HIV-infected Lymphocytes Research Articles

Bystander Effects and Profibrotic Interactions in Hepatic Stellate Cells during HIV and HCV Coinfection.

This study aims to explore the influence of coinfection with HCV and HIV on hepatic fibrosis. A coculture system was set up to actively replicate both viruses, incorporating CD4 T lymphocytes (Jurkat), hepatic stellate cells (LX-2), and hepatocytes (Huh7.5). LX-2 cells' susceptibility to HIV infection was assessed through measurements of HIV receptor expression, exposure to cell-free virus, and cell-to-cell contact with HIV-infected Jurkat cells. The study evaluated profibrotic parameters, including programed cell death, ROS imbalance, cytokines (IL-6, TGF-β, and TNF-α), and extracellular matrix components (collagen, α-SMA, and MMP-9). The impact of HCV infection on LX-2/HIV-Jurkat was examined using soluble factors released from HCV-infected hepatocytes. Despite LX-2 cells being nonsusceptible to direct HIV infection, bystander effects were observed, leading to increased oxidative stress and dysregulated profibrotic cytokine release. Coculture with HIV-infected Jurkat cells intensified hepatic fibrosis, redox imbalance, expression of profibrotic cytokines, and extracellular matrix production. Conversely, HCV-infected Huh7.5 cells exhibited elevated profibrotic gene transcriptions but without measurable effects on the LX-2/HIV-Jurkat coculture. This study highlights how HIV-infected lymphocytes worsen hepatic fibrosis during HCV/HIV coinfection. They increase oxidative stress, profibrotic cytokine levels, and extracellular matrix production in hepatic stellate cells through direct contact and soluble factors. These insights offer valuable potential therapies for coinfected individuals.

The Synthetic Opioid Fentanyl Increases HIV Replication and Chemokine Co-Receptor Expression in Lymphocyte Cell Lines.

In the United States, the illicit use of synthetic opioids such as fentanyl has led to a serious public health crisis. Synthetic opioids are known to enhance viral replication and to suppress immunologic responses, but their effects on HIV pathogenesis remain unclear. Thus, we examined the impact of fentanyl on HIV-susceptible and HIV-infected cell types. TZM-bl and HIV-infected lymphocyte cells were incubated with fentanyl at varying concentrations. Expression levels of the CXCR4 and CCR5 chemokine receptors and HIV p24 antigen were quantified with ELISA. HIV proviral DNA was quantified using SYBR RT-PCR. Cell viability was detected with the MTT assay. RNAseq was performed to characterize cellular gene regulation in the presence of fentanyl. Fentanyl enhanced expression of both chemokine receptor levels in a dose-dependent manner in HIV-susceptible and infected cell lines. Similarly, fentanyl induced viral expression in HIV-exposed TZM-bl cells and in HIV-infected lymphocyte cell lines. Multiple genes associated with apoptosis, antiviral/interferon response, chemokine signaling, and NFκB signaling were differentially regulated. Synthetic opioid fentanyl impacts HIV replication and chemokine co-receptor expression. Increased virus levels suggest that opioid use may increase the likelihood of transmission and accelerate disease progression.

Neonatal immunization prevents the development of a chronic autoimmune response against CD4 caused by HIV-1 gp120 in rats.

The AIDS autoimmune hypothesis suggests that suppression of the autoimmunity against CD4 T lymphocytes should positively affect the course of HIV infection. The aim of this study was to determine whether neonatal immunization can be used to prevent induction of anti-CD4 autoimmune response triggered by HIV-1. The induction of anti-CD4 lymphocytes in HIV infection proceeds via their idiotypic interactions with anti-gp120 lymphocytes; therefore, the creation of tolerance to gp120 by means of neonatal immunization with gp120 may prevent subsequent induction of anti-CD4 lymphocytes. Neonatal immunization with CD4 may also be effective, since it can increase natural tolerance to CD4 and prevent its subsequent breakdown by gp120. Thus, anti-gp120 lymphocytes and anti-CD4 lymphocytes are potential neonatal stimulation targets. To determine which of these targets can be manipulated during the neonatal period, a computer model of the immune network was used. The computer model predictions were tested in a rat model of autoimmune CD4 T lymphocytopenia induced by gp120. The in silico studies predicted that stimulating a clone against an external antigen that is in idiotype-anti-idiotype interactions with an autoclone, when stimulation is performed during the time that the dynamic behavior type of the immune network is being established, changes the autoimmune response from self-perpetuating to transient. Experimental studies confirmed the predictions of the computer model and showed that neonatal immunization with gp120 suppresses anti-CD4 autoantibody production and prevents the development of autoimmune CD4 T lymphocytopenia triggered in adult rats by gp120. Neonatal HIV-1 gp120 immunization enhances natural tolerance to CD4.

