Altered representation of naive and memory CD8 T cell subsets in HIV-infected children

Biological Aging and Immune Senescence in Children with Perinatally Acquired HIV

Chronic HIV-infected children suffer from premature aging and aging-related diseases. Viral replication induces an ongoing inflammation process, with the release of pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs), the activation of the immune system, and the production of proinflammatory cytokines. Although combined highly active antiretroviral therapy (ART) has significantly modified the natural course of HIV infection, normalization of T and B cell phenotype is not completely achievable; thus, many HIV-infected children display several phenotypical alterations, including higher percentages of activated cells, that favor an accelerated telomere attrition, and higher percentages of exhausted and senescent cells. All these features ultimately lead to the clinical manifestations related to premature aging and comorbidities typically observed in older general population, including non-AIDS-related malignancies. Therefore, even under effective treatment, the premature aging process of HIV-infected children negatively impacts their quality and length of life. This review examines the available data on the impact of HIV and ART on immune and biological senescence of HIV-infected children.

HIV-1 elite controllers present a high frequency of activated regulatory T and Th17 cells

HIV-1 infection is characterized by generalized deregulation of the immune system, resulting in increased chronic immune activation. However, some individuals called HIV controllers (HICs) present spontaneous control of viral replication and have a more preserved immune system. Among HICs, discordant results have been observed regarding immune activation and the frequency of different T cell subsets, including Treg and Th17 cells. We evaluated T cell immune activation, differentiation and regulatory profiles in two groups of HICs—elite controllers (ECs) and viremic controllers (VCs)—and compared them to those of cART-treated individuals (cART) and HIV-1-negative (HIV-neg) individuals. ECs demonstrated similar levels of activated CD4⁺ and CD8⁺ T cells in comparison to HIV-neg, while cART and VCs showed elevated T cell activation. CD4⁺ T cell subset analyses showed differences only for transitional memory T cell frequency between the EC and HIV-neg groups. However, VC individuals showed higher frequencies of terminally differentiated, naïve, and stem cell memory T cells and lower frequencies of transitional memory and central memory T cells compared to the HIV-neg group. Among CD8⁺ T cell subsets, ECs presented higher frequencies of stem cell memory T cells, while VCs presented higher frequencies of terminally differentiated T cells compared to the HIV-neg group. HICs showed lower frequencies of total Treg cells compared to the HIV-neg and cART groups. ECs also presented higher frequencies of activated and a lower frequency of resting Treg cells than the HIV-neg and cART groups. Furthermore, we observed a high frequency of Th17 cells in ECs and high Th17/Treg ratios in both HIC groups. Our data showed that ECs had low levels of activated T cells and a high frequency of activated Treg and Th17 cells, which could restrict chronic immune activation and be indicative of a preserved mucosal response in these individuals.

Immunogenicity and Safety of the Measles Vaccine in HIV-Infected Children: An Updated Systematic Review

Children infected with human immunodeficiency virus (HIV) are at increased risk of measles morbidity and mortality. We searched abstracts from the PubMed, Embase, and Latin American and Caribbean Center on Health Sciences Information databases for articles published from the earliest date available through September 26, 2017. The primary outcome of interest was serological responses to measles vaccine, stratified by HIV infection status. A total of 2,858 potentially eligible articles were identified, and the final review included 12 studies published between 1992 and 2013, 9 of which reported data on vaccine safety. The studies we included represented 3,573 children, of whom at least 335 were infected with HIV, 788 were HIV-exposed but not infected, and 1,478 were unexposed to HIV. Four of the 12 studies found statistically significant reductions in seropositivity among HIV-infected children compared with HIV-uninfected children within 4 months of vaccination (prevalence ratio range, 0.44-0.70), and forest plots provided visual trends of decreasing immunity over time among HIV-infected children in 2 additional studies. No vaccine-related deaths or serious adverse events were reported. This updated review demonstrated limitations of the existing published literature but supported evidence of reduced immunogenicity of measles vaccine among HIV-infected children, supporting the World Health Organization recommendation to revaccinate HIV-infected children against measles following immune reconstitution with combination antiretroviral therapy.

Predominantly Antibody-Deficient Patients With Non-infectious Complications Have Reduced Naive B, Treg, Th17, and Tfh17 Cells

Background: Patients with predominantly antibody deficiency (PAD) suffer from severe and recurrent infections that require lifelong immunoglobulin replacement and prophylactic antibiotic treatment. Disease incidence is estimated to be 1:25,000 worldwide, and up to 68% of patients develop non-infectious complications (NIC) including autoimmunity, which are difficult to treat, causing high morbidity, and early mortality. Currently, the etiology of NIC is unknown, and there are no diagnostic and prognostic markers to identify patients at risk.

Objectives: To identify immune cell markers that associate with NIC in PAD patients.

Methods: We developed a standardized 11-color flow cytometry panel that was utilized for in-depth analysis of B and T cells in 62 adult PAD patients and 59 age-matched controls.

Results: Nine males had mutations in Bruton's tyrosine kinase (BTK) and were defined as having X-linked agammaglobulinemia. The remaining 53 patients were not genetically defined and were clinically diagnosed with agammaglobulinemia (n = 1), common variable immunodeficiency (CVID) (n = 32), hypogammaglobulinemia (n = 13), IgG subclass deficiency (n = 1), and specific polysaccharide antibody deficiency (n = 6). Of the 53, 30 (57%) had one or more NICs, 24 patients had reduced B-cell numbers, and 17 had reduced T-cell numbers. Both PAD–NIC and PAD+NIC groups had significantly reduced Ig class-switched memory B cells and naive CD4 and CD8 T-cell numbers. Naive and IgM memory B cells, Treg, Th17, and Tfh17 cells were specifically reduced in the PAD+NIC group. CD21^lo B cells and Tfh cells were increased in frequencies, but not in absolute numbers in PAD+NIC.

Conclusion: The previously reported increased frequencies of CD21^lo B cells and Tfh cells are the indirect result of reduced naive B-cell and T-cell numbers. Hence, correct interpretation of immunophenotyping of immunodeficiencies is critically dependent on absolute cell counts. Finally, the defects in naive B- and T-cell numbers suggest a mild combined immunodeficiency in PAD patients with NIC. Together with the reductions in Th17, Treg, and Tfh17 numbers, these key differences could be utilized as biomarkers to support definitive diagnosis and to predict for disease progression.

Single-Cell Protein Secretion Detection and Profiling

Secreted proteins play important roles in mediating various biological processes such as cell-cell communication, differentiation, migration, and homeostasis at the population or tissue level. Here, we review bioanalytical technologies and devices for detecting protein secretions from single cells. We begin by discussing conventional approaches followed by detailing the latest advances in microengineered systems for detecting single-cell protein secretions with an emphasis on multiplex measurement. These platforms include droplet microfluidics, micro-/nanowell-based assays, and microchamber-based assays, among which the advantages and limitations are compared. Microscale systems also enable the tracking of protein secretion dynamics in single cells, further empowering the study of the cell-cell communication network. Looking forward, we discuss the remaining challenges and future opportunities that will transform basic research of cellular secretion functions at the systems level and the clinical applications for immune monitoring and cancer treatment.

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.

Effect of IL-7 and IL-15 on T cell phenotype in myelodysplastic syndromes

Aberrant T cell phenotype is one of the characteristics of myelodysplastic syndromes (MDS). In this study, we detected an increased concentration of IL-15 in the plasma of MDS patients (n = 20) compared with that in the plasma of healthy controls (n = 20). In MDS patients, reduced naïve CD4+ and CD8+ T cells [16.11 ± 6.56 vs. 24.11 ± 7.18 for CD4+ T cells (p < 0.001) and 13.15 ± 5.67 vs. 23.51 ± 6.25 for CD8+ T cells (p < 0.001)] were observed. The reduced naïve and increased effector memory T cells were significantly correlated with IL-15 plasma level. Then, the effect of IL-15 and IL-7 was tested in vitro. Peripheral blood mononuclear cells from MDS were treated for 15 days with IL-15. This treatment significantly decreased naïve CD4+ (p < 0.001) and CD8+ (p < 0.001) T cells and correspondingly increased terminal memory CD4+ and CD8+ T cells (p < 0.001). Treatment with IL-7 increased naïve CD4+ (p < 0.05) and CD8+ (p < 0.001) T cells. Our results indicated that exposure to high levels of IL-15 may be involved in the T cell phenotype conversion observed in MDS. IL-7 may be one of the promising therapeutic candidates for recovering the effector immune compartment in MDS patients.

