Comparative Study of the VI Polysaccharide Typhoid Vaccines Effectiveness from Local Strain with Commercial Vaccine

Abstract

Typhoid fever, which is caused by Salmonella enterica subspecies enterica serovar Typhi (S. Typhi) is an exclusively human enterically transmitted, range from mild gastroenteritis to severe systemic disease and spread by the fecal-oral route via contaminated food and water.In current study done production of polysaccharide typhoid vaccine against typhoid fever from local strain (S. Typhi). Identification of S. Typhi (local strain) by traditional methods of diagnosis as microscopic examination and biochemical tests as Api20E system diagnosis, Vitek-2 and serological test .All confirmed the identity of the bacteria belonging to the Salmonella Typhi. In current study, polysaccharide was used as immunogen to production typhoid vaccine from local strain and evaluation these vaccine biological, chemical, physical and Immunological with Commercial vaccine and comparative the results, the results of biological test as sterility, safety and pyrogenicity test were conforms. A result of chemical test (phenol content and residual formalin) by using HPLC and GC, PH value and protein content were safety side comparative WHO protocol. On the other hand, the results of physical test present particles size of local typhoid vaccine was less than Com. V. the particle, the smaller the particle size of vaccine supports the immune response increased immunization. The result Immunological test by ELISA was showed that the titration of  PS V. local strain group was high immune response and  significantly differences  (P<0.5) in the sera of treated guinea pigs between first and booster dose, control group was Non-significant. The result of cellular immune response that present in total white blood corpuscles (WBCs) count  showed no significant different of Com. Vaccine and control group between first and booster dose but, there significant different (P<0.05) of PS vaccine between first and booster dose. In challenge test the result was showed 80% and 70% ratio protected in PS and Com groups vaccines respectively and resisted with the virulent enhance challenge exposure against S. Typhi organism after give 100LD50 dose (10⁸) to those animal.In conclusion, can reproduction of Iraqi typhoid vaccine (Killed vaccine) that was produced in VIS and stopped since 2003 by using new vaccine that recommended by WHO for humane immunization against typhoid fever, also possibility use of method evaluation for evaluates commercial typhoid vaccine.

Keywords: (HPLC) High-performance liquid chromatography, (GC)gas chromatography.