Cellular and humoral immunity assessment in recovered COVID-19 Iraqi dentists

Background: Dentists, safeguarding against contagious diseases, face infection risks. The study aimed to assess post-COVID immunity, quantification of salivary biomarkers for prognostication, and immune surveillance. Materials and methods: A cross-sectional study was done on 91 working Iraqi dentists from June to August 2022. The dual IgG s1 &n, and IgA s1 &n specific to COVID-19 were measured by ELISA-specific kits from serum and saliva. From randomly selected 36 out of 91 participants CD4 and subtypes TH1 and TH2 were counted by flow cytometry from fresh whole peripheral blood. Results: All CD4, Th1, and Th2 percentage levels were reduced as a whole if compared to known normal value, and Th2 elevated and inhibited the level of Th1 in all study individuals. All cells were significantly associated with a positive history of COVID-19 infection whereas the CD4 was significantly related to the Pfizer type of vaccine, loss of both sense and recovery time within 15 days. A positive correlation was found between CD4 and Th2 and CD4 with IgG n in serum; this antibody was highly significant with positive COVID-19 infection higher than that of serum IgG s1. Noticeably, the IgA (s+n) in serum was associated with a positive history of infection and could be detected in individuals with a duration of the last infection >1-2 years and last vaccine duration > 6- 12 months. Conclusion: A low percentage level of CD4 and an imbalance Th1/Th2 ratio made the recovered individual more susceptible to re-infection but the significantly high percentage of specific COVID antibodies followed one time of infection or booster vaccine dose gave their protection.