Exploring host-commensal-pathogen dynamics in cell line and organotypic human intestinal epithelial models

Host and microbiome intricately interact in the ecosystem of the human digestive tract, playing a crucial role in our health. These interactions can initiate immune responses in the epithelial cells, which, in turn, activate downstream responses in other immune cells. Here, we used a CaCo-2 and a human intestinal enteroid (HIE) model to explore epithelial responses to both commensal and pathogenic bacteria, individually and combined. CaCo-2 cells were co-cultured with peripheral blood mononuclear cells, revealing downstream activation of immune cells. While both systems showed comparable cytokine profiles, they differed in their responses to the different bacteria, with the organoid system being more representative of responses observed in humans. We provide evidence of the pro-inflammatory responses associated with these bacteria. These models contribute to a deeper understanding of the interactions between the microbiota, intestinal epithelium, and immune cells in the gut, promoting advances in the field of host-microbe interactions.

Pre-vaccination immunotypes reveal weak and robust antibody responders to influenza vaccination

Effective vaccine-induced immune responses are particularly essential in older adults who face an increased risk of immunosenescence. However, the complexity and variability of the human immune system make predicting vaccine responsiveness challenging. To address this knowledge gap, our study aimed to characterize immune profiles that are predictive of vaccine responsiveness using "immunotypes" as an innovative approach. We analyzed an extensive set of innate and adaptive immune cell subsets in the whole blood of 307 individuals (aged 25-92) pre- and post-influenza vaccination which we associated with day 28 hemagglutination inhibition (HI) antibody titers. Building on our previous work that stratified individuals into nine immunotypes based on immune cell subsets, we identified two pre-vaccination immunotypes associated with weak and one showing robust day 28 antibody response. Notably, the weak responders demonstrated HLA-DR+ T-cell signatures, while the robust responders displayed a high naïve-to-memory T-cell ratio and percentage of nonclassical monocytes. These specific signatures deepen our understanding of the relationship between the baseline of the immune system and its functional potential. This approach could enhance our ability to identify individuals at risk of immunosenescence. Our findings highlight the potential of pre-vaccination immunotypes as an innovative tool for informing personalized vaccination strategies and improving health outcomes, particularly for aging populations.

Identification of aging-associated immunotypes and immune stability as indicators of post-vaccination immune activation

Immunosenescence describes immune dysfunction observed in older individuals. To identify individuals at-risk for immune dysfunction, it is crucial to understand the diverse immune phenotypes and their intrinsic functional capabilities. We investigated immune cell subsets and variation in the aging population. We observed that inter-individual immune variation was associated with age and cytomegalovirus seropositivity. Based on the similarities of immune subset composition among individuals, we identified nine immunotypes that displayed different aging-associated immune signatures, which explained inter-individual variation better than age. Additionally, we correlated the immune subset composition of individuals over approximately a year as a measure of stability of immune parameters. Immune stability was significantly lower in immunotypes that contained aging-associated immune subsets and correlated with a circulating CD38 + CD4+ T follicular helper cell increase 7 days after influenza vaccination. In conclusion, immune stability is a feature of immunotypes and could be a potential indicator of post-vaccination cellular kinetics.

Quantification of T-cell dynamics during latent cytomegalovirus infection in humans

Cytomegalovirus (CMV) infection has a major impact on the T-cell pool, which is thought to be associated with ageing of the immune system. The effect on the T-cell pool has been interpreted as an effect of CMV on non-CMV specific T-cells. However, it remains unclear whether the effect of CMV could simply be explained by the presence of large, immunodominant, CMV-specific memory CD8+ T-cell populations. These have been suggested to establish through gradual accumulation of long-lived cells. However, little is known about their maintenance. We investigated the effect of CMV infection on T-cell dynamics in healthy older adults, and aimed to unravel the mechanisms of maintenance of large numbers of CMV-specific CD8+ T-cells. We studied the expression of senescence, proliferation, and apoptosis markers and quantified the in vivo dynamics of CMV-specific and other memory T-cell populations using in vivo deuterium labelling. Increased expression of late-stage differentiation markers by CD8+ T-cells of CMV+ versus CMV- individuals was not solely explained by the presence of large, immunodominant CMV-specific CD8+ T-cell populations. The lifespans of circulating CMV-specific CD8+ T-cells did not differ significantly from those of bulk memory CD8+ T-cells, and the lifespans of bulk memory CD8+ T-cells did not differ significantly between CMV- and CMV+ individuals. Memory CD4+ T-cells of CMV+ individuals showed increased expression of late-stage differentiation markers and decreased Ki-67 expression. Overall, the expression of senescence markers on T-cell populations correlated positively with their expected in vivo lifespan. Together, this work suggests that i) large, immunodominant CMV-specific CD8+ T-cell populations do not explain the phenotypical differences between CMV+ and CMV- individuals, ii) CMV infection hardly affects the dynamics of the T-cell pool, and iii) large numbers of CMV-specific CD8+ T-cells are not due to longer lifespans of these cells.

