Discordant cellular and humoral immune responses to cytomegalovirus infection in healthy blood donors: existence of a Th1-type dominant response

Memory SARS-CoV-2 T-cell response in convalescent COVID-19 patients with undetectable specific IgG antibodies: a comparative study

Background

During the COVID-19 pandemic, a variable percentage of patients with SARS-CoV-2 infection failed to elicit humoral response. This study investigates whether patients with undetectable SARS-CoV-2 IgG are able to generate SARS-CoV-2 memory T cells with proliferative capacity upon stimulation.

Methods

This cross-sectional study was conducted with convalescent COVID-19 patients, diagnosed with a positive real-time PCR (RT-PCR) from nasal and pharyngeal swab specimens. COVID-19 patients were enrolled ≥3 months after the last PCR positive. Proliferative T-cell response after whole blood stimulation was assessed using the FASCIA assay.

Results

A total of 119 participants (86 PCR-confirmed COVID-19 patients and 33 healthy controls) were randomly filtered from an initial cohort. Of these 86 patients, 59 had detectable (seropositive) and 27 had undetectable (seronegative) SARS-CoV-2 IgG. Seropositive patients were subclassified as asymptomatic/mild or severe according to the oxygen supplementation requirement. SARS-CoV-2 CD3+ and CD4+ T cells showed significantly lower proliferative response in seronegative than in seropositive patients. The ROC curve analysis indicated that ≥ 5 CD4+ blasts/μL of blood defined a "positive SARS-CoV-2 T cell response". According to this cut-off, 93.2% of seropositive patients had a positive T-cell response compared to 50% of seronegative patients and 20% of negative controls (chi-square; p < 0.001).

Conclusions

This proliferative assay is useful not only to discriminate convalescent patients from negative controls, but also to distinguish seropositive patients from those with undetectable SARS-CoV-2 IgG antibodies. Memory T cells in seronegative patients are able to respond to SARSCoV-2 peptides, although at a lower magnitude than seropositive patients.

Lack of cytomegalovirus (CMV)-specific cell-mediated immune response using QuantiFERON-CMV assay in CMV-seropositive healthy volunteers: fact not artifact

The QuantiFERON-CMV (QF) assay measures cell-mediated immunity against cytomegalovirus (CMV-CMI), which is particularly useful in individuals susceptible to CMV infection such as transplant patients. A positive QF result identifies patients that are better protected against CMV infection. However, the significance of a negative QF result in CMV-seropositive individuals needs to be clarified. CMV-CMI was analyzed in healthy subjects using the QF assay, and, in parallel, the Flow-cytometric Assay of Specific Cell-mediated Immune response in Activated whole blood (FASCIA). FASCIA assay measures T-cell proliferation using CMV lysate as stimulus whereas QF assay use a mix of peptides. A total of 93 healthy volunteers were enrolled, and 13/71 CMV-seropositive individuals (18.3%) showed humoral/cellular discordance using QF assay (CMV+ QF-). Interestingly, with FASCIA assay CD4+ and CD8+ T-cell proliferations were lower in CMV+ QF- than in CMV+ QF+ individuals. Furthermore, CMV+ QF- volunteers had a lower level of anti-CMV IgG than CMV+ QF+ subjects. Discordant CMV+ QF- volunteers can be defined as low responder individuals since they show lower CMV-specific humoral and cellular immune responses in comparison to CMV+ QF+ individuals. Immune discordance shows the high heterogeneity of immunity to CMV in healthy subjects.

Schistosoma mansoni soluble egg antigen (SEA) and recombinant Omega-1 modulate induced CD4+ T-lymphocyte responses and HIV-1 infection in vitro

Parasitic helminths evade, skew and dampen human immune responses through numerous mechanisms. Such effects will likely have consequences for HIV-1 transmission and disease progression. Here we analyzed the effects that soluble egg antigen (SEA) from Schistosoma mansoni had on modulating HIV-1 infection and cytokine/chemokine production in vitro. We determined that SEA, specifically through kappa-5, can potently bind to DC-SIGN and thereby blocks DC-SIGN mediated HIV-1 trans-infection (p<0.05) whilst not interfering with cis-infection. DCs exposed to SEA whilst maturing under Th2 promoting conditions, will upon co-culture with naïve T-cells induce a T-cell population that was less susceptible to HIV-1 R5 infection (p<0.05) compared to DCs unexposed to SEA, whereas HIV-1 X4 virus infection was unaffected. This was not observed for DCs exposed to SEA while maturing under Th1 or Th1/Th2 (T_mix) promoting conditions. All T-cell populations induced by SEA exposed DCs demonstrate a reduced capacity to produce IFN-γ and MIP-1β. The infection profile of T-cells infected with HIV-1 R5 was not associated with down-modulation of CCR5 cell surface expression. We further show that DCs maturing under T_mix conditions exposed to plant recombinant omega-1 protein (rω-1), which demonstrates similar functions to natural ω-1, induced T-cell populations that were less sensitive for HIV-1 R5 infection (p<0.05), but not for X4 virus infection. This inhibition associated again with a reduction in IFN-γ and MIP-1β expression, but additionally correlated with reduced CCR5 expression. We have shown that SEA parasite antigens and more specifically rω-1 can modulate HIV-1 infectivity with the potential to influence disease course in co-infected individuals.

