ABSTRACT
This study examined the effect of hot-spring bathing (40 to 41°C) on salivary secretion and salivary secretory IgA (sIgA) in healthy volunteers. Ten volunteers (10 men, average 33.6±9.3 years old) bathed in a hot-spring for 10 minutes.<br>Saliva samples were collected before bathing, during bathing (from 5 to 7 min), and after bathing using the Saxon test. The saliva flow rates and sIgA concentration were determined and then the sIgA secretion rates were calculated.<br>The saliva flow rates increased significantly during the bathing (p<0.02) and decreased after bathing. The sIgA secretion rates during bathing were significantly higher than those before and after bathing (p<0.02).<br>The increases in saliva flow rates and sIgA secretion rates during bathing were considered to indicate the improvement of local immunity in the oral cavity and thus considered to be useful for preventing upper respiratory tract infections.
ABSTRACT
Escherichia coli heat-labile enterotoxin (LT) is composed of catalytic A and non-catalytic homo-pentameric B subunits and causes diarrheal disease in human and animals. In order to produce a nontoxic LT for vaccine and adjuvant development, two novel derivatives of LT were constructed by a site-directed mutagenesis of A subunit; Ser63 to Tyr63 in LTS63Y and Glu110, Glu112 were deleted in LT delta 110/112. The purified mutant LTs (mLTs) showed a similar molecular structural complex as AB5 to that of wild LT. In contrast to wild-type LT, mLTs failed to induce either elongation activity, ADP-ribosyltransferase activity, cAMP synthesis in CHO cells or fluid accumulation in mouse small intestine in vivo. Mice immunized with mLTs either intragastrically or intranasally elicited high titers of LT-specific serum and mucosal antibodies comparable to those induced by wild-type LT. These results indicate that substitution of Ser63 to Tyr63 or deletion of Glu110 and Glu112 eliminate the toxicity of LT without a change of AB5 conformation, and both mutants are immunogenic to LT itself. Therefore, both mLTs may be used to develop novel anti-diarrheal vaccines against enterotoxigenic E. coli.