Predictive factors for vaccine failure to guide vaccination in allogeneic hematopoietic stem cell transplant recipients

Vaccination after hematopoietic stem cell transplantation (HSCT) is essential to protect high-risk patients against potentially lethal infections. Though multiple studies have evaluated vaccine specific responses, no comprehensive analysis of a complete vaccination schedule post-HSCT has been performed and little is known about predictors for vaccine failure. In this context, allogeneic HSCT (alloHSCT) patients were included and vaccinated starting one year post-transplantation. Antibody responses were measured by Multiplex Immuno Assay for pneumococcal (PCV13), meningococcal C, diphtheria, pertussis, tetanus and Haemophilus influenza type b one month after the last vaccination and correlated to clinical and immunological parameters. Vaccine failure was defined as antibody response above vaccine-specific cut-off values for less than four out of six vaccines. Ninety-six patients were included of which 27.1% was found to have vaccine failure. Only 40.6% of all patients responded adequately to all six vaccines. In multivariate analysis, viral reactivation post-HSCT (OR 6.53; P = 0.03), B-cells <135 per mm³ (OR 7.24; P = 0.00) and NK-cells <170 per mm³ (OR 11.06; P = 0.00) were identified as predictors for vaccine failure for vaccination at one year post-alloHSCT. Measurement of antibody responses and an individualized approach for revaccination guided by clinical status and immune reconstitution of B-cells and NK-cells may improve vaccine responses.

Latent CMV Infection Is Associated With Lower Influenza Virus-Specific Memory T-Cell Frequencies, but Not With an Impaired T-Cell Response to Acute Influenza Virus Infection

Latent infection with cytomegalovirus (CMV) is assumed to contribute to the age-associated decline of the immune system. CMV induces large changes in the T-cell pool and may thereby affect other immune responses. CMV is expected to impact especially older adults, who are already at higher risk of severe disease and hospitalization upon infections such as influenza virus (IAV) infection. Here, we investigated the impact of CMV infection on IAV-specific CD8⁺ T-cell frequencies in healthy individuals (n=96) and the response to IAV infection in older adults (n=72). IAV-specific memory T-cell frequencies were lower in healthy CMV⁺ older individuals compared to healthy CMV^- older individuals. Upon acute IAV infection, CMV serostatus or CMV-specific antibody levels were not negatively associated with IAV-specific T-cell frequencies, function, phenotype or T-cell receptor repertoire diversity. This suggests that specific T-cell responses upon acute IAV infection are not negatively affected by CMV. In addition, we found neither an association between CMV infection and inflammatory cytokine levels in serum during acute IAV infection nor between cytokine levels and the height of the IAV-specific T-cell response upon infection. Finally, CMV infection was not associated with increased severity of influenza-related symptoms. In fact, CMV infection was even associated with increased IAV-specific T-cell responses early upon acute IAV infection. In conclusion, although associated with lower frequencies of memory IAV-specific T cells in healthy individuals, CMV infection does not seem to hamper the induction of a proper T-cell response during acute IAV infection in older adults.

Rapid reconstitution of CD4 T cells and NK cells protects against CMV-reactivation after allogeneic stem cell transplantation

BACKGROUND

Epstein-Barr virus and Cytomegalovirus reactivations frequently occur after allogeneic stem cell transplantation (SCT).

METHODS

Here we investigated the role of immune cell reconstitution in the onset and subsequent severity of EBV- and CMV-reactivation. To this end, 116 patients were prospectively sampled for absolute T cell (CD4 and CD8), B-cell (CD19) and NK-cell (CD16 and CD56) numbers weekly post-SCT during the first 3 months and thereafter monthly until 6 months post-SCT. Viral load was monitored in parallel.

