We evaluate the efficacy of recombinant DNA vaccine ABA392 against haemorrhagic septicaemia infection through intranasal administration route by targeting the mucosal immunity. The DNA vaccine was constructed and subjected to animal study using the Sprague Dawley (SD) rat. The study was divided into two major parts: (i) active and (ii) passive immunization studies, involving 30 animals for each part. Each group was then divided into five test groups: two test samples G1 and G2 with 50 and 100 µg ml-1 purified DNA vaccine; one positive control G5 with 106 CFU per ml formalin-killed PMB2; and two negative controls, G3 and G4 with normal saline and pVAX1 vector. Both studies were conducted for the determination of immunogenicity by total white blood cell count (TWBC), indirect ELISA and histopathological changes for the presence of the bronchus-associated lymphoid tissue (BALT). Our findings demonstrate that TWBC, IgA and IgG increased after each of the three vaccination regimes: groups G1, G2 and G5. Test samples G1 and G2 showed significant differences (P
Haemorrhagic septicaemia (HS) is a well-known high fatality septicaemic disease happening among bovines. The disease is caused by the Pasteurella multocida serotype B:2 bacteria. P. multocida B:2 has high mortality and morbidity rates and is spread through the intranasal and oral routes in bovines. In this study, our aim was to investigate the efficacy of the recombinant protein vaccine, ABA392/pET30a via intranasal inoculation by targeting the mucosal immunity. The constructed recombinant protein vaccine ABA392/pET30a was subjected to an animal study using Sprague Dawley rats. The study was divided into two parts: active and passive immunization studies. Both studies were carried out through the determination of immunogenicity (using Total White Blood Cell (TWBC) Count with Indirect ELISA) and histopathogenicity, analyzing (Bronchus Associated Lymphoid Tissue (BALT) formation) in lungs. As a result, the IgA and IgG development of both tested groups: group 1 (50μg/mL protein vaccine) and group 2 (100μg/mL protein vaccine) showed equivalent with the positive control group 4 (formalin-killed P. multocida B:2). However, there was a significant difference when compared with the negative control group 3 (normal saline). These results demonstrate that both the protein vaccine at the concentration 50μg/mL and 100μg/mL have the same efficacy as the commercially available positive control vaccine. From the studies, higher concentration of protein vaccine at 100μg/mL showed higher development of both IgA and IgG compared to 50μg/mL protein vaccine. Higher and rapid development of IgA compared to IgG showed that mucosal immunity has been induced through the intranasal administration of the protein vaccine. In addition, leucocytosis was observed at each dose of vaccination showed that the protein vaccine is capable to induce the immune responses of the host. Histopathogenicity studies of the vaccinated groups showed more BALT formation and no severe lesions after challenge compared to the negative control group. Besides, no inflammatory onsite or anaphylactic responses were observed after the intranasal inoculation which proved to be safer and provided longer lasting immunity. Therefore, recombinant protein vaccine ABA392/pET30a could be a potential candidate for intranasal administration which can provoke mucosal immunity against HS disease.
Haemorrhagic septicaemia (HS) is a major disease in cattle and buffaloes, caused by certain serotypes of Pasteurella multocida, mainly B and E serotypes. Frequent HS outbreak has a major impact in many Asian countries, including Malaysia, where farmers encounter economic loss due to low milk production as well as death of their livestock. There are four types of vaccines available; broth bacterins, alum precipitated vaccine, aluminium hydroxide gel vaccine and oil adjuvant vaccine (OAV), but these vaccines can only provide short term immunity and therefore need to be administered annually. Hence, the development of a protein vaccine using recombinant antigen can be a potential candidate for the production of HS vaccine that would give longer immunity. We have successfully cloned the ABA392 gene fragment into a protein expression vector, pET-30a. The protein was expressed from our ABA392/pET30a clone and the immunogenicity of the protein has been tested on rats. This vaccine was able to trigger an immune response and therefore has the potential to be tested as suitable vaccine candidate in future studies. It is envisaged that this subunit vaccine will make a significant contribution in the management of HS among livestock in future.