Feline leukemia virus: current status of the feline acquired immune deficiency syndrome and immunoprevention.

In order to gain insight into the nature of the retrovirus HIV (human immunodeficiency virus) research dealing with an immune deficiency virus affecting cats FeLV is reviewed. FeLV tends to affect the host animal by weakening resistance to opportunistic infections and to an extent neoplasms. It affects T-lymphocyte as well as polymorphonuclear cells. Most infected cats resist infection and establish sound immunity to FeLV but there is evidence of a capacity of FeLV to continue to exist in a latent state. Thymic atrophy lymphoid and myeloid depletion hemolytic anemia and/or non-regenerative anemia are common clinical findings in FeLV-infected cats. In vitro tests conducted in the attempt to develop a vaccine showed that inactivated FeLV also showed some immunosuppressive effects. Whether FeLV affects a variety of cell types is under investigation. There is a possibility that FeLV affects a variety of cells through its suppression of cAMP or calcium. Immunosupression effects are attributed to specific blocking factors (e.g. free tumor antigen) in the blood which are not of viral origin or not exclusively so. Treating FeLV-infected cats with Staphylococcus aureus has shown some promise although the mechanism for it is not known exactly. Early vaccine preparations consisting of killed or live attenuated FeLV failed to produce protective levels of neutralizing antibodies or to protect from tumor development. Injections of kittens with lymphoid tumor cells was more successful as was the use of antigens isolated from cultured tumor-related antigens.