Toronto : Antibody levels in the blood of COVID-19 patients drop rapidly during the weeks after their bodies have cleared the novel coronavirus, and symptoms have subsided, according to a study.
In the absence of approved, effective treatments for COVID-19, some hospitals have been treating patients with severe symptoms with blood plasma from recovering patients.
If convalescent plasma is ultimately shown to have a clear benefit, the new study published in the journal mBio concluded that it needs to be collected during a specific window of time after recovery.
However, recovering patients can’t donate blood until at least 14 days after symptoms have subsided, to give the body time to clear viral particles.
“We don’t want to transfuse the virus, just transfuse the antibodies,” said Andres Finzi at the University of Montreal in Canada.
“But at the same time, our work shows that the capacity of the plasma to neutralise viral particles is going down during those first weeks,” Finzi said.
The spike protein of SARS-CoV-2 plays a crucial role in helping the virus grab and invade host cells.
Antibodies produced by the body’s immune system bind to a part of this protein and block the capacity of this “key” to engage with the host’s cellular “lock”, preventing the viral particle from infecting a cell host, said Finzi.
Previous studies suggest that antibodies against the SARS-CoV-2 spike protein peak 2 or 3 weeks after the onset of symptoms.
Findings from an earlier cross-sectional study by Finzi’s group, involving more than 100 patients, suggested that the ability of plasma to neutralise the virus decreased significantly between 3 and 6 weeks after symptom onset.
In the new longitudinal study, Finzi and his colleagues analysed blood samples collected at one-month intervals from 31 individuals recovering from COVID-19.
They measured levels of immunoglobulins that act against the coronavirus S protein and tested the ability of the antibodies to neutralise the virus.
The researchers observed variation on the level of individual patients but identified a consistent overall signal.
The levels of Immunoglobulins G, A, and M that target the binding site decreased between 6 and 10 weeks after symptoms began, they found.
During the same time period, the ability of the antibodies to neutralise the virus similarly fell, according to the researchers.
Understanding how the levels of antibodies change over time is critical not only for optimising the use of convalescent plasma but also for understanding vaccine efficacy and whether or not previously infected people are at risk of re-infection, they added.(AGENCIES)

Dubai : Mumbai Indians all-rounder Kieron Pollard feels that pace spearhead Jasprit Bumrah has taken over the mantle from Sri Lankan Lasith Malinga to become the lynchpin of the four-time IPL champions’ bowling attack.
After picking up the crucial wickets of KL Rahul, Mayank Agarwal and Nicholas Pooran in the stipulated 20 overs, Bumrah (3/24) bowled an excellent Super Over against Kings XI Punjab, conceding just five runs.
However, it was not enough as Mohammad Shami bowled an equally impressive over to lead the match to a second Super Over in which KXIP snatched a win at the Dubai International Stadium on Sunday.
“He’s a world-class cricketer. He has been number one in a couple of formats for a long period of time. He has learned and has grown leaps and bounds for us at Mumbai Indians…We have comfort in him,” Pollard said at the post-match press conference.
“A couple of years ago, we had a fit and fair Lasith Malinga and he (Bumrah) has taken over that mantle now,” he added.
Malinga, the highest wicket-taker in the IPL, opted out this year citing personal reasons.
Chasing five runs in the first Super Over, skipper Rohit Sharma and Quinton De Kock failed to take MI across the finish line.
In the second Super Over, Pollard and Hardik Pandya helped the defending champions score 11 runs.
“Obviously there are decision-makers to make the decision, you know we can look at those things and say that’s where we lost the game but we played a very good game of cricket. We batted well,” said Pollard.
Mumbai have lost two games via Super Overs. They were defeated by Royal Challengers Bangalore earlier in the tournament.
Their five-match winning streak broken by KXIP, the defending champions are placed second with 12 points.
“Just a matter of improvement, each and every time we step on the cricket field it is to improve and to do better. We will look back and analyse the game and we will come up with a better plan and hopefully get two points in the next game,” said the all-rounder.
KXIP pacer Chris Jordan, who bowled the second Super Over for his team, was delighted to be on the winning side.
“I feel like the way we have played a lot of our games this season, they could have been very easily ended with us on the winning side,” Jordan said during the post-match press conference.
“Unfortunately, that was not the case. I think from the last two games, specially the kind of team spirit and camaraderie we have shown as an entire team and entire franchise has been second to none.
“Just glad that we have a little bit of luck going our way now but we can’t rest on that,” he added.
Jordon conceded 11 runs of the second Super Over. Chris Gayle then hit the first ball bowled by Trent Boult for a six before opener Mayank Agarwal cracked successive fours as KXIP notched up an incredible win to keep their IPL play-off hopes alive.
The presence of the big-hitting Gayle in the playing XI has also inspired the team.
“You can see the impact the legend himself, Gayle, made in the last two games. Hitting a fifty after not playing for a while and then finish off the game in the Super Over for us. It is great to have, what I considered to be a great of the game, in our team. His energy is unbelievable,” Jordan said.
KXIP have got the better of MI and RCB in their last two games, however, KL Rahul and his men have been guilty of making their run chases too close and the pacer hopes his side can close in matches quicker.
“If we want to take it to the next level, we have got to keep doing simple things and hopefully finish off games a bit quick as well,” Jordan added. (AGENCIES)