Neutralizing antibodies and T-cell responses to inactivated SARS-CoV-2 vaccine in COVID-19 convalescents one and a half years after infection.

Vaccines have been considered the most promising solution for ending the coronavirus disease 2019 (COVID-19) pandemic. Information regarding neutralizing antibodies (NAbs) and T-cell immune response in inactivated SARS-CoV-2 vaccine-immunized COVID-19 convalescent patients were either only available for a short time after illness recovered or not available at all (T-cell immunity). We evaluated SARS-CoV-2 NAbs and cellular immune responses to the SARS-CoV-2 inactivated vaccine in convalescent patients who recovered from infection for about one and a half years. We found that compared to before vaccination, SARS-CoV-2 NAbs and specific T-cell responses were significantly boosted by the inactivated vaccine in convalescent patients, which confirmed the pre-existing adaptive immunity in SARS-CoV-2 infected people. We observed that NAbs and IFN-γ-secreting T-cell response elicited by a single vaccine dose in subjects with prior COVID-19 infection were higher than after two doses of vaccine in SARS-CoV-2 naïve subjects. Both humoral and cellular immune responses elicited by one and two doses of inactivated vaccine were comparable in COVID-19-recovered persons. In conclusion, inactivated COVID-19 vaccine induced robust NAbs and T-cell responses to SARS-CoV-2 in COVID-19 convalescent patients and immune responses after one dose were equal to that after receiving two doses, which highlighted that robust humoral and cellular immune response can be reactivated by the inactivated vaccine in SARS-CoV-2 convalescent patients.

Neutralizing antibodies and cellular immune response after two doses of inactivated SARS-CoV-2 vaccine in China.

BACKGROUND: As of 2022, inactivated SARS-CoV-2 vaccines had been used in more than 91 countries. However, limited real world information was available on the immune responses of the inactivated SARS-CoV-2 vaccine. METHODS: We used SARS-CoV-2 pseudovirues to determine the neutralizing antibodies (NAbs) to wild type and several global variants and utilized enzyme-linked immunosorbent assay to investigate IFN-γ-secreting T-cell responses to SARS-CoV-2 among 240 vaccinated individuals after two doses of inactivated vaccine in China. RESULTS: A majority of the vaccinated (>90%) developed robust NAbs and T-cell responses to SARS-CoV-2 in the first two months after the second dose. After six months, only 37.0% and 44.0% of vaccinees had NAbs and T-cell immunity to SARS-CoV-2, respectively. Immune serum retained most of its neutralizing potency against the Alpha and Iota variants, but lost significant neutralizing potency against the Beta, Kappa, Delta, and Omicron variants. Only 40% of vaccine-sera retained low-level neutralization activities to Omicron, with a 14.7-fold decrease compared to the wild type. CONCLUSION: The inactivated SARS-CoV-2 vaccine stimulated robust NAbs and T-cell immune responses in the first two months after the second dose but the immune effect dropped rapidly, highlighing that a third dose or additional booster immunizations may be required to boost immunity against SARS-CoV-2.

SARS-CoV-2 Delta Variant in Jingmen City, Hubei Province, China, 2021: Children Susceptible and Vaccination Breakthrough Infection.

Background: The delta variant (B.1.617.2) of SARS-CoV-2 was the dominant viral strain causing COVID-19 in China, 2021. We reported a SARS-CoV-2 delta variant outbreak in Jingmen City, Hubei Province, China. Methods: The data of epidemiological, clinical, laboratorial, and vaccination of COVID-19 cases were collected through field investigation and analyzed. Results: During the outbreak from 4 to 20 August 2021, 58 cases of the SARS-CoV-2 delta variant (B.1.617.2) were identified with 15 (25.9%) asymptomatic and 43 (74.1%) symptomatic (mild and moderate) patients. The mean serial interval was 2.6 days (standard deviation: 2.0, 95% CI: 1.9-3.6). The median age of the patients was 39 years (ranging from 1 to 60 years) with the high proportion in children (19.0%). The secondary attack rate was 9.8% higher from parents to their children (<18 years) (46.2%, 95% CI: 14.8-77.5%) than that between spouses (36.4%, 95% CI: 14.5-58.2%), but no significant difference was observed (p > 0.05). Approximately half (27; 46.6%) of cases were vaccine breakthrough infections. In vaccine breakthrough cases (fully vaccinated), viral loads decreased 1.9-3.4-folds (p < 0.05), duration of viral shedding shortened 5 days (p < 0.05), and the risk of becoming symptomatic from asymptomatic decreased 33% (95% CI: 5-53%) (aged ≥12 years) than those in unvaccinated infections. Conclusions: Children are highly susceptible to the SARS-CoV-2 delta variant in the COVID-19 outbreak in Jingmen City in 2021. Inactivated vaccine derived from wide-type strain can effectively reduce the viral load, duration of viral shedding, and clinical severity in vaccine breakthrough cases. Our study indicates that protective measures that include full vaccination against COVID-19, especially in children, should be strengthened.

