Abstract Idiopathic CD4 lymphocytopenia (ICL) is a syndrome of unknown etiology characterized by low peripheral CD4 T cell counts and susceptibility to opportunistic infections. One hypothesis for its etiology is trapping of T cells in effector sites. 11 ICL patients and 16 healthy controls (HC) underwent colonic biopsies for CD3, CD4, and CD8 T cell enumeration by flow cytometry (FC) and immunohistochemistry (IHC) in lamia propria (LP). Mucosal IL17+ CD4 T cells were assessed after PMA/ionomycin stimulation. Plasma levels of LPS (for microbial translocation), I-FABP (for gut epithelial integrity), sCD14 (for monocyte activation), D-dimer (for coagulation) and CRP, IL-6 and TNFalpha (for inflammation) were tested in 33 ICL patients and 44 HC. ICL patients had fewer CD3 (2.84-fold, P=0.0080), CD4 (3.04-fold, P=0.013) and CD8 (2.28-fold, P=0.043) T cells in the colonic mucosa compared to HC by FC and fewer CD3 (2.31-fold, P=0.036) and CD4 (3.81-fold, P=0.0003) T cells in LP by IHC. The proportion of IL-17+ CD4 T cells was higher in ICL compared to HC (6.04 vs 3.35%, P=0.013). Levels of sCD14 levels were slightly higher in ICL than in HC (1.42 vs 1.21 µg/ml, P=0.003). Levels of LPS, I-FABP, IL-6, TNFalpha, D-Dimer, and CRP levels were not significantly different between ICL and HC (all P>0.05). These data suggest that colonic mucosal lymphopenia accompanies peripheral T cell lymphopenia in ICL, albeit with preserved gut epithelial integrity and a lack of systemic inflammation.
HIV infection is characterized by a brisk immune activation that plays an important role in the CD4 depletion and immune dysfunction of patients with AIDS. The mechanism underlying this activation is poorly understood. In the current study, we tested the hypothesis that this activation is the net product of two distinct pathways: the inflammatory response to HIV infection and the homeostatic response to CD4 T cell depletion. Using ex vivo BrdU incorporation of PBMCs from 284 patients with different stages of HIV infection, we found that CD4 proliferation was better predicted by the combination of CD4 depletion and HIV viral load (R(2) = 0.375, P < 0.001) than by either parameter alone (CD4 T cell counts, R(2) = 0.202, P < 0.001; HIV viremia, R(2) = 0.302, P < 0.001). Interestingly, CD8 T cell proliferation could be predicted by HIV RNA levels alone (R(2) = 0.334, P < 0.001) and this predictive value increased only slightly (R(2) = 0.346, P < 0.001) when CD4 T cell depletion was taken into account. Consistent with the hypothesis that CD4 T cell proliferation is driven by IL-7 as a homeostatic response to CD4 T cell depletion, levels of phosphorylated STAT-5 were found to be elevated in naive subsets of CD4 and CD8 T cells from patients with HIV infection and in the central memory subset of CD4 T cells. Taken together these data demonstrate that at least two different pathways lead to immune activation of T cells in patients with HIV infection and these pathways differentially influence CD4 and CD8 T cell subsets.
Abstract Immune activation plays an important role in the pathogenesis of HIV disease. Although the causes are not fully understood, the forces that lead to immune dysfunction differ for CD4 and CD8 T cells. In this study, we report that the molecular pathways that drive immune activation during chronic HIV infection are influenced by differences in the homeostatic regulation of the CD4 and CD8 T cell pools. Proliferation of CD4 T cells is controlled more tightly by CD4 T cell numbers than is CD8 T cell proliferation. This difference reflects the importance of maintaining a polyclonal CD4 T cell pool in host surveillance. Both pools of T cells were found to be driven by viral load and its associated state of inflammation. In the setting of HIV-induced lymphopenia, naive CD4 T cells were recruited mainly into the proliferating pool in response to CD4 T cell depletion, whereas naive CD8 T cell proliferation was driven mainly by levels of HIV RNA. RNA analysis revealed increased expression of genes associated with type I IFN and common γ chain cytokine signaling in CD4 T cell subsets and only type I IFN-associated genes in CD8 T cell subsets. In vitro studies demonstrated enhanced STAT1 phosphorylation in response to IFN-α and increased expression of the IFNAR1 transcripts in naive and memory CD4 T cells compared with that observed in CD8 T cells. CD4 T cell subsets also showed enhanced STAT1 phosphorylation in response to exogenous IL-7.
