Gut mucosal immune responses and protective efficacy of oral yeast Cyprinid herpesvirus 2 (CyHV-2) vaccine in Carassius auratus gibelio

Abstract

Cyprinid herpesvirus 2 (CyHV-2) causes herpesviral hematopoietic necrosis (HVHN) disease outbreaks in farmed Cyprinid fish, which leads to serious economic losses worldwide. Although oral vaccination is considered the most suitable strategy for preventing infectious diseases in farmed fish, so far there is no commercial oral vaccine available for controlling HVNN in gibel carp (C. auratus gibelio). In the present study, we developed for the first time an oral vaccine against CyHV-2 by using yeast cell surface display technology and then investigated the effect of this vaccine in gibel carp. Furthermore, the protective efficacy was evaluated by comparing the immune response of a single vaccination with that of a booster vaccination (booster-vaccinated once 2 weeks after the initial vaccination). Critically, the activities of immune-related enzymes and genes expression in vaccine group, especially in the booster vaccine group, were higher than those in the control group. Moreover, strong innate and adaptive immune responses could be elicited in both mucosal and systemic tissues after receipt of the oral yeast vaccine. To further understand the protective efficacy of this vaccine in gibel carp, we successfully developed the challenge model with CyHV-2. Our results showed the relative percent survival was 66.7% in the booster vaccine group, indicating this oral yeast vaccine is a promising vaccine for controlling CyHV-2 disease in gibel carp aquaculture.

Oral Vaccination of Recombinant Saccharomyces cerevisiae Expressing ORF132 Induces Protective Immunity against Cyprinid Herpesvirus-2

“…In rainbow trout vaccinated with an oral vaccine against IHNV, IgT and IgM mRNA level was found to be increased in systemic and mucosal tissues, while IgT expression levels in the hindgut were higher than those in systemic tissues [ 13 ]. A similar phenomenon has also been found in crucian carp vaccinated with an oral yeast vaccine [ 26 ]. Here, IgM and IgT expression levels were promoted in the kidney, spleen, and hindgut post vaccination.…”

“…It was reported that oral delivery of recombinant S. cerevisiae cells could be engulfed by the intestinal epithelial cells of gut in crucian carp, and heterologous protein-specific antibodies could be detected in the serum of vaccinated fish [ 25 ]. This immune response could be rapidly upregulated after booster vaccination [ 26 ]. Results from the present study showed that ORF132 specific antibody in serum was induced after oral administration, and antibody levels in the EBY100/pYD1-ORF132 immunized group were significantly higher than that of the control group.…”

“…The oral yeast vaccine needs to overcome the harsh intestinal environment, bringing about relatively low protection [ 27 ]. Previous studies have shown varying RPS in yeast surface display technology-based vaccines, including 53.3% [ 28 ] and 30% [ 14 ] for CyHV-3, 14.3% (one immunization) and 66.7% (two immunizations) for CyHV-2 [ 26 ], and 45.8% for IHHNV [ 13 ]. Unlike their experiment, two immunizations were performed in this study, each lasting 7 days.…”

Response of immunoglobulin M in gut mucosal immunity of common carp (Cyprinus carpio) infected with Aeromonas hydrophila

“…Previous studies hypothesized that the immune responses induced by mucosal (gut) and parenteral immunization are asymmetrical (73). In a previous study, when antigens were delivered via the gut, mucosal and systemic immune responses were elicited, as demonstrated by an increase in the amounts of circulating IgM (74). In contrast, delivering the dinitrophenol (a model antigen) by intraperitoneal injection resulted in strong systemic responses, whereas mucosal responses were virtually absent (75).…”

Current status and development prospects of aquatic vaccines

“…Subunit vaccines eliminate irrelevant or harmful pathogen components that induce protective immunity while retaining only the effective immunogenic components, resulting in significantly improved and stable immune effects, increased reliability, and fewer adverse reactions in the body. However, they frequently need optional adjuvants and are incapable of producing mucosal and cellular protection ( 36 ). But the plant-produced subunit vaccines are easier to manufacture, transport and store, and the immunization route is simpler and safer.…”