'Immunogenetics of Aging': report on the activities of the 15th International HLA and Immunogenetics Working Group and 15th International HLA and Immunogenetics Workshop

High-resolution characterization of KIR genes polymorphism in healthy subjects from the Bulgarian population-A pilot study

Although killer-cell immunoglobulin-like receptor (KIR) gene content has been widely studied in health and disease, with the advancement of next-generation sequencing (NGS) technology the high-resolution characterization of this complex gene region has become achievable. KIR allele-level diversity has lately been described across human populations. The present study aimed to analyze for the first time the allele-level polymorphism of nine KIR genes in 155 healthy, unrelated individuals from the Bulgarian population by applying NGS. The highest degree of polymorphism was detected for the KIR3DL3 gene with 40 observed alleles at five-digit resolution in total, 22 of which were common. On the other hand, the KIR3DS1 gene was found to have the lowest degree of polymorphism among the studied KIR genes with one common allele: KIR3DS1*01301 (31.6%). To better understand KIR allelic associations and patterns in Bulgarians, we have estimated the pairwise linkage disequilibrium (LD) for the 10 KIR loci, where KIR2DL3*00501 allele was found in strong LD with KIR2DL1*00101 (D' = 1.00, R2  = 0.742). This is the first study investigating KIR polymorphism at the allele level in a population from the South-East European region. Considering the effect of the populationally shaped KIR allelic polymorphism on NK cell function, this data could lead to a better understanding of the genetic heterogeneity of this region and can be carried into clinical practice by improvement of the strategies taken for NK-mediated diseases.

17th IHIW component "Immunogenetics of Ageing" - New NGS data

The 'Immunogenetics of Aging' project is a component introduced in the 14th International HLA and Immunogenetics Workshop (IHIW) and developed further within subsequent workshops. The aim was to determine the relevance of immunogenetic markers, focusing on HLA, cytokine genes, and some innate immunity genes, for successful aging and an increased capacity to reach the extreme limits of life-span. Within the 17th IHIW we applied Next Generation Sequencing methods to refine further HLA associations at allele level in longevity, and to extend our knowledge to additional loci such as HLA-DQA1, HLA-DPB1 and HLA-DPA1. Analysis of relatively small number of healthy elderly and young controls from four populations showed that some HLA class I and class II alleles were significantly positively associated with healthy aging. Additionally we observed statistically significant differences in HLA allele distribution when the analysis was performed separately in elderly females and males compared to sex-matched young controls. Haplotypes, probably associated with better control of viral and malignant diseases were increased in the elderly sample. These preliminary NGS data could confirm our hypotheses that survival and longevity might be associated with selection of HLA alleles and haplotypes conferring disease resistance or susceptibility. Therefore HLA alleles and haplotypes could be informative immunogenetic markers for successful ageing.

Role of Immunogenetics in the Outcome of HCMV Infection: Implications for Ageing

The outcome of host-virus interactions is determined by a number of factors, some related to the virus, others to the host, such as environmental factors and genetic factors. Therefore, different individuals vary in their relative susceptibility to infections. Human cytomegalovirus (HCMV) is an important pathogen from a clinical point of view, as it causes significant morbidity and mortality in immunosuppressed or immunosenescent individuals, such as the transplanted patients and the elderly, respectively. It is, therefore, important to understand the mechanisms of virus infection control. In this review, we discuss recent advances in the immunobiology of HCMV-host interactions, with particular emphasis on the immunogenetic aspects (human leukocyte antigens, HLA; killer cell immunoglobulin-like receptors, KIRs; immunoglobulin genetic markers, GM allotypes) to elucidate the mechanisms underlying the complex host-virus interaction that determine various outcomes of HCMV infection. The results, which show the role of humoral and cellular immunity in the control of infection by HCMV, would be valuable in directing efforts to reduce HCMV spurred health complications in the transplanted patients and in the elderly, including immunosenescence. In addition, concerning GM allotypes, it is intriguing that, in a Southern Italian population, alleles associated with the risk of developing HCMV symptomatic infection are negatively associated with longevity.

Collection and storage of HLA NGS genotyping data for the 17th International HLA and Immunogenetics Workshop

For over 50 years, the International HLA and Immunogenetics Workshops (IHIW) have advanced the fields of histocompatibility and immunogenetics (H&I) via community sharing of technology, experience and reagents, and the establishment of ongoing collaborative projects. Held in the fall of 2017, the 17th IHIW focused on the application of next generation sequencing (NGS) technologies for clinical and research goals in the H&I fields. NGS technologies have the potential to allow dramatic insights and advances in these fields, but the scope and sheer quantity of data associated with NGS raise challenges for their analysis, collection, exchange and storage. The 17th IHIW adopted a centralized approach to these issues, and we developed the tools, services and systems to create an effective system for capturing and managing these NGS data. We worked with NGS platform and software developers to define a set of distinct but equivalent NGS typing reports that record NGS data in a uniform fashion. The 17th IHIW database applied our standards, tools and services to collect, validate and store those structured, multi-platform data in an automated fashion. We have created community resources to enable exploration of the vast store of curated sequence and allele-name data in the IPD-IMGT/HLA Database, with the goal of creating a long-term community resource that integrates these curated data with new NGS sequence and polymorphism data, for advanced analyses and applications.

