Inhibition of cellular activation of retroviral replication by CD8+ T cells derived from non-human primates

Abstract

SUMMARY To test the hypothesis that CD8+ T cells inhibit viral replication at the level of cellular activation, an Epstein‐Barr virus (EBV)‐transformed cell line (FEcl) from a simian immunodeficiency virus (SIV)‐seropositive sooty mangabey monkey was transfected with a human CD4 gene and shown to be replication‐competent for HIV‐1, HIV‐2 and SIV. Utilizing a dual‐chamber culture system, it was found that inhibition of viral replication can be mediated by a soluble factor. The FEcl cell line was transiently transfected with an LTR‐driven CAT reporter gene. It was found that autologous CD8+ T cells markedly inhibited CAT activity. Furthermore, co‐transfection of the FEcl cell line with an LTR‐driven tat plasmid and LTR‐CAT was able to quantitatively mitigate the suppressive effect. Thus, this inhibition appears to be directed at cellular mechanisms of viral transcription. Control transfections with an LTR‐driven CAT plasmid with a mutation at the NFkB binding site yielded no CAT activity, suggesting that most viral replication as measured by CAT activity is dependent, to a large extent, upon cellularly derived NFkB binding proteins.

The CD8+T Cell Noncytotoxic Antiviral Responses

“…However, in the case of the B cell line, in contrast to observations with the 1G5 cell line ( 44 ), only basal LTR-dependent transcription was affected, not Tat-mediated enhancement of LTR-dependent transcription ( 112 ). In this study, the CD8 + T cells from two different species of NHP, sooty mangabey and rhesus macaque, inhibited the CAT activity ( 112 ). However, Tat, introduced via a different LTR vector, reduced this effect.…”

“…CD8 + T cells and their supernatants from SIV-infected NHP also inhibited SIV replication and LTR-dependent transcription, which was demonstrated in assays using either primary CD4 + cells ( 204 ) or a B cell line ( 112 ) transfected with an LTR-chloramphenicol acetyltransferase (CAT) reporter construct. However, in the case of the B cell line, in contrast to observations with the 1G5 cell line ( 44 ), only basal LTR-dependent transcription was affected, not Tat-mediated enhancement of LTR-dependent transcription ( 112 ). In this study, the CD8 + T cells from two different species of NHP, sooty mangabey and rhesus macaque, inhibited the CAT activity ( 112 ).…”

“…Finally, PHA-stimulated CD8 + cells from uninfected sooty mangabeys (SM) suppressed SIV replication in the CD4 + cells from rhesus macaques ( 112 ). Conceivably, the CD8 + cells play a central role in the prevention of immunodeficiency disease in the SM primates ( 61 ).…”

“…Similar findings on the lack of histocompatibility dependence, even across species barriers, were made in NHP. Cultured CD8 + cells from SIV-infected sooty mangabeys suppressed viral transcription in rhesus macaque CD4 + cells transiently transfected with a long terminal repeat (LTR)-driven CAT reporter gene, without killing the target cells ( 112 ).…”

“…This reduction was independent of LTR transcription being induced either by Tat or mitogenic activation via phorbol myristate acetate (PMA) and ionomycin. In addition, CD8 + T cell supernatants also decreased transcription of the CAT reporter gene when it was under the control of a minimal promoter only containing two NF-κB elements ( 112 ). Moreover, the CD8 + T cell supernatants were able to suppress transcription via the retrovirus promoters of HTLV-1 and Rous sarcoma virus (RSV), which also contain two NF-κB elements ( 208 ).…”