RESULTS

In contrast to the general belief, we found that early T-cell reconstitution does not play a role in the onset of viral reactivation. CMV reactivation in the first 7 weeks after SCT however resulted in higher absolute CD8(+) T-cell numbers 6 months post-SCT in patients with high-level reactivation, many of which were CMV-specific. Interestingly, rapid reconstitution of CD4(+) T-cells, as well as NK cells and the presence of donor KIR3DL1, are associated with the absence of CMV-reactivation after SCT, suggestive of a protective role of these cells. In contrast, EBV-reactivations were not affected in any way by the level of immune reconstitution after SCT.

CONCLUSION

In conclusion, these data suggest that CD4(+) T-cells and NK cells, rather than CD8(+) T-cells, are associated with protection against CMV-reactivation.

HCV monoinfection and HIV/HCV coinfection enhance T-cell immune senescence in injecting drug users early during infection

Background

Injecting drug users (IDU) are at premature risk of developing multimorbidity and mortality from causes commonly observed in the elderly. Ageing of the immune system (immune-senescence) can lead to premature morbidity and mortality and can be accelerated by chronic viral infections. Here we investigated the impact of HCV monoinfection and HIV/HCV coinfection on immune parameters in (ex-) IDU. We analyzed telomere length and expression of activation, differentiation and exhaustion markers on T cells at baseline (t = 1) and at follow-up (t = 2) (median interval 16.9 years) in IDU who were: HCV mono-infected (n = 21); HIV/HCV coinfected (n = 23) or multiple exposed but uninfected (MEU) (n = 8).

Results

The median time interval between t = 1 and t = 2 was 16.9 years. Telomere length within CD4⁺ and CD8⁺ T cells decreased significantly over time in all IDU groups (p ≤ 0.012). CD4⁺ T-cell telomere length in HCV mono-infected IDU was significantly reduced compared to healthy donors at t = 1 (p < 0.008). HIV/HCV coinfected IDU had reduced CD4⁺ and CD8⁺ T-cell telomere lengths (p ≤ 0.002) to healthy donors i at t = 1. This was related to persistent levels of immune activation but not due to increased differentiation of T cells over time. Telomere length decrease was observed within all T-cell subsets, but mainly found in immature T cells (CD27⁺CD57⁺) (p ≤ 0.015).

Conclusions

HCV mono-infection and HIV/HCV coinfection enhance T-cell immune-senescence. Our data suggest that this occurred early during infection, which warrants early treatment for both HCV and HIV to reduce immune senescence in later life.

Electronic supplementary material

The online version of this article (doi:10.1186/s12979-016-0065-0) contains supplementary material, which is available to authorized users.

A lower viral set point but little immunological impact after early treatment during primary HIV infection

The Primo-SHM trial, a multicenter randomized trial comparing no treatment with 24 or 60 weeks of combination antiretroviral therapy (cART) during primary human immunodeficiency virus (HIV) infection (PHI), recently demonstrated that temporary early cART lowered the viral set point and deferred the need for re-initiation of cART during chronic HIV infection. This study examined whether the beneficial effect of early treatment was caused by preservation of immunological responses. Twenty-seven treated and 20 untreated PHI individuals participating in the Primo-SHM trial were compared at viral set point, that is, 36 weeks after baseline or after treatment interruption, respectively, for a diverse set of immunological parameters. The results show no differences between treated and untreated individuals at the level of effector T-cell formation or replication capacity of the T-cells; regulation of various T, B, natural killer, or dendritic cells; polyfunctionality of the CD8 T-cells; preservation of CD4 T-cells in the gut associated lymphoid tissue; or immune activation. There were subtle differences in the quality of the cytolytic CD4 T-cell response: 11% (median) of CD4 T-cells of the early treated individuals produced the cytolytic molecule perforin compared to 5% in untreated individuals (p=0.046), and treatment caused a modest increase in CD4 T-cells expressing both perforin and granzyme B (median 9% vs. 4% of CD4 T-cells; p=0.045). Early treatment had a modest positive effect on the quality of the CD4 T-cell response. It remains unclear, however, whether these subtle immunological differences were the cause or a result of the lower viral set point in patients who received early treatment.

Ongoing risk behavior and the presence of HCV-RNA affect the hepatitis C virus (HCV)-Specific CD4(+) T cell response

The largest population of people at risk for HCV-infection is injecting drug users (DU). We hypothesize that recurrent exposure to HCV, by continuing risk behavior, influences the development of an HCV-specific T-cell response. Therefore, we studied the association between repeated exposure to and the height and focus of the HCV-specific T-cell response in HCV antibody-positive injecting DU (n=18) with ongoing risk behavior ('high-risk'), 9 with and 9 without detectable HCV-RNA), and 9 never-injecting DU ('low-risk', HCV-RNA+). Both total HCV-specific T-cell response, as well as the T-cell response against HCV nonstructural proteins, were significantly higher in injecting compared to never-injecting DU. Interestingly, the high-risk HCV-RNA¯ had no measurable CD4(+) T-cell response to Core protein, compared to detectable responses to Core in the HCV-RNA+ group. Thus, both ongoing risk behavior and presence of HCV-RNA affect the HCV-specific T-cell response in both magnitude and specificity, which may have implications for vaccine development.