Parasitic helminths have developed a number of strategies to evade, skew and dampen human immune responses. Such effects will likely have consequences for HIV-1 transmission and disease progression. Here we analyzed the effect that soluble egg antigen (SEA) from Schistosoma mansoni had on HIV-1 infection in vitro. We determined that SEA, through kappa-5, can potently block DC-SIGN mediated HIV-1 trans-infection of CD4⁺ T-lymphocytes, but not block cis-infection. Dendritic cells (DC) exposed to SEA during maturation under Th2 skewing conditions, induce T-cell populations that are less susceptible to HIV-1 R5 infection compared to cells induced by unexposed DCs. HIV-1 X4 infection was unaffected. This restricted infection profile was not associated with down-modulation of CCR5 surface expression or observed differences in cytokine/chemokine production. Using recombinant omega-1, an abundant component of SEA, HIV-1 R5 infection was similarly inhibited with no effect on HIV-1 X4 infection levels. Hence SEA possesses antigens, namely omega-1, that can modulate HIV-1 infection and potentially influence disease course in co-infected individuals.

Epstein-Barr virus- and cytomegalovirus-specific immune response in patients with brain cancer

Background

Patients with brain tumor or pancreatic cancer exhibit the poorest prognosis, while immune fitness and cellular immune exhaustion impacts their survival immensely. This work identifies differences in the immune reactivity to the common human pathogens cytomegalovirus (CMV) and Epstein–Barr virus (EBV) between patients with brain tumor in comparison to those with pancreatic cancer and healthy individuals.

Methods

We characterized the humoral and cellular immune responses of patients with brain tumor or pancreatic cancer to cytomegalovirus structural protein pp65 (CMV-pp65) as well as Epstein–Barr nuclear antigen-1 (EBNA-1) by whole-blood assay and ELISA.

Results

Anti-CMV-pp65 plasma immunoglobulin gamma (IgG) titers were significantly lower in patients with brain tumor compared to healthy donors and patients with pancreatic cancer. Among the responding patients with GBM, those with a weak anti-CMV IgG response also had a decreased median overall survival (p = 0.017, 667 vs 419 days) while patients with brain tumor showed a generally suppressed anti-CMV immune-reactivity. Patients with brain tumor exhibited a significantly lower interferon gamma (IFNγ) response to EBNA-1 and CMV-pp65 compared to patients with pancreatic cancer or healthy donors. This antigen-specific response was further amplified in patients with brain tumor upon conditioning of whole blood with IL-2/IL-15/IL-21. Exclusively in this setting, among the responding patients with GBM, those exhibiting a EBV-specific cellular immune response above the median also displayed an increased median overall survival pattern compared to weak responders (753 vs 370 days, p < 0.001).

Conclusions

This report provides (i) a fast and easy assay using common viral antigens and cytokine stimulation to screen for immune fitness/exhaustion of patients with brain tumor in comparison to pancreatic cancer and healthy individuals and (ii) EBV/CMV-induced IFNγ production as a potential marker of survival in patients with brain tumor.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1557-9) contains supplementary material, which is available to authorized users.

Detecting all Immunoglobulin Classes and Subclasses in a Multiplex 7 Color ImmunoSpot® Assay

Antibody molecules in peripheral blood have a relatively short half-life of roughly 20 days, and therefore their persistence in the serum depends on continuous replenishment by plasma cells. Serum antibody titers are thus indirect and unreliable indicators of immunological memory. In contrast, memory B cells persist in peripheral blood for decades, and enumerating these cells provides direct evidence of having developed an immune response to a given antigen. ELISPOT is an ideal research tool for enumerating antigen-specific memory B cells. Traditionally, B cell ELISPOT assays have been performed for detecting a single class of immunoglobulin (Ig), using a single colorimetric substrate. For comprehensive monitoring of B cell memory, however, all immunoglobulin classes and subclasses need to be assessed. Thus, seven single color assays would need to be performed to measure the numbers of antigen-specific B cells producing IgM, IgA, IgE, IgG₁, IgG₂, IgG₃, and IgG₄. We report here the development of a multiplex seven color B cell ImmunoSpot^® assay in which the number of antigen-specific B cells can be established simultaneously for all major antibody classes and subclasses, requiring the PBMC, antigen, and labor corresponding to a single color assay.

B Cells and B Cell Blasts Withstand Cryopreservation While Retaining Their Functionality for Producing Antibody

In individuals who have once developed humoral immunity to an infectious/foreign antigen, the antibodies present in their body can mediate instant protection when the antigen re-enters. Such antigen-specific antibodies can be readily detected in the serum. Long term humoral immunity is, however, also critically dependent on the ability of memory B cells to engage in a secondary antibody response upon re-exposure to the antigen. Antibody molecules in the body are short lived, having a half-life of weeks, while memory B cells have a life span of decades. Therefore, the presence of serum antibodies is not always a reliable indicator of B cell memory and comprehensive monitoring of humoral immunity requires that both serum antibodies and memory B cells be assessed. The prevailing view is that resting memory B cells and B cell blasts in peripheral blood mononuclear cells (PBMC) cannot be cryopreserved without losing their antibody secreting function, and regulated high throughput immune monitoring of B cell immunity is therefore confined to-and largely limited by-the need to test freshly isolated PBMC. Using optimized protocols for freezing and thawing of PBMC, and four color ImmunoSpot® analysis for the simultaneous detection of all immunoglobulin classes/subclasses we show here that both resting memory B cells and B cell blasts retain their ability to secrete antibody after thawing, and thus demonstrate the feasibility of B cell immune monitoring using cryopreserved PBMC.

