Galit Alter

Publications of Galit Alter

• A 17q12 allele is associated with altered NK cell subsets and function.

  Authors: Zongqi Xia, Qingquan Liu, Christoph T Berger, Brendan T Keenan, Anna Kaliszewska, Patrick C Cheney, Gyan P Srivastava, Irene Wood Castillo, Philip L De Jager, Galit Alter

  Journal of immunology (Baltimore, Md. : 1950). 02/2012; 188(7):3315-22.

  NK cells play an important role in innate immunity. A previous genome-wide association study demonstrated an association between a 17q12 allele (rs9916629(C)) and lower frequency of CD3(-)CD56(+) NKNK cells play an important role in innate immunity. A previous genome-wide association study demonstrated an association between a 17q12 allele (rs9916629(C)) and lower frequency of CD3(-)CD56(+) NK cells in peripheral blood. We performed an analysis that not only replicates the original result of the genome-wide association study (p = 0.036) but also defines the specific cell subpopulations and functions that are modulated by the rs9916629 polymorphism in a cohort of 96 healthy adult subjects using targeted multiparameter flow cytometric profiling of NK cell phenotypes and functions. We found that rs9916629(C) is associated with alterations in specific NK cell subsets, including lower frequency of predominantly cytotoxic CD56(dim) NK cells (p = 0.011), higher frequency of predominantly regulatory CD56(bright) NK cells (p = 0.019), and a higher proportion of NK cells expressing the inhibitory NKG2A receptor (p = 0.0002). Functionally, rs9916629(C) is associated with decreased secretion of macrophage inflammatory protein-1β by NK cells in the context of Ab-dependent cell-mediated cytotoxicity (p = 0.039) and increased degranulation in response to MHC class I-deficient B cells (p = 0.017). Transcriptional profiling of NK cells suggests that rs9916629 influences the expression of transcription factors such as TBX21, which has a role in NK cell differentiation, offering a possible mechanism for the phenotypic and functional differences between the different alleles. The rs9916629(C) allele therefore has a validated effect on the proportion of NK cells in peripheral blood and skews NK cells toward a specific phenotypic and functional profile, potentially influencing the impact that these innate immune cells have on infection and autoimmunity.

• KIR/HLA: genetic clues for a role of NK cells in the control of HIV.

  Authors: Lena Fadda, Galit Alter

  Advances in experimental medicine and biology. 01/2012; 780:27-36.

  Early events following HIV infections determine the course of disease progression. Mounting evidence suggests that antiviral immune responses induced soon after infection, prior to the induction ofEarly events following HIV infections determine the course of disease progression. Mounting evidence suggests that antiviral immune responses induced soon after infection, prior to the induction of adaptive immune responses, are key to early control of viral infection. Among the early innate immune effector cells, natural killer (NK) cells represent a unique subset of lymphoctyes that do not express an antigen specific receptor. Rather, these cells integrate signals from an arsenal of non-specific inhibitory and activating receptors that are expressed on their cell surface. As such, these cells are classified as cells of the innate immune system, and they are able to lyse certain tumor targets and infected cells without the need for prior antigen sensitization. Over the past decade, accumulating evidence suggests that these innate lymphocytes may not be as innate as once believed, but that individual NK cell clones may show some target cell specificity, and play a critical early role following infection with HIV.

• Correction: Copy Number Variation of KIR Genes Influences HIV-1 Control.

  Authors: Kimberly Pelak, Anna C Need, Jacques Fellay, Kevin V Shianna, Sheng Feng, Thomas J Urban, Dongliang Ge, Andrea De Luca, Javier Martinez-Picado, Steven M Wolinsky [......] Jay H Bream, Maureen P Martin, Persephone Borrow, Norman L Letvin, Andrew J McMichael, Barton F Haynes, Amalio Telenti, Mary Carrington, David B Goldstein, Galit Alter

  PLoS biology. 12/2011; 9(12).

  [This corrects the article on p. e1001208 in vol. 9.].

• Copy number variation of KIR genes influences HIV-1 control.

  Authors: Kimberly Pelak, Anna C Need, Jacques Fellay, Kevin V Shianna, Sheng Feng, Thomas J Urban, Dongliang Ge, Andrea De Luca, Javier Martinez-Picado, Steven M Wolinsky [......] Jay H Bream, Maureen P Martin, Persephone Borrow, Norman L Letvin, Andrew J McMichael, Barton F Haynes, Amalio Telenti, Mary Carrington, David B Goldstein, Galit Alter

  PLoS biology. 11/2011; 9(11):e1001208.

