Gamma Interferon Regulates Contraction of the Influenza Virus-Specific CD8 T Cell Response and Limits the Size of the Memory Population

The factors that regulate the contraction of the CD8 T cell response and the magnitude of the memory cell population against localized mucosal infections such as influenza are important for generation of efficient vaccines but are currently undefined. In this study, we used a mouse model of influenza to demonstrate that the absence of gamma interferon (IFN-γ) or IFN-γ receptor 1 (IFN-γR1) leads to aberrant contraction of antigen-specific CD8 T cell responses. The increased accumulation of the effector CD8 T cell population was independent of viral load. Reduced contraction was associated with an increased fraction of CD8 T cells expressing the interleukin-7 receptor (IL-7R) at the peak of the response, resulting in enhanced numbers of memory/memory precursor cells in IFN-γ^−/− and IFN-γR^−/− compared to wild-type (WT) mice. Blockade of IL-7 within the lungs of IFN-γ^−/− mice restored the contraction of influenza virus-specific CD8 T cells, indicating that IL-7R is important for survival and is not simply a consequence of the lack of IFN-γ signaling. Finally, enhanced CD8 T cell recall responses and accelerated viral clearance were observed in the IFN-γ^−/− and IFN-γR^−/− mice after rechallenge with a heterologous strain of influenza virus, confirming that higher frequencies of memory precursors are formed in the absence of IFN-γ signaling. In summary, we have identified IFN-γ as an important regulator of localized viral immunity that promotes the contraction of antigen-specific CD8 T cells and inhibits memory precursor formation, thereby limiting the size of the memory cell population after an influenza virus infection.     

Reovirus Induction of and Sensitivity to Beta Interferon in Cardiac Myocyte Cultures Correlate with Induction of Myocarditis and Are Determined by Viral Core Proteins

Reovirus-induced acute myocarditis in mice serves as a model to investigate non-immune-mediated mechanisms of viral myocarditis. We have used primary cardiac myocyte cultures infected with a large panel of myocarditic and nonmyocarditic reassortant reoviruses to identify determinants of viral myocarditic potential. Here, we report that while both myocarditic and nonmyocarditic reoviruses kill cardiac myocytes, viral myocarditic potential correlates with viral spread through cardiac myocyte cultures and with cumulative cell death. To address the role of secreted interferon (IFN), we added anti-IFN-α/β antibody to infected cardiac myocyte cultures. Antibody benefited nonmyocarditic more than myocarditic virus spread (P < 0.001), and this benefit was associated with the reovirus M1 and L2 genes. There was no benefit for a differentiated skeletal muscle cell line culture (C2C12 cells), suggesting cell type specificity. IFN-β induction in reovirus-infected cardiac myocyte cultures correlated with viral myocarditic potential (P = 0.006) and was associated with the reovirus M1, S2, and L2 genes. Sensitivity to the antiviral effects of IFN-α/β added to cardiac myocyte cultures also correlated with viral myocarditic potential (P = 0.004) and was associated with the same reovirus genes. Several reoviruses induced IFN-β levels discordant with their myocarditic phenotypes, and for those tested, sensitivity to IFN-α/β compensated for the anomalous induction levels. Thus, the combination of induction of and sensitivity to IFN-α/β is a determinant of reovirus myocarditic potential. Finally, a nonmyocarditic reovirus induced cardiac lesions in mice depleted of IFN-α/β, demonstrating that IFN-α/β is a determinant of reovirus-induced myocarditis. This provides the first identification of reovirus genes associated with IFN induction and sensitivity and provides the first evidence that IFN-β can be a determinant of viral myocarditis and reovirus disease.     