Direct Detection of T- and B-Memory Lymphocytes by ImmunoSpot® Assays Reveals HCMV Exposure that Serum Antibodies Fail to Identify

It is essential to identify donors who have not been infected with human cytomegalovirus (HCMV) in order to avoid transmission of HCMV to recipients of blood transfusions or organ transplants. In the present study, we tested the reliability of seronegativity as an indicator for the lack of HCMV exposure in healthy human blood donors. Eighty-two HCMV seronegative individuals were identified, and their peripheral blood mononuclear cells (PBMC) were tested in ImmunoSpot® assays for the presence of HCMV-specific T- and B-memory lymphocytes. Eighty-two percent (67 of 82) of these HCMV seronegative individuals featured at least one memory cell that was lineage specific for HCMV, with the majority of these subjects possessing CD4+ and CD8+ T cells, as well as B cells, providing three independent lines of evidence for having developed immunity to HCMV. Only 15 of these 82 donors (18%) showed neither T- nor B-cell memory to HCMV, consistent with immunological naïveté to the virus. The data suggest that measurements of serum antibodies frequently fail to reveal HCMV exposure in humans, which may be better identified by direct detection of HCMV-specific memory lymphocytes.

Associations of social environment, socioeconomic position and social mobility with immune response in young adults: the Jerusalem Perinatal Family Follow-Up Study

OBJECTIVES

Immune response to cytomegalovirus (CMV) impacts adult chronic disease. This study investigates associations of childhood and adulthood social environment, socioeconomic position (SEP) and social mobility with CMV response in young adults.

DESIGN

Historical prospective study design.

SETTING

Subcohort of all 17 003 births to residents of Jerusalem between 1974 and 1976.

PARTICIPANTS

Participants included 1319 young adults born in Jerusalem with extensive archival and follow-up data, including childhood and adulthood SEP-related factors and anti-CMV IgG titre levels and seroprevalence measured at age 32.

MAIN EXPOSURE AND OUTCOME MEASURES

Principal component analysis was used to transform correlated social environment and SEP-related variables at two time points (childhood and adulthood) into two major scores reflecting household (eg, number of siblings/children, religiosity) and socioeconomic (eg, occupation, education) components. Based on these components, social mobility variables were created. Linear and Poisson regression models were used to investigate associations of components and mobility with anti-CMV IgG titre level and seroprevalence, adjusted for confounders.

RESULTS

Lower levels of household and socioeconomic components in either childhood or adulthood were associated with higher anti-CMV IgG titre level and seropositivity at age 32. Compared with individuals with stable favourable components, anti-CMV IgG titre level and risk for seropositivity were higher in stable unfavourable household and socioeconomic components (household: β=3.23, P<0.001; relative risk (RR)=1.21, P<0.001; socioeconomic: β=2.20, P=0.001; RR=1.14, P=0.01), downward household mobility (β=4.32, P<0.001; RR=1.26, P<0.001) and upward socioeconomic mobility (β=1.37, P=0.04; RR=1.19, P<0.001). Among seropositive individuals, associations between household components and mobility with anti-CMV IgG titre level were maintained and associations between socioeconomic components and mobility with anti-CMV IgG titre level were attenuated.

CONCLUSIONS

Our study provides evidence that accumulating low SEP from childhood through adulthood and social mobility may compromise immune response in young adulthood.

Impact of age and cytomegalovirus on CD8+ T-cell compartment remodeling after solid organ transplantation: A one-year follow-up study

Cytomegalovirus (CMV), a member of the β-herpesvirus family, is a major complicating infection in transplant patients. CMV latency has a long-term impact on CD8⁺ T-cell differentiation. It is unclear, however, whether this effect can be detected in one-year period. To investigate this, we analyzed the remodeling of the CD8⁺ T-cell compartment during the first year after solid organ transplantation. A total of 55 kidney or lung transplant patients were recruited. CD8⁺ T-cell subsets were prospectively analyzed at pretransplant, at 3 or 6months and 12months after transplantation (mo post-Tx). A significant increase in the frequency of CD27^-CD28^-CD8⁺ T cells (from 32.8% to 42.3%; p=0.014) was observed from pretransplant to 12mo post-Tx. Further analysis, however, showed that the largest expansion was observed from 3/6 to 12mo post-Tx whereas small non-significant variations were observed from pretransplant to 3/6mo post-Tx. The adjusted analysis showed that age and CMV seropositivity were statistically associated with the baseline frequency of CD27^-CD28^-CD8⁺ T cells. Additionally, CMV replication was related to the posttransplant expansion of this subpopulation, since it was not observed in patients without CMV viremia (24% vs. 4.2%). The results indicate that the expanded frequency associated with late CMV replication is additive to the baseline frequency related to aging and CMV seropositivity. If the expanded frequency remains at this high level for a long period it might have clinical consequences related to the control of future reactivations of CMV or of other related viruses.

An optimized IFN-γ ELISpot assay for the sensitive and standardized monitoring of CMV protein-reactive effector cells of cell-mediated immunity

Background

In healthy individuals, Cytomegalovirus (CMV) infection is efficiently controlled by CMV-specific cell-mediated immunity (CMI). Functional impairment of CMI in immunocompromized individuals however can lead to uncontrolled CMV replication and severe clinical complications. Close monitoring of CMV-specific CMI is therefore clinically relevant and might allow a reliable prognosis of CMV disease as well as assist personalized therapeutic decisions.

Methods

Objective of this work was the optimization and technical validation of an IFN-γ ELISpot assay for a standardized, sensitive and reliable quantification of CMV-reactive effector cells. T-activated® immunodominant CMV IE-1 and pp65 proteins were used as stimulants. All basic assay parameters and reagents were tested and optimized to establish a user-friendly protocol and maximize the signal-to-noise ratio of the ELISpot assay.