Increased proportion of perforin-expressing CD8+T-cells indicates control of herpesvirus reactivation in children after stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) is frequently complicated by viral reactivations. Early diagnosis of viral reactivations and preemptive therapy relies on frequent viralload monitoring. An easy marker of effective cytotoxicity in lymphopenia is lacking and therefore we studied perforin-expression in CD8+T-cells in children following HSCT. Prospectively, we weekly monitored viral loads and perforin-expression of CD8+T-cells in whole blood by FACS, until 4months after HSCT in children. 27 patients were included (median age 4,3, range 0.3-20,1years) of whom 19 developed viral reactivations. These patients showed higher percentages of perforin-expressing CD8+T-cells (17,2%, range 0-63%) than those without (6,8%; range 0-16%) (p=0.001). The increased percentage of perforin-expressing CD8+T-cells coincided with a decrease in viral load with a median interval between maximum viral load and maximum level of perforin-expression of 0,4weeks (range 0.1-7.1). We conclude that perforin-expression in CD8+T-cells may be a marker for effective antiviral T-cell reconstitution early after HSCT in children.

Complementary role of HCV and HIV in T-cell activation and exhaustion in HIV/HCV coinfection

Objectives

To investigate whether T-cell activation and exhaustion is linked to HCV- and HIV disease parameters in HIV/HCV infected individuals, we studied T-cell characteristics in HIV/HCV coinfected patients and controls.

Methods

14 HIV/HCV coinfected, 19 HCV monoinfected, 10 HIV monoinfected patients and 15 healthy controls were included in this cross-sectional study. Differences in expression of activation and exhaustion markers (HLA-DR, CD38, PD-1, Tim-3 and Fas) and phenotypic markers on CD4⁺ and CD8⁺ T-cells were analysed by flow cytometry and were related to HCV disease parameters (HCV-viremia, ALT and liver fibrosis).

Results

Frequencies of activated CD4⁺ and CD8⁺ T-cells were higher in HIV/HCV-coinfected compared to healthy controls and HCV or HIV mono-infected individuals. Coinfected patients also showed high expression of the exhaustion marker PD-1 and death receptor Fas. In contrast, the exhaustion marker Tim-3 was only elevated in HIV-monoinfected patients. T-cell activation and exhaustion were correlated with HCV-RNA, suggesting that viral antigen influences T-cell activation and exhaustion. Interestingly, increased percentages of effector CD8⁺ T-cells were found in patients with severe (F3–F4) liver fibrosis compared to those with no to minimal fibrosis (F0–F2).

Conclusions

HIV/HCV coinfected patients display a high level of T-cell activation and exhaustion in the peripheral blood. Our data suggest that T-cell activation and exhaustion are influenced by the level of HCV viremia. Furthermore, high percentages of cytotoxic/effector CD8⁺ T-cells are associated with liver fibrosis in both HCV monoinfected and HIV/HCV coinfected patients.

Low doses of the novel caspase-inhibitor GS-9450 leads to lower caspase-3 and -8 expression on peripheral CD4+ and CD8+ T-cells

Chronic hepatitis C virus (HCV) infection is characterized by increased rates of apoptotic hepatocytes and activated caspases have been shown in HCV-infected patients. GS-9450, a novel caspase-inhibitor has demonstrated hepatoprotective activity in fibrosis/apoptosis animal models. This study evaluated the effects of GS-9450 on peripheral T-cell apoptosis in chronic HCV-infected patients. As sub study of the GS-US-227-0102, a double-blind, placebo-controlled phase 2a trial evaluating the safety and tolerability of GS-9450, apoptosis of peripheral CD4+ and CD8+ T-cells was measured using activated caspase-3, activated caspase-8 and CD95 (Fas). Blood samples were drawn at baseline, day 14 after therapy and at 5 weeks off-treatment follow-up in the first cohort of 10 mg. In contrast to the placebo-treated patients, GS-9450 caused a median of 46% decrease in ALT-values from baseline to day 14 in all treated patients (median of 118-64 U/l) rising again to a median of 140 U/l (19%) at 5 weeks off-treatment follow-up. In GS9450-treated patients, during treatment and follow-up, percentages of activated caspase-3+ and caspase-8 expression tended to decrease, in contrast to placebo-treated patients. Interestingly, compared to healthy controls, higher percentages of caspase-3 and caspase-8 positive CD4+ and CD8+ T-cells were demonstrated in HCV-infected patients at baseline. Decreased ALT-values were observed in all HCV-infected patients during treatment with low dose of the caspase-inhibitor GS-9450 accompanied by a lower expression of caspase-3 and -8 on peripheral T-cells. Furthermore, at baseline percentages of activated caspase-3, activated caspase-8 and CD95+ T-cells were higher in chronic HCV-infected patients compared to healthy controls.

