Abstract
Aim:Typhoid is one of the most important food and water borne disease causing millions of deaths over the world. Presently, there is no cost effective vaccine available in India. The outer-membrane proteins (Omps) of Salmonella have been exhibited as a potential candidate for development of subunit vaccine against typhoid. The objective of the present study was to evaluate the use of recombinant Omp 28 protein for immunization of rabbit to elucidate its protection against virulent Salmonella Typhi.Materials and Methods:Immune potential of recombinant Omp28 was tested in New Zealand Rabbits. Rabbits were divided into two groups, i.e., control and test group. Control group was injected with phosphate buffer saline with adjuvant while test group were injected with recombinant Omp28 along with adjuvant. Rabbits were bleed and serum was collected from each rabbit. Serum was tested by Enzyme-linked immunosorbent assay (ELISA) for humoral response. Rabbits were challenged with virulent culture to test the protective immunity.Results:Humoral response was provoked at 15th day and maintained till 30th day. The mean ELISA titer at 15th day was 1 : 28000 (mean titer log 10 : 4.4472) and on the 30th day was 1 : 25866 (mean titer log 10 : 4.4127). Protective immune potential of Omp 28 was assessed by challenge studies in rabbits for which vaccinated and control rabbits were challenged with 109 cells of virulent culture of S. Typhi. In control group, out of six, no rabbit could survive after 48 days while in vaccinated group, three out of six rabbit were survived.Conclusion:Immunization of rabbit with recombinant Omp 28 induced a strong humoral response which was exhibited by high antibody titer in ELISA. Subsequently, intraperitoneal homologous challenge of the immunized New Zealand rabbit resulted in lack of significant protection. These findings indicate that Omp 28 though provoked the humoral immunity but could not provide the protective immunity in rabbit model.
Highlights
Typhoid fever is a public health problem with an estimated 22 million cases and 220,000 related deaths occurring worldwide each year [1]
The objective of the present study was to evaluate the use of recombinant outer-membrane proteins (Omps) 28 protein for immunization of rabbit to elucidate its protection against virulent Salmonella Typhi
Protective immune potential of Omp 28 was assessed by challenge studies in rabbits for which vaccinated and control rabbits were challenged with 109 cells of virulent culture of S
Summary
Typhoid fever is a public health problem with an estimated 22 million cases and 220,000 related deaths occurring worldwide each year [1] It is a life-threatening illness caused by Salmonella enterica serovar Typhi. With the advancement of molecular biology polymerase chain reaction (PCR)-based techniques have been extensively used for detection and differentiation of pathogens [2,3,4,5,6] which had made possible to detect the disease in early stages but the development of resistance to antimicrobial agents and the possible reversal of the resistance in S. Typhi has become a significant issue leading to difficulties in the management of disease [7,8].
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