LOS ANGELES, Dec.25: The body’s protective antibodies against the novel coronavirus target a different part of the virus in severe cases of COVID-19 than in mild forms of the disease and significantly decrease within several months of infection, a new study says. .
According to scientists, including those from Stanford University in the United States, the findings shed new light on the links between the course of the disease and a patient’s immune response.
The research, published in the journal Science Immunology, found that people with severe COVID-19 have lower levels of antibodies that target the spike protein used by the virus to enter human cells than those that target the proteins. of the inner shell of the SARS-CoV-2 virus.
“This is one of the most comprehensive studies to date on the immune response of antibodies to SARS-CoV-2 in people across the spectrum of disease severity, from asymptomatic to fatal,” said Scott Boyd, co-author of the Stanford University study. .
“We evaluated multiple time points and sample types and also analyzed the viral RNA levels in patients’ nasopharyngeal swabs and blood samples. It’s one of the first looks at this disease, “Boyd said.
In the study, scientists studied 254 people with asymptomatic, mild, or severe COVID-19 who were identified via routine testing or occupational health screening at Stanford Health Care or who arrived at a Stanford Health Care clinic with symptoms. of COVID-19.
According to the scientists, 25 of the people with symptoms were treated on an outpatient basis, 42 were hospitalized outside the intensive care unit and 37 were treated in the intensive care unit.
The study found that 25 people in the study died from the disease.
From analyzing the patient samples, the scientists said antibodies that recognize and bind to the spike protein prevent the virus from infecting cells.
However, they said that antibodies that recognize other viral components are unlikely to prevent viral spread.
The researchers evaluated the levels of three types of antibodies – IgG, IgM and IgA – in the patients.
They estimated the proportions of antibodies that targeted the viral peak protein or the virus’s inner shell as the disease progressed and patients recovered or fell ill.
“We found that disease severity correlates with the ratio of antibodies that recognize spike protein domains to other non-protective viral targets,” Boyd said.
“Those people with mild disease tended to have a higher percentage of anti-spike antibodies, and those who died from their illness had more antibodies that recognized other parts of the virus,” he added.
While the study identified trends among a group of patients, the scientists said there is still substantial variability in the immune response mounted by individual patients, particularly those with severe disease.
They believe that antibody responses are likely not the only determinant of someone’s outcome.
“Among people with serious illnesses, some die and others recover. Some of these patients mount a vigorous immune response and others have a more moderate response, ”Boyd said.
“So, a lot of other things are happening. Other branches of the immune system are also involved. It is important to note that our results identify correlations but do not demonstrate causality, “he added.
The scientists also found that people with asymptomatic and mild illnesses had lower overall antibody levels than those with severe illness.
IgM and IgA levels steadily decreased in patients after recovering to low or undetectable levels for approximately one to four months after symptom onset, and IgG levels decreased significantly.
“This is fairly consistent with what has been seen with other coronaviruses routinely circulating in our communities to cause the common cold,” Boyd said. (PTI)