T-cell responses at baseline and during therapy with peginterferon-alpha and ribavirin are not associated with outcome in chronic hepatitis C infected patients

BACKGROUND

Since the association between hepatitis C virus (HCV)-specific T-cell responses both pre-treatment and during interferon-alpha based therapy and viral clearance is unresolved, a combined analysis of distinctive T-cell characteristics (proliferation and interferon-gamma production) is important to clarify this issue.

METHODS

Peripheral blood mononuclear cells (PBMC) collected in 22 chronic HCV infected patients at pre-treatment and at week 4 during pegIFN-alpha/ribavirin therapy, were stimulated with overlapping peptide pools in a [3H]-thymidine assay, an interferon-gamma-ELISA, and a sensitive 12-day T-cell expansion assay.

RESULTS

Compared to the [3H]-thymidine proliferation and interferon-gamma secretion assays, the 12-day T-cell expansion assay was more sensitive in detecting T-cell responses. No significant association was demonstrated between pre-treatment HCV-specific CD4+ or CD8+ T-cell responses and either a sustained virological response (SVR) or a rapid virological response (RVR). However, a skewing of individual responses towards the non-structural antigens was observed. During pegIFN-alpha/ribavirin therapy, HCV-specific CD4+ and CD8+ T-cells declined similarly in both SVR/RVR and non-SVR/non-RVR patients.

CONCLUSION

No correlation was found between the magnitude of pre-treatment HCV-specific T-cell responses and the outcome of pegIFN-alpha/ribavirin therapy in terms of SVR and RVR. Moreover, the magnitude of HCV-specific T-cell responses declined in all patients early during treatment.

Emergence of monoclonal antibody b12-resistant human immunodeficiency virus type 1 variants during natural infection in the absence of humoral or cellular immune pressure

Human immunodeficiency virus type 1 (HIV-1) resistance to broadly neutralizing antibodies such as b12, which targets the highly conserved CD4-binding site, raises a significant hurdle for the development of a neutralizing antibody-based vaccine. Here, 15 individuals were studied of whom seven developed b12-resistant viruses late in infection. The study investigated whether immune pressure may be involved in the selection of these viruses in vivo. Although four out of seven patients showed HIV-1-specific broadly neutralizing activity in serum, none of these patients had CD4-binding site-directed antibodies, indicating that strong humoral immunity is not a prerequisite for the outgrowth of b12-resistant viruses. In virus variants from one patient, who showed extremely weak heterologous and autologous neutralizing activity in serum, mutations were identified in the envelope that coincided with changes in b12 neutralization sensitivity. Lack of cytotoxic T-cell activity against epitopes with and without these mutations excluded a role for host cellular immunity in the selection of b12-resistant mutant viruses in this patient. However, b12 resistance correlated well with increased virus replication kinetics, indicating that selection for enhanced infectivity, possibly driven by the low availability of target cells in the later stages of disease, may coincide with increased resistance to CD4-binding site-directed agents, such as b12. These results showed that b12-resistant HIV-1 variants can emerge during the course of natural infection in the absence of both humoral and cellular immune pressure, suggestive of other mechanisms playing a role in the selective outgrowth of b12-resistant viruses.

