Protective immunity to SARS-CoV-2 could last eight months or more



Colorized scanning electron micrograph of an apoptotic (green) cell heavily infected with SARS-COV-2 virus particles (yellow), isolated from a patient sample. Image taken at the NIAID Integrated Research Center (IRF) in Fort Detrick, Maryland. Credit: NIH / NIAID

New data suggests that almost all COVID-19 survivors have the necessary immune cells to fight reinfection.

The results, based on analyzes of blood samples from 188 patients with COVID-19, suggest that responses to the novel coronavirus, SARS-CoV-2, of all major players in the “adaptive” immune system, which is learning to fight specific pathogens, can last for at least eight months after the onset of symptoms of the initial infection.

“Our data suggest that the immune response is there – and remains,” Professor LJI Alessandro Sette, Dr Biol. Sci., Who co-led the study with Professor LJI Shane Crotty, Ph.D., and Assistant Research Professor LJI Daniela Weiskopf, Ph.D.

“We measured the antibodies, memory B cells, helper T cells and killer T cells at the same time,” says Crotty. “As far as we know, this is the largest study ever, for any acute infection, that has measured these four components of immune memory.”

The results, published in the January 6, 2021 online edition of Science, could mean that COVID-19 survivors have protective immunity against serious illnesses caused by the SARS-CoV-2 virus for months or even years after infection.

The new study helps clarify some data regarding COVID-19 from other laboratories, which has shown a dramatic drop in anti-COVID antibodies in the months following infection. Some feared that this drop in antibodies meant that the body would not be equipped to defend itself against reinfection.

Sette explains that a drop in antibodies is quite normal. “Of course, the immune response decreases to some extent over time, but that’s normal. This is what immune responses do. They have a first phase of ramping up, and after this fantastic expansion, the immune response contracts somewhat and reaches steady state, ”says Sette.

Researchers have found that antibodies specific to the virus persist in the bloodstream for months after infection. It is important to note that the body also has immune cells called memory B cells. If a person encounters SARS-CoV-2 again, these memory B cells could reactivate and produce antibodies against SARS-CoV-2 to fight reinfection.

The SARS-CoV-2 virus uses its “spike” protein to initiate infection in human cells, so the researchers looked for memory B cells specific for the SARS-CoV-2 peak. They found that peak-specific memory B cells actually increased in the blood six months after infection.

COVID-19 survivors also had an army of T cells ready to fight reinfection. The memory CD4 + “helper” T cells lingered, ready to trigger an immune response if they saw SARS-CoV-2 again. Many CB8 + memory “killer” T cells also remained, ready to destroy infected cells and stop reinfection.

Dr Daniela Weiskopf discusses the study. Credit: Jenna Hambrick, La Jolla Institute of Immunology

The different parts of the adaptive immune system work together, so seeing anti-COVID antibodies, memory B cells, CD4 + memory T cells, and CD8 + memory T cells in the blood more than eight months after infection is good. sign.

“This implies that there’s a good chance that people will have protective immunity, at least against serious illness, during that period of time, and probably well beyond,” Crotty says.

The team warns that protective immunity varies widely from person to person. In fact, researchers have seen a 100-fold range in the magnitude of immune memory. People with poor immune memory may be vulnerable to a recurring case of COVID-19 in the future, or they may be more likely to infect other people.

“There are people who are way below the amount of immune memory they have, and maybe those people are a lot more likely to re-infect themselves,” Crotty says.

“It appears that people who have been infected will have some degree of protective immunity against reinfection,” Weiskopf adds. “What protection remains to be established.”

The fact that immune memory against SARS-CoV-2 is possible is also a good sign for vaccine developers. Weiskopf points out that the study followed responses to natural infection with SARS-CoV-2, not immune memory after vaccination.

“It is possible that immune memory will be similar in the long term after vaccination, but we will have to wait for the data to arrive to be able to say for sure,” Weiskopf says. “Several months ago, our studies showed that natural infection elicited a strong response, and this study now shows that responses last. Vaccine studies are in their infancy and have so far been associated with strong protection. We hope that a similar pattern of long-lasting responses will also emerge for vaccine-induced responses.

Researchers will continue to analyze samples from patients with COVID-19 in the coming months and hope to track their responses 12 to 18 months after symptoms appear.

“We also do very detailed scans with much, much higher granularity on the elements of the virus recognized,” says Sette. “And we plan to evaluate the immune response not only after natural infection, but after vaccination.”

The team is also working to understand how immune memory differs in people of different ages and how this can influence the severity of COVID-19 cases.

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More information:
Jennifer M. Dan et al, Immunological memory of SARS-CoV-2 evaluated up to 8 months after infection, Science (2021). DOI: 10.1126 / science.abf4063

Provided by La Jolla Institute for Immunology

Quote: Protective immunity to SARS-CoV-2 could last eight months or more (2021, January 6) retrieved January 8, 2021 from months.html

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