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author:("whitman, game")
1.  Activation of NK cells by HIV-specific ADCC antibodies 
Human Vaccines & Immunotherapeutics  2013;9(5):1011-1018.
HIV-specific ADCC antibodies could play a role in providing protective immunity. We have developed a whole blood ADCC assay that measures NK cell activation in response to HIV peptide epitopes. These HIV peptide-specific ADCC responses are associated with escape from immune recognition and slower progression of HIV infection and represent interesting HIV vaccine antigens. However, the mechanism by which these epitopes are expressed and whether or not they induce NK-mediated killing of cells expressing such peptide-antigens is not understood. Herein, we show that fluorescent-tagged ADCC peptide epitopes associate with blood granulocytes. The peptide-associated granulocytes become a specific target for antibody-mediated killing, as shown by enhanced expression of apoptosis marker Annexin and reduction in cell numbers. When HIV Envelope gp140 protein is utilized in the ADCC assay, we detected binding to its ligand, CD4. During the incubation, cells co-expressing gp140 and CD4 reduce in number. We also detected increasing Annexin expression in these cells. These data indicate that blood cells expressing HIV-specific ADCC epitopes are targeted for killing by NK cells in the presence of ADCC antibodies in HIV+ plasma and provide a clearer framework to evaluate these antigens as vaccine candidates.
PMCID: PMC3899135  PMID: 23324623
HIV; ADCC; NK cells; granulocytes; apoptosis
2.  Activation of NK cells by ADCC antibodies and HIV disease progression 
Antibody-dependent cellular cytotoxicity (ADCC) is of considerable interest as an immune response that may facilitate control of HIV infection. We studied ADCC responses prospectively in a cohort of 79 HIV+ subjects followed for a mean of 2.3 years without antiretroviral therapy. We used a novel assay of the ability of ADCC to activate NK cells, either from the same HIV+ subject or a healthy blood donor. We found ADCC responses to either gp140 Env protein or HIV peptide pools were common in HIV+ subjects when NK cells from the HIV+ subject were used, but did not correlate with markers of HIV disease progression. In contrast, ADCC responses to whole gp140 Env protein were strongly associated with a slower decline in CD4 T cell loss when healthy donor NK cells were used as effectors. Our data had implications for induction of the most effective ADCC responses by HIV vaccines.
PMCID: PMC3175260  PMID: 21792067
HIV; ADCC; NK Cells; CD4 T cells; viral load
3.  HIV Infection Abrogates the Functional Advantage of Natural Killer Cells Educated through KIR3DL1/HLA-Bw4 Interactions To Mediate Anti-HIV Antibody-Dependent Cellular Cytotoxicity 
Journal of Virology  2012;86(8):4488-4495.
Combinations of KIR3DL1 and HLA-Bw4 alleles protect against HIV infection and/or disease progression. These combinations enhance NK cell responsiveness through the ontological process of education. However, educated KIR3DL1+ NK cells do not have enhanced degranulation upon direct recognition of autologous HIV-infected cells. Since antibody-dependent cellular cytotoxicity (ADCC) is associated with improved HIV infection outcomes and NK cells overcome inhibition through killer cell immunoglobulin-like receptors (KIR) to mediate ADCC, we hypothesized that KIR3DL1-educated NK cells mediate anti-HIV ADCC against autologous cells. A whole-blood flow cytometry assay was used to evaluate ADCC-induced activation of NK cells. This assay assessed activation (gamma interferon [IFN-γ] production and/or CD107a expression) of KIR3DL1+ and KIR3DL1− NK cells, from HLA-Bw4+ and HLA-Bw4− HIV-positive and HIV-negative individuals, in response to autologous HIV-specific ADCC targets. KIR3DL1+ NK cells were more functional than KIR3DL1− NK cells from HLA-Bw4+, but not HLA-Bw4−, healthy controls. In HIV-infected individuals, no differences in NK cell functionality were observed between KIR3DL1+ and KIR3DL1− NK cells in HLA-Bw4+ individuals, consistent with dysfunction of NK cells in the setting of HIV infection. Reflecting the partial normalization of NK cell responsiveness following initiation of antiretroviral therapy, a significant correlation was observed between the peripheral CD4+ T-lymphocyte counts in antiretroviral therapy-treated subjects and the functionality of NK cells. However, peripheral CD4+ T-lymphocyte counts were not correlated with an anti-HIV ADCC functional advantage in educated KIR3DL1+ NK cells. The abrogation of the functional advantage of educated NK cells may enhance HIV disease progression. Strategies to enhance the potency of NK cell-mediated ADCC may improve HIV therapies and vaccines.