The Immunodominance Change and Protection of CD4+ T-Cell Responses Elicited by an Envelope Protein Domain III-Based Tetravalent Dengue Vaccine in Mice

Dengue is the leading cause of mosquito-borne viral infections and no vaccine is available now. Envelope protein domain III (ED3) is the major target for the binding of dengue virus neutralizing antibodies; however, the ED3-specifc T-cell response is less well understood. To investigate the T-cell responses to four serotypes of dengue virus (DENV-1 to 4), we immunized mice using either a tetravalent ED3-based DNA or protein vaccine, or combined both as a DNA prime-protein boost strategy (prime-boost). A significant serotype-dependent IFN-γ or IL-4 response was observed in mice immunized with either the DNA or protein vaccine. The IFN-γ response was dominant to DENV-1 to 3, whereas the IL-4 response was dominant to DENV-4. Although the similar IgG titers for the four serotypes were observed in mice immunized with the tetravalent vaccines, the neutralizing antibody titers varied and followed the order of 2 = 3>1>4. Interestingly, the lower IFN-γ response to DENV-4 is attributable to the immunodominance change between two CD4⁺ T-cell epitopes; one T-cell epitope located at E_349-363 of DENV-1 to 3 was more immunogenic than the DENV-4 epitope E_313-327. Despite DENV-4 specific IFN-γ responses were suppressed by immunodominance change, either DENV-4-specific IFN-γ or neutralizing antibody responses were still recalled after DENV-4 challenge and contributed to virus clearance. Immunization with the prime-boost elicited both IFN-γ and neutralizing antibody responses and provided better protection than either DNA or protein immunization. Our findings shed light on how ED3-based tetravalent dengue vaccines sharpen host CD4 T-cell responses and contribute to protection against dengue virus.     

Measurement of CD8+ and CD4+ T Cell Frequencies Specific for EBV LMP1 and LMP2a Using mRNA-Transfected DCs

An EBV-specific cellular immune response is associated with the control of EBV-associated malignancies and lymphoproliferative diseases, some of which have been successfully treated by adoptive T cell therapy. Therefore, many methods have been used to measure EBV-specific cellular immune responses. Previous studies have mainly used autologous EBV-transformed B-lymphoblastoid cell lines (B-LCLs), recombinant viral vectors transfected or peptide pulsed dendritic cells (DCs) as stimulators of CD8⁺ and CD4⁺ T lymphocytes. In the present study, we used an interferon-γ (IFN-γ) enzyme-linked immunospot (ELISPOT) assay by using isolated CD8⁺ and CD4⁺ T cells stimulated with mRNA-transfected DCs. The frequency of latent membrane protein 1 (LMP1)-specific IFN-γ producing CD4⁺ T cells was significantly higher than that of LMP2a. The frequency of IFN-γ producing CD4⁺ T cells was significantly correlated with that of CD8⁺ T cells in LMP1-specific immune responses (r = 0.7187, Pc < 0.0001). To determine whether there were changes in LMP1- or LMP2a-specific immune responses, subsequent peripheral blood mononuclear cells (PBMCs) samples were analyzed. Significant changes were observed in 5 of the 10 donors examined, and CD4⁺ T cell responses showed more significant changes than CD8⁺ T cell responses. CD8⁺ and CD4⁺ T cells from EBV-seropositive donors secreted only the Th1 cytokines IFN-γ, TNF-α, and IL-2, while Th2 (IL-4) and Th17 (IL-17a) cytokines were not detected. CD4⁺ T cells secreted significantly higher cytokine levels than did CD8⁺ T cells. Analysis of EBV-specific T cell responses using autologous DCs transfected with mRNA might provide a comprehensive tool for monitoring EBV infection and new insights into the pathogenesis of EBV-associated diseases.     

TcVac3 Induced Control of Trypanosoma cruzi Infection and Chronic Myocarditis in Mice

