Effect of chronic feline immunodeficiency virus infection on experimental feline calicivirus-induced disease.

Acute feline calicivirus (FCV) infection caused a more severe disease in chronically feline immunodeficiency virus (FIV) infected than in non-FIV infected cats. FIV infected cats shed significantly higher amounts of FCV through their saliva after FCV challenge than the non-FIV infected cats. However, there was no difference in the duration of FCV shedding. None of the cats exposed to FCV developed chronic FCV carriage. Both groups of cats mounted similar titers of neutralizing antibodies to FCV. Although FIV infected cats started out with significantly lower total lymphocyte and neutrophil numbers than the non-FIV infected cats, the transient lymphopenia and neutrophilia attributable to the FCV infection was of similar intensity in both groups of animals. There was no evidence that the underlying FIV-related disease or viremia was influenced by acute FCV infection. Acute FCV infection did not significantly alter the CD4+/CD8+ T lymphocyte ratio in FIV infected compared to non-FIV infected cats. The ongoing humoral IgG response to FIV was not affected by the FCV infection. There was no significant change in the proportion of FIV infected peripheral blood mononuclear cells during 8 subsequent weeks after FCV challenge as determined by polymerase chain reaction.