Concomitant evaluation of PMA+ionomycin-induced kinase phosphorylation and cytokine production in T cell subsets by flow cytometry.

Methods to detect intracellular kinase signaling intermediates by flow cytometry have been recently developed. Termed "phospho-flow," these methods employ fluorescence-conjugated monoclonal antibodies that recognize phosphorylated epitopes of intracellular kinases, and may be combined with surface phenotypic markers to observe changes in kinase pathways by cellular subset. Effector functions, like cytokine production, are processes intrinsically linked to intracellular signaling and kinase activity within each cell. Methodologies that would simultaneously detect changes to signaling pathways as well as effector responses at the single-cell level would allow for mapping of the functional consequences induced by signaling pathway modifications. However, there are challenges to developing such a combined protocol, relating to the different kinetics of rapid signaling events and the more prolonged time required to induce and observe cytokine responses. In this report, we describe the development of an assay that accommodates differences in protocol conditions and response kinetics, merging phospho-flow cytometry, and intracellular cytokine staining methods into a single experimental protocol. We examined intracellular ERK1/2 phosphorylation and IFN-γ production by CD4+ and CD8+ T cells upon polyclonal stimulation with PMA and ionomycin, while monitoring expression of the cytolytic molecule perforin and the T cell activation marker CD38. We present a method that allows observation of kinase phosphorylation and cytokine production within the same cell after stimuli, while maintaining a stable cellular phenotype. Monitoring of signaling and effector functions in distinct immune subsets provides a platform to investigate and relate intracellular kinase signaling activity to immune cell effector function and phenotype in disease states.

Sequential staining improves detection of CCR2 and CX3CR1 on monocytes when simultaneously evaluating CCR5 by multicolor flow cytometry.

Chemokines and their receptors play an essential role within the immune system by dictating cellular migration. In vivo, receptor-ligand interactions rarely occur in isolation as cellular recruitment and migration are complex and highly coordinated processes often involving networks of multiple chemokines and multiple receptors. Simultaneous detection of multiple chemokine receptors on the single cell level is necessary to allow immunophenotyping studies that will help understand the intricacies of these networks. Chemokine receptors undergo a basal level of ongoing internalization, intracellular trafficking, and recycling back to the cell surface, even in the absence of the ligand. In the presence of ligand, receptor-ligand interactions enhance receptor internalization, reducing the cell surface receptor concentration, making precise determination of intrinsic levels challenging. Using multicolor flow cytometry, we sought to evaluate and optimize the simultaneous detection of cell surface expression levels of CCR2, CX3CR1, and CCR5 in primary human monocytes using a single antibody panel. We observed that staining for CCR2 alone or for CX3CR1 alone showed greater expression levels than when the cells were stained with the full panel of antibodies. Fluorescent-minus-one (FMO) controls revealed that ligation of the CCR5 monoclonal antibody to the receptor interfered with detection of CX3CR1 and CCR2. Sequential addition of antibodies during the staining procedure was sufficient to restore the detection levels, suggesting close proximity and possible functional interactions between CCR2/CCR5 and CX3CR1/CCR5 in monocytes. This study highlights the importance of optimizing staining procedures and using proper controls when simultaneously evaluating expression levels of multiple chemokine receptors by flow cytometry. Concurrent assessment of multiple receptors will provide insight and greater understanding of the complex interactions involved in cellular migration.

Comparative immune responses to Mycobacterium tuberculosis in people with latent infection or sterilizing protection.

There is great need for vaccines against tuberculosis (TB) more efficacious than the licensed BCG. Our goal was to identify new vaccine benchmarks by identifying immune responses that distinguish individuals able to eradicate the infection (TB-resisters) from individuals with latent infection (LTBI-participants). TB-resisters had higher frequencies of circulating CD8+ glucose monomycolate (GMM)+ Granzyme-B+ T cells than LTBI-participants and higher proportions of polyfunctional conventional and nonconventional T cells expressing Granzyme-B and/or PD-1 after ex vivo M. tuberculosis stimulation of blood mononuclear cells. LTBI-participants had higher expression of activation markers and cytokines, including IL10, and IFNγ. An exploratory analysis of BCG-recipients with minimal exposure to TB showed absence of CD8+GMM+Granzyme-B+ T cells, lower or equal proportions of Granzyme-B+PD-1+ polyfunctional T cells than TB-resisters and higher or equal than LTBI-participants. In conclusion, high Granzyme-B+PD-1+ T cell responses to M. tuberculosis and, possibly, of CD8+GMM+Granzyme-B+ T cells may be desirable for new TB vaccines.

