Project description:To investigate the virological properties of SARS-CoV-2 variants, we amplified the clinical isolates of an early pandemic D614G-bearing isolate (B.1.1 lineage, strain TKYE610670; GISAID ID: EPI_ISL_479681), a Delta isolate (B.1.617.2 lineage, strain TKYTK1734; GISAID ID: EPI_ISL_2378732) and an Omicron isolate (BA.1 lineage, strain TY38-873; GISAID ID: EPI_ISL_7418017) and prepared the working viruses.
Project description:To investigate the virological properties of a SARS-CoV-2 variant, Omicron BA.2, we generated chimeric recombinant viruses that express GFP and encodes the S gene of B.1.1 (ancestral D614G-bearing virus), Delta, BA.1 and BA.2. To verify the genome sequence of the working viruses, we performed viral RNA-sequencing of the viral stock.
Project description:The SARS-CoV-2 pandemic was marked with emerging viral variants, some of which were designated as variants of concern (VOCs) due to their selection and rapid circulation in the human population. Here we elucidate functional features of each VOC linked to variations in growth during infection. Patient-derived primary nasal cultures grown at air-liquid-interface (ALI) were used to model upper-respiratory infection and human lung epithelial cell lines used to model lower-respiratory infection. All VOCs replicated to higher titers than the ancestral virus, suggesting a selection for replication efficiency. In primary nasal ALI cultures, Omicron replicated to the highest titers at early time points, followed by Delta, paralleling comparative studies of patient samples. All SARS-CoV-2 viruses entered the cell primarily via a transmembrane serine protease 2 (TMPRSS2)-dependent pathway, and Omicron was more likely to use an endosomal route of entry. All VOCs activated and overcame dsRNA-activated cellular responses including interferon signaling, oligoadenylate ribonuclease L (OAS-RNase L) degradation and protein kinase R (PKR) activation. Among the VOCs Omicron expressed the most interferon and interferon stimulated genes. Infections in nasal ALI resulted in damage to nasal cells such as a compromise of cell-barrier integrity and loss of nasal cilia and ciliary beating function, especially with Delta infections. Overall, Omicron replication was optimized for growth in the upper-respiratory system and least-favorable in the lower-respiratory cell line; and Delta was the most cytopathic for both upper and lower respiratory cells. Our findings highlight the functional differences among VOCs and illuminate distinct mechanisms of pathogenesis in infected individuals.
Project description:The Omicron variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), first identified in November 2021 in South Africa, has initiated the 5th wave of global pandemics. Here, we systemically examined immunological and metabolic characteristics of Omicron variants infection. We found Omicron resisted to neutralizing antibody targeting receptor binding domain (RBD) of wild-type SARS-CoV-2. Omicron could not be neutralized by sera of Corona Virus Disease 2019 (COVID-19) convalescent individuals who were infected with the Delta variant. Through mass spectrometry on MHC-bound peptidomes, we found that the spike protein of the Omicron variants could generate additional CD8+ T cell epitopes, compared with Delta. These epitopes could induce robust CD8+ T cell responses. Moreover, we found booster vaccination increased the cross-memory CD8+ T cell responses against Omicron. Metabolic regulome analysis of Omicron-specific T cell showed a metabolic profile that promoted memory T cell responses. Consistently, a higher fraction of memory CD8+ T cells were found in Omicron stimulated peripheral blood mononuclear cells (PBMCs). In addition, CD147 was also a receptor for the Omicron variants, and CD147 antibody inhibited infection of Omicron. CD147-mediated Omicron infection in a human CD147 transgenic mouse model induced exudative alveolar pneumonia. Taken together, our data suggested that vaccination booster and receptor blocking antibody are two effective strategies against Omicron.
