A whole-cell Lactococcus garvieae autovaccine protects Nile tilapia against infection

• Published in: PloS one Vol. 15; no. 3; p. e0230739
• Main Authors: Bwalya, Patricia, Hang’ombe, Bernard M., Gamil, Amr A., Munang'andu, Hetron M., Evensen, Øystein, Mutoloki, Stephen
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 26.03.2020; Public Library of Science (PLoS)
• Subjects: Animals; Antibodies; Aquaculture; Autopsy; Autovaccines - immunology; Bacteria; Bacterial infections; Biology and Life Sciences; Cichlids - immunology; Cichlids - microbiology; Disease; Diseases; Epidemics; Ethics; Experiments; Farming; Fish; Fish diseases; Fish Diseases - pathology; Fish Diseases - prevention & control; Fish farms; Fisheries; Health aspects; Immunohistochemistry; Infection; Infections; Isolation; Laboratory animals; Lactococcus - physiology; Life sciences; Medical research; Medicine and Health Sciences; Organ Specificity; Organs; Pathology; Research and Analysis Methods; Spleen; Surveillance; Tilapia; Time; Vaccination; Vaccines; Veterinary colleges; Veterinary medicine; Denmark; Zambia; Kariba Lake; Norway; India
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0230739

The autovaccine was produced in-house using a bacterial isolate from a diseased fish from the target farm. Three groups of 150 fish each were injected with either 1) an oil-adjuvanted, inactivated whole cell autovaccine, 2) adjuvant only or 3) PBS (negative control). Approximately 660 degree days post vaccination, the fish were challenged with 9x105 cfu bacteria/fish by intraperitoneal injection and monitored for a further 28 days. Protection against infections was measured by lack of/reduced bacterial loads both by bacterial re-isolation and immunohistochemistry as well as absence of clinical signs/pathology. Significantly less L. garvieae (p<0.03) was re-isolated from either the adjuvant only or control groups compared to the vaccinated group. Furthermore, a significantly high amount (p<0.001) of anti-L. garvieae specific antibodies were observed in the vaccinated group compared to the adjuvant only or control groups at time of challenge. This coincided with protection against infection measured by absence/reduced L. garvieae re-isolation from internal organs, reduced clinical signs and lack of pathology in this group. In the adjuvant only and control groups, bacteria were re-isolated from the kidney, liver, spleen, brain and eyes during the first 14 days. The findings suggest that oil-based vaccines can protect tilapia against L. garvieae infection through an antibody mediated response.