Isolation, Cryopreservation, and Immunophenotyping of Human Peripheral Blood Mononuclear Cells

This unit describes procedures for the isolation, cryopreservation, and thawing of human peripheral blood mononuclear cells (HPBMC) and analysis of cell surface markers (CSM) for immunophenotyping using polychromatic flow cytometry. This methodology can be used to ensure that cell integrity and phenotype stability are not altered through cryopreservation and extended storage. For this analysis, HPBMC were isolated from 7 healthy individuals, and 11-color flow cytometry was performed on freshly isolated samples as well as samples cryopreserved for short- and long-term periods. There is no significant difference in the percentage of cells expressing the CSM CD3, CD4, CD8, CD45RO, CD16, CD19, or CD56 between freshly isolated and cryopreserved HPBMC. Hence, cryopreservation of HPBMC does not influence the phenotype of distinct cellular subsets in isolated mononuclear cells. This protocol for HPBMC isolation, cryopreservation, and thawing of HPBMC is intended for long-term studies of large cohorts requiring sample shipment and subsequent batch analysis. © 2017 by John Wiley & Sons, Inc.

HIV-Specific CD8 T Cells Producing CCL-4 Are Associated With Worse Immune Reconstitution During Chronic Infection

BACKGROUND

Immunological nonresponse represents the Achilles heel in the combination antiretroviral therapy (cART) effectiveness, and increases risk of clinical events and death. CD8 T cells play a crucial role in controlling HIV replication, and polyfunctional HIV-specific CD8 T cells have been associated with nonprogressive HIV infection. However, the possible role of polyfunctional CD8 T cells in predicting posttreatment immune reconstitution has not yet been explored. The aim of this study was to identify functional markers predictive of immunological response to cART in chronic HIV-infected patients.

METHODS

A cohort of chronic HIV-infected individuals naive to cART were enrolled in the ALPHA study. CD4/CD8 T-cell subsets, their differentiation/activation, as well as susceptibility to apoptosis were analyzed before and after 12 months of cART. Moreover, CD8 T cells polyfunctional response after HIV antigenic stimulation was also assessed.

RESULTS

Results showed a significant correlation between worse CD4 T-cell restoration and low frequency of naive CD4 T cells, high frequency of effector memory CD4 T cells, and high susceptibility to apoptosis of CD4 T cells all before cART. Moreover, CD8 functional subsets expressing total C-C motif chemokine ligand 4 (CCL-4) or in combination with CD107a and interferon gamma (IFNγ) were negatively associated with immune reconstitution.

CONCLUSIONS

In conclusion, our study shows that a more differentiated phenotype of CD4 T cells and CCL-4-producing CD8 T cells could represent valuable predictors of worse immune reconstitution. These parameters may be used as tools for identifying patients at risk of immunological failure during cART and eventually represent the basis for innovative therapeutic strategies.

Impact of Vaccination on Distribution of T Cell Subsets in Antiretroviral-Treated HIV-Infected Children

Antiretroviral therapy (ART) is generally prescribed to patients with human immunodeficiency virus (HIV) infection with vaccination introduced to prevent disease complications. However, little is known about the influence of immunization on T cell subsets' distribution during the course of infection. This study aims to identify the impact of viral replication and immunization on naïve, effector, effector memory, and central memory T cell subpopulations in ART-treated HIV-infected children. Fifty patients were recruited and injected intramuscularly with influenza A (H1N1) 2009 vaccine on the day of enrollment (day 0) and day 28. Blood samples were collected for pre- and postvaccination on days 0 and 56 for analyzing T cell phenotypes by flow cytometry. Phenotypes of all T cell subsets remained the same after vaccination, except for a reduction in effector CD8⁺ T cells. Moreover, T cell subsets from patients with controllable viral load showed similar patterns to those with virological failure. Absolute CD4 count was also found to have a positive relationship with naïve CD4⁺ and CD8⁺ T cells. In conclusion, vaccination and viral replication have a little effect on the distribution of T cell subpopulations. The CD4 count can be used for prediction of naïve T cell level in HIV-infected patients responding to ART.

Reconciling Longitudinal Naive T-Cell and TREC Dynamics during HIV-1 Infection

Naive T cells in untreated HIV-1 infected individuals have a reduced T-cell receptor excision circle (TREC) content. Previous mathematical models have suggested that this is due to increased naive T-cell division. It remains unclear, however, how reduced naive TREC contents can be reconciled with a gradual loss of naive T cells in HIV-1 infection. We performed longitudinal analyses in humans before and after HIV-1 seroconversion, and used a mathematical model to investigate which processes could explain the observed changes in naive T-cell numbers and TRECs during untreated HIV-1 disease progression. Both CD4⁺ and CD8⁺ naive T-cell TREC contents declined biphasically, with a rapid loss during the first year and a much slower loss during the chronic phase of infection. While naive CD8⁺ T-cell numbers hardly changed during follow-up, naive CD4⁺ T-cell counts continually declined. We show that a fine balance between increased T-cell division and loss in the peripheral naive T-cell pool can explain the observed short- and long-term changes in TRECs and naive T-cell numbers, especially if T-cell turnover during the acute phase is more increased than during the chronic phase of infection. Loss of thymic output, on the other hand, does not help to explain the biphasic loss of TRECs in HIV infection. The observed longitudinal changes in TRECs and naive T-cell numbers in HIV-infected individuals are most likely explained by a tight balance between increased T-cell division and death, suggesting that these changes are intrinsically linked in HIV infection.

T-cell phenotype and function following a first cART regimen containing either a protease inhibitor or a non-nucleoside reverse transcriptase inhibitor in HIV-infected late presenters: results from a retrospective, ex vivo study

BACKGROUND

We aimed to comparatively assess darunavir/ritonavir (DRV/r) and efavirenz (EFV)-based first-line cART regimens in the reconstitution of T-cell phenotype and function in HIV-infected, late presenter subjects.

METHODS

Retrospective, ex vivo study on stored peripheral blood mononuclear cell samples of cART-naive, HIV-infected individuals with CD4(+) T-cell counts <50>250/µl upon cART initiation with either DRV/r or EFV as third drugs of standard antiretroviral regimens. CD4(+) and CD8(+) T-cell maturation (CCR7/CD45RA) and proliferation (Ki67), CD8(+) T-cell activation (CD38/HLA-DR) as well as HIV- and cytomegalovirus (CMV)-specific responses (CD4/CD8/IL-2/IFN-γ) were studied by flow cytometry at baseline (T0), T3, T6 and T12 months. Soluble inflammatory markers (IL-6 and sCD14) were measured in plasma at T0 and T12. Wilcoxon and Mann-Whitney tests were used for statistics.

RESULTS

A total of 19 patients started DRV/r and 15 EFV. Both regimens accounted for suppression of the HIV RNA load (<40 copies/ml), reconstitution of absolute CD4(+) T-cells and CD4(+)/CD8(+) T-cell ratio. All study participants displayed a significant decrease of activated HLA-DR(+)CD38(+) CD8(+) T-cells at all study time points, yet no differences were found between study groups in T-cell activation and maturation phenotype. From a functional standpoint, only individuals receiving DRV/r displayed transitory recovery of HIV-specific IL-2(+)IFN-γ(-) CD4(+) T-cells (T3: P=0.006) and IL-2(-)IFN-γ(+) CD8(+) T-cells (T3: P=0.032).

CONCLUSIONS

DRV/r- and EFV-based regimens have an equal effect on T-cell phenotype and function in HIV late presenters. A temporary restoration of HIV-specific T-cell immunity early in the course of therapy with DRV/r possibly implies a more effective control over HIV in the first months following a PI/r-based regimen, even at late stage of disease.

