Summary
Knowledge of donor and recipient (D/R) cytomegalovirus (CMV) serostatus is critical for risk stratification of CMV infection and disease in transplant recipients, particularly in the solid ...organ transplantation (SOT) setting. Despite its broad availability and the success of it use, the risk stratification based on the D/R serostatus is not free of limitations since there are a nondepreciable number of patients that are not accurately categorized by this approach. In fact, up to 20% of seropositive SOT recipients, classically considered at intermediate risk, develop episodes of CMV infection and disease after transplantation. Here, we provide an overview of additional donor and recipient factors that may have utility in identifying patients at risk for post‐transplant CMV infection. Specifically, we summarize our current understanding regarding the potential use of use CMV‐specific T‐cell‐mediated immunity, neutralizing antibodies and host genetics that may influence the risk of CMV infection and disease. We provide an overview of the benefits and limitations associated with using these immunological factors in risk stratification and propose specific variables that could be analyzed at the pretransplant evaluation to improve the identification of patients with increased individual susceptibility.
The humoral immune response of transplant recipients to influenza vaccination has been studied in detail. In contrast, the hemagglutinin inhibiting (HI) antibody response evoked by natural influenza ...infection and its impact on viral kinetics is unknown. In this prospective, multicenter, cohort study of natural influenza infection in transplant recipients, we measured HI antibody titers at presentation and 4 weeks later. Serial nasopharyngeal viral loads were determined using a quantitative influenza A polymerase chain reaction (PCR). We analyzed 196 transplant recipients with influenza infection. In the cohort of organ transplant patients with influenza A (n = 116), seropositivity rates for strain‐specific antibodies were 44.0% (95% confidence interval CI 31.5‐53.2%) at diagnosis and 64.7% (95% CI 55.4‐72.9%) 4 weeks postinfection. Seroconversion was observed in 32.8% (95% CI 24.7‐41.9%) of the cases. Lung transplant recipients were more likely to seroconvert (P = .002) and vaccine recipients were less likely to seroconvert (P = .024). A subset of patients (n = 30) who were unresponsive to prior vaccination were also unresponsive to natural infection. There was no correlation between viral kinetics and antibody response. This study provides novel data on the seroresponse to influenza infection in transplant patients and its relationship to a number of parameters including a prior vaccination status, virologic measures, and clinical variables.
This prospective, multicenter cohort study of transplant recipients reports the strain‐specific hemagglutinin‐inhibiting antibody response to natural influenza infection and demonstrates that serologic response rates are poor in this population and antibody responses are largely unrelated to nasopharyngeal viral measures.
Primary infection and/or reactivation of cytomegalovirus (CMV) in kidney transplant recipients (KTR) favor rejection and mortality. T follicular helper cells (TFH) could contribute to protection ...against CMV. Circulatory TFH (cTFH) were studied pretransplant and early posttransplant in 90 CMV seropositive KTR not receiving antithymocyte globulin or antiviral prophylaxis, followed‐up for 1 year. Patients who presented CMV infection had significantly lower cTFH and activated cTFH pretransplant and early posttransplant. Pretransplant activated cTFH were also lower within patients who developed CMV disease. Pre‐ and 14 days posttransplant activated cTFH were an independent protective factor for CMV infection (HR 0.41, p = .01; and 0.52, p = .02, respectively). KTR with low cTFH 7 days posttransplant (<11.9%) had lower CMV infection‐free survival than patients with high cTFH (28.2% vs. 67.6%, p = .002). cTFH were associated with CMV‐specific neutralizing antibodies (Nabs). In addition, IL‐21 increased interferon‐γ secretion by CMV‐specific CD8+ T cells in healthy controls. Thus, we show an association between cTFH and lower incidence of CMV infection, probably through their cooperation in CMV‐specific Nab production and IL‐21‐mediated enhancement of CD8+ T cell activity. Moreover, monitoring cTFH pre‐ and early posttransplant could improve CMV risk stratification and help select KTR catalogued at low/intermediate risk who could benefit from prophylaxis.
Circulatory T follicular helper cells may protect against cytomegalovirus reactivation by promoting neutralizing antibody production and fostering effector cellular responses by secreting IL‐21 and also may serve as a biomarker to identify CMV seropositive patients at high risk of cytomegalovirus reactivation.
CMV is a major cause of morbidity and mortality in immunocompromised individuals that will benefit from the availability of a vaccine. Despite the efforts made during the last decade, no CMV vaccine ...is available. An ideal CMV vaccine should elicit a broad immune response against multiple viral antigens including proteins involved in virus-cell interaction and entry. However, the therapeutic use of neutralizing antibodies targeting glycoproteins involved in viral entry achieved only partial protection against infection. In this scenario, a better understanding of the CMV proteome potentially involved in viral entry may provide novel candidates to include in new potential vaccine design. In this study, we aimed to explore the CMV genome to identify proteins with putative transmembrane domains to identify new potential viral envelope proteins. We have performed in silico analysis using the genome sequences of nine different CMV strains to predict the transmembrane domains of the encoded proteins. We have identified 77 proteins with transmembrane domains, 39 of which were present in all the strains and were highly conserved. Among the core proteins, 17 of them such as UL10, UL139 or US33A have no ascribed function and may be good candidates for further mechanistic studies.