Project description:There have been reports of long coronavirus disease (long COVID) and breakthrough infections (BTIs); however, the mechanisms and pathological features of long COVID after Omicron BTIs remain unclear. Assessing long COVID and immune recovery after Omicron BTIs is crucial for understanding the disease and developing and managing new-generation vaccines. Here, we followed up mild BA.2 BTI convalescents for six-month with routine blood tests and neutralization assay. Then, we applied proteomic analysis and single-cell RNA sequencing (scRNA-seq) to study the convalescents’ recovery status. Lastly, we retrospectively analyzed the clinical parameters related to immunity and metabolism of the convalescents. We found that major organs exhibited ephemeral dysfunction in double-Convidecia vaccinated persons who experienced BA.2 BTI and recovered to normal in approximately six-month. We observed durable and potent levels of neutralizing antibodies against major circulating severe acute respiratory syndrome coronavirus 2 sub-variants, including BQ.1, BQ.1.1 and BF.7, indicating that hybrid humoral immunity stays active. However, PLTs may take longer to recover. This was supported by proteomic and scRNA-seq analyses, which also showed coagulation disorder and an imbalance between anti-pathogen immunity and metabolism six-month after BA.2 BTI. The immunity-metabolism imbalance was then proved with retrospective analysis of abnormal levels of hormones, low blood glucose level and coagulation profile. The long-term malfunctional coagulation and imbalance in the material metabolism and immunity may contribute to the development of long COVID and act as useful indicators for assessing recovery and the long-term impacts after Omicron sub-variant BTIs.
Project description:Antibody response following Omicron infection is reported to be less robust than that to other variants. Here we investigated how prior vaccination and/or prior infection modulates that response. Disease severity, antibody responses and immune transcriptomes were characterized in four groups of Omicron-infected outpatients (n=83): unvaccinated/no prior infection, vaccinated/no prior infection, unvaccinated/prior infection and vaccinated/prior infection. The percentage of patients with asymptomatic or mild disease was highest in the vaccinated/no prior infection group (87%) and lowest in the unvaccinated/no prior infection group (47%). Significant anti-Omicron spike antibody levels and neutralizing activity were detected in the vaccinated group immediately after infection but were not present in the unvaccinated/no prior infection group. Within two weeks, antibody levels against Omicron, increased. Omicron neutralizing activity in the vaccinated group exceeded that of the prior infection group. No increase in neutralizing activity in the unvaccinated/no prior infection group was seen. The unvaccinated/prior infection group showed an intermediate response. We then investigated the early transcriptomic response following Omicron infection in these outpatient populations and compared it to that found in unvaccinated hospitalized patients with Alpha infection. Omicron infected patients showed a gradient of transcriptional response dependent upon whether or not they were previously vaccinated or infected. Vaccinated patients showed a significantly blunted interferon response as compared to both unvaccinated Omicron infected outpatients and unvaccinated Alpha infected hospitalized patients typified by the response of specific gene classes such as OAS and IFIT that control anti-viral responses and IFI27, a predictor of disease outcome.
Project description:SARS-CoV-2 Omicron infection results in a milder clinical feature compared to the Delta strain. The development of Omicron specific vaccine has also been hampered due to the low immunogenicity. By reverse-mutating the amino acids in the Omicron receptor binding domain (RBD), we identified that the mutation from Phenylalanine 375 (F375) in the Omicron spike to Serine 375 (S375) in Delta and other early strains significantly enhances the immune response in the manner of vaccines. Interestingly, the new evolution of the 371FAPF375FAF sequence in Omicron exhibited a potent inhibitory effect on macrophage uptake of the RBD nanoparticle or spike-pseudovirus particles. Omicron RBD enhances binding to Siglec-9 on macrophages to reduce the immunogenicity and increase the immune evasion, which could be abrogated by Serine 375 mutation. Based upon these observations, we further developed a bivalent Omicron RBD with S375 mutation and Delta RBD nanoparticle vaccine, which elicited potent and broad neutralizing antibodies in mice, rabbits, and rhesus macaques. Our research suggests that manipulating the Siglec-9 pathway could be a promising approach to enhancing vaccine response. Importantly, our findings suggest that Omicron subvariants have developed a new strategy to evade immune surveillance by impairing the phagocytosis and antigen presentation processes of macrophages.
Project description:Detection of high level of co-infection and the emergence of novel SARS-CoV-2 delta-omicron and omicron-omicron recombinants in the epidemiological surveillance of Andalusia (Spain)