Dynamics of T cell memory in human cytomegalovirus infection

Memory inflation: Beyond the acute phase of viral infection

Memory inflation is confirmed as the most commonly dysregulation of host immunity with antigen-independent manner in mammals after viral infection. By generating large numbers of effector/memory and terminal differentiated effector memory CD8+ T cells with diminished naïve subsets, memory inflation is believed to play critical roles in connecting the viral infection and the onset of multiple diseases. Here, we reviewed the current understanding of memory inflated CD8+ T cells in their distinct phenotypic features that different from exhausted subsets; the intrinsic and extrinsic roles in regulating the formation of memory inflation; and the key proteins in maintaining the expansion and proliferation of inflationary populations. More importantly, based on the evidences from both clinic and animal models, we summarized the potential mechanisms of memory inflation to trigger autoimmune neuropathies, such as Guillain-Barré syndrome and multiple sclerosis; the correlations of memory inflation between tumorigenesis and resistance of tumour immunotherapies; as well as the effects of memory inflation to facilitate vascular disease progression. To sum up, better understanding of memory inflation could provide us an opportunity to beyond the acute phase of viral infection, and shed a light on the long-term influences of CD8+ T cell heterogeneity in dampen host immune homeostasis.

Human cytomegalovirus microRNAs: strategies for immune evasion and viral latency

Viruses use various strategies and mechanisms to deal with cells and proteins of the immune system that form a barrier against infection. One of these mechanisms is the encoding and production of viral microRNAs (miRNAs), whose function is to regulate the gene expression of the host cell and the virus, thus creating a suitable environment for survival and spreading viral infection. miRNAs are short, single-stranded, non-coding RNA molecules that can regulate the expression of host and viral proteins, and due to their non-immunogenic nature, they are not eliminated by the cells of the immune system. More than half of the viral miRNAs are encoded and produced by Orthoherpesviridae family members. Human cytomegalovirus (HCMV) produces miRNAs that mediate various processes in infected cells to contribute to HCMV pathogenicity, including immune escape, viral latency, and cell apoptosis. Here, we discuss which cellular and viral proteins or cellular pathways and processes these mysterious molecules target to evade immunity and support viral latency in infected cells. We also discuss current evidence that their function of bypassing the host's innate and adaptive immune system is essential for the survival and multiplication of the virus and the spread of HCMV infection.

Multimodal HLA-I genotype regulation by human cytomegalovirus US10 and resulting surface patterning

Human leucocyte antigen class I (HLA-I) molecules play a central role for both NK and T-cell responses that prevent serious human cytomegalovirus (HCMV) disease. To create opportunities for viral spread, several HCMV-encoded immunoevasins employ diverse strategies to target HLA-I. Among these, the glycoprotein US10 is so far insufficiently studied. While it was reported that US10 interferes with HLA-G expression, its ability to manipulate classical HLA-I antigen presentation remains unknown. In this study, we demonstrate that US10 recognizes and binds to all HLA-I (HLA-A, -B, -C, -E, -G) heavy chains. Additionally, impaired recruitment of HLA-I to the peptide loading complex was observed. Notably, the associated effects varied significantly dependending on HLA-I genotype and allotype: (i) HLA-A molecules evaded downregulation by US10, (ii) tapasin-dependent HLA-B molecules showed impaired maturation and cell surface expression, and (iii) β2m-assembled HLA-C, in particular HLA-C*05:01 and -C*12:03, and HLA-G were strongly retained in complex with US10 in the endoplasmic reticulum. These genotype-specific effects on HLA-I were confirmed through unbiased HLA-I ligandome analyses. Furthermore, in HCMV-infected fibroblasts inhibition of overlapping US10 and US11 transcription had little effect on HLA-A, but induced HLA-B antigen presentation. Thus, the US10-mediated impact on HLA-I results in multiple geno- and allotypic effects in a so far unparalleled and multimodal manner.

Fractalkine/CX3CR1 in Dilated Cardiomyopathy: A Potential Future Target for Immunomodulatory Therapy?

Dilated cardiomyopathy (DCM) is a cardiac condition with structural and functional impairment, where either the left ventricle or both ventricular chambers are enlarged, coinciding with reduced systolic pump function (reduced ejection fraction, rEF). The prevalence of DCM is more than 1:250 individuals, and mortality largely due to heart failure in two-third of cases, and sudden cardiac death in one-third of patients. Damage to the myocardium, whether from a genetic or environmental cause such as viruses, triggers inflammation and recruits immune cells to the heart to repair the myocardium. Examination of myocardial biopsy tissue often reveals an inflammatory cell infiltrate, T lymphocyte (T cell) infiltration, or other activated immune cells. Despite medical therapy, adverse outcomes for DCM remain. The evidence base and existing literature suggest that upregulation of CX3CR1, migration of immune cells, together with cytomegalovirus (CMV) seropositivity is associated with worse outcomes in patients with dilated cardiomyopathy. We hypothesise that this potentially occurs through cardiac inflammation and fibrosis, resulting in adverse remodelling. Immune modulators to target this pathway may potentially improve outcomes above and beyond current guideline-recommended therapy.

Applications of Anti-Cytomegalovirus T Cells for Cancer (Immuno)Therapy

Infection with cytomegalovirus (CMV) is highly prevalent in the general population and largely controlled by CD8pos T cells. Intriguingly, anti-CMV T cells accumulate over time to extraordinarily high numbers, are frequently present as tumor-resident 'bystander' T cells, and remain functional in cancer patients. Consequently, various strategies for redirecting anti-CMV CD8pos T cells to eliminate cancer cells are currently being developed. Here, we provide an overview of these strategies including immunogenic CMV peptide-loading onto endogenous HLA complexes on cancer cells and the use of tumor-directed fusion proteins containing a preassembled CMV peptide/HLA-I complex. Additionally, we discuss conveying the advantageous characteristics of anti-CMV T cells in adoptive cell therapy. Utilization of anti-CMV CD8pos T cells to generate CAR T cells promotes their in vivo persistence and expansion due to appropriate co-stimulation through the endogenous (CMV-)TCR signaling complex. Designing TCR-engineered T cells is more challenging, as the artificial and endogenous TCR compete for expression. Moreover, the use of expanded/reactivated anti-CMV T cells to target CMV peptide-expressing glioblastomas is discussed. This review highlights the most important findings and compares the benefits, disadvantages, and challenges of each strategy. Finally, we discuss how anti-CMV T cell therapies can be further improved to enhance treatment efficacy.

Familial CD45RA- T cells to treat severe refractory infections in immunocompromised patients

Background

Immunocompromised patients are susceptible to high-risk opportunistic infections and malignant diseases. Most antiviral and antifungal drugs are quite toxic, relatively ineffective, and induce resistance in the long term. The transfer of pathogen-specific Cytotoxic T-Lymphocytes has shown a minimal toxicity profile and effectiveness in treating Cytomegalovirus, Adenovirus, Epstein - Barr virus, BK Virus and Aspergillus infections, but this therapy have the main limitations of regulatory issues, high cost, and absence of public cell banks. However, CD45RA^- cells containing pathogen-specific memory T-cells involve a less complex manufacturing and regulatory process and are cheaper, feasible, safe, and potentially effective.

Methods

We present preliminary data from six immunocompromised patients: four who had severe infectious diseases and two who had EBV lymphoproliferative disease. All of them underwent multiple safe familial CD45RA^- T-cell infusions as adoptive passive cell therapy, containing Cytomegalovirus, Epstein - Barr virus, BK virus, and Aspergillus-specific memory T-cells. We also present the method for selecting the best donors for CD45RA^- cells in each case and the procedure to isolate and store these cells.

Results

The infusions were safe, there was no case of graft-versus host disease, and they showed a clear clinical benefit. The patients treated for BK virus nephritis, Cytomegalovirus encephalitis, Cytomegalovirus reactivation, and disseminated invasive aspergillosis experienced pathogen clearance, complete resolution of symptoms in 4-6 weeks and a lymphocyte increase in 3 of 4 cases after 3-4 months. Donor T cell transient microchimerism was detected in one patient. The two patients treated for EBV lymphoproliferative disease underwent chemotherapy and several infusions of CD45RA^- memory T-cells containing EBV cytotoxic lymphocytes. Donor T-cell microchimerism was observed in both patients. The viremia cleared in one of the patients, and in the other, despite the viremia not clearing, hepatic lymphoproliferative disease remained stable and was ultimately cured with EBV-specific Cytotoxic T-Lymphocytes.

