Development of an attenuated oral vaccine strain of tilapia Group B Streptococci serotype Ia by gene knockout technology.
Fish Shellfish Immunol
; 93: 924-933, 2019 Oct.
Article
in En
| MEDLINE
| ID: mdl-31374315
ABSTRACT
Our previous studies demonstrated that the deletion of D2 fragment in tilapia Streptococcus agalactiae(GBS) attenuated strain YM001 is the main reason for the loss of virulence to tilapia. In this study, a Δ2 mutant that deletion of D2 fragment in parental virulent strain HN016 was constructed, and the safety, stability, immunogenicity, and growth characteristics, as well as the virulence mechanism of Δ2 mutant were evaluated. The results showed that Δ2 mutant was not pathogenic to tilapia, and the virulent revertants were not observed after 50 generations of passage. The RPS reached 96.11% at 15 days and 93.05% at 30 days, respectively, after intraperitoneal injection, while RPS reached 74.80% at 15 days and 53.16% at 30 days, respectively, after oral immunization. The growth of Δ2 mutant was significantly faster than YM001, and genes that were enriched in the nitrogen metabolism and arginine biosynthesis signaling pathway (arc, glnA, and gdhA) were identified as important candidate genes responsible for growth rate of S. agalactiae. The absence of D2 fragment affected the expression of Sip, therefore influencing the bacterial virulence. Altogether, this study demonstrated that deletion of D2 fragment in HN016 causes the loss of virulence to tilapia, and Δ2 mutant is a promising, better attenuated oral vaccine strain of S. agalactiae compared to YM001.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Streptococcal Infections
/
Streptococcus agalactiae
/
Bacterial Vaccines
/
Base Sequence
/
Sequence Deletion
/
Cichlids
/
Fish Diseases
Type of study:
Prognostic_studies
Limits:
Animals
Language:
En
Journal:
Fish Shellfish Immunol
Journal subject:
BIOLOGIA
/
MEDICINA VETERINARIA
Year:
2019
Document type:
Article
Affiliation country: