EP2964239A1 - Use of attenuated parasite strains for the prevention and/or treatment of eye wounds associated with an infection by toxoplasma gondii - Google Patents

Abstract

The invention relates to strains of Toxoplasma gondii isolated from the natural medium thereof for the use of same in the prevention and/or treatment, in a mammal, of eye wounds associated with an infection by an apicomplexa of the Sarcocystidae family.

Description

 USE OF ATTENUATED STRAINS OF PARASITE FOR THE PREVENTION AND / OR TREATMENT OF OCULAR LESIONS ASSOCIATED WITH TOXOPLASMA GONDII INFECTION.

The present invention relates to the use of attenuated live parasite strains for the prevention and / or treatment of ocular lesions associated with Toxoplasma gondii infection, in mammals and in humans in particular.

Apicomplexes are obligate intracellular protozoan parasites that have a life cycle that can involve multiple hosts. The phylum of these parasites is subdivided into several families.

Toxoplasma gondii (T. gondii) belongs to the family Sarcocystidae. This protozoan exists in three infectious forms that vary according to the host and the infectious stage:

 tachyzoite: a proliferative and infectious form that multiplies asexually in the cells of the intermediate hosts (i.e. all the homeotherms) and the final ones (i.e. the felids and the cat in particular),

 o bradyzoite: a slow-dividing, low-level form of metabolism of the parasite contained in cysts,

 o the sporozoite: a form contained in oocysts, which results from the sexual multiplication of the parasite in the intestine of definitive hosts (i.e. cat and other felids).

The cat, the definitive host of the parasite, becomes infected by ingesting parasitized prey containing cysts (or tachyzoites if the prey is in the acute phase of toxoplasmosis (Dubey, 2002, J. Parasitol, 88: 713-717)), or by ingestion of oocysts. Infection of the cat leads to the formation, in its gut, of gametocytes whose fusion leads to the formation of oocysts which will then be disseminated in the environment via feces. These oocysts, which contain the sporozoites, sporulate and remain very long infectious in the external environment. Their pathogenic character persists for at least one year. After ingestion of oocysts by the definitive and intermediate hosts, the released sporozoites infect the enterocytes of the host and become tachyzoites that are disseminated in the body. Under the pressure of the immune system, the Tachyzoite is transformed into bradyzoite which persists in cysts with a preferential tropism for the central nervous system, retina and muscles.

Ingestion of encysted tissue is the second leading cause of contamination of final and intermediate hosts. After ingestion of cysts, the bradyzoites are released and infect the entero-epithelial cells and turn into tachyzoites, which disseminate in the host organism and, under the pressure of the immune system, will again form bradyzoites intra-cystic.

T. gondii strains are classified into three types (Howe et al, 1995, J.

Infect. Dis., 171: 1561-1566) according to their degree of virulence in vivo: Type I strains (i.e. strain RH) are highly virulent (Sibley et al, 1992,

Nature, 359: 82-5) while Type II strains (ie, strains ME49, 76K or

Prugniaud) and III (i.e., CEP or M7741 strains) are relatively less virulent and generally establish chronic infections (Howe et al., 1997, J. Clin.

Microbiol., 35: 1411-4). In addition, many atypical strains not related to the first three types are identified, particularly in Africa and

South America (Darde, 2008, Parasite, 15: 366-71, Rajendran et al, 2011, Infect.

Broom. Evol, 12: 359-68; Mercier et al, 2010, PLoS Negl. Too much. Dis., 4: e876, Ferreira et al., 2006, Infect. Broom. Evol., 6: 22-31).

Toxoplasma gondii causes an infectious disease: toxoplasmosis. Extremely widespread, with more than one-third of the world's population infected, the consequences of toxoplasmosis can be dramatic in two particular cases: (i) in HIV-negative pregnant women since the parasite can cross the placental barrier and infect the fetus thereby causing an abortion or severe malformations or severe psychomotor disturbances in the newborn and (ii) in immunocompromised persons such as HIV-infected persons in whom toxoplasmosis, an opportunistic parasitosis, can cause serious brain or heart disorders, lethal in the absence of treatment.

In immunocompetent persons, toxoplasmosis is usually benign. However, in recent years, many publications describe the impact of this infectious disease on the eye. The retina constitutes a preferential site of encystment of the parasite. Thus, toxoplasmosis is the most common cause of intraocular inflammation and posterior uveitis in individuals immunocompetent. These intraocular inflammations can cause a modification of the constituents of the ocular fluids (aqueous humor and vitreous humor) and thus alter the visual function. Toxoplasmosis is also responsible for retinochoroiditis most often related to the reactivation of parasites contained in retinal cysts, cysts may result:

 o either a congenital infection (i.e contracted in utero during pregnancy). Infection of the fetus in the first weeks of pregnancy leads to major ocular lesions (microphthalmia, cataract, extensive foci of retinochoroiditis). Ophthalmological monitoring of children infected with T. gondii in utero should be performed regularly during the first seven years of life of the child. Follow-up of functional signs {i.e. impaired vision, myodesopsia, scotoma) should immediately direct the practitioner towards a reactivation of T. gondii characterized by a multiplying phase of the parasite, o either of an acquired infection. Congenital infection is not the only etiology of ocular toxoplasmosis. Indeed, the role of infections of acquired origin has been demonstrated in many cases of ocular toxoplasmosis, especially in several members of the same siblings or when the prevalence is high in certain geographical areas. In ocular toxoplasmosis of acquired origin, ocular manifestations may be concomitant to primary infection or delayed, sometimes years or decades after primary infection.

The rate of reactivation of T. gondii resulting from an acquired infection is comparable to that resulting from a congenital infection and regardless of their etiological origin, the lesions generated on the retina may cause deterioration or loss of vision if they are close to the macula or optic nerve.

The prevalence and incidence of ocular toxoplasmosis is highly dependent on the geographical area. In France, where, as in Europe, Type II strains predominate, the prevalence of ocular toxoplasmosis in the population has not been assessed with certainty but the incidence of the disease would be 2% of infected patients and would therefore concern about 800,000 patients. In some parts of the world, especially in South America, where Type I T. gondii strains predominate {The. the most virulent), the incidence of ocular toxoplasmosis is significantly higher. For example, in the Erechim region, a city in southern Brazil, toxoplasmic retinochoroidal scars were found in 17.7% of the subjects examined and out of a total population of 2 million, 20,000 people lost their use of one eye and 5,000 people are totally blind (Jones et al, 2006, Emerg Infect Dis, 12: 582-587, Silveira et al., 2009, Expert Rev. Anti Infected Ther 7: 905-908).

The diagnosis of ocular toxoplasmosis is essentially clinical. When the lesions observed at the fundus are atypical, the serological analysis of the anti-7 ⁷ antibodies. gondii can be performed not only in the patient's serum, but also in the aqueous humor of the eye. Measurements of anti-T. gondii IgG levels and total IgG levels in these two compartments make it possible to determine the value of the Desmonts coefficient. This coefficient corresponds to the ratio IgG anti-T. gondii I total IgG in the aqueous humor on the ratio IgG anti-7 ⁷ . gondii I total IgG in the blood. When this ratio is greater than 3, it is estimated that there is a local synthesis of anti-7 ⁷ antibodies. gondii translating intraocular infection. When this ratio is less than 2, the local production of anti-7 ⁷ antibodies. gondii is not demonstrated, without ocular toxoplasmosis being eliminated. A value between 2 and 3 is doubtful for asserting local production of T. gondii antibodies. In the last two cases, the presence of the parasite in the aqueous humor can be detected by the amplification of T. gondii DNA by the Polymerase Chain Reaction technique.

Current treatments (Engstrom et al., 1991, Am. J. Ophthalmol., 111: 601-610) are based on the use of pyrimethamine or sulfadiazine. These antiparasitics or antibiotics, by inhibiting the metabolism of folic acid, block the synthesis of nucleic acids of the parasite. These compounds are active on tachyzoites, but are inactive on bradyzoites. Cotrimoxazole and clindamycin also act on tachyzoites. Azithromycin has an in vitro action on bradyzoites which is found to be weak in vivo on this parasitic form. Atovaquone has the best in vivo action potential on both tachyzoites and bradyzoites. These compounds must be used at high concentrations to cross the blood-eye barrier and reach sufficient levels in the retina. From this In fact, these drugs can have dramatic side effects (Lyell's syndrome, agranulocytosis, pseudo-membranous colitis) and require supplementation of the patient with folate. The use of these compounds may be associated with corticosteroid therapy. The goal of corticosteroids is to limit the inflammatory reaction associated with retinochoroiditis of toxoplasmic origin. Prednisone is the reference corticosteroid. Administration of corticosteroids, however, is reserved for immunocompetent patients.

Since these compounds do not have a kysticidal effect, they can not, therefore, prevent the reactivation of encysted T. gondii leading to recurrences of the disease, estimated at 15% at two years. They are, therefore, prescribed only when the visual function is threatened (macular or papillary involvement). The goal of the treatment is to activate the healing of existing lesions. Therapeutic treatments make it possible to limit the damage during a reactivation of the encysted parasite but in no way prevent subsequent reactivations. Long underestimated, ocular toxoplasmosis has serious consequences and this infection is now part of health watch programs established in France, Brazil, etc. The marketing of an effective toxoplasmosis vaccine, limiting by the subsequent dissemination of the parasite into ocular tissues and the clinical consequences of subsequent outbreaks is an interesting and promising strategy to limit the impact of this infectious disease (Silveira et al, 2009, Expert Rev. Anti-Infecti Ther 7: 905 -908).