Conclusion

The use of familial CD45RA^- T-cells containing specific Cytotoxic T-lymphocytes is a feasible, safe and potential effective approach for treating severe pathogen infections in immunocompromised patients through a third party donor. Furthermore, this approach might be of universal use with fewer institutional and regulatory barriers.

Comparative clinical manifestations and immune effects of cytomegalovirus infections following distinct types of immunosuppression

BACKGROUND

Cytomegalovirus (CMV) infection is a well-recognized complication of solid organ and hematopoietic cell transplantation. However, CMV infection also occurs in patients with human immunodeficiency virus (HIV) infection, previously immunocompetent intensive care unit (ICU) patients, and individuals on immunosuppressive medications for various underlying diseases.

OBJECTIVES

This review describes the comparative effects of CMV infection in distinct types of acquired immunosuppression.

SOURCES

Selected peer-reviewed publications on CMV infections published until December 2021.

CONTENT

CMV infection affects various organ systems through direct cytolytic mechanisms, but may also exert indirect effects by promoting pro-inflammatory and immunosuppressive responses. This has been well studied in transplant recipients, for whom antiviral prophylaxis and pre-emptive therapy have now become standard practice. These strategies not only prevent direct CMV disease manifestations, but also mitigate various immunopathological processes to reduce graft-versus-host disease, graft rejection, and the occurrence of secondary bacterial and fungal infections. The efficacy of neither prophylactic nor pre-emptive treatment of CMV infection has been demonstrated for patients with critical illness- or medication-induced immunosuppression. Many observational studies have shown an independent association between CMV reactivation and a prolonged duration of mechanical ventilation or increased mortality in the ICU. Furthermore, data suggest that CMV reactivation may increase pulmonary inflammation and prolong the duration of mechanical ventilation.

IMPLICATIONS

A large number of observational and experimental studies suggest attributable morbidity and mortality related to CMV infection, not only in transplant recipients and patients with HIV infection but also in patients with critically illness- or medication-induced immunosuppression. Adequately powered randomized controlled trials investigating the efficacy of prophylaxis or pre-emptive treatment of CMV infection in these patients are lacking, with a notable exception for transplant recipients.

Identification of Naturally Processed Epitope Region Using Artificial APC Expressing a Single HLA Class I Allotype and mRNA of HCMV pp65 Antigen Fragments

Recently, long synthetic peptides or in silico-predicted epitope peptides have been used to identify T cell epitopes, but these approaches may not be suitable for investigating naturally processed epitopes. Here, mRNAs, including fragments or predicted epitope sequences of HCMV pp65 antigen, were generated by in vitro transcription following transcriptionally active PCR. Then, artificial antigen-presenting cells (aAPCs) expressing a single HLA allotype were transfected with mRNAs to identify epitopes in donors with T cell responses that recognize pp65 antigen restricted to HLA-A*02:01, -A*02:06, or -B*07:02. T cells restricted to a particular HLA allotype showed positive responses in some of the 10 fragment antigens. Among predicted epitopes within these positive fragments, three epitopes of HLA-A*02:01, -A*02:06, and -B*07:02 were confirmed. In addition, T cells expanded by anti-CD3 stimulation for two weeks could also be effectively used for the identification of these T cell epitopes, although there were individual differences. These results demonstrated that fragment antigens and epitopes can be rapidly generated using mRNA, and naturally processed antigenic regions can be detected using aAPCs without a T cell cloning procedure. This method will help to identify novel T cell epitopes for developing immunotherapy and vaccines against infectious diseases and cancer.

NK and CD8+ T cell phenotypes predict onset and control of CMV viremia after kidney transplant

CMV causes mostly asymptomatic but lifelong infection. Primary infection or reactivation in immunocompromised individuals can be life-threatening. CMV viremia often occurs in solid organ transplant recipients and associates with decreased graft survival and higher mortality. Furthering understanding of impaired immunity that allows CMV reactivation is critical to guiding antiviral therapy and examining the effect of CMV on solid organ transplant outcomes. This study characterized longitudinal immune responses to CMV in 31 kidney transplant recipients with CMV viremia and matched, nonviremic recipients. Recipients were sampled 3 and 12 months after transplant, with additional samples 1 week and 1 month after viremia. PBMCs were stained for NK and T cell markers. PBMC transcriptomes were characterized by RNA-Seq. Plasma proteins were quantified by Luminex. CD8⁺ T cell transcriptomes were characterized by single-cell RNA-Seq. Before viremia, patients had high levels of IL-15 with concurrent expansion of immature CD56^bright NK cells. After viremia, mature CD56^dim NK cells and CD28^–CD8⁺ T cells upregulating inhibitory and NK-associated receptors were expanded. Memory NK cells and NK-like CD28^–CD8⁺ T cells were associated with control of viremia. These findings suggest that signatures of innate activation may be prognostic for CMV reactivation after transplant, while CD8⁺ T cell functionality is critical for effective control of CMV.

HLA-B locus products resist degradation by the human cytomegalovirus immunoevasin US11

To escape CD8+ T-cell immunity, human cytomegalovirus (HCMV) US11 redirects MHC-I for rapid ER-associated proteolytic degradation (ERAD). In humans, classical MHC-I molecules are encoded by the highly polymorphic HLA-A, -B and -C gene loci. While HLA-C resists US11 degradation, the specificity for HLA-A and HLA-B products has not been systematically studied. In this study we analyzed the MHC-I peptide ligands in HCMV-infected cells. A US11-dependent loss of HLA-A ligands was observed, but not of HLA-B. We revealed a general ability of HLA-B to assemble with β₂m and exit from the ER in the presence of US11. Surprisingly, a low-complexity region between the signal peptide sequence and the Ig-like domain of US11, was necessary to form a stable interaction with assembled MHC-I and, moreover, this region was also responsible for changing the pool of HLA-B ligands. Our data suggest a two-pronged strategy by US11 to escape CD8+ T-cell immunity, firstly, by degrading HLA-A molecules, and secondly, by manipulating the HLA-B ligandome.

The human immune system can cover the presentation of a wide array of pathogen derived antigens owing to the three extraordinary polymorphic MHC class I (MHC-I) gene loci, called HLA-A, -B and -C in humans. Studying the HLA peptide ligands of human cytomegalovirus (HCMV) infected cells, we realized that the HCMV encoded glycoprotein US11 targeted different HLA gene products in distinct manners. More than 20 years ago the first HCMV encoded MHC-I inhibitors were identified, including US11, targeting MHC-I for proteasomal degradation. Here, we describe that the prime target for US11-mediated degradation is HLA-A, whereas HLA-B can resist degradation. Our further mechanistic analysis revealed that US11 uses various domains for distinct functions. Remarkably, the ability of US11 to interact with assembled MHC-I and modify peptide loading of degradation-resistant HLA-B was dependent on a low-complexity region (LCR) located between the signal peptide and the immunoglobulin-like domain of US11. To redirect MHC-I for proteasomal degradation the LCR was dispensable. These findings now raise the intriguing question why US11 has evolved to target HLA-A and -B differentially. Possibly, HLA-B molecules are spared in order to dampen NK cell attack against infected cells.

Challenges and Clinical Implications of the Diagnosis of Cytomegalovirus Lung Infection in Children

PURPOSE OF REVIEW

Pulmonary cytomegalovirus (CMV) infection is a potential lethal disease in children, but it remains a diagnostic challenge. The differentiation between latent CMV infections with viral shedding and active infections is difficult and may lead to false positives in bronchoalvolar lavage (BAL) PCR detection. This review summarizes current diagnostic approaches for CMV lung infection in children including progress in the identification of underlying immune defects linked to this condition.

