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      Characterization of SARS-CoV-2 recombinants and emerging Omicron sublineages

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          Abstract

          The SARS-CoV-2 Omicron is currently the predominant circulating variant in the COVID-19 pandemic. The dominating Omicron sublineages respond to host immune pressure and develop advantageous mutations or genetic recombination, which result in variants that are more contagious or better at escaping immune responses in response to previous infection or vaccination. Meanwhile, multiple genetic recombination events have been reported in coinfection cases, the majority of which have resulted from the recombination between co-circulating Omicron BA.1 (or BA.1.1) and Delta variant or BA.2. Here, we review the knowledge and characterization of recombination for SARS-CoV-2 at the population level, provide an update on the occurrence of newly circulating Omicron sublineages, and discuss the effectiveness of novel vaccines/therapeutic drugs against the Omicron variant.

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          Most cited references54

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          Case Study: Prolonged infectious SARS-CoV-2 shedding from an asymptomatic immunocompromised cancer patient.

          Long-term SARS-CoV-2 shedding was observed from the upper respiratory tract of a female immunocompromised patient with chronic lymphocytic leukemia and acquired hypogammaglobulinemia. Shedding of infectious SARS-CoV-2 was observed up to 70 days, and genomic and subgenomic RNA up to 105 days past initial diagnosis. The infection was not cleared after a first treatment with convalescent plasma, suggesting limited impact on SARS-CoV-2 in the upper respiratory tract within this patient. Several weeks after a second convalescent plasma transfusion, SARS-CoV-2 RNA was no longer detected. We observed marked within-host genomic evolution of SARS-CoV-2, with continuous turnover of dominant viral variants. However, replication kinetics in Vero E6 cells and primary human alveolar epithelial tissues were not affected. Our data indicate that certain immunocompromised patients may shed infectious virus for longer durations than previously recognized. Detection of subgenomic RNA is recommended in persistently SARS-CoV-2 positive individuals as a proxy for shedding of infectious virus.
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            A Bivalent Omicron-Containing Booster Vaccine against Covid-19

            Abstract Background The safety and immunogenicity of the bivalent omicron-containing mRNA-1273.214 booster vaccine are not known. Methods In this ongoing, phase 2–3 study, we compared the 50-μg bivalent vaccine mRNA-1273.214 (25 μg each of ancestral Wuhan-Hu-1 and omicron B.1.1.529 [BA.1] spike messenger RNAs) with the previously authorized 50-μg mRNA-1273 booster. We administered mRNA-1273.214 or mRNA-1273 as a second booster in adults who had previously received a two-dose (100-μg) primary series and first booster (50-μg) dose of mRNA-1273 (≥3 months earlier). The primary objectives were to assess the safety, reactogenicity, and immunogenicity of mRNA-1273.214 at 28 days after the booster dose. Results Interim results are presented. Sequential groups of participants received 50 μg of mRNA-1273.214 (437 participants) or mRNA-1273 (377 participants) as a second booster dose. The median time between the first and second boosters was similar for mRNA-1273.214 (136 days) and mRNA-1273 (134 days). In participants with no previous severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the geometric mean titers of neutralizing antibodies against the omicron BA.1 variant were 2372.4 (95% confidence interval [CI], 2070.6 to 2718.2) after receipt of the mRNA-1273.214 booster and 1473.5 (95% CI, 1270.8 to 1708.4) after receipt of the mRNA-1273 booster. In addition, 50-μg mRNA-1273.214 and 50-μg mRNA-1273 elicited geometric mean titers of 727.4 (95% CI, 632.8 to 836.1) and 492.1 (95% CI, 431.1 to 561.9), respectively, against omicron BA.4 and BA.5 (BA.4/5), and the mRNA-1273.214 booster also elicited higher binding antibody responses against multiple other variants (alpha, beta, gamma, and delta) than the mRNA-1273 booster. Safety and reactogenicity were similar with the two booster vaccines. Vaccine effectiveness was not assessed in this study; in an exploratory analysis, SARS-CoV-2 infection occurred in 11 participants after the mRNA-1273.214 booster and in 9 participants after the mRNA-1273 booster. Conclusions The bivalent omicron-containing vaccine mRNA-1273.214 elicited neutralizing antibody responses against omicron that were superior to those with mRNA-1273, without evident safety concerns. (Funded by Moderna; ClinicalTrials.gov number, NCT04927065.)
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              Evolution of the SARS‐CoV‐2 omicron variants BA.1 to BA.5: Implications for immune escape and transmission

