PROGRESSIVE ENCEPHALOPATHY ASSOCIATED WITH CD4 CD8 INVERSION IN ADULTFIV-INFECTED CATS/

Experimental intravenous challenge of five adult cats with the feline immunodeficiency virus Maryland isolate (FN-MD) was investigated for i ts ability to induce neurologic abnormalities associated with the onse t of immunodeficiency. Five 8-month-old cats were inoculated with 1000 median tissue culture infective dose of FIV-MD isolate, with five age -matched cats serving as uninfected controls. All FIV-MD-infected cats tested positive for serum antiviral antibodies and plasma viral DNA a s detected by polymerase chain reaction at 2, 4, 10, and 16 months pos tinfection (PI). At 10 and 16 months PI, there was a significant reduc tion in the CD4/CD8 lymphocyte ratio, with all cats having a CD4/CD8 r atio of 1 or less. Total protein electrophoretic analysis of cerebrosp inal fluid demonstrated a significantly increased albumin quotient at 4 and 16 months PI, representing a disrupted blood-brain barrier (BBB) . At 16 months PI, all cats demonstrated a preferential increase in fr ontal cortical slow-wave activity compared with control cats. Serial e valuation of brainstem auditory evoked potential recordings revealed a prolongation of the interpeak latencies times over the study time. At least one abnormality was found over time in visual and somatosensory evoked potential testing in three and four infected cats, respectivel y. Comparing lymphocyte subtype ratios with neurologic testing reveale d that every FIV-MD-infected cat exhibited an abnormality in at least one neurologic functional lest with a concurrent CD4/CD8 count ratio o f 1 or less. Overall, this study demonstrated that FIV-MD infection in adult cats results in a delayed-onset, progressive encephalopathy tha t parallels the decline in the CD4/CD8 lymphocyte ratio. Compared with prior information from pediatric FIV-MD-infected cats, these results indicate that age of infection influences the onset and severity of di sease and may be associated with CD4 cell depletion in FIV-MD-infected cats, as seen in HIV-1-infected humans.