ABSTRACT
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.
Subject(s)
Antibodies, Viral/immunology , COVID-19/immunology , COVID-19/virology , SARS-CoV-2/physiology , T-Lymphocytes/immunology , Adult , Antibodies, Neutralizing/blood , Antibodies, Neutralizing/immunology , CD4-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/immunology , COVID-19/blood , Female , Humans , Immunoglobulin G/blood , Immunoglobulin G/immunology , Immunoglobulin M/blood , Immunoglobulin M/immunology , Immunologic Memory , Interferon-gamma/metabolism , Kinetics , Leukocyte Common Antigens/metabolism , Male , Middle Aged , Phenotype , Receptors, CCR7/metabolismABSTRACT
SARS-CoV-2 nucleocapsid (N) protein has been proposed as a good vaccine target. N-specific T cells were observed in SARS-CoV-2 N immunized mice and COVID-19 convalescents. It is of importance to identify the T cell responses triggered by SARS-CoV-2 N protein. Intradermal immunization with SARS-CoV N protein was demonstrated to elicit non-protective T cell responses which may be avoided by intranasal vaccination. Therefore, we conducted intranasal vaccination of BALB/c mice with recombinant adenovirus type-5 expressing SARS-CoV-2 N protein. Such procedure induced CD8 T cell responses in the lung. Meanwhile CD4 T cell responses were observed in the spleen, which was associated with robust antibody production. Our study further supports the notion that SARS-CoV-2 N protein can work as a target for vaccine development.