Increased Natural Killer Cell Activation in HIV-Infected Immunologic Non-Responders Correlates with CD4+ T Cell Recovery after Antiretroviral Therapy and Viral Suppression

RESEARCH ARTICLE Increased Natural Killer Cell Activation in HIVInfected Immunologic Non-Responders Correlates with CD4+ T Cell Recovery after Antiretroviral Therapy and Viral Suppression Zhenwu Luo1, Zhen Li1,2, Lisa Martin3, Zhiliang Hu1,4, Hao Wu2, Zhuang Wan1, Michael Kilby3, Sonya L. Heath5, Lei Huang6*, Wei Jiang1,3* a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 1 Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, United States of America, 2 Beijing You’an Hospital, Capital Medical University, No.8 Xitoutiao, You’an men wai, Fengtai District, Beijing, China, 3 Divison of Infectious Diseases, Department of Medicine, Medical University of South Carolina, Charleston, United States of America, 4 Department of Infectious Disease, the Second Affiliated Hospital of the Southeast University, Nanjing, China, 5 Division of Infectious Diseases, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States of America, 6 The 302 Hospital of PLA, Treatment and Research Center for Infectious Diseases, Beijing, China * (WJ); (LH) OPEN ACCESS Citation: Luo Z, Li Z, Martin L, Hu Z, Wu H, Wan Z, et al. (2017) Increased Natural Killer Cell Activation in HIV-Infected Immunologic Non-Responders Correlates with CD4+ T Cell Recovery after Antiretroviral Therapy and Viral Suppression. PLoS ONE 12(1): e0167640. doi:10.1371/journal. pone.0167640 Editor: Johan K. Sandberg, Karolinska Institutet Department of Medicine Solna, SWEDEN Received: June 22, 2016 Accepted: November 17, 2016 Published: January 11, 2017 Copyright: © 2017 Luo et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and the Supporting Information file. Abstract The role of natural killer (NK) cell function in HIV disease especially in the setting of longterm antiretroviral therapy (ART) and viral suppression is not fully understood. In the current study, we have investigated NK cell activation in healthy controls and aviremic ART-treated HIV+ subjects with different degrees of immune restoration. We performed a cross sectional study in 12 healthy controls and 24 aviremic ART-treated HIV-infected subjects including 13 HIV+ subjects with CD4+ T cells above 500 cells/μL defined as “immunologic responders” and 11 HIV+ subjects with CD4+ T cells below 350 cells/μL defined as “immunologic nonresponders”. We analyzed NK cell number, subset, and activation by expression of CD107a and NKG2D and co-expression of CD38 and HLA-DR. NK cell-mediated cytotoxicity against uninfected CD4+ T cells was tested in vitro. We found that NK cell absolute number, percentage of NK cells, and percentage of NK cell subsets were similar in the three study groups. The increased NK cell activation was found predominantly in CD56dimCD16+ subset of immunologic non-responders but not immunologic responders compared to healthy controls. The activation of NK cells was inversely correlated with the peripheral CD4+ T cell count in HIV+ subjects, even after controlling for chronic T cell activation, sex, and age, potential contributors for CD4+ T cell counts in HIV disease. Interestingly, NK cells from immunologic non-responders mediated cytotoxicity against uninfected CD4+ T cells ex vivo. NK cells may play a role in blunted CD4+ T cell recovery in ART-treated HIV disease. Funding: This work was supported by NIH grants AI091526 (Wei Jiang), the University of Alabama at Birmingham, Center for AIDS Research P30 AI027767 (Sonya Heath), and the 12th Five Year Research Project of People’s Liberation Army (CWS11J160) (Lei Huang). The funders had no role in study design, data collection and analysis, PLOS ONE | DOI:10.1371/journal.pone.0167640 January 11, 2017 1 / 17 NK Cells in HIV Disease decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Introduction Antiretroviral therapy (ART) dramatically suppresses HIV viral replication, improves immune function, restores CD4+ T cells, increases survival, and delays disease progression in HIV disease [1–3]. However, up to 25% patients fail to reconstitute their CD4+ T cells to the levels similar to healthy controls despite HIV suppression under ART treatment [2, 4, 5]. Inflammatory syndrome, heightened morbidity and mortality, are seen in persons who fail to increase their CD4 + T cell counts under ART treatment [3, 6–10]. Patients under viral-suppressive ART treatment with peripheral CD4+ T cell counts > 500 cells/μl are defined as “immunologic responders” and patients under viral-suppressive ART treatment with peripheral CD4+ T cell counts  350 cells/ μl are defined as “immunologic non-responders” [11–13]. The mechanisms of incomplete CD4 + T cell restoration have been extensively studied, including thymic and lymphoid fibrosis, low nadir CD4+ T cell counts, heightened microbial translocation and inflammation, high T cell activation, and virus-mediated cytopathogenicity [14–23]; but are still not fully understood. Chronic T cell activation is a predictive marker for peripheral CD4+ T cell count and disease progression in HIV disease [24–26]. Although ART treatment significantly decreases chronic T cell activation, residual activation persists even after many years of ART treatment [27, 28]. The magnitude of T cell activation in this setting is associated with the degrees of CD4+ T cell recovery [29]. Natural killer (NK) cells are a subset of granular lymphocytes that are critical in the innate immunity against infection [30]. They are capable to kill infected cells through cytolysis [31]. Moreover, NK cell mediated antibody-dependent cellular cytotoxicity (ADCC) has been associated with protection from infection and disease progression [32], and is an important mechanism to control HIV infection [33–35]. Human NK cells are commonly defined to two subsets, CD56dimCD16+ and CD56brightCD16− subpopulations [36]. CD56dimCD16+ NK cells predominate in the peripheral blood, and CD56brightCD16− NK cells constitute the majority of NK cells in secondary lymphoid tissues [36]. Chronic HIV infection is associated with reduced proportion and absolute number of CD3−CD56+ NK cells compared to healthy controls [37, 38], as well as increased proportion of CD56dimCD16+ NK cell subset [39, 40]. These alterations of NK cells are largely associated with HIV viral replication in ART-naïve patients [41]. Several markers are associated with NK cell activation and cytolytic function. For example, co-expression of CD38 and HLA-DR is an activation marker on NK cells [42]. CD107a is a marker of lysosomal granule exocytosis [43]. Upon antibody-mediated NK cell activation, CD107a expression increases and mediates cytoly (...truncated)