PMCID: PMC3318670  PMID: 22345455
4.  Influence of Cytokines on HIV-Specific Antibody-Dependent Cellular Cytotoxicity Activation Profile of Natural Killer Cells 
PLoS ONE  2012;7(6):e38580.
There is growing interest in HIV-specific antibody-dependent cellular cytotoxicity (ADCC) as an effective immune response to prevent or control HIV infection. ADCC relies on innate immune effector cells, particularly NK cells, to mediate control of virus-infected cells. The activation of NK cells (i.e., expression of cytokines and/or degranulation) by ADCC antibodies in serum is likely subject to the influence of other factors that are also present. We observed that the HIV-specific ADCC antibodies, within serum samples from a panel of HIV-infected individuals induced divergent activation profiles of NK cells from the same donor. Some serum samples primarily induced NK cell cytokine expression (i.e., IFNγ), some primarily initiated NK cell expression of a degranulation marker (CD107a) and others initiated a similar magnitude of responses across both effector functions. We therefore evaluated a number of HIV-relevant soluble factors for their influence on the activation of NK cells by HIV-specific ADCC antibodies. Key findings were that the cytokines IL-15 and IL-10 consistently enhanced the ability of NK cells to respond to HIV-specific ADCC antibodies. Furthermore, IL-15 was demonstrated to potently activate “educated” KIR3DL1+ NK cells from individuals carrying its HLA-Bw4 ligand. The cytokine was also demonstrated to activate “uneducated” KIR3DL1+ NK cells from HLA-Bw6 homozygotes, but to a lesser extent. Our results show that cytokines influence the ability of NK cells to respond to ADCC antibodies in vitro. Manipulating the immunological environment to enhance the potency of NK cell-mediated HIV-specific ADCC effector functions could be a promising immunotherapy or vaccine strategy.
PMCID: PMC3372512  PMID: 22701674
5.  Antibody-Dependent Cellular Cytotoxicity and NK Cell-Driven Immune Escape in HIV Infection: Implications for HIV Vaccine Development 
Advances in Virology  2012;2012:637208.
The HIV-1 genome is malleable and a difficult target tot vaccinate against. It has long been recognised that cytotoxic T lymphocytes and neutralising antibodies readily select for immune escape HIV variants. It is now also clear that NK cells can also select for immune escape. NK cells force immune escape through both direct Killer-immunoglobulin-like receptor (KIR)-mediated killing as well as through facilitating antibody-dependent cellular cytotoxicity (ADCC). These newer finding suggest NK cells and ADCC responses apply significant pressure to the virus. There is an opportunity to harness these immune responses in the design of more effective HIV vaccines.
PMCID: PMC3350948  PMID: 22611395
6.  Activation of NK Cells by ADCC Responses During Early HIV Infection 
Viral Immunology  2011;24(2):171-175.
Partial control of HIV occurs during acute infection, although the mechanisms responsible are poorly understood. We studied the ability of antibody-dependent cellular cytotoxicity (ADCC) antibodies in serum to activate natural killer (NK) cells in longitudinal samples from 8 subjects with well-defined early HIV infection who controlled viremia to low levels. NK cell activation by ADCC antibodies to gp140 Env proteins was detected in half of the subjects at the first time point studied, a mean of 111 d after the estimated time of infection. In contrast, ADCC-mediated NK cell activation in response to linear HIV peptides evolved more slowly, over the first 2 y of infection. Our studies suggest that HIV-specific ADCC responses to conformational epitopes occur early during acute HIV infection, and broaden to include linear epitopes over time. These findings have implications for the immune control of HIV.
PMCID: PMC3070001  PMID: 21449728
7.  Pol as a target for antibody dependent cellular cytotoxicity responses in HIV-1 infection 
Virology  2011;412(1):110-116.
Antibody-Dependent Cellular Cytotoxicity (ADCC) may assist in preventing HIV or delaying disease progression. Most prior studies have analyzed Env-specific ADCC responses. We hypothesized that effective ADCC-based immunity may target conserved internal viral proteins such as Pol. We analyzed the ability overlapping Pol peptides to induce activation of NK cells via ADCC. We prospectively studied ADCC responses in 83 HIV+ subjects followed for 3 years. Pol peptides were commonly targeted by ADCC responses in these chronically infected subjects (in 32 of the 83 subjects). However, Pol-specific ADCC responses declined over time and did not correlate with delayed HIV progression, measured by either baseline CD4 T cells, CD4 T cell loss over time, baseline viral load or the need to start antiretroviral therapy. Although Pol is frequently targeted by ADCC in HIV+ subjects, the strength or specificity of Pol-specific ADCC responses needs to be modulated to be effective in delaying HIV progression.
PMCID: PMC3056898  PMID: 21269655

Results 1-7 (7)