Reduced chronic lymphocyte activation following Interferon-α blockade in the acute phase of SIV infection in rhesus macaques. Reduced chronic lymphocyte activation following Interferon-α blockade in the acute phase of SIV infection in rhesus macaques

Pathogenic HIV/SIV infection of humans and rhesus macaques (RMs) induces persistently high production of type-I interferon (IFN-I) which is thought to contribute to disease progression. To elucidate the specific role of IFN in SIV pathogenesis, 12 RMs were treated prior to i.v. SIVmac239 infection with a high or a low dose of an antibody (AGS-009) that neutralizes most IFN subtypes, and compared with six mock-infused, SIV-infected controls. Plasma viremia was measured post infection to assess the effect of IFNα blockade on virus replication, and peripheral blood and lymphoid tissue samples were analyzed by immunophenotypical staining. Consistent with the known antiviral effect of IFN-I, high-dose AGS-009 treatment induced a modest increase in acute phase viral loads vs. controls. 4 out of 6 RMs receiving a high dose of AGS-009 also experienced an early decline in CD4+ T cell counts which was associated with progression to AIDS. Interestingly, 50% of animals treated with AGS-009 (6/12) developed AIDS within one year of infection, compared with 17% (1/6) of untreated controls. Finally, blockade of IFN decreased the levels of activated CD4+ and CD8+ T cells, as well as B-cells, as measured by PD-1 and/or Ki67 expression. The lower levels of activated lymphocytes in IFN-blockade animals supports the hypothesis that IFN signaling contributes to lymphocyte activation during SIV infection, and suggests that this signaling pathway is involved in controlling virus replication during acute infection. The potential anti-inflammatory effect of IFN blockade should be explored as a strategy to reduce immune activation in HIV-infected individuals. Overall design: 107 Rhesus macaque whole blood samples were hybridized to Illumina Human RefSeq-12 V4 BeadChips.