During the last decade, many studies have demonstrated the role of CMV specific T-cell immune response on controlling CMV replication and dissemination. In fact, it is well established that ...transplanted patients lacking CMV-specific T-cell immunity have an increased occurrence of CMV replication episodes and CMV-related complications. In this context, the use of adoptive transfer of CMV-specific T-cells has been widely investigated and applied to Hematopoietic Stem Cell Transplant patients and may be useful as a therapeutic alternative, to reconstitute the CMV specific T-cell response and to control CMV viremia in patients receiving a transplantation. However, only few authors have explored the use of T-cell adoptive transfer in SOT recipients. We propose a novel review in which we provide an overview of the impact of using CMV-specific T-cell adoptive transfer on the control of CMV infection in SOT recipients, the different approaches to stimulate, isolate and expand CMV-specific T-cells developed over the years and a discussion of the possible use of CMV adoptive cellular therapy in this SOT population. Given the timeliness and importance of this topic, we believe that such an analysis will provide important insights into CMV infection and its treatment/prevention.
The B and T lymphocytes of the adaptive immune system are important for the control of most viral infections, including COVID-19. Identification of epitopes recognized by these cells is fundamental ...for understanding how the immune system detects and removes pathogens, and for antiviral vaccine design. Intriguingly, several cross-reactive T lymphocyte epitopes from SARS-CoV-2 with other betacoronaviruses responsible for the common cold have been identified. In addition, antibodies that cross-recognize the spike protein, but not the nucleoprotein (N protein), from different betacoronavirus have also been reported. Using a consensus of eight bioinformatic methods for predicting B-cell epitopes and the collection of experimentally detected epitopes for SARS-CoV and SARS-CoV-2, we identified four surface-exposed, conserved, and hypothetical antigenic regions that are exclusive of the N protein. These regions were analyzed using ELISA assays with two cohorts: SARS-CoV-2 infected patients and pre-COVID-19 samples. Here we describe four epitopes from SARS-CoV-2 N protein that are recognized by the humoral response from multiple individuals infected with COVID-19, and are conserved in other human coronaviruses. Three of these linear surface-exposed sequences and their peptide homologs in SARS-CoV-2 and HCoV-OC43 were also recognized by antibodies from pre-COVID-19 serum samples, indicating cross-reactivity of antibodies against coronavirus N proteins. Different conserved human coronaviruses (HCoVs) cross-reactive B epitopes against SARS-CoV-2 N protein are detected in a significant fraction of individuals not exposed to this pandemic virus. These results have potential clinical implications.
The aim of this study was to identify CMV drug resistance mutations (DRM) in solid organ transplant (SOT) recipients with suspected resistance comparing next-generation sequencing (NGS) with Sanger ...sequencing and assessing risk factors and the clinical impact of resistance.
Using Sanger sequencing as the reference method, we prospectively assessed the ability of NGS to detect CMV DRM in the UL97 and UL54 genes in a nationwide observational study from September 2013 to August 2016.
Among 44 patients recruited, 14 DRM were detected by Sanger in 12 patients (27%) and 20 DRM were detected by NGS, in 16 (36%). NGS confirmed all the DRM detected by Sanger. The additional six mutations detected by NGS were present in <20% of the sequenced population, being located in the UL97 gene and conferring high-level resistance to ganciclovir. The presence of DRM by NGS was associated with lung transplantation (p = 0.050), the administration of prophylaxis (p = 0.039), a higher mean time between transplantation and suspicion of resistance (p = 0.038) and longer antiviral treatment duration before suspicion (p = 0.024). However, the latter was the only factor independently associated with the presence of DRM by NGS in the multivariate analysis (OR 2.24, 95% CI 1.03 to 4.87).
NGS showed a higher yield than Sanger sequencing for detecting CMV resistance mutations in SOT recipients. The presence of DRM detected by NGS was independently associated with longer antiviral treatment.
Human cytomegalovirus (HCMV) continues to be a major cause of morbidity in transplant patients and newborns. However, the functions of many of the more than 282 genes encoded in the HCMV genome ...remain unknown. The development of bacterial artificial chromosome (BAC) technology contributes to the genetic manipulation of several organisms including HCMV. The maintenance of the HCMV BAC in E. coli cells permits the rapid generation of recombinant viral genomes that can be used to produce viral progeny in cell cultures for the study of gene function. We optimized the Lambda-Red Recombination system to construct HCMV gene deletion mutants rapidly in the complete set of tested genes. This method constitutes a useful tool that allows for the quick generation of a high number of gene deletion mutants, allowing for the analysis of the whole genome to improve our understanding of HCMV gene function. This may also facilitate the development of novel vaccines and therapeutics.
Little is known about the long-term antibody response to the 2009-H1N1 vaccine in solid organ transplant recipients (SOTR) and its clinical repercussion on the efficacy of following 2010-2011 ...influenza vaccine.
We performed a multicenter prospective study in SOTR receiving one dose of the nonadjuvant 2010-2011 seasonal influenza vaccine and determined the immunological response at 5 weeks after vaccination.
One hundred SOTR were included. Long-term antibody titers to the previous vaccine were only detected in one third of the patients. Patients with baseline titers had significantly higher seroprotection for the 2009-H1N1 strain (100% vs. 73%, relative risks RR 1.37, 95% confidence intervals CI 1.19-1.57; P=0.006), for H3N2 strain (100% vs. 62.2%, RR 1.61, 95% CI 1.36-1.90; P=0.005), and for B strain (100% vs. 69%; P=0.02). The seroconversion rate in patients with baseline titers was 90.9% vs. 73% (RR 2.97, 95% CI 0.75-11.74; P=0.07) for the 2009-H1N1 strain, 92.2% vs. 62.2% (RR 5.29, 95% CI 0.8-35.7; P=0.02) for the H3N2 strain, and 58.3% vs. 69% (P=0.45) for the B strain.
SOTR response to the 2010-2011 influenza vaccine was not optimal. The response was related to baseline titers; however, most of the patients did not exhibit detectable antibodies at vaccination lacking long-term response. New strategies are necessary to improve vaccination efficacy.
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