CHARACTERISTICS AND IMPACT OF OPPORTUNITY INFECTIONS ON GASTROINTESTINAL TRACT IN HIV-INFECTED PEOPLE

A decrease in the number of CD4 + lymphocytes in HIV infection is known to increase the risk of opportunistic infections, malignancies and other diseases classified as diagnostic criteria for AIDS. The purpose of this work is to analyze the main groups of opportunistic infections and infectious lesions commonly affecting the gastrointestinal tract in HIV-positive patients. Up to 90% of deaths from HIV infection are directly or indirectly caused by opportunistic infections that emphasize the importance of further research aimed at their prevention and management. A progressive decline in the number of CD4 + lymphocytes due to their non-stop destruction and insufficient replenishment from progenitor cells underlies the development of immunodeficiency in HIV infection. Pathological changes in the gastric mucosa may be associated with Mycobacterium avium complex. Cryptosporidosis is an opportunistic infection reported as common among immuno-suppressed patients. It occurs as a long-term, mild infection without severe clinical symptoms. In recent decades, opportunistic infections have become a medical and social challenge due to their spread and significant impact on the quality of life of HIV-positive people. It should be also noted that the presence of opportunistic infection has little effect on the characteristics of the microbial picture in the intestine. But, at the same time, it can deteriorate metabolic processes in the intestinal epithelium, proliferation and maintenance of its resistance to aggressive factors. Therefore, the issue of detection and timely treatment of opportunistic infections is of a great medical and social importance. Conclusions: Early diagnosis, prevention and management of opportunistic infections play an essential role in increasing the life expectancy of HIV-positive people and improving the course of the disease.

Productive HIV infection in astrocytes can be established via a nonclassical mechanism.

Astrocytes are proposed to be a critical reservoir of HIV in the brain. However, HIV infection of astrocytes is inefficient in vitro except for cell-to-cell transmission from HIV-infected cells. Here, we explore mechanisms by which cell-free HIV bypasses entry and postentry barriers leading to a productive infection. HIV infection of astrocytes was investigated by a variety of techniques including transfection of CD4-expressing plasmid, treatment with lysosomotropic agents or using a transwell culture system loaded with HIV-infected lymphocytes. Infection was monitored by HIV-1 p24 in culture supernatants and integrated proviral DNA was quantified by Alu-PCR. Persistent HIV infection could be established in astrocytes by transfection of proviral DNA, transduction with VSV-G-pseudotyped viruses, transient expression of CD4 followed by HIV infection, or simultaneous treatment with lysosomotropic chloroquine or Tat-HA2 peptide with HIV infection. In absence of these treatments, HIV entered via endocytosis as seen by electronmicroscopy and underwent lysosomal degradation without proviral integration, indicating endocytosis is a dead end for HIV in astrocytes. Nevertheless, productive infection was observed when astrocytes were in close proximity but physically separated from HIV-infected lymphocytes in the transwell cultures. This occurred with X4 or dual tropic R5X4 viruses and was blocked by an antibody or antagonist to CXCR4. A CD4-independent, CXCR4-dependent mechanism of viral entry is proposed, by which immature HIV particles from infected lymphocytes might directly bind to CXCR4 on astrocytes and trigger virus--cell fusion during or after the process of viral maturation. This mechanism may contribute to the formation of brain HIV reservoirs.