Comparison of naïve and central memory derived CD8+ effector cell engraftment fitness and function following adoptive transfer

Human CD8⁺ effector T cells derived from CD45RO⁺CD62L⁺ precursors enriched for central memory (T_CM) precursors retain the capacity to engraft and reconstitute functional memory upon adoptive transfer, whereas effectors derived from CD45RO⁺CD62L^- precursors enriched for effector memory precursors do not. Here we sought to compare the engraftment fitness and function of CD8⁺ effector T cells derived from CD45RA⁺CD62L⁺ precursors enriched for naïve and stem cell memory precursors (T_N/SCM) with that of T_CM. We found that cytotoxic T cells (CTLs) derived from T_CM transcribed higher levels of CD28, FOS, INFγ, Eomesodermin (Eomes), and lower levels of BCL2L11, maintained higher levels of phosphorylated AKT, and displayed enhanced sensitivity to the proliferative and anti-apoptotic effects of γ-chain cytokines compared to CTLs derived from T_N/SCM. Higher frequencies of CTLs derived from T_CM retained CD28 expression and upon activation secreted higher levels of IL-2. In NOD/Scid IL-2RγC^null mice, CD8⁺ T_CM derived CTLs engrafted to higher frequencies in response to human IL-15 and mounted robust proliferative responses to an immunostimulatory vaccine. Similarly, CD8⁺ T_CM derived CD19CAR⁺ CTLs exhibited superior antitumor potency following adoptive transfer compared to their CD8⁺ T_N/SCM derived counterparts. These studies support the use of T_CM enriched cell products for adoptive therapy of cancer.

Impact of elevated maternal HIV viral load at delivery on T-cell populations in HIV exposed uninfected infants in Mozambique

Background

HIV-uninfected infants born to HIV-infected mothers (HIV-exposed uninfected, HEU) have been described to have immune alterations as compared to unexposed infants. This study sought to characterize T-cell populations after birth in HEU infants and unexposed infants living in a semirural area in southern Mozambique.

Methods

Between August 2008 and June 2009 mother-infant pairs were enrolled at the Manhiça District Hospital at delivery into a prospective observational analysis of immunological and health outcomes in HEU infants. Infants were invited to return at one month of age for a clinical examination, HIV DNA-PCR, and immunophenotypic analyses. The primary analysis sought to assess immunological differences between HEU and unexposed groups, whereas the secondary analysis assessed the impact of maternal HIV RNA viral load in the HEU group. Infants who had a positive HIV DNA-PCR test were not included in the analysis.

Results

At one month of age, the 74 HEU and the 56 unexposed infants had similar median levels of naïve, memory and activated CD8 and CD4 T-cells. Infant naïve and activated CD8 T-cells were found to be associated with maternal HIV-RNA load at delivery. HEU infants born to women with HIV-RNA loads above 5 log₁₀ copies/mL had lower median levels of naïve CD8 T-cells (p = 0.04), and higher median levels of memory CD8 T-cells, (p = 0.014).

Conclusions

This study suggests that exposure to elevated maternal HIV-RNA puts the infant at higher risk of having early T-cell abnormalities. Improving prophylaxis of mother to child HIV programs such that more women have undetectable viral load is crucial to decrease vertical transmission of HIV, but may also be important to reduce the consequences of HIV virus exposure in HEU infants.

Clinical, immunological and treatment-related factors associated with normalised CD4+/CD8+ T-cell ratio: effect of naïve and memory T-cell subsets

Background

Although effective antiretroviral therapy(ART) increases CD4+ T-cell count, responses to ART vary considerably and only a minority of patients normalise their CD4+/CD8+ ratio. Although retention of naïve CD4+ T-cells is thought to predict better immune responses, relationships between CD4+ and CD8+ T-cell subsets and CD4+/CD8+ ratio have not been well described.

Methods

A cross-sectional study in a cohort of ambulatory HIV+ patients. We used flow cytometry on fresh blood to determine expanded CD4+ and CD8+ T-cell subsets; CD45RO+CD62L+(central memory), CD45RO+CD62L-(effector memory) and CD45RO-CD62L+(naïve) alongside routine T-cell subsets(absolute, percentage CD4+ and CD8+ counts), HIVRNA and collected demographic and treatment data. Relationship between CD4+/CD8+ T-cell ratio and expanded T-cell subsets was determined using linear regression analysis. Results are median[IQR] and regression coefficients unless stated.

Results

We recruited 190 subjects, age 42(36–48) years, 65% male, 65.3% Caucasian, 91% on ART(52.6% on protease inhibitors), 78.4% with HIVRNA<40cps/ml and median ART duration 6.8(2.6–10.2) years. Nadir and current CD4+ counts were 200(112–309) and 465(335–607) cells/mm³ respectively. Median CD4+/CD8+ ratio was 0.6(0.4–1.0), with 26.3% of subjects achieving CD4+/CD8+ ratio>1. Of the expanded CD4+ T-cell subsets, 27.3(18.0–38.3)% were naïve, 36.8(29.0–40.0)% central memory and 27.4(20.0–38.5)% effector memory. Of the CD8+ T-cells subsets, 16.5(10.2–25.5)% were naïve, 19.9(12.7–26.6)% central memory and 41.0(31.8–52.5)% effector memory. In the multivariable adjusted analysis, total cumulative-ART exposure(+0.15,p = 0.007), higher nadir CD4+ count(+0.011,p<0.001) and higher %CD8+ naive T-cells(+0.0085,p<0.001) were associated with higher CD4+/CD8+ ratio, higher absolute CD8+ T-cell(-0.0044,p<0.001) and higher %CD4+ effector memory T-cells(-0.004,p = 0.0036) were associated with lower CD4+/CD8+ ratio. Those with CD4+/CD8+ ratio>1 had significantly higher median %CD8+ naive T-cells; 25.4(14.0–36.0)% versus 14.4(9.4–21.6)%, p<0.0001, but significantly lower absolute CD8+ count; 464(384.5–567) versus 765(603–1084) cells/mm³, p<0.001.

Conclusions

Study suggests important role for naïve CD8+ T-cell populations in normalisation of the immune response to HIV-infection. How these findings relate to persistent immune activation on ART requires further study.

Composition and function of T cell subpopulations are slow to change despite effective antiretroviral treatment of HIV disease

The ability to reconstitute a normal immune system with antiretroviral therapy in the setting of HIV infection remains uncertain. This study aimed to characterize quantitative and qualitative aspects of various T cell subpopulations that do not improve despite effective ART. CD4∶CD8 ratio was evaluated in HIV-infected subjects with viral loads >10,000 copies/µl (“non-controllers”, n = 42), those with undetectable viral loads on ART (“ART-suppressed”, n = 53), and HIV-uninfected subjects (n = 22). In addition, T cell phenotype and function were examined in 25 non-controllers, 18 ART-suppressed, and 7 HIV-uninfected subjects. CD4∶CD8 ratio in non-controllers, ART-suppressed, and HIV-uninfected subjects was 0.25, 0.48, and 1.95 respectively (P<0.0001 for all comparisons). The increased ratio in ART-suppressed compared to non-controllers was driven by an increase of CD4+ T cells, with no change in the expanded CD8+ T cell population. Expansion of differentiated (CD28−CD27−CD45RA+/−CCR7−) T cell subpopulations persisted despite ART and minimal changes were noted in naïve T cell frequencies over time. Increased number of CD8+CD28− T cells and increased CD8+ CMV-specific T cell responses were associated with a decreased CD4∶CD8 ratio. Measures of T cell function demonstrated persistence of high frequencies of CD8+ T cells producing IFN–γ. Lastly, though all CD8+ subpopulations demonstrated significantly lower Ki67 expression in ART-suppressed subjects, CD4+ T cell subpopulations did not consistently show this decrease, thus demonstrating different proliferative responses in the setting of T cell depletion. In summary, this study demonstrated that CD4∶CD8 ratios remained significantly decreased and naïve T cell numbers were slow to increase despite long-term viral suppression on ART. In addition, there is a evidence of differential regulation of the CD4+ and CD8+ T cell subpopulations, suggesting independent homeostatic regulation of the two compartments.

Altered T-cell subsets in HIV-1 natural viral suppressors (elite controllers) with hepatitis C infection

We have established a cohort of 64 Natural Viral Suppressors (NVS) (similar to Elite Controllers/Elite Suppressors), 30 of which have chronic hepatitis C virus (HCV). We investigated T-cell phenotypic changes in association with HCV infection. NVS without HCV and normal controls had similar T-cell phenotypes. However, NVS with HCV had lower naive cell proportions (CD4 and CD8) compared with NVS without HCV (P = 0.0008 and P = 0.02) or normal controls (P = 0.0163 and P = 0.017). These results and previously reported data suggest that HCV coinfection increases immune activation and T-cell disturbances. Any associated T-cell functional changes or potential clinical consequences need further study.

