Evaluation of ribosomal P0 peptide as a vaccine candidate against Argulus siamensis in Labeo rohita

Abstract

Argulus spp. are important ectoparasites of fish, and the current approach of their control using chemical pesticides has numerous drawbacks. Vaccination is a promising alternative but identification of protective antigens is a limiting step. The ribosomal protein P0, essential for protein synthesis, has been studied as a vaccine candidate. We generated sequence information of the P0 protein of the ectoparasite Argulus siamensis and the host Labeo rohita. The region of the parasite P0 protein with less sequence similarity with that of the host P0 protein and high predicted antigenicity was used for peptide synthesis. The peptide was conjugated with keyhole limpet hemocyanin (KLH) for immunization of rohu at a dose of 1.5 μg/g body weight. Dot blot assays confirmed production of antibodies against pP0-KLH in immunized fish. We evaluated the efficiency of pP0-KLH as a vaccine antigen by challenge of the immunized fish with A. siamensis. Although there was no significant difference in parasite load between both groups, a reduced and delayed mortality of 59% (15 days post-infection) in immunized group was noticed as compared to 75% mortality (within 7–15 days post-infection) in control group. The partial protection observed indicated the need for further optimization of this molecule to develop it into a vaccine candidate.

Keywords

• argulus siamensis
• antigen
• ectoparasite
• labeo rohita
• ribosomal proteins
• vaccine