AIDS vaccination studies using an ex vivo feline immunodeficiency virus model: Detailed analysis of the humoral immune response to a protective vaccine

The feline immunodeficiency virus (FIV) cat model is extensively used to in vestigate possible vaccination approaches against AIDS in humans. Although consistent levels of protection have been achieved with FIV, as with other model systems, by immunizing with whole inactivated virus or fixed infected cells, the mechanisms responsible for protection are elusive. In previous studies we showed that cats immunized with a vaccine consisting of fixed in fected cells were protected or unprotected against cell-free or cell-associ ated FIV challenge depending on the time interval between completion of vac cination and challenge. In an attempt to define possible humoral immune cor relates of protection, selected sera harvested at the times of challenge fr om such cats were examined for anti-FIV-antibody titers and properties by u sing binding and functional immunological assays. Binding assays included q uantitative Western blotting, enzyme-linked tests for antibodies to FIV gly coproteins and immunodominant linear epitopes, and tests for measuring conf ormation dependence and avidity of anti-viral-envelope antibodies. Function al assays included virus neutralization performed with two different cell s ubstrates, complement- and antibody-dependent virolysis, blocking of revers e transcriptase, and an assay that measured the ability of sera to prevent FIV growth in cocultures of infected and uninfected cells, Despite the wide spectrum of parameters investigated, no correlation between vaccine-induce d protection and the humoral parameters measured was noted.