Vaccination effect of liposomes entrapped whole cell bacterial vaccine on immune response and disease protection in Epinephelus bruneus against Vibrio harveyi

The protective efficacy of liposomes-entrapped with whole cell bacterial vaccine (WCV) on immune response and protection against Vibrio harveyi infection in Epinephelus bruneus was investigated at weeks 1, 2, and 4. The cumulative mortality was 25% in WCV immunized fish whereas it was 35% and 40% with activated whole cell V. harveyi alone (WC) or liposome alone against pathogen; the mortality was 90% in non-immunization fish against pathogen. Total protein significantly increased in WCV and WC groups on weeks 2 and 4. The albumin, globulin, and albumin:globulin ratio significantly increased in WCV and WC groups on week 4. The antibody titres significantly increased in fish immunized with liposomes-entrapped WCV from weeks 1 to 4 where as in WC group only on week 4. The phagocytic activity significantly enhanced in liposomes-entrapped WCV group on weeks 1 and 2 and all other immunized groups on week 4. The complement activity was significantly enhanced in liposomes-entrapped WCV and WC immunized groups on weeks 2 and 4. However, the lysozyme activity significantly was enhanced in all immunization groups from weeks 1 to 4. These results suggest that fish immunized with liposomes-entrapped WCV and WC alone have the potential to modulate the immune system affording increased protection against V. harveyi infection in kelp grouper.

► The cumulative mortality was 25% in liposome-entrapped WCV immunized fish.
► Total protein significantly increased in liposome-entrapped WCV or WC alone.
► The antibody titres significantly increased in liposome-entrapped WCV.
► The phagocytic activity significantly enhanced in all immunized groups on week 4.
► The lysozyme activity significantly enhanced in all immunization groups from weeks 1 to 4.