High frequencies of PMN-MDSCs are associated with low suppressive capacity in advanced stages of HIV-1 infection

BackgroundPolymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) are an immature cell type that inhibits the effector functions of T lymphocytes in chronic HIV infection. A well-known immunological feature of the disease course is the development of immune exhaustion, which is correlated with excessive immune activation in late-stage disease. Here, we hypothesized that immune exhaustion would also affect PMN-MDSCs in late-stage HIV-1 infection.MethodsWe evaluated untreated chronically HIV-infected patients (progressors, n = 10) and control groups (controllers, patients with non-small cell lung carcinoma and healthy controls, n = 16) with regard to levels of PMN-MDSCs and their inhibitory potential. Additionally, we studied CD8 T cell effector functions (interferon-gamma, TNF alpha, IL-2 and CD107) and parameters of CD8 T cell activation (CD38 and HLA-DR) and exhaustion (PD-1 and LAG-3) by flow cytometry. Plasma inflammation markers analyzed here were IL-6, IL-8, soluble CD14, highly sensitive CRP, and cystatin C.ResultsCoincubation experiments with isolated PMN-MDSCs led to a significant inhibition of CD8 T cell proliferation (p < 0.0001), with a significant correlation between PMN-MDSC frequency and suppressive capacity: the higher the frequency of PMN-MDSCs was, the lower the suppressive capacity (rho = 0.51, p = 0.0082). Stratifying all study subjects into subgroups with PMN-MDSC frequencies above or below 2.5% resulted in a significantly increased suppressive capacity in patients with frequencies below 2.5% (p = 0.021). While there was no correlation with the cellular activation markers CD38 and HLA-DR, high IL-8 levels were significantly associated with high PMN-MDSC frequencies (rho = 0.52, p = 0.0074) and low suppressive capacity (rho = 0.47, p = 0.019).ConclusionsIn this study, we demonstrate for the first time that PMN-MDSCs show limited effector functions in advanced disease stages of HIV infection. The hyperactive immune state is associated with this loss of function. However, we show an association with the proinflammatory cytokine IL-8, which is an important factor for the migration and adhesion of polymorphonuclear cells.

HIV infection induces CD44+PD-L1+ tumor initiating cells in AIDS associated non-AIDS defining cancers

Abstract The antiretroviral therapy (ART) significantly increased the number of aging HIV patients and the non-AIDS defining cancers (NADC) have become the most frequent co-morbidity and causes of death among HIV patients. The role of HIV infection in cancer initiation and progression is unclear. Tumor initiating cells (TIC) are responsible for chemo-resistance, metastasis and mortality. Our previous work demonstrated that tumor-intrinsic PD-L1 correlate with proportion (%) of TIC and virulence. Supernatants from HIV infected peripheral blood lymphocyte (PBMC) cultures (HIV-sup) significantly increased % TIC (CD44+PD-L1+) in two human tumor cell lines-SCC4 (squamous carcinoma) and HeLa (cervical cancer). HIV single stranded RNA (ssRNA) binds TLR7/8, and leads to immune activation and inflammation. The Cancer Genome Atlas database analyses showed that squamous cancer and cervical adenocarcinoma patients with TLR7/8 amplification had significantly poor overall survival. TLR7 agonist R848 led to significant increase in % TIC, whereas treatment of the cancer cells with HIV-sup in presence of TLR7/8 inhibitor ODN2088 reversed this effect. Similarly, pharmacological inhibition (by ACHP) of TLR7/8 mediated NFkB signaling pathway decreased TIC % two-fold, confirming HIV mediated TLR7/8 signaling has pro-TIC effects. High levels of inflammatory cytokine IFNα correlates with HIV load and persistent infection. Treatment with IFNα led to a significant increase in TIC whereas blocking IFNα-induced JAK signaling by ruxolitinib, in presence of HIV-sup reduced TIC significantly. Thus, our novel data gives insight into HIV induced host-pathogen interactions that lead to TIC prevalence.