  A genome-wide screen for large structural variants showed that a copy number variant (CNV) in the region encoding killer cell immunoglobulin-like receptors (KIR) associates with HIV-1 control asA genome-wide screen for large structural variants showed that a copy number variant (CNV) in the region encoding killer cell immunoglobulin-like receptors (KIR) associates with HIV-1 control as measured by plasma viral load at set point in individuals of European ancestry. This CNV encompasses the KIR3DL1-KIR3DS1 locus, encoding receptors that interact with specific HLA-Bw4 molecules to regulate the activation of lymphocyte subsets including natural killer (NK) cells. We quantified the number of copies of KIR3DS1 and KIR3DL1 in a large HIV-1 positive cohort, and showed that an increase in KIR3DS1 count associates with a lower viral set point if its putative ligand is present (p = 0.00028), as does an increase in KIR3DL1 count in the presence of KIR3DS1 and appropriate ligands for both receptors (p = 0.0015). We further provide functional data that demonstrate that NK cells from individuals with multiple copies of KIR3DL1, in the presence of KIR3DS1 and the appropriate ligands, inhibit HIV-1 replication more robustly, and associated with a significant expansion in the frequency of KIR3DS1+, but not KIR3DL1+, NK cells in their peripheral blood. Our results suggest that the relative amounts of these activating and inhibitory KIR play a role in regulating the peripheral expansion of highly antiviral KIR3DS1+ NK cells, which may determine differences in HIV-1 control following infection.

• HIV-1 adaptation to NK-cell-mediated immune pressure.

  Authors: Galit Alter, David Heckerman, Arne Schneidewind, Lena Fadda, Carl M Kadie, Jonathan M Carlson, Cesar Oniangue-Ndza, Maureen Martin, Bin Li, Salim I Khakoo, Mary Carrington, Todd M Allen, Marcus Altfeld

  Nature. 08/2011; 476(7358):96-100.

  Natural killer (NK) cells have an important role in the control of viral infections, recognizing virally infected cells through a variety of activating and inhibitory receptors. Epidemiological andNatural killer (NK) cells have an important role in the control of viral infections, recognizing virally infected cells through a variety of activating and inhibitory receptors. Epidemiological and functional studies have recently suggested that NK cells can also contribute to the control of HIV-1 infection through recognition of virally infected cells by both activating and inhibitory killer immunoglobulin-like receptors (KIRs). However, it remains unknown whether NK cells can directly mediate antiviral immune pressure in vivo in humans. Here we describe KIR-associated amino-acid polymorphisms in the HIV-1 sequence of chronically infected individuals, on a population level. We show that these KIR-associated HIV-1 sequence polymorphisms can enhance the binding of inhibitory KIRs to HIV-1-infected CD4(+) T cells, and reduce the antiviral activity of KIR-positive NK cells. These data demonstrate that KIR-positive NK cells can place immunological pressure on HIV-1, and that the virus can evade such NK-cell-mediated immune pressure by selecting for sequence polymorphisms, as was previously described for virus-specific T cells and neutralizing antibodies. NK cells might therefore have a previously underappreciated role in contributing to viral evolution.

• Decreased Fc receptor expression on innate immune cells is associated with impaired antibody-mediated cellular phagocytic activity in chronically HIV-1 infected individuals.

  Authors: Anne-Sophie Dugast, Andrew Tonelli, Christoph T Berger, Margaret E Ackerman, Gaia Sciaranghella, Qingquan Liu, Magdalena Sips, Ildiko Toth, Alicja Piechocka-Trocha, Musie Ghebremichael, Galit Alter

  Virology. 07/2011; 415(2):160-7.

  In addition to neutralization, antibodies mediate other antiviral activities including antibody-dependent cellular phagocytosis (ADCP), antibody-dependent cellular cytotoxicity (ADCC), as well asIn addition to neutralization, antibodies mediate other antiviral activities including antibody-dependent cellular phagocytosis (ADCP), antibody-dependent cellular cytotoxicity (ADCC), as well as complement deposition. While it is established that progressive HIV infection is associated with reduced ADCC and ADCP, the underlying mechanism for this loss of function is unknown. Here we report considerable changes in FcR expression over the course of HIV infection on both mDCs and monocytes, including elevated FcγRI expression in acute HIV infection and reduced expression of FcγRII and FcγRIIIa in chronic HIV infection. Furthermore, selective blockade of FcγRII alone was associated with a loss in ADCP activity, suggesting that FcγRII plays a central role in modulating ADCP. Overall, HIV infection is associated with a number of changes in FcR expression on phagocytic cells that are associated with changes in their ability to respond to antibody-opsonized targets, potentially contributing to a failure in viral clearance in progressive HIV-1 infection.