Comprehensive longitudinal analysis of hepatitis C virus (HCV)-specific T cell responses during acute HCV infection in the presence of existing HIV-1 infection

The aim of this study was to study the development of HCV-specific T cell immunity during acute HCV infection in the presence of an existing HIV-1 infection in four HIV-1 infected men having sex with men. A comprehensive analysis of HCV-specific T cell responses was performed at two time points during acute HCV infection using a T cell expansion assay with overlapping peptide pools spanning the entire HCV genome Three patients with (near) normal CD4+ T cell counts (range 400-970 x 10(6)/L) either resolved (n=1) or temporary suppressed HCV RNA. In contrast, one patient with low CD4+ T cell counts (330 x 10(6)/L), had sustained high HCV RNA levels. All four patients had low HCV-specific CD8+ T cell responses, and similar magnitudes of CD4+ T cell responses. Interestingly, individuals with resolved infection or temporary suppression of HCV-RNA had HCV-specific CD4+ T cell responses predominantly against nonstructural (NS) proteins. While the individual with high HCV RNA plasma concentrations had CD4+ T cell responses predominantly directed against Core. Our data show that an acute HCV infection in an HIV-1 infected person can be suppressed in the presence of HCV-specific CD4+ T cell response targeting non-structural proteins. However further research is needed in a larger group of patients to evaluate the role of HIV-1 on HCV-specific T cell responses in relation to outcome of acute HCV infection.

Detailed analysis of Epstein-Barr virus-specific CD4+ and CD8+ T cell responses during infectious mononucleosis

We studied simultaneously Epstein-Barr virus (EBV)-specific CD4(+) and CD8(+) T cell responses during and after infectious mononucleosis (IM), using a previously described 12-day stimulation protocol with EBNA1 or BZLF1 peptide pools. Effector function of EBV-specific T cells was determined after restimulation by measuring intracellular interferon-gamma production. During IM, BZLF1-specifc CD4(+) T cell responses were dominant compared with CD8(+) T cell responses. EBNA1-specific CD4(+) and CD8(+) T cell responses were low and remained similar for 6 months. However, 6 months after IM, BZLF1-specific CD4(+) T cell responses had declined, but CD8(+) T cell responses had increased. At diagnosis, EBV-specific CD8(+) T cells as studied by human leucocyte antigen class I tetramer staining comprised a tetramer(bright)CD8(bright) population consisting mainly of CD27(+) memory T cells and a tetramer(dim)CD8(dim) population consisting primarily of CD27(-) effector T cells. The remaining EBV-specific CD8(+) T cell population 6 months after the diagnosis of IM consisted mainly of tetramer(bright)CD8(bright) CD27(+) T cells, suggesting preferential preservation of memory T cells after contraction of the EBV-specific T cell pool.

HCV-specific T-cell responses in injecting drug users: evidence for previous exposure to HCV and a role for CD4+ T cells focussing on nonstructural proteins in viral clearance

In order to understand the parameters associated with resolved hepatitis C virus (HCV)-infection, we analysed the HCV-specific T-cell responses longitudinally in 13 injecting drug-users (IDUs) with a prospectively identified acute HCV infection. Seven IDUs cleared HCV and six IDUs remained chronically infected. T-cell responses were followed in the period needed to resolve and a comparable time span in chronic carriers. Ex vivo T-cell responses were measured using interferon-gamma Elispot assays after stimulation with overlapping peptide pools spanning the complete HCV genome. CD4+ memory-T-cell responses were determined after 12-day stimulation with HCV proteins. The maximum response was compared between individuals. The T-cell responses measured directly ex vivo were weak but significantly higher in resolvers compared to chronic carriers, whereas the CD4+ memory-T-cell response was not different between resolvers and chronic carriers. However, HCV Core protein was targeted more often in chronic carriers compared to individuals resolving HCV infection. CD4+ T-cell responses predominantly targeting nonstructural proteins were associated with resolved HCV infection. Interestingly, observation of memory-T-cell responses present before the documented HCV-seroconversion suggests that reinfections in IDUs occur often. The presence of these responses however, were not predictive for the outcome of infection. However, a transition of the HCV-specific CD4+ memory-T-cell response from targeting Core to targeting nonstructural proteins during onset of infection was associated with a favourable outcome. Therefore, the specificity of the CD4+ memory-T-cell responses measured after 12-day expansion seems most predictive of resolved infection.

Stable pattern of HIV-1 subtype C Gag-specific T-cell responses coincides with slow rate of CD4 T-cell decline in HIV-infected Ethiopians

We studied HIV-1 clade C Gag-specific T-cell responses in five HIV-infected Ethiopians with a relatively slow (< 15 cells/microl per year) and five with a fast (> 45 cells/microl per year) CD4 T-cell decline longitudinally. Six study subjects had T-cell responses directed to one or more HIV-1 Gag peptides. The persistence of strong and broad anti-Gag cytotoxic T-lymphocyte responses was associated with a slow rate of CD4 T-cell decline and with human leukocyte antigen alleles from the B27 supertype.

