Progressive immune dysfunction in cats experimentally infected with feline immunodeficiency virus

Area of Science:

• Veterinary Immunology
• Virology
• Immunodeficiency

Background:

• Feline immunodeficiency virus (FIV) is an important lentivirus affecting domestic cats.
• Understanding FIV's impact on the immune system is crucial for feline health management.

Purpose of the Study:

• To investigate the progressive effects of FIV infection on T-cell and B-cell immune functions in domestic cats.
• To characterize the timeline of immune deterioration following FIV infection.

Main Methods:

• Monitoring of specific-pathogen-free domestic cats post-infection with the Petaluma isolate of FIV.
• Assessment of circulating CD4+ and CD8+ T-lymphocyte counts and ratios.
• Evaluation of in vitro lymphocyte proliferation responses to pokeweed mitogen and concanavalin A.
• Assessment of in vivo antibody responses to T-dependent and T-independent synthetic polypeptide immunogens.

Main Results:

• Early FIV infection (within 6 months) showed decreased CD4+ lymphocytes and CD4+/CD8+ T-cell ratio, with a mild reduction in T-cell proliferation.
• By 11-12 months post-infection, a clear deficit in pokeweed mitogen response was observed.
• Later stages (25-44 months) revealed declining responses to concanavalin A and impaired antibody production to T-dependent antigens.
• Antibody responses to T-independent antigens remained intact throughout the study.

Conclusions:

• Feline immunodeficiency virus induces a slow, progressive impairment of T-cell mediated immunity.
• The B-cell capacity to respond to T-independent antigens is preserved during FIV infection.
• These findings highlight the specific impact of FIV on cellular immunity while humoral immunity against certain stimuli remains functional.