Preparation Of A Haemophilus influenzae Type B/Tetanus Toxoid Conjugate Vaccine By Reductive Amination. II-Assessment Of Its Immune Response In Mice

¹Alaa Shehata, ²Yehia El Mashad, ³Amr S.M. El Sayed and ³Baheya Riad

¹Egyptian Organization for Biological Products and Vaccines (VACSERA), ²Department of Medical Biochemistry, Tanta University, ³Department of Chemistry, Faculty of Science, Cairo University

Haemophilus influenzae type b (Hib) capsular polysaccharide (CPS)/ tetanus toxoid (TT) conjugate vaccine has been previously prepared. At this study chemical binding between CPS and the carrier protein (TT) was assessed by ELISA using hyper immune burro serum raised against Hib CPS. The highest reactivity of this hyper immune serum was found to be against the conjugate when compared to CPS alone, unconjugated CPS + TT mixture and tyraminated CPS. The immune response against Hib CPS using this conjugate vaccine was studied in C57Bl/6J mice. Animals injected with two doses of the conjugate showed better immune response compared to animals injected with CPS. Also, a boosting effect was noticed after injection of a third dose of the conjugate which did not occur after third dose of CPS. The conjugate was found to elicit a level of immune response in mice similar to that elicited by each of three licensed commercially available Hib CPS conjugate vaccines after two doses. The same boosting effect was obtained after injection of a third dose of the conjugate similar to that obtained after injection of a third dose of the licensed vaccines. These results suggest further studies of this conjugate vaccine to be used in Egypt.