25 Estimating the contribution of proliferation to HIV-infected lymphocyte persistence

25 Estimating the contribution of proliferation to HIV-infected lymphocyte persistence

ILC You Later: Early and Irreparable Loss of Innate Lymphocytes in HIV Infection

Loss of IL-17-producing cells in the gut during HIV infection is linked to GI barrier damage. Kløverpris etal. (2016) find that circulating ILCs are lost early and irreversibly during HIV infection. Early ART administration protects against the ILC loss, and this might be clinically beneficial to HIV-infected individuals.

The DC-SIGN-CD56 interaction inhibits the anti-dendritic cell cytotoxicity of CD56 expressing cells.

BackgroundThis study aimed to clarify interactions of the pattern-recognition receptor DC-SIGN with cells from the HIV-infected peripheral blood lymphocyte cultures.MethodsCells from control and HIV-infected peripheral blood lymphocyte cultures were tested for the surface expression of DC-SIGN ligands. The DC-SIGN ligand expressing cells were analyzed for the role of DC-SIGN-ligand interaction in their functionality.ResultsIn the vast majority of experiments HIV-infected lymphocytes did not express detectable DC-SIGN ligands on their cell surfaces. In contrast, non-infected cells, carrying NK-specific marker CD56, expressed cell surface DC-SIGN ligands. The weakly polysialylated CD56 was identified as a novel DC-SIGN ligand. The treatment of DC-SIGN expressing dendritic cells with anti-DC-SIGN antibodies increased the anti-dendritic cell cytotoxicity of CD56pos cells. The treatment of CD56pos cells with a peptide, blocking the weakly polysialylated CD56-specifc trans-homophilic interactions, inhibited their anti-dendritic cells cytotoxicity.ConclusionsThe interaction between DC-SIGN and CD56 inhibits homotypic intercellular interactions of CD56pos cells and protects DC-SIGN expressing dendritic cells against CD56pos cell-mediated cytotoxicity. This finding can have an impact on the development of approaches to HIV infection and cancer therapy as well as in transplantation medicine.

FAS −670 A/G polymorphism may be associated with the depletion of CD4+ T lymphocytes in HIV-1 infection

In this study, the polymorphisms in the FAS and FASL genes was investigated in a sample of 198 HIV-1-seropositive individuals and 191 seronegative controls to evaluate a possible association between polymorphisms and the infection. The identification of the A and G alleles of the FAS −670 polymorphism was accomplished through polymerase chain reaction assays followed by digestion with the restriction enzyme MvaI. The identification of the A and G alleles of the FAS −124 polymorphism and the T and delT alleles of the FAS −169 polymorphism were performed using the amplification-created restriction site method followed by restriction fragment length polymorphism reactions. The comparative analysis of allelic and genotypic frequencies between the groups did not reveal any significant differences. However, the quantitative analysis of CD4+ T lymphocytes suggests that the G allele of the FAS −670 A/G polymorphism can be a protective factor against the depletion of these cells in the course of an HIV-1 infection. Polymorphisms in the FAS and FASL genes were not associated with the number of CD8+ T lymphocytes or the plasma viral load. Our findings suggest that the FAS −670 polymorphism may be associated with apoptosis of CD4+ T lymphocytes after infection by HIV-1.

Cell-to-cell contact facilitates HIV transmission from lymphocytes to astrocytes via CXCR4.

