Cytomegalovirus glycoprotein B and N genotypes in pediatric recipients of the hematopoietic stem cell transplant

Significance of Cytomegalovirus gB Genotypes in Adult Patients Undergoing Hematopoietic Stem Cell Transplantation: Insights from a Single-Centre Investigation

INTRODUCTION

Cytomegalovirus (CMV) infection is a major clinical issue after allogeneic hematopoietic stem cell transplantation (HSCT). The CMV envelope glycoproteins are key in viral pathogenesis; the glycoprotein B (gB) encoded by the UL55 gene might be an important determinant of viral virulence and disease severity marker in patients treated with allogeneic HSCT. Our aim was to investigate the molecular diversity of CMV gB and inquire into the associations between UL55 gene variations and clinical manifestations in adult patients treated with allogeneic HSCT.

RESULTS

The most prevalent genotypes were gB1 and gB4 (11/27, 40.7%). Patients with genotype gB1 infection had earlier platelet engraftment (p < 0.033) and less frequent minimal/measurable residual disease post HSCT than those without this genotype. Patients with gB4 glycoprotein infection had a significantly lower CD4+/CD8+ ratio at D90 (p < 0.026). Interestingly, patients with gB5 glycoprotein infection had shorter overall survival from base condition diagnosis (p < 0.042), as well as shorter overall survival after HSCT (p < 0.036). Acute GvHD was noted more frequently in those with mixed-genotype infection (p = 0.047).

MATERIAL AND METHODS

The study included fifty-nine adult patients treated with allogeneic HSCT. Peripheral venous blood was sampled typically per week, with detection of CMV performed by quantitative real-time PCR. Multiplex nested PCR was used to determine specific gB genotypes, which were then statistically compared vis-à-vis specific clinical variables.

CONCLUSIONS

Our study points to variations in the viral UL55 locus imparting both beneficial (earlier platelet engraftment, less frequent MRD post HSCT) and adverse effects (shorter overall survival, more frequent acute GvHD, less frequent 100% chimerism at day 90) to the transplanted host. Comprehensive molecular investigations are necessary to validate this apparent duality, as the potential benefits of CMV could perhaps be utilized for the benefit of the patient in the future.

Determination of Genotypes in Cytomegalovirus (CMV) Strains Obtained from Pediatric and Adult Immunocompromised Patients

Background and Purpose: Cytomegalovirus causes asymptomatic disease in individuals with normal immune system; and leads to serious complications in immunocompromised individuals and fetus. In CMV, gB is the most studied glycoprotein in terms of genotyping. Up to now, four different gB genotypes (gB 1-4) of CMV have been identified. In this study, it was aimed to determine the genotypes of CMV strains obtained from patients with immune deficiency. Methods: Twenty children and 29 adults, 49 patients who were followed in the Department of Adult Hematology and Pediatric Hematology were included in the study. DNA isolation was performed from samples with CMV DNA level of 1000 IU / ml and above, and 474 bp region from the gB region of the virus was amplified by nested PCR. This region was sequenced by the Sanger (ABI 3500 Prism) sequencing. Next generation sequencing (NGS) method was applied to the samples that CMV genotype could not be determined by Sanger sequencing. Results: Distribution of CMV genotypes of patients determined by Sanger sequencing; while it was determined as 18/49 (36.7%) type 1, 5/49 (10.2%) type 2, 5/49 (10.2%) type 3 and 1/49 (2%) type 4; 14/49 (28.5%) of them were found as mixed genotypes. CMV genotype could not be determined in 6 patients by Sanger sequencing and CMV genotype of these 6 patients were found as mixed genoype by NGS. Mixed genotype was detected in 20 (40.9%) of 49 patients, in total by Sanger sequencing and NGS. Conclusion: It is remarkable that the most common genotype is mixed genotype. It was concluded that it is appropriate to study the next generation sequencing method in patients whose CMV genotype cannot be determined by Sanger sequencing.

Common Polymorphisms in the Glycoproteins of Human Cytomegalovirus and Associated Strain-Specific Immunity

Human cytomegalovirus (HCMV), one of the most prevalent viruses across the globe, is a common cause of morbidity and mortality for immunocompromised individuals. Recent clinical observations have demonstrated that mixed strain infections are common and may lead to more severe disease progression. This clinical observation illustrates the complexity of the HCMV genome and emphasizes the importance of taking a population-level view of genotypic evolution. Here we review frequently sampled polymorphisms in the glycoproteins of HCMV, comparing the variable regions, and summarizing their corresponding geographic distributions observed to date. The related strain-specific immunity, including neutralization activity and antigen-specific cellular immunity, is also discussed. Given that these glycoproteins are common targets for vaccine design and anti-viral therapies, this observed genetic variation represents an important resource for future efforts to combat HCMV infections.