RESUMEN
Since the SARS-CoV-2 outbreak in 2019, a diversity of viral genomic variants has emerged and spread globally due to increased transmissibility, pathogenicity, and immune evasion. By the first trimester of 2023 in Chile, as in most countries, BQ and XBB were the predominant circulating sub-lineages of Omicron. The molecular and antigenic characteristics of these variants have been mainly determined using non-authentic spike pseudoviruses, which is often described as a limitation. Additionally, few comparative studies using isolates from recent Omicron sub-lineages have been conducted. In this study, we isolated SARS-CoV-2 variants from clinical samples, including the ancestral B.1.1, Delta, Omicron BA.1, and sub-lineages of BA.2 and BA.5. We assessed their infectivity through cell culture infections and their antibody evasion using neutralization assays. We observed variations in viral plaque size, cell morphology, and cytotoxicity upon infection in Vero E6-TMPRSS2 cells for each variant compared to the ancestral B.1.1 virus. BA.2-derived sub-variants, such as XBB.1.5, showed attenuated viral replication, while BA.5-derived variants, such as BQ.1.1, exhibited replication rates similar to the ancestral SARS-CoV-2 virus. Similar trends were observed in intestinal Caco-2 cells, except for Delta. Antibody neutralization experiments using sera from individuals infected during the first COVID-19 wave (FWI) showed a consistent but moderate reduction in neutralization against Omicron sub-lineages. Interestingly, despite being less prevalent, BQ.1.1 showed a 6.1-fold greater escape from neutralization than XBB.1.5. Neutralization patterns were similar when tested against sera from individuals vaccinated with 3xBNT162b2 (PPP) or Coronavac-Coronavac-BNT162b2 (CCP) schedules. However, CCP sera showed 2.3-fold higher neutralization against XBB.1.5 than FWI and PPP sera. This study provides new insights into the differences between BA.2 and BA.5-derived variants, leading to their eventual outcompetition. Our analysis offers important evidence regarding the balance between infectivity and antigenic escape that drives the evolution of second-generation SARS-CoV-2 variants in the population.
RESUMEN
SARS-CoV-2 Omicron subvariants are still emerging and spreading worldwide. These variants contain a high number of polymorphisms in the spike (S) glycoprotein that could potentially impact their pathogenicity and transmission. We have previously shown that the S:655Y and P681H mutations enhance S protein cleavage and syncytia formation. Interestingly, these polymorphisms are present in Omicron S protein. Here, we characterized the cleavage efficiency and fusogenicity of the S protein of different Omicron sublineages. Our results showed that Omicron BA.1 subvariant is efficiently cleaved but it is poorly fusogenic compared to previous SARS-CoV-2 strains. To understand the basis of this phenotype, we generated chimeric S protein using combinations of the S1 and S2 domains from WA1, Delta and Omicron BA.1 variants. We found that the S2 domain of Omicron BA.1 hindered efficient cell-cell fusion. Interestingly, this domain only contains six unique polymorphisms never detected before in ancestral SARS-CoV-2 variants. WA1614G S proteins containing the six individuals S2 Omicron mutations were assessed for their fusogenicity and S surface expression after transfection in cells. Results showed that the S:N856K and N969K substitutions decreased syncytia formation and impacted S protein cell surface levels. However, we observed that "first-generation" Omicron sublineages that emerged subsequently, had convergently evolved to an enhanced fusogenic activity and S expression on the surface of infected cells while "second-generation" Omicron variants have highly diverged and showed lineage-specific fusogenic properties. Importantly, our findings could have potential implications in the improvement and redesign of COVID-19 vaccines.
Asunto(s)
Vacunas contra la COVID-19 , COVID-19 , Humanos , SARS-CoV-2/genética , Mutación , Glicoproteína de la Espiga del Coronavirus/genéticaRESUMEN
BACKGROUND/AIM: Last year was characterized by the appearance of novel SARS-CoV-2 virus variants, mainly the omicron sub-lineages BA.2.12.1, BA.4, and BA.5, which have confirmed resistance to the acquired immune response developed following first-generation mRNA vaccines. Given the ability to use mRNA technology to respond quickly to variant strains, novel bivalent vaccines against novel omicron variants were generated. In the current work, we evaluated the efficacy and safety of novel bivalent mRNA Omicron-containing booster vaccines among patients with hematological neoplasms, including both lymphoproliferative and myeloid malignancies. PATIENTS AND METHODS: Cohort patients were obtained from electronic medical records of Maccabi Healthcare Services (MHS), the second-largest healthcare organization in Israel. We analyzed the outcome of all patients with hematological neoplasms, between September 21, 2022, and December 31, 2022, who were identified as having SARS-CoV-2 infection based on polymerase chain reaction (PCR) tests. The Kaplan-Meier method was used to compare the proportion of patients hospitalized for SARS-CoV-2 infection within 30 days among recipients and non-recipients of omicron vaccine. RESULTS: During the study period, 472 patients were infected with Omicron. We compared the outcome of 70 patients who received the bivalent mRNA booster to 402 who did not. Fewer bivalent recipients needed COVID-19-related hospitalization [2 of 70 (2.9%)] in comparison to the non-vaccinated cohort [42 of 402 (10.4%)] (p-value=0.0304). This represents an 89% relative risk reduction in COVID-19-related hospitalization in patients with hematological neoplasms. The median duration of hospitalization was 7 days for the non-vaccinated group and 4 for the vaccinated group. A statistically significant increase in ischemic stroke rates due to bivalent mRNA Omicron-containing booster vaccine was not observed. CONCLUSION: The bivalent Omicron-containing vaccine mRNA booster has a protective effect in preventing and shortening hospitalization in patients with hematological neoplasms with an acceptable safety profile.