Neutralizing Antibodies and Cellular Immune Responses Against SARS-CoV-2 Sustained One and a Half Years After Natural Infection.

Background: COVID-19 has caused more than 2.6 billion infections and several million deaths since its outbreak 2 years ago. We know very little about the long-term cellular immune responses and the kinetics of neutralizing antibodies (NAbs) to SARS-CoV-2 because it has emerged only recently in the human population. Methods: We collected blood samples from individuals who were from the first wave of the COVID-19 epidemic in Wuhan between December 30, 2019, and February 24, 2020. We analyzed NAbs to SARS-CoV-2 using pseudoviruses and IgG antibodies to SARS-CoV-2 spike (S) and nucleocapsid (N) protein using enzyme-linked immunosorbent assay in patients' sera and determined SARS-CoV-2-specific T-cell responses of patients with ELISpot assays. Results: We found that 91.9% (57/62) and 88.9% (40/45) of COVID-19 patients had NAbs against SARS-CoV-2 in a year (10-11 months) and one and a half years (17-18 months), respectively, after the onset of illness, indicating that NAbs against SARS-CoV-2 waned slowly and possibly persisted over a long period time. Over 80% of patients had IgG antibodies to SARS-CoV-2 S and N protein one and a half years after illness onset. Most patients also had robust memory T-cell responses against SARS-CoV-2 one and a half years after the illness. Among the patients, 95.6% (43/45) had an IFN-γ-secreting T-cell response and 93.8% (15/16) had an IL-2-secreting T-cell response. The T-cell responses to SARS-CoV-2 were positively correlated with antibodies (including neutralizing antibodies and IgG antibodies to S and N protein) in COVID-19 patients. Eighty percent (4/5) of neutralizing antibody-negative patients also had SARS-CoV-2-specific T-cell response. After long-term infection, protective immunity was independent of disease severity, sex, and age. Conclusions: We concluded that SARS-CoV-2 infection elicited a robust and persistent neutralizing antibody and memory T-cell response in COVID-19 patients, indicating that these sustained immune responses, among most SARS-CoV-2-infected people, may play a crucial role in protection against reinfection.

SARS-CoV-2 ORF3a Induces Incomplete Autophagy via the Unfolded Protein Response.

In the past year and a half, SARS-CoV-2 has caused 240 million confirmed cases and 5 million deaths worldwide. Autophagy is a conserved process that either promotes or inhibits viral infections. Although coronaviruses are known to utilize the transport of autophagy-dependent vesicles for the viral life cycle, the underlying autophagy-inducing mechanisms remain largely unexplored. Using several autophagy-deficient cell lines and autophagy inhibitors, we demonstrated that SARS-CoV-2 ORF3a was able to induce incomplete autophagy in a FIP200/Beclin-1-dependent manner. Moreover, ORF3a was involved in the induction of the UPR (unfolded protein response), while the IRE1 and ATF6 pathways, but not the PERK pathway, were responsible for mediating the ORF3a-induced autophagy. These results identify the role of the UPR pathway in the ORF3a-induced classical autophagy process, which may provide us with a better understanding of SARS-CoV-2 and suggest new therapeutic modalities in the treatment of COVID-19.

A Tuberculosis Outbreak During the COVID-19 Pandemic - Hubei Province, China, 2020.

What is already known about topic? Multidrug-resistant tuberculosis (MDR-TB) has become a growing threat to public health. There were few reports about family-to-school MDR-TB outbreaks in China, especially during the coronavirus disease 2019 (COVID-19) pandemic. What is added by this report? A tuberculosis (TB) outbreak happened in Hubei Province during the COVID-19 pandemic. The transmission chain was probably from a father （MDR-TB case）with retreated TB history to his daughter, who then spread TB to her classmates. What are the implications for public health practice? We should enhance TB control both in schools and households, including strengthening TB/MDR-TB detection, health education, and ventilation. The TB contact screening cannot only be limited to outside school settings and should be conducted in the school when a TB student is absent from school for 2 or 3 months, or even longer especially during the COVID-19 pandemic.

Development of a Nucleocapsid Protein-Based ELISA for Detection of Human IgM and IgG Antibodies to SARS-CoV-2.

