Factores inmunogenéticos y respuesta inmunológica en pacientes Covid-19

Abstract

Infection with the new SARS-CoV-2 coronavirus has generated many unknowns about the role of the immune system in the pathology and resolution of the infection. COVID- 19 produces an immune imbalance characterized by lymphopenia, elevated biochemical markers of inflammation and cytokines, which can lead to a cytokine storm and more severe disease. On the other hand, the immune system is made up of a multitude of cells and proteins that intervene in the course of a viral infection, participating in both innate and adaptive immunity. All these factors intervene in the evolution of the infection, being determinant in its severity. Objectives We set out to determine the immunologic and immunogenetic profile of patients with COVID-19 and its relationship to disease severity: - In the first part, the lymphocyte profile of patients with COVID-19 was studied and characterized, determining the frequency and functional profile (activation and exhaustion) of lymphocyte subpopulations in hospitalized patients. In addition, the lymphocyte subpopulations functional profile (activation and depletion) was analyzed. These data were related to biochemical and clinical parameters of patients with different degrees of COVID-19 severity. - Subsequently, we focused on the role of immunogenetics, studying the HLA and MICA polymorphic systems. We searched for alleles that could explain susceptibility or protection against infection and severity of COVID-19. - Finally, in conjunction with the development of COVID-19 vaccines, we studied the humoral and cellular immune response in individuals vaccinated with the Moderna mRNA-1273 SARS-CoV-2 vaccine. In addition, we analyzed the role of HLA class II molecules in the humoral response of those vaccinated with mRNA-1273. Materials and Methods A population of 144 patients admitted for COVID-19 was used to study lymphocyte subpopulations. They were classified according to their severity. Analysis of lymphocyte subpopulations was performed by multiparametric flow cytometry, determining the affected subpopulations and their functional status. In addition, a database was created with different markers of inflammation and disease severity. All these parameters were analyzed and related to each other to determine prognostic markers. In the immunogenetics study we included 483 COVID-19 patients with different degrees of severity. High resolution typing for HLA alleles and determination of MICA STR alleles were performed. Next, allele frequencies were compared between the different severity groups and the control group. Finally, we obtained 601 samples from individuals vaccinated with mRNA-1273 and not previously infected with SARS-CoV-2. Humoral and cellular responses were determined and classified into three groups according to the degree of response. In the end, 30 individuals were selected from each group and HLA class II typing was performed. Results Analysis of lymphopenia showed a decrease in CD4+ and CD8+ T cells. The study of T helper (Th) revealed alterations in most of them, with a marked decrease of Th1 cells. An increase in Th0 lymphocytes and a low degree of lymphocyte activation were also observed. More severe patients were characterized by a higher degree of lymphopenia and neutrophilia along with an increased expression of markers of activation and exhaustion in T lymphocytes. Regarding immunogenetics, HLA typing results showed no association with risk, protection, or severity of SARS-CoV-2 infection. In the analysis of MICA molecules, the MICA*A9 allele was associated with infection and moderate disease. Finally, in the study of the immune response in individuals vaccinated with mRNA-1273, a general humoral response of great amplitude was observed. The cellular study yielded a response of 86% which was positively related to the magnitude of humoral response. In the end, the HLA-DRB1*07:01 allele and HLADRB1* 07:01~DQA1*02:01~DQB1*02:02 haplotype were associated with a more intense humoral response. Conclusions - Poor control of SARS-CoV-2 infection is characterized by lymphopenia with a marked decrease in Th1 lymphocytes, an increase in Th0 lymphocytes and a low degree of lymphocyte activation. - HLA alleles and haplotypes are not associated with severity and susceptibility to SARS-CoV-2 infection. - MICA*A9 allele is a risk factor for SARS-CoV-2 infection and severity. - There is a general humoral response in mRNA-1273 vaccinees, similar to that observed in convalescent COVID-19 patients. The cellular response was positively related to the degree of humoral response. - The HLA-DRB1*07:01 allele and its associated haplotype are positively related to the generation of a more intense humoral response in those vaccinated with mRNA-1273.