RECENT FINDINGS

There is increasing literature supporting that the combined assessment of host risk factors and lung disease pattern is essential for the diagnosis of pulmonary CMV infection in children. The most important host risk factor is an immunecompromised state that has expanded from primary or acquired immunodeficiency (e.g., HIV) to include a myriad of immune-dysregulation syndromes (e.g., CTLA4, PIK3 defects). Newborns, paricularly those born premature, are also a high-risk group. At the pulmonary level, active CMV infection is typically characterized by alveolar compromise leading to hypoxemia, ground-glass opacities, and intra-alveolar infiltrates with CMV inclusions in lung biopsy. The identification of active CMV lung infection should trigger additional evaluation of immune defects (primary or secondary) impairing T and NK cell function or innate antiviral responses as well as other immune dysregulation disorders. Lung CMV infections in children are more prevalent in immunocompromised hosts and premature newborns. Lung CMV infections should prompt further investigation into conditions altering immune mechanisms usually in place to contain CMV infections. Common clinical and radiological patterns such as hypoxemia and ground-glass pulmonary opacities may allow early identification and treatment of CMV lung infection and underlying causes in the pediatric population.

Control of primary mouse cytomegalovirus infection in lung nodular inflammatory foci by cooperation of interferon-gamma expressing CD4 and CD8 T cells

Human cytomegalovirus (CMV) and mouse cytomegalovirus (MCMV) infection share many characteristics. Therefore infection of mice with MCMV is an important tool to understand immune responses and to design vaccines and therapies for patients at the risk of severe CMV disease. In this study, we investigated the immune response in the lungs following acute infection with MCMV. We used multi-color fluorescence microscopy to visualize single infected and immune cells in nodular inflammatory foci (NIFs) that formed around infected cells in the lungs. These NIFs consisted mainly of myeloid cells, T cells, and some NK cells. We found that the formation of NIFs was essential to reduce the number of infected cells in the lung tissue, showing that NIFs were sites of infection as well as sites of immune response. Comparing mice deficient for several leukocyte subsets, we identified T cells to be of prime importance for restricting MCMV infection in the lung. Moreover, T cells had to be present in NIFs in high numbers, and CD4 as well as CD8 T cells supported each other to efficiently control virus spread. Additionally, we investigated the effects of perforin and interferon-gamma (IFNγ) on the virus infection and found important roles for both mechanisms. NK cells and T cells were the major source for IFNγ in the lung and in in vitro assays we found that IFNγ had the potential to reduce plaque growth on primary lung stromal cells. Notably, the T cell-mediated control was shown to be perforin-independent but IFNγ-dependent. In total, this study systematically identifies crucial antiviral factors present in lung NIFs for early containment of a local MCMV infection at the single cell level.

The (gradual) rise of memory inflation

Memory inflation, as a term, has been used for 15 years now to describe the longitudinal development of stable, expanded CD8+ T memory pools with a distinct phenotype and functional profile which emerge in specific infection and vaccine settings. These settings have in common the persistence of antigen, especially cytomegalovirus infection but also more recently adenoviral vector vaccination. However, in contrast to chronic infections which lead to "exhaustion" the repeated antigen encounters experienced by CD8+ T cells lead to development of a robust T-cell population structure which maintains functionality and size. In this review, I will discuss how the ideas around this form of memory have evolved over time and some new models which can help explain how these populations are induced and sustained. These models are relevant to immunity against persistent viruses, to novel vaccine strategies and to concepts about aging.

Cytomegalovirus (CMV) Epitope-Specific CD4+ T Cells Are Inflated in HIV+ CMV+ Subjects

Select CMV epitopes drive life-long CD8⁺ T cell memory inflation, but the extent of CD4 memory inflation is poorly studied. CD4⁺ T cells specific for human CMV (HCMV) are elevated in HIV⁺ HCMV⁺ subjects. To determine whether HCMV epitope-specific CD4⁺ T cell memory inflation occurs during HIV infection, we used HLA-DR7 (DRB1*07:01) tetramers loaded with the glycoprotein B DYSNTHSTRYV (DYS) epitope to characterize circulating CD4⁺ T cells in coinfected HLA-DR7⁺ long-term nonprogressor HIV subjects with undetectable HCMV plasma viremia. DYS-specific CD4⁺ T cells were inflated among these HIV⁺ subjects compared with those from an HIV^- HCMV⁺ HLA-DR7⁺ cohort or with HLA-DR7-restricted CD4⁺ T cells from the HIV-coinfected cohort that were specific for epitopes of HCMV phosphoprotein-65, tetanus toxoid precursor, EBV nuclear Ag 2, or HIV gag protein. Inflated DYS-specific CD4⁺ T cells consisted of effector memory or effector memory-RA⁺ subsets with restricted TCRβ usage and nearly monoclonal CDR3 containing novel conserved amino acids. Expression of this near-monoclonal TCR in a Jurkat cell-transfection system validated fine DYS specificity. Inflated cells were polyfunctional, not senescent, and displayed high ex vivo levels of granzyme B, CX₃CR1, CD38, or HLA-DR but less often coexpressed CD38⁺ and HLA-DR⁺ The inflation mechanism did not involve apoptosis suppression, increased proliferation, or HIV gag cross-reactivity. Instead, the findings suggest that intermittent or chronic expression of epitopes, such as DYS, drive inflation of activated CD4⁺ T cells that home to endothelial cells and have the potential to mediate cytotoxicity and vascular disease.

Impact of Aging and Cytomegalovirus on Immunological Response to Influenza Vaccination and Infection

The number of people over the age of 60 is expected to double by 2050 according to the WHO. This emphasizes the need to ensure optimized resilience to health stressors in late life. In older adults, influenza is one of the leading causes of catastrophic disability (defined as the loss of independence in daily living and self-care activities). Influenza vaccination is generally perceived to be less protective in older adults, with some studies suggesting that the humoral immune response to the vaccine is further impaired in cytomegalovirus (CMV)-seropositive older people. CMV is a β-herpes virus infection that is generally asymptomatic in healthy individuals. The majority of older adults possess serum antibodies against the virus indicating latent infection. Age-related changes in T-cell-mediated immunity are augmented by CMV infection and may be associated with more serious complications of influenza infection. This review focuses on the impact of aging and CMV on immune cell function, the response to influenza infection and vaccination, and how the current understanding of aging and CMV can be used to design a more effective influenza vaccine for older adults. It is anticipated that efforts in this field will address the public health need for improved protection against influenza in older adults, particularly with regard to the serious complications leading to loss of independence.

Brief Report: Soluble CD163 in CMV-Infected and CMV-Uninfected Subjects on Virologically Suppressive Antiretroviral Therapy in the ICONA Cohort

AIMS

To contribute to the understanding of the role played by cytomegalovirus (CMV) in sustaining monocyte/macrophage-mediated immune activation in antiretroviral therapy treated HIV-infected subjects.

DESIGN AND METHODS

We selected 23 CMV-uninfected and 46 CMV-infected HIV+ subjects, matched for age, CD4 nadir, HIV infection duration, and viral hepatitis serostatus. All subjects were on successful antiretroviral therapy since at least 1 year. A group of 16 healthy donors with similar age and sex was also included. Plasma levels of tumor necrosis factor-alpha, interleukin-6, sCD163, sCD14, and CMV immunoglobulin G levels were measured in duplicate with human enzyme-linked immunosorbent assay kits.

RESULTS

We found significantly higher sCD163 plasma levels in HIV+CMV+ compared with HIV+CMV- subjects and healthy donors. This augmentation was confirmed also when subjects positive for hepatitis C virus-Ab were excluded from analysis. Interestingly, a correlation between anti-CMV immunoglobulin G levels and sCD163, tumor necrosis factor-alpha, interleukin-6, and sCD14 in HIV+CMV+ subjects was found.

CONCLUSIONS

CMV coinfection could be a major driver of monocyte/macrophage activation in virally suppressed HIV+ individuals and might explain the increased risk of non-AIDS morbidity/mortality in HIV/CMV-coinfected subjects.

