NEW DELHI: Recent studies suggest that those recovering from Covid-19 may have antibodies for only a few months, a sign that long-term immunity is difficult to achieve, but several scientists dissipate the sadness and say it is too soon. to determine if individuals can contract the disease again.
Some special cells of the immune system may still offer protection against the disease, scientists said as questions arise as to whether people who have recovered from Covid-19 can get it again, even those whose antibodies progressively decrease as the days and weeks.
It is too early to say whether people with low levels of new levels of coronavirus-blocking antibodies (nAbs) after recovery are at risk of contracting Covid-19 disease on re-exposure to the virus, Vineeta Bal, an immunologist at the Institute Indian Science, Education and Research in Pune told PTI.
“This pandemic is only six to seven months old, and reports of people testing positive for the virus a second time after recovery are primarily from those who first became infected in January,” Bal said in a video interview.
The discussion, and unease among the laity after the news of the pandemic, escalated when a still peer-reviewed study, published on medRxiv last week, evaluated 90 patients recovered from Covid-19 in the UK and found that her nAbs decreased two-fold to 23-fold over a follow-up period of 18-65 days.
Another study, published last month in the journal Nature Medicine, surveyed antibody levels in patients with Covid-19, including those who showed no symptoms, and revealed that the nAbs lasted only two to three months after recovery.
While reports do come out of people who tested positive for virus re-exposure, it doesn’t necessarily mean that people who lose nAbs will develop the disease, said Bal, who was a member of the Prime Minister’s working group for women in science under the Ministry of Science. and Technology.
It may take a year to get enough data to confirm this.
While antibody levels, as indicated by the two studies, may decrease in recovered individuals, other players in the immune system may offer longer-lasting immunity.
“Some reports say that detectable T cells that can fight infection and prevent Covid-19 disease in re-exposure may offer protection,” said Bal.
Commenting on the implications of the studies, immunologist Satyajit Rath of the National Institute of Immunology in New Delhi said the findings are in line with how the human immune system interacts with coronaviruses, such as those that cause the cold. common.
In Rath’s opinion, as with other coronavirus infections, the more severe Covid-19 disease, the higher the maximum antibody levels in patients, as well as the tendency of their nAb levels to decrease in weeks or months.
Asymptomatic infected individuals produce very few nAbs to start with, and can recover and be protected by non-antibody-based mechanisms, he explained in an email interview.
“There is also some evidence that virus-specific T cells activate and expand in infected people, and may also provide accelerated recovery reinfection,” said Rath, adding a warning that there is no direct evidence of such a real causal cause. . relationship.
According to the immunologist, if the antibodies play an important role, the two studies could mean that long-term immunity, both individually and for the population, can be difficult to achieve.
Under such a scenario, he said, people can periodically re-infect themselves and the “virus can continue to spread” until effective vaccines come into use.
There is no good evidence on this yet, and it may or may not be the case, he said.
Another study, published in the journal Nature on Wednesday, also revealed the involvement of T cells.
The research, conducted by scientists at the Duke-Nus School of Medicine in Singapore, found that people infected with SARS-CoV-2, or the 2002-03 SARS pandemic virus or other coronaviruses, develop memory T cells.
These coronavirus-specific T cells could last more than 15 years in the body after people recover from the infection, and they can still proliferate once they find a protein from that virus.
According to this study, patients who recovered from the SARS virus 2002-03 17 years ago still possess virus-specific memory T cells that cross-reacted with the current pandemic virus.
However, whether such pre-existing T cells affect the clinical manifestation of Covid-19 has not yet been studied, said Nina Le Bert, co-author of this study.
“However, if an individual already has memory T cells that recognize the new infection, the adaptive immune response may start earlier and may reduce the severity of Covid-19,” he told PTI by email, wishing for more studies to confirm this. .
According to Le Bert, the immune system is complex, and the different types of cells generally complement each other.
“I think that both cellular and antibody immunity will be equally important,” he added.
Analyzing the implications of T cell involvement in vaccine development, Bal said: “For a vaccine to be effective, it needs to generate a reasonable concentration of nAbs and cytotoxic T cells.”
“Then they can kill the viruses on re-exposure,” he said, adding that the combination produces “two components of a perfect vaccine.”
He cautioned that vaccines that rely more on cell-mediated immunity may not be as effective in all individuals to the same extent, compared to those that increase the response of an antibody alone.
Bal explained that this is due to the genetic diversity of the global human population.