There is therefore a real need for the development of an agent for preventing and / or treating ocular lesions in a mammal, in particular a mammal already infected with T. gondii or a mammal likely to be infected with T. gondii and to develop toxoplasmosis.

Recently, an attenuated live vaccine strain of T. gondii has been developed by the invalidation of two genes encoding the TgMIC1 and TgMIC3 proteins (EP 1 703 914 B1 and US 7,964,185 B2 / Cérède et al., 2005 J. Exp Med, 201: 453-63). This strain, called Toxo micl-3 KO, generates a strong and specific immune response against T. gondii and makes it possible to prevent the effects of a subsequent infection in mice (Ismaël et al, 2005, J. Infect Dis., 194 1176-1183) and also in ewes (Mevelec et al., 2010, Vet Res., 41: 49-60). It has also been shown that virulence in vivo is only minimally affected by isolated inactivation of TgMIC1 or TgMIC3; on the other hand, it is strongly diminished by the simultaneous inactivation of the two proteins, highlighting the synergistic role of the two proteins (Cérède et al., 2005 J. Exp. Med., 201: 453-63). One of the aims of the invention is to provide an agent for reducing, in the eye, in a mammal, the inflammation following a T. gondii infection.

 Another object of the invention is to reduce the inflammatory reaction occurring in the eye at the time of reactivation of T. gondii in a mammal already infected with T. gondii.

 Another object of the invention is to provide an agent for reducing the number of cysts, especially intra-retinal, thereby preventing eye lesions related to the reactivation of T. gondii.

 Yet another object of the invention is to provide a vaccine against ocular lesions caused by T. gondii.

The subject of the present invention is strains of Toxoplasma gondii isolated from their natural environment for use in the prevention and / or treatment, in a mammal, of ocular lesions associated with an apicomplex infection of the family Sarcocystidae.

The subject of the present invention is strains of Toxoplasma gondii isolated from their natural environment for use in the prevention and / or treatment, in a mammal, of ocular lesions associated with infection by an apicomplex of the family Sarcocystidae, said strains possessing attenuated virulence with respect to a virulent T.gondii RH strain.

The subject of the present invention is strains of Toxoplasma gondii isolated from their natural environment for use in the prevention or treatment, in a mammal, of ocular lesions associated with an apicomplex infection of the family Sarcocystidae, said strains having a attenuated virulence with respect to a virulent strain, i.e. a strain having a virulence substantially identical to the virulence of the strain from which the attenuated virulence strain was obtained. "Prevention" refers to prophylaxis aimed at preventing the onset or spread of a disease. These include protecting an individual predisposed to the contraction and development of ocular lesions associated with an apicomplex infection of the family Sarcocystidae. This includes protecting a mammal exposed to a risk of contamination by its environment.

By "treatment" is meant not only the inhibition of the progression of the pathology, but also the attenuation, or even the disappearance, of the symptoms related to this pathology. The aim of the treatment is to reduce the amplitude of the symptoms until their complete disappearance, allowing the individual to return to a normal physiological state.

"Mammal" refers to humans, pets and livestock or livestock, which are of economic and commercial value to the agri-food industries.

By "strains of Toxoplasma gondii" is meant strains of Toxoplasma gondii which have an attenuated virulence, less than the virulence of RH-type T.gondii strains from which they derive, but which nonetheless retain an immunogenic capacity identical to that of the strains. T. gondii type RH for use in the prevention or treatment of a pathology associated with an apicomplex infection of the Sarcocystidae family. This attenuated virulence can result from the invalidation of at least one gene linked to the virulence of the parasite. This gene invalidation can occur during a natural process of evolution of the species or be performed in vitro by molecular biology techniques well known to those skilled in the art. In the first case, the gene invalidation occurs at random in the genome whereas in the other case, the gene invalidation is targeted at one or more specific genes. Whether of natural origin or consecutive to the human hand, this gene invalidation results in the absence of expression of the protein encoded by the invalidated gene (s) or the expression of one or several non-functional proteins. The in vitro modification of the genetic heritage of Toxoplasma gondii confers on the strain a mutant character, as opposed to the wild strain from which it derives. Wild strains of parasites not only have an immunogenic potential but are also virulent, i.e. they are capable of inducing pathology associated with Toxoplasma gondii (ie toxoplasmosis), rendering their use unsuitable in the context of the present invention.

"Pathologies associated with apicomplex infection of the family Sarcocystidae" means diseases resulting from infection with a protozoan belonging to the phylum apicomplexes, and in particular parasites belonging to the family of sarcocystidae which includes the genus Toxoplasma.

According to a particular embodiment, in the use according to the present invention strains of Toxoplasma gondii isolated from their natural environment, said mammal is a human being or an animal. According to another embodiment, in the use according to the present invention strains of Toxoplasma gondii isolated from their natural environment, said strains of Toxoplasma gondii have at least one adhesin MIC-1 and / or an adhesin MIC-3 inactivated by a gene modification involving at least one of the mic-1 and / or mic-3 genes. According to another particular embodiment, in the use according to the present invention strains of Toxoplasma gondii isolated from their natural environment, said strains of Toxoplasma gondii have at least one adhesin MIC-1 and / or an adhesin MIC-3 inactivated by the deletion of at least one of the mic-1 and / or mic-3 genes.

By "a MIC-1 adhesin and / or an adhesin MIC-3" is meant the proteins of the micronemes, also called adhesins, MIC-1 and / or MIC-3, which play a role in mobility, migration or migration. cellular invasion of the phylum of the apicomplexes in its host. These proteins have binding modules that allow them to bind to host cells.

By "an inactivated adhesin" is meant an adhesin whose function can no longer be provided within the cell. An adhesin is inactivated when it is not produced or when it is produced but has no functional activity. The inactivation may also be the consequence of inoperative or insufficient post-translational modifications (ie glycosylation, isoprenylation, phosphorylation, sulfation, amidation, acetylation, alkylation) of the adhesin which do not allow it to perform its function. Inactivation of an adhesin can also be obtained indirectly by altering or suppressing the expression of one or several other proteins (including other adhesins) that bind to the adhesin to form a functional complex. The destructuring of such a complex causes a loss of function of the adhesin.

By "gene modification" is meant any mutation made in the nucleic sequence of a gene resulting in the absence of expression of the protein encoded by this gene or resulting in the expression of a non-functional form of the encoded protein. by this gene. This operation requires the intervention of the hand of a person skilled in the art when it is operated in vitro. This mutation may consist in the deletion of all or part of the gene, or its coding region, or its promoter region, in the insertion or substitution of nucleotides in the nucleotide sequence of the gene.

By "mic-1 gene" is meant the gene coding for the MIC-1 microneme protein, also called MIC-1 adhesin. This protein contains several modules including binding domains that specifically bind lactose. The MIC-1 protein is also able to bind to the surface of the host cells. By "mic-1 gene" is meant the gene encoding the micronemas protein

MIC-3, also called MIC-3 adhesin. This protein is homodimerized to form a complex of 90 kDa. MIC-3 has EGF-like domains and a lectin-like domain. The MIC-3 protein is also able to bind to the surface of the host cells. According to yet another embodiment, in the use according to the present invention strains of Toxoplasma gondii isolated from their natural environment, said strains of Toxoplasma gondii possess the two adhesins MIC-1 and MIC-3 inactivated by a gene modification involving the two genes mic-l and mic-3.

According to yet another particular embodiment, in the use according to the present invention strains of Toxoplasma gondii isolated from their natural environment, said strains of Toxoplasma gondii have both adhesins MIC-1 and MIC-3 inactivated by the deletion of both mic-1 and mic-3 genes.

By "gene modification on the two mic-1 and mic-3 genes" is meant the mutation made in the nucleic sequence of the mic-1 gene and that of the mic-3 gene. This double mutation results in the lack of expression of MIC-1 and MIC-3 proteins or results in the expression of a non-functional form of MIC-1 proteins. and MIC-3. This mutant strain of Toxoplasma gondii is called Toxo honey -3 KO and has a very attenuated virulence in comparison with the wild type T. gondii RH strains from which it derives. The Toxo micl-3 KO strains, however, retain a high immunogenicity. The detailed construction of the strain Toxo micl-3 KO is described in documents Cérède et al, 2005 J. Exp. Med., 201: 453-63, US 7, 946, 185 B2 and EP 1 703 914 B1.

Toxo micl-3 KO strains retained their ability to colonize the target tissues without the development of any pathogenic phenomenon following the administration of said strains to a mammal. Invalidation of the honey and mic3 genes in no way alters the immunogenic potential of these strains, but considerably reduces their virulence with respect to a virulent strain, that is to say a strain having a virulence substantially identical to virulence. of the strain from which the attenuated virulence strain was obtained.

According to another embodiment, in the use according to the present invention strains of Toxoplasma gondii isolated from their natural environment, said apicomplex of the Sarcocystidae family is Toxoplasma gondii.

"Toxoplasma gondii" refers to the protozoa of the phylum apicomplexes that can cause birth defects or miscarriages in most warm-blooded mammals and birds. These parasites are particularly capable of causing toxoplasmosis in humans, pigs, ewes, rodents or any mammal that has a mature or deficient immune system.

According to another embodiment, in the use according to the present invention strains of Toxoplasma gondii isolated from their natural environment, said ocular lesions belong to the group comprising or consisting of intra- ocular inflammations, uveites, hyalites or retinochoroïdits.

By "intraocular inflammations" is meant any secretion of cytokines and chemokines involved in the immune response and any recruitment or activation of the immune system cells contained in the eye. "Uveitis" means the inflammation of the uvea, a vascularized complex that feeds the eye and includes the iris, the ciliary body (anatomical element to which are connected the ligaments retaining the lens) and the choroid. This inflammation can be caused by a virus, a bacterium or a parasite or be due to an autoimmune disease. Uveitis can be anterior, intermediate or posterior depending on the compartments of the eye it affects. Uveitis can be painful or not and is associated with a decrease in visual acuity. The eye may appear red with, for example, watery eyes or photophobia.

