Interleukin-1 beta (IL-1ß) as adjuvant enhances the immune effects of Aeromonas veronii inactivated vaccine in largemouth bass (Micropterus salmoides).

Largemouth bass (Micropterus salmoides) has emerged as a significant economic fish species, with a rise in Aeromonas veronii infections in farming. However, research on adjuvants for vaccines against A. veronii in largemouth bass remains scarce. In present study, recombinant largemouth bass IL-1ß (LbIL-1ß) was expressed to explore its adjuvant effect on the A. veronii inactivated vaccine. Following vaccination with recombinant LbIL-1ß (rLbIL-1ß) and the inactivated A. veronii, higher serum SOD levels and lysozyme activities were observed in largemouth bass from inactivated A. veronii + rLbIL-1ß vaccinated group. Furthermore, it was discovered that rLbIL-1ß was able to boost the serum-specific antibody levels induced by the inactivated A. veronii. The qRT-PCR analysis revealed that rLbIL-1ß also enhanced the expression of IgM, CD4, and MHC II in largemouth bass triggered by the inactivated A. veronii. After challenged with live A. veronii, the outcomes demonstrated that the relative percentage survival (RPS) for largemouth bass resulting from the inactivated A. veronii in combination with rLbIL-1ß was 76.67 %, surpassing the RPS of 60 % in the inactivated A. veronii group. Collectively, these findings indicate that rLbIL-1ß enhances the protective effect of the A. veronii inactivated vaccine on largemouth bass, showcasing potential as an adjuvant for further development.

Infection dynamic of Micropterus salmoides rhabdovirus and response analysis of largemouth bass after immersion infection.

Largemouth bass (Micropterus salmoides) is an important economic freshwater aquaculture fish originating from North America. However, the frequent outbreaks of Micropterus salmoides rhabdovirus (MSRV) have seriously limited the healthy development of Micropterus salmoides farming industry. In the present study, a strain of MSRV was isolated and identified from infected largemouth bass by PCR, transmission electron micrograph observation and genome sequences analysis, and tentatively named MSRV-HZ01 strain. Phylogenetic analyses showed that the MSRV-HZ01 presented the highest similarity to MSRV-2021, followed by MSRV-FJ985 and MSRV-YH01. The various tissues of juvenile largemouth bass exhibited significant pathological damage following MSRV-HZ01 immersion infection, and the mortality reached 90%. We also found that intestine was the key organ for MSRV to enter the fish body initially by dynamic analysis of viral infection, and the head kidney was the susceptible tissue of virus. Moreover, the MSRV was also transferred to the external mucosal tissue in later stage of viral infection to achieve horizontal transmission. In addition, the genes of IFN γ and IFN I-C were significantly up-regulated after MSRV infection to exert antiviral functions. The genes of cGAS and Sting might play an important role in the regulation of interferon expression. In conclusion, we investigated the virus infection dynamics and fish response following MSRV immersion infection, which would promote our understanding of the interaction between MSRV and largemouth bass under natural infection.

Protective effect of inactivated hepatitis A vaccine against the outbreak of hepatitis A in an open rural community.

AIM: To evaluate the protective effect of inactivated hepatitis A vaccine (Healive) against hepatitis A outbreak in an emergency vaccination campaign. METHODS: During an outbreak of hepatitis A in Honghe Town, Xiuzhou District, Jiaxing City, Zhejiang Province, two nonrandomized controlled trials were conducted in September 2006. The first trial was to vaccinate 108 anti-HAV negative individuals with close contacts of the patients from September with 1 dose of an inactivated hepatitis A vaccine, Healive. The control group comprised of 115 individuals with close contacts of the patients before September. The second trial was to vaccinate 3365 primary and secondary school students who volunteered to receive a dose of Healive and 2572 students who did not receive Healive serving as its controls. An epidemiological survey was conducted to evaluate the protective efficacy of the vaccine. RESULTS: A total of 136 hepatitis A cases were reported during an outbreak that started in June, peaked in August and September, and ended after December of 2006. After a massive vaccination of school children in September, the number of cases declined significantly. No hepatitis A was detected in the 108 vaccinated individuals with close contacts of patients, whereas 4 cases of hepatitis A were found in the controls. The infection rate of hepatitis A was not significantly different in the individuals with close contacts of patients whether or not they received the vaccine (P = 0.122). No hepatitis A was detected in the 3365 students who received the vaccine, four cases of hepatitis A were found in the controls. The infection rate of students with or without vaccination was significantly different in the students who received the vaccine (0/3365 vs 4/2572, P = 0.035). The protective efficacy of the vaccine was 100%. CONCLUSION: Inactivated hepatitis A vaccine demonstrates a good protective effect against an outbreak of hepatitis A.