Higher Vitamin D Levels before Methotrexate Therapy Initiation Are Associated with Lower Subsequent Mortality in Patients with Rheumatoid Arthritis

(1) Vitamin D deficiency is associated with mortality in the general population and has been observed in one rheumatoid arthritis (RA) cohort. Here, we investigate the relationship between 25-hydroxyvitamin D (25(OH)D) levels before methotrexate (MTX) therapy initiation in patients with RA and the subsequent all-cause mortality in a national Veterans Affairs (VA) cohort. (2) This is a retrospective study on RA patients time-oriented around the initial MTX prescription and 25(OH)D levels before starting MTX. We examined survival in patients with 25(OH)D levels > 50 nmol/L and ≤50 nmol/L using the Cox Proportional Hazard Model and fully adjusted for risk factors. (3) In total, 15,109 RA patients were included in the nationwide cohort. RA patients with 25(OH)D levels > 50 nmol/L before starting MTX had a 28% reduced risk of mortality when compared to those with levels ≤ 50 nmol/L (HR: 0.72, CI: 0.64-0.80, p < 0.001) after adjusting for traditional risk factors. (4) In this national RA cohort receiving standard-of-care MTX, patients with 25(OH)D levels > 50 nmol/L have a lower subsequent mortality when compared to those with 25(OH)D levels ≤ 50 nmol/L. It remains to be determined whether increasing Vitamin D levels in RA patients initially found to be Vitamin D deficient impacts their all-cause mortality.

Cytomegalovirus Infection Facilitates the Costimulation of CD57+CD28- CD8 T Cells in HIV Infection and Atherosclerosis via the CD2-LFA-3 Axis

CD8 T cells are emerging as important mediators in atherosclerosis and cardiovascular disease (CVD). Immune activation may play a particular role in people with HIV (PWH) who are at an increased risk of CVD, even after controlling for known CVD risk factors. Latent CMV infection is associated with increased CVD risk for both PWH and people without HIV, and human CMV-specific CD4 and CD8 T cells are enriched for an immunosenescent phenotype. We previously showed that CMV coinfection in PWH promotes vascular homing and activation of inflammatory CD4 T cells through the CD2-LFA-3 axis. However, the role of CD2/LFA3 costimulation of CD8 T cells in PWH with CMV has yet to be described. In the present study, we demonstrate that CD2 expression on CX3CR1+CD57+CD28- inflammescent CD8 T cells is increased on cells from CMV-seropositive PWH. In vitro CD2/LFA-3 costimulation enhances TCR-mediated activation of these inflammatory CD8 memory T cells. Finally, we show that LFA-3 is highly expressed in aortas of SIV-infected rhesus macaques and in atherosclerotic plaques of people without HIV. Our findings are consistent with a model in which CMV infection enhances CD2 expression on highly proinflammatory CD8 T cells that can then be stimulated by LFA-3 expressed in the vasculature, even in the absence of CD28 costimulation. This model, in which CMV infection exacerbates toxic cytokine and granzyme production by CD8 T cells within the vasculature, highlights a potential therapeutic target in atherosclerosis development and progression, especially for PWH.

Rheumatoid arthritis and older age are associated with lower humoral and cellular immune response to primary series COVID-19 mRNA vaccine

OBJECTIVE

People with autoimmune disease have worse COVID-19 infection-related outcomes, lower antibody responses to COVID-19 vaccine, and higher rates of breakthrough infection. Immunosuppressive medications used to treat rheumatoid arthritis (RA) are associated with lower COVID-19 vaccine responses, though independent contributions of comorbidities, T-cell immunity, and age are less clear. We sought to test the hypothesis that RA, immunosuppressive medications used to treat RA, and older age, contribute to reduced B and T cell response to COVID-19 vaccine.

METHODS

We evaluated serum samples, taken the day of 1st vaccine dose, the day of 2nd dose, 2-6 weeks after 2nd dose, 7-12 weeks after 2nd dose, 13-24 weeks after 2nd dose, and 2-6 weeks after the 3rd dose, for anti-spike IgG and neutralizing antibody levels to Wuhan and Omicron BA.1 and peripheral blood mononuclear cells (PBMC) for spike-specific IFN-γ and IL-2 production by ELISPOT assay in 46 RA and 101 non-autoimmune control participants before and after the primary series COVID-19 mRNA vaccination.

RESULTS

RA participants had lower spike-specific IgG and Wuhan-strain neutralizing antibody levels 2-6 weeks compared to controls after the second dose of primary vaccine series. Neutralizing antibody levels against Omicron BA.1 were low in both groups. IFN-γ production correlated with Wuhan neutralizing antibody levels, while older age negatively correlated with spike-specific IL-2, IFN-γ and IgG. Lower antibody levels were associated with older age, RA status, and medication usage, while lower T cell responses were associated primarily with older age.

CONCLUSIONS

These data indicate lower COVID-19 mRNA vaccine-induced antibody levels in persons with RA compared to individuals without RA, likely partially attributable to immune suppressive medications. At the same time, older age is associated with lower antibody and cellular immune response to COVID-19 vaccines.

Distinct SARS-CoV-2 specific NLRP3 and IL-1β responses in T cells of aging patients during acute COVID-19 infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes Coronavirus Disease 2019 (COVID-19) that presents with varied clinical manifestations ranging from asymptomatic or mild infections and pneumonia to severe cases associated with cytokine storm, acute respiratory distress syndrome (ARDS), and even death. The underlying mechanisms contributing to these differences are unclear, although exacerbated inflammatory sequelae resulting from infection have been implicated. While advanced aging is a known risk factor, the precise immune parameters that determine the outcome of SARS-CoV-2 infection in elderly individuals are not understood. Here, we found aging-associated (age ≥61) intrinsic changes in T cell responses when compared to those from individuals aged ≤ 60, even among COVID-positive patients with mild symptoms. Specifically, when stimulated with SARS-CoV-2 peptides in vitro, peripheral blood mononuclear cell (PBMC) CD4+ and CD8+ T cells from individuals aged ≥61 showed a diminished capacity to produce IFN-γ and IL-1β. Although they did not have severe disease, aged individuals also showed a higher frequency of PD-1+ cells and significantly diminished IFN-γ/PD-1 ratios among T lymphocytes upon SARS-CoV-2 peptide stimulation. Impaired T cell IL-1β expression coincided with reduced NLRP3 levels in T lymphocytes. However, the expression of these molecules was not affected in the monocytes of individuals aged ≥61. Together, these data reveal SARS-CoV-2-specific CD4+ and CD8+ T-cell intrinsic cytokine alterations in the individuals older than 61 and may provide new insights into dysregulated COVID-directed immune responses in the elderly.