HIV reservoir in the brain represents a major barrier for curing HIV infection. As the most abundant, long-lived cell type, astrocytes play a critical role in maintaining the reservoir; however, the mechanism of infection remains unknown. Here, we determine how viral transmission occurs from HIV-infected lymphocytes to astrocytes by cell-to-cell contact. Human astrocytes were exposed to HIV-infected lymphocytes and monitored by live-imaging, confocal microscopy, transmission and three-dimensional electron microscopy. A panel of receptor antagonists was used to determine the mechanism of viral entry. We found that cell-to-cell contact resulted in efficient transmission of X4 or X4R5-using viruses from T lymphocytes to astrocytes. In co-cultures of astrocytes with HIV-infected lymphocytes, the interaction occurred through a dynamic process of attachment and detachment of the two cell types. Infected lymphocytes invaginated into astrocytes or the contacts occurred via filopodial extensions from either cell type, leading to the formation of virological synapses. In the synapses, budding of immature or incomplete HIV particles from lymphocytes occurred directly onto the membranes of astrocytes. This cell-to-cell transmission could be almost completely blocked by anti-CXCR4 antibody and its antagonist, but only partially inhibited by anti-CD4, ICAM1 antibodies. Cell-to-cell transmission was mediated by a unique mechanism by which immature viral particles initiated a fusion process in a CXCR4-dependent, CD4-independent manner. These observations have important implications for developing approaches to prevent formation of HIV reservoirs in the brain.

HIV cell-to-cell spread and innate immune responses

Our research is aimed at understanding the interplay between viruses and the immune system. HIV cell-tocell transmission is a major mechanism of viral spread. We are studying how antiviral molecules, such as broadly neutralizing antibodies and restriction factors, known to inhibit infection with cell-free virions, interfere with HIV-1 cell-to-cell transmission. Moreover, we previously showed that HIV-1 infected lymphocytes are more potent inducers of type-l IFN than free virions. There are target cell-type differences in the recognition of infected lymphocytes. In primary pDCs and pDC-like cells, recognition occurs in large part through TLR7. In myeloid DCs, and other cells that lack TLR7, recognition is independent of TLR7, and occurs in a large part through a cytoplasmic pathway that we are currently analyzing. Finally, we are examining how HIV-2 spreads from cell-to-cell and triggers type-l IFN in various primary cell types. Characterization of the mechanisms of innate recognition of HIV-infected cells allows a better understanding of the pathogenic and exacerbated immunologic events associated with HIV infection.

Novel ‘Si[sbnd]C’ carbosilane dendrimers as carriers for anti-HIV nucleic acids: Studies on complexation and interaction with blood cells

Treatment of HIV infection by gene therapy is a promising tool for combating AIDS. One of the primary limitations of gene therapy is the effective delivery of nucleic acids to the target cells. Dendrimers are nanoparticles that are increasingly being used as nucleic acid vehicles. We have synthesized “SiC” amino-terminated carbosilane dendrimers [GnO3(NMe3)m]m+ functionalized with quaternary ammonium (NMe3+) terminal groups via hydrosilylation of allyl dimethylamine with the corresponding GnO3(SiH)m dendrimers and further addition of MeI. These dendrimers are soluble in water. Initially, complexation between these “SiC” dendrimers and anti-HIV nucleic acids (oligodeoxynucleotides ANTITAR and GEM91, siRNA siP24) was studied and molar ratios for complete complexation were determined. Then the charge and size of the dendriplexes (complexes of “SiC” dendrimers with nucleic acids) were analyzed and it was found that they possessed charges of +5 to +40mV and sizes of 60–600nm (zeta-size) or 50–100nm (atomic force microscopy) suitable for cell transfection. Stability studies showed that the dendriplexes were stable over time and were resistant to degradation by serum albumin. The effects of dendrimers and their dendriplexes on erythrocytes (isolated and in whole blood) revealed that the dendriplexes were significantly less cytotoxic than the pure dendrimers. The effects of dendrimers and their dendriplexes on peripheral blood mononuclear cells (the main target of HIV) were analyzed and it was found that the dendriplexes were 10 times less cytotoxic than the pure dendrimers. Finally, transfection experiments revealed that “SiC”-carbosilane dendrimers had a restricted ability to deliver long-chain double-stranded nucleic acids. The results indicate that these cationic carbosilane dendrimers are good candidates for delivering short-chain siRNA and oligodeoxynucleotide to HIV-infected peripheral blood mononuclear cells or lymphocytes.