Impaired functionality of antigen presenting cells in HIV- exposed uninfected infants in the first six months of life.

HIV-exposed uninfected infants (HEU) have increased morbidity and mortality due to infections in the first 6 months of life that tapers down to 2 years of life. The underlying immunologic defects remain undefined. We investigated antigen-presenting cells (APC) by comparing the phenotype of unstimulated APC, responses to toll-like receptor (TLR) stimulation, and ability to activate natural killer (NK) cells in 24 HEU and 64 HIV-unexposed infants (HUU) at 1-2 days of life (birth) and 28 HEU and 45 HUU at 6 months of life. At birth, unstimulated APC showed higher levels of activation and cytokine production in HEU than HUU and stimulation with TLR agonists revealed lower expression of inflammatory cytokines and activation markers, but similar expression of IL10 regulatory cytokine, in APC from HEU compared to HUU. Differences were still present at 6 months of life. From birth to 6 months, APC underwent extensive phenotypic and functional changes in HUU and minimal changes in HEU. TLR stimulation also generated lower NK cell expression of CD69 and/or IFNγ in HEU compared with HUU at birth and 6 months. In vitro experiments showed that NK IFNγ expression depended on APC cytokine secretion in response to TLR stimulation. Ex vivo IL10 supplementation decreased APC-mediated NK cell activation measured by IFNγ expression. We conclude that APC maturation was stunted or delayed in the first 6 months of life in HEU compared with HUU. Deficient inflammatory APC responses and/or the imbalance between inflammatory and regulatory responses in HEU may play an important role in their increased susceptibility to severe infections.

Virus-specific CD8+ T-cell responses better define HIV disease progression than HLA genotype.

HLA alleles B57/58, B27, and B35 have the strongest genetic associations with HIV-1 disease progression. The mechanisms of these relationships may be host control of HIV-1 infection via CD8(+) T-cell responses. We examined these immune responses in subjects from the Seattle Primary Infection Cohort with these alleles. CD8(+) T-cell responses to conserved HIV epitopes within B57/58 alleles (TW10 and KF11) and B27 alleles (KK10 and FY10) delayed declines in CD4(+) T-cell counts (4 to 8 times longer), while responses to variable epitopes presented by B35 alleles (DL9 and IL9) resulted in more rapid progression. The plasma viral load was higher in B57/58(+) and B27(+) subjects lacking the conserved B57/58- and B27-restricted responses. The presence of certain B57/58-, B27-, and B35-restricted HIV-specific CD8(+) T-cell responses after primary HIV-1 infection better defined disease progression than the HLA genotype alone, suggesting that it is the HIV-specific CD8(+) T cells and not the presence of a particular HLA allele that determine disease progression. Further, the most effective host CD8(+) T-cell responses to HIV-1 were prevalent within an HLA allele, represented a high total allele fraction of the host CD8(+) T-cell response, and targeted conserved regions of HIV-1. These data suggest that vaccine immunogens should contain only conserved regions of HIV-1.

Lower influenza-specific cell-mediated immune responses in individuals with atopic dermatitis compared with healthy controls.

In a sub-study of a clinical trial (NCT01737710) investigating the immunogenicity of trivalent inactivated influenza vaccine (IIV3) administered intradermally or intramuscularly to individuals with atopic dermatitis (AD), we assessed T cell and antigen-presenting cell (APC) responses to influenza B in AD and Non-AD controls. The comparison of IFN-γ ELISpot in 58 AD and 31 Non-AD showed lower responses in AD pre-vaccination. Pre-vaccination, AD also had lower Th2 responses and less inflammatory cytokine production by APC measured by flow cytometry and cytokine levels in culture supernatants. AD also had lower Th1 and Th2 responses to nonspecific anti-CD3/anti-CD28-stimulation, but these were not significantly correlated with the influenza-specific responses, suggesting a primary role for the APC in the decreased influenza-specific T cell responses. Multivariate modeling of influenza-specific responses pre-vaccination with influenza-specific antibody titers and IFN-γ ELISpot as outcome measures identified several T cell and APC subsets that negatively or positively predicted protective responses to the vaccine. However, none of the functional differences between AD and Non-AD had high predictive value on adaptive responses to influenza vaccine, which was in agreement with the overall similar responses to the vaccine in the parent clinical trial.