Disease Progression in HIV-1-Infected Viremic Controllers

BACKGROUND

The mechanism of CD4 T-cell decline in HIV-1 infection is unclear, but the association with plasma viral RNA load suggests viral replication is involved. Indeed, viremic controller patients with low viral RNA loads typically maintain high CD4 T-cell counts. Within a local cohort of 86 viremic controllers, we identify a subgroup (18 "discord controllers") with low CD4 T-cell counts that present clinical uncertainty. The underlying mechanism accounting for CD4 T-cell decline in the face of low or undetectable plasma (RNA) viral load remains unresolved. The objective of this study was to investigate the viral and host immune system dynamics in discord controllers by measuring cellular HIV-1 DNA load, T-cell populations, and T-cell activation markers.

METHODS

We compared discord controllers (viral RNA load <2000 copies/mL, <450 CD4 T-cells/mm) with typical controllers (viral RNA load <2000 copies/mL, >450 CD4 T-cells/mm) and progressors (viral RNA load >10,000 copies/mL, <450 CD4 T-cells/mm). We quantified CD4/CD8 naive/central memory/effector memory subsets (CD45RA/RO ± CD62L), activation levels (CD38HLA-DR), and HIV-1 DNA load.

RESULTS

Discord controllers resembled progressors showing high viral DNA load, depletion of naive CD4 T-cells, and higher activation in all CD4 T-cell subsets, compared with typical controllers. They were similar to typical controllers with lower CD8 T-cell activation compared with progressors.

CONCLUSIONS

Our data are consistent with a relationship between CD4 T-cell activation and disease progression. HIV-1 DNA load may be a better marker of viral replication and disease progression than viral RNA load. Lower level CD8 T-cell activation correlates with low viral RNA load but not with disease progression or viral DNA load.

Detectable viral load aggravates immunosenescence features of CD8 T-cell subsets in vertically HIV-infected children

BACKGROUND

CD8 T cells are crucial in the immune responses against HIV infection, but HIV-infected adults suffer a naive CD8 T-cell depletion and accelerated senescence caused by chronic antigen stimulation. Although HIV-infected children preserve a better immune reconstitution capacity their CD8 responses are defective. We wanted to know, whether HIV vertical transmission produces a premature aging of the CD8 population due to antigen exposition to HIV from birth and persistent chronic activation.

METHODS

We conducted a multicentre cross-sectional study that compared vertically HIV-infected children with detectable (viremic) or undetectable (aviremic) viral load and age-matched healthy children. Using multiparameter flow cytometry, we studied within the CD8 population the frequencies of naive, memory, effector memory (effector memory), and TemRA subsets and measured markers of senescence, activation, and proliferation in these cells.

RESULTS

We found that naive subset in viremic children was markedly decreased and had a replicative senescence phenotype. Furthermore, viremic children showed increased frequencies of memory, TEM and TemRA CD8 T cells, with a more activated and replicative senescence phenotype. We found that HIV-infected children with undetectable viral load have an increased senescence in memory and effector CD8 T cells, but the frequencies and phenotype of the CD8 subsets analyzed are comparable to healthy children.

CONCLUSIONS

[corrected] Our study shows that CD8 T cells of HIV-infected children have a more senescent phenotype when compared with age-matched healthy children. Interestingly enough, our results support the importance of maintaining undetectable viral load in HIV-infected children to avoid the premature ageing and dysfunction of CD8 T cells.

CD4 T-cell regeneration in HIV-1 elite controllers

BACKGROUND

Elite controllers spontaneously control HIV-1 replication, which in many cases is associated with preservation of normal CD4 T-cell counts. However, a subset of elite controllers has progressive CD4 T-cell losses despite undetectable viral loads, for reasons that remain undefined. Here, we assessed mechanisms of CD4 T-cell homeostasis in elite controllers with progressive vs. nonprogressive HIV-1 disease courses.

METHODS

Flow cytometry assays were used to determine the proliferation, activation and apoptosis levels of naive T cells in elite controllers with high or low CD4 T-cell counts and reference cohorts of HIV-1-negative and HAART-treated persons. Thymic output was measured by single-joint T-cell receptor excision circle (sjTREC)/β T-cell receptor excision circle (βTREC) ratios, and the frequency of circulating recent thymic emigrants was flow cytometrically determined by surface expression of protein tyrosine kinase 7.

RESULTS

Proportions of naive T cells in elite controllers were severely reduced and closely resemble those of HIV-1 patients with progressive disease. Despite reductions in naive T cells, most elite controllers were able to maintain normal total CD4 T-cell counts by preservation of uncompromised thymic function in conjunction with extrathymic processes that led to elevated levels of circulating recent thymic emigrants. In contrast, elite controllers with low CD4 T-cell counts had reduced thymic output that mirrored thymic dysfunction during untreated progressive HIV-1 infection.

CONCLUSION

These results indicate that both thymic and extrathymic mechanisms contribute to CD4 T-cell maintenance in elite controllers and support the idea that CD4 T-cell homeostasis and control of viral replication are distinct but frequently coinciding processes.

Lymphoid tissue damage in HIV-1 infection depletes naïve T cells and limits T cell reconstitution after antiretroviral therapy

Highly active antiretroviral therapy (HAART) can suppress HIV-1 replication and normalize the chronic immune activation associated with infection, but restoration of naïve CD4⁺ T cell populations is slow and usually incomplete for reasons that have yet to be determined. We tested the hypothesis that damage to the lymphoid tissue (LT) fibroblastic reticular cell (FRC) network contributes to naïve T cell loss in HIV-1 infection by restricting access to critical factors required for T cell survival. We show that collagen deposition and progressive loss of the FRC network in LTs prior to treatment restrict both access to and a major source of the survival factor interleukin-7 (IL-7). As a consequence, apoptosis within naïve T cell populations increases significantly, resulting in progressive depletion of both naïve CD4⁺ and CD8⁺ T cell populations. We further show that the extent of loss of the FRC network and collagen deposition predict the extent of restoration of the naïve T cell population after 6 month of HAART, and that restoration of FRC networks correlates with the stage of disease at which the therapy is initiated. Because restoration of the FRC network and reconstitution of naïve T cell populations are only optimal when therapy is initiated in the early/acute stage of infection, our findings strongly suggest that HAART should be initiated as soon as possible. Moreover, our findings also point to the potential use of adjunctive anti-fibrotic therapies to avert or moderate the pathological consequences of LT fibrosis, thereby improving immune reconstitution.

The hallmark of HIV-1 infection is depletion of CD4 T cells, whose loss leads to the opportunistic infections and cancers characteristic of AIDS. Highly active antiretroviral therapy (HAART) can control HIV-1 replication, but reconstitution particularly of naïve T cells is often incomplete and slow. We show here that fibrosis damages lymphoid tissues (LT), thereby contributing to depletion and incomplete reconstitution. Prior to treatment, chronic immune activation induces LT fibrosis to disrupt the fibroblastic reticular cell (FRC) network, the major source of the T cell survival factor interleukin 7 (IL-7). Fibrosis in this way interferes with the access of T cells to IL-7 “posted” on the FRC network. Without a source and access to IL-7, naïve cells are depleted prior to initiating HAART because of increased apoptosis, and, even after initiating HAART, the losses continue by this mechanism because of pre-existing LT damage. Thus, LT fibrosis impairs immune reconstitution despite the beneficial effects of HAART in suppressing viral replication. Because less LT damage has accumulated in earlier stages of infection, early initiation of HAART also improves immune reconstitution. This LT damage mechanism also suggests that anti-fibrotic treatment in addition to HAART could further improve immune reconstitution.

The suppression of immune activation during enfuvirtide-based salvage therapy is associated with reduced CCR5 expression and decreased concentrations of circulating interleukin-12 and IP-10 during 48 weeks of longitudinal follow-up

BACKGROUND

It has been suggested that patients who initiate highly active antiretroviral therapy (HAART) late in their course of infection may have suboptimal CD4 T-cell gains, persistent alterations in T-cell subsets and residual inflammation. To address this issue, we carried out a comprehensive 48-week immunological study in HIV-infected patients who had experienced failures of prior therapies, had low CD4 cell counts, and were receiving enfuvirtide-based salvage therapy.

METHODS

Immunological monitoring of peripheral lymphocytes from enfuvirtide-responder patients was performed over a 48-week period. A detailed assessment of immune cell subsets, their activation state [CD38 and human leucocyte antigen (HLA)-DR expression] and homeostasis [activation-induced cell death (AICD) and Ki67 expression], and the expression of co-receptors was performed by flow cytometry. Cytokine and chemokine signatures were assessed using multianalyte profiling technology.