We characterized the immune responses elicited by a DNA-prime/MVA-boost vaccine (TcVac3) constituted of antigenic candidates (TcG2 and TcG4), shown to be recognized by B and T cell responses in Trypanosoma cruzi (Tc) infected multiple hosts. C57BL/6 mice immunized with TcVac3 elicited a strong antigen-specific, high-avidity, trypanolytic antibody response (IgG2b>IgG1); and a robust antigen- and Tc-specific CD8⁺T cell response with type-1 cytokine (IFN-γ⁺TNF-α>IL-4⁺IL-10) and cytolytic effector (CD8⁺CD107a⁺IFN-γ⁺Perforin⁺) phenotype. The vaccine-induced effector T cells significantly expanded upon challenge infection and provided >92% control of T. cruzi. Co-delivery of IL-12 and GMCSF cytokine adjuvants didn’t enhance the TcVac3-induced resistance to T. cruzi. In chronic phase, vaccinated/infected mice exhibited a significant decline (up to 70%) in IFN-γ⁺CD8⁺T cells, a predominance of immunoregulatory IL-10⁺/CD4⁺T and IL10⁺/CD8⁺T cells, and presented undetectable tissue parasitism, inflammatory infiltrate, and fibrosis in vaccinated/infected mice. In comparison, control mice responded to challenge infection by a low antibody response, mixed cytokine profile, and consistent activation of pro-inflammatory CD8⁺T cells associated with parasite persistence and pathologic damage in the heart. We conclude that TcVac3 elicited type-1 effector T cell immunity that effectively controlled T. cruzi infection, and subsequently, predominance of anti-inflammatory responses prevented chronic inflammation and myocarditis in chagasic mice.     

TGF-β and IL-10 Production by HIV-Specific CD8+ T Cells Is Regulated by CTLA-4 Signaling on CD4+ T Cells

Immune dysregulation in HIV-1 infection is associated with increased expression of inhibitory molecules such as CTLA-4, TGF-β, and IL-10. In this study we examined one potential mechanism for regulating TGF-β and IL-10 expression by HIV-specific suppressor CD8+ T cells. No overlap between TGF-β, IL-10, and IFN-γ cytokine production by HIV-specific CD8+ T cells was observed. TGF-β positive and IL-10 positive cells were FOXP3 negative, CD25 negative, and displayed a heterogeneous surface expression of CD127. TGF-β and IL-10 positive CD8+ T cells did not express CTLA-4. Nevertheless, CTLA-4 blockade resulted in a significant decrease in HIV-specific TGF-β positive and IL-10 positive CD8+ T cell responses, and a concomitant increase in HIV-specific IFN-γ positive CD8+ T cell responses. Depletion of CD4+ T cells abrogated the impact of CTLA-4 on HIV-specific TGF-β positive and IL-10 positive CD8+ T cells. Our study suggests that CTLA-4 Signaling on CD4+ T cells regulates the inhibitory functions of the HIV-specific suppressor CD8+ T cells.     

Th1 and Th17 Responses to Helicobacter pylori in Bangladeshi Infants,Children and Adults

Both Th1 and Th17 cells are important components of the immune response to Helicobacter pylori (Hp) in adults, but less is known about T cell responses to Hp during early childhood, when the infection is often acquired. We investigated Th1 and Th17 type responses to Hp in adults, children and infants in Bangladesh, where Hp is highly endemic. IL-17 and IFN-γ mRNA levels in gastric biopsies from Hp-infected Bangladeshi adults were analyzed and compared to levels in infected and uninfected Swedish controls. Since biopsies could not be collected from infants and children, cytokine responses in Bangladeshi infants (6–12 months), children (3–5 years) and adults (>19 years) were instead compared by stimulating peripheral blood mononuclear cells (PBMCs) with a Hp membrane preparation (MP) and analyzing culture supernatants by ELISA and cytometric bead array. We found significantly higher expression of IL-17 and IFN-γ mRNA in gastric mucosa of Hp-infected Bangladeshi and Swedish adults compared to uninfected Swedish controls. PBMCs from all age groups produced IL-17 and IFN-γ after MP stimulation, but little Th2 cytokines. IL-17 and IFN-γ were primarily produced by CD4⁺ T cells, since CD4⁺ T cell depleted PBMCs produced reduced amounts of these cytokines. Infant cells produced significantly more IL-17, but similar levels of IFN-γ, compared to adult cells after MP stimulation. In contrast, polyclonal stimulation induced lower levels IL-17 and IFN-γ in infant compared to adult PBMCs and CD4⁺ T cells. The strong IL-17 production in infants after MP stimulation was paralleled by significantly higher production of the IL-17 promoting cytokine IL-1β from infant compared to adult PBMCs and monocytes. In conclusion, these results show that T cells can produce high levels of IL-17 and IFN-γ in response to Hp from an early age and indicate a potential role for IL-1β in promoting Th17 responses to Hp during infancy.     

