High frequency of QPY allele and linkage disequilibrium of granzyme-B in Epstein-Barr-virus-associated hemophagocytic lymphohistiocytosis

Host genetics of Epstein-Barr virus infection, latency and disease

Epstein–Barr virus (EBV) infects 95% of the adult population and is the cause of infectious mononucleosis. It is also associated with 1% of cancers worldwide, such as nasopharyngeal carcinoma, Hodgkin's lymphoma and Burkitt's lymphoma. Human and cancer genetic studies are now major forces determining gene variants associated with many cancers, including nasopharyngeal carcinoma and Hodgkin's lymphoma. Host genetics is also important in infectious disease; however, there have been no large-scale efforts towards understanding the contribution that human genetic variation plays in primary EBV infection and latency. This review covers 25 years of studies into host genetic susceptibility to EBV infection and disease, from candidate gene studies, to the first genome-wide association study of EBV antibody response, and an EBV-status stratified genome-wide association study of Hodgkin's lymphoma. Although many genes are implicated in EBV-related disease, studies are often small, not replicated or followed up in a different disease. Larger, appropriately powered genomic studies to understand the host response to EBV will be needed to move our understanding of the biology of EBV infection beyond the handful of genes currently identified. Fifty years since the discovery of EBV and its identification as a human oncogenic virus, a glimpse of the future is shown by the first whole-genome and whole-exome studies, revealing new human genes at the heart of the host–EBV interaction. © 2014 The Authors. Reviews in Medical Virology published by John Wiley & Sons Ltd.

Are all granzymes cytotoxic in vivo?

Granzymes are serine proteases mainly found in cytotoxic lymphocytes. The most-studied member of this group is granzyme B, which is a potent cytotoxin that has set the paradigm that all granzymes are cyototoxic. In the last 5 years, this paradigm has become controversial. On one hand, there is a plethora of sometimes contradictory publications showing mainly caspase-independent cytotoxic effects of granzyme A and the so-called orphan granzymes in vitro. On the other hand, there are increasing numbers of reports of granzymes failing to induce cell death in vitro unless very high (potentially supra-physiological) concentrations are used. Furthermore, experiments with granzyme A or granzyme M knock-out mice reveal little or no deficit in their cytotoxic lymphocytes’ killing ability ex vivo, but indicate impairment in the inflammatory response. These findings of non-cytotoxic effects of granzymes challenge dogma, and thus require alternative or additional explanations to be developed of the role of granzymes in defeating pathogens. Here we review evidence for granzyme cytotoxicity, give an overview of their non-cytotoxic functions, and suggest technical improvements for future investigations.

Risk of generalized vitiligo is associated with the common 55R-94A-247H variant haplotype of GZMB (encoding granzyme B)

Generalized vitiligo (GV) is characterized by autoimmune destruction of melanocytes by skin-homing cytotoxic T-cells (CTLs) that target melanocyte autoantigens. Two recent genomewide association studies (GWAS) of GV in European-derived whites (EUR) have demonstrated genetic association with GZMB, encoding granzyme B, a marker of activated CTLs that mediates target-cell apoptosis, as well as autoantigen activation and consequent initiation and propagation of autoimmunity. Here, we describe detailed genetic analyses of the GZMB region of chromosome 14q12 to identify genetic variation potentially causal for GV, implicating two non-synonymous SNPs in strong linkage disequilibrium that comprise part of a common multi-variant high-risk haplotype, rs8192917-C— rs11539752-C (55R-94A). To identify possible uncommon deleterious variants that might “hitchhike” on the high-risk haplotype, we then carried out “next-generation” DNA re-sequencing of GZMB in 114 EUR GV patients. Overall, our findings support a direct causal role for the GZMB rs8192917-C—rs11539752-C haplotype (55R-94A) in the pathogenesis of GV.

Genetic variants of human granzyme B predict transplant outcomes after HLA matched unrelated bone marrow transplantation for myeloid malignancies