Endotoxemia Associated with Liver Disease Correlates with Systemic Inflammation and T Cell Exhaustion in Hepatitis C Virus Infection

Both acute and chronic hepatitis C virus (HCV) infections are characterized by inflammation. HCV and reduced liver blood filtration contribute to inflammation; however, the mechanisms of systemic immune activation and dysfunction as a result of HCV infection are not clear. We measured circulating inflammatory mediators (IL-6, IP10, sCD163, sCD14), indices of endotoxemia (EndoCab, LBP, FABP), and T cell markers of exhaustion and senescence (PD-1, TIGIT, CD57, KLRG-1) in HCV-infected participants, and followed a small cohort after direct-acting anti-viral therapy. IL-6, IP10, Endocab, LBP, and FABP were elevated in HCV participants, as were T cell co-expression of exhaustion and senescence markers. We found positive associations between IL-6, IP10, EndoCab, LBP, and co-expression of T cell markers of exhaustion and senescence. We also found numerous associations between reduced liver function, as measured by plasma albumin levels, and T cell exhaustion/senescence, inflammation, and endotoxemia. We found positive associations between liver stiffness (TE score) and plasma levels of IL-6, IP10, and LBP. Lastly, plasma IP10 and the proportion of CD8 T cells co-expressing PD-1 and CD57 decreased after initiation of direct-acting anti-viral therapy. Although associations do not prove causality, our results support the model that translocation of microbial products, resulting from decreased liver blood filtration, during HCV infection drives chronic inflammation that results in T cell exhaustion/senescence and contributes to systemic immune dysfunction.

Interleukin 6 Blockade With Tocilizumab Diminishes Indices of Inflammation That Are Linked to Mortality in Treated Human Immunodeficiency Virus Infection

BACKGROUND

People with human immunodeficiency virus (PWH) are at increased risk for comorbidities, and plasma interleukin 6 (IL-6) levels are among the most robust predictors of these outcomes. Tocilizumab (TCZ) blocks the receptor for IL-6, inhibiting functions of this cytokine.

METHODS

This was a 40-week, placebo-controlled, crossover trial (NCT02049437) where PWH on stable antiretroviral therapy (ART) were randomized to receive 3 monthly doses of TCZ or matching placebo intravenously. Following a 10-week treatment period and a 12-week washout, participants were switched to the opposite treatment. The primary endpoints were safety and posttreatment levels of C-reactive protein (CRP) and CD4+ T-cell cycling. Secondary endpoints included changes in inflammatory indices and lipid levels.

RESULTS

There were 9 treatment-related toxicities of grade 2 or greater during TCZ administration (mostly neutropenia) and 2 during placebo administration. Thirty-one of 34 participants completed the study and were included in a modified intent-to-treat analysis. TCZ reduced levels of CRP (median decrease, 1819.9 ng/mL, P < .0001; effect size, 0.87) and reduced inflammatory markers in PWH, including D-dimer, soluble CD14, and tumor necrosis factor receptors. T-cell cycling tended to decrease in all maturation subsets after TCZ administration, but was only significant among naive CD4 T cells. Lipid levels, including lipid classes that have been related to cardiovascular disease risk, increased during TCZ treatment.

CONCLUSIONS

TCZ is safe and decreases inflammation in PWH; IL-6 is a key driver of the inflammatory environment that predicts morbidity and mortality in ART-treated PWH. The clinical significance of lipid elevations during TCZ treatment requires further study. Clinical Trials Registration. NCT02049437.

The US Department of Veterans Affairs Science and Health Initiative to Combat Infectious and Emerging Life-Threatening Diseases (VA SHIELD): A Biorepository Addressing National Health Threats

Background

The coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has demonstrated the need to share data and biospecimens broadly to optimize clinical outcomes for US military Veterans.

Methods

In response, the Veterans Health Administration established VA SHIELD (Science and Health Initiative to Combat Infectious and Emerging Life-threatening Diseases), a comprehensive biorepository of specimens and clinical data from affected Veterans to advance research and public health surveillance and to improve diagnostic and therapeutic capabilities.

Results

VA SHIELD now comprises 12 sites collecting de-identified biospecimens from US Veterans affected by SARS-CoV-2. In addition, 2 biorepository sites, a data processing center, and a coordinating center have been established under the direction of the Veterans Affairs Office of Research and Development. Phase 1 of VA SHIELD comprises 34 157 samples. Of these, 83.8% had positive tests for SARS-CoV-2, with the remainder serving as contemporaneous controls. The samples include nasopharyngeal swabs (57.9%), plasma (27.9%), and sera (12.5%). The associated clinical and demographic information available permits the evaluation of biological data in the context of patient demographics, clinical experience and management, vaccinations, and comorbidities.

Conclusions

VA SHIELD is representative of US national diversity with a significant potential to impact national healthcare. VA SHIELD will support future projects designed to better understand SARS-CoV-2 and other emergent healthcare crises. To the extent possible, VA SHIELD will facilitate the discovery of diagnostics and therapeutics intended to diminish COVID-19 morbidity and mortality and to reduce the impact of new emerging threats to the health of US Veterans and populations worldwide.

High Red Cell Distribution Width and Low Absolute Lymphocyte Count Associate With Subsequent Mortality in HCV Infection

Background:

Hepatitis-C virus (HCV) chronic infection can lead to cirrhosis, hepatocellular carcinoma (HCC), end-stage liver disease, cardiovascular disease (CVD), and mortality. Transient Elastography (TE) is used to non-invasively assess fibrosis. Whether immune monitoring provides additive prognostic value is not established. Increased red-cell distribution width (RDW) and decreased absolute lymphocyte count (ALC) predict mortality in those without liver disease. Whether these relationships remain during HCV infection is unknown.

Materials and Methods:

A retrospective cohort of 1,715 single-site VA Liver Clinic patients receiving Transient Elastography (TE) 2014-2019 to evaluate HCV-associated liver damage were evaluated for RDW and ALC in relation to traditional parameters of cardiovascular risk, liver health, development of HCC, and mortality.

Results:

The cohort was 97% male, 55% African American, 26% with diabetes mellitus, 67% with hypertension, and 66% with tobacco use. After TE, 3% were subsequently diagnosed with HCC, and 12% (n=208) died. Most deaths (n=189) were due to non-liver causes. The TE score associated with prevalent CVD, positively correlated with atherosclerotic cardiovascular disease (ASCVD) 10-Year Risk Score, age, RDW, and negatively correlated with ALC. Patients with anisocytosis (RDW above 14%) or lymphopenia (ALC level under 1.2×10⁹/L) had greater subsequent all-cause mortality, even after adjusting for age, TE score, and comorbidities. TE score, and to a modest degree RDW, were associated with subsequent liver-associated mortality, while TE score, RDW, and ALC were each independently associated with non-liver cause of death.