• Early viral replication in lymph nodes provides HIV with a means by which to escape NK-cell-mediated control.

  Authors: Rutger Luteijn, Gaia Sciaranghella, Jan van Lunzen, Anne Nolting, Anne-Sophie Dugast, Musie S Ghebremichael, Marcus Altfeld, Galit Alter

  European journal of immunology. 06/2011; 41(9):2729-40.

  Acute HIV infection is marked by dramatic viral replication associated with preferential replication within secondary lymphoid tissues, such as lymph nodes (LNs), that is rapidly but incompletelyAcute HIV infection is marked by dramatic viral replication associated with preferential replication within secondary lymphoid tissues, such as lymph nodes (LNs), that is rapidly but incompletely contained to a viral setpoint. Accumulating evidence supports a role for natural killer (NK) cells in the early control of HIV infection; however, little is known about the location of their antiviral control. Given that HIV replicates profusely in LNs during early infection, we sought to define whether changes occurred in the NK cell infiltrate within these sites during the first year of HIV infection. Surprisingly, NK cell numbers and distribution were unaltered during early HIV infection. LN NK cells expressed decreased inhibitory receptors, were more highly activated, and expressed elevated TRAIL, potentially conferring a superior capacity for NK cells to become activated and control infection. Most noticeably, KIR(+) NK cells were rarely detected in the LN during HIV infection, associated with diminished migratory capacity in the setting of reduced expression of CX3CR1 and CXCR1. Thus, incomplete control of HIV viral replication during early disease may be due to the inefficient recruitment of KIR(+) NK cells to this vulnerable site, providing HIV a niche where it can replicate unabated by early NK-cell-mediated innate pressure.

• Correction: Characteristics of the Earliest Cross-Neutralizing Antibody Response to HIV-1.

  Authors: Iliyana Mikell, D Noah Sather, Spyros A Kalams, Marcus Altfeld, Galit Alter, Leonidas Stamatatos

  PLoS pathogens. 03/2011; 7(3).

  [This corrects the article on p. e1001251 in vol. 7.].

• Mutiny or scrutiny: NK cell modulation of DC function in HIV-1 infection.

  Authors: Galit Alter, Marcus Altfeld

  Trends in immunology. 03/2011; 32(5):219-24.

  Accumulating data suggest that natural killer (NK) cells are involved not only in the innate antiviral response following infection, but also in shaping the quality of the adaptive immune response byAccumulating data suggest that natural killer (NK) cells are involved not only in the innate antiviral response following infection, but also in shaping the quality of the adaptive immune response by modulating the functional properties of myeloid dendritic cells (DC) during the acute immune response to infection. In this role, NK cells ensure that only fully mature, immunogenic DCs gain access to inductive sites, where they might prime effective antiviral adaptive immune responses. However, increasing evidence now suggests that several aspects of this cross-talk between NK cells and DCs are compromised during HIV infection, potentially contributing to immune dysfunction.

• Natural killer cells in spontaneous control of HIV infection.

  Authors: Christoph T Berger, Galit Alter

  Current opinion in HIV and AIDS. 03/2011; 6(3):208-13.

  Over the last decade our understanding of the role of natural killer cells in HIV infection has changed dramatically due to strong epidemiological, phenotypic, and functional data providing evidenceOver the last decade our understanding of the role of natural killer cells in HIV infection has changed dramatically due to strong epidemiological, phenotypic, and functional data providing evidence for their involvement in antiviral control. Here we review the current literature on natural killer cells in the control of HIV infection, with a specific focus on their role in HIV controllers, individuals that spontaneously control HIV replication in the absence of antiretroviral therapy. Differences between progressors and controllers are highlighted in the context of genetic influences, natural killer cell phenotypes, function and dysregulation. Also, recent findings on the role of natural killer cell-mediated antibody-dependent cellular cytotoxicity in HIV control are summarized. This evolving understanding of the complex biology of natural killer cells and their multifaceted role in HIV infection offer exciting new approaches for future vaccine strategies. Furthermore, the specific natural killer cell phenotype and function observed in controllers may guide new vaccine modalities that specifically harness the antiviral power of natural killer cells as adjuvants, or as direct effectors.

