Recently recovered COVID-19 patients produce various virus-specific antibodies

Most recently discharged patients who recently recovered from COVID-19 produce virus-specific antibodies and T cells, suggesting a study published May 3 in the journal Immunity, But the reactions of different patients are not all the same. The 14 patients investigated in the study showed a widespread immune response, but the results of 6 of them evaluated 2 weeks after discharge suggested that the antibody was maintained for at least that period. Additional results from the study indicate which part of the virus is most effective in triggering these immune responses and therefore should be targeted in potential vaccines.

It is not clear why immune responses vary greatly from country to country patient. The authors state that this variability may be related to the initial amount of virus encountered by patients, their physical condition, or their microbiota. Other open questions include whether these immune responses protect against COVID-19 upon reexposure to SARS-CoV-2, and the T cell types activated by viral infection. The laboratory tests used for detection are antibody Human SARS-CoV-2 requires further validation to determine accuracy and reliability.

“These findings suggest that both B and T cells are involved in immune-mediated protection against viral infections,” said Chen Dong, a collaborator at Tsinghua University. “Our study provided a basis for further analysis of protective immunity and an understanding of the mechanisms underlying the development of COVID-19, especially in severe cases. It also affects the design of the vaccine. “

Little is known about the protective immune response elicited by the disease-causing virus, SARS-CoV-2, so addressing this knowledge gap could accelerate the development of effective vaccines. Co-researcher Cheng-Feng Qin added. Academy of Military Medical Sciences in Beijing, China.

With this goal in mind, the researchers compared the immune response of 14 COVID-19 patients who were recently cleared of the virus with those of 6 healthy donors. Eight patients were newly discharged, and the remaining six were follow-up patients who were discharged 2 weeks before analysis. Specifically, the researchers who collected Blood sample They then evaluated the levels of immunoglobulin M (IgM) antibodies that first appeared in response to infections and the highest levels of immunoglobulin G (IgG) antibodies. General type Found in the blood circulation.

Both newly discharged and follow-up patients had SARS-CoV-2 nucleocapsid protein encapsulating viral genomic RNA and IgM antibody binding to the receptor binding domain of the S protein compared to healthy controls. We have shown high levels of IgG antibodies (S-RBD), which bind to host cell receptors during the viral entry process. Taken together, these findings indicate that COVID-19 patients can mount an antibody response to the SARS-CoV-2 protein, suggesting that these antibodies are maintained for at least 2 weeks after discharge.

In addition, five newly discharged patients had high levels of neutralizing antibodies that bound to pseudoviruses expressing the SARS-CoV-2 S protein. Neutralizing antibodies prevent infectious particles from interacting with host cells. In addition, all but one follow-up patient had detectable neutralizing antibodies against the pseudovirus.

Five newly discharged patients had higher levels of T cells secreting interferon gamma (IFNγ), a signaling molecule that plays a key role in immunity, compared to healthy controls response For SARS-CoV-2 nucleocapsid protein. These are the same patients with high levels of neutralizing antibodies. In addition, three newly discharged patients showed detectable levels of IFNγ-secreting T cells specific for SARS-CoV-2 main protease, a protein that plays a key role in viral replication. In contrast, seven newly discharged patients showed detectable levels of IFNγ-secreting T cells specific for SARS-CoV-2 S-RBD. In contrast, high concentrations of IFNγ-secreting T cell Reacts with nucleocapsid proteins, major proteases, and S-RBD.

One finding with potential clinical relevance was that the amount of neutralizing antibodies was positively associated with IgG antibodies to S-RBD, but not with antibodies that bind to the nucleocapsid protein. . In addition, S-RBD induced both antibody and T cell responses. “Our results suggest that S-RBD is a promising target for the SARS-CoV-2 vaccine,” says Fang Chen, a co-senior research author at Chui Yang Liu Hospital at Tsinghua University. . “But our findings need to be further confirmed in a large cohort of COVID-19 patients.”