Results

Optimized and standardized ELISpot revealed low intra-assay, inter-assay and inter-operator variability (coefficient of variation CV below 22%) and CV inter-site was lower than 40%. Good assay linearity was obtained between 6 × 10⁴ and 2 × 10⁵ PBMC per well upon stimulation with T-activated® IE-1 (R² = 0.97) and pp65 (R² = 0.99) antigens. Remarkably, stimulation of peripheral blood mononuclear cells (PBMC) with T-activated® IE-1 and pp65 proteins resulted in the activation of a broad range of CMV-reactive effector cells, including CD3⁺CD4⁺ (Th), CD3⁺CD8⁺ (CTL), CD3⁻CD56⁺ (NK) and CD3⁺CD56⁺ (NKT-like) cells. Accordingly, the optimized IFN-γ ELISpot assay revealed very high sensitivity (97%) in a cohort of 45 healthy donors, of which 32 were CMV IgG-seropositive.

Conclusion

The combined use of T-activated® IE-1 and pp65 proteins for the stimulation of PBMC with the optimized IFN-γ ELISpot assay represents a highly standardized, valuable tool to monitor the functionality of CMV-specific CMI with great sensitivity and reliability.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-017-0195-y) contains supplementary material, which is available to authorized users.

Cytomegalovirus driven immunosenescence-An immune phenotype with or without clinical impact?

The continuous emerging increase in life span has led to vulnerability to a number of different diseases in the elderly. Some of these risks may be attributed to specific changes in the immune system referred to as immunoscenescence. This term aims to describe decreased immune functions among elderly individuals, and is characterized to be harmful age-associated changes in the immune system that lead to its gradual immune dysfunction. An impaired function of the immune system may increase susceptibility to various diseases in the elderly population such as infections, cardiovascular diseases and cancer. Although it is unclear how this immune phenotype develops, emerging evidence suggest that it may reflect an exhaustion of the immune system, possibly caused by one or several chronic infections. The main candidate is human cytomegalovirus (CMV), which can induce immune dysfunctions observed in immunoscenescence. Although the immune system is currently considered to be exhausted in CMV positive elderly individuals, it is not known whether such dysfunction of the immune system is a main reason for increased susceptibility to other diseases, or if direct effects of the virus in disease pathogenesis reflect the increased vulnerability to them. These aspects will be discussed in this review.

Cytomegalovirus transmission in pediatric renal transplant recipients during the window period

We report two CMV naïve children who received deceased donor renal transplants from a CMV IgG-negative single donor. CMV IgG in both recipients and the donor were negative immediately prior to transplant. Both recipients had early recurrences of their original disease in their transplants, requiring multiple sessions of plasmapheresis. All blood products used were leukoreduced or CMV seronegative. A few days post-transplant, both recipients developed significant positive CMV viremia. Both required initiation of oral valganciclovir. Case 1 responded to oral valganciclovir only while the case 2 had a delayed response to it and hence required intravenous ganciclovir with good response. When checked retrospectively, CMV IgM in the donor was positive along with positive CMV DNA PCR from the white cells. Here we describe a very unusual scenario of CMV transmission in two pediatric renal transplant recipients from a single donor during the CMV window period.

Physical function impairment of older, HIV-infected adults is associated with cytomegalovirus immunoglobulin response

Cytomegalovirus (CMV) is associated with poor outcomes, including physical function impairment, in older HIV-uninfected adults. Whether CMV is associated with physical functional impairment in HIV-infected adults is unknown. The primary objective of this study was to determine the relationship between CMV-specific humoral and cell-mediated immune responses with functional impairment in well-controlled HIV infection. In a case-control study, low-function cases were matched by age, gender, and time from HIV diagnosis to high-function controls. Quantitative CMV IgG and %CMV-specific CD8(+) and CD4(+) T cells (interferon-γ expression following CMV pp65 stimulation) were used to estimate physical function. Among 30 low-function cases and 48 high-function matched controls, CMV IgG ranged from <10 to 8,830 EU/ml, including four controls with results <10 EU/ml. Each log10 increase in CMV IgG was associated with 5-fold greater odds of low function (p=0.01); these findings were robust to adjustment for concomitant CD4(+) count, tobacco use, and age; to exclusion of subjects with CMV IgG <10 EU/ml; and to adjustment for hepatitis C viremia. %CMV-specific CD4(+) or CD8(+) T cells were not associated with low function. In bivariable models, the relationship between CMV IgG and physical function was attenuated and was no longer significant when including IL-6, CD4/CD8 ratio, or the Veterans Aging Cohort Study Index score. High levels of CMV-specific IgG were associated with impaired physical function. Attenuation of the strength of this association in bivariable models suggests an indirect relationship mediated by systemic inflammation and immune suppression.

Neonatal Transfusion Medicine: Five Major Unanswered Research Questions for the Twenty-First Century

Blood component transfusions are important to the care of preterm neonates; however, their use in clinical practice often is not based on high levels of evidence. Five major questions for neonates are discussed: (1) What is the optimal red blood cell (RBC) transfusion threshold? (2) What is the optimal platelet transfusion threshold? (3) Does the storage age of an RBC unit affect outcomes? (4) Does RBC transfusion contribute to the pathogenesis of necrotizing enterocolitis? and (5) Which new practices should be used to prevent transfusion-transmitted infections? Although definitive answers to these questions do not exist, future research should help answer them.