Refining human T-cell immunotherapy of cytomegalovirus disease: a mouse model with 'humanized' antigen presentation as a new preclinical study tool

With the cover headline 'T cells on the attack,' the journal Science celebrated individualized cancer immunotherapy by adoptive transfer of T cells as the 'Breakthrough of the Year' 2013 (J. Couzin-Frankel in Science 342:1432-1433, 2013). It is less well recognized and appreciated that individualized T cell immunotherapy of cytomegalovirus (CMV) infection is approaching clinical application for preventing CMV organ manifestations, interstitial CMV pneumonia in particular. This coincident medical development is particularly interesting as reactivated CMV infection is a major viral complication in the state of transient immunodeficiency after the therapy of hematopoietic malignancies by hematopoietic cell transplantation (HCT). It may thus be attractive to combine T cell immunotherapy of 'minimal residual disease/leukemia (MRD)' and CMV-specific T cell immunotherapy to combat both risks in HCT recipients simultaneously, and ideally with T cells derived from the respective HLA-matched HCT donor. Although clinical trials of human CMV-specific T cell immunotherapy were promising in that the incidence of virus reactivation and disease was found to be reduced with statistical significance, animal models are still instrumental for providing 'proof of concept' by directly documenting the prevention of viral multiple-organ histopathology and organ failure under controlled conditions of the absence versus presence of the therapy, which obviously is not feasible in an individual human patient. Further, animal models can make predictions regarding parameters that determine the efficacy of T cell immunotherapy for improved study design in clinical investigations, and they allow for manipulating host and virus genetics. The latter is of particular value as it opens the possibility for epitope specificity controls that are inherently missing in clinical trials. Here, we review a recently developed new mouse model that is more approximated to human CMV-specific T cell immunotherapy by 'humanizing' antigen presentation using antigenically chimeric CMV and HLA-transgenic mice to allow for an in vivo testing of the antiviral function of human CMV-specific T cells. As an important new message, this model predicts that T cell immunotherapy is most efficient if CD4 T cells are equipped with a transduced TCR directed against an epitope presented by MHC/HLA class-I for local delivery of 'cognate' help to CD8 effector T cells at infected MHC/HLA class-II-negative host tissue cells.

The Expression of Human Cytomegalovirus MicroRNA MiR-UL148D during Latent Infection in Primary Myeloid Cells Inhibits Activin A-triggered Secretion of IL-6

The successful establishment and maintenance of human cytomegalovirus (HCMV) latency is dependent on the expression of a subset of viral genes. Whilst the exact spectrum and functions of these genes are far from clear, inroads have been made for protein-coding genes. In contrast, little is known about the expression of non-coding RNAs. Here we show that HCMV encoded miRNAs are expressed de novo during latent infection of primary myeloid cells. Furthermore, we demonstrate that miR-UL148D, one of the most highly expressed viral miRNAs during latent infection, directly targets the cellular receptor ACVR1B of the activin signalling axis. Consistent with this, we observed upregulation of ACVR1B expression during latent infection with a miR-UL148D deletion virus (ΔmiR-UL148D). Importantly, we observed that monocytes latently infected with ΔmiR-UL148D are more responsive to activin A stimulation, as demonstrated by their increased secretion of IL-6. Collectively, our data indicates miR-UL148D inhibits ACVR1B expression in latently infected cells to limit proinflammatory cytokine secretion, perhaps as an immune evasion strategy or to postpone cytokine-induced reactivation until conditions are more favourable. This is the first demonstration of an HCMV miRNA function during latency in primary myeloid cells, implicating that small RNA species may contribute significantly to latent infection.

Reconstitution of CD8 T Cells Protective against Cytomegalovirus in a Mouse Model of Hematopoietic Cell Transplantation: Dynamics and Inessentiality of Epitope Immunodominance

Successful reconstitution of cytomegalovirus (CMV)-specific CD8⁺ T cells by hematopoietic cell transplantation (HCT) gives a favorable prognosis for the control of CMV reactivation and prevention of CMV disease after hematoablative therapy of hematopoietic malignancies. In the transient immunocompromised state after HCT, pre-emptive cytoimmunotherapy with viral epitope-specific effector or memory CD8⁺ T cells is a promising option to speed up antiviral control. Despite high-coding capacity of CMVs and a broad CD8⁺ T-cell response on the population level, which reflects polymorphism in major histocompatibility complex class-I (MHC-I) glycoproteins, the response in terms of quantity of CD8⁺ T cells in any individual is directed against a limited set of CMV-encoded epitopes selected for presentation by the private repertoire of MHC-I molecules. Such epitopes are known as “immunodominant” epitopes (IDEs). Besides host immunogenetics, genetic variance in CMV strains harbored as latent viruses by an individual HCT recipient can also determine the set of IDEs, which complicates a “personalized immunotherapy.” It is, therefore, an important question if IDE-specific CD8⁺ T-cell reconstitution after HCT is critical or dispensable for antiviral control. As viruses with targeted mutations of IDEs cannot be experimentally tested in HCT patients, we employed the well-established mouse model of HCT. Notably, control of murine CMV (mCMV) after HCT was comparably efficient for IDE-deletion mutant mCMV-Δ4IDE and the corresponding IDE-expressing revertant virus mCMV-Δ4IDE-rev. Thus, antigenicity-loss mutations in IDEs do not result in loss-of-function of a polyclonal CD8⁺ T-cell population. Although IDE deletion was not associated with global changes in the response to non-IDE epitopes, the collective of non-IDE-specific CD8⁺ T-cells infiltrates infected tissue and confines infection within nodular inflammatory foci. We conclude from the model, and predict also for human CMV, that there is no need to exclusively aim for IDE-specific immunoreconstitution.

Cellular Interferon Gamma and Granzyme B Responses to Cytomegalovirus-pp65 and Influenza N1 Are Positively Associated in Elderly

Morbidity and mortality in the elderly are associated with viral infections, including influenza and cytomegalovirus (CMV). With increasing age, cellular immunity gains importance in protection to influenza, but latent CMV is highly prevalent and associated with immune dysfunction. An insight into the association between immunity against influenza and CMV adds to the understanding of healthy aging. Here we first aimed to measure influenza-specific cellular immunity using granzyme B (GrzB) and interferon-gamma (IFN-γ)-ELISpot. Next, influenza-specific cellular immunity was associated with humoral and cellular CMV-specific immunity in healthy 65+ elderly. Vaccine trial participants gave additional blood samples 3 weeks after receiving a H1N1 containing vaccine. CMV serology was determined and peripheral blood mononuclear cells were stimulated with influenza N1 or CMV pp65-derived peptide pools for 7 days and rechallenged to assess antigen-specific GgrzB and IFN-γ responses using ELISpot assays. Results were compared using chi-square and correlation analysis. Eighty-three individuals (60% men, 65% CMV IgG+, age range 65-78y) participated. We found significant positive associations between IFN-γ and GrzB responses to both influenza and CMV, but also between a positive CMV serostatus and an influenza N1-specific activation marker response (p = 0.013). CMV pp65 responses were detected in CMV IgG+ individuals, but remarkably also in CMV IgG- individuals (27%). In this study, following influenza vaccination, elderly with cellular immunity against CMV were more likely to have cellular immunity against influenza vaccine N1 antigen. These findings stress the need to continue exploring the possible role of CMV in immunosenescence.

Leukocyte Immunoglobulin-Like Receptor 1-Expressing Human Natural Killer Cell Subsets Differentially Recognize Isolates of Human Cytomegalovirus through the Viral Major Histocompatibility Complex Class I Homolog UL18

Immune responses of natural killer (NK) cell are controlled by the balance between activating and inhibitory receptors, but the expression of these receptors varies between cells within an individual. Although NK cells are a component of the innate immune system, particular NK cell subsets expressing Ly49H are positively selected and increase in frequency in response to cytomegalovirus infection in mice. Recent evidence suggests that in humans certain NK subsets also have an increased frequency in the blood of human cytomegalovirus (HCMV)-infected individuals. However, whether these subsets differ in their capacity of direct control of HCMV-infected cells remains unclear. In this study, we developed a novel in vitro assay to assess whether human NK cell subsets have differential abilities to inhibit HCMV growth and dissemination. NK cells expressing or lacking NKG2C did not display any differences in controlling viral dissemination. However, when in vitro-expanded NK cells were used, cells expressing or lacking the inhibitory receptor leukocyte immunoglobulin-like receptor 1 (LIR1) were differentially able to control dissemination. Surprisingly, the ability of LIR1⁺ NK cells to control virus spread differed between HCMV viral strains, and this phenomenon was dependent on amino acid sequences within the viral ligand UL18. Together, the results here outline an in vitro technique to compare the long-term immune responses of different human NK cell subsets and suggest, for the first time, that phenotypically defined human NK cell subsets may differentially recognize HCMV infections.

