Bifidobacterium longum Subsp. infantis Promotes IgA Level of Growing Mice in a Strain-Specific and Intestinal Niche-Dependent Manner.

Throughout infancy, IgA is crucial for maintaining gut mucosal immunity. This study aims to determine whether supplementing newborn mice with eight different strains of Bifidobacterium longum subsp. infantis might regulate their IgA levels. The strains were gavaged to BALB/C female (n = 8) and male (n = 8) dams at 1-3 weeks old. Eight strains of B. longum subsp. infantis had strain-specific effects in the regulation of intestinal mucosal barriers. B6MNI, I4MI, and I10TI can increase the colonic IgA level in females and males. I8TI can increase the colonic IgA level in males. B6MNI was also able to significantly increase the colonic sIgA level in females. B6MNI, I4MI, I8TI, and I10TI regulated colonic and Peyer's patch IgA synthesis genes but had no significant effect on IgA synthesis pathway genes in the jejunum and ileum. Moreover, the variety of sIgA-coated bacteria in male mice was changed by I4MI, I5TI, I8TI, and B6MNI. These strains also can decrease the relative abundance of Escherichia coli. These results indicate that B. longum subsp. infantis can promote IgA levels but show strain specificity. Different dietary habits with different strains of Bifidobacterium may have varying effects on IgA levels when supplemented in early infancy.

Comparison of Serum Total IgA Levels in Severe and Mild COVID-19 Patients and Control Group.

BACKGROUND: The present study aimed to compare serum total IgA levels between severe and mild COVID-19 patients' groups and the control group. METHODS: In this cross-sectional study, 216 definite severe COVID-19 patients (as the inpatient group), 183 subjects with positive specific COVID-19 IgG with mild or no symptoms as the (outpatient group), and 203 healthy subjects with negative specific serology, as the control group were investigated. The cases' laboratory data were collected, and thereafter, statistical tests, including independent samples t test, ANOVA test, and post hoc test, were performed using SPSS software version 22. RESULT: The mean ± SD of IgA in all the included subjects was 2.23 ± 0.78 (g/L). According to the obtained results, there were statistically significant changes in IgA among the three study groups (P value < 0.05). This difference was significant between both outpatient and inpatient groups (P value < 0.05). The mean ± SD of serum IgG in all the subjects was calculated as 15.83 ± 5.73 (g/L). A strong statistically significant change was also seen in IgG among all three groups (P value < 0.001). Of note, there was a significant negative correlation between IgG and IgA total titers of the outpatient group (P value = 0.011*r = - 0.188). CONCLUSION: It was shown that the total serum IgA and IgG levels are significantly associated with the severity of COVID-19 infection. As well, we found that total serum IgA and IgG are associated with the severity of illness. Since a low level of IgA is asymptomatic and high frequent in Iran and other countries, we suggest the evaluation of serum IgA levels in high-risk people and strengthening immune system in subjects with a low level of IgA, in order to reduce the rate of death. In this regard, oral or nasal mucosal vaccines in combination with parenteral vaccination are recommended due to increasing immunity versus COVID-19 by further secretion of the IgA antibody and preventing virus transmission.