Human cytomegalovirus particles directly suppress CD4 T-lymphocyte activation and proliferation

Are CMV and SARS-CoV-2 Infections Mutual Risk Factors in Kidney Transplant Recipients?

Throughout the years, much progress has been made in the field of renal transplantation; however, along with new developments, new problems have arisen. While transplantation is the optimal choice in patients suffering from end-stage renal disease, it is always connected to certain commonly associated risks, in particular those caused by opportunistic infections. One such risk includes the reactivation of cytomegalovirus (CMV), an issue commonly affecting all kinds of transplant recipients. Similarly, with the rise of the ever-evolving global SARS-CoV-2 pandemic, patients must be constantly monitored for any respiratory symptoms, and observed closely under the care of their attending physician. Treating these patients has become extremely difficult due to limitations caused by COVID-19 protocols (for instance, the reduction of immunosuppression dosages and the avoidance of lymphocyte-depleting induction therapy) and the lack of knowledge surrounding this relatively new and worsening risk factor. In order to give patients optimal care, these arising problems need to be studied and addressed.

Specific Immunity to Cytomegalovirus in Pediatric Cardiac Transplantation

BACKGROUND

Cytomegalovirus (CMV) infection is implicated in endothelial dysfunction and graft damage after pediatric heart transplantation. CMV-specific immune responses are thought to be necessary for CMV viral control but there is little data in pediatric heart transplantation.

METHODS

We studied 28 consecutive pediatric heart transplant recipients for 1 year posttransplant. CMV T-cell expressing IFN-γ, TNF-α, and IL-2 in response to ex vivo stimulation with CMV lysates or peptides were measured. Circulating cytokines were measured in plasma. Generalized Additive Models were applied to the data to model changes of cell population dynamics over time.

RESULTS

CMV-specific T cell-mediated responses were impaired in the first 8 weeks posttransplant. During this period, 25% of patients had CMV viremia, of which those with VLs of 10 000 or more CMV deoxyribonucleic acid copies/mL were given ganciclovir. In this group, the frequency of CD4+ and CD8+ T cells producing IFN-γ and the CD8+CD57+ granzyme B+ T-cell population increased at 12 to 24 weeks and remained elevated for the duration of the study.

CONCLUSIONS

We have shown that CMV viremia is associated with CMV-specific immune responses and increased CD8+CD57+ granzyme B+ cells at 1 year posttransplant; however, early responses were not predictive of impending CMV viremia. It remains to be seen if the early CMV immune response detected is associated with endothelial and allograft damage, in light of previous studies demonstrating increased vasculopathy in pediatric patients with CMV viremia.

Signatures of T and B Cell Development, Functional Responses and PD-1 Upregulation After HCMV Latent Infections and Reactivations in Nod.Rag.Gamma Mice Humanized With Cord Blood CD34+ Cells

Human cytomegalovirus (HCMV) latency is typically harmless but reactivation can be largely detrimental to immune compromised hosts. We modeled latency and reactivation using a traceable HCMV laboratory strain expressing the Gaussia luciferase reporter gene (HCMV/GLuc) in order to interrogate the viral modulatory effects on the human adaptive immunity. Humanized mice with long-term (more than 17 weeks) steady human T and B cell immune reconstitutions were infected with HCMV/GLuc and 7 weeks later were further treated with granulocyte-colony stimulating factor (G-CSF) to induce viral reactivations. Whole body bio-luminescence imaging analyses clearly differentiated mice with latent viral infections vs. reactivations. Foci of vigorous viral reactivations were detectable in liver, lymph nodes and salivary glands. The number of viral genome copies in various tissues increased upon reactivations and were detectable in sorted human CD14⁺, CD169⁺, and CD34⁺ cells. Compared with non-infected controls, mice after infections and reactivations showed higher thymopoiesis, systemic expansion of Th, CTL, Treg, and Tfh cells and functional antiviral T cell responses. Latent infections promoted vast development of memory CD4⁺ T cells while reactivations triggered a shift toward effector T cells expressing PD-1. Further, reactivations prompted a marked development of B cells, maturation of IgG⁺ plasma cells, and HCMV-specific antibody responses. Multivariate statistical methods were employed using T and B cell immune phenotypic profiles obtained with cells from several tissues of individual mice. The data was used to identify combinations of markers that could predict an HCMV infection vs. reactivation status. In spleen, but not in lymph nodes, higher frequencies of effector CD4⁺ T cells expressing PD-1 were among the factors most suited to distinguish HCMV reactivations from infections. These results suggest a shift from a T cell dominated immune response during latent infections toward an exhausted T cell phenotype and active humoral immune response upon reactivations. In sum, this novel in vivo humanized model combined with advanced analyses highlights a dynamic system clearly specifying the immunological spatial signatures of HCMV latency and reactivations. These signatures can be merged as predictive biomarker clusters that can be applied in the clinical translation of new therapies for the control of HCMV reactivation.

