Abstract
Immersion vaccination relies on the response of fish mucosa-associated lymphoid tissues, the Crucian carp (Carassius auratus) and Grouper (Epinephelus coioides) were researched in this paper to examine local mucosal immune responses and associated humoral system responses following immersion vaccination. We administered 1.5 × 107 CFU/ml formalin-inactivated Vibrio harveyi cells and measured mucus and serum antibody titers as well as IgM, MHC II mRNA levels in immune organs. The mucosal antibody response preceded the serum response indicating a role for local mucosal immunity in immersion vaccination. IgM and MHC II mRNA levels were relatively greater for the spleen and head kidney indicating the importance and central position of systemic immunity. Expression levels were also high for the gills while skin levels were the lowest. IgM and MHC II mRNA levels were altered over time following vaccination and the hindgut, liver and spleen were similar indicating a close relationship, so the absolute value of r is used to analyze the correlation among different organs immunized. It can be inferred the existence of an internal immune molecular mechanism for Immune synergy hindgut-liver-spleen, from the peak time (14th day), the relative ratio of genes expression in the same tissues between the immunized grouper and the control group (26 times), and Pearson correlation coefficient (0.8<|r|<1). Injection challenges with live V. harveyi indicated that the relative protection rates for the crucian carp and Grouper was basically the same at 44.4% and 47.4%, respectively. It is believe that crucian carp may be used as a substitute for the valuable grouper in immunity experiment, just from aspect of the relative percent survival (RPS) and how it changes with time. But they were not consistent about the IgM mRNA expression between that of crucian carp and grouper after immersion the Vibrio vaccine.
Highlights
Immersion vaccination has numerous advantages over traditional methods including minimal pain for the fish, lower labor costs, and time coupled with greater operator safety especially for large numbers of small fish
The antibody titers in carp skin mucus peaked on day 7 and declined and returned to pre-immunization levels by week 3
Many studies on immersion vaccination in fish have been reported in recent years [1,2,3], injection immunization technology is still the mainstream of application in the worldwide application [2, 3, 8, 20, 25, 26], whether manual injection or mechanical injection [25, 26]. because immersion vaccination has numerous advantages over the injection methods including minimal pain for fish, lower labor costs and time coupled with greater operator safety especially for large numbers of small fish [2, 3, 18]
Summary
Immersion vaccination has numerous advantages over traditional methods including minimal pain for the fish, lower labor costs, and time coupled with greater operator safety especially for large numbers of small fish. Mucosal surfaces of fish, including skin, gill, and gut, contain numerous immune substances poorly studied that act as the first line of defense against a broad spectrum of pathogens [6], and these organs provide the local immune responses required for a competent immune system in fish. IgT/Z is thought to be specialized in mucosal immunity, but as known that there is not every teleost species possesses these isotypes Ig [3, 9] This suggested that IgM was the most important mediator in the fish specific humoral and mucosal immune responses [3, 8,9,10]
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