Infection of captive macaques with simian immunodeficiency virus (SIV) and domestic cats with feline immunodeficiency virus (FIV), both discovered in the last five years, represent excellent animal models for
infection of humans with the human immunodeficiency virus (HIV). Protection against challenge
infection and protection against development of simian and
feline acquired immunodeficiency syndrome has been achieved in each model by use of inactivated whole virus or virus-cell
vaccines. A recombinant SIV envelope
peptide vaccine has also proved efficacious. These
vaccines have protected against 10-100 animal infectious doses of the homologous cell-free virus given systemically, and, in the simian model, apparently show cross protection against a heterologous strain of SIV. Protected animals appear free of any
latent infection although late breakthroughs of
infection in a few animals imply that not all vaccinated animals are completely protected. The mechanism of protection in the simian model apparently involves envelope antibody but the role of
neutralizing antibody remains unclear. Questions remaining to be answered in both SIV and FIV models are: (1) the duration of immunity, (2) the extent of protection against heterologous strains and mucosal
infection, (3) protection against
infection with cell-associated virus and (4) the role, if any, of cellular immunity in
vaccine protection. Initial attempts at post-
infection immunotherapy with
SIV vaccines have not yet been successful. The inactivated whole SIV and FIV
vaccines offer a promising start and provide hope that a prophylactic
AIDS vaccine will be developed. Use of these animal models for
antiviral therapy is just now getting underway. Both models should prove especially useful for studies of prophylaxis and
therapy, especially during the early stages of
infection and for investigations on
drug pharmacokinetics or toxicity that can not be done as well in HIV-infected humans. The animals will also be ideal for testing the pathogenicity of
drug-induced mutant forms of SIV and FIV. For these purposes it will be necessary to create self-sustaining specific pathogen-free macaque and cat breeding colonies and provide increased housing facilities for infected animals. The future of
AIDS research is crucially dependent on the long term availability of these animal models.