Impact of immunosenescence on in vitro response of B lymphocytes of individuals vaccinated against COVID-19: influence of smoking and chronic obstructive pulmonary disease

Abstract

The fact that COVID-19 pandemia has led to an unprecedented, worldwide effort to develop a vaccine able to confer protection to a large and heterogeneous population, gave rise to the reemergence of the issue of vaccination of elderly and those bearing chronic diseases. While these populations show enhanced susceptibility to the severe forms of the COVID-19, they also tend to develop weaker vaccine responses compared with youngs and adults in general. Aged people are immunologically characterized for presenting immunosenescence. This condition refers to a state defined by robust measures of immune parameters (biomarkers) that are different in younger and older individuals that have been associated with detrimental clinical outcome (e.g. mortality, frailty, poor response to vaccination). Individuals suffering from chronic inflammatory diseases. e.g., COPD patients also develop a phenotype called accelerated immunosenescence. Several aspects of immunosenescence have been investigated in the last two decades, mostly dealing with the T lymphocyte compartment. Information regarding alterations of the B lymphocyte compartment linked to immunosenescence are less well understood and less well established, as can be exemplified by the role of B lymphocytes in the poorer vaccine responses of the elderly. Therefore, this project aims to investigate the B lymphocyte response and production of specific antibodies to SARS-CoV-2 proteins after vaccination against COVID-19. Peripheral blood mononuclear cells from healthy aged individuals (e 60 y-o), patients with COPD, aged smokers but without pulmonary impairment compatible with COPD, will be compared with PBMC from young adults (e 35 y-o). PBMC cultures will be submitted to several analyses: phenotyping assays (flow cytometry) to determine the B lymphocyte subpopulations and the expression of surface and intracellular functional molecules, assays for purifying B lymphocyte population followed by in vitro expansion of these cells, and then exposure to specific viral proteins to evaluate the capacity of clonal expansion, specific antibody production and pro/anti-inflammatory cytokines secretion, as well as testing the B lymphocyte culture supernatants in a SARS-CoV-2 neutralization assay. Some features of the T-cell responses will also be assessed, such as Th patterns, cytokines and immunophenotyping. We expect, with these experiments, to collect relevant data aiming at better characterizing B lymphocyte responses to the vaccine in the healthy aged and in the aged with comorbidities. This knowledge is crucial for the design of better vaccine candidates in this specific population: beyond the well-known effects of immunosenescence on the T-cell compartment, information regarding B lymphocyte dysfunctions may uncover novel mechanisms that impair vaccines response, particularly regarding the amount and quality of the antibody production. (AU)