Effect of early anti-retroviral therapy on the pathogenic changes in mucosal tissues of SIV infected rhesus macaques

The gastrointestinal tissue plays an important role in the pathogenesis of HIV/SIV infection and serves as a viral reservoir in infected individuals under antiretroviral therapy (ART). However, the effect of ART administration in the very early stage of infection on HIV/SIV replication and pathogenesis in gastrointestinal tissue has not been fully studied. In this current study, rhesus monkeys infected with SIV were treated with ART starting at day 7 post-infection. The effect of early ART on SIV replication and infection-related pathogenic changes in mucosal tissues of the infected monkeys was examined.

These results suggest that early ART administration could not effectively inhibit SIV replication in intestinal tissues and mesentery lymph nodes and could not reduce the immune activation induced by SIV infection in the intestinal tissues.

Nuclear acids were extracted from snap frozen ileum and colon tissues and mesentery lymph nodes from SIV infected monkeys with or without ART. SIV RNA and DNA loads as well as levels of CD3, CD4 and cytokine mRNA were measured by PCR and RT PCR from the isolated nuclear acids. Tissue sections were stained by immuno-fluorescence labeled antibodies for CD3 and CD4.

Without ART treatment, these monkeys underwent a mild SIV infection with low viral loads and slightly decreased CD4+ T cell counts in peripheral blood. In ART treated monkeys, SIV RNA loads were undetectable in blood with normal CD4+ T cell counts, however, SIV RNA and DNA were detected in the intestinal tissues and mesentery lymph nodes although the levels were lower than those in untreated monkeys. The levels of CD3 and CD4 positive cells in the tissues were similar between the infected untreated monkeys and infected ART treated monkeys based on RT-PCR and immune-fluorescence staining of the tissue sections. Furthermore, compatible levels of IL-6, TNF-a, IL-1b and MyD88 mRNAs were detected in most of intestinal tissues and mesentery lymph nodes of infected ART treated and infected untreated monkeys. Conclusions: These results suggest that early ART administration could not effectively inhibit SIV replication in intestinal tissues and mesentery lymph nodes and could not reduce the immune activation induced by SIV infection in the intestinal tissues.