Alginate-coated chitosan microparticles encapsulating an oral plasmid-cured live Salmonella enterica serovar Gallinarum vaccine cause a higher expression of interferon-gamma in chickens compared to the parenteral live vaccine.

Salmonella enterica serovar Gallinarum causes a disease in chickens known as fowl typhoid. Interferon-gamma (IFN-γ) has been shown to be crucial in eliminating salmonellosis infection because of its strong association with T-cell responses. This study was undertaken to compare the expression of IFN-γ in chickens generated by different vaccine formulations. Eighty one-day-old Lohmann layer chicks were divided into four groups of 20 birds each for the experiment. This comprised an unvaccinated negative control group (NEG), a group vaccinated with the live 9R vaccine by the injection route (SC), a group vaccinated with alginate-coated chitosan microparticles encapsulating live plasmid-cured S. Gallinarum strain 9 (PC) by the oral route, and a group vaccinated with a weak attenuated live S. Gallinarum strain 9 encapsulated in alginate-coated chitosan microparticles (VM) given orally. Vaccinations were done at 10 and 14 weeks of age followed by challenge at 16 weeks of age. IgG was measured using ELISA. qRT-PCR was used to compare the mRNA fold expression of IFN-γ in the PC, VM and SC groups using the unvaccinated/unchallenged group as the control. There were significant differences in the IgG levels between each vaccinated group and the unvaccinated group (P < 0.05) after booster vaccination and post-challenge. There was 100% protection of the birds in SC and VM groups, 80% protection in PC group and 0% protection in the NEG group. Using 2-ΔΔCT calculation, IFN-γ was more highly expressed in the PC group than in the SC group or VM group. In conclusion, the IFN-γ was more highly expressed in the PC group (though not significantly higher) compared to the SC and VM groups and this could be attributed to the alginate-coated chitosan microparticles which acted as an adjuvant.

Adjuvant effect of Vernonia amygdalina leaf extract on host immune response to hepatitis B virus subunit vaccine.

Aim of the study: Adjuvants can increase the efficiency and reduce the number of required doses for hepatitis B vaccination. Thus the study was designed to investigate whether V. amygdalina leaf extract may be used as an adjuvant to the conventional hepatitis B surface antigen-based vaccine through humoral response analyses. Methodology: The toxicity/safety margin of V. amygdalina was determined using Lorke's method. Immunization was carried out in mice in two phases, phase 1 employed a 3-times vaccination schedule while phase 2 tested 2-times vaccination schedule. The humoral immune response was determined using ELISA test. The total white blood count, different white blood count, aspartate aminotransferase level, alanine aminotransferase level were determined and the body weight of the mice periodically monitored. Results: Our data show that V. amygdalina was not toxic up to the dose of 5000 mg/kg bodyweight (bw). At a concentration of 250 mg/kg bw as an adjuvant in a three times vaccination schedule, it increased IgM, IgG1 and IgA antibody responses. In a 2-times vaccination schedule, 1000 mg/kg of V. amygdalina as an adjuvant to hepatitis B vaccine was able to elicit effective antibody production (0.174±0.002) significantly (P <0.05) higher than the conventional hepatitis B vaccine group (0.109±0.002) which received 3-times vaccine dose. It equally enhanced innate cell-mediated immune response by increasing total white blood cell, neutrophil and lymphocyte counts. The adjuvant-vaccine combination did not produce side effects as the aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were within the normal ranges. The liver excised from the sacrificed mice at the end of the vaccination series showed no sign of congestion, inflammation or colour change. Periodic mice body weight monitoring showed similar growth pattern between the treatment and control groups. Conclusion: Results obtained suggest that V. amygdalina may serve as an effective adjuvant to hepatitis B virus vaccine.

Preliminary evaluation of the immunoenhancement potential of Newcastle disease vaccine formulated as a cationic liposome.

This study evaluates the enhancement of immune response of birds to Newcastle disease (ND) vaccine encapsulated in 1,2-dioleoyl-3-trimethylammonium propane (DOTAP)-based liposomes. The vesicles of the liposomal ND vaccine were physically characterized for shape, particle size and zeta potential. The results of the analyses showed that vesicles of the liposomal ND vaccine were spherical and tightly packed. The mean size distribution was below 100 nm. The mean zeta potential was 24 mV. Sixty experimental birds were then divided into an unvaccinated group, a liposomal ND vaccine group and a live La Sota(®) vaccine group. Both the liposomal ND vaccine and live La Sota(®) vaccine groups were vaccinated orally at 3 and 6 weeks of age. The mean antibody titres, total and differential white blood cell count, and blood chemistry, respectively, were assessed. Ten birds from each group were challenged by oral administration of 0.2 ml virulent Herts 33 strain at 9 weeks of age. The log(2) mean antibody titre induced by the liposomal ND vaccine after secondary immunization of the birds was 9.60±0.95 while that of the live La Sota( (®) ) vaccine was 6.00±0.63. Nine of the 10 challenged birds in the unvaccinated group died while none died from the liposomal ND vaccine group or the live La Sota(®) vaccine group. After the boost vaccination, the chickens vaccinated with the liposomal ND vaccine had a higher mean antibody titre, indicating that encapsulating ND vaccine in DOTAP-based liposome induced significantly higher immunity than the live La Sota(®) vaccine.

Formulation and evaluation of niosomes.

Span 20-based niosome was prepared by lipid film hydration technique and loaded with Newcastle disease vaccine. Three batches with Span 20, cholesterol and dicetyl phosphate in micro molar ratios of 10:10:1; 15:15:1 and 20:20:1 were prepared and evaluated for encapsulation efficiency using haemagglutination test. The morphology of the vesicles was studied by means of transmission electron microscopy. Particle size, zeta potential and polydispersity index were determined by photon correlation spectroscopy using a nanosizer. Adjuvanticity was assessed using haemagglutination inhibition test. The vesicles of Span 20-based niosomes were distinct, near spherical large unilamellar vesicles. The vesicles were of varied sizes (<1000 nm) with the entrapped Newcastle disease vaccine in the core of the vaccine. The zeta potential had a peak at -50 mV. The polydispersity index was 0.68. Haemagglutination inhibition test showed a 71% increment in immune response over that of the marketed La Sota(®) vaccine which had a 60% increment in immune response. The niosomal vaccine did not alter but rather enhanced the immunogenicity of the Newcastle disease vaccine.