Mucosal infection with simian immunodeficiency virus (SIV) can be prevented in non-human primates by immunization with recombinant SIV gp120 and p27 in alum. This was established in the first EU sponsored Concerted Action and will be published in Nature Medicine (Lehner et al 1996). To pave the way to human application, rectal and vaginal mucosal immunization has been successfully performed with cholera toxin B (CTB) subunit (Czerkinsky et al 1995). These findings offer a firm pre-clinical and clinical baseline which we wish to develop. The present proposal addresses 3 principal objectives in developing a preventive vaccination strategy in humans.
(1) To develop the most effective and simplest route of delivery of the vaccine, using targeted iliac lymph node (TILN) immunization as a basis for comparison of protection, immunity and viral load. (2) To elucidate the mechanism of protective immunity, by examining B and T cell responses at 3 defined barriers: the recto-genital mucosa, iliac lymph nodes, and spleen with the circulating blood. (3) To generate recombinant antigens in plants so as to enable a cost-effective vaccine to be produced on an agricultural scale. The deep subcutaneous (SC) delivery required for TILN immunization in macaques will be first modified into conventional SC and/or IM injection with the aid of lymphoscintigraphy. The alternative direct rectal and vaginal immunization will be explored utilising a number of mucosal receptors. Fcg and C3b receptors enable immune complexes to bind to these receptors, and GM1 enables CTB-HIV-1 constructs to bind to the mucosa and to be interiorised. Recombinant immune complexes, as well as HIV gp120, p24 and nef antigens will be generated in transgenic tobacco plants, with the potential of large scale production, of a cost-effective vaccine. The type of immunity elicited by the modified TILN and direct mucosal immunization will be studied for a number of B and T cell functions. IgA and IgG antibodies will be assayed in the mucosal secretions, urine and serum. T cell functions will be studied for proliferative, cytotoxic and suppressor activities, as well as their b chemokines and clonal heterogeneity.
Protection from HIV-1 infection will be investigated by rectal and vaginal challenge in macaques with the HIV-1 envelope bearing chimaeric SIV (SHIV). The effectiveness of any one of the vaccines and route of delivery will be assessed by monitoring HIV infection by coculture, nested PCR and by the quantitative RNA assay to determine virus production rates. The relationship between various B and T cell functions and protective immunity should enable us to elucidate the mechanism of protection. In order to translate the results of protective immunization in non-human to human primates, parallel human immunization studies will be pursued. CTB will be used to study mucosal immune responses in HIV-1 infected subjects. As the most effective means of preventing HIV infection becomes evident in macaques, and safety criteria are satisfied, sero-negative human volunteers will be immunized in a Phase I study. We believe that this multidisciplinary project, integrating diverse and complimentary European scientific expertise, should lead to a vaccination strategy preventing sexual transmission of HIV.
Funding SchemeCSC - Cost-sharing contracts
2288 GJ Rijswijk Zh
413 46 Gfteborg