“Human cells have surface proteins called HLA antigens that are different for each individual. Therefore, there is no way to trigger a cell-mediated immune response in a universal vaccine that is generalizable to everyone,” he said. PTI VIS MIN
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Some special cells of the immune system may still offer protection against the disease, scientists said as questions arise as to whether people who have recovered from Covid-19 can get it again, even those whose antibodies progressively decrease as the days and weeks.
It is too early to say whether people with low levels of new levels of coronavirus-blocking antibodies (nAbs) after recovery are at risk of contracting Covid-19 disease on re-exposure to the virus, Vineeta Bal, an immunologist at the Institute Indian Science, Education and Research in Pune told PTI.
“This pandemic is only six to seven months old, and reports of people testing positive for the virus a second time after recovery are primarily from those who first became infected in January,” Bal said in a video interview.
The discussion, and unease among the laity after the news of the pandemic, escalated when a still peer-reviewed study, published on medRxiv last week, evaluated 90 patients recovered from Covid-19 in the UK and found that her nAbs decreased two-fold to 23-fold over a follow-up period of 18-65 days.
Another study, published last month in the journal Nature Medicine, surveyed antibody levels in patients with Covid-19, including those who showed no symptoms, and revealed that the nAbs lasted only two to three months after recovery.
While reports do come out of people who tested positive for virus re-exposure, it doesn’t necessarily mean that people who lose nAbs will develop the disease, said Bal, who was a member of the Prime Minister’s working group for women in science under the Ministry of Science. and Technology.
It may take a year to get enough data to confirm this.
While antibody levels, as indicated by the two studies, may decrease in recovered individuals, other players in the immune system may offer longer-lasting immunity.
“Some reports say that detectable T cells that can fight infection and prevent Covid-19 disease in re-exposure may offer protection,” said Bal.
Commenting on the implications of the studies, immunologist Satyajit Rath of the National Institute of Immunology in New Delhi said the findings are in line with how the human immune system interacts with coronaviruses, such as those that cause the cold. common.
In Rath’s opinion, as with other coronavirus infections, the more severe Covid-19 disease, the higher the maximum antibody levels in patients, as well as the tendency of their nAb levels to decrease in weeks or months.
Asymptomatic infected individuals produce very few nAbs to start with, and can recover and be protected by non-antibody-based mechanisms, he explained in an email interview.
“There is also some evidence that virus-specific T cells activate and expand in infected people, and may also provide accelerated recovery reinfection,” said Rath, adding a warning that there is no direct evidence of such a real causal cause. . relationship.
According to the immunologist, if the antibodies play an important role, the two studies could mean that long-term immunity, both individually and for the population, can be difficult to achieve.
Under such a scenario, he said, people can periodically re-infect themselves and the “virus can continue to spread” until effective vaccines come into use.
There is no good evidence on this yet, and it may or may not be the case, he said.
Another study, published in the journal Nature on Wednesday, also revealed the involvement of T cells.
The research, conducted by scientists at the Duke-Nus School of Medicine in Singapore, found that people infected with SARS-CoV-2, or the 2002-03 SARS pandemic virus or other coronaviruses, develop memory T cells.
These coronavirus-specific T cells could last more than 15 years in the body after people recover from the infection, and they can still proliferate once they find a protein from that virus.
According to this study, patients who recovered from the SARS virus 2002-03 17 years ago still possess virus-specific memory T cells that cross-reacted with the current pandemic virus.
However, whether such pre-existing T cells affect the clinical manifestation of Covid-19 has not yet been studied, said Nina Le Bert, co-author of this study.
“However, if an individual already has memory T cells that recognize the new infection, the adaptive immune response may start earlier and may reduce the severity of Covid-19,” he told PTI by email, wishing for more studies to confirm this. .
According to Le Bert, the immune system is complex, and the different types of cells generally complement each other.
“I think that both cellular and antibody immunity will be equally important,” he added.
Analyzing the implications of T cell involvement in vaccine development, Bal said: “For a vaccine to be effective, it needs to generate a reasonable concentration of nAbs and cytotoxic T cells.”
“Then they can kill the viruses on re-exposure,” he said, adding that the combination produces “two components of a perfect vaccine.”
He cautioned that vaccines that rely more on cell-mediated immunity may not be as effective in all individuals to the same extent, compared to those that increase the response of an antibody alone.
Bal explained that this is due to the genetic diversity of the global human population.
“Human cells have surface proteins called HLA antigens that are different for each individual. Therefore, there is no way to trigger a cell-mediated immune response in a universal vaccine that is generalizable to everyone,” he said. PTI VIS MIN
MIN MIN 07161740 NNNN
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