.

24. Use according to Claim 20 or Claim 21 for the preparation of a medicament for administration by a systemic route or by a local route.

25. Use according to Claim 20 or Claim 21 for the preparation of a medicament for administration by an intramuscular, subcutaneous, or intradermal route.

26. Use according to Claim 20 or Claim 21 for the preparation of a medicament for administration by a cutaneous route .

27. Use according to Claim 20 or Claim 21 for the preparation of a medicament for administration by means of a pharmacologically acceptable liquid.

28. Use according to any one of Claims 20 to 27 for the preparation of a medicament further comprising a pharmacologically acceptable carrier and excipients which can optimize the activity of the active components .