A study has shown that people who have been down with mild infection and have had less viral load might be vulnerable to some of the most severe strains of the SARS-CoV-2 virus as compared to patients with severe COVID19 who have been hospitalized, and those who have been vaccinated with two doses. The Variants of concern (VOCs) such as B.1.1.7, B.1.351, and P.1 are some of the most severe strains of the virus. The study has been done by a team of experts from the Netherlands and the US. The study is being peer-reviewed at present. The COVID19 pandemic has claimed the lives of 3.5 million people across the world and has infected around 17.1 million people across the globe. It has become the most deadly pandemic in modern history. Experts have said that the frequent emergence of many strains of the SARS-CoV-2 virus has been putting humans under serious threat.
The World Health Organization (WHO) has tagged some viral strains of the virus as Variants of concern (VOCs) due to their immune dodging ability and a higher rate of infection. The VOCs such as B.1.1.7, B.1.351, and P.1 have been found in the UK, South Africa, and Brazil respectively for the first time. These strains have started spreading around the globe soon after their emergence. The B.1.1.7 variant has been found in 132 countries in the world. The South African variant known as B.1.351 has been detected in 82 countries. The P.1 variant has been spreading in 52 nations across the world.
Scientists have said that all three VOCs share a common trait in the spike receptor-protein binding domain (RBD) that is known as the N501Y mutation. They have said that the mutation shoots up the RBD affinity of the virus for the ACE2 receptor in humans. The E484K mutation that is found in the B.1.351 and P.1 variants helps the virus to evade antibody-induced neutralization. In the new study, the authors have compared the immune evasion abilities of these three VOCs. They have tried to find whether these strains can dodge neutralization induced by monoclonal therapeutic antibodies and polyclonal antibodies derived from infection and COVID19 shots. Experts have taken serum samples from 69 COVID19 patients around 4 to 6 weeks after the onset of symptoms for an antibody test.
They have taken an extra set of serum samples from 50 health care workers who have been vaccinated against COVID19. The serum samples of these health care workers have been taken four weeks after their second dose. The volunteers of the study have been given mRNA based shot that has been made by Pfizer and BioNtech. Scientists have created the spike proteins of the SARS-CoV-2 virus and its three VOCs. They have used multiple protein microarrays to test the binding antibody response of serum samples. Experts have used lentiviral-based pseudoviruses of the wild-type virus and three VOCs to find out defusing ability of sera.
The authors of the study have said that the spike binding ability of convalescent sera has been reduced by 2.4 times, 3 times, and 4 times for B.1.1.7, B.1.351, and P.1 strains respectively as compared to the wild type SARS-CoV-2. They have said that there has been a major difference in the levels of spike-binding antibodies in severely ill hospitalized COVID19 patients and those with mild infection who have not been hospitalized. In the study, a similar level of binding antibody has been seen in people who have been given the vaccine and those who have been admitted to the hospitals. The level of binding antibody has been 4 to 11 times greater as compared to people with a mild infection, said the experts. All these findings have been steady with all VOCs that have been tested in the study. The authors have said that nearly 96 percent of recovery sera and 100 percent of vaccinated sera have shown full defusing ability against the original strain of the virus. On the other hand, all tested sera have shown a major decline in neutralization strength against the VOCs. The study has noted that patients who have been down with mild infection have shown 4 times decline in neutralizing titers against the B.1.351 strain.
Patients who have been severely ill have shown a 7 times decline in defusing titers. While people who have been given the shots have shown a 5 times reduction in defusing titers against the B.1.351 strain. Scientists have noted that all patients with mild infection have shown defusing titers against wild-type virus and the B.1.1.7 variant. Around 39 percent of them have not been able to defuse the B.1.351 strain. Nearly 34 percent of them have failed to kill the P.1 strain. All hospitalized patients and vaccinated people have been able to retain some defusing ability against all VOCs. Experts have said that preclinical tested anti-RBD and anti-NTD, (non-terminal domain) antibodies have shown a major decline in binding ability against the B.1.351 and P.1 strains as compared to the wild-type virus. Nevertheless, some SARS-CoV cross-reactive anti-RBD monoclonal antibodies have been able to keep up similar binding kinetics to all VOCs. The study has shown that the E484K mutation along with other mutations such as K417N and K417T has a higher effect on the binding of monoclonal anti-RBD antibodies.
Experts have said that only 5 out of 11 tested monoclonal anti-RBD antibodies have been able to keep up defusing ability against the South African and Brazilian strains. On the other hand, both anti-NTD antibodies have not been able to kill the South African strain. The authors of the study have said people who have been treated in hospitals and those who have been given both doses of the shot might have protection against all three VOCs of the virus even after having low binding and defusing titers.
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