Background: SIV infected macaques treated with ART in combination with an anti-α4β7 mAb controlled plasma viremia for up to two years following discontinuation of all therapy. The mechanism of control is unknown.
Methods: We employed whole body immuno-PET/CT imaging to detect the distribution of virus and CD4+ T cells in treated animals both before and after therapy interruption. Flow cytometry and immunohistochemistry was used to confirm PET/CT results.
Results: We were able to detect virus in various lymphoid and mucosal tissues including gut in animals treated with either ART plus control IgG or ART plus anti-α4β7 mAb. Anti-α4β7 mAb promoted a redistribution of virus, with a pronounced decrease in the large intestine. The reduction in viral replication in gut tissues occurred despite the fact that anti-α4β7 mAb treatment did not result in a decrease in CD4+ T cells within the gut.
Conclusions: These results demonstrate that an anti-α4β7 mAb impacts the distribution of virus while promoting the restoration of CD4+ T cell in the gut and other lymphoid tissues following experimental infection and treatment with ART. The redisrtibution of virus and the subsequent CD4+ T cell restoration may underlie the mechanism of viral control in macaques treated with ART plus anti- α4β7 mAb.