This virus is a member of the Lentivirus subfamily of Retroviruses. It appears to be widely distributed worldwide since at least 1960s. There are 5 FIV subtypes (Clades A to E) and they all are infectious to a variety of susceptible wild and domestic feline species. In the USA and world, the prevalence of infection for house cats is estimated to be 1 - 4%, and this number is certainly larger in the feral cat population.
FIV has a primary tropism for lymphocytes and gradually destroys sub-populations of T lymphocytes. This cytopathic effect causes a progressive loss of CD4+ lymphocytes, inversion of the CD4/CD8 ratio, and eventual loss of CD8+ lymphocytes in the late stages of infection. Cell-mediated immunity is impaired to a greater extent than antibody-mediated immunity. In addition, impaired production and dysregulation of various cytokines plays a role in pathogenesis of disease.
There is at present no viable treatment for FIV infection. Because of its genotypic and phenotypic similarity to HIV, strategies used to control HIV infection may be effective to treat FIV infection as well. Unfortunately, antiretroviral drugs are too toxic for animals, leaving virtually no alternative for treating FIV.
It is widely established that HIV particles acquire host cell antigens upon budding from the infected cell. These antigens are thought to function as co-receptors to allow the virus to infect other cells, and may even contribute to the tropism of the virus for specific cell types.
CytoDyn is developing monoclonal antibodies that interrupt or prevent the function of one of these cellular acquired antigens as therapeutic agents to treat HIV infection. This antigen, called CD11a, is an adhesion molecule that is widely recognized as an essential co-receptor for HIV infection. We hypothesized that this particular opportunity for treating HIV may be universal among the Lentivirus family and thus provide a novel target to control FIV infection. To test this hypothesis we identified an anti-CD11a that could bind to feline cells and measured its ability to suppress FIV infection in vitro.
