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Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has infected millions of people around the world, leading to respiratory coronavirus disease (COVID-19) and a global pandemic in 2019. The rapid development and deployment of different COVID-19 vaccines and non-pharmaceutical interventions (such as hard and soft lockdowns) have effectively curbed the number of new infections, hospitalizations and deaths worldwide every day.

However, although the vaccine is the most likely way to protect yourself from severe COVID-19 and related hospitalization, the antibody response and neutralizing activity have been achieved within a few months after the initial SARS-CoV-2 infection and vaccination. Weaken.

SARS-CoV-2 variants with mutations in the spike protein that help the virus evade the host immune response exacerbate this problem for survivors and vaccinators. They have become a major obstacle to ending this epidemic.

So far, four variants-B.1.1.7 (alpha or UK variants), B.1.351 (beta, RSA), P.1 (gamma, BRA) and B.1.617.2 (delta, IND ) Are called variants of concern (VoC) because they can spread and cause breakthrough infections even in vaccinated people.

After the initial infection, in parallel with the antibody response, symptomatic COVID19 survivors have a strong CD4 and CD8 memory T cell response, which targets a wider range of antigens and epitopes than the antibody covers. Importantly, according to research, the respiration of SARS-CoV-2 specific T cell epitopes seems to be less sensitive to mutations present in VoC. So far, the degree of protection provided by T cells prevents re-infection and progression to severe COVID-19.

The researchers conducted a comprehensive, longitudinal, long-term immune study, including functional analysis, to evaluate the immune adaptability to different antigenic VoC. The research is currently available on the preprint server medRxiv* while awaiting peer review.

The COVID-19 immunization study was conducted 12 months after the PCR confirmed SARS-CoV-2 infection, and there was no community transmission in the cohort of 43 mild COVID-19 survivors in South Australia.

Immune to multi-isotype antibody response, homologous pseudotyped virus, homologous and VoC live virus serum neutralization activity, RBD-specific B cell population, and Spike and non-Spike SARS-CoV-2 specific CD8 and CD4 T cells In-depth evaluation conducted research on ancestral and VoC epitopes.

In the same cohort, the results were compared with age- and gender-matched COVID-19 naive, healthy individuals, and COVID-19 recovery 6 months after infection.

The receptor binding domain (RBD) of the SARS-CoV-2 Spike protein is the main target of neutralizing antibodies (nAbs), and nAb titers decrease within a few months after COVID-19 infection.

Analysis of the longitudinal effects of the humoral response showed that despite the high rate of receptor binding domain (RBD) seropositivity, the presence of circulating memory B cells and the homologous virus neutralizing activity during the recovery period of COVID19, the effects of VoC on VoC after 12 months The functional humoral response was significantly reduced. Infect.

Twelve months after mild COVID-19, >90% of convalescent patients were still seropositive for RBD-IgG, and 88.9% of patients had circulating RBD-specific memory B cells. Despite this, only 51.2% of the survivors had serum neutralizing activity against the homologous live SARS-CoV-2 virus, which was further reduced to 44.2% when tested on live B.1.1.7 (alpha), and for B.1.351 ( beta) 4.6% when tested), 11.6% for P.1 (gamma), and 16.2% for B.1.617.2 (delta) VoC.

Compared with non-spindle antigens, spike antigens and non-spindle-specific T cells are detected in more than 50% of recovered patients, and the frequency of spike antigens is higher.

Although in the recovery period of Spike "high responders" (the recovery period with Spike-specific CD4 and CD8 T cell responses, higher than the statistically determined threshold), the high prevalence and maintenance rate of Spike-specific T cells is much higher than 12 The healthy control level at month, T-cell function measured by cytokine expression after stimulation with Spike epitope corresponding to VoC was significantly reduced.

These data indicate that sub-optimal Spike-specific T helper cell functional responses are more likely to occur during the recovery period (infected with Wuhan-like variants) when encountering B.1.351 or B.1.617.2 but not other VoCs. This is similar to the humoral antibody response of COVID-19 survivors and vaccinators.

The study showed that although serum antibody, circulating memory B cell and T cell responses are persistent and maintainable at 12 months after the initial infection, COVID-19 recoveries have a functional Spike-specific T cell response and neutralization ability. There are obvious shortcomings. The current VoC.  

These results highlight the need to continue vaccination even in people who have previously reported mild COVID-19, and imply that due to the delay in vaccination, there is a risk of re-infection with severely virulent volatile organic compounds.

These studies are more relevant in the context of the current unequal distribution of vaccines globally, which keeps the vaccination rate in many developing countries from Africa, Southeast Asia, Central and South Asia, and Central America at 20-30% (full vaccination).

medRxiv publishes preliminary scientific reports that have not been peer-reviewed, and therefore should not be considered conclusive, guide clinical practice/health-related behaviors, or considered established information.

Published in: Medical Research News | Disease/Infection News

Tags: antibody, antibody, antigen, B cell, CD4, cell, cell death, coronavirus, coronavirus disease COVID-19, cytokine, frequency, homology, immunity, pandemic, protein, pseudovirus, receptor, respiratory tract , SARS, SARS-CoV-2, severe acute respiratory system, severe acute respiratory syndrome, spike protein, syndrome, T cell, vaccine, virus

Sreetama Dutt has completed her B.Tech. Received a bachelor's degree in biotechnology from SRM University in Chennai, India, and holds a master's degree in science. Doctor of Medical Microbiology, University of Manchester, UK. Initially decided to build her career in laboratory-based research, medical writing and communication happened to catch her when she least expected it. Of course, all is not a coincidence.

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