Tubular cell HIV-entry through apoptosed CD4 T cells: A novel pathway

We hypothesized that HIV-1 may enter tubular cells by phagocytosis of apoptotic fragments of HIV-1-infected T cells infiltrating tubular interstitium. The study was designed to evaluate the interaction of programmed death-1 (PD-1) receptors on CD4 T cells and programmed death ligand-1 (PD-L1) on tubular cells (HK2 and HRPTEC, primary tubular cells). Co-cultivation of HIV-1 infected lymphocytes (HIV-LY) with HK2s/HRPTECs resulted in T cell apoptosis, uptake of the apoptosed HIV-LY by HK2s/HRPTECs, tubular cell activation and HIV expression. Cytochalasin-B inhibited tubular cell HIV-LY uptake and anti-PD-L1 antibody inhibited HIV-LY apoptosis and tubular cell HIV-LY uptake, activation and HIV expression. These observations do indicate induction of apoptosis of T cells due to interaction of PD-1 and PD-L1 upon co-cultivation and subsequent phygocytosis of HIV-laden apoptotic bodies by tubular cells and thus the transfer of HIV-1 into tubular cells. These findings identify a novel pathway that facilitates HIV-1 entry into tubular cell.

Short Communication: Adhesion Pathways Utilized by HIV-Infected Lymphocytes

We recently reported a novel adhesion pathway in lymphocytes that is mediated by cyclin-dependent kinase (Cdk) 4 activity and mediates lymphocyte interactions with endothelial matrix. We now demonstrate that HIV-infected lymphocytes also use Cdk4 to mediate spontaneous adhesion to fibronectin and endothelial matrix. We further demonstrate that HIV-infected lymphocytes require Rap-1 activity for phorbol-stimulated adhesion. Understanding adhesion pathways used by HIV-infected lymphocytes may lead to interventions to regulate aberrant adhesion and migration.

Novel insights into innate sensing of HIV-infected cells

Our research is aimed at understanding the interplay between viruses and the immune system. We are analyzing how HIV infection triggers production of type-l interferon (IFN) and other cytokines in various cell types. Cell-free HIV-1 virions are considered to be poor stimulators of IFN production. We examined how HIV-infected cells are recognized by plasmacytoid dendritic cells (pDCs), by monocyte-derived DCs (MDDCs), and by other cells. We show that infected lymphocytes are more potent inducers of IFN than virions. There are target cell-type differences in the recognition of infected lymphocytes. In primary pDCs and pDC-like cells, recognition occurs in large part through TLR7, as demonstrated by the use of inhibitors and by TLR7 silencing. Donor cells expressing replication-defective viruses, carrying mutated reverse transcriptase, integrase or nucleocapsid proteins induced IFN production by target cells as potently as wild-type virus. In contrast, Env-deleted or fusion defective HIV-1 mutants were less efficient, suggesting that in addition to TLR7, cytoplasmic cellular sensors may also mediate viral sensing. Furthermore, in a model of TLR7-negative cells, we demonstrate that the IRF3 pathway, through a process requiring access of incoming viral material to the cytoplasm, allows sensing of HIV-infected lymphocytes. We are also currently analyzing the role of SAMHD1, a recently identified anti-HIV restriction factor, in the activation of MDDCs by HIV. Altogether, our results indicate that detection of HIV-infected lymphocytes occurs at different levels, through both endosomal and cytoplasmic pathways. Characterization of the mechanisms of innate recognition of HIV-infected cells allows a better understanding of the pathogenic and exacerbated immunologic events associated with HIV infection.

A Common Path to Innate Immunity to HIV-1 Induced by Toll-Like Receptor Ligands in Primary Human Macrophages