IMPORTANCE HCMV infection is ubiquitous in most populations; it is not cleared by the host after primary infection but persists for life. The innate and adaptive immune systems control the spread of virus, for which natural killer (NK) cells play a pivotal role. NK cells can respond to HCMV infection by rapid, short-term, nonspecific innate responses, but evidence from murine studies suggested that NK cells may display long-term, memory-like responses to murine cytomegalovirus infection. In this study, we developed a new assay that examines human NK cell subsets that have been suggested to play a long-term memory-like response to HCMV infection. We show that changes in an HCMV viral protein that interacts with an NK cell receptor can change the ability of NK cell subsets to control HCMV while the acquisition of another receptor has no effect on virus control.

Maturation and Mip-1β Production of Cytomegalovirus-Specific T Cell Responses in Tanzanian Children, Adolescents and Adults: Impact by HIV and Mycobacterium tuberculosis Co-Infections

It is well accepted that aging and HIV infection are associated with quantitative and functional changes of CMV-specific T cell responses. We studied here the expression of Mip-1β and the T cell maturation marker CD27 within CMVpp65-specific CD4(+) and CD8(+) T cells in relation to age, HIV and active Tuberculosis (TB) co-infection in a cohort of Tanzanian volunteers (≤ 16 years of age, n = 108 and ≥ 18 years, n = 79). Independent of HIV co-infection, IFNγ(+) CMVpp65-specific CD4(+) T cell frequencies increased with age. In adults, HIV co-infection further increased the frequencies of these cells. A high capacity for Mip-1β production together with a CD27(low) phenotype was characteristic for these cells in children and adults. Interestingly, in addition to HIV co-infection active TB disease was linked to further down regulation of CD27 and increased capacity of Mip-1β production in CMVpp65-specific CD4+ T cells. These phenotypic and functional changes of CMVpp65-specific CD4 T cells observed during HIV infection and active TB could be associated with increased CMV reactivation rates.

How understanding immunology contributes to managing CMV disease in immunosuppressed patients: now and in future

Several decades of research on human cytomegalovirus (HCMV) and the principal mammalian cytomegaloviruses which to varying degrees act as models of HCMV infection, particularly murine, guinea pig and rhesus CMV, have led to the recognition of the CMVs as interesting models of persistent infection with a large and complex DNA virus, which have been highly informative of the immunology and molecular pathogenesis of the virus-host relationship in the normal host. However, it is appropriate to ask how this relative wealth of knowledge has influenced the understanding and management of clinical disease due to HCMV. This article considers the immunology of cytomegalovirus in the normal human host, and the interrelated issue of the sites of HCMV latency and mechanisms of reactivation in the myeloid cell lineage, and in related in vitro model systems. The way in which this site of latency conditions the immune response, and emerging information on the special features of the adaptive immune response to HCMV during latency are also considered. Examples of HCMV disease associated with acquired immunosuppression, principally in the context of transplantation, but also as a consequence of HIV/AIDS and immune reconstitution inflammatory syndrome, are then discussed, with a particular emphasis on how understanding the immunology of persistent infection may contribute to managing CMV disease now and in future.

The immunological underpinnings of vaccinations to prevent cytomegalovirus disease

A universal cytomegalovirus (CMV) vaccination promises to reduce the burden of the developmental damage that afflicts up to 0.5% of live births worldwide. An effective vaccination that prevents transplacental transmission would reduce CMV congenital disease and CMV-associated still births and leave populations less susceptible to opportunistic CMV disease. Thus, a vaccination against this virus has long been recognized for the potential of enormous health-care savings because congenital damage is life-long and existing anti-viral options are limited. Vaccine researchers, industry leaders, and regulatory representatives have discussed the challenges posed by clinical efficacy trials that would lead to a universal CMV vaccine, reviewing the links between infection and disease, and identifying settings where disrupting viral transmission might provide a surrogate endpoint for disease prevention. Reducing the complexity of such trials would facilitate vaccine development. Children and adolescents are the targets for universal vaccination, with the expectation of protecting the offspring of immunized women. Given that a majority of females worldwide experience CMV infection during childhood, a universal vaccine must boost natural immunity and reduce transmission due to reactivation and re-infection as well as primary infection during pregnancy. Although current vaccine strategies recognize the value of humoral and cellular immunity, the precise mechanisms that act at the placental interface remain elusive. Immunity resulting from natural infection appears to limit rather than prevent reactivation of latent viruses and susceptibility to re-infection, leaving a challenge for universal vaccination to improve upon natural immunity levels. Despite these hurdles, early phase clinical trials have achieved primary end points in CMV seronegative subjects. Efficacy studies must be expanded to mixed populations of CMV-naive and naturally infected subjects to understand the overall efficacy and potential. Together with CMV vaccine candidates currently in clinical development, additional promising preclinical strategies continue to come forward; however, these face limitations due to the insufficient understanding of host defense mechanisms that prevent transmission, as well as the age-old challenges of reaching the appropriate threshold of immunogenicity, efficacy, durability and potency. This review focuses on the current understanding of natural and CMV vaccine-induced protective immunity.

Aging and cytomegalovirus infection differentially and jointly affect distinct circulating T cell subsets in humans

The impact of intrinsic aging upon human peripheral blood T cell subsets remains incompletely quantified and understood. This impact must be distinguished from the influence of latent persistent microorganisms, particularly CMV, which has been associated with age-related changes in the T cell pool. In a cross-sectional cohort of 152 CMV-negative individuals, aged 21-101 y, we found that aging correlated strictly to an absolute loss of naive CD8, but not CD4, T cells but, contrary to many reports, did not lead to an increase in memory T cell numbers. The loss of naive CD8 T cells was not altered by CMV in 239 subjects (range 21-96 y), but the decline in CD4(+) naive cells showed significance in CMV(+) individuals. These individuals also exhibited an absolute increase in the effector/effector memory CD4(+) and CD8(+) cells with age. That increase was seen mainly, if not exclusively, in older subjects with elevated anti-CMV Ab titers, suggesting that efficacy of viral control over time may determine the magnitude of CMV impact upon T cell memory, and perhaps upon immune defense. These findings provide important new insights into the age-related changes in the peripheral blood pool of older adults, demonstrating that aging and CMV exert both distinct and joint influence upon blood T cell homeostasis in humans.

Alloreactivity of virus-specific T cells: possible implication of graft-versus-host disease and graft-versus-leukemia effects

Immune reconstitution of functional virus-specific T cells after allogeneic hematopoietic stem cell transplantation (HSCT) has been intensively investigated. However, the possible role of crossreactivity of these virus-specific T cells against allogeneic targets is still unclear. Theoretically, as in the field of organ transplantation, virus-specific T cells possess crossreactivity potential after allogeneic HSCT. Such crossreactivity is assumed to play a role in graft-versus-host disease and graft-versus-leukemia effects. In this article, we aim to give a comprehensive overview of current understanding about crossreactivity of virus-specific T cells.

Age-associated increase of low-avidity cytomegalovirus-specific CD8+ T cells that re-express CD45RA

The mechanisms regulating memory CD8(+) T cell function and homeostasis during aging are unclear. CD8(+) effector memory T cells that re-express CD45RA increase considerably in older humans and both aging and persistent CMV infection are independent factors in this process. We used MHC class I tetrameric complexes that were mutated in the CD8 binding domain to identify CMV-specific CD8(+) T cells with high Ag-binding avidity. In individuals who were HLA-A*0201, CD8(+) T cells that expressed CD45RA and were specific for the pp65 protein (NLVPMVATV epitope) had lower avidity than those that expressed CD45RO and demonstrated decreased cytokine secretion and cytolytic potential after specific activation. Furthermore, low avidity NLVPMVATV-specific CD8(+) T cells were significantly increased in older individuals. The stimulation of blood leukocytes with CMV lysate induced high levels of IFN-α that in turn induced IL-15 production. Moreover, the addition of IL-15 to CD45RA(-)CD45RO(+) CMV-specific CD8(+) T cells induced CD45RA expression while Ag activated cells remained CD45RO(+). This raises the possibility that non-specific cytokine-driven accumulation of CMV-specific CD8(+)CD45RA(+) T cells with lower Ag-binding avidity may exacerbate the effects of viral reactivation on skewing the T cell repertoire in CMV-infected individuals during aging.