Conclusion:

Widely available mortality calculators generally require multiple pieces of clinical information. RDW and ALC, parameters collected on a single laboratory test that is commonly performed, prior to HCV therapy may be pragmatic markers of long-term risk of mortality.

Variable Normalization of Naïve CD4+ Lymphopenia and Markers of Monocyte and T Cell Activation over the Course of Direct-Acting Anti-Viral Treatment of Chronic Hepatitis C Virus Infection

Chronic hepatitis C virus (HCV) infection is associated with naïve CD4+ T cell lymphopenia and long-standing/persistent elevation of cellular and soluble immune activation parameters, the latter heightened in the setting of HIV co-infection. The underlying mechanisms are not completely understood. However, we recently reported that accelerated peripheral cell death may contribute to naïve CD4+ T cell loss and that mechanistic relationships between monocyte activation, T cell activation, and soluble inflammatory mediators may also contribute. Chronic HCV infection can be cured by direct-acting anti-viral (DAA) therapy, and success is defined as sustained virological response (SVR, undetectable HCV RNA (ribonucleic acid) at 12 weeks after DAA treatment completion). However, there is no general consensus on the short-term and long-term immunological outcomes of DAA therapy. Here, we consolidate previous reports on the partial normalization of naïve CD4+ lymphopenia and T cell immune activation and the apparent irreversibility of monocyte activation following DAA therapy in HCV infected and HCV/HIV co-infected individuals. Further, advanced age and cirrhosis are associated with delayed or abrogation of immune reconstitution after DAA therapy, an indication that non-viral factors also likely contribute to host immune dysregulation in HCV infection.

Naïve CD4+ T Cell Lymphopenia and Apoptosis in Chronic Hepatitis C Virus Infection Is Driven by the CD31+ Subset and Is Partially Normalized in Direct-Acting Antiviral Treated Persons

Background

The mechanisms underlying naïve CD4+ lymphopenia during chronic Hepatitis C Virus (HCV) infection are unclear. Whether direct-acting antiviral (DAA) therapy restores peripheral naïve CD4+ T cell numbers and function is unknown.

Methods

We enumerated frequencies and counts of peripheral naïve CD4+, CD4+CD31+ and CD4+CD31- T cells by flow cytometry in a cross sectional analysis comparing chronic HCV infected (n=34), DAA-treated(n=29), and age-range matched controls (n=25), as well as in a longitudinal cohort of HCV DAA treated persons (n=16). The cross-sectional cohort was stratified by cirrhosis state. Cell apoptosis/survival (AnnexinV+7AAD+/BCL-2 labeling) and cell cycle entry (Ki67 expression) of CD31+ and CD31- naïve CD4+ T cells was analyzed directly ex vivo and following 3 and 5 days of in vitro culture with media, interleukin (IL) -7 or CD3/CD28 activator.

Results

In the cross-sectional cohort, naïve CD4+ proportions were lower in chronic HCV infected persons compared to controls and DAA-treated persons, an effect in part attributed to cirrhosis. Age was associated with naïve cell counts and proportions in HCV infected and treated persons as well. Naïve CD4+ cell proportions negatively correlated with plasma levels of soluble CD14 following therapy in DAA-treated persons. Naïve CD4+ cells from HCV infected persons exhibited greater direct ex vivo apoptosis and cell-cycling compared to cells from DAA-treated persons and controls, and this was localized to the CD4+CD31+ subset. On the other hand, no remarkable differences in expression of BCL-2 or IL-7 Receptor (CD127) at baseline or following in vitro media or IL7 containing culture were observed. In the longitudinal cohort, naïve CD4+CD31+/CD31- ratio tended to increase 24 weeks after DAA therapy initiation.

Conclusions

Activation and apoptosis of peripheral naïve CD4+CD31+ T cells appear to contribute to naïve CD4+ lymphopenia in chronic HCV infection, and this defect is partially reversible with HCV DAA therapy. Age and cirrhosis -associated naïve CD4+ lymphopenia is present both before and after HCV DAA therapy. These findings have implications for restoration of host immune function after DAA therapy.

Markers of T Cell Exhaustion and Senescence and Their Relationship to Plasma TGF-β Levels in Treated HIV+ Immune Non-responders

Background: Immune non-responders (INR) are HIV+, ART-controlled (>2 yrs) people who fail to reconstitute their CD4 T cell numbers. Systemic inflammation and markers of T cell senescence and exhaustion are observed in INR. This study aims to investigate T cell senescence and exhaustion and their possible association with soluble immune mediators and to understand the immune profile of HIV-infected INR. Selected participants were <50 years old to control for the confounder of older age. Methods: Plasma levels of IL-6, IP10, sCD14, sCD163, and TGF-β and markers of T cell exhaustion (PD-1, TIGIT) and senescence (CD57, KLRG-1) were measured in ART-treated, HIV+ participants grouped by CD4 T cell counts (n = 63). Immune parameters were also measured in HIV-uninfected, age distribution-matched controls (HC; n = 30). Associations between T cell markers of exhaustion and senescence and plasma levels of immune mediators were examined by Spearman rank order statistics. Results: Proportions of CD4 T cell subsets expressing markers of exhaustion (PD-1, TIGIT) and senescence (CD57, KLRG-1) were elevated in HIV+ participants. When comparing proportions between INR and IR, INR had higher proportions of CD4 memory PD-1+, EM CD57+, TEM TIGIT+ and CD8 EM and TEM TIGIT+ cells. Plasma levels of IL-6, IP10, and sCD14 were elevated during HIV infection. IP10 was higher in INR. Plasma TGF-β levels and CD4 cycling proportions of T regulatory cells were lower in INR. Proportions of CD4 T cells expressing TIGIT, PD-1, and CD57 positively correlated with plasma levels of IL-6. Plasma levels of TGF-β negatively correlated with proportions of TIGIT+ and PD-1+ T cell subsets. Conclusions: INR have lower levels of TGF-β and decreased proportions of cycling CD4 T regulatory cells and may have difficulty controlling inflammation. IP10 is elevated in INR and is linked to higher proportions of T cell exhaustion and senescence seen in INR.

Hepatitis C Virus (HCV) Direct-Acting Antiviral Therapy in Persons With Human Immunodeficiency Virus-HCV Genotype 1 Coinfection Resulting in High Rate of Sustained Virologic Response and Variable in Normalization of Soluble Markers of Immune Activation

BACKGROUND

Hepatitis C virus (HCV) direct-acting antivirals are highly effective. Less is known about changes in markers of immune activation in persons with human immunodeficiency virus (HIV) in whom a sustained virologic response (SVR) is achieved.