              The first dominant SARS‐CoV‐2 Omicron variant BA.1 harbours 35 mutations in its Spike protein from the original SARS‐CoV‐2 variant that emerged late 2019. Soon after its discovery, BA.1 rapidly emerged to become the dominant variant worldwide and has since evolved into several variants. Omicron is of major public health concern owing to its high infectivity and antibody evasion. This review article examines the theories that have been proposed on the evolution of Omicron including zoonotic spillage, infection in immunocompromised individuals and cryptic spread in the community without being diagnosed. Added to the complexity of Omicron's evolution are the multiple reports of recombination events occurring between co‐circulating variants of Omicron with Delta and other variants such as XE. Current literature suggests that the combination of the novel mutations in Omicron has resulted in the variant having higher infectivity than the original Wuhan‐Hu‐1 and Delta variant. However, severity is believed to be less owing to the reduced syncytia formation and lower multiplication in the human lung tissue. Perhaps most challenging is that several studies indicate that the efficacy of the available vaccines have been reduced against Omicron variant (8–127 times reduction) as compared to the Wuhan‐Hu‐1 variant. The administration of booster vaccine, however, compensates with the reduction and improves the efficacy by 12–35 fold. Concerningly though, the broadly neutralising monoclonal antibodies, including those approved by FDA for therapeutic use against previous SARS‐CoV‐2 variants, are mostly ineffective against Omicron with the exception of Sotrovimab and recent reports suggest that the Omicron BA.2 is also resistant to Sotrovimab. Currently two new Omicron variants BA.4 and BA.5 are emerging and are reported to be more transmissible and resistant to immunity generated by previous variants including Omicron BA.1 and most monoclonal antibodies. As new variants of SARS‐CoV‐2 will likely continue to emerge it is important that the evolution, and biological consequences of new mutations, in existing variants be well understood.
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                Author and article information

                Journal
                Int J Med Sci
                Int J Med Sci
                ijms
                International Journal of Medical Sciences
                Ivyspring International Publisher (Sydney )
                1449-1907
                2023
                1 January 2023
                : 20
                : 1
                : 151-162
                Affiliations
                [1 ]Tianjin Institute of Urology, The Second Hospital of Tianjin Medical University, Tianjin, China
                [2 ]Department of Genetics, School of Basic Medical Sciences, Tianjin Medical University, Tianjin, China
                [3 ]Tianjin Children's Hospital, Children's Hospital, Tianjin University, Tianjin, China
                Author notes
                ✉ Corresponding authors: Wei Liu, Tianjin Children's Hospital, Children's Hospital, Tianjin University, Tianjin, China. E-mail: lance1971@ 123456163.com ; Yuliang Wang, The Tianjin Institute of Urology, Second Hospital of Tianjin Medical University, Tianjin, China. E-mail: wangyuliang123@ 123456tmu.edu.cn or wang_yu_l@ 123456163.com .

                * These authors contributed equally to this work.

                Competing Interests: The authors have declared that no competing interest exists.

                Article
                ijmsv20p0151
                10.7150/ijms.79116
                9812801
                36619228
                e6ef0204-f76f-4c05-9810-b1fb47b6ab69
                © The author(s)

                This is an open access article distributed under the terms of the Creative Commons Attribution License ( https://creativecommons.org/licenses/by/4.0/). See http://ivyspring.com/terms for full terms and conditions.

                History
                : 21 September 2022
                : 10 December 2022
                Categories
                Review

                Medicine
                covid-19,sars-cov-2,omicron,recombinant,ba.5,vaccine
                Medicine
                covid-19, sars-cov-2, omicron, recombinant, ba.5, vaccine

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