By "hyalites" is meant inflammation of the vitreous of the eye which corresponds to an intermediate uveitis.

By "retinochoroidites" are meant clinical entities that include any lesion of the retina-choroid complex. Always inflammatory, they can be of infectious or autoimmune origin. Retinochoroiditis therefore corresponds to an inflammation of the posterior uveae, that is to say of the retina and the choroid.

According to a more particular embodiment, in the use according to the present invention strains of Toxoplasma gondii isolated from their natural environment, said ocular lesions are consecutive to a primary infection of said mammal by T. gondii.

By "primary infection" is meant the first contact of said mammal with the parasite T. gondii. This primary infection leads to an immune response characterized in particular by the production of anti-Γ antibodies. gondii and by the activation of a cellular immune response directed specifically against T. gondii.

According to an even more particular embodiment, in the use according to the present invention strains of Toxoplasma gondii isolated from their natural environment, said ocular lesions are consecutive to a reactivation of the asexual form of T. gondii.

By "reactivation of the asexual form of T. gondii" is meant the conversion of T. gondii bradyzoites to tachyzoites and the release of these after cyst disruption, thereby inducing cell contamination. The reactivation of T. gondii may be due to a deficiency of the immune system of the infected mammal. According to a still more particular embodiment, in the use according to the present invention strains of Toxoplasma gondii isolated from their natural environment, said ocular lesions are consecutive to a primary infection of said mammal by T. gondii and reactivation of the asexual form of T. gondii. According to a particular embodiment, in the use according to the present invention strains of Toxoplasma gondii isolated from their natural environment, said strains are contacted with said mammal at a rate of 100 to 10 ⁸ tachyzoites.

By "tachyzoite" is meant the rapid and asexual form of replication of Toxoplasma gondii. The tachyzoite has a size of 5-8 x 2-3μιη. The apical portion of the parasite has conoids that participate in parasite entry into the host cell. Micronemas, rhoptries and dense granules are the three main organelles of the tachyzoite, which also contains a nucleus, an apicoplast, a Golgi apparatus, an endoplasmic reticulum and an organelle close to the mitochondria. The effective dose of tachyzoites for the prophylactic treatment of mammals limits the infection or transmission of the pathogen responsible for toxoplasmosis. Another goal is to prevent the appearance of new intraocular lesions during reactivation of the encysted parasite. Such a treatment can be adapted and / or repeated as many times as necessary by those skilled in the art, depending on the age and the immunological status of the mammal.

Contacting the tachyzoites with the mammal is feasible not only for a mammal exhibiting the symptoms inherent to toxoplasmosis, but also for a mammal with none of these symptoms but which presents a risk of infection with virulent strains of Toxoplasma gondii likely to induce toxoplasmosis and therefore these symptoms.

According to a particular embodiment, the strains of Toxoplasma gondii isolated from their natural environment for their use according to the present invention are in a dosage form chosen from the group comprising or consisting of liquid suspensions, solid or liquid dispersions, powders , pasta or lyophilisais. The dosage form is adapted by those skilled in the art depending on the mode of administration chosen. All the conventional modes of administration can be envisaged: enterally (per os for example) parenterally (intravenous, intramuscular or intraperitoneal injection for example) or by intra-nasal spraying.

According to a more particular embodiment, strains of Toxoplasma gondii isolated from their natural environment for their use according to the present invention may be associated with at least one other antigen, at least one adjuvant, at least one stabilizer, at least one preservative at least one vector or a mixture of these products for stimulating and increasing the immune response of said mammal.

The term "antigen" denotes any natural or recombinant protein, in its native or mutated form, derived from a parasite or pathogenic agent other than Toxoplasma gondii capable of inducing in a mammal a cellular or humoral immune response. The purpose of combining the mutant strain of Toxoplasma gondii with such an antigen is to enhance the immune response of the mammal and thereby confer a better protection against an apicomplex infection.

By "adjuvant" is meant any substance capable of enhancing and prolonging the immune response directed against the targeted antigen. The mechanism involved in making the immune response more effective is dependent on the adjuvant used. Adjuvants are substances well known to those skilled in the art, among which include aluminum salts, squalene, saponins, constituents or bacterial toxins, or certain proteins (peptone, albumin, casein).

The term "stabilizer or preservatives" denotes the compounds which make it possible to preserve the toxoplasma gondii strains in their packaging perfectly. The purpose of these compounds is to ensure the viability of T. gondii strains. Stabilizers or preservatives are substances that are well known to those skilled in the art, among which include carbohydrates (sorbitol, mannitol, lactose, sucrose, glucose, dextran, trehalose) and polar organic solvents such as DMSO. (dimethylsulfoxide), polysorbates. By "vector" is meant an entity used to penetrate a gene of interest into a cell. Vectors are substances well known to humans of Art, among which include nanoparticles, ISCOMs (ie "immune stimulatory complexes"), etc ...

By "increasing the immune response" is meant the activation of the different pathways of the mammalian immune system by the combination consisting of the mutant strain of T. gondii with a second antigen. It is to activate the innate immune response through an increase in the synthesis of cytokines of distinct categories such as interferons or interleukins. Interleukin-12 (IL-12) is able to stimulate Natural Killer (NK) cells. The cells thus stimulated will secrete interferon-γ (IFN-gamma), which plays a major role in protecting against intracellular parasites such as T. gondii. In an adult mammal with a mature and competent immune system, the immune response is based on adaptive immunity (specific proliferation in response to foreign antigens by CD4 + and CD8 + T cells) in addition to the innate response.

According to another particular embodiment, strains of Toxoplasma gondii isolated from their natural environment for their use according to the present invention may be associated with at least one antiparasitic compound or an antibiotic selected from the group comprising or consisting of pyrimethamine, sulfadiazine , cotrimoxazole, clindamycin, azithromycin or atovaquone.

According to another more particular embodiment, strains of Toxoplasma gondii isolated from their natural environment for their use according to the present invention may be associated with at least one antiparasitic compound or an antibiotic selected from the group comprising or consisting of pyrimethamine, the sulfadiazine, cotrimoxazole, clindamycin, azithromycin or atovaquone and, to a corticosteroid.

The present invention also relates to a method for preventing the onset and / or treating, in a mammal, ocular lesions caused by one or more apicomplexes of the family Sarcocystidae comprising a step of administering tachyzoites of one or more mutant strains of Toxoplasma gondii attenuated virulence to said mammal to reduce the number of ocular lesions. According to a particular embodiment, in the method according to the present invention, the mutant strains of Toxoplasma gondii have at least one adhesin MIC-1 or a MIC-3 adhesin inactivated by gene modification on at least one of the mic-1 or mic-3 genes.

According to a more particular embodiment, in the method according to the present invention, the mutant strains of Toxoplasma gondii have at least one MIC-1 adhesin and / or an inactivated MIC-3 adhesin by the deletion of at least one of the mic genes. - 1 and / or mic-3.

According to another particular embodiment, in the method according to the present invention, the mutant strains of Toxoplasma gondii have both the MIC-1 and MIC-3 adhesins inactivated by a gene modification involving the two mic-1 and mic-3 genes. .

According to another more particular embodiment, in the method according to the present invention, the mutant strains of Toxoplasma gondii have both the MIC-1 and MIC-3 adhesins inactivated by the deletion of the two mic-1 and mic-3 genes.

According to another particular embodiment, in the method according to the present invention, the mammal is a human being or an animal.

In a non-vaccinated mammal according to the method of the present invention, challenge infection leads to elevated intraocular synthesis of IFN-γ. The method according to the present invention inhibits this intraocular synthesis of IFN-gamma resulting from the test infection. The present invention also relates to a method for preventing the occurrence and / or treating, in a mammal, intraocular inflammation caused by one or more apicomplexes of the family Sarcocystidae comprising a step of administering tachyzoites of a strain or several mutant strains of Toxoplasma gondii of attenuated virulence to said mammal. According to another more particular embodiment, in the method according to the present invention, the administration of tachyzoites of a strain or several mutant strains of Toxoplasma gondii is carried out enterally or parenterally.

The following figures and examples are given solely by way of illustration of the subject of the present invention and in no way constitute a limitation thereof. Description of figures

Figure 1A: Ophthalmologic clinical signs in Swiss Webster (OF1) mice 4 weeks after challenge infection.

 The determination of ophthalmological clinical signs is performed under a binocular microscope on each eye of each of the mice 4 weeks after the mice have been orally infected with 50 cysts of the 76K strain of Toxoplasma gondii. The mice were vaccinated with 100 tachyzoites of the strain Toxo -3 KO honey 4 weeks before test infection (black column) or not (gray column).

 - on the abscissa:

 o (a) ocular lesions of the uveitis / hyalite type,

 o (b) hemorrhagic-type ocular lesions,

 o (c) ocular lesions of the corneal type,

 o (d) ocular lesions of the cataract type.

 - on the ordinate: percentage of eyes with lesions. Figure 1B: Ophthalmological clinical signs in Swiss Webster (OF1) mice 8 weeks after challenge infection.

 The determination of the ophthalmological clinical signs is performed under a binocular microscope on each eye of each of the mice 8 weeks after the mice have been infected orally with 50 cysts of the 76K strain of Toxoplasma gondii. The mice were vaccinated with 100 tachyzoites of the strain Toxo -3 KO honey 4 weeks before test infection (black column) or not (gray column).