Serine protease granzyme B plays important roles in infections, autoimmunity, transplant rejection, and antitumor immunity. A triple-mutated granzyme B variant that encodes three amino substitutions (Q48R, P88A, and Y245H) has been reported to have altered biological functions. In the polymorphism rs8192917 (2364A>G), the A and G alleles represent wild type QPY and RAH mutant variants, respectively. In this study, we analyzed the impact of granzyme B polymorphisms on transplant outcomes in recipients undergoing unrelated HLA-fully matched T-cell-replete bone marrow transplantation (BMT) through the Japan Donor Marrow Program. The granzyme B genotypes were retrospectively analyzed in a cohort of 613 pairs of recipients with hematological malignancies and their unrelated donors. In patients with myeloid malignancies consisting of acute myeloid leukemia and myelodysplastic syndrome, the donor G/G or A/G genotype was associated with improved overall survival (OS; adjusted hazard ratio [HR], 0.60; 95% confidence interval [CI], 0.41–0.89; P = 0.01) as well as transplant related mortality (TRM; adjusted HR, 0.48; 95% CI, 0.27–0.86, P = 0.01). The recipient G/G or A/G genotype was associated with a better OS (adjusted HR, 0.68; 95% CI, 0.47–0.99; P = 0.05) and a trend toward a reduced TRM (adjusted HR, 0.61; 95% CI, 0.35–1.06; P = 0.08). Granzyme B polymorphism did not have any effect on the transplant outcomes in patients with lymphoid malignancies consisting of acute lymphoid leukemia and malignant lymphoma. These data suggest that there is an association between the granzyme B genotype and better clinical outcomes in patients with myeloid malignancies after unrelated BMT.

Genotypic variation and phenotypic characterization of granzyme B gene polymorphisms

BACKGROUND

Granzyme B has been associated with allograft rejection in solid organ transplantation. Single nucleotide polymorphisms (SNPs) in the granzyme B gene might impact its expression. The aims of this study were (1) to establish the frequency of two granzyme B SNPs (A-295G; Q-55R) in pediatric heart transplant (PHTx) recipients and (2) to determine their phenotypic expression in healthy individuals.

METHODS

Three hundred ninety-six PHTx patients (245 white non-Hispanic, 49 black non-Hispanic, 82 Hispanics, and 20 others) and 52 healthy controls were screened for Q-55R and A-295G. For the control samples, we assessed the frequency of granzyme B positive cells by ELISPOT assay after mitogen stimulation.

RESULTS

Among the PHTx recipients, 57% percent of the population carried the Q/Q genotype, whereas 6% were R/R homozygotes. Seven of 49 (14%) black non-Hispanics were R/R homozygotes, whereas 13 of 245 (5%) of white non-Hispanics and 5 of 82 (6%) Hispanics carried the R/R genotype (P=0.02). The A allele frequency of granzyme B A-295G (49.6%) was similar to that of the G allele (50.4%). However, 80% of Black non-Hispanics were A allele carriers compared with 68% of White non-Hispanics (P<0.0001). After mitogen stimulation, the frequency of granzyme B positive cells was higher in the Q/Q homozygotes compared with R/R carriers (P=0.006), whereas a similar frequency of granzyme B positive cells was noticed among the genotypes of A-295G SNP.

CONCLUSIONS

These data indicate that 55 Q/Q genotype is associated with increased in vitro expression of granzyme B.

Nationwide survey of hemophagocytic lymphohistiocytosis in Japan

Hemophagocytic lymphohistiocytosis (HLH), a disorder of the mononuclear phagocyte system, can be classified into two distinct forms: primary HLH (FHL) and secondary HLH. To clarify the epidemiology and clinical outcome for each HLH subtype, we conducted a nationwide survey of HLH in Japan. Since 799 patients were diagnosed in 292 institutions of Japan between 2001 and 2005, the annual incidence of HLH was estimated as 1 in 800,000 per year. Among them, 567 cases were actually analyzed in this study. The most frequent subtype was Epstein-Barr virus (EBV)-associated HLH, followed by other infection- or lymphoma-associated HLH. Age distribution showed a peak of autoimmune disease- and infection-associated HLH in children, while FHL and lymphoma-associated HLH occurred almost exclusively in infants and the elderly, respectively. The 5-year overall survival rate exceeded 80% for patients with EBV- or other infection-associated HLH, was intermediate for those with FHL or B-cell lymphoma-associated HLH, and poor for those with T/NK cell lymphoma-associated HLH (<15%). Although this nationwide survey establishes the heterogeneous characteristics of HLH, the results should be useful in planning prospective studies to identify the most effective therapy for each HLH subtype.

The role of Granzyme B in atheromatous diseases

The mechanism and role of apoptotic cell death in the pathogenesis of atheromatous diseases is an area of intense research. Atherosclerosis is an inflammatory disease and as such, immune-mediated cell killing plays an important role. Recent studies have suggested that Granzyme B and perforin play an important role in atherogenesis. The current manuscript reviews our current understanding pertaining to the role of Granzyme B in cardiac allograft vasculopathy and atherosclerosis.