Scientists are getting closer to understanding how the body releases antibodies and immune cells in response to the new coronavirus.
Because it is important: Natural immunity differs from that offered by vaccination, but offers clues for designing effective vaccines and therapies.
Driving the news: Earlier this week, the FDA released a guide to evaluating COVID-19 vaccines, emphasizing evaluation of safety and efficacy through clinical trials.
- That’s a standard procedure in developing a vaccine, But the agency duplicated its message in a climate of compressed timelines and as misinformation and skepticism about vaccines spread.
- FDA set a benchmark that a COVID-19 vaccine “would prevent the disease or decrease its severity in at least 50% of the vaccinated people.”
Where is it located: Vaccine development generally focuses on creating an antibody response to prevent infection from a virus. Here’s the latest on the antibody response to SARS-CoV-2, the virus that causes COVID-19:
- Most people who recover produce some antibodies to the virus, some of which are neutralizing antibodies that prevent the virus from entering cells.
- The amount and type of antibodies. seems to vary per person In a pre-print study, not yet peer-reviewed, researchers looked at convalescent plasma and found a wide range. Most had only a modest level of antibodies, and about 16% had no neutralizing antibodies, but 10% had very strong neutralizing activity, says Larry Luchsinger of the New York Blood Center and author of the study. They found that the differences couldn’t be attributed to age, blood type, or ethnicity, but the men had twice as much antiviral activity.
- In another recent peer-reviewed study, the amount of neutralizing antibodies was low in more than 99% of participants, but small amounts of antibodies binding to the virus receptor binding domain were found in all participants, suggesting that humans are “intrinsically capable” of generating antibodies that neutralize SARS-CoV-2, the authors wrote in Nature.
- People with severe infections. seems more likely to develop antibodies. “If you have evidence of more inflammation … then their antibody levels tend to be higher, “says Sanjeev Krishna, of St. George’s, University of London, who is co-author of a different pre-printed study that looked at levels of a different antibody (IgG) for the virus in 177 people over time.
- But not everyone produces antibodies, according to Several recent studies. Krishna said they found that between 2% and 8% of people infected with the virus did not test positive for IgG antibodies.
Between lines: For those who develop antibodies, it is too early to say how long the antibodies will last and whether they will confer protection, Daniel Lingwood of Harvard Medical School tells Axios.
- Krishna Study showed no decrease after almost two months.
- But a recent study published in Natural medicine Observing 37 asymptomatic and 37 symptomatic people, a decrease in IgG and neutralizing antibody levels was found after two or three months. (The amount was further reduced in people without symptoms.)
In the meantime, The body’s other immune actors to defend against viruses are receiving increasing attention.
- Auxiliary T cells help the body remembers the targets of the antibodies they make. The researchers are discovering that many people recovering from COVID-19 have helper T cells that target specific proteins in SARS-CoV-2.
Other type of T cells – killer T cells – is at the heart of the separate cellular immune response. These longer-term immune actors arrive a little later in the process and help control an infection and its severity by killing infected cells rather than protecting against infection.
- A small study of patients. Admitted to the ICU for COVID-19 complications found that the majority had SARS-CoV-2-specific killer T cells.
- Two of the healthy control subjects. Those who were not exposed to the virus also had low levels of T cells that react to SARS-CoV-2, “indicative of cross-reactivity due to prior infection with the ‘common cold’ coronavirus,” the authors write.
Not surprisingly, T cells are important, as they are known to help fight a host of different viral infections, says Mark Poznansky, director of the Center for Vaccines and Immunotherapy at Massachusetts General Hospital.
- Yes, but: It is still unknown how long T-cell responses last, whether they prevent infection with SARS-CoV-2, and whether the virus can evade them (and antibodies).
What to see: “We don’t know what protective immunity is, and therefore we don’t know exactly what must be recreated to protect it,” says Poznansky.
- T cells and the proteins they target Viruses must be considered, as should antibodies in vaccine design, he and other researchers urge.
- A successful vaccine will depend on whether it works in a clinical trial., not necessarily at the level of antibody response.
- “The unknowns of immunity they are canceled if it is really working clinically ”, adds Poznansky.
The bottom line: Antibodies are not the most important thing for the immune system, and they probably are not for COVID-19 vaccines.
Go deeper: Looking for clues to coronavirus in individual cells
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