 - on the abscissa:

 o (a) ocular lesions of the uveitis / hyalite type,

 o (b) hemorrhagic-type ocular lesions,

 o (c) ocular lesions of the corneal type,

 o (d) ocular lesions of the cataract type.

 - on the ordinate: percentage of eyes with lesions.

Figure 1C: Ophthalmologic clinical signs in Swiss Webster (OF1) mice 12 weeks after challenge infection.

The determination of ophthalmological clinical signs is performed under a binocular microscope on each eye of each of the mice 12 weeks after the mice have been infected orally with 50 cysts of the 76K strain of Toxoplasma gondii. The mice were vaccinated with 100 tachyzoites of the strain Toxo honey -3 KO 4 weeks before test infection (black column) or not (gray column).

 - on the abscissa:

 o (a) ocular lesions of the uveitis / hyalite type,

 o (b) hemorrhagic-type ocular lesions,

 o (c) ocular lesions of the corneal type,

 o (d) ocular lesions of the cataract type.

 - on the ordinate: percentage of eyes with lesions.

Figure 2A: Evaluation of the number of intracerebral cysts in Swiss Webster (OF1) mice 4 weeks after challenge infection.

 Counting of the number of intracerebral cysts was performed from mouse brain morsel 4 weeks after the mice were orally infected with 50 cysts of Toxoplasma gondii strain 76K. Each point represents a mouse. Eight to ten counts are carried out on 10 of this crushed material using a binocular microscope on Malassez cells. The average is then calculated and reported to the entire initial volume to estimate the number of intracerebral cysts.

 - abscissa: lots of Swiss Webster mouse (OF1):

 lot (i): mice which received 100 tachyzoites of the strain Toxo -3 KO honey intraperitoneally and then infected with 50 cysts of the strain 76K of

Toxoplasma gondii (black squares),

 lot (ii): mice only infected with 50 cysts of Toxoplasma gondii strain 76K (black circles).

 - on the ordinate: number of intracerebral cysts. Figure 2B: Evaluation of the number of intracerebral cysts in Swiss Webster (OF1) mice 8 weeks after challenge infection.

Counting of the number of intracerebral cysts was performed from mouse brain mace 8 weeks after the mice were orally infected with 50 cysts of Toxoplasma gondii strain 76K. Each point represents a mouse. Eight to ten counts are carried out on 10 of this crushed material using a binocular magnifying microscope on Malassez cells. The average is then calculated and reported to the entire initial volume to evaluate the number of intracerebral cysts.

 - abscissa: lots of Swiss Webster mouse (OF1):

 lot (i): mice which received 100 tachyzoites of the strain Toxo -3 KO honey intraperitoneally and then infected with 50 cysts of the strain 76K Toxoplasma gondii (black squares),

 lot (ii): mice only infected with 50 cysts of Toxoplasma gondii strain 76K (black circles).

 - on the ordinate: number of intracerebral cysts.

Figure 2C: Evaluation of the number of intracerebral cysts in Swiss Webster (OF1) mice 12 weeks after challenge infection.

 Counting of the number of intracerebral cysts was performed from mouse brain mace 12 weeks after the mice were orally infected with 50 cysts of Toxoplasma gondii strain 76K. Each point represents a mouse. Eight to ten counts are carried out on 10 of this crushed material using a binocular magnifying microscope on Malassez cells. The average is then calculated and reported to the entire initial volume to estimate the number of intracerebral cysts.

 - abscissa: lots of Swiss Webster mouse (OF1):

 lot (i): mice which received 100 tachyzoites of the strain Toxo -3 KO honey intraperitoneally and then infected with 50 cysts of the strain 76K Toxoplasma gondii (black squares),

 lot (ii): mice only infected with 50 cysts of Toxoplasma gondii strain 76K (black circles).

 - on the ordinate: number of intracerebral cysts.

Figure 3A: Evaluation of the number of intra-retinal cysts in Swiss Webster (OF1) mice 4 weeks after challenge infection.

 Counting of the number of intra-retinal cysts was performed on the retinal-choroid complex of the enucleated eyes of the mice 4 weeks after the mice were orally infected with 50 cysts of the Toxoplasma gondii strain 76K. Each point represents a mouse.

- abscissa: lots of Swiss Webster mouse (OF1): lot (i): mice which received 100 tachyzoites of the strain Toxo mic1-3KO intraperitoneally and then infected with 50 cysts of the 76K strain of Toxoplasma gondii (black squares),

 lot (ii): mice only infected with 50 cysts of Toxoplasma gondii strain 76K (black circles).

 - on the ordinate: number of intra-retinal cysts.

Figure 3B: Evaluation of the number of intra-retinal cysts in Swiss Webster (OF1) mice 8 weeks after challenge infection.

 Counting of the number of intra-retinal cysts was performed on the retinal-choroid complex of the enucleated eyes of the mice 8 weeks after the mice were orally infected with 50 cysts of the Toxoplasma gondii strain 76K. Each point represents a mouse.

 - abscissa: lots of Swiss Webster mouse (OF1):

 lot (i): mice which received 100 tachyzoites of the strain Toxo mic1-3KO intraperitoneally and then infected with 50 cysts of the 76K strain of Toxoplasma gondii (black squares),

 lot (ii): mice only infected with 50 cysts of Toxoplasma gondii strain 76K (black circles).

 - on the ordinate: number of intra-retinal cysts.

Figure 3C: Evaluation of the number of intra-retinal cysts in Swiss Webster (OF1) mice 12 weeks after challenge infection.

 Counting of the number of intra retinal cysts was performed on the retinal-choroid complex of the enucleated eyes of the mice 12 weeks after the mice were orally infected with 50 cysts of the Toxoplasma gondii strain 76K. Each point represents a mouse.

 - abscissa: lots of Swiss Webster mouse (OF1):

 lot (i): mice which received 100 tachyzoites of the strain Toxo mic1-3KO intraperitoneally and then infected with 50 cysts of the 76K strain of Toxoplasma gondii (black squares),

 lot (ii): mice only infected with 50 cysts of Toxoplasma gondii strain 76K (black circles).

- on the ordinate: number of intra-retinal cysts. Figure 4A: assay of PIFN-γ in the Swiss Webster (OF1) mouse aqueous humor 4 weeks after the start of the challenge infection.

 The assay of gamma interferon (IFN-gamma) in the aqueous humor was performed 4 weeks after the mice were orally infected with 50 cysts of the 76K strain of Toxoplasma gondii. Each point represents a mouse,

 as abscissa: Swiss Webster mouse batches (OF1)

 lot (i): mice which received 100 tachyzoites of the strain Toxo -3 KO honey intraperitoneally and then infected with 50 cysts of the strain 76K Toxoplasma gondii (black squares),

 lot (ii): mice only infected with 50 cysts of the 76K strain of Toxoplasma gondii (black circles),

 on the ordinate: concentration of IFN-γ in pg / mL.

Figure 4B: IFN-gamma assay in the Swiss Webster (OF1) mouse aqueous humor 8 weeks after the start of the challenge infection.

 The interferon gamma (IFN-gamma) assay in the aqueous humor was performed

8 weeks after mice were orally infected with 50 cysts of Toxoplasma gondii strain 76K. Each point represents a mouse,

 as abscissa: Swiss Webster mouse batches (OF1)

 lot (i): mice which received 100 tachyzoites of the strain Toxo -3 KO honey intraperitoneally and then infected with 50 cysts of the strain 76K Toxoplasma gondii (black squares),

 lot (ii): mice only infected with 50 cysts of Toxoplasma gondii strain 76K (black circles),

 on the ordinate: concentration of IFN-γ in pg / mL.

Figure 4C: Assay of IFN-γ in Swiss Webster (OF1) mouse aqueous humor 12 weeks after the start of challenge infection.

 The interferon-gamma (IFN-gamma) assay in the aqueous humor was performed 12 weeks after the mice were orally infected with 50 cysts of the Toxoplasma gondii strain 76K. Each point represents a mouse.

- abscissa: lots of Swiss Webster mice (OF1) lot (i): mice which received 100 tachyzoites of the strain Toxo mie 1-3 KO intraperitoneally and then infected with 50 cysts of the 76K strain of Toxoplasma gondii (black squares),

 lot (ii): mice only infected with 50 cysts of Toxoplasma gondii strain 76K (black circles),

 on the ordinate: concentration of IFN-γ in pg / mL.

Figure 5A: Ophthalmological clinical signs in Swiss Webster (OF1) mice 4 weeks old and infected in utero with Toxoplasma gondii.

 The determination of ophthalmologic clinical signs in the 4-week-old young mice infected in utero with Toxoplasma gondii is performed using a binocular loupe under general anesthesia by inhalation of 2.5% isoflurane gas (oxygen at 3L / min). In order to evaluate inflammation, the following rating is used:

 • Stage 0: no inflammation,

 • Stage 1: Tyndall in anterior or moderate vitreous chamber,

• Stage 2: Tyndall in anterior or severe vitreous chamber and / or dilation of the iris and / or conjunctivo-scleral vessels,

 • Stage 3: Corneal disorder and retro-corneal precipitates and / or very severe hyalite,

 • Stage 4: Secondary Cataract.

 Each point represents the cumulative clinical stage for a young mouse (cumulative clinical stage being the sum of the clinical stages of the two eyes per mouse).

 - on the abscissa: lots of Swiss Webster (OF1) mice:

 o lot (i): young mice born to mothers who received 100 tachyzoites of the strain Toxo mie 1-3 KO intraperitoneally and then infected with 15 cysts of Toxoplasma gondii strain 76K on day 12 of pregnancy (black circles), o lot (ii): young mice born to unvaccinated mothers uninfected with 15 cysts of Toxoplasma gondii strain 76K on day 12 of pregnancy (black squares),

 o lot (iii): young mice born to mothers who had only been infected with 15 cysts of Toxoplasma gondii strain 76K on day 12 of pregnancy (black triangles).