Toll-like receptors (TLR) represent the best characterized receptor family transducing innate immune responses, the first line of defense against microbial invaders. This study was designed to investigate whether responses through TLR inhibit HIV-1 replication in its primary target cells. Primary human macrophages and lymphocytes from several different donors and HIV-1 infection in tissue culture were used exclusively in this work. We report that ligands of three different TLR: LPS, R848, and double stranded RNA, induce a common antiviral response in macrophages as assayed by measurement of HIV-1 p24 protein, gag DNA, and entry into cells. HIV-1 infection is arrested after efficient entry but prior to reverse transcription. TLR-ligand activated cells secrete antiviral factors that induce a similar restriction. HIV-1 infection of lymphocytes is not affected by exposure to TLR ligands or to antiviral factors secreted by activated macrophages. TBK1, but neither NF-κB nor JAK-STAT activity, is required in macrophages to mount this antiviral response; the combination of p38 MAPK and JNK are partially required for induction of antiviral activity. Based on transcriptional induction and inhibition, the TLR-linked antiviral activity is different from APOBEC3 A or G, interferon-β, NAMPT, or p21Cip1. The cell-type specificity, site of action, and requirement for signaling intermediates suggest that the TLR-linked antiviral activity is novel.

Innate Sensing of HIV-Infected Cells

Cell-free HIV-1 virions are poor stimulators of type I interferon (IFN) production. We examined here how HIV-infected cells are recognized by plasmacytoid dendritic cells (pDCs) and by other cells. We show that infected lymphocytes are more potent inducers of IFN than virions. There are target cell-type differences in the recognition of infected lymphocytes. In primary pDCs and pDC-like cells, recognition occurs in large part through TLR7, as demonstrated by the use of inhibitors and by TLR7 silencing. Donor cells expressing replication-defective viruses, carrying mutated reverse transcriptase, integrase or nucleocapsid proteins induced IFN production by target cells as potently as wild-type virus. In contrast, Env-deleted or fusion defective HIV-1 mutants were less efficient, suggesting that in addition to TLR7, cytoplasmic cellular sensors may also mediate sensing of infected cells. Furthermore, in a model of TLR7-negative cells, we demonstrate that the IRF3 pathway, through a process requiring access of incoming viral material to the cytoplasm, allows sensing of HIV-infected lymphocytes. Therefore, detection of HIV-infected lymphocytes occurs through both endosomal and cytoplasmic pathways. Characterization of the mechanisms of innate recognition of HIV-infected cells allows a better understanding of the pathogenic and exacerbated immunologic events associated with HIV infection.

Early Interferon-γ Production in Human Lymphocyte Subsets in Response to Nontyphoidal Salmonella Demonstrates Inherent Capacity in Innate Cells

BackgroundNontyphoidal Salmonellae frequently cause life-threatening bacteremia in sub-Saharan Africa. Young children and HIV-infected adults are particularly susceptible. High case-fatality rates and increasing antibiotic resistance require new approaches to the management of this disease. Impaired cellular immunity caused by defects in the T helper 1 pathway lead to intracellular disease with Salmonella that can be countered by IFNγ administration. This report identifies the lymphocyte subsets that produce IFNγ early in Salmonella infection.MethodologyIntracellular cytokine staining was used to identify IFNγ production in blood lymphocyte subsets of ten healthy adults with antibodies to Salmonella (as evidence of immunity to Salmonella), in response to stimulation with live and heat-killed preparations of the D23580 invasive African isolate of Salmonella Typhimurium. The absolute number of IFNγ-producing cells in innate, innate-like and adaptive lymphocyte subpopulations was determined.Principal FindingsEarly IFNγ production was found in the innate/innate-like lymphocyte subsets: γδ-T cells, NK cells and NK-like T cells. Significantly higher percentages of such cells produced IFNγ compared to adaptive αβ-T cells (Student's t test, P<0.001 and ≤0.02 for each innate subset compared, respectively, with CD4+- and CD8+-T cells). The absolute numbers of IFNγ-producing cells showed similar differences. The proportion of IFNγ-producing γδ-T cells, but not other lymphocytes, was significantly higher when stimulated with live compared with heat-killed bacteria (P<0.0001).Conclusion/SignificanceOur findings indicate an inherent capacity of innate/innate-like lymphocyte subsets to produce IFNγ early in the response to Salmonella infection. This may serve to control intracellular infection and reduce the threat of extracellular spread of disease with bacteremia which becomes life-threatening in the absence of protective antibody. These innate cells may also help mitigate against the effect on IFNγ production of depletion of Salmonella-specific CD4+-T lymphocytes in HIV infection.