• KIR polymorphisms modulate peptide-dependent binding to an MHC class I ligand with a Bw6 motif.

  Authors: Arnaud D Colantonio, Benjamin N Bimber, William J Neidermyer, R Keith Reeves, Galit Alter, Marcus Altfeld, R Paul Johnson, Mary Carrington, David H O'Connor, David T Evans

  PLoS pathogens. 03/2011; 7(3):e1001316.

  Molecular interactions between killer immunoglobulin-like receptors (KIRs) and their MHC class I ligands play a central role in the regulation of natural killer (NK) cell responses to viral pathogensMolecular interactions between killer immunoglobulin-like receptors (KIRs) and their MHC class I ligands play a central role in the regulation of natural killer (NK) cell responses to viral pathogens and tumors. Here we identify Mamu-A1*00201 (Mamu-A*02), a common MHC class I molecule in the rhesus macaque with a canonical Bw6 motif, as a ligand for Mamu-KIR3DL05. Mamu-A1*00201 tetramers folded with certain SIV peptides, but not others, directly stained primary NK cells and Jurkat cells expressing multiple allotypes of Mamu-KIR3DL05. Differences in binding avidity were associated with polymorphisms in the D0 and D1 domains of Mamu-KIR3DL05, whereas differences in peptide-selectivity mapped to the D1 domain. The reciprocal exchange of the third predicted MHC class I-contact loop of the D1 domain switched the specificity of two Mamu-KIR3DL05 allotypes for different Mamu-A1*00201-peptide complexes. Consistent with the function of an inhibitory KIR, incubation of lymphocytes from Mamu-KIR3DL05(+) macaques with target cells expressing Mamu-A1*00201 suppressed the degranulation of tetramer-positive NK cells. These observations reveal a previously unappreciated role for D1 polymorphisms in determining the selectivity of KIRs for MHC class I-bound peptides, and identify the first functional KIR-MHC class I interaction in the rhesus macaque. The modulation of KIR-MHC class I interactions by viral peptides has important implications to pathogenesis, since it suggests that the immunodeficiency viruses, and potentially other types of viruses and tumors, may acquire changes in epitopes that increase the affinity of certain MHC class I ligands for inhibitory KIRs to prevent the activation of specific NK cell subsets.

• Emerging concepts on the role of innate immunity in the prevention and control of HIV infection.

  Authors: Margaret E Ackerman, Anne-Sophie Dugast, Galit Alter

  Annual review of medicine. 01/2011; 63:113-30.

  While neutralizing antibodies can provide sterilizing protection from HIV infection via their variable domains, the antibody constant domain provides a functional link between innate and adaptiveWhile neutralizing antibodies can provide sterilizing protection from HIV infection via their variable domains, the antibody constant domain provides a functional link between innate and adaptive immunity and offers a means to harness the potent antiviral properties of a wide spectrum of innate immune effector cells. There has been a growing appreciation of the role of these effector mechanisms across fields from cancer immunotherapy to autoimmunity and infectious disease, as well as speculation that this mechanism may be responsible for the protection observed in the RV144 HIV vaccine trial. This review summarizes these extraneutralizing humoral immune activities, progress in defining the importance of these effector mechanisms during progression in HIV infection, and the potential impact that such vaccine-induced immune responses may have on protection from infection.

• Expansion of 2B4+ natural killer (NK) cells and decrease in NKp46+ NK cells in response to influenza.

  Authors: Stephanie Jost, Jeff Reardon, Eric Peterson, Danielle Poole, Ronald Bosch, Galit Alter, Marcus Altfeld

  Immunology. 01/2011; 132(4):516-26.