METHODS

We conducted a nonrandomized clinical trial of 12 or 24 weeks of paritaprevir-ritonavir-ombitasvir plus dasabuvir (PrOD) with or without ribavirin in persons with HCV-1/HIV coinfection suppressed with antiretroviral therapy. Plasma HCV, soluble CD14 (sCD14), interferon-inducible protein 10, soluble CD163 (sCD163), interleukin 6 (IL-6), interleukin 18, monocyte chemoattractant protein (MCP-1), autotaxin (ATX), and Mac2-binding protein (Mac2BP) were measured over 48 weeks.

RESULTS

Participants were treated with PrOD for 12 (n = 9) or 24 (n = 36) weeks; the SVR rate at 12 weeks was 93%. At baseline, cirrhosis was associated with higher ATX and MCP-1, female sex with higher ATX and IL-6, older age with higher Mac2BP, higher body mass index with higher ATX, and HIV-1 protease inhibitor use with higher sCD14 levels. In those with SVR, interferon-inducible protein 10, ATX, and Mac2BP levels declined by week 2, interleukin 18 levels declined by the end of treatment, sCD14 levels did not change, and sCD163, MCP-1, and IL-6 levels changed at a single time point.

CONCLUSIONS

During HIV/HCV coinfection, plasma immune activation marker heterogeneity is in part attributable to age, sex, cirrhosis, body mass index, and/or type of antiretroviral therapy. HCV treatment with paritaprevir-ritonavir-ombitasvir plus dasabuvir is highly effective and is associated with variable rate and magnitude of decline in markers of immune activation.

CLINICAL TRIALS REGISTRATION

NCT02194998.

Inflammescent CX3CR1+CD57+CD8+ T cells are generated and expanded by IL-15

HIV infection is associated with an increase in the proportion of activated CD8+ memory T cells (Tmem) that express CX3CR1, but how these cells are generated and maintained in vivo is unclear. We demonstrate that increased CX3CR1 expression on CD8+ Tmem in people living with HIV (PLWH) is dependent on coinfection with human CMV, and CX3CR1+CD8+ Tmem are enriched for a putatively immunosenescent CD57+CD28- phenotype. The cytokine IL-15 promotes the phenotype, survival, and proliferation of CX3CR1+CD57+CD8+ Tmem in vitro, whereas T cell receptor stimulation leads to their death. IL-15-driven survival is dependent on STAT5 and Bcl-2 activity, and IL-15-induced proliferation requires STAT5 and mTORC1. Thus, we identify mechanistic pathways that could explain how "inflammescent" CX3CR1+CD57+ CD8+ Tmem dominate the overall memory T cell pool in CMV-seropositive PLWH and that support reevaluation of immune senescence as a nonproliferative dead end.

Inflammescent CX3CR1+CD57+CD8+ T cells are generated and expanded by IL-15

HIV infection is associated with an increase in the proportion of activated CD8+ memory T cells (Tmem) that express CX3CR1, but how these cells are generated and maintained in vivo is unclear. We demonstrate that increased CX3CR1 expression on CD8+ Tmem in people living with HIV (PLWH) is dependent on coinfection with human CMV, and CX3CR1+CD8+ Tmem are enriched for a putatively immunosenescent CD57+CD28- phenotype. The cytokine IL-15 promotes the phenotype, survival, and proliferation of CX3CR1+CD57+CD8+ Tmem in vitro, whereas T cell receptor stimulation leads to their death. IL-15-driven survival is dependent on STAT5 and Bcl-2 activity, and IL-15-induced proliferation requires STAT5 and mTORC1. Thus, we identify mechanistic pathways that could explain how "inflammescent" CX3CR1+CD57+ CD8+ Tmem dominate the overall memory T cell pool in CMV-seropositive PLWH and that support reevaluation of immune senescence as a nonproliferative dead end.

Cytomegalovirus Coinfection Is Associated with Increased Vascular-Homing CD57+ CD4 T Cells in HIV Infection

Cytotoxic CD4 T cells are linked to cardiovascular morbidities and accumulate in both HIV and CMV infections, both of which are associated with increased risk of cardiovascular disease (CVD). In this study, we identify CMV coinfection as a major driver of the cytotoxic phenotype, characterized by elevated CD57 expression and reduced CD28 expression, in circulating CD4 T cells from people living with HIV infection, and investigate potential mechanisms linking this cell population to CVD. We find that human CD57+ CD4 T cells express high levels of the costimulatory receptor CD2 and that CD2/LFA-3 costimulation results in a more robust and polyfunctional effector response to TCR signals, compared with CD28-mediated costimulation. CD57+ CD4 T cells also express the vascular endothelium-homing receptor CX3CR1 and migrate toward CX3CL1-expressing endothelial cells in vitro. IL-15 promotes the cytotoxic phenotype, elevates CX3CR1 expression, and enhances the trafficking of CD57+ CD4 T cells to endothelium and may therefore be important in linking these cells to cardiovascular complications. Finally, we demonstrate the presence of activated CD57+ CD4 T cells and expression of CX3CL1 and LFA-3 in atherosclerotic plaque tissues from HIV-uninfected donors. Our findings are consistent with a model in which cytotoxic CD4 T cells contribute to CVD in HIV/CMV coinfection and in atherosclerosis via CX3CR1-mediated trafficking and CD2/LFA-3-mediated costimulation. This study identifies several targets for therapeutic interventions and may help bridge the gap in understanding how CMV infection and immunity are linked to increased cardiovascular risk in people living with HIV infection.

Cytomegalovirus coinfection is associated with increased vascular-homing CD57+ CD4 T cells in HIV infection

Cytotoxic CD4 T cells are linked to cardiovascular morbidities and accumulate in both human immunodeficiency virus (HIV) and cytomegalovirus (CMV) infections, both of which are associated with increased risk of cardiovascular disease. Here we identify CMV coinfection as a major driver of the cytotoxic phenotype – characterized by elevated CD57 expression and reduced CD28 expression – in circulating CD4 T cells from people living with HIV infection (PLWH). We find that CD57+ CD4 T cells express high levels of the costimulatory receptor CD2 and that CD2/LFA-3 costimulation results in a more robust and polyfunctional effector response to T cell receptor (TCR) signals, compared to CD28-mediated costimulation. CD57+ CD4 T cells also express the vascular endothelium-homing receptor CX3CR1 and migrate toward CX3CL1-expressing endothelial cells in vitro. IL-15 promotes the cytotoxic phenotype, elevates CX3CR1 expression, and enhances the trafficking of CD57+ CD4 T cells, and may therefore be important in linking these cells to cardiovascular complications. Finally, we demonstrate the presence of CD57+ CD4 T cells and expression of IL-15, CX3CL1, and LFA-3 in atherosclerotic plaque tissues from HIV-uninfected donors. Our findings are consistent with a model in which cytotoxic CD4 T cells contribute to cardiovascular disease in HIV/CMV coinfection and in atherosclerosis via CX3CR1-mediated trafficking and CD2-mediated costimulation, and may help bridge the gap in understanding how CMV infection and immunity are linked to increased cardiovascular risk in PLWH.