Characterization of Anamnestic T-cell Responses Induced by Conventional Vaccines against Contagious Bovine Pleuropneumonia

A better understanding of how T1 vaccination confers immunity would facilitate the rational design of improved vaccines against contagious bovine pleuropneumonia (CBPP). We show here that mycoplasmas-induced recall proliferation and IFN-γ responses are detected in cattle that received multiple shots of T1 vaccines. These anamnestic responses were under the strict control of CD4⁺ T lymphocytes. Moreover, CD62L expression indicated that both CD4⁺ effector memory (Tem) and central memory (Tcm) T lymphocytes are elicited in these animals. Comparative analysis with data from cattle that completely recovered from CBPP infection revealed similar anamnestic T-cell responses albeit at a lower magnitude for T1-vaccinated animals, particularly in the Tcm compartment. In conclusion, we discuss how our current understanding of T-cell responses will contribute to ongoing efforts for the improvement of future CBPP vaccines.     

Mitochondrial reactive oxygen is critical for IL-12/IL-18-induced IFN-γ production by CD4+ T cells and is regulated by Fas/FasL signaling

Mitochondrial activation and the production of mitochondrial reactive oxygen species (mROS) are crucial for CD4⁺ T cell responses and have a role in naïve cell signaling after TCR activation. However, little is known about mROS role in TCR-independent signaling and in recall responses. Here, we found that mROS are required for IL-12 plus IL-18-driven production of IFN-γ, an essential cytokine for inflammatory and autoimmune disease development. Compared to TCR stimulation, which induced similar levels of mROS in naïve and memory-like cells, IL-12/IL-18 showed faster and augmented mROS production in memory-like cells. mROS inhibition significantly downregulated IFN-γ and CD44 expression, suggesting a direct mROS effect on memory-like T cell function. The mechanism that promotes IFN-γ production after IL-12/IL-18 challenge depended on the effect of mROS on optimal activation of downstream signaling pathways, leading to STAT4 and NF-κB activation. To relate our findings to IFN-γ-driven lupus-like disease, we used Fas-deficient memory-like CD4⁺ T cells from lpr mice. Importantly, we found significantly increased IFN-γ and mROS production in lpr compared with parental cells. Treatment of WT cells with FasL significantly reduced mROS production and the activation of signaling events leading to IFN-γ. Moreover, Fas deficiency was associated with increased mitochondrial levels of cytochrome C and caspase-3 compared with WT memory-like cells. mROS inhibition significantly reduced the population of disease-associated lpr CD44^hiCD62L^loCD4⁺ T cells and their IFN-γ production. Overall, these findings uncovered a previously unidentified role of Fas/FasL interaction in regulating mROS production by memory-like T cells. This apoptosis-independent Fas activity might contribute to the accumulation of CD44^hiCD62L^loCD4⁺ T cells that produce increased IFN-γ levels in lpr mice. Overall, our findings pinpoint mROS as central regulators of TCR-independent signaling, and support mROS pharmacological targeting to control aberrant immune responses in autoimmune-like disease.Subject terms: Autoimmunity, Cytokines     

Differential Regulation of Effector- and Central-Memory Responses to Toxoplasma gondii Infection by IL-12 Revealed by Tracking of Tgd057-Specific CD8+ T Cells