  Several studies have highlighted the importance of murine natural killer (NK) cells in the control of influenza virus infection, notably through the natural cytotoxicity receptor NKp46. However,Several studies have highlighted the importance of murine natural killer (NK) cells in the control of influenza virus infection, notably through the natural cytotoxicity receptor NKp46. However, little is known about the involvement of NK cells in human influenza infection. Here, we show that upon in vitro exposure to influenza, NKp46 expression on NK cells decreases, whereas expression of 2B4, an activating receptor that can enhance natural cytotoxicity in synergy with NKp46, is up-regulated. Consistent with these observations, NKp46(dull) and 2B4(bright) NK cells had a higher functional activity in response to influenza than NK cells expressing high levels of NKp46 or low levels of 2B4, respectively. Importantly, we assessed whether the expression of these receptors was also modified in vivo in response to influenza antigens and showed that an increase in 2B4-expressing NK cells and a decrease in NKp46(+) NK cells occurred following intramuscular influenza vaccination. Altogether, our results further suggest that NKp46 may play an important role in the innate immune response to human influenza and reveal that exposure to influenza antigens is associated with a previously unrecognized increase in 2B4 expression that can impact NK cell activity against the virus.

• Characteristics of the earliest cross-neutralizing antibody response to HIV-1.

  Authors: Iliyana Mikell, D Noah Sather, Spyros A Kalams, Marcus Altfeld, Galit Alter, Leonidas Stamatatos

  PLoS pathogens. 01/2011; 7(1):e1001251.

  Recent cross-sectional analyses of HIV-1+ plasmas have indicated that broadly cross-reactive neutralizing antibody responses are developed by 10%-30% of HIV-1+ subjects. The timing of the initialRecent cross-sectional analyses of HIV-1+ plasmas have indicated that broadly cross-reactive neutralizing antibody responses are developed by 10%-30% of HIV-1+ subjects. The timing of the initial development of such anti-viral responses is unknown. It is also unknown whether the emergence of these responses coincides with the appearance of antibody specificities to a single or multiple regions of the viral envelope glycoprotein (Env). Here we analyzed the cross-neutralizing antibody responses in longitudinal plasmas collected soon after and up to seven years after HIV-1 infection. We find that anti-HIV-1 cross-neutralizing antibody responses first become evident on average at 2.5 years and, in rare cases, as early as 1 year following infection. If cross-neutralizing antibody responses do not develop during the first 2-3 years of infection, they most likely will not do so subsequently. Our results indicate a potential link between the development of cross-neutralizing antibody responses and specific activation markers on T cells, and with plasma viremia levels. The earliest cross-neutralizing antibody response targets a limited number of Env regions, primarily the CD4-binding site and epitopes that are not present on monomeric Env, but on the virion-associated trimeric Env form. In contrast, the neutralizing activities of plasmas from subjects that did not develop cross-neutralizing antibody responses target epitopes on monomeric gp120 other than the CD4-BS. Our study provides information that is not only relevant to better understanding the interaction of the human immune system with HIV but may guide the development of effective immunization protocols. Since antibodies to complex epitopes that are present on the virion-associated envelope spike appear to be key components of earliest cross-neutralizing activities of HIV-1+ plasmas, then emphasis should be made to elicit similar antibodies by vaccination.

• Determining the phagocytic activity of clinical antibody samples.

  Authors: Elizabeth G McAndrew, Anne-Sophie Dugast, Anna F Licht, Justin R Eusebio, Galit Alter, Margaret E Ackerman

  Journal of visualized experiments : JoVE. 01/2011;

  Antibody-driven phagocytosis is induced via the engagement of Fc receptors on professional phagocytes, and can contribute to both clearance as well as pathology of disease. While the properties ofAntibody-driven phagocytosis is induced via the engagement of Fc receptors on professional phagocytes, and can contribute to both clearance as well as pathology of disease. While the properties of the variable domains of antibodies have long been considered critical to in vivo function, the ability of antibodies to recruit innate immune cells via their Fc domains has become increasingly appreciated as a major factor in their efficacy, both in the setting of recombinant monoclonal antibody therapy, as well as in the course of natural infection or vaccination(1-3). Importantly, despite its nomenclature as a constant domain, the antibody Fc domain does not have constant function, and is strongly modulated by IgG subclass (IgG1-4) and glycosylation at Asparagine 297(4-6). Thus, this method to study functional differences of antigen-specific antibodies in clinical samples will facilitate correlation of the phagocytic potential of antibodies to disease state, susceptibility to infection, progression, or clinical outcome. Furthermore, this effector function is particularly important in light of the documented ability of antibodies to enhance infection by providing pathogens access into host cells via Fc receptor-driven phagocytosis(7). Additionally, there is some evidence that phagocytic uptake of immune complexes can impact the Th1/Th2 polarization of the immune response(8). Here, we describe an assay designed to detect differences in antibody-induced phagocytosis, which may be caused by differential IgG subclass, glycan structure at Asn297, as well as the ability to form immune complexes of antigen-specific antibodies in a high-throughput fashion. To this end, 1 μm fluorescent beads are coated with antigen, then incubated with clinical antibody samples, generating fluorescent antigen specific immune complexes. These antibody-opsonized beads are then incubated with a monocytic cell line expressing multiple FcγRs, including both inhibitory and activating. Assay output can include phagocytic activity, cytokine secretion, and patterns of FcγRs usage, and are determined in a standardized manner, making this a highly useful system for parsing differences in this antibody-dependent effector function in both infection and vaccine-mediated protection(9).