RESULTS

Enfuvirtide-based salvage therapy induced a progressive restoration of naïve and central memory CD4 T cells, associated with a decrease in their activation state, suppression of premature priming for AICD and increased expression of Ki67. In addition, a significant decrease in C-C chemokine receptor 5 (CCR5) expression was detected on CD4 T cells, which was strongly correlated with the suppression of immune activation. Changes in circulating proinflammatory molecules occurred; i.e. there were decreases in the concentrations of interleukin (IL)-12, macrophage inflammatory protein MIP-1α, MIP-1β, monokine induced by IFNγ (MIG) and interferon-γ-inducible protein-10 (IP-10). The decline in circulating IL-12 and IP-10 was correlated with both the reduction in the viral load and CD4 T-cell restoration.

CONCLUSIONS

This study shows that suppression of HIV-1 replication with enfuvirtide-based salvage therapy in patients with low CD4 cell counts may result in an immunological benefit, characterized by the restoration of CD4 T-cell subsets associated with decreased immune activation and suppression of inflammation.

A challenge for the future: aging and HIV infection

Older individuals (≥50 years of age) are increasingly becoming a new at-risk group for HIV-1 infection and, together with those surviving longer due to the introduction of anti-retroviral therapy (ART), it is predicted that more than half of all HIV-1-infected individuals in the United States will be greater than 50 years of age in the year 2015. Older individuals diagnosed with HIV-1 are prone to faster disease progression and reduced T-cell reconstitution despite successful virologic control with anti-retroviral therapy (ART). There is also growing evidence that the T-cell compartment in HIV-1(+) adults displays an aged phenotype, and HIV-1-infected individuals are increasingly diagnosed with clinical conditions more commonly seen in older uninfected persons. As aging in the absence of HIV infection is associated with alterations in T-cell function and immunosenescence, the combined impact of both HIV-1 infection and aging may provide an explanation for poorer clinical outcomes observed in older HIV-1-infected individuals. Thus, the development of novel therapeutics to stimulate immune function and delay immunosenescence is critical and would be beneficial to both the elderly and HIV-1-infected individuals.

Decline of CD4⁺ T-cell count before start of therapy and immunological response to treatment in antiretroviral-naive individuals

OBJECTIVE

Treatment guidelines recommend initiation of therapy for individuals experiencing rapid CD4 cell decline. It is not known, however, whether the rate of CD4 cell decline before combination antiretroviral therapy (cART) is related to immunological response following cART.

METHODS

We estimated precART and postcART CD4 cell slopes by mixed models and categorized patients into two groups according to whether estimated precART slopes were above or below the 75th percentile. We compared immunological responses of the two groups through both mixed models and survival techniques. Models were stratified by CD4 cell at baseline, adjusted for HIV RNA, age, sex, HIV transmission group, year of seroconversion, initiation during primary infection, hepatitis C virus and hepatitis B virus serostatus, and cART class.

RESULTS

Of 2038 eligible patients, 1531 and 507 experienced median (interquartile range) precART CD4 cell slope of −105 (−471 to −61) and −42 (−62 to −80) cells/μl, respectively, over 2 years. After adjusting for potential confounders, individuals with shallower decline experienced a slower rate of CD4 cell recovery following cART initiation of +9.5 [95% confidence interval (CI) +6.6 to +12.2] compared to +13.9 (+13.0 to +14.8) cells/μl per month among those with steeper precART decline (P < 0.001). After stratifying by the baseline CD4 cell count, the adjusted relative hazard of an increase from baseline of more than 50 cells/μl was 0.70 (95% CI 0.62−0.79) for those with a shallower vs. steeper precART decline.

CONCLUSION

Findings highlight the existence of a subgroup of individuals with shallower precART CD4 cell decline who experience poorer CD4 cell increases after cART; new studies in this group may provide information to optimize responses to therapy.

Cumulative mechanisms of lymphoid tissue fibrosis and T cell depletion in HIV-1 and SIV infections

The hallmark of HIV-1 and SIV infections is CD4(+) T cell depletion. Both direct cell killing and indirect mechanisms related to immune activation have been suggested to cause the depletion of T cells. We have now identified a mechanism by which immune activation-induced fibrosis of lymphoid tissues leads to depletion of naive T cells in HIV-1 infected patients and SIV-infected rhesus macaques. The T regulatory cell response to immune activation increased procollagen production and subsequent deposition as fibrils via the TGF-β1 signaling pathway and chitinase 3-like-1 activity in fibroblasts in lymphoid tissues from patients infected with HIV-1. Collagen deposition restricted T cell access to the survival factor IL-7 on the fibroblastic reticular cell (FRC) network, resulting in apoptosis and depletion of T cells, which, in turn, removed a major source of lymphotoxin-β, a survival factor for FRCs during SIV infection in rhesus macaques. The resulting loss of FRCs and the loss of IL-7 produced by FRCs may thus perpetuate a vicious cycle of depletion of T cells and the FRC network. Because this process is cumulative, early treatment and antifibrotic therapies may offer approaches to moderate T cell depletion and improve immune reconstitution during HIV-1 infection.

Characteristics of CD8+ T cell subsets in Chinese patients with chronic HIV infection during initial ART

BACKGROUND

CD8+ T cells may play an important role in protecting against HIV. However, the changes of CD8+ T cell subsets during early period of ART have not been fully studied.

METHODS

Twenty-one asymptomatic treatment-naive HIV-infected patients with CD4 T+ cells less than 350 cells/μl were enrolled in the study. Naïve, central memory(CM), effective memory(EM) and terminally differentiated effector (EMRA) CD8+ cell subsets and their activation and proliferation subsets were evaluated in blood samples collected at base line, and week 2, 4, 8 and 12 of ART.

RESULTS

The total CD8+ T cells declined and the Naïve and CM subsets had a tendency of increase. Activation levels of all CD8+ T cell subsets except EMRA subset decreased after ART. However, proliferation levels of total CD8+ T cells, EMRA, EM and CM subsets increased at the first 4 weeks of ART, then decreased. Proliferation level of the naïve cells decreased after ART.

CONCLUSION

The changes of CD8+ T cell subsets during initial ART are complex. Our results display a complete phenotypical picture of CD8+ cell subsets during initial ART and provide insights for understanding of immune status during ART.

The dual impact of HIV-1 infection and aging on naïve CD4 T-cells: additive and distinct patterns of impairment

HIV-1-infected adults over the age of 50 years progress to AIDS more rapidly than adults in their twenties or thirties. In addition, HIV-1-infected individuals receiving antiretroviral therapy (ART) present with clinical diseases, such as various cancers and liver disease, more commonly seen in older uninfected adults. These observations suggest that HIV-1 infection in older persons can have detrimental immunological effects that are not completely reversed by ART. As naïve T-cells are critically important in responses to neoantigens, we first analyzed two subsets (CD45RA⁺CD31⁺ and CD45RA⁺CD31^-) within the naïve CD4⁺ T-cell compartment in young (20–32 years old) and older (39–58 years old), ART-naïve, HIV-1 seropositive individuals within 1–3 years of infection and in age-matched seronegative controls. HIV-1 infection in the young cohort was associated with lower absolute numbers of, and shorter telomere lengths within, both CD45RA⁺CD31⁺CD4⁺ and CD45RA⁺CD31^-CD4⁺ T-cell subsets in comparison to age-matched seronegative controls, changes that resembled seronegative individuals who were decades older. Longitudinal analysis provided evidence of thymic emigration and reconstitution of CD45RA⁺CD31⁺CD4⁺ T-cells two years post-ART, but minimal reconstitution of the CD45RA⁺CD31^-CD4⁺ subset, which could impair de novo immune responses. For both ART-naïve and ART-treated HIV-1-infected adults, a renewable pool of thymic emigrants is necessary to maintain CD4⁺ T-cell homeostasis. Overall, these results offer a partial explanation both for the faster disease progression of older adults and the observation that viral responders to ART present with clinical diseases associated with older adults.