Production of the pro-inflammatory cytokine IL-12 by innate phagocytes drives the differentiation of IFN-γ-producing effector T cells during Toxoplasma gondii infection. However, the role of IL-12 in the regulation of memory CD8+ T cell differentiation and function during murine toxoplasmosis is unclear. To track memory CTL development, we identified a novel H-2K^b-restricted CTL population specific for the Toxoplasma antigen tgd057. Tgd057-specific CTLs were induced by both vaccination and natural peroral infection, and were representative of the polyclonal CTL population. Tgd057-specific primary effector cells required IL-12 for the differentiation of KLRG1+ effector subpopulations and IFN-γ production in response to restimulation with parasite-infected cells, but not to restimulation with cognate peptide. The effect of IL-12 deficiency during the primary response was profoundly imprinted on memory CTLs, which continued to show defects in cell numbers, KLRG1+ effector memory subpopulation differentiation, and IFN-γ recall responses. Importantly, isolated CD62L^hi KLRG1- CD8+ T cells differentiated in the absence of IL-12 were enhanced in their ability to generate IFN-γ-producing secondary tgd057-specific effector cells. Our data, for the first time, demonstrate the negative impact of IL-12 signaling on the quality of the central memory CTL compartment. Thus, despite the beneficial role of IL-12 in promoting effector differentiation, excessive exposure to IL-12 during CTL priming may limit the development of long-term protective immunity through the decreased fitness of central memory CTL responses.     

Alum Adjuvant Enhances Protection against Respiratory Syncytial Virus but Exacerbates Pulmonary Inflammation by Modulating Multiple Innate and Adaptive Immune Cells

Respiratory syncytial virus (RSV) is well-known for inducing vaccine-enhanced respiratory disease after vaccination of young children with formalin-inactivated RSV (FI-RSV) in alum formulation. Here, we investigated alum adjuvant effects on protection and disease after FI-RSV immunization with or without alum in comparison with live RSV reinfections. Despite viral clearance, live RSV reinfections caused weight loss and substantial pulmonary inflammation probably due to high levels of RSV specific IFN-γ⁺IL4^-, IFN-γ^-TNF-α⁺, IFN-γ⁺TNF-α^- effector CD4 and CD8 T cells. Alum adjuvant significantly improved protection as evidenced by effective viral clearance compared to unadjuvanted FI-RSV. However, in contrast to unadjuvanted FI-RSV, alum-adjuvanted FI-RSV (FI-RSV-A) induced severe vaccine-enhanced RSV disease including weight loss, eosinophilia, and lung histopathology. Alum adjuvant in the FI-RSV-A was found to be mainly responsible for inducing high levels of RSV-specific IFN-γ^-IL4⁺, IFN-γ^-TNF-α⁺ CD4⁺ T cells, and proinflammatory cytokines IL-6 and IL-4 as well as B220⁺ plasmacytoid and CD4⁺ dendritic cells, and inhibiting the induction of IFN-γ⁺CD8 T cells. This study suggests that alum adjuvant in FI-RSV vaccines increases immunogenicity and viral clearance but also induces atypical T helper CD4⁺ T cells and multiple inflammatory dendritic cell subsets responsible for vaccine-enhanced severe RSV disease.     

Differential Effects of IL-12 on Tregs and Non-Treg T Cells: Roles of IFN-γ, IL-2 and IL-2R

Complex interactions between effector T cells and Foxp3⁺ regulatory T cells (Treg) contribute to clinical outcomes in cancer, and autoimmune and infectious diseases. Previous work showed that IL-12 reversed Treg-mediated suppression of CD4⁺Foxp3⁻ T cell (Tconv) proliferation. We and others have also shown that Tregs express T-bet and IFN-γ at sites of Th1 inflammation and that IL-12 induces IFN-γ production by Tregs in vitro. To investigate whether loss of immunosuppression occurs when IFN-γ is expressed by Tregs we treated mouse lymphocyte cultures with IL-12. IFN-γ expression did not decrease the ability of Tregs to suppress Tconv proliferation. Rather, IL-12 treatment decreased Treg frequency and Foxp3 levels in Tregs. We further showed that IL-12 increased IL-2R expression on Tconv and CD8 T cells, diminished its expression on Tregs and decreased IL-2 production by Tconv and CD8 T cells. Together, these IL-12 mediated changes favored the outgrowth of non-Tregs. Additionally, we showed that treatment with a second cytokine, IL-27, decreased IL-2 expression without augmenting Tconv and CD8 T cell proliferation. Notably, IL-27 only slightly modified levels of IL-2R on non-Treg T cells. Together, these results show that IL-12 has multiple effects that modify the balance between Tregs and non-Tregs and support an important role for relative levels of IL-2R but not for IFN-γ expression in IL-12-mediated reversal of Treg immunosuppression.     