- on the ordinate: cumulative clinical stage. Figure 5B: Ophthalmological clinical signs in Swiss Webster (OF1) mice, 8 weeks old, infected in utero with Toxoplasma gondii.

 The determination of ophthalmologic clinical signs in the 8-week-old mouse infected in utero with Toxoplasma gondii is performed post-mortem using a binocular loupe. In order to evaluate inflammation, the following rating is used:

 • Stage 0: no inflammation,

 • Stage 1: Tyndall in anterior or moderate vitreous chamber,

• Stage 2: Tyndall in anterior or severe vitreous chamber and / or dilation of the iris and / or conjunctivo-scleral vessels,

 · Stage 3: Corneal disorder and retro-corneal precipitates and / or very severe hyalite,

 • Stage 4: Secondary Cataract.

 Each point represents the cumulative clinical stage for a young mouse (cumulative clinical stage being the sum of the clinical stages of the two eyes per mouse).

 - on the abscissa: lots of Swiss Webster (OF1) mice:

 o lot (i): young mice born to mothers who received 100 tachyzoites of the strain Toxo mie 1-3 KO intraperitoneally and then infected with 15 cysts of Toxoplasma gondii strain 76K on day 12 of pregnancy (black circles), o lot (ii): young mice born to unvaccinated mothers uninfected by 15 cysts of Toxoplasma gondii strain 76K at day 12 of pregnancy

(black squares),

 o lot (iii): young mice born to mothers who had only been infected with 15 cysts of Toxoplasma gondii strain 76K on day 12 of pregnancy (black triangles).

 - on the ordinate: cumulative clinical stage.

Figure 6: Evaluation of the number of intracerebral cysts in Swiss Webster (OF1) mice, 8 weeks old, infected in utero with Toxoplasma gondii.

Counting of the number of intracerebral cysts was made from a brain seed of 8-week-old suckling mice whose mothers were or were not infected at 12 gestation with 15 cysts of Toxoplasma gondii strain 76K. Eight to ten counts are made on 10 of this crushed material using a binocular loupe on Malassez cells. The average is then calculated and reported to the entire initial volume to evaluate the number of intracerebral cysts. Each point represents a mouse.

 - abscissa: lots of Swiss Webster mouse (OF1):

 o lot (i): young mice born to mothers who received 100 tachyzoites of the strain Toxo mie 1-3 KO intraperitoneally and then infected with 15 cysts of Toxoplasma gondii strain 76K on day 12 of pregnancy (black circles), o lot (ii): young mice born to unvaccinated mothers uninfected with 15 cysts of Toxoplasma gondii strain 76K on day 12 of pregnancy (black squares),

 o lot (iii): young mice born to mothers who were only infected with 15 cysts of Toxoplasma gondii strain 76K on day 12 of pregnancy (black triangles).

 - on the ordinate: number of intracerebral cysts.

Figure 7: Evaluation of the number of intra-retinal cysts in Swiss Webster (OF1) mice, 8 weeks old, infected in utero with Toxoplasma gondii.

 Counting the number of intra-retinal cysts was performed on the retinal-choroidal complex of enucleated eyes of young mice aged 8 weeks and whose mothers were infected or not on day 12 of gestation by 15 cysts of the strain 76K Toxoplasma gondii . Each point represents a mouse.

 - abscissa: lots of Swiss Webster mouse (OF1):

 o lot (i): young mice born to mothers who received 100 tachyzoites of strain Toxo mie 1-3 KO intraperitoneally and then infected with 15 cysts of Toxoplasma gondii strain 76K on day 12 of pregnancy (black circles), o lot ( (ii): young mice born to unvaccinated and uninfected mothers of Toxoplasma gondii strain 76K on pregnancy day 12 (black squares),

 o lot (iii): young mice born to mothers who had only been infected with 15 cysts of Toxoplasma gondii strain 76K on day 12 of pregnancy (black triangles).

- on the ordinate: number of intra-retinal cysts. Example 1 Efficacy of the strain Toxo micl-3 KO in the prevention of toxoplasmosis in a mouse model of chronic ocular toxoplasmosis

1 - Experimental protocol

1.1 - Animals

 Vaccination is performed on Swiss Webster (OF1), non-consanguine, female, 8 week old mice from the January breeding center (Le Genest-Saint-Isle, France). The mice are maintained throughout the confinement level 2 animal facility experiment in order to minimize the risk of external contamination. 1.2 - T. gondii strain

1.2.1 - Toxo strain micl-3 KO

The mutant strain of Toxoplasma gondii, Toxo micl-3 KO, whose genes coding for the MIC1 and MIC3 proteins were invalidated, is maintained by successive passages on a human foreskin fibroblast line (HFF) grown in DMEM medium (Dulbecco's Modified Eagle Medium) supplemented with 10% fetal calf serum, 2 mM L-glutamine, 100 U / mL penicillin and 100 U / mL streptomycin.

After lysis of the cell layer, the tachyzoites are recovered in the supernatant and counted on Malassez cell. The concentration is then adjusted to obtain a final dose of 100 tachyzoites in 200 DMEM medium, corresponding to the mouse vaccine dose.

1.2.2 - HR strain

The wild strain RH of Toxoplasma gondii, from which the strain Toxo mic1-3 KO is derived, is also maintained by successive passages on a line of human foreskin fibroblasts (HFF) cultured in DMEM medium to which fetal calf serum is added. %, 2 mM L-glutamine, 100 U / mL penicillin and 100 U / mL streptomycin.

For the preparation of the total parasite extract, the tachyzoites of strain RH are washed, sonicated twice at 60 watt / s for 10 min in ice and centrifuged at 2000 g for 30 min at + 4 ° C. The supernatant is recovered and the concentration is determined by an assay kit (BCA assay) that uses as standard Bovine Albumin Serum (BSA). The aliquots are stored at -20 ° C.

1.2.3 - Strain 76K

The Type II 76K strain is used for the mouse challenge infection. This strain is conserved as cysts by continuous passages on CBA / J mice by gavage (mouse cycle). On the eve of the challenge infection, a cycle mouse, infected at least two months before with 76K strain cysts, is sacrificed by cervical dislocation.

The brains of mice are recovered after washing with alcohol from the coat of the animal's head. A cutaneous incision with scissors is performed at the level of a retro-auricular nuchal line. The scalp is then anteverted and two craniotomies beginning at the occipital foramen to the frontal bones are performed. The cranial vault is removed and the brain is removed in its entirety. The brain is then ground in 5 mL of RPMI medium in a potter. The ground material is left overnight at + 4 ° C. After counting Malassez cell cysts, the concentration is adjusted to obtain infection doses of 200 each containing 50 cysts.

1.3 - Vaccination protocols / test infection

Swiss-OF1 mice are divided into two distinct lots: Batch (i): composed of 27 female mice vaccinated intraperitoneally using a 25-gauge needle. Vaccination is carried out with 100 tachyzoites of the strain Toxo miel -3 KO, the production of which is described in paragraph 1.2.1.

 o lot (ii): composed of 30 unvaccinated female control mice,

Twenty-eight days after vaccination (D28), a retro-orbital blood test was performed on all the mice to diagnose seroconversion in mice by the ELISA technique.

Thirty days after vaccination (D30) mice from lots (i) and (ii) were subjected to gavage challenge infection using an 18 gauge cannula with 50 cysts of Toxoplasma gondii strain 76K. , prepared in accordance with the description in paragraph 1.2.3. Twenty-eight days after challenge infection (J58), retro-orbital blood sampling was performed on all mice.

For each batch, one-third of the animals were sacrificed 4 weeks after force-feeding (J58), another third at 8 weeks (J86) and the last third at 12 weeks (J104). On each mouse, an ophthalmological examination is performed. Intracerebral and intra-retinal toxoplasmic cysts are counted and the intraocular immune response is analyzed.

1.4 - Serological analyzes

The serological status of the mice is determined by an indirect type ELISA test. The blood samples are centrifuged at 5,000 g for 15 min and the serum is recovered. The total parasitic extract of the RH strain whose preparation is described in section 1.2.2 is diluted in a pH9.6 carbonate buffer to obtain a final concentration of 10 μg / mL. Flat-bottomed 96-well plates are then sensitized overnight at + 4 ° C. by depositing in each well 100 of total Toxoplasma gondii extract. The plates are then washed three times with the washing buffer (PBS 1x - Tween 20 0.05%) and saturated for 1 h 30 at 37 ° C with a solution of PBS IX - Tween 20 0.05% supplemented with 4% Serum Bovine Albumin (BSA) (Sigma). The medium is then removed.

The sera to be tested are diluted to l / ^50th in a solution of PBS IX - 0.05% Tween 20) and are deposited in duplicate in the wells. After one hour of incubation at 37 ° C. and a new washing series, the secondary anti-mouse IgG antibody coupled to the alkaline phosphatase (Sigma A3562, goat anti-Mouse IgG) and diluted to 1/5000 ^eme is deposited at the rate of 100 per well. The samples are then incubated for one hour at 37 ° C. After a new series of three washes, the revelation is made by adding to each well of 100 μl, a disodium paranitrophenylphosphate solution (PnPP) (Sigma) at 1 mg / ml, in a DEA-HCl buffer. After 20 min of incubation at room temperature and protected from light, the absorbance at 405 nm is measured using a plate reader (Multiskan MCC340 Wallace). The mice are considered seroconverted when the absorbance obtained is 2.5 times greater than the absorbance obtained with the negative control derived from serum of healthy naive mice.

