A team of researchers recently cross-tested severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies to assess their neutralization activity against different variants. The team recently released their findings as a preprint on the medRxiv* server.

SARS-CoV-2, the causative agent of the coronavirus disease 2019 (COVID-19) pandemic, has infected more than 163 million individuals and claimed more than 3.4 million lives since it was first identified in December 2019. Despite the enormous ongoing vaccine roll-out across the world, one major concern among scientists and healthcare givers is the duration of the protective immunity and its specificity.

Many aspects of the long-term clinical and immunological consequences of anti-SARS-CoV-2 antibodies against the infecting strain and re-infection by the SARS-CoV-2 variants are unclear.

To evaluate the cross-immunity between the viral strains, the researchers measured and compared the neutralization capacity of antibodies in sera from convalescent individuals previously infected with SARS-CoV-2 strains circulating at the beginning of the pandemic with genetic variant strains present at late pandemic stages.

The scientists evaluated whether anti-SARS-CoV-2 antibodies induced by SARS-CoV-2 B.1.1.28 virus strain can neutralize the P.1 SARS-CoV-2 variant. They found that majority of the patients infected with SARS-CoV-2 strain B.1.1.28 developed neutralizing antibodies that were also effective against the P.1 variant in vitro, without having prior exposure to this strain.

The P.1 lineage, a novel SARS-CoV-2 variant, was identified in Manaus, Brazil, at the beginning of November 2020. This variant has 17 mutations, including three in the gene coding for the spike protein (K417T, E484K and N501Y). These mutations result in antigenic changes in the spike protein, which could reduce the efficacy of neutralizing antibodies generated against a previous SARS-CoV-2 strain.

The P.1 SARS-CoV-2 variant is spreading and exacerbating the pandemic in Brazil. Under these circumstances, the researchers in this study tested if the neutralizing antibody responses induced by infection with the SARS-CoV-2 virus that was dominant at the beginning of the pandemic remained effective when tested against the P.1 lineage.

The study found neutralizing antibodies that were generated following infection with the SARS-CoV-2 B.1.1.28 were effective in vitro, against the SARS-CoV-2 P.1 variant, in a cohort of 60 SARS-CoV-2 infections confirmed patients. These patients were participants in The Corona São Caetano Program, a primary care initiative offering COVID-19 care to all residents of São Caetano do Sul, Brazil. They presented mild to moderate disease symptoms lasting for 3 days and required no hospitalization.

The researchers conclude, “Thus, previous infections with the ancestral strains will apparently provide a sufficient degree of protection from the P.1 variant in the majority of previously infected individuals.”

While discussing the possibilities of anamnestic antibody response following re-exposure to the same or different strains of the virus and the difference in neutralization antibody titers, the researchers also pointed to the limitations of their study.

First, this study includes a small cohort of patients who manifested mild to moderate episodes of COVID-19. This calls for expanding the study to determine if individuals with more severe disease differed in the occurrence or titer of antibodies cross-reactive to P.1.

The second limitation is the time length of the study: the neutralizing antibody titers were assessed only for the first six weeks after the initial infection. The researchers recommend extending this study to later time points to gain valuable information.

The third important limitation of the study is the lack of including other components of the immune response, such as cell-mediated immunity.

Though large prospective epidemiologic studies are required to establish the role of neutralizing antibodies in preventing or minimizing infection, by SARS-CoV-2 variants in previously exposed individuals, it will vary depending on the changes in the spike protein antigenicity.

This significant study provides valuable insights into the efficacy, kinetics and durability of protective immune responses against a different variant during a pandemic and can guide rational vaccine design.

Our data provides the encouraging information that a previous SARS-CoV2 infection likely provides a substantial degree of protection against the P.1 variant, even in most individuals with a relatively mild infection,” the researchers conclude.

*Important Notice

medRxiv 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.

Written by

Dr. Ramya Dwivedi

Ramya has a Ph.D. in Biotechnology from the National Chemical Laboratories (CSIR-NCL), in Pune. Her work consisted of functionalizing nanoparticles with different molecules of biological interest, studying the reaction system and establishing useful applications.