HIV-Exposed Uninfected Infants Have Increased Regulatory T Cells That Correlate With Decreased T Cell Function.

Background: HIV-exposed uninfected infants (HEU) are at higher risk of severe infections, hospitalizations and death compared with HIV-unexposed uninfected infants (HUU), but the immune deficit underlying it is not known. To address this gap, we investigated T cell functionality and its relationship to phenotypic profiles of T cells and antigen presenting cells (APC) in HEU and HUU. Methods: Blood mononuclear cells from 55 HEU and 16 HUU were stimulated with Staphylococcal Enterotoxin B (SEB) or mock for 72 h, and tested by flow cytometry for proliferation and expression of Th1, Th2, and regulatory (Treg) markers. In parallel, cells were phenotypically assessed for differentiation profiles of Treg, conventional T cell (Tconv) and APC in unstimulated cells. Results: HEU had lower CD4+ functional responses to SEB/mock and similar CD8+ responses compared with HUU. In the phenotypic T cell panel, HEU showed higher proportions of CD4+ and CD8+ Treg expressing IL10, FOXP3, and CD25; higher effector Tconv and Treg; and lower naïve and CD4+TGFß+ Treg compared with HUU. In the phenotypic APC panel, HEU showed higher proportions of CD1c+ cDC2, CD123+ pDC, CD16+ inflammatory monocytes and cDC and higher expression of CD103 on CD1c-CD123-CD16-cDC1 compared with HUU. Regression analyses adjusted for HIV exposure and multiple comparisons showed that higher CD8+IL10+ and CD8+FOXP3+ Treg in unstimulated cells were associated with lower CD8+ T cell functional responses to SEB/mock. Functionality was not affected by Tconv differentiation, but higher APC activation in aggregate was associated with higher CD8+IL10+ Treg responses to SEB. Conclusions: T cell functionality was decreased in HEU compared with HUU. High CD8+ Treg proportions were the most important predictors of decreased T cell functionality in HEU and HUU.

Analysis of Murine Hematopoietic Stem Cell Proliferation During Inflammation.

Normally, quiescent hematopoietic stem cells (HSC) rapidly enter the cell cycle following exposure to inflammatory stimuli. The analysis of HSC cell cycle activity in murine bone marrow during inflammation is often complicated by the relative rarity of HSCs and shifts in Sca-1, a key cell surface marker used to identify HSCs. Here, we report a method to analyze HSC proliferation and cell cycle distribution under inflammatory conditions. Our approach uses EdU incorporation and Ki67 staining coupled with DNA content quantification by DAPI. We also incorporate the surface marker ESAM to help minimize the potential for contaminating events that may confound analysis in the HSC compartment.

HIV and Age Do Not Synergistically Affect Age-Related T-Cell Markers.

INTRODUCTION: Despite major progress in controlling HIV disease through antiretroviral therapy, changes in immune phenotype and function persist in individuals with chronic HIV, raising questions about accelerated aging of the immune system. METHODS: We conducted a cross-sectional study (2005-2007) of HIV-infected (n = 111) and uninfected (n = 114) men from the Veterans Aging Cohort Study. All HIV-infected subjects were on antiretroviral therapy with VL <400 copies/mL for at least 3 years. T-cell markers were examined using flow cytometry. We evaluated the impact of HIV serostatus and age on T-cell phenotypes (expressed as percentages of the total CD4 and CD8 T-cell population) using multivariate linear regression, adjusted for smoking, alcohol, and race/ethnicity. We tested for interactions between HIV and age by including interaction terms. RESULTS: Among both HIV-infected and uninfected subjects, increasing age was associated with a decreased proportion of naive CD4 T cells (P = 0.014) and CD8 T cells (P < 0.0001). Both HIV infection and increasing age were associated with higher proportions of effector memory CD4 T cells (P < 0.0001 for HIV; P = 0.04 for age) and CD8 T cells (P = 0.0001 for HIV; P = 0.0004 for age). HIV infection, but not age, was associated with a higher proportion of activated CD8 T cells (P < 0.0001). For all T-cell subsets tested, there were no significant interactions between HIV infection and age. CONCLUSIONS: Age and HIV status independently altered the immune system, but we found no conclusive evidence that HIV infection and advancing age synergistically result in accelerated changes in age-associated T-cell markers among virally suppressed individuals.