Reconstitution of EBV Latent but Not Lytic Antigen-Specific CD4+and CD8+T Cells after HIV Treatment with Highly Active Antiretroviral Therapy

The incidence of (EBV-related) malignancies in HIV-infected subjects has declined since the introduction of highly active antiretroviral therapy (HAART). To investigate the effect of HAART on EBV infection, we performed a longitudinal analysis of the T cell response to both a latent and a lytic Ag and EBV viral load in 10 subjects from early in HIV infection up to 5 years after HAART. All individuals responded to HAART by a decline in HIV viral load, a restoration of total CD4+ T cell numbers, and a decline in T cell immune activation. Despite this, EBV load remained unaltered, even after 5 years of therapy, although a decline in both CD4+ and CD8+ T cells specific for the lytic EBV protein BZLF1 suggested a decreased EBV reactivation rate. In contrast, latent EBV Ag EBNA1-specific CD4+ and CD8+ T cell responses were restored after 5 years of treatment to levels comparable to healthy individuals. In two individuals who were treated by HAART late during HIV progression, a lymphoma developed shortly after initiation of HAART, despite restoration of EBV-specific CD4+ and CD8+ T cells. In conclusion, long-term HAART does not alter the EBV DNA load, but does lead to a restoration of EBNA1-specific T cell responses, which might allow better control of EBV-infected cells when applied early enough during HIV infection.

Loss of EBNA1-specific memory CD4+ and CD8+ T cells in HIV-infected patients progressing to AIDS-related non-Hodgkin lymphoma

We previously observed a loss of Epstein-Barr virus (EBV)-specific CD8+ T cells in subjects progressing to EBV-related non-Hodgkin lymphoma (NHL), correlating with loss of CD4+ T cells. The aim of the present study was to determine the role of EBV-specific CD4+ T cells in the development of NHL during chronic HIV infection. To this end, CD4+ and CD8+ memory T cells, capable of both proliferation and subsequent interferon gamma (IFNgamma) production, directed against a latent (Epstein-Barr virus nuclear antigen 1 [EBNA1]) and a lytic (BamH fragment Z left frame 1 [BZLF1]) EBV antigen were studied longitudinally in 9 progressors to NHL, 4 progressors to non-EBV-related AIDS, and 4 slow progressors to AIDS. In all 3 groups we observed a decline of EBV-specific memory CD4+ and CD8+ T-cell responses during HIV infection. However, whereas latent antigen EBNA1-specific CD4+ T cells were lost well before diagnosis in all subjects who developed an AIDS-related NHL (and EBNA1-specific CD8+ T cells were significantly lower compared with the other groups), these cells were better preserved in progressors to non-EBV-related disease and slow progressors. Loss of EBNA1-specific T-cell immunity thus might be important for progression to NHL. Interestingly, BZLF1-specific T cells were not lost in all progressors to NHL, suggesting a different function of these cells in the surveillance of EBV-infected B cells.

Novel method for detection of virus-specific CD4+ T?cells indicates a decreased EBV-specific CD4+ T?cell response in untreated HIV-infected subjects

A lower function of EBV-specific CD8(+) T cells in HIV-infected subjects could be related to a lack of specific CD4(+) T cell help. Therefore, we studied EBV-specific CD4(+) T cells in both healthy donors and untreated or highly active antiretroviral therapy (HAART)-treated HIV-seropositive homosexual men. To this end, PBMC were stimulated with overlapping peptide pools from a latent and a lytic EBV protein, EBV nuclear antigen (EBNA)1 and EBV lytic-switch protein ZEBRA (BZLF1), respectively. EBV-specific CD4(+) T cell frequencies measured directly ex vivo were low. To measure EBV-specific memory CD4(+) T cells, capable of both expansion and IFN-gamma production upon antigenic challenge, we developed a specific and reproducible assay, combining ex vivo expansion of specific T cells with flow cytometric analysis of IFN-gamma production. Untreated HIV-infected individuals had a lower CD4(+) T cell response to both EBNA1 and BZLF1 as compared to healthy EBV carriers and HAART-treated HIV-positive subjects. This suggests loss of EBV-specific CD4(+) T cells due to HIV infection, while HAART might restore this response. In addition, we found an increase in the EBNA1-specific CD8(+) T cell response in HAART-treated subjects. Interestingly, numbers of EBV-specific CD4(+) and CD8(+) T cells were inversely correlated with EBV viral load, suggesting an important role also for EBV-specific CD4(+) T cells in the control of EBV infection.