SARS-CoV-2 is the etiologic agent of COVID-19, which has led to a dramatic loss of human life and presents an unprecedented challenge to public health worldwide. The gold standard assay for SARS-CoV-2 identification is real-time polymerase chain reaction; however, this assay depends on highly trained personnel and sophisticated equipment and may suffer from false results. Thus, a serological antibody test is a supplement to the diagnosis or screening of SARS-CoV-2. Here, we develop and evaluate the diagnostic performance of an IgM/IgG indirect ELISA method for antibodies against SARS-CoV-2 in COVID-19. The ELISA was constructed by coating with a recombinant nucleocapsid protein of SARS-CoV-2 on an enzyme immunoassay plate, and its sensitivity and specificity for clinical diagnosis of SARS-CoV-2 infection was assessed by detecting the SARS-CoV-2-specific IgM and IgG antibodies in COVID-19 patient's sera or healthy person's sera. The SARS-CoV-2 positive serum samples (n = 168) were collected from confirmed COVID-19 patients. A commercial nucleocapsid protein-based chemiluminescent immunoassay (CLIA) kit and a colloidal gold immunochromatography kit were compared with those of the ELISA assay. The specificity, sensitivity, positive predictive value (PPV), and negative predictive value (NPV) of IgM were 100, 95.24, 100, and 91.84%, whereas those of IgG were 100, 97.02, 100, and 94.74%, respectively. We developed a highly sensitive and specific SARS-CoV-2 nucleocapsid protein-based ELISA method for the diagnosis and epidemiologic investigation of COVID-19 by SARS-CoV-2 IgM and IgG antibody detection.

Seroprevalence and asymptomatic carrier status of SARS-CoV-2 in Wuhan City and other places of China.

Wuhan City (WH) in China was the first place to report COVID-19 in the world and the outbreak of COVID-19 was controlled in March of 2020 in WH. It is unclear what percentage of people were infected with SARS-CoV-2 and what percentage of population is carriers of SARS-CoV-2 in WH. We retrospectively analyzed the SARS-CoV-2 IgG and IgM antibody positive rates in 63,107 healthy individuals from WH and other places of China using commercial colloidal gold detection kits from March 6 to May 3, 2020. Statistical approaches were utilized to explore the difference and correlation for the seropositive rate of IgG and IgM antibody on the basis of sex, age group, geographic region and detection date. The total IgG and IgM antibody positive rate of SARS-CoV-2 was 1.68% (186/11,086) in WH, 0.59% (226/38,171) in Hubei Province without Wuhan (HB), and 0.38% (53/13,850) in the nation except for Hubei Province (CN), respectively. The IgM positive rate was 0.46% (51/11,086) in WH, 0.13% (51/38,171) in HB, and 0.07% (10/13,850) in CN. The incidence of IgM positive rates in healthy individuals increased from March 6 to May 3, 2020 in WH. Female and older age had a higher probability of becoming infected than males (OR = 1.34; 95% CI: 1.08-1.65) or younger age (OR = 2.25; 95% CI: 1.06-4.78). The seroprevalence of SARS-CoV-2 was relatively low in WH and other places of China, but it is significantly high in WH than other places of China; a large amount of asymptomatic carriers of SARS-CoV-2 existed after elimination of clinical cases of COVID-19 in Wuhan City. Therefore, SARS-CoV-2 may exist in a population without clinical cases for a long period.

Identification of cGAS as an innate immune sensor of extracellular bacterium Pseudomonas aeruginosa.

Cyclic GMP-AMP synthase (cGAS) is reported essential for detecting intracellular bacteria. However, it remains to be determined whether and how cGAS is involved in extracellular bacterial infection. Here, we report that cGAS is essential for mediating type I interferon (IFN) production in infection by multiple extracellular pathogens, including Pseudomonas aeruginosa, Klebsiella pneumoniae, and Staphylococcus aureus. In addition, the canonical cGAS-stimulator of interferon gene (STING)-IFN axis is required for protecting mice from P. aeruginosa-induced mouse acute pulmonary infection, confirmed in cGAS pathway-specific gene deficiency mouse models. cGAS -/- and STING -/- mice exhibited reduced type I IFNs production, excessive inflammatory response accompanied with decreased resistance to P. aeruginosa challenge. Unfolded protein response was also modulated by cGAS through IRF3 and type I IFNs under P. aeruginosa infection. Collectively, these findings uncover the importance of cGAS in initiating immune responses against extracellular bacterial infection.

Real-time naive case fatality rates can reflect timeliness of case confirmation during pandemics.

An objective law was observed that naive case fatality rates (CFRs) of a disease will decrease early and then gradually increase infinitely near the true CFR as time went on during an outbreak. The normal growth of naive CFR was an inherent character rather than indicating the disease was becoming more severe. According to the law, by monitoring real-time naive CFRs, it can help outbreak-controllers know if there were many cases left unconfirmed or undiscovered in the outbreak. We reflected on the use of the naive CFR in the context of COVID-19 outbreaks. The results showed that Hubei Province of China, France and South Korea had cases that were not confirmed in a timely manner during the initial stages of the outbreak. Delayed case confirmations existed for long periods of time in France, Italy, the United Kingdom, the Netherlands and Spain. Monitoring of real-time naive CFRs could be helpful for decision-makers to identify under-reporting of cases during pandemics.