Patna: As the novel coronavirus continues to wreak havoc worldwide, scientists and health researchers are working at breakneck speed to find a safe, effective treatment and vaccine against COVID-19, the disease caused by the SARS-CoV-2 virus. Perhaps, much research has been focusing on antibodies from the blood of people who have recovered from COVID-19. Researchers have found that people who had recovered from coronavirus infection had potent antibodies. However, doctors at AIIMS-Patna have reportedly found that around 20-25 per cent of people who had been cured of COVID-19 have weak or no antibodies against the SARS-CoV-2 virus.

Researchers said antibodies are molecules that are produced by the immune system to fight infection. Several vaccine candidates that are being tested all over the world are designed to trigger the human body to produce antibodies to the SARS-CoV-2 spike protein.  It is claimed that antibodies that recognise and bind to the spike protein can prevent the deadly virus from infecting human cells.

According to a TOI report, doctors found that about 80-100 (out of 400 cured patients) did not show the presence of antibodies against the SARS-CoV-2 or it was less than the level required for protection from the virus. Doctors made this random discovery as these 400 people who had recovered from Covid-19 voluntarily came forward to donate convalescent plasma and were tested for specific antibodies using the IgG Elisa Test.

The ICMR-Delhi guideline notes that people who had been cured of CVOID-19 having a minimum of 1.12 AU/ ml antibody can donate blood for the convalescent plasma therapy. Plasma therapy that uses blood from people who’ve recovered from the disease to help others recover.

“Of the 400 cured patients, around 80-100 did not show the presence of specific antibodies against the virus or it was less than 1.12 AU (arbitrary unit)/ ml,” the report, citing Dr Sanjay Kumar, nodal officer for COVID- 19 at AIIMS-Patna, said.

Dr Kumar told a newspaper that the level of IgG was low in those suffering from mild symptoms or asymptomatic cured patients. However, IgG levels spiked in recovered patients with more critical, severe and moderate symptoms.

“Several studies conducted by scientists and researchers also revealed the same in their research,” added Dr Kumar.

“Immune response that produces antibodies to protect against the virus is high in people, who are more infectious to the disease. Secondly, some people have recovered before the ideal time (28 days) for the development of antibody after cessation of symptoms. Lastly, the IgG level depends on the immune system of individuals. So, the cured asymptomatic and mild symptoms patients need to be careful, because of chances of reinfection,” he said as he underlined three possible reasons behind the difference in antibody level observed in cured patients.

Potent antibodies found in cured COVID-19 patients

A study published in Nature Medicine reported that antibodies developed against COVID-19 begin to decrease in number, just 2-3 months after infection. Meanwhile, a study published on June 18 in Nature showed that potent infection-blocking antibodies were found in people who recovered from COVID-19, although most cured patients had low levels of antibodies to SARS-CoV-2 in their blood. Researchers believe that careful analsysis of antibodies may provide guidance for developing vaccines and antibodies as treatments for novel coronavirus infection.