High responsiveness of HLA-B57-restricted Gag-specific CD8+ T cells in vitro may contribute to the protective effect of HLA-B57 in HIV-infection

HLA-B57 has been shown to be associated with long-term asymptomatic HIV-1 infection. To investigate the biological mechanism by which the HLA-B57 allele could protect from HIV-1 disease, we studied both the number of CD8(+) T cells as well as CD8(+) T cell responsiveness directed to different HIV-1 Gag peptides presented by HLA-A2, -B8 or -B57. T cells specific for the HLA-B57 peptide KAFSPEVIPMF responded more readily and to a higher extend to antigenic stimulation in vitro than T cells specific for the HLA-A2 peptide SLYNTVATL or the HLA-B8 peptide EIYKRWII. This phenomenon was reproducible with T cells from individuals expressing HLA-B57 in combination with one or both of the other alleles and was persistent during long-term follow-up. Lower reactivity of A2- and B8-restricted T cells was not explained by mutations in the B8- or A2-restricted Gag-peptides. Moreover, no correlation between peptide mutation frequency and IFN-gamma production by the corresponding Gag-specific T cells was observed. In conclusion, functional differences were observed between T cells specific for HIV epitopes derived from the same protein presented by different HLA molecules. B57-restricted KAFSPEVIPMF-specific CD8(+) T cells have relatively high responsiveness, which could contribute to the protective effect of HLA-B57 in HIV infection.

Altered EBV Viral Load Setpoint after HIV Seroconversion Is in Accordance with Lack of Predictive Value of EBV Load for the Occurrence of AIDS-Related Non-Hodgkin Lymphoma

In contrast to the situation in the post-transplant setting, in HIV-infected individuals an elevated EBV load is not predictive of EBV-related malignancies. To study whether a high EBV load is already a normal situation early in HIV infection and is not related to a decrease in immune function over time, we investigated EBV load and EBV-specific CD8(+) T cells approximately 1 year before and 1 year after HIV seroconversion. EBV load significantly increased after HIV seroconversion from 205 to 1002 copies/10(6) PBMC (p < 0.001), whereas no further increase in EBV load was observed between 1 and 5 years after HIV seroconversion (median, 1827-2478 copies/10(6) PBMC; p = 0.530). Interestingly, the absolute number of EBV lytic epitope, RAKFKQLL-specific CD8(+) T cells increased over HIV seroconversion (4.78 to 9.54/ micro l; p = 0.011). Furthermore, the fraction of CD27-negative effector, RAK-specific CD8(+) T cells tended to increase (from 12.2 to 17.31% CD27(-); p = 0.051), in accordance with Ag-driven differentiation. In conclusion, both virological and immunological data support the idea that a new EBV viral setpoint is reached early in HIV infection, probably by EBV reactivation, as suggested by the preferential increase in EBV lytic epitope-specific CD8(+) T cells. These data may thus help to explain the lack of predictive value of EBV load for the occurrence of AIDS-related lymphoma.

Functional restoration of human immunodeficiency virus and Epstein-Barr virus-specific CD8(+) T cells during highly active antiretroviral therapy is associated with an increase in CD4(+) T cells

To investigate the effect of highly active antiretroviral therapy (HAART) on HIV- and Epstein-Barr virus (EBV)-specific CD8(+) T cells, total number and function of these cells was determined in 16 HIV-infected individuals using tetrameric HLA-peptide complexes and IFN-gamma ELISPOT assays after peptide stimulation, respectively. HAART induced a significant decrease in HIV-specific tetramer(+) T cells, whereas EBV-specific tetramer(+) T cells did not change. In addition, individuals who temporarily failed on therapy showed a temporary increase in the number of HIV-specific T cells, suggesting that differences in the pool size of antigen-specific T cells was determined by the presence of antigen. Interestingly, there was an increase in the ratio of IFN-gamma-producing T cells per total number of both HIV- and EBV-specific T cells in the majority of individuals, suggesting that the function of virus-specific T cells is improved in individuals successfully treated with HAART. Despite this relative functional improvement of EBV-specific T cells, no significant changes were observed in EBV load. In four subjects who temporarily failed on HAART, the percentage of IFN-gamma-producing T cells, both for HIV and EBV, paralleled CD4(+) T cell kinetics, suggesting that function seems to be related to differences in CD4(+) T cell numbers. Overall, these data indicate that HAART improves the antigen responsiveness of both HIV- and EBV-specific T cells, which is associated with an increase in CD4(+) T cells.