DNA VACCINATION USING EXPRESSION VECTORS CARRYING FIV STRUCTURAL GENES INDUCES IMMUNE-RESPONSE AGAINST FELINE IMMUNODEFICIENCY VIRUS

Following inactivated virus vaccination trials, the surface glycoprote in gp120 of the feline immunodeficiency virus (FIV) was considered as one of the determinants for protection, However, several vaccination t rials using recombinant Env protein or some peptides failed to induce protection. To understand the role of the gp120 protein in vivo, we va ccinated cats with naked DNA coding for FIV structural proteins gp120 and p10, We analyzed the ability of these vaccinations to induce immun e protection and to influence the onset of infection. Injection in cat muscles of expression vectors coding for the FIV gp120 protein induce d a humoral response. Cats immunized twice with the gp120 gene showed different patterns after challenge. Two cats were, like the control ca ts, infected from the second week after infection onwards. The two oth ers maintained a low proviral fond with no modification of their antib ody pattern. The immune response induced by gp120 DNA injection could control the level of viral replication This protective-like immune res ponse was not correlated to the humoral response, All the cats immuniz ed with the gp120 gene followed by the p10 gene were infected like the control cats, from the second week bur they developed a complete humo ral response against viral proteins after challenge. Futhermore, they showed a sudden but transient drop of the proviral load at 4 weeks aft er infection. Under these conditions, one injection of the p10 gene af ter one injection of the gp120 gene was not sufficient to stimulate pr otection. On the contrary, after a period, it seems to facilitate viru s replication. (C) 1997 Elsevier Science Ltd.