Yusuke Ushida

Upper respiratory tract infections (URTIs) are highly prevalent and impose substantial individual and societal burdens. Plasmacytoid dendritic cells (pDCs) are major producers of type I interferons (IFNs) with antiviral activity. This study investigated whether CpG oligodeoxynucleotide-induced IFN-α production by peripheral blood mononuclear cells (PBMCs), a marker of pDC activity, was associated with subsequent occurrence of the common cold. Data from 41 healthy adults in the placebo arm of a randomized controlled trial were analyzed. CpG-induced IFN-α production was measured before a 4-week observation period, and participants were dichotomized into high and low IFN-α production groups based on the median value. The occurrence of common cold events and cold symptoms was assessed using daily self-reported symptom scores and body temperature records. Seven participants developed the common cold, all in the low group. The crude risk difference between the low and high groups was 0.333 (Miettinen–Nurminen 95% CI, 0.148–0.546; Fisher’s exact p = 0.009). The low group also showed higher risks for fever, plugged nose, and sore throat, while findings for the other symptoms were less conclusive. As a hypothesis-generating pilot study, these findings suggest that low TLR9-mediated IFN-α production may be associated with increased susceptibility to URTIs in healthy adults.

Background: In recent years, the prevalence of seasonal allergic rhinitis has increased rapidly in Japan, becoming a social problem. Therefore, we evaluated the effect of tablets containing Lacticaseibacillus paracasei KW3110 (L. paracasei KW3110) on allergic symptoms in the nose and eyes.Methods: In a randomized, double-blind, placebo-controlled, parallel-group study, 120 healthy adults with mild to moderate allergic rhinitis ingested either a placebo tablet or a test tablet containing L. paracasei KW3110 for 12 weeks (from January to April). Subjects who did not regularly use medication and experienced nasal and eye discomfort in early spring were selected. Allergic symptoms in the nose and eyes were assessed using subjective symptom surveys and diagnosis by an otorhinolaryngologist.Results: Compared with the placebo group, the L. paracasei KW3110 group showed a significant improvement in the score of “nasal symptoms” (p < 0.05) and “outdoor activities” (p < 0.05) in the Japanese Rhino-conjunctivitis Quality of Life Questionnaire (JRQLQ No.1) at 4 weeks when pollen dispersal begins, and “runny nose” (p < 0.05) in a diary questionnaire on nasal and eye symptoms at 8 weeks. Diagnosis by an otorhinolaryngologist showed a significant decrease in the score of “paroxysmal sneezing or rhinorrhea” (p < 0.05) and “classification of severity of allergic rhinitis symptoms” (p < 0.05) at 4 weeks, and the number of subjects scoring “worse” (p < 0.05) in the efficacy assessment.Conclusion: These findings suggest that intake of L. paracasei KW3110 is effective in alleviating nasal symptoms in subjects with mild to moderate allergic rhinitis, which can be useful for preventing allergic rhinitis without medication.Clinical trial registration: https://www.umin.ac.jp/, identifier UMIN000053239.