Cycling CD4+ T cells in HIV-infected immune nonresponders have mitochondrial dysfunction

Immune nonresponder (INR) HIV-1-infected subjects are characterized by their inability to reconstitute the CD4+ T cell pool after antiretroviral therapy. This is linked to poor clinical outcome. Mechanisms underlying immune reconstitution failure are poorly understood, although, counterintuitively, INRs often have increased frequencies of circulating CD4+ T cells in the cell cycle. While cycling CD4+ T cells from healthy controls and HIV+ patients with restored CD4+ T cell numbers complete cell division in vitro, cycling CD4+ T cells from INRs do not. Here, we show that cells with the phenotype and transcriptional profile of Tregs were enriched among cycling cells in health and in HIV infection. Yet there were diminished frequencies and numbers of Tregs among cycling CD4+ T cells in INRs, and cycling CD4+ T cells from INR subjects displayed transcriptional profiles associated with the impaired development and maintenance of functional Tregs. Flow cytometric assessment of TGF-β activity confirmed the dysfunction of Tregs in INR subjects. Transcriptional profiling and flow cytometry revealed diminished mitochondrial fitness in Tregs among INRs, and cycling Tregs from INRs had low expression of the mitochondrial biogenesis regulators peroxisome proliferator-activated receptor γ coactivator 1-α (PGC1α) and transcription factor A for mitochondria (TFAM). In vitro exposure to IL-15 allowed cells to complete division, restored the expression of PGC1α and TFAM, and regenerated mitochondrial fitness in the cycling Tregs of INRs. Our data suggest that rescuing mitochondrial function could correct the immune dysfunction characteristic of Tregs in HIV-1-infected subjects who fail to restore CD4+ T cells during antiretroviral therapy.

Soluble Markers of Immune Activation Differentially Normalize and Selectively Associate with Improvement in AST, ALT, Albumin, and Transient Elastography During IFN-Free HCV Therapy

Background

During chronic hepatitis C virus (HCV) infection, Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT) levels mark active liver inflammation and tissue damage, while albumin reflects synthetic liver function and nutritional status. Transient Elastography (TE) is a clinical measure of liver stiffness that facilitates evaluation of liver damage stage. While a portion of the TE score is attributable to liver fibrosis and relatively irreversible damage, another component of the TE score is attributable to liver inflammation or edema. Markers of inflammation during chronic HCV infection include soluble markers of immune activation, which are also associated with morbid outcome (including cardiovascular disease and liver-disease progression). Whether soluble markers of immune activation or changes in their level during HCV therapy relate to normalization of AST, ALT, Albumin, or TE score, is not clear.

Methods

We evaluated soluble markers of immune activation (plasma sCD14, IL-6, sCD163, autotaxin [ATX], and Mac2BP) and TE score, and their relationship in 20 HCV-infected patients before, during, and after HCV-directed IFN-free direct-acting antiviral (DAA) therapy. We evaluated normalization of parameters and the relationship between each over a 6-month window.

Results

Before therapy, serum AST levels positively correlated with plasma levels of sCD14, sCD163, and Mac2BP, while ALT levels positively correlated with Mac2BP. Serum albumin level negatively correlated with plasma IL-6 and ATX levels. IFN-free therapy uniformly resulted in sustained virological response at 12 and 24 weeks after therapy completion. After initiation of therapy AST and ALT normalized, while levels of ATX, Mac2BP, sCD163, and TE score partially normalized over 6 months. Additionally, change in AST level and APRI score correlated with change in sCD163, IL-6, and Mac2BP levels, and change in ALT correlated with change in IL-6 and Mac2BP levels. Improvement in TE score correlated with a decrease in the level of sCD14 at week 4, and almost statistically significant with decrease in sCD14 at weeks 20-24 after initiation of IFN-free HCV therapy.

Conclusions

Soluble markers of immune activation normalize or partially normalize at different rates after initiation of curative HCV DAA therapy, and TE scores improve, with wide variability in the degree of absolute improvement in liver stiffness from patient to patient. Decline magnitude of sCD14 was associated with improvement in TE score, while magnitude of improvement in AST correlated with reduction in sCD163 levels. These data provide support for a model where monocyte/Kupffer cell activation may account for a portion of the liver inflammation and edema, which is at least partially reversible following initiation of HCV DAA therapy.

Cytokines and T-Cell Homeostasis in HIV Infection

Untreated human immunodeficiency virus (HIV) infection is characterized by progressive CD4(+) T-cell depletion and CD8(+) T-cell expansion, and CD4(+) T-cell depletion is linked directly to the risk for opportunistic infections and infection-associated mortality. With suppression of HIV replication by antiretroviral therapy, circulating CD4(+) Tcell numbers typically improve while CD8(+) T-cell expansion persists, and both CD4(+) T-cell cytopenia and CD8(+) T-cell expansion are associated with morbidity and mortality. In this brief review, we report on the role that selected homeostatic and inflammatory cytokines may play both in the failure of CD4(+) T-cell restoration and the CD8(+) T-cell expansion that characterize HIV infection.

During Hepatitis C Virus (HCV) Infection and HCV-HIV Coinfection, an Elevated Plasma Level of Autotaxin Is Associated With Lysophosphatidic Acid and Markers of Immune Activation That Normalize During Interferon-Free HCV Therapy

BACKGROUND

 Immune activation predicts morbidity during hepatitis C virus (HCV) infection and human immunodeficiency virus (HIV) infection, although mechanisms underlying immune activation are unclear. Plasma levels of autotaxin and its enzymatic product, lysophosphatidic acid (LPA), are elevated during HCV infection, and LPA activates immunocytes, but whether this contributes to immune activation is unknown.

METHODS

 We evaluated plasma levels of autotaxin, interleukin 6 (IL-6), soluble CD14 (sCD14), soluble CD163 (sCD163), and Mac2 binding protein (Mac2BP) during HCV infection, HIV infection, and HCV-HIV coinfection, as well as in uninfected controls, before and after HIV antiretroviral therapy (ART) initiation and during interferon-free HCV therapy.