Altered Natural Killer Cell Function in HIV-Exposed Uninfected Infants.

OBJECTIVES: HIV-exposed uninfected (HEU) infants have higher rates of severe and fatal infections compared with HIV-unexposed (HUU) infants, likely due to immune perturbations. We hypothesized that alterations in natural killer (NK) cell activity might occur in HEU infants and predispose them to severe infections. DESIGN: Case-control study using cryopreserved peripheral blood mononuclear cells (PBMCs) at birth and 6 months from HEU infants enrolled from 2002 to 2009 and HUU infants enrolled from 2011 to 2013. METHODS: NK cell phenotype and function were assessed by flow cytometry after 20-h incubation with and without K562 cells. RESULTS: The proportion of NK cells among PBMCs was lower at birth in 12 HEU vs. 22 HUU (1.68 vs. 10.30%, p < 0.0001) and at 6 months in 52 HEU vs. 72 HUU (3.09 vs. 4.65%, p = 0.0005). At birth, HEU NK cells demonstrated increased killing of K562 target cells (p < 0.0001) and increased expression of CD107a (21.65 vs. 12.70%, p = 0.047), but these differences resolved by 6 months. Stimulated HEU NK cells produced less interferon (IFN)γ at birth (0.77 vs. 2.64%, p = 0.008) and at 6 months (4.12 vs. 8.39%, p = 0.001), and showed reduced perforin staining at 6 months (66.95 vs. 77.30%, p = 0.0008). Analysis of cell culture supernatants indicated that lower NK cell activity in HEU was associated with reduced interleukin (IL)-12, IL-15, and IL-18. Addition of recombinant human IL-12 to stimulated HEU PBMCs restored IFNγ production to that seen in stimulated HUU cultures. CONCLUSION: NK cell proportion, phenotype, and function are altered in HEU infants. NK cell cytotoxicity and degranulation are increased in HEU at birth, but HEU NK cells have reduced IFNγ and perforin production, suggesting an adequate initial response, but decreased functional reserve. NK cell function improved with addition of exogenous IL-12, implicating impaired production of IL-12 by accessory cells. Alterations in NK cell and accessory cell function may contribute to the increased susceptibility to infection in HEU infants.

Immune Responses to Circulating and Vaccine Viral Strains in HIV-Infected and Uninfected Children and Youth Who Received the 2013/2014 Quadrivalent Live-Attenuated Influenza Vaccine.

The live-attenuated influenza vaccine (LAIV) has generally been more efficacious than the inactivated vaccine in children. However, LAIV is not recommended for HIV-infected children because of insufficient data. We compared cellular, humoral, and mucosal immune responses to the 2013-2014 LAIV quadrivalent (LAIV4) in HIV-infected and uninfected children 2-25 years of age (yoa). We analyzed the responses to the vaccine H1N1 (H1N1-09), to the circulating H1N1 (H1N1-14), which had significant mutations compared to H1N1-09 and to B Yamagata (BY), which had the highest effectiveness in 2013-2014. Forty-six HIV-infected and 56 uninfected participants with prior influenza immunization had blood and nasal swabs collected before and after LAIV4 for IFNγ T and IgG/IgA memory B-cell responses (ELISPOT), plasma antibodies [hemagglutination inhibition (HAI) and microneutralization (MN)], and mucosal IgA (ELISA). The HIV-infected participants had median CD4+ T cells = 645 cells/µL and plasma HIV RNA = 20 copies/mL. Eighty-four percent were on combination anti-retroviral therapy. Regardless of HIV status, significant increases in T-cell responses were observed against BY, but not against H1N1-09. H1N1-09 T-cell immunity was higher than H1N1-14 both before and after vaccination. LAIV4 significantly increased memory IgG B-cell immunity against H1N1-14 and BY in uninfected, but not in HIV-infected participants. Regardless of HIV status, H1N1-09 memory IgG B-cell immunity was higher than H1N1-14 and lower than BY. There were significant HAI titer increases after vaccination in all groups and against all viruses. However, H1N1-14 MN titers were significantly lower than H1N1-09 before and after vaccination overall and in HIV-uninfected vaccinees. Regardless of HIV status, LAIV4 increased nasal IgA concentrations against all viruses. The fold-increase in H1N1-09 IgA was lower than BY. Overall, participants <9 yoa had decreased BY-specific HAI and nasal IgA responses to LAIV4. In conclusion, HIV-infected and uninfected children and youth had comparable responses to LAIV4. H1N1-09 immune responses were lower than BY and higher than H1N1-14, suggesting that both antigenic mismatches between circulating and vaccine H1N1 and lower immunogenicity of the H1N1 vaccine strain may have contributed to the decreased H1N1 effectiveness of 2013-2014 LAIV4.