Methicillin-resistant Staphylococcus aureus bacteremia among liver transplant recipients: epidemiology and associated risk factors for morbidity and mortality

Bacteremia due to Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA), complicates the clinical course of liver transplantation and is associated with high morbidity and mortality. Intravascular catheters had been reported to be the most frequent source of MRSA bacteremia. Among bacteremic liver recipients, 26.3%-100% of S. aureus were MRSA. Previous studies identified pre-transplant and post-transplant acquired S. aureus carriage, greater severity of liver disease, hepatocellular carcinoma and infection with immuno-modulatory viruses as predictors of S. aureus bacteremia in liver recipients. MRSA bacteremia accompanied by pneumonia and abdominal infections was related to mortality. Vancomycin, as well as daptomycin, is a first-line antibiotic for MRSA bacteremia. The purpose of this review is to better understand the characteristics of MRSA bacteremia by summarizing the epidemiology and antimicrobial resistance of S. aureus, the primary source, and related risk factors for morbidity and mortality of MRSA bacteremia. We have also explored the diagnostic, therapeutic and preventive measures for MRSA bacteremia to improve the outcomes of liver recipients.

Research status of pulmonary infection after renal transplantation

Recipients with a low immunity are under a high risk of infection due to the extensive use of immunosuppressive drugs after renal transplantation. Pulmonary infection after renal transplantation is a prevalent postoperative complication characterized by a wide range of pathogens and high mortality. If the disease cannot be diagnosed in time, then the therapeutic effect will not be effective. This article reviews susceptible factors, high onset time, common pathogens, clinical manifestations, and therapy of pulmonary infection after renal transplantation to provide reference for disease prevention and treatment.

Clinical and immunological assessment of therapeutic immunization with a subunit vaccine for recurrent ocular canine herpesvirus-1 infection in dogs

Latent canine herpesvirus-1 (CHV-1) infections are common in domestic dogs and reactivation of latent virus may be associated with recurrent ocular disease. The objectives of the present study were to evaluate the ability of a subunit CHV-1 vaccine to stimulate peripheral CHV-1 specific immunity and prevent recurrent CHV-1 ocular disease and viral shedding. Mature dogs with experimentally-induced latent CHV-1 infection received a 2-dose CHV-1 vaccine series. Recurrent ocular CHV-1 infection was induced by corticosteroid administration in the prevaccinal, short-term postvaccinal (2 weeks post-vaccination), and long-term postvacccinal (34 weeks post-vaccination) periods. Immunological, virological, and clinical parameters were evaluated during each study period. Quantitative assessment of peripheral immunity included lymphocyte immunophenotyping, proliferation response, and interferon-γ production; and CHV-1 virus neutralizing antibody production. In the present study, vaccination did not prevent development of ocular disease and viral shedding; however, there was a significant decrease in clinical ocular disease scores in the short-term postvaccinal period. Significant alterations in peripheral immunity detected in the dogs during the short-term and long-term postvaccinal periods included increased T and B lymphocyte subpopulation percentage distributions, increased lymphocyte expression of major histocompatibility complex class I and II, increased CHV-1 virus neutralizing antibody titers, decreased lymphocyte proliferation, and decreased interferon-γ production. Vaccination of latently infected mature dogs with the selected subunit CHV-1 vaccine was not effective in preventing recurrent ocular CHV-1 infection and viral shedding induced by corticosteroid administration. The vaccine did induce long-term CHV-1 specific immunity and may decrease the severity of clinical ocular disease in the immediate postvaccinal period.