1.5 - Ophthalmological analyzes Before the sacrifice of the mice, ophthalmological analyzes are carried out using a binocular microscope (Zeiss OPMI 99 colposcope foot on which is fixed a binocular head Zeiss F 170 with its two objectives) after instillation of two drops of mydriactum 0, 1% in each eye at 10 min intervals. The examination of the fundus is then performed using the same tool with the help of a lens "superfluid" of 90 diopters. The animal is brought under the light beam with a zoom of 0.6. The eye is centered, then the lens is brought 5 mm from the eyeball without coming into contact with it.

1.6-Analysis of the Intraocular Immune Response Immediately after sacrifice, an aqueous humor sample is taken under a binocular loupe using a 30 gauge needle mounted on a 1 ml syringe. The two samples corresponding to the two eyes of the same mouse are combined and intra-ocular IFN-γ is assayed by ELISA (BD Opt EIA Mouse IFN-γ ELISA set). On D-1, the capture antibody diluted to 1/250 in "coating" buffer (dilution buffer: 85 mM NaHCO ₃ , 15 mM Na ₂ CO ₃ , pH 9.5) is deposited on a plate 96 well. These plates are incubated at + 4 ° C all night. After washing with 0.05% PBS-Tween 20 buffer, the plate is saturated for 1h at room temperature with saturation buffer (IX PBS - 10%> FCS) at 200 per well. After a further series of three washes, the aqueous humor samples diluted to l / ^10th in saturation buffer are deposited and subsequently incubated for two hours at room temperature at 50 per well. In parallel, a range is made from murine IFN-γ obtained commercially. After a further series of wash, 50 of the solution containing the antibody and the detection of enzyme are deposited at a dilution of l / 250 ^th in the saturation buffer and incubated for lh. After a new round of washing, the plate is revealed with the substrate (Tetramethylbenzidine, Sigma), at a rate of 50 μl per well. After 30 min, 25 μl of stop solution (H ₂ S0 ₄ 2N) are added. The optical densities are read at 450 nm using a plate reader (Multiskan MCC340 Wallace).

1.7 - Numeracy of intracerebral and intracerebral cysts 1.7.1 - Intracerebral cysts The brains of mice are recovered after washing with alcohol from the coat of the animal's head. A cutaneous incision with scissors is performed at the level of a retro-auricular nuchal line. The scalp is then anteverted and two craniotomies beginning at the occipital foramen to the frontal bones are performed. The cranial vault is removed and the brain is removed in its entirety. The brain is then ground in 5 mL of RPMI medium in a potter. The ground material is left overnight at + 4 ° C.

For the counting of cysts, eight to ten counts are made on 10 of this crushed material using a binocular microscope on Malassez cells. The average is then calculated and reported to the entire initial volume to estimate the number of intracerebral cysts.

1.7.2 - Intrainthral cysts

After taking aqueous humor, the eyes of the mice are enucleated. Under a binocular loupe, complete conjunctival debridement is practiced. A limbal incision is made and the cornea is extracted. Four scleral orthogonal incisions are then made to the posterior pole of the Vannas scissors and the retina-choroid-scleral assembly is spread flat on the work surface. The lens is also removed by maximizing the vitreous gel in contact with the retina to minimize trauma. The retina-choroid complex is then gently removed using a micromanipulator and placed in 50 RPMI medium, then homogenized by "back and forth" in the cone of a micropipette.

For counting cysts, the entire sample is observed between slide and coverslip using a binocular loupe.

2 - Results 2.1. - Conduct of the experiment

Thirty days after vaccination, the mice were challenged by gavage with 50 cysts of the 76K strain.

2.2. - Serological analyzes

One month after vaccination, serological testing was performed on all animals. The 27 vaccinated animals in lot (i) have an antibody titre greater than 2.5 times that of the control mice of batch (ii) and are therefore considered to be seroconverted with respect to Toxoplasma gondii. In contrast, mice in the control group remain seronegative.

A second serological test was performed one month after the challenge infection. After the challenge infection, all mice in the vaccinated and infected lot (i) and the infected lot (ii) are seropositive. On the other hand, the optical density observed from the sera of the vaccinated and infected mice is higher than that observed from the mice only vaccinated or uninfected, thus reflecting a higher antibody level in the vaccinated and infected mice compared to that observed. in mice only vaccinated or uninfected.

2.3. - Ophthalmological analyzes

Four weeks post-challenge challenge, thirty-eight eyes were examined (18 in the vaccinated and then infected group - lot (i) and, in the infected control group - lot (ii) .The results are shown in Figure 1A In the infected control group (lot (ii)), eight eyes showed inflammatory signs: 7 were uveitis (35%) and one was haemorrhagic (5%) .These signs were found in 40% ) eyes analyzed. In the vaccinated and then infected group (lot (i)), no inflammatory lesions were observed, but one animal had a bilateral corneal case (11% of the eyes analyzed) and another a cataract (11% of the eyes analyzed ).

At eight weeks post challenge, thirty-eight eyes were examined (18 in the vaccinated and then infected group - lot (i) and, in the infected control group - lot (ii)). In the infected control group (lot (ii)), six eyes showed inflammatory signs of uveitis type (30%>), two eyes of signs of cataracts (10%>) and only one of the signs of bleeding type (5% ). These signs were thus found in 45% of the eyes analyzed. In the vaccinated and then infected group (lot (i)), no inflammatory lesions were observed but one animal presented, again, a corneal case bilaterally (Figure 1B).

At twelve weeks post challenge, thirty six eyes were examined (16 in the vaccinated and then infected group - lot (i) and in the control group - lot (ii)). In the infected control group (lot (ii)), five eyes showed inflammatory signs of uveitis (25%) and three of cataracts (15%). These signs were thus found at 40% of the eyes analyzed. In the vaccinated and then infected group (lot (i)), no inflammatory lesions were observed (Figure 1C).

In summary, lesions were found in 41.6% of the unvaccinated and infected control mice (batch (ii)). The main clinical signs observed are hyalites (30%>), haemorrhages (3.3%) and cataracts (8.3%). In the vaccinated and infected group (lot (i)), only 7.7% of the eyes had bilateral corneal lesions. In addition, these clinical signs are not described as a consequence of a T. gondii infection, they are most likely due to another cause such as trauma suffered in the cages or during handling.

2.4. - Numeration of intracerebral and intratretinal cysts

2.4.1 - Intracerebral cysts

The presence of intracerebral cysts was investigated in the brains of uninfected control mice (lot (ii)) and vaccinated and infected (lot (i)):

• At four weeks post challenge, the control mice (lot (ii)) had an average number of intracerebral cysts of 718 ± 187 cysts whereas no cysts were counted in the brains of previously vaccinated mice. (lot (i)) (Figure 2A),

• At eight weeks post-infection challenge, the control mice (lot (ii)) had an average number of intracerebral cysts of 880 ± 394 cysts whereas no cysts were counted in the brains of previously vaccinated mice (lot (i)) (Figure 2B),

• At 12 weeks post-challenge, the control mice (lot (ii)) had an average number of intracerebral cysts of 1,094 ± 303 cysts whereas no cysts were counted in the brains of previously vaccinated mice. (lot (i)) (Figure 2C).

2.4.2 - Intrainthral cysts

The presence of intra-retinal cysts was investigated in the eyes of uninfected control mice (lot (ii)) and vaccinated and infected (lot (i)):

• At four weeks post challenge, the control mice (lot (ii)) had an average number of cysts per eye of 4.50 ± 2.26 against 0.66 ± 0.77 cysts per eye for mice in the vaccinated lot (lot (i)) (Figure 3A),

 • At eight weeks post challenge, the control mice (lot (ii)) had an average number of cysts per eye of 5.55 ± 3.56 versus 0.44 ± 0.51 cysts per eye for the mice. the vaccinated lot (lot (i))

(Figure 3B),

 • Finally, at 12 weeks post-challenge infection, the control mice (lot (ii)) had an average number of cysts per eye of 4.3 ± 2.66 against 0.31 ± 0.60 cysts per eye for mice of the vaccinated lot (lot (ii)) (Figure 3C).

This experiment showed a clear decrease in the number of intrainthral cysts in the vaccinated mice (batch (i)) compared to the unvaccinated control mice (batch (ii)). Thus, only 40% of the eyes (21/52 eyes) of the vaccinated mice (lot (i)) exhibited intra-retinal cysts against 96% of the eyes of the control mice (lot (ii)) (58/60 eyes). Similarly, the mean number of intra- retinal cysts was 4.8 ± 2.85 cysts per eye for control mice (lot (ii)) versus 0.46 ± 0.63 cysts per eye for vaccinated mice (batch (i)), a decrease greater than 90%>.

2.5. - Analysis of the immune response Aqueous samples were taken in the mice of the control group (batch (ii)) and the vaccinated group (batch (i)). IFN-gamma cytokine was assayed in the aqueous humor. The ocular defense is done by increasing production of IL-12 which in turn induces secretion of IFN-γ and TNF-α. This inflammatory intraocular environment is highly deleterious to the eye. Four weeks after challenge infection, the average intraocular secretion of IFN-γ in unvaccinated but infected controls (lot (ii)) is 7.659 ± 7.980 pg / mL (Figure 4A). Still in the animals of batch (ii), this intraocular secretion is 722 ± 1.045 pg / ml at eight weeks post-infection (Figure 4B) and 1,200 ± 1.866 pg / ml at twelve weeks post-infection (Figure 4C). This decrease is explained by the spontaneous evolution of inflammatory attacks, resolving in about 4 weeks. For mice previously vaccinated with the strain Toxo micl-3 KO (lot (i)), no local secretion of IFN-γ was detected, four (34 ± 42 pg / ml), eight (21 ± 34 pg / ml). mL) or twelve (1 ± 2 μg / mL) weeks after infection (Figures 4A, 4B and 4C), indirectly indicating the absence of deleterious inflammatory processes for the eyes.