RESULTS

 We observed greater plasma autotaxin levels in HCV-infected and HCV-HIV-coinfected participants, compared with uninfected participants, primarily those with a higher ratio of aspartate aminotransferase level to platelet count. Autotaxin levels correlated with IL-6, sCD14, sCD163, Mac2BP, and LPA levels in HCV-infected participants and with Mac2BP levels in HCV-HIV-coinfected participants, while in HIV-infected individuals, sCD14 levels correlated with Mac2BP levels. Autotaxin, LPA, and sCD14 levels normalized, while sCD163 and Mac2BP levels partially normalized within 6 months of starting interferon-free HCV therapy. sCD163 and IL-6 levels normalized within 6 months of starting ART for HIV infection. In vitro, LPA activated monocytes.

CONCLUSIONS

 These data indicate that elevated levels of autotaxin and soluble markers of immune activation during HCV infection are partially reversible within 6 months of initiating interferon-free HCV treatment and that autotaxin may be causally linked to immune activation during HCV infection and HCV-HIV coinfection.

IL-15 promotes activation and expansion of CD8+ T cells in HIV-1 infection

In HIV-1-infected patients, increased numbers of circulating CD8+ T cells are linked to increased risk of morbidity and mortality. Here, we identified a bystander mechanism that promotes CD8 T cell activation and expansion in untreated HIV-1-infected patients. Compared with healthy controls, untreated HIV-1-infected patients have an increased population of proliferating, granzyme B+, CD8+ T cells in circulation. Vβ expression and deep sequencing of CDR3 revealed that in untreated HIV-1 infection, cycling memory CD8 T cells possess a broad T cell repertoire that reflects the repertoire of the resting population. This suggests that cycling is driven by bystander activation, rather than specific antigen exposure. Treatment of peripheral blood mononuclear cells with IL-15 induced a cycling, granzyme B+ phenotype in CD8+ T cells. Moreover, elevated IL-15 expression in the lymph nodes of untreated HIV-1-infected patients correlated with circulating CD8+ T cell counts and was normalized in these patients following antiretroviral therapy. Together, these results suggest that IL-15 drives bystander activation of CD8+ T cells, which predicts disease progression in untreated HIV-1-infected patients and suggests that elevated IL-15 may also drive CD8+ T cell expansion that is linked to increased morbidity and mortality in treated patients.

CD8 T-Cell Expansion and Inflammation Linked to CMV Coinfection in ART-treated HIV Infection

BACKGROUND

Persistent CD8 T-cell expansion, low CD4/CD8 T-cell ratios, and heightened inflammation persist in antiretroviral therapy (ART)-treated human immunodeficiency virus (HIV) infection and are associated with increased risk of morbid outcomes. We explored the role of cytomegalovirus (CMV) infection in CD8 lymphocytosis and inflammation in ART-treated HIV infection.

METHODS

Absolute CD4 and CD8 T-cell counts were abstracted from clinical records and compared among 32 HIV-infected CMV-seronegative subjects, 126 age, CD4 and gender-matched HIV-infected CMV-seropositive subjects, and among 21 HIV-uninfected controls (9 CMV-negative, 12 CMV-positive). Plasma inflammatory indices were measured in a subset by ELISA.

RESULTS

Median CD8 counts/µL were higher in HIV-positive/CMV-positive patients (795) than in HIV-positive/CMV-negative subjects (522, P = .006) or in healthy controls (451, P = .0007), whereas CD8 T-cell counts were similar to controls' levels in HIV-positive/CMV-negative subjects. Higher plasma levels of IP-10 (P = .0011), TNF-RII (P = .0002), and D-dimer (P = .0444) were also found in coinfected patients than in HIV-positive/CMV-negative subjects.

CONCLUSIONS

CMV infection is associated with higher CD8 T-cell counts, resultant lower CD4/CD8 ratios, and increased systemic inflammation in ART-treated HIV infection. CMV infection may contribute to risk for morbid outcomes in treated HIV infection.

Inflammatory cytokines drive CD4+ T-cell cycling and impaired responsiveness to interleukin 7: implications for immune failure in HIV disease

BACKGROUND

Systemic inflammation has been linked to a failure to normalize CD4(+) T-cell numbers in treated human immunodeficiency virus (HIV) infection. Although inflammatory cytokines such as interleukin 6 (IL-6) are predictors of disease progression in treated HIV infection, it is not clear how or whether inflammatory mediators contribute to immune restoration failure.

METHODS

We examined the in vitro effects of IL-6 and interleukin 1β (IL-1β) on peripheral blood T-cell cycling and CD127 surface expression.

RESULTS

The proinflammatory cytokine IL-1β induces cell cycling and turnover of memory CD4(+) T cells, and IL-6 can induce low-level cycling of naive T cells. Both IL-1β and IL-6 can decrease T-cell surface expression and RNA levels of CD127, the interleukin 7 receptor α chain (IL-7Rα). Preexposure of healthy peripheral blood mononuclear cells (PBMCs) to IL-6 or IL-1β attenuates IL-7-induced Stat5 phosphorylation and induction of the prosurvival factor Bcl-2 and the gut homing integrin α4β7. We found elevated expression of IL-1β in the lymphoid tissues of patients with HIV infection that did not normalize with antiretroviral therapy.

CONCLUSIONS

Induction of CD4(+) T-cell turnover and diminished T-cell responsiveness to IL-7 by IL-1β and IL-6 exposure may contribute to the lack of CD4(+) T-cell reconstitution in treated HIV-infected subjects.

HIV-1 is not a major driver of increased plasma IL-6 levels in chronic HIV-1 disease

OBJECTIVE

Increased plasma IL-6 levels have been associated with HIV-1 disease progression risk, yet the drivers of IL-6 production in HIV-1 infection are not known. This study was designed to explore the relationship between HIV-1 replication and IL-6 induction.

DESIGN

Correlations between plasma levels of IL-6 and HIV-1 RNA were examined in 2 clinical studies. To more directly assess the induction of IL-6 by HIV-1, several cell and tissue types that support HIV-1 replication in vivo were infected with HIV-1, and expression of IL-6 was measured.

METHODS

Spearman rank correlations were used to examine the relationship between plasma levels of IL-6 and HIV-1 RNA. Macrophages and colonic and lymph node histocultures were infected with HIV-1 or stimulated with bacterial products, lipopolysaccharide (LPS) or flagellin, and IL-6 levels in supernatant were measured by enzyme-linked immunosorbent assay or multiplex bead assay.

RESULTS

In the clinical studies, there was weak or no correlation between plasma levels of IL-6 and HIV-1 RNA, but IL-6 levels were correlated with plasma levels of the LPS coreceptor CD14. Macrophages stimulated with LPS or flagellin showed robust production of IL-6, but there was no increase in IL-6 production after HIV-1 infection. IL-6 expression was not increased in lymph node histocultures obtained from HIV-1-infected subjects nor after productive HIV-1 infection of colonic or lymph node histocultures ex vivo.