Idiopathic CD4 lymphocytopenia (ICL) is a clinical syndrome that is defined by CD4 lymphopenia of less than 300 cells per cubic millimeter in the absence of any primary or acquired cause of immunodeficiency. Some 30 years after its original identification, ICL has remained a disease of obscure cause, with limited evidence with respect to its prognosis or management, despite diagnostic and therapeutic innovations. We evaluated the clinical, genetic, immunologic, and prognostic characteristics of 108 patients who were enrolled during an 11-year period. We performed whole-exome and targeted gene sequencing to identify genetic causes of lymphopenia. We also performed longitudinal linear mixed-model analyses of T-cell count trajectories and evaluated predictors of clinical events, the response to immunization against coronavirus disease 2019 (Covid-19), and mortality. After the exclusion of patients with genetic and acquired causes of CD4 lymphopenia, the study population included 91 patients with ICL during 374 person-years of follow-up. The median CD4+ T-cell count among the patients was 80 cells per cubic millimeter. The most prevalent opportunistic infections were diseases related to human papillomavirus (in 29%), cryptococcosis (in 24%), molluscum contagiosum (in 9%), and nontuberculous mycobacterial diseases (in 5%). A reduced CD4 count (<100 cells per cubic millimeter), as compared with a CD4 count of 101 to 300 cells, was associated with a higher risk of opportunistic infection (odds ratio, 5.3; 95% confidence interval [CI], 2.8 to 10.7) and invasive cancer (odds ratio, 2.1; 95% CI, 1.1 to 4.3) and a lower risk of autoimmunity (odds ratio, 0.5; 95% CI, 0.2 to 0.9). The risk of death was similar to that in the age- and sex-adjusted general population, but the prevalence of cancer was higher. Among the study patients, ICL continued to be associated with increased susceptibility to viral, encapsulated fungal, and mycobacterial diseases, as well as with a reduced response to novel antigens and an increased risk of cancer. (Funded by the National Institute of Allergy and Infectious Diseases and the National Cancer Institute; ClinicalTrials.gov number, NCT00867269.)
Abstract After acute viral infection a small population of effector CD8 T cells upregulate CD127 expression and develop into long lived resting memory T cells. During chronic infections, such as HIV, there is an accumulation of CD8 T cells with effector/memory-like phenotype. These observations led to the hypothesis that there is a developmental impairment in the long lived resting memory T cells within that setting. The transcription factors RUNX3 and Eomesodermin (EOMES) are important in the development of long lived memory CD8 T cells. We studied the dynamics of CD127 expression, RUNX3 and EOMES in patients with HIV infection and different levels of viremia. Consistent with other reports, CD127 expression was decreased in the memory CD8 T cell subset. The CD8 memory CD127low T cells showed increased expression of RUNX3 and EOMES mRNA, as well as effector molecules perforin and granzyme B. In patients with suppressed viremia, we could identify two populations of CD8 T cells expressing EOMEShigh and EOMESint. The EOMESint cells showed a short-lived effector phenotype (perforin+, granzyme B+, CD127low) and the EOMEShigh cells showed a memory-like phenotype (perforin-, CD127high). These results suggest that in human CD8 T cells, EOMES is necessary for the maintenance of long lived memory CD8 T cells and its expression was influenced by HIV-RNA levels and the associated inflammatory environment (R=0.4, p=0.01). These findings provide new insights into the pathogenesis of HIV infection.
