Comparison of Immunogenicity and Safety of Selected Adjuvant Formulations for Contagious Caprine Pleuropneumonia Vaccine Improvement

Abstract

Contagious caprine pleuropneumonia (CCPP) is a transboundary disease of goat which is caused by the Mycoplasma capricolum subspecies capripneumoniae (Mccp). Vaccination is the most cost-effective technique in the control of CCPP than any other control measures. Selection of the effective adjuvants is crucial in ensuring the quality of vaccine and its protective efficacy. Saponin is the most commonly used adjuvant, with its shortcomings in its potential for dose related toxicity, low chemical stability, low extraction yield and irritation to laboratory workers. However, the possibility of using oil emulsion adjuvants as an alternative to saponin has not been considered, even though, oil in water adjuvant is relatively safer and cheaper. Therefore, the objective of the present study is to evaluate immunogenicity and safety of selected adjuvant formulations for CCPP vaccine improvement. For this purpose, different adjuvants (15% Emulsigen, 15% Emulsigen-D, 15%Emulsigen-P, 10% Carbigen, 3% saponin and 0.3% saponin) were evaluated on sixty-three healthy and Mccp antibody free goats by classifying in to seven study groups (six experimental groups and one control group), each group consisting of nine goats (n=9). One ml of each vaccine formulation with a different adjuvant was applied to experimental groups and sera samples were collected on days 0, 7, 14, 21, 28, 42, 49 and 56 to assess their immune response using Competitive Enzyme Linked Immune Sorbent Assay (c-ELISA). In addition, adverse effects following the administration of the vaccines were recorded. Thus, the experimental study revealed that 0.3% saponin achieved considerably highest immune response (mean percentage of inhibition [PI] value=74.45), followed by 3% saponin (66.92), Emulsigen (66.90) and Carbigen (66.45). The result did not show statistically (p>0.05, ANOVA) significant difference among them in their efficacy. Emulsigen-P and Emulsigen-D elicited sufficient immune response (mean PI=59.57 and 56.77) in comparison to non-vaccinated groups. On a different note, 3% saponin had posed irritation and high fever in some animals. Carbigen did not develop any reaction including a localized swelling seen in another groups. These findings confirmed that the oil adjuvants, particularly, Carbigen and Emulsigen are valuable to provide a sufficient immune response and better safety. Consequently, it could be concluded that these oil adjuvants can be used as an alternative to saponin in CCPP vaccine.