Label free detection of CD4+ and CD8+ T cells using the optofluidic ring resonator

We have demonstrated label free detection of CD4+ and CD8+ T-Lymphocyte whole cells and CD4+ T-Lymphocyte cell lysis using the optofluidic ring resonator (OFRR) sensor. The OFRR sensing platform incorporates microfluidics and photonics in a setup that utilizes small sample volume and achieves a fast detection time. In this work, white blood cells were isolated from healthy blood and the concentrations were adjusted to match T-Lymphocyte levels of individuals infected with HIV. Detection was accomplished by immobilizing CD4 and CD8 antibodies on the inner surface of the OFRR. Sensing results show excellent detection of CD4+ and CD8+ T-Lymphocyte cells at medically significant concentrations with a detection time of approximately 30 minutes. This work will lead to a rapid and low-cost sensing device that can provide a CD4 and CD8 count as a measure of HIV progression.

Microbial translocation induces persistent macrophage activation unrelated to HIV-1 levels or T-cell activation following therapy

OBJECTIVE

HIV-1 replication and microbial translocation occur concomitant with systemic immune activation. This study delineates mechanisms of immune activation and CD4 T-cell decline in pediatric HIV-1 infection.

DESIGN

Cross-sectional and longitudinal cellular and soluble plasma markers for inflammation were evaluated in 14 healthy and 33 perinatally HIV-1-infected pediatric study volunteers prior to and over 96 weeks of protease-inhibitor-containing combination antiretroviral therapy (ART). All HIV-1-infected patients reconstituted CD4 T cells either with suppression of viremia or rebound of drug-resistant virus.

METHODS

Systemic immune activation was determined by polychromatic flow cytometry of blood lymphocytes and ELISA for plasma soluble CD27, soluble CD14, and tumor necrosis factor. Microbial translocation was evaluated by limulus amebocyte lysate assay to detect bacterial lipopolysaccharide (LPS) and ELISA for antiendotoxin core antigen immunoglobulin M (IgM) antibodies. Immune activation markers were compared with viral load, CD4 cell percentage, and LPS by regression models. Comparisons between healthy and HIV-1-infected or between different viral outcome groups were performed by nonparametric rank sum.

RESULTS

Microbial translocation was detected in healthy infants but resolved with age (P < 0.05). LPS and soluble CD14 levels were elevated in all HIV-1-infected patients (P < 0.05 and P < 0.0001, respectively) and persisted even if CD4 T cells were fully reconstituted, virus optimally suppressed, and lymphocyte activation resolved by ART. Children with CD4 T-cell reconstitution but viral rebound following ART continued to display high levels of soluble CD27.

CONCLUSION

Microbial translocation in pediatric HIV-1 infection is associated with persistent monocyte/macrophage activation independent of viral replication or T-cell activation.

Assessment of CD8(+) T cell differentiation in Trypanosoma cruzi-infected children

We previously reported that the T cell compartment in chronically Trypanosoma cruzi-infected adult subjects display functional and phenotypic signs of immune senescence. This study aimed to investigate the differentiation and the senescent profile of the overall CD8(+) T cell compartment in T. cruzi-infected children at the early stage of the disease. We found a lower percentage of naive (CD27(+)CD28(+)CD45RA(+)) and early antigen-experienced (CD45RA(-)CD27(+)CD28(+)), and higher percentages of late differentiated antigen-experienced (CD45RA(-)CD27(-)CD28(-)) CD8(+) T cells in T. cruzi-infected children as compared with age-matched uninfected controls. The expression of the interleukin (IL)-7R is also decreased on naive and on antigen-experienced total CD8(+) T cells with various degrees of differentiation. Conversely, the expression of HLA-DR, caspase-3, and CD57 did not vary on the total CD8(+) T cell compartment. These findings suggest that the duration of the infection is relevant in the process of immune senescent that this parasite can induce.

Altered naive and memory CD4+ T-cell homeostasis and immunosenescence characterize younger patients with myelodysplastic syndrome

Response to immunosuppressive therapy (IST) in younger patients with myelodysplastic syndrome (MDS) has been linked to a T-cell-dominant autoimmune process that impairs hematopoiesis. Analysis of the age-adjusted CD4:CD8 ratio in 76 MDS patients compared with 54 healthy controls showed that inadequate CD4+, rather than expansion of CD8+ T cells, was associated with a lower ratio in a group that included both lower and higher risk MDS patients defined by the International Prognostic Scoring System. In younger MDS patients, naive and memory phenotypes defined by CD45RA and CD62L display showed depletion of naive CD4+ and CD8+ T cells, suggesting a possible relationship to IST responsiveness. To determine the correlation between T-cell subset distribution, T-cell turnover and autoimmunity, a cohort of 20 patients were studied before and after IST. The CD4:CD8 ratio correlated inversely with the proliferative T-cell index before treatment in IST-responsive patients, suggesting that proliferation may be linked to accelerated CD4+ T-cell turnover and hematopoietic failure. Our data show seminal findings that both CD4+ and CD8+ T-cell subsets are dysregulated in MDS. Association between these T-cell defects and response to IST suggests that aberrant T-cell homeostasis and chronic activation are critical determinants influencing autoimmune hematopoietic suppression in younger patients.

Incomplete reconstitution of T cell subsets on combination antiretroviral therapy in the AIDS Clinical Trials Group protocol 384

BACKGROUND

Initiation of combination antiretroviral therapy (ART) results in higher total CD4 cell counts, a surrogate for immune reconstitution. Whether the baseline CD4 cell count affects reconstitution of immune cell subsets has not been well characterized.

METHODS

Using data from 978 patients (621 with comprehensive immunological assessments) from the AIDS [Acquired Immunodeficiency Syndrome] Clinical Trials Group protocol 384, a randomized trial of initial ART, we compared reconstitution of CD4(+), CD4(+) naive and memory, CD4(+) activation, CD8(+), CD8(+) activation, B, and natural killer cells among patients in different baseline CD4(+) strata. Reference ranges for T cell populations in control patients negative for human immunodeficiency virus (HIV) infection were calculated using data from AIDS Clinical Trials Group protocol A5113.

RESULTS

Patients in the lower baseline CD4(+) strata did not achieve total CD4(+) cell counts similar to those of patients in the higher strata during 144 weeks of ART, although CD4(+) cell count increases were similar. Ratios of CD4(+) naive-memory cell counts and CD4(+):CD8(+) cell counts remained significantly reduced in patients with lower baseline CD4(+) cell counts (

CONCLUSIONS

After nearly 3 years of ART, T cell subsets in patients with baseline CD4(+) cell counts >350 cells/mm(3) achieved or approached the reference range those of control individuals without HIV infection. In contrast, patients who began ART with Collapse

Key Words Collapse

MESH Headings

• Acquired Immunodeficiency Syndrome/drug therapy
• Acquired Immunodeficiency Syndrome/immunology
• Adult
• Antiretroviral Therapy, Highly Active
• B-Lymphocytes/immunology
• CD4 Lymphocyte Count
• CD4-CD8 Ratio
• Female
• Humans
• Killer Cells, Natural/immunology
• Male
• Middle Aged
• T-Lymphocyte Subsets/immunology

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Grants

• AI25879 NIAID NIH HHS
• AI066992 NIAID NIH HHS
• K01 AI062435-02 NIAID NIH HHS
• R01 AI066992 NIAID NIH HHS
• U01 AI038858 NIAID NIH HHS
• AI27659 NIAID NIH HHS
• AI38855 NIAID NIH HHS
• IP30AI060354 NIAID NIH HHS
• U01 AI025879 NIAID NIH HHS
• K01 AI062435 NIAID NIH HHS
• AI27666 NIAID NIH HHS
• AI38858 NIAID NIH HHS
• K01 AI062435-04 NIAID NIH HHS
• U01 AI038855 NIAID NIH HHS
• K01 AI062435-03 NIAID NIH HHS
• K01AI062435 NIAID NIH HHS
• U01 AI027666 NIAID NIH HHS
• K01 AI062435-01A1 NIAID NIH HHS
• U01 AI027659 NIAID NIH HHS
• P30 AI060354 NIAID NIH HHS

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Affiliation(s)

Gregory K Robbins Infectious Diseases Unit, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
John G Spritzler
Ellen S Chan
David M Asmuth
Rajesh T Gandhi
Benigno A Rodriguez
Gail Skowron
Paul R Skolnik
Robert W Shafer
Richard B Pollard

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Significantly skewed memory CD8+ T cell subsets in HIV-1 infected infants during the first year of life

HIV-1 infection causes a severe T cell compromise; however, little is known about changes in naive, memory, effector and senescent T cell subsets during the first year of life. T cell subsets were studied over the first year of life in blood from 3 infant cohorts: untreated HIV-infected, HIV-exposed but uninfected, and HIV-unexposed. In HIV-infected infants, the frequency of CCR7(+)CD45RA(+) naive CD8(+) T cells was significantly decreased, while the frequency of CCR7(-)CD45RA(-) effector memory CD8(+) T cells was increased, compared with the control cohorts. A larger population of CD8(+) T cells in HIV-infected infants displayed a phenotype consistent with senescence. Differences in CD4(+) T cell subset frequencies were less pronounced, and no significant differences were observed between exposed and unexposed HIV-uninfected infants. We concluded that the proportion of naive, memory, effector and senescent CD8(+) T cells during the first year of life is significantly altered by HIV-1 infection.

