Protection of mice against gastric colonization of Helicobacter pylori by therapeutic immunization with systemic whole cell inactivated vaccines.

The protective effect of therapeutic immunization with heat inactivated Helicobacter pylori cells administered with aluminum phosphate as an adjuvant was evaluated with "Swiss albino mice" infected with H. pylori Sydney strain 1 (SS1). The presence of bacteria in histological sections of the stomach was evaluated to confirm the colonization of H. pylori. The infection dose was determined to be 1 × 108 cells which resulted to be the optimal concentration to sustain infection for required time. Systemic immunization of H. pylori 26695 and SS1 Whole cell heat inactivated vaccine were induced on mice. The IgG titer levels of high dose adjuvant vaccine of both strains were proportionate on the 7th and 14th day. Subsequently on the 21st and 28th day SS1 high dose adjuvant revealed a higher titer value. The Probability values were <0.0001 which is statistically significant. Moreover, therapeutic immunization with SS1 (WC) vaccine confers efficacious protection against H. pylori infection in mice. These results represent strong evidence for feasibility of therapeutic use of whole cell based vaccine formulations against H. pylori infection in animal model.

Process optimization for enhanced production of diphtheria toxin by submerged cultivation.

When stationary culture was replaced by submerged cultivation in a fermentor, a significant increase in the yield of diphtheria toxin in a short cultivation time (less than 48 h as against 7-8 d) was noted. It was found that under optimal conditions of temperature, vortex mixing and surface aeration, an alkaline pH favoured toxin release. Furthermore, to enhance the production volume, two-and three-step semicontinuous batch cultivations were carried out. The toxin produced was of good titre with an adequate antigenic purity. Under optimal conditions, the variation in the Limes of flocculation (Lf titre) was likely due to the quality of the production medium, which in turn depended on the quality of the raw materials used. The process was also optimized in a pilot-scale fermentor.