Risk Factors for Bloodstream Infection After Living-donor Liver Transplantation in Children

BACKGROUND

Postoperative bloodstream infection (BSI) is the most important determinant of recipient morbidity and mortality after liver transplantation (LT). Children who underwent LT are at the highest risk of developing BSI because of the significant surgical intervention, use of multiple devices, and administration of immunosuppressive agents. However, information regarding the risk factors for BSI in children after LT is limited.

METHODS

We retrospectively reviewed 210 children who underwent living-donor LT at the largest pediatric LT center in Japan. Patients' characteristics, blood culture results and clinical outcomes were extracted from electronic medical records. Univariate and multivariate analyses were performed to identify the risk factors for BSI.

RESULTS

Among the 210 LT recipients, 53 (25%) recipients experienced 86 episodes of BSI during the observational period. The source of the BSI was identified only in 38%: catheter-related BSI (27%) peritonitis (7%), urinary tract infection (2%), pneumonia (1%) and infectious endocarditis (1%). A multivariate analysis demonstrated that body weight (P = 0.03), volume of blood loss during LT (P < 0.001) and cytomegalovirus (CMV) antigenemia positivity (P = 0.04) were independently associated with the development of BSI. The risk factors for BSI differed when we analyzed the subjects according to age (≤24 months and >24 months), blood loss and pediatric end-stage liver disease/model for end-stage liver disease versus positive CMV antigenemia.

CONCLUSIONS

The volume of blood loss, postoperative CMV antigenemia positivity and body weight were associated with the development of BSI after LT in pediatric living-donor recipients. To identify the age-specific predictors of BSI in children who underwent LT, age-specific analyses are crucial.

Cytomegalovirus in the neonate: immune correlates of infection and protection

Fetal and neonatal infections caused by human cytomegalovirus (CMV) are important causes of morbidity and occasional mortality. Development of a vaccine against congenital CMV infection is a major public health priority. Vaccine design is currently focused on strategies that aim to elicit neutralizing antibody and T-cell responses, toward the goal of preventing primary or recurrent infection in women of child-bearing age. However, there has been relatively little attention given to understanding the mechanisms of immune protection against acquisition of CMV infection in the fetus and newborn and how this information might be exploited for vaccine design. There has similarly been an insufficient study of what deficits in the immune response to CMV, both for mother and fetus, may increase susceptibility to congenital infection and disease. Protection of the fetus against vertical transmission can likely be achieved by protection of the placenta, which has its own unique immunological milieu, further complicating the analysis of the correlates of protective immunity. In this review, the current state of knowledge about immune effectors of protection against CMV in the maternal, placental, and fetal compartments is reviewed. A better understanding of immune responses that prevent and/or predispose to infection will help in the development of novel vaccine strategies.

Impact of methimazole treatment on magnesium concentration and lymphocytes activation in adolescents with Graves' disease

The aim of this research was to assess plasma magnesium (Mg) concentration, the frequencies of activated T CD4+ and T CD8+ lymphocytes and B lymphocytes in adolescents with hyperthyroidism due to Graves' disease (GD), and to assess changes in the above-mentioned parameters during methimazole (MMI) treatment. The frequencies of activated T and B cells were measured by flow cytometry method and plasma Mg concentration was determined by spectrophotometry method in 60 adolescents at the time of GD diagnosis and after receiving the normalisation of the thyroid hormones levels. The control group consisted of 20 healthy volunteers. We observed lower plasma Mg concentration, and higher frequencies of activated T and B lymphocytes in the study group before the treatment in comparison with healthy controls, and with study group in MMI-induced euthyreosis (p < 0.01).Statistically significant negative correlations between the percentages of activated T CD3+, T CD4+, T CD8+ and B CD19+ lymphocytes, and plasma Mg concentration before the treatment were found (r < -0.335, p < 0.002). After the treatment no vital differences in plasma Mg concentration, and in percentages of activated cells between GD patients and controls were found, except CD8+CD25+ cells (p = 0.03). The present study demonstrates that both activated T and B cells might play an important role in the pathogenesis of GD, and activation is related to Mg plasma level. The use of MMI in treatment of hyperthyroidism due to GD leads to decrease the frequencies of activated lymphocytes and normalisation of Mg levels.