A team of researchers in the U.S. recently conducted a study to examine whether natural infection-induced or vaccine-induced neutralizing antibodies are capable of eliminating the risk of recently emerged Indian variant (B.1.617.1) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
The findings reveal that sera obtained from convalescent individuals and those immunized with mRNA-based coronavirus disease 2019 (COVID-19) vaccines are capable of neutralizing the Indian variant, which has recently been categorized as the Variant of Concern (VOC) by the World Health Organization (WHO).
The study - which was conducted by researchers at Emory University, the University of Stanford and the National Institute of Allergy and Infectious Diseases (NIAID) - is currently available on the bioRxiv* preprint server.
The deadly outbreak of COVID-19 has placed a significant burden on the healthcare and economic structures of many countries globally. With the progression of the pandemic, novel variants of SARS-CoV-2 with multiple spike mutations are emerging and persisting, and thus, placing the global population in a tremendous crisis. Because of significantly higher infectivity and less sensitivity to antibody-mediated neutralization, some of these variants have already been designed as VOCs by the WHO.
Recently, India has been affected severely by a second wave of COVID-19 pandemic because of a newly emerged VOC (B.1.617.1) that exhibits potentially high infectivity and immune evasion ability. Compared to previously circulating SARS-CoV-2 variants, the B.1.617.1 variant contains multiple mutations in specific spike regions, including the N-terminal antigenic supersite, the receptor-binding domain (RBD), and the polybasic furin cleavage site at the S1/S2 boundary. Overall, this has raised a global concern as the B.1.617.1 variant has been identified in many countries outside India.
In the current study, the scientists investigated whether serum samples obtained from SARS-CoV-2-infected or vaccinated individuals could neutralize the Indian VOC in live virus neutralization assays.
For the live virus neutralization assay, serum samples were obtained from 24 COVID-19 recovered individuals and 25 vaccinated individuals. Of all vaccinated individuals, 15 received the Moderna COVID-19 vaccine, and 10 received the Pfizer/BioNTech vaccine.
Specifically, the convalescent serum samples were collected after 31 to 91 days of symptom onset. Similarly, the vaccinated serum samples were collected 35 – 51 days after the 2nd dose of Moderna vaccine and 7 – 27 days after the 2nd dose of Pfizer/BioNTech vaccine.
The B.1.617.1 variant of SARS-CoV-2 was isolated from the residual mid turbinate swab sample of a COVID-19 patient in Stanford, California.
Compared to wildtype SARS-CoV-2, the B.1.617.1 variant showed lower sensitivity to neutralization by the serum samples obtained from both convalescent and vaccinated individuals.
Specifically, the convalescent serum samples exhibited the average neutralizing antibody titers of 514 and 79 against the wildtype virus and the B.1.617.1 variant, respectively. However, the neutralizing antibody titers against the B.1.617.1 variant could not be detected in 5 convalescent serum samples.
The serum samples obtained from Moderna-vaccinated individuals showed the average neutralizing antibody titers of 1332 and 190 against the wildtype virus and the B.1.617.1 variant, respectively.
Similarly, the Pfizer/BioNTech-vaccinated serum samples exhibited the average antibody titers of 1176 and 164 against the wildtype virus and the variant, respectively.
The study findings indicate that compared to the wildtype virus, the B.1.617.1 variant is significantly resistant (6.8-fold) to neutralization by antibodies developed in response to natural infection or vaccination. Despite such lower sensitivity, about 79% of convalescent sera and 100% of vaccinated sera showed considerable effectiveness in neutralizing the B.1.617.1 variant.
Taken together, the study highlights the effectiveness of mRNA-based COVID-19 vaccines in inducing neutralizing antibodies against newly emerging SARS-CoV-2 variants like B.1.617.1.
bioRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.