Measuring T-cell responses against LCV and CMV in cynomolgus macaques using ELISPOT: potential application to non-clinical testing of immunomodulatory therapeutics

A number of immunomodulatory therapeutics increase the risk of disease associated with latent herpesviruses such as cytomegalovirus (CMV) and Epstein-Barr virus (EBV), a member of the lymphocryptovirus (LCV) family that infects humans. The diseases associated with loss of immunity to these viruses can have major impacts on patients as well as on the commercial viability of the immunomodulatory therapeutics. In an effort to develop non-clinical methods for measuring effects on anti-viral immunity, we have developed an interferon (IFN)-γ enzyme-linked immunosorbent spot (ELISPOT) assay to quantify the number of CMV or LCV-reactive T-cells in peripheral blood of cynomolgus macaques. After optimization of various parameters, the IFN-γ ELISPOT assay was characterized for specificity, intra-assay, monkey-to-monkey, and longitudinal variability and sensitivity to immunosuppression. The results show that nearly all animals have detectable responses against both CMV and LCV and responses were derived from T-cells specific to the virus of interest. Analyses of variability show assay reproducibility (≤23% CV), and that variability over time in anti-viral responses in individual animals (larger for LCV than for CMV) was ∼2-fold in most animals over a 3-month time period, which is predicted to allow for detection of drug-induced changes when using group sizes typical of non-clinical studies. In addition, the IFN-γ ELISPOT assay was capable of detecting decreases in the numbers of CMV and LCV reactive T-cells induced by immunosuppressive drugs in vitro. This assay may allow for non-clinical assessment of the effects of immunomodulatory therapeutics on anti-viral T-cell immunity in monkeys, and may help determine if therapeutics increase the risk of reactivating latent viral infections.

The myeloid transcription factor GATA-2 regulates the viral UL144 gene during human cytomegalovirus latency in an isolate-specific manner

It is generally accepted that, following primary infection, human cytomegalovirus (HCMV) establishes lifelong latency in CD34(+) progenitor cells and other derivative cells of the myeloid lineage. In this study, we show that the viral UL144 gene is expressed during latent infection in two cell types of the myeloid lineage, CD34(+) and CD14(+) monocytes, and that the UL144 protein is functional in latently infected monocytes. However, this latency-associated expression of UL144 occurs only in certain isolates of HCMV and depends on the presence of functional GATA-2 transcription factor binding sites in the UL144 promoter, in contrast to the viral latency-associated gene LUNA, which we also show is regulated by GATA-2 but expressed uniformly during latent infection independent of the virus isolate. Taken together, these data suggest that the HCMV latency-associated transcriptome may be virus isolate specific and dependent on the repertoire of transcription factor binding sites in the promoters of latency-associated genes.

Evolution of CD8+ T cell responses after acute PARV4 infection

PARV4 is a small DNA human virus that is strongly associated with hepatitis C virus (HCV) and HIV infections. The immunologic control of acute PARV4 infection has not been previously described. We define the acute onset of PARV4 infection and the characteristics of the acute-phase and memory immune responses to PARV4 in a group of HCV- and HIV-negative, active intravenous drug users. Ninety-eight individuals at risk of blood-borne infections were tested for PARV4 IgG. Gamma interferon enzyme-linked immunosorbent spot assays, intracellular cytokine staining, and a tetrameric HLA-A2-peptide complex were used to define the T cell populations responding to PARV4 peptides in those individuals who acquired infection during the study. Thirty-five individuals were found to be PARV4 seropositive at the end of the study, eight of whose baseline samples were found to be seronegative. Persistent and functional T cell responses were detected in the acute infection phase. These responses had an active, mature, and cytotoxic phenotype and were maintained several years after infection. Thus, PARV4 infection is common in individuals exposed to blood-borne infections, independent of their HCV or HIV status. Since PARV4 elicits strong, broad, and persistent T cell responses, understanding of the processes responsible may prove useful for future vaccine design.

Nucleocytoplasmic shuttling and CRM1-dependent MHC class I peptide presentation of human cytomegalovirus pp65

The phosphoprotein 65 (pp65) of human cytomegalovirus is a prominent target of the antiviral CD8 T lymphocyte response. This study focused on investigating the properties of pp65 that render it a privileged antigen. It was found that pp65 was metabolically stable. The tegument protein was introduced into MHC class I presentation following its delivery via non-replicating dense bodies. No ubiquitination was found on particle-associated pp65. Proof was obtained that pp65 was a nucleocytoplasmic shuttle protein, using heterokaryon analyses. Based on this finding, inhibition experiments showed that presentation of particle-derived pp65 by HLA-A2 was sensitive to the impairment of the CRM1-mediated nuclear export pathway. The data support the idea that particle-derived pp65 can serve as a nuclear reservoir for proteasomal processing and MHC class I presentation, following its CRM1-dependent nuclear export. The presentation of pp65-derived peptides was also impaired by CRM1-inhibition following de novo synthesis of the tegument protein. However, pp65 protein levels were also reduced when blocking CRM1-mediated export after transient expression. This indicated that pp65 expression rather than direct interference with its own nuclear export was responsible for its reduced presentation in this case. The functionality of CRM1-mediated nuclear export is thus important for the presentation of pp65-derived peptides in the context of MHC class I on organ cells, both after exogenous uptake and after de novo synthesis of the tegument protein, but different mechanisms may account for either case.

Deep sequencing of antiviral T-cell responses to HCMV and EBV in humans reveals a stable repertoire that is maintained for many years

CD8⁺ T-cell responses against latent viruses can cover considerable portions of the CD8⁺ T-cell compartment for many decades, yet their initiation and maintenance remains poorly characterized in humans. A key question is whether the clonal repertoire that is raised during the initial antiviral response can be maintained over these long periods. To investigate this we combined next-generation sequencing of the T-cell receptor repertoire with tetramer-sorting to identify, quantify and longitudinally follow virus-specific clones within the CD8⁺ T-cell compartment. Using this approach we studied primary infections of human cytomegalovirus (hCMV) and Epstein Barr virus (EBV) in renal transplant recipients. For both viruses we found that nearly all virus-specific CD8⁺ T-cell clones that appeared during the early phase of infection were maintained at high frequencies during the 5-year follow-up and hardly any new anti-viral clones appeared. Both in transplant recipients and in healthy carriers the clones specific for these latent viruses were highly dominant within the CD8⁺ T-cell receptor Vβ repertoire. These findings suggest that the initial antiviral response in humans is maintained in a stable fashion without signs of contraction or changes of the clonal repertoire.

Several viruses have found ways to evade the human immune system and cause latent infections. Examples include HIV and herpes-viruses. Most humans carry these herpes-viruses. The human immune system mounts continuous responses against these viruses to prevent them from causing disease. If this balance is disturbed, these viruses can cause extensive pathology. We do not know how the immune response against these viruses evolves over time. Understanding this response might help to understand why the immune system does not clear these viruses and might help in preventive and therapeutic strategies. Here we used a new technology that allowed us to track virus specific immune cells (CD8⁺ T cells) over time in a quantitative manner. When we used this technology to study the evolution of latent responses against herpes-viruses (from infection until 5 years later) we found that immune responses were very rigid and did not evolve over time. Collectively our data shows that – for these herpes-viruses – the initial immune response is maintained despite the fact that this does not result in clearance of the virus. Therefore, if a virus survives the initial response, it will not be cleared in the future. This is an important consideration in understanding latent infection and for vaccination-design.