Stone age diseases and modern AIDS

The great advantage of being a sexually transmitted disease is the ability to survive and specialize solely on a host species that is present in low numbers and widely distributed so that contact between infected and uninfected organisms by chance is rare. Pathogens of a sparse, but widely distributed host species, must either: i) have an alternative host; ii) be able to survive in a dormant state; or iii) be non-destructive to their host. For the pathogens of a diploid there is a particularly effective strategy, that of being sexually transmitted. Then the hosts' themselves transfer the pathogen.

Immunophenotyping of T cell subpopulations in HIV disease

This unit illustrates the challenges associated with measurements of T cell subpopulations, and describes how those challenges can be overcome by using polychromatic (5+ color) approaches to flow cytometry. Such approaches are immensely powerful and directly applicable to studies of T cell biology in HIV disease; however, their development requires careful consideration of the antibodies and fluorochromes employed, as discussed here. Furthermore, factors generally known to influence T cell counts can also govern the success or failure of polychromatic experiments; therefore, these factors are reviewed and provide recommendations for minimizing their influence on polychromatic measurements of T cell subsets.

Antigen activation and impaired Fas-induced death-inducing signaling complex formation in T-large-granular lymphocyte leukemia

Clonal T-cell expansion in patients with T-large-granular lymphocyte (LGL) leukemia occurs by an undefined mechanism that may be related to Fas apoptosis resistance. Here, we demonstrate polarized expansion of CD8(+) terminal-memory differentiation in such patients, as demonstrated by CD45RA expression and absence of CD62L expression, suggesting repeated stimulation by antigen in vivo. Elimination of antigen-stimulated T cells normally occurs through Fas-mediated apoptosis. We show that cells from LGL leukemia patients express increased levels of c-FLIP and display resistance to Fas-mediated apoptosis and abridged recruitment of proteins that comprise the death-inducing signaling complex (DISC), including the Fas-associated protein with death-domain (FADD) and caspase-8. Exposure to interleukin-2 (IL-2) for only 24 hours sensitized leukemic LGL to Fas-mediated apoptosis with enhanced formation of the DISC, and increased caspase-8 and caspase-3 activities. We observed dysregulation of c-FLIP by IL-2 in leukemic LGL, suggesting a role in Fas resistance. Our results demonstrate that expanded T cells in patients with LGL leukemia display both functional and phenotypic characteristics of prior antigen activation in vivo and display reduced capacity for Fas-mediated DISC formation.

Unravelling the complexity of T cell abnormalities in common variable immunodeficiency

We investigated several phenotypic and functional parameters of T cell-mediated immunity in a large series of common variable immunodeficiency (CVID) patients. We demonstrated that the vast majority of CVID patients presented multiple T cell abnormalities intimately related among them, the severity of which was reflected in a parallel loss of CD4+ naive T cells. A strong correlation between the number of CD4+ naive T cells and clinical features was observed, supporting the subgrouping of patients according to their number of naive CD4+ T lymphocytes. A reduced thymic output and disrupted CD4+ and CD8+ TCR repertoires paralleled the contraction of CD4+ naive T cell pools. The evaluation of activation markers and cytokine production indicated a strong T cell activation that was significantly related to the increased levels of T cell turnover and apoptosis. Finally, discrete genetic profiles could be demonstrated in groups of patients showing extremely diverse T cell subset composition and function. Naive CD4+ T cell levels were significantly associated with the switched memory B cell-based classification, although the concordance between the respective subgroups did not exceed 58.8%. In conclusion, our data highlight the key role played by the T cell compartment in the pathogenesis of CVID, pointing to the need to consider this aspect for classification of this disease.

Functional signatures of protective antiviral T-cell immunity in human virus infections

The most common human viruses have different abilities to establish persistent chronic infection. Virus-specific T-cell responses are critical in the control of virus replication and in the prevention of disease in chronic infection. A large number of phenotypic markers and a series of functions have been used to characterize virus-specific CD4+ and CD8+ T-cell responses, and these studies have shown great phenotypic and functional heterogeneity of the T-cell responses against different viruses. The heterogeneity of the T-cell response has been proposed to be specific to each virus. However, over the past 2 years, several studies have provided evidence that the phenotypic and functional heterogeneity of CD4+ and CD8+ T-cell responses is predominantly regulated by the levels of antigen load. The levels of antigen load modulate the phenotypic and functional patterns of the T-cell response within the same virus infection. Furthermore, the functional characterization of virus-specific CD4+ and CD8+ T-cell responses has identified signatures of protective antiviral immunity. Polyfunctional, i.e. interleukin-2 and interferon-gamma (IFN-gamma) secretion and proliferation, and not monofunctional, i.e. IFN-gamma secretion, CD4+ and CD8+ T-cell responses represent correlates of protective antiviral immunity in chronic virus infections.

Interferon-alpha differentially rescues CD4 and CD8 T cells from apoptosis in HIV infection

OBJECTIVE

To examine the effects of interferon-alpha (IFN-alpha) on T cell survival and activation in HIV infection.

DESIGN

The effects of IFN-alpha on spontaneous apoptosis and CD38 expression among T cell subsets were determined in vitro and studied in relation to CD4 cell counts, plasma HIV RNA levels and the age of the subjects.

METHODS

Peripheral blood mononuclear cells from 48 HIV-infected persons and 17 healthy donors were incubated in vitro overnight with or without the addition of IFN-alpha. Percentages of apoptotic cells (positive for annexin V) and CD38 cells were determined among T cell subsets.

RESULTS

IFN-alpha inhibited spontaneous apoptosis of CD4 and CD8 T lymphocytes. This protective activity was impaired in CD4 T cells from HIV-infected persons. The reduced protection of IFN-alpha among CD4 cells from HIV-infected persons was not related to the percentages of activated (CD38 or CD45RO+CD38+) cells. Surprisingly, IFN-alpha induced CD38 expression among CD8 T cells from HIV-infected persons, and the magnitude of this effect was directly related to circulating CD4 T cell count. The CD8 T cell subset that expressed CD38 in response to IFN-alpha was defined as CD28 negative, CD62 ligand (CD62L) intermediate/negative.

CONCLUSIONS

Heightened expression of IFN-alpha in HIV infection may contribute to the phenotypic activation state that characterizes chronic infection while a diminished responsiveness of CD4 T cells to the protective effect of this cytokine may contribute to differential survival of CD4 and CD8 T cells in HIV disease.

Longitudinal assessment of de novo T cell production in relation to HIV-associated T cell homeostasis failure

Loss of circulating CD4+ T cells in HIV-1 disease is balanced by CD8+ lymphocytosis to maintain normal CD3+ T cell counts [blind T cell homeostasis (TCH)]. However, for unknown reasons TCH generally fails 1.5-2.5 years before clinically defined AIDS. We investigated whether TCH failure was associated with changes in thymic production of T cells. Using specimens stored prospectively in the Multicenter AIDS Cohort Study (MACS), we measured expression of signal-joint T cell receptor excision circles (sjTRECs), a marker for thymic T cell production, and the fraction of proliferating naive and memory T cells during a 6-8 year period bracketing TCH failure. Segmented regression modeling assessed (1) rates of change in TREC levels before and after TCH failure, and (2) whether these were affected by cellular proliferation, which may dilute sjTREC levels. TCH failure was associated with a large decline in sjTREC (median 1109-fold, p = 0.028); the rate of this decline was only slightly affected when increased proliferation of naive T cells or other peripheral lymphocytes was taken into account. Preferential loss of naive CD4+ T cells was also noted before TCH failure, as has been seen in other studies. These results suggest that deficits in de novo T cell production, either through the decline of thymic function or the destruction of naive T cells, are likely to play an important role in TCH failure and progression of HIV-1 disease.