Role of 4-1BB Receptor in the Control Played by CD8+ T Cells on IFN-γ Production by Mycobacterium tuberculosis Antigen-Specific CD4+ T Cells

Background

Antigen-specific IFN-γ producing CD4⁺ T cells are the main mediators of protection against Mycobacterium tuberculosis infection both under natural conditions and following vaccination. However these cells are responsible for lung damage and poor vaccine efficacy when not tightly controlled. Discovering new tools to control nonprotective antigen-specific IFN-γ production without affecting protective IFN-γ is a challenge in tuberculosis research.

Methods and Findings

Immunization with DNA encoding Ag85B, a candidate vaccine antigen of Mycobacterium tuberculosis, elicited in mice a low but protective CD4⁺ T cell-mediated IFN-γ response, while in mice primed with DNA and boosted with Ag85B protein a massive increase in IFN-γ response was associated with loss of protection. Both protective and non-protective Ag85B-immunization generated antigen-specific CD8⁺ T cells which suppressed IFN-γ-secreting CD4⁺ T cells. However, ex vivo ligation of 4-1BB, a member of TNF-receptor super-family, reduced the massive, non-protective IFN-γ responses by CD4⁺ T cells in protein-boosted mice without affecting the low protective IFN-γ-secretion in mice immunized with DNA. This selective inhibition was due to the induction of 4-1BB exclusively on CD8⁺ T cells of DNA-primed and protein-boosted mice following Ag85B protein stimulation. The 4-1BB-mediated IFN-γ inhibition did not require soluble IL-10, TGF-β, XCL-1 and MIP-1β. In vivo Ag85B stimulation induced 4-1BB expression on CD8⁺ T cells and in vivo 4-1BB ligation reduced the activation, IFN-γ production and expansion of Ag85B-specific CD4⁺ T cells of DNA-primed and protein-boosted mice.

Conclusion/Significance

Antigen-specific suppressor CD8⁺ T cells are elicited through immunization with the mycobacterial antigen Ag85B. Ligation of 4-1BB receptor further enhanced their suppressive activity on IFN-γ-secreting CD4⁺ T cells. The selective expression of 4-1BB only on CD8⁺ T cells in mice developing a massive, non-protective IFN-γ response opens novel strategies for intervention in tuberculosis pathology and vaccination through T-cell co-stimulatory-based molecular targeting.     

Deficiency in Th2 Cytokine Responses Exacerbate Orthopoxvirus Infection

Ectromelia virus (ECTV) causes mousepox in mice, a disease very similar to smallpox in humans. ECTV and variola virus (VARV), the agent of smallpox, are closely related orthopoxviruses. Mousepox is an excellent small animal model to study the genetic and immunologic basis for resistance and susceptibility of humans to smallpox. Resistance to mousepox is dependent on a strong polarized type 1 immune response, associated with robust natural killer (NK) cell, cytotoxic T lymphocyte (CTL) and gamma interferon (IFN-γ) responses. In contrast, ECTV-susceptible mice generate a type 2 response, associated with weak NK cell, CTL and IFN-γ responses but robust IL-4 responses. Nonetheless, susceptible strains infected with mutant ECTV lacking virus-encoded IFN-γ binding protein (vIFN-γbp) (ECTV-IFN-γbp^Δ) control virus replication through generation of type 1 response. Since the IL-4/IL-13/STAT-6 signaling pathways polarize type 2/T helper 2 (Th2) responses with a corresponding suppression of IFN-γ production, we investigated whether the combined absence of vIFN-γbp, and one or more host genes involved in Th2 response development, influence generation of protective immunity. Most mutant mouse strains infected with wild-type (WT) virus succumbed to disease more rapidly than WT animals. Conversely, the disease outcome was significantly improved in WT mice infected with ECTV-IFN-γbp^Δ but absence of IL-4/IL-13/STAT-6 signaling pathways did not provide any added advantage. Deficiency in IL-13 or STAT-6 resulted in defective CTL responses, higher mortality rates and accelerated deaths. Deficiencies in IL-4/IL-13/STAT-6 signaling pathways significantly reduced the numbers of IFN-γ producing CD4 and CD8 T cells, indicating an absence of a switch to a Th1-like response. Factors contributing to susceptibility or resistance to mousepox are far more complex than a balance between Th1 and Th2 responses.     