Characterization of humoral and cell-mediated immune responses directed against hepatitis C virus F protein in subjects co-infected with hepatitis C virus and HIV-1.

BACKGROUND: Hepatitis C virus (HCV) F protein is encoded in an alternate reading frame overlapping the core protein region. Its precise sequence, biological function and mode of expression are currently unclear. This study was conducted to examine the prevalence and characteristics of host humoral and cell-mediated immune responses directed against F protein in patients co-infected with HCV and HIV-1. METHODS: Mutations were introduced to allow the expression of HCV-1a F protein in the absence of core. This recombinant and a truncated form lacking the first 11 amino acid residues shared with core were expressed in Escherichia coli, and their amino acid sequences were verified by mass spectrometry. Vaccinia-F protein recombinants were used to test F protein-specific cytotoxic T lymphocyte (CTL) activity. The binding of F protein-derived peptides to HLA-A*0201 was studied to identify putative CTL epitopes. RESULTS: Sera from 23 of 39 patients infected with various HCV genotypes recognized the truncated form, including 13 of 25 subjects co-infected with HIV-1, indicative of antigenic crossreactivity and consistent with the conservation of F protein coding sequences between HCV genotypes. Crossreactive F protein-specific CTL precursors were detected in nine of 11 HCV-infected subjects, including seven of nine patients co-infected with HCV and HIV-1. Finally, three novel putative HLA-A*0201-restricted CTL epitopes were identified. CONCLUSION: These results indicate that patients co-infected with HCV and HIV-1 can mount immunoglobulin and CTL responses directed against HCV F protein that are fully comparable in scope and magnitude with those observed in individuals infected with HCV alone.

Reduced CD14 expression on classical monocytes and vascular endothelial adhesion markers independently associate with carotid artery intima media thickness in chronically HIV-1 infected adults on virologically suppressive anti-retroviral therapy.

HIV infection causes systemic immune inflammation, and increases the risk for cardiovascular (CVD) disease even among those on virologically suppressive anti-retroviral treatment (ART). We performed a biostatistical analysis and screen of candidate cellular and plasma biomarkers for association with carotid artery intima-media thickness (CIMT), independent of traditional CVD risk factors such as age, gender, systolic blood pressure (SBP), lipid levels, smoking and diabetes. We conducted a multi-stage analysis based on a cross-sectional study of CVD risk in HIV-infected subjects age >45 years on ART for >6 months. The goal of this analysis was to identify candidate cellular and plasma biomarkers of CIMT in HIV-1 infected adults. We further sought to determine if these candidate biomarkers were independent of traditional CVD risk factors previously identified in HIV negative adults. High-resolution B-mode ultrasound images of the right common carotid common artery (CCA) were obtained. Plasma soluble inflammatory mediators, cytokines and chemokines were detected. Monocytes were defined by CD14/CD16 expression, and CD8+ T-cell activation by CD38/HLA-DR expression. Subjects were a median of 49.5 years old, 87% male, had a CIMT of 0.73 mm, FRS of 6%, a median viral load of 48 copies/mL, and CD4+ T cell count of 479 cells/µL. Soluble VCAM-1, and expansion of CD14dimCD16- monocytes each associated with higher CIMT independently of age and SBP. These factors are distinct components of a shared atherogenic process; 1) vascular endothelial molecular expression and 2) vascular monocytes that enter into the vascular endothelium and promote atherosclerotic plaque.