CONCLUSIONS

We find no evidence that HIV-1 replication is an important driver of IL-6 expression in vivo or in in vitro systems.

TLR4 and TLR5 on corneal macrophages regulate Pseudomonas aeruginosa keratitis by signaling through MyD88-dependent and -independent pathways

Pseudomonas aeruginosa is a major cause of blindness and visual impairment in the United States and worldwide. Using a murine model of keratitis in which abraded corneas are infected with P. aeruginosa parent and ΔfliC (aflagellar) strains 19660 and PAO1, we found that F4/80(+) macrophages were the predominant cell type in the cornea expressing TLR2, TLR4, and TLR5. Depletion of macrophages and dendritic cells using transgenic Mafia mice, in which Fas ligand is selectively activated in these cells, resulted in diminished cytokine production and cellular infiltration to the corneal stroma and unimpaired bacterial growth. TLR4(-/-) mice showed a similar phenotype postinfection with ΔfliC strains, whereas TLR4/5(-/-) mice were susceptible to corneal infection with parent strains. Bone marrow-derived macrophages stimulated with ΔfliC bacteria induced Toll/IL-1R intracellular domain (TIR)-containing adaptor inducing IFN-β (TRIF)-dependent phosphorylation of IFN regulatory factor 3 in addition to TIR-containing adaptor protein/MyD88-dependent phosphorylation of IκB and nuclear translocation of the p65 subunit of NFκB. Furthermore, TRIF(-/-) mice showed a similar phenotype as TLR4(-/-) mice in regulating only ΔfliC bacteria, whereas MyD88(-/-) mice were unable to clear parent or ΔfliC bacteria. Finally, IL-1R1(-/-) and IL-1α/β(-/-) mice were highly susceptible to infection. Taken together, these findings indicate that P. aeruginosa activates TLR4/5 on resident corneal macrophages, which signal through TRIF and TIR-containing adaptor protein/MyD88 pathways, leading to NF-κB translocation to the nucleus, transcription of CXCL1 and other CXC chemokines, recruitment of neutrophils to the corneal stroma, and subsequent bacterial killing and tissue damage. IL-1α and IL-1β are also produced, which activate an IL-1R1/MyD88-positive feedback loop in macrophages and IL-1R on other resident cells in the cornea.

Increased per cell IFN-gamma productivity indicates recent in vivo activation of T cells

Immunization with vaccinia virus causes long-term immunity. Efforts have been made to characterize the T cells responsible for this protection. Recently, T cell subsets were described that not only co-express multiple cytokines, but also show increased per cell cytokine productivity. These highly productive cells are often considered to be the most protective. We used ELISPOT assays to measure per cell IFN-gamma productivity of vaccinia-specific T cells in childhood immunized adults immediately before and at different time points after vaccinia re-vaccination. Apart from an increase in frequency, we found a marked increase of IFN-gamma productivity following vaccinia re-vaccination. However, these changes were short-lived as both parameters quickly returned to baseline values within 22days after re-vaccination. Therefore, increased per cell IFN-gamma productivity seems to be a sign of recent in vivo T cell activation rather than a stable marker of a distinct T cell subset responsible for long-term immune protection.

Granzyme B production distinguishes recently activated CD8(+) memory cells from resting memory cells

For immune diagnostic purposes it would be critical to be able to distinguish between ongoing immune processes, such as active infections, and long-term immune memory, for example imprinted by infections that have been cleared a long time ago or by vaccinations. We tested the hypothesis that the secretion of granzyme B, as detected in ex vivo ELISPOT assays, permits this distinction. We studied EBV-, flu- and CMV-specific CD8(+) cells in healthy individuals, Vaccinia virus-reactive CD8(+) cells in the course of vaccination, and HIV-specific CD8(+) cells in HIV-infected individuals. Antigen-specific ex vivo GzB production was detected only transiently after Vaccinia immunization, and in HIV-infected individuals. Our data suggest that ex vivo ELISPOT measurements of granzyme B permit the identification of actively ongoing CD8(+) cell responses-a notion that is pertinent to the immune diagnostic of infections, transplantation, allergies, autoimmune diseases, tumors and vaccine development.

Neonatal induction of myelin-specific Th1/Th17 immunity does not result in experimental autoimmune encephalomyelitis and can protect against the disease in adulthood

The neonatal immune system is believed to be biased towards T helper type 2 (Th2) immunity, but under certain conditions neonates can also develop Th1 immune responses. Neonatal Th2 immunity to myelin antigens is not pathogenic and can prevent induction of experimental autoimmune encephalomyelitis (EAE) in adulthood, but the consequences of neonatally induced Th1 immunity to self-antigens have remained unresolved. Here, we show that neonatal injection of mice with myelin antigens emulsified in complete Freund's adjuvant (CFA) induced vigorous production of IFN-gamma and IL-17, but not IL-5, consistent with myelin-specific Th1/Th17 immunity. Importantly, the myelin-specific Th1/Th17 cells persisted in the mice until adulthood without causing symptoms of EAE. Intraperitoneal, but not subcutaneous injection of neonates with myelin antigens protected against induction of EAE as adults. Intraperitoneally injected neonates showed a substantial decrease of the number and avidity of myelin-reactive Th17 cells, suggesting a decrease in IL-17 producing precursor cells as the mechanism of protection from EAE upon re-injection with myelin antigens as adults. The results could provide a rationale for the presence of autoreactive T cells found in healthy human individuals without autoimmune disease.

Suramin has adjuvant properties and promotes expansion of antigen-specific Th1 and Th2 cells in vivo

Aluminum hydroxide and incomplete Freund's adjuvant (IFA) are the only adjuvants approved for human use. Both are T helper 2 (Th2) adjuvants, however, T helper 1 (Th1) immunity is induced if microbial products such as mycobacteria, CpG's, or bacterial toxins are included in the adjuvant preparation. The usefulness of bacterial toxins, such as Pertussis toxin (PT) or Cholera toxin (CT), as adjuvants for human vaccination is limited by toxic side effects and high immunogenicity. Hence, we asked whether or not the adjuvant activity of bacterial toxins on Th1 and Th2 immunity could be mimicked by chemical compounds of small molecular weight and less immunogenicity. In the present study, we show that Suramin, a small molecular weight naphthylurea, which mainly acts on G-proteins and on P2X/P2Y receptors, promotes expansion of hen eggwhite lysozyme (HEL)-specific Th1 and Th2 cells upon immunization of BALB/c mice with HEL in aluminum hydroxide (alum). The results indicated that the adjuvant effects of Suramin on T cell responses were mediated by enhancing the expression of MHC class II and costimulatory molecules on antigen presenting cells (APCs), and by increasing their pro-inflammatory cytokine production. Together, the results suggest that small molecular weight compounds such as Suramin could be used as alternative vaccine adjuvants.

