Report

Teaser, summary, work performed and final results

Periodic Reporting for period 3 - ImmunoAgeing (An integrated approach to dissect determinants, risk factors and pathways of ageing of the immune system.)

Teaser

Changes occurring in the immune system of ageing humans – broadly referred to as ‘immunosenescence’ – have huge consequences on health, ultimately leading to a clinically evident and profound deterioration, resulting in high morbidity and mortality rates attributed to...

Summary

Changes occurring in the immune system of ageing humans – broadly referred to as ‘immunosenescence’ – have huge consequences on health, ultimately leading to a clinically evident and profound deterioration, resulting in high morbidity and mortality rates attributed to infectious and chronic diseases. Until now, diverse population-based cross-sectional studies have shown that many immune components change with age, spanning both the innate and adaptive arms of the immune system, and involving changes in cellular frequencies and altered functional capacity. In parallel, to the general downregulation of immune responsiveness with aging, is observed a smoldering rise in circulating inflammatory mediators, this phenomenon is commonly known as ‘inflammaging’. Overall, the nature of these alterations and the underlying genetics and biological determinants are still largely unknown.
The ImmunoAgeing project aims to define the extent to which immunosenescence comprises changes in levels of specific immune cell types or molecules, or functional competence of cells, and to detect genetic and non-genetic factors that drive these changes. The relatively limited sample size of the previous studies have not resolved reciprocal effects and have reported only the strongest phenotype interactions. To this aim, the project has assessed the genetic bases of the circulating immune cells and molecules that in part show a tendency with age. Also, to test why the immune system is prone to autoreactivity during aging, the autoantibody levels and B cell and T cell responsiveness were tested in individuals from the ProgeNIA cohort. Autoantibodies are responsible for the autoreactivity phenomena that is increased during ageing and to correlate their presence with chronic viral infections which will also be tested on the same sample set; in parallel the study will assess the contraction of the B cell and T cell that renders the elderly more prone to infections, and less responsive to vaccination.
In general, the whole study provides the trajectory underlying the ageing process for the age-affected traits such as immune mediators, immunoglobulins, autoantibodies, cell frequencies, surface markers, transcripts and B and T cell receptor indices in a core cohort from 1000 to 4000 shared individuals for carrying out an integrated data analysis

Work performed

The study has been focused on diverse aspects of the immune system including the levels of the circulating cells considered as actual numbers and as percentage with respect to the parental lineage. These traits represented the starting point of the project whose data have contributed to generate additional working hypothesis that articulate the ImmunoAgeing Project itself. At first instance the assessed immune traits were broaden in numbers of profiled individuals and in number of cell population tested, specifically, from four 8-color phenotyping panels on 2,000 individual to additional three, up to 14-color, panels on 4,000 individuals.
The analysis of flow cytometry data were both genetic and epidemiological with the aim of identify the DNA variants affecting their quantitative variation and their alterations with aging, respectively.
In details, the study of the genetic component served to establish the amount of variation in immune traits that is attributable to inherited variation (‘heritability’). The heritability of the assessed immunophenotypes capturing the proportion of genetic variation due to additive genetic effects averaged 35.9%, with the highest values of 79.0% for a Treg subpopulation highly expressing the CD39 activation marker. Interestingly, the lymphoid cells were 12% more heritable than myeloid cells (38.3% vs 33.6%, respectively), and among lymphoid cells, CD4 T subsets were the most heritable, followed by B and CD8 T subsets (46.4%; 37.6%; 35.3%, respectively). To identify the genetic variation accounting for the inherited component of the 730 immunophenotypes, we performed GWAS, assessing 20,143,392 SNPs and 1,688,858 indels, either genotyped with high density arrays or imputed through our Sardinian sequence-based reference panel of 3,514 individuals.
The plan for a proper exploitation and dissemination of the results is to reach both the scientific and non-scientific community through the publication in high impact journals and by means of conferences for the general public.

Final results

Among the main results of the ImmunoAgeing Project is the identification of molecules of potential interest for druggability with particular emphasis in the context of autoimmunity. We considered as a druggable target any protein whose expression has been showed to be regulated by the associated genetic signals underlying associations with diseases in addition to the immunological traits assessed during the course of the study. Furthermore, we were particularly interested in targets whose downregulation would be protective against the disease because inhibition of targets is usually easier to obtain than their hyper functionality.
Of the 23 proteins underlying that were genetically regulated by variants involved in disease predisposition, 16 are classified as drug targets in the Pharmaprojects database. Remarkably, our genetic findings suggest new indications for use of 12 of these 16 alleged druggable targets, thus identifying candidates for drug repurposing efforts. For example, some potential targets for therapeutic modulation of autoimmune diseases include CD28, CD40 and CD25. For instance, many drugs acting against CD40 are currently in clinical trials. Our genetic evidence of reduced expression of CD40 in various B-cell subtypes that confers protection for Rheumatoid Arthritis and Kawasaki disease is consistent with corresponding intervention. However, in view of the genetic associations detected in our study, therapeutic downregulation of CD40 in these diseases might engender increased risk for other autoimmune diseases, like Multiple Sclerosis, Crohn\'s Disease and Systemic Lupus Erythematosus, because the same genetic signal increased susceptibility to these diseases. The highlighted observations in the context of the biological processes regulating immunosenescence and autoimmunity have an high socio-economic impact for therapeutic intervention on high-frequency diseases affecting the community. This is one of the main outcome of the ImmunoAgeing Project, however, following the ongoing integrative analysis, we aspect to broaden the information valuable for the aging portion of the general population.

Website & more info

More info: http://www.immunoageing.eu/.