Human cytomegalovirus latency alters the cellular secretome, inducing cluster of differentiation (CD)4+ T-cell migration and suppression of effector function

After primary infection, human cytomegalovirus (HCMV) persists as a life-long latent infection, with host immunosuppression often resulting in clinical reactivation. During lytic infection, major changes in the expression of secreted cellular proteins (the secretome) occur that have profound effects on host-cell interactions, particularly at the level of the host immune response. In contrast, little is known about changes in the secretome that accompany latent infection, yet this is likely to be of major importance for the life-long carriage of this persistent human pathogen in the face of constant immunosurveillance. We have analyzed the secretome of cells carrying latent HCMV and have identified changes in several secreted cellular proteins known to be involved in regulation of the immune response and chemoattraction. Here, we show that a latency-associated increase in CC chemokine ligand (CCL)8 results in the recruitment of cluster of differentiation (CD)4(+) T cells to supernatants from latently infected CD34(+) cells but that these latent supernatants, also rich in immunosuppressive factors, inhibit cytokine secretion and cytotoxicity of HCMV-specific T-helper (Th)1 CD4(+) T cells. These results identify a strategy by which sites of latent HCMV can firstly recruit CD4(+) T cells and then inhibit their antiviral effector functions, thereby aiding the maintenance of latent infection in the face of the host immune response.

Human CD4+ T cell response to human herpesvirus 6

Following primary infection, human herpesvirus 6 (HHV-6) establishes a persistent infection for life. HHV-6 reactivation has been associated with transplant rejection, delayed engraftment, encephalitis, muscular dystrophy, and drug-induced hypersensitivity syndrome. The poor understanding of the targets and outcome of the cellular immune response to HHV-6 makes it difficult to outline the role of HHV-6 in human disease. To fill in this gap, we characterized CD4 T cell responses to HHV-6 using peripheral blood mononuclear cell (PBMC) and T cell lines generated from healthy donors. CD4(+) T cells responding to HHV-6 in peripheral blood were observed at frequencies below 0.1% of total T cells but could be expanded easily in vitro. Analysis of cytokines in supernatants of PBMC and T cell cultures challenged with HHV-6 preparations indicated that gamma interferon (IFN-γ) and interleukin-10 (IL-10) were appropriate markers of the HHV-6 cellular response. Eleven CD4(+) T cell epitopes, all but one derived from abundant virion components, were identified. The response was highly cross-reactive between HHV-6A and HHV-6B variants. Seven of the CD4(+) T cell epitopes do not share significant homologies with other known human pathogens, including the closely related human viruses human herpesvirus 7 (HHV-7) and human cytomegalovirus (HCMV). Major histocompatibility complex (MHC) tetramers generated with these epitopes were able to detect HHV-6-specific T cell populations. These findings provide a window into the immune response to HHV-6 and provide a basis for tracking HHV-6 cellular immune responses.

Memory T cell inflation: understanding cause and effect

Typically, during viral infections, T cells encounter antigen, undergo proliferative expansion and ultimately contract into a pool of memory cells. However, after infection with cytomegalovirus, a ubiquitous β-herpesvirus, T cell populations specific for certain epitopes do not contract but instead are maintained and/or accumulate at high frequencies with a characteristic effector-memory phenotype. This feature has also been noted after other infections, for example, by parvoviruses. We discuss this so-called memory T cell inflation and the factors involved in this phenomenon. Also, we consider the potential therapeutic use of memory T cell inflation as a vaccine strategy and the associated implications for immune senescence.

Fish T cells: recent advances through genomics

This brief review is intended to provide a concise overview of the current literature concerning T cells, advances in identifying distinct T cell functional subsets, and in distinguishing effector cells from memory cells. We compare and contrast a wealth of recent progress made in T cell immunology of teleost, elasmobranch, and agnathan fish, to knowledge derived from mammalian T cell studies. From genome studies, fish clearly have most components associated with T cell function and we can speculate on the presence of putative T cell subsets, and the ability to detect their differentiation to form memory cells. Some recombinant proteins for T cell associated cytokines and antibodies for T cell surface receptors have been generated that will facilitate studying the functional roles of teleost T cells during immune responses. Although there is still a long way to go, major advances have occurred in recent years for investigating T cell responses, thus phenotypic and functional characterization is on the near horizon.

Significant association of multiple human cytomegalovirus genomic Loci with glioblastoma multiforme samples

Viruses are appreciated as etiological agents of certain human tumors, but the number of different cancer types induced or exacerbated by viral infections is unknown. Glioblastoma multiforme (GBM)/astrocytoma grade IV is a malignant and lethal brain cancer of unknown origin. Over the past decade, several studies have searched for the presence of a prominent herpesvirus, human cytomegalovirus (HCMV), in GBM samples. While some have detected HCMV DNA, RNA, and proteins in GBM tissues, others have not. Therefore, any purported association of HCMV with GBM remains controversial. In most of the previous studies, only one or a select few viral targets were analyzed. Thus, it remains unclear the extent to which the entire viral genome was present when detected. Here we report the results of a survey of GBM specimens for as many as 20 different regions of the HCMV genome. Our findings indicate that multiple HCMV loci are statistically more likely to be found in GBM samples than in other brain tumors or epileptic brain specimens and that the viral genome was more often detected in frozen samples than in paraffin-embedded archival tissue samples. Finally, our experimental results indicate that cellular genomes substantially outnumber viral genomes in HCMV-positive GBM specimens, likely indicating that only a minority of the cells found in such samples harbor viral DNA. These data argue for the association of HCMV with GBM, defining the virus as oncoaccessory. Furthermore, they imply that, were HCMV to enhance the growth or survival of a tumor (i.e., if it is oncomodulatory), it would likely do so through mechanisms distinct from classic tumor viruses that express transforming viral oncoproteins in the overwhelming majority of tumor cells.

Expansion of T cells targeting multiple antigens of cytomegalovirus, Epstein-Barr virus and adenovirus to provide broad antiviral specificity after stem cell transplantation

BACKGROUND AIMS

Hematopoietic stem cell transplant (HSCT) is the treatment of choice for a proportion of patients with hematologic malignancies as well as for non-malignant diseases. However, viral infections, particularly Epstein-Barr virus (EBV), cytomegalovirus (CMV) and adenovirus (Ad), remain problematic after transplant despite the use of antiviral drugs. We have shown that cytotoxic T lymphocytes (CTL) generated against CMV-pp65, EBV and Ad antigens in a single culture are capable of controlling infections with all three viruses after HSCT. Although pp65-specific CTL have proved efficacious for the control of CMV infection, several reports highlight the importance of targeting additional CMV antigens.

METHODS

To expand multivirus-specific T cells with activity against both CMV-pp65 and CMV-IE-1, peripheral blood mononuclear cells (PBMC) were transduced with the adenoviral vector (Ad5f35-IE-1-I-pp65). After 9-12 days the CTL were restimulated with autologous EBV-transformed B cells transduced with the same Ad vector.

RESULTS

After 18 days in culture nine CTL lines expanded from less than 1.5 × 10(7) PBMC to a mean of 6.1 × 10(7) T cells that recognized CMV antigens pp65 [median 273 spot-forming cells (SFC), range 47-995] and IE-1 (median 154 SFC, range 11-505), the Ad antigens hexon (median 153 SFC, range 26-465) and penton (median 37 SFC, range 1-353), as well as EBV lymphoblastoid cell lines (median 55 SFC, range 9-301). Importantly, the T cells recognized at least two antigens per virus and lysed virus peptide-pulsed targets.

CONCLUSIONS

CTL that target at least two antigens each of CMV, EBV and Ad should have clinical benefit with broad coverage of all three viruses and enhanced control of CMV infections compared with current protocols.

Bronchial secretory immunoglobulin a deficiency correlates with airway inflammation and progression of chronic obstructive pulmonary disease

RATIONALE

Although airway inflammation can persist for years after smoking cessation in patients with chronic obstructive pulmonary disease (COPD), the mechanisms of persistent inflammation are largely unknown.

OBJECTIVES

We investigated relationships between bronchial epithelial remodeling, polymeric immunoglobulin receptor (pIgR) expression, secretory IgA (SIgA), airway inflammation, and mural remodeling in COPD.

