Lasting antibody and T cell responses to SARS-CoV-2 in COVID-19 patients three months after infection.

The dynamics, duration, and nature of immunity produced during SARS-CoV-2 infection are still unclear. Here, we longitudinally measured virus-neutralising antibody, specific antibodies against the spike (S) protein, receptor-binding domain (RBD), and the nucleoprotein (N) of SARS-CoV-2, as well as T cell responses, in 25 SARS-CoV-2-infected patients up to 121 days post-symptom onset (PSO). All patients seroconvert for IgG against N, S, or RBD, as well as IgM against RBD, and produce neutralising antibodies (NAb) by 14 days PSO, with the peak levels attained by 15-30 days PSO. Anti-SARS-CoV-2 IgG and NAb remain detectable and relatively stable 3-4 months PSO, whereas IgM antibody rapidly decay. Approximately 65% of patients have detectable SARS-CoV-2-specific CD4+ or CD8+ T cell responses 3-4 months PSO. Our results thus provide critical evidence that IgG, NAb, and T cell responses persist in the majority of patients for at least 3-4 months after infection.

Robust Antibody and T Cell Responses in COVID-19 Patients Six Months After Infection (preprint)

Determining the longevity of natural immunity after SARS-CoV-2 infection is critical for understanding immune protection and optimizing vaccine design. Over six months have been passed since the emergence of COVID-19 in China. We evaluated humoral and cellular responses in 418 patients six months after infection. 95.9% and 98.1% of the patients maintained SARS-CoV-2-specific IgG and neutralizing antibodies. All severe patients were positive for IgG and neutralizing antibodies and had significantly higher titers than mild and moderate patients as well as asymptomatic individuals. The patients had a more robust SARS-CoV-2-specific CD4+ T cell response than CD8+ T cells six months after infection. Unexpectedly, sustained immune activation was observed, which displayed as the evaluated proinflammatory monocytes, non-classical NK cells, CD4+ Treg cells, and activated CD4+ T cells. Our findings indicate that SARS-CoV-2 gives rise to persisting and robust protective immunity, which provides a promising sign for prevention from reinfection and vaccination strategy.Funding: This work was supported by grants from the Natural Science Foundation of China (81773494 to M.J.M.), the National Major Project for Control and Prevention of Infectious Disease of China (2017ZX10303401-006 to M.J.M.), the Special National Project on Investigation of Basic Resources of China (2019FY101502 to M.J.M.).Conflict of Interest: The authors declare no competing interests.Ethical Approval: All patients provided written informed consent. The study was conducted following the Declaration of Helsinki, and the Institutional Review Board of the Academy of Military Medical Sciences approved the study protocol (IRB number: AF/SC-08/02.46).

Lymphocytopenia and neutrophilia deteriorate at the lowest oxygenation index timepoint in COVID-19 patient (preprint)

BackgroundCoronavirus disease 2019 (COVID-19) spread throughout the world and caused hundreds of thousands of infected people to death. However, the pathogenesis of severe acute respiratory syndrome coronavirus-2 (SARS COV-2) is poorly understood. The objective of this study is to retrospectively explore the pathogenesis of COVID-19 from clinical laboratory findings, taking disease progression into account.MethodsA single-centered, retrospective study was carried out, which included moderate (n=76) and severe COVID-19 cases (n=22). The difference of laboratory findings from blood routine examination and hepatorenal function test were retrospectively evaluated between the state of moderate and severe. The disease progression was indicated by oxygenation index.ResultsAge is a risk factor for disease progression from moderate to severe. Lymphocytopenia, neutrophilia, liver and kidney function decreasement occurred in severe patients on admission, compared with moderate patients. Lymphocytopenia and neutrophilia deteriorated at the lowest oxygenation index timepoint in the severe patients. And the oxygenation index was associated with ratio of lymphocyte and neutrophil in COVID-19 patients.ConclusionsLymphocytopenia and neutrophilia, which deteriorate in the progression of severe patients, are the main pathogenesis of COVID-19. More measures need to be taken to control lymphocytopenia and neutrophilia in severe COVID-19. Oxygenation index presented potentiality as predictor on the progression of COVID-19.