Association between serum chitinase level and toll-like receptor polymorphisms in bakery workers

Background and objectives: Bakery workers are exposed to wheat allergens, bacterial endotoxins and fungus, which interact to induce allergic responses and work-related respiratory symptoms (WRSs). Our previous studies demonstrated that the WRSs of bakery workers were associated with TLR4 polymorphisms as well as Th2 immune responses, indicating a possible involvement of innate immune responses in the pathogenic mechanisms of baker’s asthma. We hypothesized that Chitinase in wheat flour may involve in the development of WRS in bakery workers. We measured serum Chitinase level in bakery workers and analyzed associations with TLR4 polymorphisms in a single cohort of bakery workers. Methods: Three hundred eighty three bakery workers and as controls, 106 unexposed healthy subjects were enrolled. WRSs were evaluated using a questionnaire survey.  Serum levels of Chitinase, IL-18, MPO and specific IgE/IgG antibodies to wheat flour extracts were measured by ELISA. The promoter polymorphisms of TLR4 at -2027AG and -1608TC were genotyped. Results: Serum Chitinase levels were significantly higher in bakery workers than in unexposed controls (P=0.026), however, no significant differences were noted according to the presence of WRSs and the prevalence of serum specific IgE or IgG antibodies to wheat flour (P>0.05, respectively). The workers carrying TLR4 -2027GG had significantly higher Chitinase levels than those with TLR4 -2027 AA/GG (P=0.021). Haplotype analysis indicated that the workers with ht1 [AT] had significantly higher Chitinase level that those without it (P=0.22). A significant correlation was found between serum Chitinase and IL-18 level (P=0.021), while no significant correlation was found with serum MPO level. Conclusions: These findings suggest that Chitinase may contribute to develop WRSs in bakery workers through the modulation of TLR4 function.