Discordant humoral and cellular immune responses to Cytomegalovirus (CMV) in glioblastoma patients whose tumors are positive for CMV

Background. Glioblastoma (GBM) is the most common malignant brain tumor in adults and is nearly always fatal. Emerging evidence suggests that human Cytomegalovirus (HCMV) is present in 90-100% of GBMs and that add-on antiviral treatment for HCMV show promise to improve survival. Methods. In a randomized, placebo-controlled trial of valganciclovir in 42 GBM patients, blood samples were collected for analyses of HCMV DNA, RNA, reactivity against HCMV peptides, IgG, and IgM at baseline and at 3, 12, and 24 weeks of treatment. Results. All 42 tumors were positive for HCMV protein. All patients examined had at least one blood sample positive for HCMV DNA, 63% were HCMV RNA positive, and 21% were IgM positive. However, 29% of GBM patients were IgG negative for HCMV. Five of these samples were positive in an enzyme-linked immunosorbent assay (ELISA) that used antigens derived from a clinical isolate. Blood T cells from 11 of 13 (85%) HCMV IgG-negative GBM patients reacted against HCMV peptides. Valganciclovir did not affect IgG titers, DNA, or RNA levels of the HCMV immediate early (HCMV IE) gene in blood. Conclusion. In GBM patients, HCMV activity is higher than in healthy controls and serology is a poor test to define previous or active HCMV infection in these patients.

Controlling cytomegalovirus: helping the immune system take the lead

Cytomegalovirus, of the Herpesviridae family, has evolved alongside humans for thousands of years with an intricate balance of latency, immune evasion, and transmission. While upwards of 70% of humans have evidence of CMV infection, the majority of healthy people show little to no clinical symptoms of primary infection and CMV disease is rarely observed during persistent infection in immunocompetent hosts. Despite the fact that the majority of infected individuals are asymptomatic, immunologically, CMV hijacks the immune system by infecting and remaining latent in antigen-presenting cells that occasionally reactivate subclinically and present antigen to T cells, eventually causing the inflation of CMV-specific T cells until they can compromise up to 10% of the entire T cell repertoire. Because of this impact on the immune system, as well as its importance in fields such as stem cell and organ transplant, the relationship between CMV and the immune response has been studied in depth. Here we provide a review of many of these studies and insights into how CMV-specific T cells are currently being used therapeutically.

Cytomegalovirus-specific responses of CD38⁺ memory T cells are skewed towards IFN-γ and dissociated from CD154 in HIV-1 infection

OBJECTIVE

Despite the strong correlation of T-cell CD38 expression with HIV disease progression, evidence linking CD38 expression and dysfunction at the single cell level is scant. Since CD38⁺ memory CD4⁺ T cells, especially those from HIV-infected persons, fail to induce CD154 (CD40L) while responding to a superantigen with interferon (IFN)-γ or interleukin (IL)-2, we aimed to determine if recall responses to cytomegalovirus (CMV) were similarly affected in the CD38⁺ memory CD4⁺ T-cell subpopulation.

DESIGN AND METHODS

Peripheral blood mononuclear cells from HIV+ patients and healthy controls were incubated 14 h with CMV antigens, the superantigen Staphylococcus aureus enterotoxin B or medium, and labeled for identification of central memory (T(CM)) and effector memory (T(EM)) CD4⁺ T cells, and for the intracellular detection of induced CD154, IFN-γ and/or IL-2 by flow cytometry.

RESULTS

Compared with CD38⁻ cells, CD38⁺ T(CM) cells from patients had less CD40L induction after CMV stimulation, and increased IFN-γ response. Patients' CD38⁺ T(EM) cells showed a lower IL-2 response, and tended to have a greater IFN-γ response, in which CD154 induction frequently failed. CMV-specific responses of patients' CD38⁺ T(CM) and T(EM) cells were dominated by IFN-γ, and almost all IL-2⁺ cells co-expressed IFN-γ. IL-2 responses to the polyclonal activator S. aureus enterotoxin B were also significantly less frequent among CD38⁺ T(CM) and T(EM) cells than in CD38⁻ cells.

CONCLUSION

Patients' CD38⁺ memory CD4⁺T-cell responses to CMV favor the effector cytokine IFN-γ over IL-2, in the context of deficient CD154 induction, which may limit co-stimulation, proliferation and survival.

Phenotypic and transcriptional profile correlates with functional plasticity of antigen-specific CD4+ T cells

The role of CD4(+) T cells in the control of infectious pathogens is highly complex with a myriad of functions but how these T cells acquire differential functional potentiality remains poorly defined. Here we show that human cytomegalovirus (CMV)-specific CD4(+) T cells directed towards different viral antigens expressed predominantly TNF-α alone or TNF-α and IFN-γ. TNF-α(+) and IFN-γ(+) CD4(+) T cells expressed significantly higher levels of T-box transcription factors T-bet with graded loss of Eomesodermin (Eomes) expression (T-bet(Hi)Eomes(Hi/Lo)) when compared with TNF-α(+) CD4(+) T cells expressing lower levels of both T-bet and Eomes (T-bet(-)Eomes(-)). Furthermore, TNF-α(+) and IFN-γ(+) CD4(+) T cells expressed significantly higher levels of perforin and interleukin (IL)-2 and displayed a terminally differentiated phenotype (CCR7(-)CD27(-)CD45RA(-)CD57(+)CD62L(-)). In contrast, TNF-α(+) alone CMV-specific CD4(+) T cells were predominantly early-memory phenotype with a proportion of these cells displaying T memory stem-cell phenotype (CD95(+)CD45RA(+)CCR7(+)CD27(+)). In vitro stimulation of CMV-specific CD4(+) T cells with viral antigen in the presence of IL-12 was sufficient to dramatically change the transcriptional and functional profile of TNF-α(+) CD4(+) T cells, whereas TNF-α(+) and IFN-γ(+) CD4(+) T cells remained unaltered. These findings illustrate an intrinsic link between cytokine expression, transcriptional regulation and cellular differentiation, and their impact on functional plasticity of virus-specific CD4(+) T cells.

