In a recent study, researchers report that sublineages of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant effectively escape B-cell immune responses by modifying neutralizing antibody epitopes.
Comparatively, T-cell immunity, which primarily targets the viral spike (S) protein, is less like to be affected by SARS-CoV-2 variants and, as a result, can remain effective in preventing severe symptoms associated with the coronavirus disease 2019 (COVID-19).
Introduction
Although most viral mutations do not significantly impact their properties, specific mutations can alter viral transmissibility, disease severity, and the effectiveness of therapeutic medicines, diagnostic tools, public health measures, and vaccines. Therefore, the threat of these types of mutations has led scientists worldwide to screen emerging and circulating SARS-CoV-2 variants continuously.
The SARS-CoV-2 Omicron variant has evolved into multiple sublineages, the earliest of which included BA.1, BA.2, BA.4, and BA.5. More recently, additional Omicron sublineages including BA.4.6, BF.7, BA.2.75, BA.2.75.2, BQ.1.1, and XBB have been identified and are currently emerging as dominant circulating strains to replace the previously dominant BA.5.
In addition to understanding these new variants' transmissibility, pathogenicity, and immune evasion properties, researchers have also examined the immunity patterns of human populations. These patterns are often determined by repeated infections with SARS-CoV-2 variants of concern (VOCs) and vaccination doses.
Study
The researchers of the current study utilized their established artificial intelligence/machine learning-based early warning system to evaluate the immune responses of both naive vaccinated individuals, as well as those who have experienced breakthrough infections, against the Omicron sublineages BA.4.6, BF.7, BA.2.75, BA.2.75.2, BQ.1.1, and XBB.
Three study cohorts were assessed, including 18 infection-naïve individuals who received three doses of the Pfizer-BioNTech BNT162b2 messenger ribonucleic acid (mRNA) vaccine and were 55 years old age or younger. Fifteen individuals aged 60 years or older who received four BNT162b2 vaccine doses were also included.
Furthermore, triple-vaccinated individuals who experienced breakthrough infections with Omicron sublineages were included in the study. Fourteen of these individuals were infected with BA.1, 19 were infected with BA.2, and 17 were infected with BA.4/BA.5.
Serum neutralization was assessed by 50% pseudovirus neutralization (pVN50) geometric mean titers (GMTs). In addition, a total of 506 neutralizing B-cell epitopes within the spike protein were examined to determine the degree to which B-cell epitope conservation corresponds to individual SARS-CoV-2 variant cross-neutralization.
Conclusion
The study findings indicate that SARS-CoV-2 VOCs are less likely to breach T-cell-mediated immunity at the population level. Thus, T-cell immunity can effectively limit severe COVID-19 symptoms, even in the absence of neutralizing antibodies.
Taken together, these findings emphasize the importance of boosting T-cell immunity through targeted vaccine strategies that induce CD8+ T-cell immunity in addition to antibody production.
Source:
https://www.news-medical.net/news/20221221/T-cell-immunity-remains-effective-against-SARS-CoV-2-Omicron-subvariants.aspx