• Reduced frequencies of NKp30+NKp46+, CD161+, and NKG2D+ NK cells in acute HCV infection may predict viral clearance.

  Authors: Galit Alter, Stephanie Jost, Suzannah Rihn, Laura L Reyor, Brian E Nolan, Musie Ghebremichael, Ronald Bosch, Marcus Altfeld, Georg M Lauer

  Journal of hepatology. 12/2010; 55(2):278-88.

  While the majority of HCV-infected patients progress to chronic hepatitis, a small fraction of individuals are able to clear the virus. Resolution of infection occurs within the first few weeks toWhile the majority of HCV-infected patients progress to chronic hepatitis, a small fraction of individuals are able to clear the virus. Resolution of infection occurs within the first few weeks to months of infection, suggesting that innate immune functions may be critical for early control. Epidemiologic data support a role for particular NK cell receptor bearing populations in this control, yet the mechanism by which NK cells respond to HCV early in infection is unknown. Changes in the phenotype and function of NK cells were investigated in a cohort of 43 individuals identified during various stages of HCV infection with different clinical outcomes. Acute, chronic, and resolved HCV infections were characterized by an expansion of CD56(neg) NK cells. Furthermore, increased levels of HLA-C-binding KIR(+) NK cells were observed in HCV resolvers, while all stages of HCV infection were associated with reduced percentages of NKG2D(+), NKp30(+), and NKp46(+) NK cells, and a slight increase in the ability of NK cells to respond to target cells bearing the ligands for these receptors. In contrast, NKG2A(+) and CD94(+) NK cells were elevated in acute and chronic HCV infection, but not in resolved infection. Most importantly, in acute infection, lower frequencies of NKp30(+), NKp46(+), CD161(+), and NKG2D(+) NK cells were observed in patients who were subsequently able to clear HCV infection than in those becoming chronically infected. These data implicate particular populations of NK cells in the early control and clearance of HCV infection.

• A robust, high-throughput assay to determine the phagocytic activity of clinical antibody samples.

  Authors: Margaret E Ackerman, Brian Moldt, Richard T Wyatt, Anne-Sophie Dugast, Elizabeth McAndrew, Stephen Tsoukas, Stephanie Jost, Christoph T Berger, Gaia Sciaranghella, Qingquan Liu, Darrell J Irvine, Dennis R Burton, Galit Alter

  Journal of immunological methods. 12/2010; 366(1-2):8-19.

  Phagocytosis can be induced via the engagement of Fcγ receptors by antibody-opsonized material. Furthermore, the efficiency of antibody-induced effector functions has been shown to be dramaticallyPhagocytosis can be induced via the engagement of Fcγ receptors by antibody-opsonized material. Furthermore, the efficiency of antibody-induced effector functions has been shown to be dramatically modulated by changes in antibody glycosylation. Because infection can modulate antibody glycans, which in turn modulate antibody functions, assays capable of determining the induction of effector functions rather than neutralization or titer provide a valuable opportunity to more fully characterize the quality of the adaptive immune response. Here we describe a robust and high-throughput flow cytometric assay to define the phagocytic activity of antigen-specific antibodies from clinical samples. This assay employs a monocytic cell line that expresses numerous Fc receptors: including inhibitory and activating, and high and low affinity receptors--allowing complex phenotypes to be studied. We demonstrate the adaptability of this high-throughput, flow-based assay to measure antigen-specific antibody-mediated phagocytosis against an array of viruses, including influenza, HIV, and dengue. The phagocytosis assay format further allows for simultaneous analysis of cytokine release, as well as determination of the role of specific Fcγ-receptor subtypes, making it a highly useful system for parsing differences in the ability of clinical and vaccine induced antibody samples to recruit this critical effector function.

• The humoral response to HIV-1: new insights, renewed focus.