Efficient human cytomegalovirus reactivation is maturation dependent in the Langerhans dendritic cell lineage and can be studied using a CD14+ experimental latency model

Studies from a number of laboratories have shown that the myeloid lineage is prominent in human cytomegalovirus (HCMV) latency, reactivation, dissemination, and pathogenesis. Existing as a latent infection in CD34(+) progenitors and circulating CD14(+) monocytes, reactivation is observed upon differentiation to mature macrophage or dendritic cell (DC) phenotypes. Langerhans' cells (LCs) are a subset of periphery resident DCs that represent a DC population likely to encounter HCMV early during primary infection. Furthermore, we have previously shown that CD34(+) derived LCs are a site of HCMV reactivation ex vivo. Accordingly, we have utilized healthy-donor CD34(+) cells to study latency and reactivation of HCMV in LCs. However, the increasing difficulty acquiring healthy-donor CD34(+) cells--particularly from seropositive donors due to the screening regimens used--led us to investigate the use of CD14(+) monocytes to generate LCs. We show here that CD14(+) monocytes cultured with transforming growth factor β generate Langerin-positive DCs (MoLCs). Consistent with observations using CD34(+) derived LCs, only mature MoLCs were permissive for HCMV infection. The lytic infection of mature MoLCs is productive and results in a marked inhibition in the capacity of these cells to promote T cell proliferation. Pertinently, differentiation of experimentally latent monocytes to the MoLC phenotype promotes reactivation in a maturation and interleukin-6 (IL-6)-dependent manner. Intriguingly, however, IL-6-mediated effects were restricted to mature LCs, in contrast to observations with classical CD14(+) derived DCs. Consequently, elucidation of the molecular basis behind the differential response of the two DC subsets should further our understanding of the fundamental mechanisms important for reactivation.

Cytomegalovirus infection and the risk of mortality and frailty in older women: a prospective observational cohort study

Cytomegalovirus (CMV), a prevalent pathogen, causes severe disease in immunocompromised humans. However, present understanding is limited regarding the long-term clinical effect of persistent CMV infection in immunocompetent adults. The authors conducted a prospective observational cohort study (1992-2002) of 635 community-dwelling women in Baltimore, Maryland, aged 70-79 years in the Women's Health and Aging Studies to examine the effect of CMV infection on the risk of frailty, a common geriatric syndrome, and mortality in older women. The effect of baseline serum CMV antibody (immunoglobulin G) concentration on the risk of 3-year incident frailty, defined by using a 5-component measure, and 5-year mortality was examined with Cox proportional hazards models. Compared with those who were CMV seronegative, women in the highest quartile of CMV antibody concentration had a greater incidence of frailty (hazard ratio = 3.46, 95% confidence interval: 1.45, 8.27) and mortality (hazard ratio = 3.81, 95% confidence interval: 1.64, 8.83). After adjustment for potential confounders, CMV antibody concentration in the highest quartile independently increased the risk of 5-year mortality (hazard ratio = 2.79, 95% confidence interval: 1.22, 6.40). Better understanding of the long-term clinical consequences of CMV infection in immunocompetent humans is needed to guide public health efforts for this widely prevalent infection.

Leukocyte depletion for safe blood transfusion

Leukocytes have ability to distinguish between self cells (body own cells) and foreign (allogenic) cells on the basis of human leukocyte antigen (HLA) proteins that are present on the cell membrane and are effectively unique to a person. During allogenic blood transfusion a person receives large number of allogenic donor leukocytes and these are recognized as foreign cells by the recipient immune system which leads to several adverse reactions. To avoid such leukocyte-mediated adverse reactions leukodepleted blood transfusion is required. Leukocytes can be separated on the basis of size, dielectric properties, by affinity separation, freeze-thawing and centrifugation but all these methods are time consuming and costly. Filtration is another method for leukocyte depletion that is comparatively less expensive and more efficient as it gives more than 90% leukodepletion of blood along with minimal cell loss. However, present filtration procedures also have some limitations as they work efficiently with blood components but not with whole blood and show non-specific adhesion of large number of platelets and red blood cells along with leukocytes. All the currently available filters are costly, which has been a major reason for their limited application. Therefore, demand for a more efficient and cost-effective filter is high in medical community and scientists are attenpting to improve the efficiency of currently available filters. The present review gives an overview of the significance of leukodepleted blood transfusion and focuses on different methods for leukocyte depletion and challenges involved in all these technologies.

