Many attempts to design prophylactic human immunodeficiency virus type 1 (HIV-1A preventative vaccine is urgently needed to curb the growing human immunodeficiency virus type 1 (HIV-1) epidemic and reduce the global economic burden of supplying lifelong antiretroviral therapies. The induction of antibodies (Abs) capable of neutralizing a broad range of viral strains is a major goal of HIV-1 vaccine research. Such broadly neutralizing Abs (BnAbs) have been isolated from HIV-1-infected individuals, and passive transfer of BnAbs to nonhuman primates has proven sufficient to prevent infection upon challenge with cell-free chimeric simianhuman immunodeficiency viruses (SHIV) (1-3). Despite the potential of BnAbs to prevent HIV-1 infection, a vaccine capable of eliciting BnAbs in HIV-1-uninfected individuals has not yet been designed. The lack of appropriate immunogens and the extensive somatic hypermutation within the variable regions of BnAbs are major impediments to their induction via vaccination (4). This inability to elicit BnAbs through immunization has spurred research interest into the potential of nonneutralizing effector functions of Abs to provide protection against HIV-1.Interest in the potential of the nonneutralizing effector functions of Abs has also been stimulated by the recent phase III human RV144 vaccine trial in Thailand, which provided evidence that nonneutralizing Ab-associated effector functions may be involved in Ab-conferred protection against HIV-1 infection (5, 6). Indeed, correlates of immunity analyses revealed that, in the absence of broadly neutralizing Abs, both high levels of IgG Abs to the V1V2 regions of the HIV-1 Env and low levels of plasma an-

Antibody-dependent activation of natural killer (NK) cells might facilitate protective outcomes in the context of HIV exposure or infection. Antibody-dependent activation is heightened in NK cells educated by interactions between killer immunoglobulin-like receptors (KIRs) and their major histocompatibility complex class I ligands during ontogeny. Differentiated NK cells, defined as CD57, also exhibit enhanced antibody-dependent responsiveness. Although KIRs are more frequently expressed on CD57 NK cells, the presented data suggest education and differentiation make independent contributions to NK cell anti-HIV envelope antibody-dependent activation.

Summary Evidence from the RV144 HIV‐1 vaccine trial implicates anti‐HIV‐1 antibody‐dependent cellular cytotoxicity (ADCC) in vaccine‐conferred protection from infection. Among effector cells that mediate ADCC are natural killer (NK) cells. The ability of NK cells to be activated in an antibody‐dependent manner is reliant upon several factors. In general, NK cell‐mediated antibody‐dependent activation is most robust in terminally differentiated CD57+ NK cells, as well as NK cells educated through ontological interactions between inhibitory killer immunoglobulin‐like receptors (KIR) and their major histocompatibility complex class I [MHC‐I or human leucocyte antigen (HLA‐I)] ligands. With regard to anti‐HIV‐1 antibody‐dependent NK cell activation, previous research has demonstrated that the epidemiologically relevant KIR3DL1/HLA‐Bw4 receptor/ligand combination confers enhanced activation potential. In the present study we assessed the ability of the KIR2DL1/HLA–C2 receptor/ligand combination to confer enhanced activation upon direct stimulation with HLA‐I‐devoid target cells or antibody‐dependent stimulation with HIV‐1 gp140‐pulsed CEM.NKr‐CCR5 target cells in the presence of an anti‐HIV‐1 antibody source. Among donors carrying the HLA‐C2 ligand for KIR2DL1, higher interferon (IFN)‐γ production was observed within KIR2DL1+ NK cells than in KIR2DL1– NK cells upon both direct and antibody‐dependent stimulation. No differences in KIR2DL1+ and KIR2DL1– NK cell activation were observed in HLA‐C1 homozygous donors. Additionally, higher activation in KIR2DL1+ than KIR2DL1– NK cells from HLA–C2 carrying donors was observed within less differentiated CD57– NK cells, demonstrating that the observed differences were due to education and not an overabundance of KIR2DL1+ NK cells within differentiated CD57+ NK cells. These observations are relevant for understanding the regulation of anti‐HIV‐1 antibody‐dependent NK cell responses.

Persistence of HIV DNA presents a major barrier to the complete control of HIV infection under current therapies. Most studies suggest that cells with latently integrated HIV decay very slowly under therapy. However, it is much more difficult to study the turnover and persistence of HIV DNA during active infection. We have developed an “escape clock” approach for measuring the turnover of HIV DNA in resting CD4+ T cells. This approach studies the replacement of wild-type (WT) SIV DNA present in early infection by CTL escape mutant (EM) strains during later infection. Using a strain-specific real time PCR assay, we quantified the relative amounts of WT and EM strains in plasma SIV RNA and cellular SIV DNA. Thus we can track the formation and turnover of SIV DNA in sorted resting CD4+ T cells. We studied serial plasma and PBMC samples from 20 SIV-infected Mane-A*10 positive pigtail macaques that have a signature Gag CTL escape mutation. In animals with low viral load, WT virus laid down early in infection is extremely stable, and the decay of this WT species is very slow, consistent with findings in subjects on anti-retroviral medications. However, during active, high level infection, most SIV DNA in resting cells was turning over rapidly, suggesting a large pool of short-lived DNA produced by recent infection events. Our results suggest that, in order to reduce the formation of a stable population of SIV DNA, it will be important either to intervene very early or intervene during active replication.