Specific Immunity to Cytomegalovirus in Pediatric Cardiac Transplantation

Cytomegalovirus Cell-mediated Immunity Assays in Pediatric Transplantation

Cytomegalovirus (CMV) is a significant cause of morbidity and mortality in pediatric transplantation. However, currently utilized CMV prevention paradigms have limitations, leading to research aimed at novel strategies for mitigation of CMV infection. Cell-mediated immunity (CMI) is crucial in controlling CMV infection and the use of CMV-specific CMI assays to guide prevention and treatment of CMV infection in both solid organ transplant and hematopoietic cell transplant recipients shows great promise. In this article, we review the immune response to CMV infection to highlight the rationale for CMI assays, describe available commercial assays and strategies for their use, and summarize relevant literature regarding the use of CMI assays in transplant recipients.

Update on Epidemiology and Outcomes of Infection in Pediatric Organ Transplant Recipients

Pediatric solid organ transplant (SOT) recipients are at risk for infection following transplantation. Data from adult SOT recipients are often used to guide prevention and treatment of infections associated with organ transplantation in children. This article highlights key recent pediatric SOT-specific publications for an array of infectious complications of organ transplantation. Attention is given to areas of need for future study.

Clinical utility of immune function based on IFN-γ monitoring of lymphocyte subsets for parvovirus B19 infection in renal recipients

BACKGROUND

There should be a heightened index of suspicion for Parvovirus B19 (PVB19)-related anemia in organ transplant recipients. Thus far, there is no consensus or recommendation for clinical routine monitoring methods of PVB19 recipients to allow tailoring of immunosuppression.

METHODS

We conducted a retrospective study to evaluate the utility of the function (represented by the abilities to secrete IFN-γ) and numbers of lymphocyte subsets in monitoring PVB19 infections in renal recipients posttransplant. The enrolled 109 patients were split into 2 groups according to whether the recipients had an occurrence of PVB19 infection: 37 (33.94%) recipients developed PVB19 infection and 72 (66.06%) immune-stable recipients.

RESULTS

The PVB19 infected group had significantly lower absolute counts and functions of different lymphocyte subsets compared with immune-stable recipients. We showed that the frequencies of IFN-γ + CD4 + T cells, IFN-γ + CD8 + T cells, and IFN-γ + NK cells increased markedly after treatment when compared to the occurrence in patients with timepoint before therapy, especially the percentages of IFN-γ + CD4 + T cells were significantly higher. Receiver operating characteristic (ROC) analysis showed that the optimal infection indicator was IFN-γ + NK cells frequency, with an auROC curve of 0.925. Concomitantly, Cox regression analysis indicated that the post-therapy increasing level of IFN-γ secreting function was significantly predictive of recurrent infections (P < 0.001).

CONCLUSIONS

We recommend prospective risk stratification for the high-risk population at risk of early-onset PVB19 infection and its recurrence involves screening strategies of immune-based surveillance with the sensitive IFN-γ + secreting monitoring for antiviral prophylaxis and preemptive therapy goal. Clinical Trial Notation: clinical trial registration number: chiCTR-ROC-17010756.

Functional Changes of T-Cell Subsets with Age and CMV Infection

Cytomegalovirus (CMV) latent infection and aging contribute to alterations in the function and phenotype of the T-cell pool. We have demonstrated that CMV-seropositivity is associated with the expansion of polyfunctional CD57+ T-cells in young and middle-aged individuals in response to different stimuli. Here, we expand our results on the effects of age and CMV infection on T-cell functionality in a cohort of healthy middle-aged and older individuals stratified by CMV serostatus. Specifically, we studied the polyfunctional responses (degranulation, IFN-γ and TNF-α production) of CD4+, CD8+, CD8+CD56+ (NKT-like), and CD4−CD8− (DN) T-cells according to CD57 expression in response to Staphylococcal Enterotoxin B (SEB). Our results show that CD57 expression by T-cells is not only a hallmark of CMV infection in young individuals but also at older ages. CD57+ T-cells are more polyfunctional than CD57− T-cells regardless of age. CMV-seronegative individuals have no or a very low percentages of cytotoxic CD4+ T-cells (CD1017a+) and CD4+CD57+ T-cells, supporting the notion that the expansion of these T-cells only occurs in the context of CMV infection. There was a functional shift in T-cells associated with CMV seropositivity, except in the NKT-like subset. Here, we show that the effect of CMV infection and age differ among T-cell subsets and that CMV is the major driving force for the expansion of highly polyfunctional CD57+ T-cells, emphasizing the necessity of considering CMV serology in any study of immunosenescence.

Impact of SARS-CoV-2 infection on the recovery of peripheral blood mononuclear cells by density gradient

SARS-CoV-2 virus infection is responsible for coronavirus disease (COVID-19), which is characterised by a hyperinflammatory response that plays a major role in determining the respiratory and immune-mediated complications of this condition. While isolating peripheral blood mononuclear cells (PBMCs) from whole blood of COVID-19 patients by density gradient centrifugation, we noticed some changes in the floating properties and in the sedimentation of the cells on density medium. Investigating this further, we found that in early phase COVID-19 patients, characterised by reduced circulating lymphocytes and monocytes, the PBMC fraction contained surprisingly high levels of neutrophils. Furthermore, the neutrophil population exhibited alterations in the cell size and in the internal complexity, consistent with the presence of low density neutrophils (LDNs) and immature forms, which may explain the shift seen in the floating abilities and that may be predictive of the severity of the disease. The percentage of this subset of neutrophils found in the PBMC band was rather spread (35.4 ± 27.2%, with a median 28.8% and IQR 11.6-56.1, Welch's t-test early phase COVID-19 versus blood donor healthy controls P < 0.0001). Results confirm the presence of an increased number of LDNs in patients with early stage COVID-19, which correlates with disease severity and may be recovered by centrifugation on a density gradient together with PBMCs.