Can an immune-regulatory vaccine prevent HIV infection?

Developing vaccines to prevent the establishment of HIV infection has been fraught with difficulties. It might therefore be important to consider other new strategies. Since several studies suggest that anti-inflammatory stimuli can protect from HIV infection and because HIV replicates preferably in activated T cells, we suggest here that the reduction of immune activation through a HIV-specific regulatory T-cell vaccine might thwart early viral replication. Thus, because immune activation is a good predictor of disease progression and the immune activation set point has been shown to be an early event during HIV infection, vaccinating to achieve control of early virus-specific immune activation might be advantageous.

Expansion of a subset of CD14(high)CD16(neg)CCR2(low/neg) monocytes functionally similar to myeloid-derived suppressor cells during SIV and HIV infection

Monocytes have been categorized in three main subpopulations based on CD14 and CD16 surface expression. Classical monocytes express the CD14(++)CD16(-) CCR2(+) phenotype and migrate to inflammatory sites by quickly responding to CCL2 signaling. Here, we identified and characterized the expansion of a novel monocyte subset during HIV and SIV infection, which were undistinguishable from classical monocytes, based on CD14 and CD16 expression, but expressed significantly lower surface CCR2. Transcriptome analysis of sorted cells demonstrated that the CCR2(low/neg) cells are a distinct subpopulation and express lower levels of inflammatory cytokines and activation markers than their CCR2(high) counterparts. They exhibited impaired phagocytosis and greatly diminished chemotaxis in response to CCL2 and CCL7. In addition, these monocytes are refractory to SIV infection and suppress CD8(+) T cell proliferation in vitro. These cells express higher levels of STAT3 and NOS2, suggesting a phenotype similar to monocytic myeloid-derived cells, which suppress expansion of CD8(+) T cells in vivo. They may reflect an antiproliferative response against the extreme immune activation observed during HIV and SIV infections. In addition, they may suppress antiviral responses and thus, have a role in AIDS pathogenesis. Antiretroviral therapy in infected macaque and human subjects caused this population to decline, suggesting that this atypical phenotype is linked to viral replication. J. Leukoc. Biol. 91: 803-816; 2012.