EXAMPLE 2 Efficacy of the strain Toxo micl-3 KO for the prevention of toxoplasmosis in a mouse model of congenital ocular toxoplasmosis

1 - Experimental Protocol 1.1 - Animals

 Vaccination is performed on Swiss Webster (OF1), non-consanguine, female, 8 week old mice from the January breeding center (Le Genest-Saint-Isle, France). The mice are maintained throughout the confinement level 2 animal facility experiment in order to minimize the risk of external contamination.

1.2 - T. gondii strains

1.2.1 - Toxo strain micl-3 KO

The mutant strain of Toxoplasma gondii, Toxo micl-3 KO, whose genes coding for the MIC1 and MIC3 proteins were invalidated, is maintained by successive passages on a line of human foreskin fibroblasts (HFF) grown in DMEM medium (Dulbecco's Modified Eagle Medium) supplemented with 10% fetal calf serum, 2 mM L-glutamine, 100 U / mL penicillin and 100 U / mL streptomycin.

 After lysis of the cell layer, the tachyzoites are recovered in the supernatant and counted on Malassez cell. The concentration is then adjusted to obtain a final dose of 100 tachyzoites in 200 DMEM medium, corresponding to the mouse vaccine dose.

1.2.2 - HR strain

The wild strain RH of Toxoplasma gondii, from which the strain Toxo micl-3 KO is derived, is also maintained by successive passages on a line of Human foreskin fibroblasts (HFF) grown in DMEM medium supplemented with 10% fetal calf serum, 2 mM L-glutamine, 100 U / mL penicillin and 100 U / mL streptomycin.

For the preparation of the total parasite extract, the tachyzoites of strain RH are washed, sonicated twice at 60 watts / sec for 10 min in ice and centrifuged at 2,000 g for 30 min at + 4 ° C. The supernatant is recovered and the concentration is determined by a kit of assay (BCA assay) which uses as standard Bovine Serum Albumin (BSA). The aliquots are stored at -20 ° C.

1.2.3 - Strain 76K

The Type II 76K strain is used for the mouse challenge infection. This strain is conserved as cysts by continuous passages on CBA / J mice by gavage (mouse cycle). On the eve of the challenge infection, a cycle mouse, infected two months earlier by 76K strain cysts, is sacrificed by cervical dislocation.

The brains of mice are recovered after washing with alcohol from the coat of the animal's head. A cutaneous incision with scissors is performed at the level of a retro-auricular nuchal line. The scalp is then anteverted and two craniotomies beginning at the occipital foramen to the frontal bones are performed. The cranial vault is removed and the brain is removed in its entirety. The brain is then ground in 5 mL of RPMI medium in a potter. The ground material is left overnight at + 4 ° C.

The cysts are then counted on Malassez cell and the concentration is adjusted to obtain infection doses of 200 each containing 15 cysts.

1.3 - Vaccination protocols / test infection

Female Swiss-OF1 mice are divided into three distinct lots:

• lot (i) consisting of 10 vaccinated and infected female mice (vaccinated / infected lot). The mice are vaccinated on the first day of the experiment (J0) intraperitoneally using a 25-gauge needle. Vaccination is carried out with 100 tachyzoites of the strain Toxo micl-3 KO, the production of which is described in paragraph 1.2.1., • lot (ii) consisting of 5 unvaccinated and uninfected female mice (unvaccinated / uninfected lot),

 • lot (iii) consisting of 15 unvaccinated and infected female mice (unvaccinated / infected lot). Twenty-eight days after vaccination (D28), submaxillary blood sampling was performed on all vaccinated mice to diagnose seroconverted mice (vaccinated / infected lot - lot (i)).

Two months after vaccination, seropositive mice in the vaccinated / infected lot (lot (i)) and all mice in the unvaccinated / uninfected lot (lot (ii)) and non-vaccinated / infected lot (lot (iii)) were put to the male for 3 days at the rate of 3 female mice for a male. Pregnant mice are diagnosed by weighing.

On day 12 of pregnancy, the mice diagnosed with the vaccinated / infected lot (i) and the unvaccinated / infected lot (lot iii) were challenged by gavage an 18 gauge cannula with 15 cysts of strain 76K, the preparation of which is described in section 1.2.3.

Four weeks after farrowing, the young mice benefit from an ophthalmological examination performed under general anesthesia obtained by inhalation of 2.5% isoflurane gas (oxygen at 3 l per minute) in an induction cage (Mark 5, Minerve SA) for 2 to 5 minutes, in groups of up to 5 mice. Eight weeks after farrowing, young mice are sacrificed and a second ophthalmological examination is performed. Ocular and cerebral cysts are counted and the intraocular immune response is analyzed.

1.4 - Serological analysis

The serological status of the mice is determined by an indirect type ELISA test. For mothers, serological status was studied 4 weeks after vaccination and 4 and 8 weeks after challenge infection. For young mice, serological status was studied in the fourth and eighth week of life.

The blood samples are centrifuged at 5,000 g for 15 min and the serum is recovered. The total extract of the RH strain whose preparation is described in section 1.2.2 is diluted in a carbonate buffer pH9.6 to obtain a final concentration of 10 μg / mL. 96-well flat-bottomed plates are then sensitized overnight at + 4 ° C by a deposit in each well of 100 μΐ, total extract of Toxoplasma gondii. The plates are then washed three times with the washing buffer (PBS 1 × - Tween 20 0.05%) and then saturated for 1 h 30 min at 37 ° C. with a solution of PBS IX-Tween 20 0.05% supplemented with 4% of serum. Bovine albumin (BSA) (Sigma). The medium is then removed.

The sera to be tested are diluted to l / ^50th in a solution of PBS IX - 0.05% Tween 20) and are deposited in duplicate in the wells. After one hour of incubation at 37 ° C. and a new washing series, the secondary anti-mouse IgG antibody coupled to the alkaline phosphatase (Sigma A3562, goat anti-Mouse IgG) and diluted to 1/5000 ^eme is deposited at the rate of 100 per well. The samples are then incubated for one hour at 37 ° C. After a new series of three washes, the revelation is made by adding to each well of 100 of a solution of disodium paranitrophenylphosphate (PnPP) (Sigma) at 1 mg / ml, in a DEA-HCl buffer. After 20 min of incubation at room temperature and protected from light, the absorbance at 405 nm is measured using a plate reader (Multiskan MCC340 Wallace). The mice are considered to be seroconverted when the absorbance obtained is 2.5 times greater than the absorbance obtained with the negative control derived from serum of naive and healthy mice.

1.5 - Ophthalmological analyzes

For each mouse, we were able to carry out two ophthalmological examinations. The first is carried out after 4 weeks of life on individuals anesthetized according to the previously described protocol. The second is performed at 8 weeks of life, after euthanasia.

After anesthesia or euthanasia of the mice, ophthalmological analyzes are performed using a binocular loupe (Zeiss OPMI 99 colposcope foot on which is fixed a binocular head Zeiss F 170 with its two objectives) after instillation of two drops of Mydriactum ^® 0.1% in each eye.

Anterior segment examination is performed with respect to corneal hydration to avoid the occurrence of exposure keratitis or corneal edema that may create artifacts. Ophthalmological examination revealed the occurrence of anterior uveitis (pigmented retro-corneal precipitates) and / or cataracts (crystalline opalescence, sutural or subcapsular cataracts or even a true nuclear cataract), hyalitis or retinal hemorrhages. In order to evaluate inflammation, the following rating was used (Sauer et al., 2009 Journal of Ophthalmology, 32: 742-749):

 • Stage 0: no inflammation,

 • Stage 1: Tyndall in anterior or moderate vitreous chamber,

 · Stage 2: Tyndall in anterior or severe vitreous chamber and / or dilatation of the iris and / or conjunctivo-scleral vessels,

 • Stage 3: Corneal disorder and retro-corneal precipitates and / or very severe hyalite,

 • Stage 4: Secondary Cataract. 1.6 - Numeration of intracerebral and intracerebral cysts

1.6.1 - Intracerebral cysts

The brains of mice are recovered after washing with alcohol from the coat of the animal's head. A cutaneous incision with scissors is performed at the level of a retro-auricular nuchal line. The scalp is then anteverted and two craniotomies beginning at the occipital foramen to the frontal bones are performed. The cranial vault is removed and the brain is removed in its entirety. The brain is then ground in 5 mL of RPMI medium in a potter. The ground material is left overnight at + 4 ° C.

For the count of cysts, eight to ten counts are made on 10 of this crushed material using a binocular loupe on Malassez cells. The average is then calculated and reported to the entire initial volume to estimate the number of intracerebral cysts.

1.6.2 - Intrainthral cysts

After taking aqueous humor, the mice are enucleated. Under a binocular loupe, complete conjunctival debridement is practiced. A limbal incision is made and the cornea is removed. Four scleral orthogonal incisions are then made to the posterior pole of the Vannas scissors and the retina-choroid-scleral set is spread flat on the work surface. The lens is also removed leaving the vitreous gel in maximum contact with the retina to minimize trauma. The retina-choroid complex is then gently removed using a micromanipulator and placed in 50 of RPMI medium, then homogenized by "going back and forth" in the cone of a micropipette. For the counting of cysts, the entire sample is observed using a binocular loupe between blade and coverslip.