CMV and Immunosenescence: from basics to clinics

Alone among herpesviruses, persistent Cytomegalovirus (CMV) markedly alters the numbers and proportions of peripheral immune cells in infected-vs-uninfected people. Because the rate of CMV infection increases with age in most countries, it has been suggested that it drives or at least exacerbates “immunosenescence”. This contention remains controversial and was the primary subject of the Third International Workshop on CMV & Immunosenescence which was held in Cordoba, Spain, 15-16^th March, 2012. Discussions focused on several main themes including the effects of CMV on adaptive immunity and immunosenescence, characterization of CMV-specific T cells, impact of CMV infection and ageing on innate immunity, and finally, most important, the clinical implications of immunosenescence and CMV infection. Here we summarize the major findings of this workshop.

Prevalence of at-risk genotypes for genotoxic effects decreases with age in a randomly selected population in Flanders: a cross sectional study

BACKGROUND

We hypothesized that in Flanders (Belgium), the prevalence of at-risk genotypes for genotoxic effects decreases with age due to morbidity and mortality resulting from chronic diseases. Rather than polymorphisms in single genes, the interaction of multiple genetic polymorphisms in low penetrance genes involved in genotoxic effects might be of relevance.

METHODS

Genotyping was performed on 399 randomly selected adults (aged 50-65) and on 442 randomly selected adolescents. Based on their involvement in processes relevant to genotoxicity, 28 low penetrance polymorphisms affecting the phenotype in 19 genes were selected (xenobiotic metabolism, oxidative stress defense and DNA repair, respectively 13, 6 and 9 polymorphisms). Polymorphisms which, based on available literature, could not clearly be categorized a priori as leading to an 'increased risk' or a 'protective effect' were excluded.

RESULTS

The mean number of risk alleles for all investigated polymorphisms was found to be lower in the 'elderly' (17.0 ± 2.9) than the 'adolescent' (17.6 ± 3.1) subpopulation (P = 0.002). These results were not affected by gender nor smoking. The prevalence of a high (> 17 = median) number of risk alleles was less frequent in the 'elderly' (40.6%) than the 'adolescent' (51.4%) subpopulation (P = 0.002). In particular for phase II enzymes, the mean number of risk alleles was lower in the 'elderly' (4.3 ± 1.6 ) than the 'adolescent' age group (4.8 ± 1.9) P < 0.001 and the prevalence of a high (> 4 = median) number of risk alleles was less frequent in the 'elderly' (41.3%) than the adolescent subpopulation (56.3%, P < 0.001). The prevalence of a high (> 8 = median) number of risk alleles for DNA repair enzyme-coding genes was lower in the 'elderly' (37,3%) than the 'adolescent' subpopulation (45.6%, P = 0.017).

CONCLUSIONS

These observations are consistent with the hypothesis that, in Flanders, the prevalence of at-risk alleles in genes involved in genotoxic effects decreases with age, suggesting that persons carrying a higher number of at risk alleles (especially in phase II xenobiotic-metabolizing or DNA repair genes) are at a higher risk of morbidity and mortality from chronic diseases. Our findings also suggest that, regarding risk of disease associated with low penetrance polymorphisms, multiple polymorphisms should be taken into account, rather than single ones.

Immunogenetics of ageing

The ageing process is very complex. Human longevity is a multifactorial trait which is determined by genetic and environmental factors. Twin and family studies imply that up to 25% of human lifespan is heritable. The longevity gene candidates have generally fallen into the following categories: inflammatory and immune-related factors, stress response elements, mediators of glucose and lipid metabolism, components of DNA repair and cellular proliferation and mitochondrial DNA haplogroups. Because of the central role of HLA molecules in the development of protective immunity and the extraordinary degree of polymorphism of HLA genes, many studies have addressed the possible impact of these genes on human longevity. Most of the data available so far demonstrated a possible role of HLA class II specificities in human longevity but definitive evidence has remained elusive. Although the data are limited and controversial, it has been hypothesized that longevity could be associated with cytokine gene polymorphisms correlating with different levels of cytokine production, thereby modulating immune responses in health and disease. Because of the essential role of cytokines in immune responses, the regulation of cytokine gene expression and their polymorphic nature, the genetic variations of these loci with functional significance could be appropriate immunogenetic candidate markers implicated in the mechanism of successful ageing and longevity. In addition, several other genes such as Toll-like receptor genes, Cycloxygenases (COX)/Lipoxygenases (LOX), CCR5, NK receptor genes and MBL2 have been assessed as a possible biomarkers associated with ageing. This review will summarize the data on the role of these immune genes in human longevity.