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ARS Home » Southeast Area » Auburn, Alabama » Aquatic Animal Health Research » Research » Publications at this Location » Publication #308255

Title: A microwave-irradiated Streptococcus agalactiae vaccine provides partial protection against experimental challenge in Nile tilapia, Oreochromis niloticus

Author
item PASNIK, DAVID - Animal And Plant Health Inspection Service (APHIS)
item Evans, Joyce
item Klesius, Phillip

Submitted to: World Journal of Vaccines
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/22/2014
Publication Date: 11/30/2014
Publication URL: https://handle.nal.usda.gov/10113/60500
Citation: Pasnik, D.J., Evans, J.J., Klesius, P.H. 2014. A microwave-irradiated Streptococcus agalactiae vaccine provides partial protection against experimental challenge in Nile tilapia, Oreochromis niloticus. World Journal of Vaccines. 4:184-189.

Interpretive Summary: Microwave irradiation, as opposed to formalin (chemical) exposure, has not routinely been used in the preparation of killed vaccines despite the advantages of decreased chemical toxicity, ability to kill cells quickly, ease of completion requiring only a standard microwave, and potential increased protein conservation during irradiation. We evaluated the potential of microwave irradiation versus formalin fixation of bacteria to improve Streptococcus agalactiae vaccine protection in 5 gr fish by intraperitoneal (IP) injection and bath immersion (BI). There was no significant difference in the cumulative percent mortality (CPM) post-challenge between fish administered microwave-killed cells (MKC) or formalin killed cells (FKC) within the BI (p < 0.2026) or IP (p < 0.1372) trials. These results indicate that the MKC vaccine may become a non chemical alternative to FKC in vaccination.

Technical Abstract: Microwave irradiation, as opposed to formalin exposure, has not routinely been used in the preparation of killed vaccines despite the advantages of decreased chemical toxicity, ability to kill cells quickly, ease of completion requiring only a standard microwave, and potential increased protein conservation during irradiation. We evaluated the potential of microwave irradiation versus formalin fixation of bacteria to improve Streptococcus agalactiae vaccine efficacy in 5 gr fish by intraperitoneal (IP) injection and bath immersion (BI). There was no significant difference in the cumulative percent mortality (CPM) post-challenge between fish administered microwave-killed cells (MKC) or formalin killed cells (FKC) within the BI (p < 0.2026) or IP (p < 0.1372) trials. The CPM in fish sham-vaccinated with tryptic soy broth (TSB) was significantly higher than both the FKC and MKC CPM in the IP trial and the FKC CPM (p < 0.0019) in the BI trial. Serum obtained from fish prior to vaccination exhibited minimal anti-S. agalactiae antibody activity. Thirty days after vaccination and just prior to challenge, the optical density (OD) levels of the FKC and MKC groups in the IP trials were significantly higher (p < 0.0001) than that of the TSB group. None of the groups in the BI trial exhibited significantly different OD levels post vaccination. Fourteen days after the challenge, the OD levels of all groups in both trials increased significantly above their pre-challenge levels. Both the FKC and MKC IP groups (p < 0.0001) and only the FKC BI group (p < 0.0351) had significantly increased OD level above that of the corresponding post-challenge TSB group. These results indicate that the FKC vaccine provides marginally greater protection and increased antibody concentrations than the MKC vaccine by BI and the MKC vaccine may become a non chemical alternative to FKC in vaccination.