Regulatory CD4+ and CD8+ T cells are negatively correlated with CD4+ /CD8+ T cell ratios in patients acutely infected with SARS-CoV-2.

Regulatory T cell can protect against severe forms of coronaviral infections attributable to host inflammatory responses. But its role in the pathogenesis of COVID-19 is still unclear. In this study, frequencies of total and multiple subsets of lymphocytes in peripheral blood of COVID-19 patients and discharged individuals were analyzed using a multicolor flow cytometry assay. Plasma concentration of IL-10 was measured using a microsphere-based immunoassay kit. Comparing to healthy controls, the frequencies of total lymphocytes and T cells decreased significantly in both acutely infected COVID-19 patients and discharged individuals. The frequencies of total lymphocytes correlated negatively with the frequencies of CD3- CD56+ NK cells. The frequencies of regulatory CD8+ CD25+ T cells correlated with CD4+ /CD8+ T cell ratios positively, while the frequencies of regulatory CD4+ CD25+ CD127- T cells correlated negatively with CD4+ /CD8+ T cell ratios. Ratios of CD4+ /CD8+ T cells increased significantly in patients beyond age of 45 years. And accordingly, the frequencies of regulatory CD8+ CD25+ T cells were also found significantly increased in these patients. Collectively, the results suggest that regulatory CD4+ and CD8+ T cells may play distinct roles in the pathogenesis of COVID-19. Moreover, the data indicate that NK cells might contribute to the COVID-19 associated lymphopenia.

Sequential Administration of SARS-CoV-2 Strains-Based Vaccines Effectively Induces Potent Immune Responses against Previously Unexposed Omicron Strain.

In the past few years, the continuous pandemic of COVID-19 caused by SARS-CoV-2 has placed a huge burden on public health. In order to effectively deal with the emergence of new SARS-CoV-2 variants, it becomes meaningful to further enhance the immune responses of individuals who have completed the first-generation vaccination. To understand whether sequential administration using different variant sequence-based inactivated vaccines could induce better immunity against the forthcoming variants, we tried five inactivated vaccine combinations in a mouse model and compared their immune responses. Our results showed that the sequential strategies have a significant advantage over homologous immunization by inducing robust antigen-specific T cell immune responses in the early stages of immunization. Furthermore, the three-dose vaccination strategies in our research elicited better neutralizing antibody responses against the BA.2 Omicron strain. These data provide scientific clues for finding the optimal strategy within the existing vaccine platform in generating cross-immunity against multiple variants including previously unexposed strains.

Identifying Risk Factors for Secondary Infection Post-SARS-CoV-2 Infection in Patients With Severe and Critical COVID-19.

Emerging evidence has unveiled the secondary infection as one of the mortal causes of post-SARS-CoV-2 infection, but the factors related to secondary bacterial or fungi infection remains largely unexplored. We here systematically investigated the factors that might contribute to secondary infection. By clinical examination index analysis of patients, combined with the integrative analysis with RNA-seq analysis in the peripheral blood mononuclear cell isolated shortly from initial infection, this study showed that the antibiotic catabolic process and myeloid cell homeostasis were activated while the T-cell response were relatively repressed in those with the risk of secondary infection. Further monitoring analysis of immune cell and liver injury analysis showed that the risk of secondary infection was accompanied by severe lymphocytopenia at the intermediate and late stages and liver injury at the early stages of SARS-CoV-2. Moreover, the metagenomics analysis of bronchoalveolar lavage fluid and the microbial culture analysis, to some extent, showed that the severe pneumonia-related bacteria have already existed in the initial infection.

Severe Coronavirus disease 2019 pneumonia patients showed signs of aggravated renal impairment.

BACKGROUND: This objective of this study was to identify a sensitive indicator of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. METHODS: Samples were collected from 136 patients with Coronavirus disease 2019 (COVID-19) pneumonia admitted to the Shanghai public health clinical center (116 mild, 20 severe). The concentrations of serum urea, Uric Acid (UA), Creatinine (CREA), Erythrocyte sedimentation rate (ESR), high-sensitivity C-reactive protein (hs-CRP), procalcitonin (PCT), and urine protein (Pro) have been tested in this study. RESULTS: Higher levels of urea (female 7.00 ± 3.31, male 8.87 ± 5.18) Pro (female7/7, male 12/13), hs-CRP (female 2/7, male 5/13) ESR (female 94.43 ± 33.26, male 67.85 ± 22.77) were found in severe patients compared with the mild (urea: female 3.71 ± 1.00, male 4.42 ± 1.14; Pro: female 3/46, male 12/70; hs-CRP: female 1/46, male 3/70; ESR: female 43.32 ± 33.24, male 21.64 ± 21.82). UA is lower in the severe group (female 146.90 ± 54.01, male 139.34 ± 66.95) than in mild group (female 251.99 ± 64.35, male 339.81 ± 71.32). CREA and PCT did not show a significant difference between mild and severe patients, but the difference among the five biological markers (urea, Pro, hs-CRP, ESR, and UA) between mild and severe patients we tested was small (P < .05). CONCLUSION: Severe COVID-19 patients had higher levels of urea and Pro, while their UA levels were lower, reflecting poor kidney function in severe patients. However, higher levels of hs-CRP, ESR indicated that inflammatory responses were more active in severe patients.