Distinct APC Subtypes Drive Spatially Segregated CD4+ and CD8+ T-Cell Effector Activity during Skin Infection with HSV-1

Efficient infection control requires potent T-cell responses at sites of pathogen replication. However, the regulation of T-cell effector function in situ remains poorly understood. Here, we show key differences in the regulation of effector activity between CD4⁺ and CD8⁺ T-cells during skin infection with HSV-1. IFN-γ-producing CD4⁺ T cells disseminated widely throughout the skin and draining lymph nodes (LN), clearly exceeding the epithelial distribution of infectious virus. By contrast, IFN-γ-producing CD8⁺ T cells were only found within the infected epidermal layer of the skin and associated hair follicles. Mechanistically, while various subsets of lymphoid- and skin-derived dendritic cells (DC) elicited IFN-γ production by CD4⁺ T cells, CD8⁺ T cells responded exclusively to infected epidermal cells directly presenting viral antigen. Notably, uninfected cross-presenting DCs from both skin and LNs failed to trigger IFN-γ production by CD8⁺ T-cells. Thus, we describe a previously unappreciated complexity in the regulation of CD4⁺ and CD8⁺ T-cell effector activity that is subset-specific, microanatomically distinct and involves largely non-overlapping types of antigen-presenting cells (APC).     

Discordance in CD4+T-Cell Levels and Viral Loads with Co-Occurrence of Elevated Peripheral TNF-α and IL-4 in Newly Diagnosed HIV-TB Co-Infected Cases

Background

Cytokines are the hallmark of immune response to different pathogens and often dictate the disease outcome. HIV infection and tuberculosis (TB) are more destructive when confronted together than either alone. Clinical data related to the immune status of HIV-TB patients before the initiation of any drug therapy is not well documented. This study aimed to collect the baseline information pertaining to the immune status of HIV-TB co-infected patients and correlate the same with CD4+T cell levels and viral loads at the time of diagnosis prior to any drug therapy.

Methodology/Principal Findings

We analyzed the cytokines, CD4+T cell levels and viral loads to determine the immune environment in HIV-TB co-infection. The study involved four categories namely, Healthy controls (n = 57), TB infected (n = 57), HIV infected (n = 59) and HIV-TB co-infected (n = 57) patients. The multi-partite comparison and correlation between cytokines, CD4+T-cell levels and viral loads prior to drug therapy, showed an altered TH1 and TH2 response, as indicated by the cytokine profiles and skewed IFN-γ/IL-10 ratio. Inadequate CD4+T cell counts in HIV-TB patients did not correlate with high viral loads and vice-versa. When compared to HIV category, 34% of HIV-TB patients had concurrent high plasma levels of IL-4 and TNF-α at the time of diagnosis. TB relapse was observed in 5 of these HIV-TB co-infected patients who also displayed high IFN-γ/IL-10 ratio.

Conclusion/Significance

With these studies, we infer (i) CD4+T-cell levels as baseline criteria to report the disease progression in terms of viral load in HIV-TB co-infected patients can be misleading and (ii) co-occurrence of high TNF-α and IL-4 levels along with a high ratio of IFN-γ/IL-10, prior to drug therapy, may increase the susceptibility of HIV-TB co-infected patients to hyper-inflammation and TB relapse.