We examined the prevalence of Strongyloides stercoralis (Ss) infection in a cohort of AIDS patients from a US urban centre. We monitored our cohort for possible cases of dissemination or immune reconstitution inflammatory syndrome after antiretroviral therapy (ART) initiation.One hundred and three HIV-infected participants were prospectively sampled from a cohort observational study of ART-naive HIV-1-infected patients with CD4 ≤100 T cells/μl. Clinical symptoms, corticosteroid therapy, eosinophilia, CD4 count, and plasma HIV-RNA were reviewed. Sera were tested by an enzyme-linked immunosorbent assay (CrAg-ELISA) to crude Ss extract or to an Ss-specific recombinant protein (NIE) and by luciferase immunoprecipitation system assay (LIPS) for Ss-specific antibodies.Twenty-five per cent of study participants were Strongyloides seropositive by CrAg-ELISA and 62% had emigrated from Strongyloides-endemic areas. The remaining 38% of the seropositives were US born and tested negative by NIE and LIPS. CrAg-ELISA-positive participants had a median CD4 count of 22 T cells/μl and a median HIV-RNA of 4·87 log(10) copies/ml. They presented with diarrhea (27%), abdominal pain (23%), and skin manifestations (35%) that did not differ from seronegative patients. Peripheral blood eosinophilia was common among seropositive patients (prevalence of 62% compared to 29% in seronegatives, P = 0·004). Seropositive patients were treated with ivermectin. There were no cases of hyperinfection syndrome.Strongyloidiasis may be prevalent in AIDS patients in the USA who emigrated from Ss-endemic countries, but serology can be inconclusive, suggesting that empiric ivermectin therapy is a reasonable approach in AIDS patients originating from Strongyloides endemic areas.
Human immunodeficiency virus (HIV) disease leads to impaired B cell and antibody responses through mechanisms that remain poorly defined. A unique memory B cell subpopulation (CD20hi/CD27lo/CD21lo) in human tonsillar tissues was recently defined by the expression of the inhibitory receptor Fc-receptor-like-4 (FCRL4). In this study, we describe a similar B cell subpopulation in the blood of HIV-viremic individuals. FCRL4 expression was increased on B cells of HIV-viremic compared with HIV-aviremic and HIV-negative individuals. It was enriched on B cells with a tissuelike memory phenotype (CD20hi/CD27−/CD21lo) when compared with B cells with a classical memory (CD27+) or naive (CD27−/CD21hi) B cell phenotype. Tissuelike memory B cells expressed patterns of homing and inhibitory receptors similar to those described for antigen-specific T cell exhaustion. The tissuelike memory B cells proliferated poorly in response to B cell stimuli, which is consistent with high-level expression of multiple inhibitory receptors. Immunoglobulin diversities and replication histories were lower in tissuelike, compared with classical, memory B cells, which is consistent with premature exhaustion. Strikingly, HIV-specific responses were enriched in these exhausted tissuelike memory B cells, whereas total immunoglobulin and influenza-specific responses were enriched in classical memory B cells. These data suggest that HIV-associated premature exhaustion of B cells may contribute to poor antibody responses against HIV in infected individuals.
Immune reconstitution inflammatory syndrome (IRIS) is a common cause of morbidity among people with human immunodeficiency virus (PWH) who initiate antiretroviral therapy (ART) with severe lymphopenia. Easily accessible tools that reliably predict emergence and elucidate pathogenesis of IRIS are needed to facilitate improved clinical management.Plasma levels of biomarkers were measured before ART initiation in a large multinational cohort of ART-naive PWH with severe immunosuppression (CD4+ count <100 cells/mm3) in United States, Kenya, and Thailand. We performed a series of multiparametric analyses of inflammatory and clinical biomarkers and developed a composite score merging relevant biomarkers for use in a prediction model.We identified a distinct baseline inflammatory profile and changes in inflammatory networks among biomarkers in participants who subsequently developed mycobacterial or viral IRIS. We also developed a composite score incorporating biomarkers associated with IRIS (interleukin-6 [IL-6], IL-10, IL-27, sCD14, interferon-γ, tumor necrosis factor-α, hyaluronic acid, D-dimer, body mass index, and hemoglobin) that accurately predicted mycobacterial IRIS and death in this cohort.Systemic inflammatory profiles in PWH with severe immunosuppression are predictive of IRIS. Composite scores for the prediction of mycobacterial IRIS and death could be useful for risk stratification in PWH and lymphopenia initiating ART.NCT00286767.
