Take a look at certain parts of the world and it’s almost like the pandemic never happened. From crowded venues to unmasked people out and about, widespread vaccination rollouts have allowed certain countries to enjoy some semblance of normalcy—at least, for a brief period. Though the light at the end of the tunnel seems tantalizingly close, the accumulation of mutations in SARS-CoV-2 has given rise to more contagious variants capable of causing severe infection, spurring governments to reinstate public health measures.
Among these is the highly transmissible G614 variant which quickly became the dominant SARS-CoV-2 strain worldwide in May 2020. G614 gets its powers from a point mutation in the gene encoding the spike (S) protein, a projection on the virus’ surface which enables it to infect host cells.
According to Lisa Ng, Executive Director of A*STAR’s Biomedical Research Council (BMRC) and Infectious Diseases Labs (ID Labs), this mutation increases the likelihood that G614 will be able to evade antibodies against wildtype SARS-CoV-2, potentially rendering our collective advances in COVID-19 diagnostics, therapeutics and vaccines ineffective.
To address these concerns, Ng and a team of collaborators studied the immune responses of 57 COVID-19 patients from Singapore infected with either the original D614 isolate or the G614 variant. Using flow cytometry, they found that for all patients, levels of initial IgM antibodies dipped over time, while the subsequent IgG antibody titers against SARS-CoV-2 remained elevated even months after infection.
Still, one question remained: could antibodies induced against D614 neutralize G614, and vice versa? To determine the answer, the researchers performed an antibody neutralization assay, incubating patient plasma samples with so-called pseudoviruses modified to express the S protein of the D614 and G614 strains. Accordingly, IgM and IgG antibodies from the convalescent patients of either strain neutralized both SARS-CoV-2 variants similarly.
“Neutralizing antibodies elicited against the wildtype SARS-CoV-2 can neutralize the variant G614 strain to the same degree, thus suggesting that the G614 mutation will not hinder ongoing vaccination efforts,” said Ng.
While this is good news, Ng cautioned that further studies are required to assess other variants of concern, such as the Delta variant, to ensure that vaccines and antibody-based therapeutics remain effective against the ever-changing coronavirus.
“SARS-CoV-2 is continuously mutating and evolving as part of its viral evasion mechanism,” she added. “It is now critical to determine the extent of humoral protection that is being conferred upon vaccination against emerging and new variants.”
The A*STAR-affiliated researchers contributing to this research are from the Infectious Diseases Labs (ID Labs) and Singapore Immunology Network.
