The effect of immunization with inactivated SARS-CoV-2 vaccine (CoronaVac) and/or SARS-CoV-2 infection on antibody levels, plasmablasts, long-lived-plasma-cells, and IFN-γ release by natural killer cells.

OBJECTIVES: We evaluated the antibody response, natural killer cell response and B cell phenotypes in healthcare workers (HCW) who are vaccinated with two doses of CoronaVac with or without documented SARS-CoV-2 infection and unvaccinated HCWs with SARS-CoV-2 infection. METHODS: HCWs were divided into four groups: vaccine only (VO), vaccine after SARS-CoV-2 infection (VAI), SARS-CoV-2 infection only (IO), and SARS-CoV-2 infection after vaccine (IAV). Anti-SARS-CoV-2 spike protein (Anti-S) antibodies were measured by Elecsys Anti-SARS-CoV-2 S ELISA kit. Memory B cells (CD19+CD27+), plasmablast B cells (CD19+CD138+) and long-lived plasma cells (LLPC; CD138+CD19-) were measured by flow cytometry in 74 patients. Interferon gamma (IFN-γ) release by natural killer (NK) cells were measured by NKVue Test (NKMAX, Republic of Korea) in 76 patients. RT-PCR was performed with Bio-speedy® COVID-19 qPCR detection kit, Version 2 (Bioexen LTD, Istanbul, Turkey). RESULTS: The Anti-S antibodies were detectable in all HCWs (n: 224). The median Anti-S titers (BAU/mL) was significantly higher in VAI (620 25-75% 373-1341) compared to VO (136, 25-75% 85-283) and IO (111, 25-75% 54-413, p < 0.01). VAI group had significantly lower percentage of plasmablasts (2.9; 0-8.7) compared to VO (6.8; 3.5-12.0) and IO (9.9; 4.7-47.5, p < 0.01) (n:74). Percentage of LLPCs in groups VO, VAI and IO was similar. There was no difference of IFN-γ levels between the study groups (n: 76). CONCLUSION: The antibody response was similar between uninfected vaccinated HCWs and unvaccinated HCWs who had natural infection. HCWs who had two doses of CoronaVac either before or after the natural SARS-CoV-2 infection elicited significantly higher antibody responses compared to uninfected vaccinated HCWs. The lower percentages of plasmablasts in the VAI group may indicate their migration to lymph nodes and initiation of the germinal center reaction phase. IFN-γ response did not differ among the groups.

Peripheral innate and adaptive immune cells during COVID-19: Functional neutrophils, pro-inflammatory monocytes, and half-dead lymphocytes.

BACKGROUND: A better understanding of innate and adaptive cells in COVID-19 is necessary for the development of effective treatment methods and vaccines. METHODS: We studied phenotypic features of innate and adaptive immune cells, oxidative burst, phagocytosis, and apoptosis. One hundred and three patients with COVID-19 were grouped according to their clinical features into the categories of mild (35%), moderate (40.8%), and severe (24.3%). RESULTS: Monocytes were CD16+ pro-inflammatory monocytes and tended to shed their HLA-DR, especially in severe cases (p < 0.01). Neutrophils were mature and functional, although a decline of their CD10 and CD16 was observed (p < 0.01). No defect was found in the reactive oxygen species production and their apoptosis. The percentage of natural killer cells was in the normal range, whereas the percentages of CD8+ NK and CD56+ T lymphocytes were found to be high (p < 0.01). Although the absolute numbers of all lymphocyte subsets were low and showed a tendency for a gradual decrease in accordance with the disease progression, the most decreased absolute number was that of B lymphocytes, followed by CD4+ T cells in the severe cases. The percentages of double-negative T cells; HLA-DR+ CD3+ and CD28- CD8+ subsets were found to be significantly increased. Importantly, we demonstrated the increased baseline activation of caspase-3 and increased lymphocyte apoptosis. CONCLUSION: We suggest that SARS-CoV-2 primarily affects the lymphocytes and not the innate cells. The increased baseline activation of Caspase-3 could make the COVID-19 lymphocytes more vulnerable to cell death. Therefore, this may interrupt the crosstalk between the adaptive and innate immune systems.

Immunological parameters associated with the severity of COVID-19 pneumonia in kidney transplant recipients.

PURPOSE: An outbreak of a novel respiratory disease due to coronavirus species was emerged in 2019 and named as Coronavirus Disease-2019 (COVID-19). Clinical and immunological factors affecting the course of COVID-19 in kidney transplant recipients (KTR) are not well-known. METHODS: In this prospective observational study, we presented 20 KTR with COVID-19 pnemonia and examined the factors predicting the severity of COVID-19. A total of 10 KTR without COVID-19 was used as control group. Lymphocyte subsets were determined by flow cytometry. In 13/20 patients, immunophenotyping was repeated 1 week later. RESULTS: Mean age of the patients was 50 ± 9 years. Patients were classified as mild-moderate (oxygen saturation: SO2 > 90%) and severe disease groups (SO2 ≤ 90%). Serum albumin and hemoglobin were lower and CRP, fibrinogen and peak D-dimer were higher in severe group. Peak CRP was inversely associated with nadir SO2 (r = - 0.68, p = 0.001). Neutrophil/lymphocyte ratio was higher in severe group (p = 0.01). CD3 + and CD4 + cells were lower and NK cell percentage (CD16 + 56 +) was higher in severe group. Percentage of spontaneously activated CD8 cells (CD8 + CD69 +) was higher in severe group. In comparison of KTR with and without COVID-19, CD8 + cells were lower but NK cell percentage was higher in KTR with COVID-19. CONCLUSION: In this pilot study, increased NK cells, activated CD8 + cells and decreased CD3 + and CD4 + cells were associated with severity of COVID-19 in KTR. Peripheral immunophenotyping of lymphocyte subtypes may provide prognostic information about the clinical course of COVID-19 in KTR.