  Authors: Galit Alter, M Anthony Moody

  The Journal of infectious diseases. 10/2010; 202 Suppl 2:S315-22.

  During the past 2 decades, significant advances in our understanding of the humoral immune response to human immunodeficiency virus type 1 (HIV-1) infection have been made, yet a tremendous amount ofDuring the past 2 decades, significant advances in our understanding of the humoral immune response to human immunodeficiency virus type 1 (HIV-1) infection have been made, yet a tremendous amount of work lies ahead. Despite these advances, strategies to reliably induce antibodies that can control HIV-1 infection are still critically needed. However, recent advances in our understanding of the kinetics, specificity, and function of early humoral responses offer alternative new approaches to attain this goal. These results, along with the new broadly neutralizing antibody specificities, the role for other antibody functions, the increased understanding of HIV-1-induced changes to B cell biology, and results from the RV144 "Thai" trial showing potential modest sterilizing protection by nonneutralizing antibody responses, have renewed focus on the humoral system. In this review, recent advances in our understanding of the earliest humoral responses are discussed, highlighting presentations from the meeting on the Biology of Acute HIV Infection.

• MHC class I chain-related protein A shedding in chronic HIV-1 infection is associated with profound NK cell dysfunction.

  Authors: Anne Nolting, Anne-Sophie Dugast, Suzannah Rihn, Rutger Luteijn, Mary F Carrington, Katherine Kane, Stephanie Jost, Ildiko Toth, Ellen Nagami, Gerd Faetkenheuer, Pia Hartmann, Marcus Altfeld, Galit Alter

  Virology. 10/2010; 406(1):12-20.

  Natural killer (NK) cells play a critical role in host defense against viral infections. However chronic HIV-1 infection is associated with an accumulation of dysfunctional NK cells, that poorlyNatural killer (NK) cells play a critical role in host defense against viral infections. However chronic HIV-1 infection is associated with an accumulation of dysfunctional NK cells, that poorly control viral replication. The underlying mechanisms for this NK cell mediated dysfunction are not understood. Certain tumors evade NK cell mediated detection by dampening NK cell activity through the downregulation of NKG2D, via the release of soluble NKG2D-ligands, resulting in a potent suppression of NK cell function. Here we show that chronic HIV-1 infection is associated with a specific defect in NKG2D-mediated NK cell activation, due to reduced expression and transcription of NKG2D. Reduced NKG2D expression was associated with elevated levels of the soluble form of the NKG2D-ligand, MICA, in patient sera, likely released by HIV+CD4+ T cells. Thus, like tumors, HIV-1 may indirectly suppress NK cell recognition of HIV-1-infected CD4+ T cells by enhancing NKG2D-ligand secretion into the serum resulting in a profound impairment of NK cell function.

• IL-10 induces aberrant deletion of dendritic cells by natural killer cells in the context of HIV infection.

  Authors: Galit Alter, Daniel Kavanagh, Suzannah Rihn, Rutger Luteijn, David Brooks, Michael Oldstone, Jan van Lunzen, Marcus Altfeld

  The Journal of clinical investigation. 06/2010; 120(6):1905-13.

  Persistent levels of IL-10 play a central role in progressive immune dysfunction associated with chronic viral infections such as HIV, but the underlying mechanisms are poorly understood. BecausePersistent levels of IL-10 play a central role in progressive immune dysfunction associated with chronic viral infections such as HIV, but the underlying mechanisms are poorly understood. Because IL-10 affects the phenotypic and functional properties of DCs, which are responsible for initiating adaptive immune responses, we investigated whether IL-10 induces changes in DC phenotype and function in the context of HIV infection. Here, we show that IL-10 treatment of immature and mature human DCs in culture induced contrasting phenotypic changes in these populations: immature DCs exhibited aberrant resistance to NK cell-mediated elimination, whereas mature DCs exhibited increased susceptibility to NKG2D-dependent NK elimination. Treatment of immature and mature DCs with HIV resulted in potent IL-10 secretion and the same phenotypic and functional changes observed in the IL-10-treated cells. Consistent with these in vitro data, LNs isolated from individuals infected with HIV exhibited aberrant accumulation of a partially "immature" DC population. Together, these data suggest that the progressive immune dysfunction observed in chronic viral infections might be caused in part by IL-10-induced reversal of DC susceptibility to NK cell-mediated elimination, resulting in the accumulation of poorly immunogenic DCs in LNs, the sites of adaptive immune response induction.