Human T cell cytokine responses are dependent on multidrug resistance protein-1

Multidrug resistance protein-1 (MRP1) belongs to subfamily C of the ATP-binding cassette transporters, and exports leukotriene C(4) and organic anions including the fluorescent calcium indicator indo-1. The observation that leukocytes from patients with an autoimmune disease exported indo-1 at a higher rate than controls prompted the hypothesis that MRP1 contributes to the function of activated cells. To test this, we defined the expression of MRP1 on resting and activated human T cells, and determined whether T cell activation is dependent upon MRP1 function. MRP1 is expressed on resting memory but not on naive CD4 and CD8 T cells. After activation through the TCR, cord blood CD4 T cells express high levels of MRP1. Blockade of MRP1 with the specific inhibitor MK-571 abrogated superantigen-induced expression of IFN-gamma, tumor necrosis factor-alpha, IL-10, IL-2, IL-4 and CD69 by T cells without affecting their viability, and was reversible upon removal of MK-571 from the culture media. Electrophoretic mobility shift assays demonstrate that MRP1 blockade with MK-571 induces activation of the transcriptional repressor peroxisome proliferator-activated receptor-gamma in CD4 T cells, thus providing insight into the potential mechanism by which their responses are abrogated.

Correlation of T-lymphocyte subpopulations with immunological markers in HIV-1-infected Indian patients

Progressive HIV disease is characterized by CD4 T cell decline and activation of the immune system. We aimed to study the quantitative alterations in the naive (CD45RA+CD62L+), memory/effector (CD45RO+) and activated (HLA-DR+CD38+) T-lymphocyte subpopulations in antiretroviral treatment naive, HIV-1 infected Indian patients by three-color multi-parametric flow cytometry. The association of different CD4+ and CD8+ T cell subsets with the immunological markers- CD4+ and CD8+ T cell percentages was examined by calculating the partial correlation coefficients. We also observed significant differences in the expression of different CD4+ and CD8+ T-cell subsets among the two groups of patients formed using the median CD4+ T cell percentage value (15%) of the study population. The correlations of different CD4+ and CD8+ T cell subsets reflected the quantitative alterations in the T-lymphocyte subpopulations and activation of the immune system during HIV-infection. The study outcome also emphasizes the significance of the CD38+CD8+ T-lymphocyte subset as a prognostic marker for HIV management and ART monitoring in resource-limited settings of developing countries like India.

Therapeutic role of CD8+ T cells in HIV-1 infection: targets and suppressors of viral replication

CD8+ T cells are pivotal in controlling viral replication in HIV-1-infected subjects. However, in chronic infection, HIV-1-specific CD8+ T cells fail to adequately control infection, presenting incomplete maturation and more severe functional impairment with advanced disease. Accumulating evidence has shown that CD8+ T cells can also be productively infected by HIV-1. Whether HIV-1 infection of CD8+ T lymphocytes impacts on their antiviral activity remains to be determined. This review explores the potential mechanisms of HIV-1 infection of CD8+ T cells, its likely contribution to the immunopathogenesis of HIV-1 infection and potential therapeutic interventions.

Expression of Werner and Bloom syndrome genes is differentially regulated by in vitro HIV-1 infection of peripheral blood mononuclear cells

In HIV infection, continuous immune activation leads to accelerated ageing of the adaptive immune system, similar to that observed in elderly people. We investigated the expression of WRN and BLM (genes involved in disorders characterized by premature ageing, genomic instability and cancer predisposition) in peripheral blood mononuclear cells (PBMC) activated in vitro with phytohaemagglutinin (PHA) and infected with different HIV-1 strains. The steady state levels of mRNA were analysed by reverse transcription-polymerase chain reaction (RT-PCR), and protein expression was assayed using immunocytochemistry and Western blot techniques. In uninfected PBMC, PHA stimulation induced an increase in BLM mRNA and protein expression, while WRN expression remained virtually unchanged. When PBMC were infected in vitro with a lymphotropic HIV-1 strain, the level of BLM mRNA showed a peak at 24 h of infection, followed by a decline to uninfected culture levels. A similar result failed to be seen using an R5-tropic HIV-1 strain. In accordance with mRNA expression, in HIV-infected cultures PBMC were stained more frequently and more intensely by a BLM-specific antibody as compared to uninfected cultures, staining peaking at 24. Conversely, WRN expression was not modulated by HIV-1. The proportion of cells showing BLM up-regulation, established by immunocytochemical staining, was much greater than the proportion of productively infected PBMC, as established by proviral DNA measurement. This result indicates that BLM up-regulation is probably a result of an indirect bystander cell effect. Activation of the BLM gene in infected PBMC suggests that premature ageing could be a further immunopathogenetic mechanism involved in HIV-induced immunodeficiency, and points to a possible new candidate target for innovative therapeutic intervention.

Decreases in percentages of naïve CD4 and CD8 T cells and increases in percentages of memory CD8 T-cell subsets in the peripheral blood lymphocyte populations of A-bomb survivors

Our previous studies have revealed a clear dose-dependent decrease in the percentage of naïve CD4 T cells that are phenotypically CD45RA+ in PBL among A-bomb survivors. However, whether there is a similar radiation effect on CD8 T cells has remained undetermined because of the unreliability of CD45 isoforms as markers of naïve and memory subsets among the CD8 T-cell population. In the present study, we used double labeling with CD45RO and CD62L for reliable identification of naïve and memory cell subsets in both CD4 and CD8 T-cell populations among 533 Hiroshima A-bomb survivors. Statistically significant dose-dependent decreases in the percentages of CD45RO-/CD62L+ naïve cells were found in the CD8 T-cell population as well as in the CD4 T-cell population. Furthermore, the percentages of CD45RO+/CD62L+ and CD45RO+/CD62L- memory T cells were found to increase significantly with increasing radiation dose in the CD8 T-cell population but not in the CD4 T-cell population. These results suggest that the prior A-bomb exposure has induced long-lasting deficits in both naïve CD4 and CD8 T- cell populations along with increased proportions of these particular subsets of the memory CD8 T-cell population.

Cytotoxic Difference of T Cells Expanded with Anti-CD3 Monoclonal Antibody in the Presence and Absence of Anti-CD28 Monoclonal Antibody

Bulk T cells can be expanded by CD3 stimulation alone (CD3-Ts) or by CD3/CD28 dual stimulation (CD3/CD28-Ts) of peripheral blood mononuclear cells (PBMC). However, few reports have described the difference of features between CD3-Ts and CD3/CD28-Ts. PBMC were stimulated with anti-CD3 monoclonal antibody (mAb) alone or co-stimulated with anti-CD3/CD28 mAbs immobilized on plastic plates, in the presence of rhIL-2 for 4 days, subsequently cultured in the presence of rhIL-2 with no antibody then analyzed. The expansion rate was significantly lower for CD3-Ts (965 + 510-fold, n=5) than CD3/CD28-Ts (2263 + 856-fold, n=5) (p<0.05). The CD4/CD8 ratio, the percentage of CD28(+) cell, and the percentage of T cells with no ability to generate intracytoplasmic interleukin-4 (IL-4) or interferon-gamma (IFN-gamma) were all significantly higher, but, phenotypically, memory cells were lower in CD3/CD28-Ts than in CD3-Ts. The levels of activity of both natural killer (NK) and lymphocyte-activated killer (LAK) cells were lower in CD3/CD28-Ts than CD3-Ts. In comparison to CD3-Ts, CD3/CD28-Ts showed impaired migration toward RANTES. In conclusion, T cells expanded with anti-CD3 and anti-CD28 mAbs differ from those expanded with anti-CD3 alone with proliferation, cytotoxicity, chemotaxis, and phenotype. These differences may exert profound influences on the therapeutic potential of output cells.

Flow cytometric analysis of vaccine responses: how many colors are enough?

The past 5 years have seen an explosion in technological advances related to measuring immunogenicity. Specifically, two distinct areas of development have led to considerably more detailed analysis of T cell responses: first, the ability to measure over a dozen distinct antigens expressed by individual cells simultaneously (12-color flow cytometry); and second, a host of assays that rapidly and viably identify antigen-specific T cells. Together, these technologies reveal the complex heterogeneity of an immune response generated during infection or after vaccine challenge. The next 5 years will see the determination of which underlying variables will be most important to quantifying vaccine efficacy. In this manuscript, we discuss these technologies, with a focus on assisting in the design and implementation of immunogenicity trials for future vaccine efforts.