SIV INFECTION OF MONKEY SPLEEN-CELLS INCLUDING FOLLICULAR DENDRITIC CELLS IN DIFFERENT STAGES OF DISEASE

Immunoaffinity enriched spleen follicular dendritic cells (FDCs), lymp hocytes, and macrophages from SIVsm-inoculated cynomolgus monkeys (Mac aca fascicularis) at different stages of disease were compared for lat ent and productive SIV infection. Analysis of FDCs by in situ hybridiz ation, electron microscopy, and coculture assays indicated that compar atively high levels of virus were associated with the FDC fraction. Po lymerase chain reaction (PCR) and RT-PCR results revealed that the lev els for SIVpol DNA did not correlate with the level of env mRNA in the various cell subsets, suggesting differences in latency. Limiting dil ution assays for spliced env mRNA showed a 10-100-fold higher amount o f env mRNA in FDCs than in other spleen cell subsets early during SIV infection. At late stages of disease, the number of productively infec ted FDCs significantly decreased in parallel with a marked reduction o f the FDC network and follicular involution. Our findings indicate tha t destruction of FDCs probably reflects a cytopathic effect of SIV and /or the activity of specific antiviral cytotoxic T lymphocytes.