Safety and immunogenicity of Towne cytomegalovirus vaccine with or without adjuvant recombinant interleukin-12

The Towne, human cytomegalovirus (CMV) vaccine is safe and immunogenic but has not prevented infection at doses tested to date. We administered 3000 pfu Towne CMV vaccine, with or without adjuvant recombinant interleukin-12 (rhIL-12), to CMV-seronegative healthy volunteers and then measured CMV gB-specific IgG titers and CMV-specific CD4+ and CD8+ T cell proliferation and IFNgamma expression after stimulation with whole viral lysate and immunodominant peptide CMV antigens. Adjuvant rhIL-12 at doses up to 2 microg were well-tolerated and associated with (1) dose-related increases in peak anti-CMV gB IgG titers (though not in sustained titers), (2) dose-related increases in the weak CMV viral lysate-specific CD4+ T cell proliferation responses induced by vaccine alone after 360 days of follow-up, and (3) decreases in the very robust CMV IE-specific peak CD4+ T cell and Day 360 CD8+ T cell proliferation responses induced by the vaccine alone. Also, qualitative CD8+ T cell IFNgamma responses to stimulation with the immunodominant CMV antigen, pp65, tended to occur more frequently in vaccinees who received 0.5-2.0 microg rhIL-12 compared to lower dose or no rhIL-12. Thus, adjuvant IL-12 may be a promising strategy for improving antibody and T cell immune responses to a CMV vaccine.

Impact of cryopreservation on tetramer, cytokine flow cytometry, and ELISPOT

Background

Cryopreservation of PBMC and/or overnight shipping of samples are required for many clinical trials, despite their potentially adverse effects upon immune monitoring assays such as MHC-peptide tetramer staining, cytokine flow cytometry (CFC), and ELISPOT. In this study, we compared the performance of these assays on leukapheresed PBMC shipped overnight in medium versus cryopreserved PBMC from matched donors.

Results

Using CMV pp65 peptide pool stimulation or pp65 HLA-A2 tetramer staining, there was significant correlation between shipped and cryopreserved samples for each assay (p ≤ 0.001). The differences in response magnitude between cryopreserved and shipped PBMC specimens were not significant for most antigens and assays. There was significant correlation between CFC and ELISPOT assay using pp65 peptide pool stimulation, in both shipped and cryopreserved samples (p ≤ 0.001). Strong correlation was observed between CFC (using HLA-A2-restricted pp65 peptide stimulation) and tetramer staining (p < 0.001). Roughly similar sensitivity and specificity were observed between the three assays and between shipped and cryopreserved samples for each assay.

Conclusion

We conclude that all three assays show concordant results on shipped versus cryopreserved specimens, when using a peptide-based readout. The assays are also concordant with each other in pair wise comparisons using equivalent antigen systems.

CMV antigen-specific CD4+ and CD8+ T cell IFNgamma expression and proliferation responses in healthy CMV-seropositive individuals

CMV-specific CD4+ and CD8+ T cell IFNgamma expression and proliferation were measured in healthy volunteers by flow cytometry after CMV lysate or CMV pp65 or IE peptide pool stimulation. Cutoff values were set to maximize specificity (i.e., no false positive CMV-seronegatives). Sensitivity (defined as a positive response in CMV-seropositives to at least one of the 3 antigen preparations used) was 100% for CMV-specific CD4+ and CD8+ T cell IFN expression and CD4+ T cell proliferation and 95.4% for CMV-specific CD8+ T cell proliferation. All 22 CMV-seropositive individuals had positive responses by at least three of these four measurements. These findings support the concept that a multiplicity of antigen-specific functional immune responses and persistence of robust virus-specific CD4+T cells are important components of protective immunity in this chronic viral infection.

Induction of cytomegalovirus-specific CD4+ cytotoxic T lymphocytes from seropositive or negative healthy subjects or stem cell transplant recipients

OBJECTIVE

We generated cytomegalovirus (CMV)-specific cytotoxic T lymphocytes (CTL) in vitro using dendritic cells (DC) pulsed with crude CMV antigens (Ag).

PATIENTS AND METHODS

Mononuclear cells from healthy CMV-seropositive or seronegative volunteers and from stem cell transplant (SCT) recipients were cultured with CD14(+) monocyte-derived DC prepulsed with CMV Ag and then matured in vitro with lipopolysaccharide and tumor necrosis factor-alpha. After proliferation, cells were checked for phenotype (CD4/CD8), while killing activity was measured by 51Cr-release assay.

RESULTS

CD4(+) T cells, the main proliferating cells from both seropositive and seronegative individuals, killed autologous Ag-pulsed DC but not vehicle-pulsed autologous DC or CMV-pulsed allogeneic DC. Similar CTL induction was accomplished from SCT recipients. Significant killing of autologous CMV-infected fibroblasts required 16-hour incubation as opposed to the standard 4-hour incubation, which was prevented by either a perforin inhibitor or anti-Fas ligand monoclonal antibody. CTL enhanced surface HLA-DR expression of CMV-infected fibroblasts, and their activity was neutralized by anti-HLA-DR monoclonal antibody.

CONCLUSION

CMV-specific CD4(+) CTL were inducible with or without antiviral humoral immunity, even from immunosuppressed SCT recipients. These CTL showed perforin- and Fas/Fas ligand-mediated cytotoxicity after long-term (16-hour) contact with CMV-infected targets.

Cytomegalovirus M43 gene modulates T helper cell response

Role of viral genes in modulating T helper 1 (Th1) and T helper 2 (Th2) balance is of principal interest in the study of cytomegalovirus (CMV) immunity. Murine CMV (MCMV) mutants were used to explore a possible mechanism for the ability of virus to induce a predominant Th1 response and to suppress Th2 response by examining the production of Th1 (IFN-gamma, IL-2) and Th2 (IL-4, IL-10) cytokines by the splenocytes of mice infected with wild type (WT) and MCMV mutants. Results (n=6) show that as compared with WT, the MCMV mutant with specific disruption of M43 gene upregulates the production of IL-4 (P=0.0002) and to a lesser extent IL-10 (P=0.015) at 14 days post infection. This indicates that M43 gene may play a role in suppressing Th2 (IL-4) production, especially in the later stage of infection. The IL-4 and IL-10 production during infection with M43 mutant occurs in the presence of a strong IFN-gamma (Th1) response, overriding the cross-regulatory effects of these cytokines within the Th1/Th2 paradigm and suggesting that the predominant response during CMV infection is still a Th1 type response.