IL-1Β enriched monocytes mount massive IL-6 responses to common inflammatory triggers among chronically HIV-1 infected adults on stable anti-retroviral therapy at risk for cardiovascular disease.

Chronic infection by HIV increases the risk of cardiovascular disease (CVD) despite effective antiretroviral therapy (ART). The mechanisms linking HIV to CVD have yet to be fully elucidated. High plasma levels of the pro-inflammatory cytokine IL-6, which may be triggered by IL-1ß, is a biomarker of CVD risk in HIV-negative adults, and of all-cause mortality in HIV disease. Monocytes play a pivotal role in atherosclerosis, and may be major mediators of HIV-associated inflammation. We therefore hypothesized that monocytes from HIV-infected adults would display high inflammatory responses. Employing a 10-color flow cytometry intracellular cytokine staining assay, we directly assessed cytokine and chemokine responses of monocytes from the cryopreserved peripheral blood of 33 chronically HIV-1 infected subjects. Participants were 45 years or older, on virologically suppressive ART and at risk for CVD. This group was compared to 14 HIV-negative subjects matched for age and gender, with similar CVD risk. We simultaneously detected intracellular expression of IL-1ß, IL-6, IL-8 and TNF in blood monocytes in the basal state and after stimulation by triggers commonly found in the blood of treated, chronically HIV-infected subjects: lipopolysaccharide (LPS) and oxidized low-density lipoprotein (oxLDL). In the absence of stimulation, monocytes from treated HIV-infected subjects displayed a high frequency of cells producing IL-1ß (median 19.5%), compared to low levels in HIV-uninfected persons (0.9% p<0.0001). IL-8, which is induced by IL-1ß, was also highly expressed in the HIV-infected group in the absence of stimulation, 43.7% compared to 1.9% in HIV-uninfected subjects, p<0.0001. Strikingly, high basal expression of IL-1ß by monocytes predicted high IL-6 levels in the plasma, and high monocyte IL-6 responses in HIV-infected subjects. Hyper-inflammatory IL-1ß enriched monocytes may be a major source of IL-6 production and systemic inflammation in HIV-infected adults, and may contribute to the risk for all-cause mortality and cardiovascular disease in treated HIV infection.

Vaccine-induced HIV-specific CD8+ T cells utilize preferential HLA alleles and target-specific regions of HIV-1.

Most T cell-based HIV-1 vaccine candidates induce responses of limited breadth for reasons that are unclear. We evaluated vaccine-induced T-cell responses in individuals receiving an HIV-1 recombinant adenoviral vaccine. Certain HLA alleles (B27, B57, B35, and B14) are preferentially utilized to mount HIV-specific responses, whereas other alleles (A02 and B07) are rarely utilized (P < 0.001). This preference seems due to 4 following factors individually or in combination: higher affinity of specific peptides to specific HLA alleles; higher avidity of T-cell receptor; HLA and peptide interaction; and/or higher surface expression of certain HLA. Thus, HLA immunodominance plays a substantial role in vaccine-induced T-cell responses.

Preservation of T cell proliferation restricted by protective HLA alleles is critical for immune control of HIV-1 infection.

HIV-1-infected persons with HLA-B27 and -B57 alleles commonly remain healthy for decades without antiretroviral therapy. Properties of CD8+ T cells restricted by these alleles considered to confer disease protection in these individuals are elusive but important to understand and potentially elicit by vaccination. To address this, we compared CD8+ T cell function induced by HIV-1 immunogens and natural infection using polychromatic flow cytometry. HIV-1-specific CD8+ T cells from all four uninfected immunized and 21 infected subjects secreted IFN-gamma and TNF-alpha. However, CD8+ T cells induced by vaccination and primary infection, but not chronic infection, proliferated to their cognate epitopes. Notably, B27- and B57-restricted CD8+ T cells from nonprogressors exhibited greater expansion than those restricted by other alleles. Hence, CD8+ T cells restricted by certain protective alleles can resist replicative defects, which permits expansion and antiviral effector activities. Our findings suggest that the capacity to maintain CD8+ T cell proliferation, regardless of MHC-restriction, may serve as an important correlate of disease protection in the event of infection following vaccination.