Pertussis toxin modulates the immune response to neuroantigens injected in incomplete Freund's adjuvant: induction of Th1 cells and experimental autoimmune encephalomyelitis in the presence of high frequencies of Th2 cells

Pertussis toxin (PT) has been widely used to facilitate the induction of experimental autoimmune encephalomyelitis (EAE) in rodents. It has been suggested that this microbial product promotes EAE by opening up the blood-brain barrier and thereby facilitates the migration of pathogenic T cells to the CNS. However, PT has other biological effects that could contribute to its activity in EAE, such as enhancing the cytokine production by T cells and induction of lymphocytosis. In this work, we investigated the effects of PT on the pathogenicity, cytokine differentiation, and clonal sizes of neuroantigen-reactive T cells in EAE in mice. Our results show that PT prevented the protection from EAE conferred by injection of PLPp139-151 in IFA and induced high frequencies of peptide-specific Th1 cells and disease. Interestingly, the mice developed EAE despite the simultaneous vigorous clonal expansion of PLPp139-151-specific Th2 cells. The data indicate that the Th2 cells in this model neither were protective against EAE nor promoted the disease. Furthermore, the results suggested that the effects of the toxin on neuroantigen-reactive T cells were promoted by the PT-induced activation of APCs in lymphoid tissues and the CNS. Together, the results suggest that microbial products, such as PT, could contribute to the initiation of autoimmune disease by modulating the interaction between the innate and adaptive immune system in the response to self Ags.

Immunological adjuvants efficiently induce antigen-specific T cell responses in old mice: implications for vaccine adjuvant development in aged individuals

The morbidity and mortality of infectious diseases are significantly increased in aged humans. Hence, vaccination has been suggested as a means to reduce or prevent the impact of infections on old individuals. However, it has remained unresolved whether or not standard vaccine adjuvants such as aluminum hydroxide (Alum) are similarly efficacious in old individuals, as compared to young adults. Here, we have investigated the effects of prototypic immunological adjuvants, complete Freund's adjuvant (CFA), incomplete Freund's adjuvant (IFA), or Alum on HEL-specific T cell responses in young adult and old mice. We report that independent of the adjuvant used, the induced T cell responses to the prototypic protein antigen hen eggwhite lysozyme (HEL) were similar in young adult and old mice in terms of cytokine production, T cell frequencies, determinant specificity, and T cell repertoire. The results suggest that vaccine adjuvants developed in young adults should be equally effective in inducing T cell immunity in old individuals.

T cell epitopes of human myelin oligodendrocyte glycoprotein identified in HLA-DR4 (DRB1*0401) transgenic mice are encephalitogenic and are presented by human B cells

Myelin oligodendrocyte glycoprotein (MOG) is an Ag present in the myelin sheath of the CNS thought to be targeted by the autoimmune T cell response in multiple sclerosis (MS). In this study, we have for the first time characterized the T cell epitopes of human MOG restricted by HLA-DR4 (DRB1*0401), an MHC class II allele associated with MS in a subpopulation of patients. Using MHC binding algorithms, we have predicted MOG peptide binding to HLA-DR4 (DRB1*0401) and subsequently defined the in vivo T cell reactivity to overlapping MOG peptides by testing HLA-DR4 (DRB1*0401) transgenic mice immunized with recombinant human (rh)MOG. The data indicated that MOG peptide 97-108 (core 99-107, FFRDHSYQE) was the immunodominant HLA-DR4-restricted T cell epitope in vivo. This peptide has a high in vitro binding affinity for HLA-DR4 (DRB1*0401) and upon immunization induced severe experimental autoimmune encephalomyelitis in the HLA-DR4 transgenic mice. Interestingly, the same peptide was presented by human B cells expressing HLA-DR4 (DRB1*0401), suggesting a role for the identified MOG epitopes in the pathogenesis of human MS.

The enhanced antigen-specific production of cytokines induced by pertussis toxin is due to clonal expansion of T cells and not to altered effector functions of long-term memory cells

Pertussis toxin (PT) has been shown to act as an adjuvant that enhances the production of both Th1 and Th2 cytokines to coinjected protein antigens. It has remained unresolved, however, how PT affects the clonal sizes, long-term effector functions, and Th1/Th2/Th0 differentiation of the T cell responses induced. We have studied the effects of PT on the development of the CD4(+) T cell response to a prototypic antigen, hen eggwhite lysozyme (HEL). HEL injection with incomplete Freund's adjuvant (IFA) resulted in an IFN-gamma(-)/IL-5(+) Th2 recall response. In comparison, co-administration of PT with HEL:IFA enhanced the frequencies of IL-5-producing T cells up to eightfold, and induced the differentiation of high frequencies of IFN-gamma-producing CD4(+) T cells. The results showed that the IFN-gamma and IL-5 produced, originated from clonally expanded Th1 and Th2, but not Th0 cells, and that the effector functions of long-term memory cells were unaffected. Adoptive transfer experiments suggested that PT mediated these effects via activation of APC, not by acting on the T cells directly. The effects of PT on the developing T cell response required the presence of the holotoxin (A- and B-subunit); the individual subunits did not show adjuvant effects. The data suggest that PT enhanced cytokine production by promoting differentiation and vigorous clonal expansion of Th1 and Th2 cells via activation of APC.

Developmentally regulated gene expression of Th2 cytokines in the brain

Given the critical role of cytokines in the regulation of an inflammatory response, we investigated whether certain cytokines are expressed in the brains of normal mice during maturation that could contribute to the immune-privileged nature of the CNS or potentially influence an immune-mediated illness such as experimental allergic encephalomyelitis. The gene expression of IFN gamma (Th1 cytokine) and IL-4 (Th2 cytokine) was analyzed in the brain of several strains of mice. IFN gamma was not detectable. However, IL-4 was present in the brains of neonatal mice, but not adult mice. Resident CNS cells are believed to be the source of the IL-4, because mice deficient in T cells (SCID and RAG2-/-) expressed the IL-4 gene in the CNS. Further analysis indicated that the gene expression of the Th2 cytokine transcription factor, GATA-3, correlated with IL-4 and IL-10 expression in the brain. Since GATA-3-deficient mice have an abnormal CNS, brain-derived Th2 cytokines may play an important role in CNS development, as well as potentially contribute to the immune-privileged nature of the brain.