HIV, 'an evolving species'. Roles of cellular activation and co-infections

Each small variation of the genome of a species can be preserved if it is useful for the survival of the species in a given environment. Within this framework, the finality of the biological cycle of HIV consists in a search for harmony (biological coherence) with man, which is to say a stable condition. Cellular activation appears to be the strategy developed by HIV in order to achieve this coherence. The price of this strategy is the AIDS. The first contact between HIV and immune system appears to determine the subsequent clinical outcome and the future of HIV. Lymphocytic activation varies during the course of the vital cycle of HIV. For each individual, this lymphocytic activation depends on both the HLA repertoire acquired during thymic ontogenesis and the antigenic experience before and after HIV infection. Thus intercurrent infections alter the immune condition of the organism and influence the outcome of HIV. We described a synthetic analysis of the effects of HIV on the surface protein expression and the cellular activation pathways which should provide insights in the evolutionary relationship between HIV and man and should permit to do a more physiological therapeutic approach.

CMV DNA is rarely detected in healthy blood donors using validated PCR assays

BACKGROUND

Although serologic screening or WBC reduction of blood components can reduce the incidence of transfusion-transmitted CMV (TT-CMV) infection, 'breakthrough' cases of TT-CMV still occur and may produce serious sequelae. NAT of blood components for CMV DNA has been proposed to further reduce the risks of TT-CMV. However, large-scale studies to determine the utility of validated CMV NAT assays for donor screening have not been reported.

STUDY DESIGN AND METHODS

Coded whole-blood samples (n=1000) were tested for the presence of CMV DNA using two CMV PCR assays previously validated in a multicenter trial (a nested PCR assay directed at the CMV UL93 open-reading frame and the Roche Monitor assay). Corresponding plasma samples were tested in parallel for the presence of anti-CMV using other assays (Abbott CMV EIA and Fujirebio/Olympus CMV particle agglutination assays).

RESULTS

In total 416 and 514 of the samples tested as CMV-seropositive and -seronegative, respectively, by both antibody assays. The remaining 70 samples had discrepant serology results. Only 2 of the 1000 samples (both seropositive) had reproducibly detectable CMV DNA (positive in at least three of four replicates). CMV DNA was not reproducibly detected in seronegative samples or in samples with discrepant serology results.

CONCLUSIONS

Although previous investigations showed frequent detection of CMV DNA in healthy CMV-seropositive (and some seronegative) blood donors, these studies were relatively small and the performance characteristics of their assays were difficult to evaluate. In contrast, the present large cross-sectional study of US donors utilized two previously validated PCR assays and demonstrated that CMV DNA is only rarely detectable in seropositive donors. Thus, the use of CMV PCR assays with optimal performance characteristics did not increase the detection of potentially infectious blood components beyond that provided by current serologic screening assays.

Dominance of virus-specific CD8 T cells in human primary cytomegalovirus infection

Cellular immune responses are of high importance in initiating and maintaining immunity against virus infections. Whereas the cellular immune response during persistent cytomegalovirus (CMV) infection is well assessable, the individual contribution of CD4 and CD8 T cell responses during primary infection has not been described. A novel whole-blood assay, which relies on the flow-cytometric detection of antigen-induced cytokine expression, was used to characterize CMV-specific CD4 and CD8 T cell responses during primary infection of CMV seronegative recipients of a renal allograft from a CMV seropositive donor. These T cell responses were compared with long-term CMV-positive patients with known history of transplantation-related seroconversion. Results were further correlated to CMV load and serum IgG and IgM. The long-term seroconverted patients consistently showed a dominant CMV-specific CD4 T cell response (median frequencies: CD4, 1.12% [range, 0.35 to 8.10%] versus CD8 0.13% [range, <0.05 to 0.55%]). In contrast, during primary infection, the cellular immune response is strongly dominated by CMV-specific CD8 T cells (median peak frequencies: CD4, 1.24% [range, 0.21 to 1.60%] versus CD8, 2.47% [range, 1.34 to 6.67%]). Upon receipt of ganciclovir, viral load as well as CMV-specific CD8 responses decreased. The frequency of the respective CD4 T cells fluctuated during decrease of CMV load and became dominant over CMV-specific CD8 T cell responses. These results are consistent with the view of an effective direct antiviral activity of CD8 T cells, which is most critical during periods of high viremia. Later on during persistent infection, CD4 T cells dominate the immune response to support the state of antiviral immunity.

CMV and blood transfusions

Among the human herpesviruses, cytomegalovirus (CMV) is the only one that has assumed significant importance in blood transfusion. Transfusion transmission of CMV (TT-CMV) to seronegative immunocompromised patients can lead to lethal CMV disease. Studies over the past 30 years have demonstrated that monocytes latently infected with CMV represent the primary vector for TT-CMV, and that TT-CMV can be largely abrogated by transfusing at-risk patients with either seronegative units or blood filtered to remove white blood cells. However, the small number of cases of breakthrough TT-CMV that follow transfusion of either seronegative or filtered blood still produce morbidity and mortality. These circumstances have motivated ongoing efforts to provide improved protection from TT-CMV, including the use of CMV DNA amplification for blood screening, and pathogen inactivation to sterilise all blood components prior to transfusion.