1.7 - Analysis of the intraocular immune response

Immediately after sacrifice, an aqueous humor sample is taken under a binocular loupe using a 30 gauge needle mounted on a 1 ml syringe. The two samples corresponding to the two eyes of the same mouse are combined and intra-ocular IFN-γ is assayed by ELISA (BD Opt EIA Mouse IFN-γ ELISA set). A J- 1, the capture antibody diluted to l / ^250th in buffer "coating" (dilution buffer: 85 mM NaHC0 _3, 15 mM Na ₂ C0 _3, pH 9.5) is deposited on plate 96 wells. These plates are incubated at + 4 ° C all night. After washing with 0.05% PBS-Tween 20 buffer, the plate is saturated for 1h at room temperature with saturation buffer (1X PBS, 10% FCS) at 200 per well. After a further series of three washes, the aqueous humor samples diluted to l / ^10th in saturation buffer are deposited and subsequently incubated for two hours at room temperature (50 per well to IFN-γ). In parallel, a range is made from murine IFN-γ obtained commercially. After a further series of wash, 50 of the solution containing the antibody and the detection of enzyme are deposited at a dilution of l / 250 ^th in the saturation buffer and incubated for lh. After a new round of washing, the plate is revealed with the substrate (tetramethylbenzidine), at 50 μΐ, per well. After 30 minutes, 25 μl of stop solution (H ₂ SC "4 2N) are added, and the optical densities are read at 450 nm using a plate reader (Multiskan MCC340 Wallace).

2 - Results 2.1. - Conduct of the experiment

In order to demonstrate the efficacy of the Toxo micl-3 KO strain in the prevention of ocular toxoplasmosis by maternal-fetal transmission, female mice were vaccinated, put to males and infected at mid-pregnancy with a wild-type strain. T. gondii. The mice of lot (i), as well as the control mice of lots (ii) and (iii) were put to males. Then, mice from lots (i) and (iii) were subjected to challenge infection orally at twelfth day of gestation with 15 cysts of T. gondii strain 76K.

Perinatal mortality was assessed during the first 4 weeks of life. Thus, during this period, 6 out of 127 mice died in the lot (i) vaccinated, ie 4.72%.

In batch (ii), consisting of unvaccinated and uninfected control mice, only one out of 43 mice died (2.3%) and in batch (iii) unvaccinated and infected control mice, 27 mice on 83 died (32.5%).

2.2. - Ophthalmological analyzes Clinical examinations carried out in the fourth week of life of young mice were carried out under general anesthesia in 219 young mice (121 for lot (i), 42 for lot (ii) and 56 for lot (iii)) .

In the lot (i) consisting of young mice from vaccinated and infected mothers, 13.1%) of the mice showed clinical signs compared to 71.4% in the batch (iii) made up of mice from unvaccinated but infected mothers (p. <0.0001). In batch (ii), consisting of mice from unvaccinated and uninfected mothers, only 3 mice showed clinical signs of endocular inflammation, ie 7.1%, with no significant difference with lot (i) (p = 0, 52).

The cumulative clinical stage (Figure 5A) (sum of clinical stages of 2 eyes per mouse) is significantly lower in lot (i) (0.23 ± 0.64) than in lot (iii) (1.59 ± 1.83) (p <0.0001). In contrast, the mean cumulative clinical stage is comparable in lot (i) and lot (ii) (0.15 ± 0.65) (p = 0.52).

A new ophthalmological examination was performed on these same mice sacrificed at the age of eight weeks. In lot (i), only 23 out of 121 mice had clinical signs of endocular inflammation, 19%. In contrast, in batch (iii), 41 out of 56 mice had symptomatic inflammation, 73.2% (p <0.0001). The mean cumulative clinical stage of the mice in lot (i) was also significantly lower (0.85 ± 1.92) than that of the mice in lot (iii) (4.37 ± 3.10) (Figure 5B). However, no significant difference was noted between batches (i) and (ii), both for the number of young mice with symptomatic inflammation (3 out of 42 mice, or 7.1% of the mice in batch (ii), or p = 0.0711), than for the level of the average cumulative clinical stage (0.32 ± 1.24 for the young mice of lot (ii), ie p = 0.094).

On the other hand, there is an increase in cumulative clinical stages per mouse over time, between the fourth and eighth week of life (Figures 5A and 5B).

2.3. - Numeration of intracerebral and intraretinal cysts 2.3.1 - Intracerebral cysts

A brain sample was taken from 121 suckling mice in lot (i), 36 mice from batch (ii) (6 mice not removed) and 50 mice from lot (iii) (6 not taken). A significant difference is observed between the number of mice with cerebral infection in lot (i) (36.4%>) and the number of mice with cerebral infection in lot (iii) (98%>) (p < 0.0001). No cerebral cysts were detected in the young mice (ii).

The average number of cysts per brain (Figure 6) is also very significantly less in the mice of lot (i) (61 ± 159) compared to the mice in lot (iii) (282 ± 190) (p <0.0001) . 2.3.2 - Intrainthral cysts

All eyes of 219 young mice were collected (121 for lot (i), 42 for lot (ii) and 56 for lot (iii)).

A young mice is considered infected at the eye level when at least one cyst is observed retinal in at least one of the eyes. The rate of ocular infection is very significantly less in the young mice of the lot (i) (24% o the mice infected with the ocular level) than in the mice of the lot (iii) (71.4%) of the infected mice at the eye level. ). None of the mice in lot (ii) had an intra-retinal cyst. In addition, the number of mean intraspinal cysts per mouse (Figure 7) is also very significantly lower in the animals in batch (i) (0.56 ± 1.18 cysts per eye) than in the animals in the batch ( iii) (2.54 ± 4.10 cysts per eye).

2.4 - Analysis of the serological response At the fourth week of life, the ELISA assay for serum anti-Γ antibody assays. gondii carried out according to the procedure described in paragraph 1.4 shows that 98% of the mice in lot (i) were seropositive compared to 34% in the young mice in lot (iii). None of the mice in lot (ii) had anti-T. gondii antibodies.

Thus, the optical density observed at 405 nm was significantly lower for the sera of the young mice (iii) than for the mice of the lot (i) (p = 0.008), reflecting an antibody level for the suckling mice of the batch (iii) less than that of the young mice in (i).

At the eighth week of life, no additional seroconversion was observed in the young mice (i), 98% of mice with serum antibodies. In contrast, 100% of the mice in (iii) were seropositive. All the mice in lot (ii) were seronegative.

2.5 - Analysis of the intraocular immune response

All the eyes of the young mice could be tested.

The mean IFN-γ concentration in the anterior chamber was 1,170.5 ± 1,918.7 pg / mL in the mice of lot (i), of 2,147.6 ± 3,917.5 pg / mL in the mice of the batch (iii ) and 940.9 ± 180.0 pg / mL in the young mice of lot (ii).

The mean concentration of IFN-γ in the anterior chamber is significantly reduced in the mice of the lot (i) compared to that observed in the young mice of lot (iii) (p = 0.027), but for this parameter, there is no there was no statistically significant difference between the mice in lot (i) on the one hand and lot (ii) on the other hand (P = 0.44).

In addition, the IFN-γ concentration in the anterior chamber is correlated with the number of mean retinal cysts (p <0.05, R ² = 0.144) as well as with the average cumulative clinical stages observed in the fourth and eighth week of life (p <0.05, respectively R ² = 0.186 and R ² = 0.224). Finally, the average cumulative clinical stage at the eighth week of life is strictly correlated with the number of mean intrare- retinal cyst (p <0.05, R ² = 0.542).

Claims

1. Toxoplasma gondii strains isolated from their natural environment for use in the prevention and / or treatment, in a mammal, of ocular lesions associated with an apicomplex infection of the family Sarcocystidae.

2. Toxoplasma gondii strains isolated from their natural environment for their use according to claim 1, said strains possessing an attenuated virulence with respect to a virulent T. gondii strain of RH type.

3. Toxoplasma gondii strains isolated from their natural environment for use according to claim 1 or 2, wherein said mammal is a human or an animal.

4. Toxoplasma gondii strains isolated from their natural environment for their use according to any one of claims 1 to 3, wherein said strains of Toxoplasma gondii have at least one MIC-1 adhesin and / or an inactivated MIC-3 adhesin by a gene modification relating to at least one of the mic-1 and / or mic-3 genes.

5. Toxoplasma gondii strains isolated from their natural environment for their use according to any one of claims 1 to 4, wherein said strains of Toxoplasma gondii have both inactivated MIC-1 and MIC-3 adhesins by a gene modification involving the two genes mic-1 and mic-3.

6. Toxoplasma gondii strains isolated from their natural environment for use according to any one of claims 1 to 5, wherein said apicomplex of the family Sarcocystidae is Toxoplasma gondii.

7. Toxoplasma gondii strains isolated from their natural environment for their use according to any one of claims 1 to 6, wherein said ocular lesions belong to the group comprising or consisting of intraocular inflammations, uveites, hyalites or retinochoroïdites .

8. Toxoplasma gondii strains isolated from their natural environment for use according to any one of claims 1 to 7, wherein said strains are contacted with said mammal at 100 to ⁸ tachyzoites.

9. Toxoplasma gondii strains isolated from their natural environment for their use according to any one of claims 1 to 8, wherein said strains are in a dosage form selected from the group consisting of or consisting of liquid suspensions, solid dispersions or liquids, powders, pastes or lyophilisais.

10. Toxoplasma gondii strains isolated from their natural environment for their use according to any one of claims 1 to 9, wherein said strains are associated with at least one other antigen, at least one adjuvant, at least one stabilizer, at least one a preservative or a mixture of said products for stimulating and increasing the immune response of said mammal.