METHODS

Lung tissue specimens and bronchoalveolar lavage were obtained from lifetime nonsmokers and former smokers with or without COPD. Epithelial structural changes were quantified by morphometric analysis. Expression of pIgR was determined by immunostaining and real-time polymerase chain reaction. Immunohistochemistry was performed for IgA, CD4 and CD8 lymphocytes, and cytomegalovirus and Epstein-Barr virus antigens. Total IgA and SIgA were measured by ELISA and IgA transcytosis was studied using cultured human bronchial epithelial cells.

MEASUREMENTS AND MAIN RESULTS

Areas of bronchial mucosa covered by normal pseudostratified ciliated epithelium were characterized by pIgR expression with SIgA present on the mucosal surface. In contrast, areas of bronchial epithelial remodeling had reduced pIgR expression, localized SIgA deficiency, and increased CD4(+) and CD8(+) lymphocyte infiltration. In small airways (<2 mm), these changes were associated with presence of herpesvirus antigens, airway wall remodeling, and airflow limitation in patients with COPD. Patients with COPD had reduced SIgA in bronchoalveolar lavage. Air-liquid interface epithelial cell cultures revealed that complete epithelial differentiation was required for normal pIgR expression and IgA transcytosis.

CONCLUSIONS

Our findings indicate that epithelial structural abnormalities lead to localized SIgA deficiency in COPD airways. Impaired mucosal immunity may contribute to persistent airway inflammation and progressive airway remodeling in COPD.

Increases in human papillomavirus detection during early HIV infection among women in Zimbabwe

BACKGROUND

Individuals who acquire human immunodeficiency virus (HIV) may experience an immediate disruption of genital tract immunity, altering the ability to mount a local and effective immune response. This study examined the impact of early HIV infection on new detection of human papillomavirus (HPV).

METHODS

One hundred fifty-five Zimbabwean women with observation periods before and after HIV acquisition and 486 HIV-uninfected women were selected from a cohort study evaluating hormonal contraceptive use and risk of HIV acquisition. Study visits occurred at 3-month intervals. Cervical swab samples available from up to 6 months before, at, and up to 6 months after the visit when HIV was first detected were typed for 37 HPV genotypes or subtypes.

RESULTS

We observed ∼5-fold higher odds of multiple (≥2) new HPV detections only after HIV acquisition, relative to HIV-negative women after adjusting for sexual behavior and concurrent genital tract infections. We also observed ∼2.5-fold higher odds of single new HPV detections at visits before and after HIV acquisition, relative to HIV-uninfected women in multivariable models.

CONCLUSIONS

These findings suggest that HIV infection has an immediate impact on genital tract immunity, as evidenced by the high risk of multiple new HPV detections immediately after HIV acquisition.

Altered T cell memory and effector cell development in chronic lymphatic filarial infection that is independent of persistent parasite antigen

Chronic lymphatic filarial (LF) infection is associated with suppression of parasite-specific T cell responses that persist even following elimination of infection. While several mechanisms have been implicated in mediating this T cell specific downregulation, a role for alterations in the homeostasis of T effector and memory cell populations has not been explored. Using multiparameter flow cytometry, we investigated the role of persistent filarial infection on the maintenance of T cell memory in patients from the filarial-endemic Cook Islands. Compared to filarial-uninfected endemic normals (EN), microfilaria (mf) positive infected patients (Inf) had a reduced CD4 central memory (T_CM) compartment. In addition, Inf patients tended to have more effector memory cells (T_EM) and fewer effector cells (T_EFF) than did ENs giving significantly smaller T_EFF ∶ T_EM ratios. These contracted T_CM and T_EFF populations were still evident in patients previously mf+ who had cleared their infection (CLInf). Moreover, the density of IL-7Rα, necessary for T memory cell maintenance (but decreased in T effector cells), was significantly higher on memory cells of Inf and CLInf patients, although there was no evidence for decreased IL-7 or increased soluble IL7-Rα, both possible mechanisms for signaling defects in memory cells. However, effector cells that were present in Inf and CLInf patients had lower percentages of HLA-DR suggesting impaired function. These changes in T cell populations appear to reflect chronicity of infection, as filarial-infected children, despite the presence of active infection, did not show alterations in the frequencies of these T cell phenotypes. These data indicate that filarial-infected patients have contracted T_CM compartments and a defect in effector cell development, defects that persist even following clearance of infection. The fact that these global changes in memory and effector cell compartments do not yet occur in infected children makes early treatment of LF even more crucial.

Experimental human cytomegalovirus latency in CD14+ monocytes

CD14(+) monocytes are a reservoir for latent human cytomegalovirus, and virus replication is reactivated during their differentiation to macrophages or dendritic cells. It has not been clear whether the virus can establish latency upon direct infection of monocytes or whether it must first become quiescent in a progenitor cell that subsequently differentiates to generate a monocyte. We report that infection of primary human monocytes with a clinical strain of human cytomegalovirus exhibits the hallmarks of latency. We established conditions for culturing monocytes that prevent differentiation for at least 25 d, as evidenced by cell surface marker expression. Infection of these monocytes with the FIX clinical strain resulted in transient accumulation of many viral lytic RNAs and sustained expression of four previously described latency-associated transcripts. The amount of viral DNA remained constant after infection, and cell surface and total HLA-DR proteins were substantially reduced on a continuing basis after infection. When treated with cytokine mixtures that stimulate differentiation to a macrophage or dendritic cell phenotype, infected monocytes reactivated virus replication and produced infectious progeny. Treatment of infected monocytes with IL-6 alone also was sufficient for reactivation, and the particles produced after exposure to this cytokine were about fivefold more infectious than virions produced by other treatments. We propose that in vivo microenvironments influence not only the efficiency of reactivation but also the infectivity of the virions produced from latently infected monocytes.

Oncomodulation by human cytomegalovirus: novel clinical findings open new roads

The question whether human cytomegalovirus may affect cancer diseases has been discussed (very controversially) for decades. There are convinced believers and strict opponents of the idea that HCMV might be able to play a role in the course of cancer diseases. In parallel, the number of published reports on the topic is growing. Recently published and presented (Ranganathan P, Clark P, Kuo JS, Salamat S, Kalejta RF. A Survey of Human Cytomegalovirus Genomic Loci Present in Glioblastoma Multiforme Tissue Samples. 35th Annual International Herpes Workshop, Salt Lake City, 2010) data on HCMV detection in glioblastoma tissues and colocalisation of HCMV proteins with cellular proteins known to be relevant for glioblastoma progression motivated us to recapitulate the current state of evidence.

Human cytomegalovirus-specific CD8(+) T-cell expansions contain long-lived cells that retain functional capacity in both young and elderly subjects

The immune response to human cytomegalovirus (HCMV) infection is characterized by the accumulation of HCMV-specific CD8(+) T cells, particularly in the elderly; such expansions may impair immune responses to other pathogens. We investigated mechanisms underlying HCMV-specific expansions in 12 young and 21 old healthy subjects (although not all analyses were performed on all subjects). Phenotypically, HCMV-pentamer(+) CD8(+) T cells were characterized by marked Vβ restriction, advanced differentiation (being predominantly CD27(-) CD28(-) ), and variable CD45RO/RA expression. Although more common and larger in older subjects, expansions had similar phenotypic characteristics in the young. In one old subject, repeated studies demonstrated stability in size and Vβ distribution of pentamer(+) populations over 6 years. We tested whether HCMV-specific CD8(+) T-cell expansions arose from accelerated proliferation or extended lifespan by in vivo labelling with deuterated glucose and ex vivo Ki-67 expression. Uptake of deuterated glucose was lower in pentamer(+) cells than in pentamer(-) CD8(+) CD45RO(+) or CD8(+) CD45RA(+) cells in three old subjects, consistent with reduced proliferation and extended lifespan. Similarly Ki-67 labelling showed no evidence for increased proliferation in HCMV-specific CD8(+) expansions in older subjects, although pentamer(-) CD45RA(+) cells from young donors expressed very little Ki-67. We investigated Bcl-2 and CD95 as possible anti-apoptotic mediators, but neither was associated with pentamer-positivity. To investigate whether expansion represents a compensatory response to impaired functionality, we performed two tests of functionality, peptide-stimulated proliferation and CD107 expression; both were intact in pentamer(+) cells. Our data suggest that HCMV-specific CD8(+) expansions in older subjects accumulate by extended lifespan, rather than accelerated proliferation.