广东海洋大学学报2025，Vol.45Issue(6)：1-12,12.DOI:10.3969/j.issn.1673-9159.2025.06.001
小球藻表达LrrG抗原罗非鱼口服疫苗的免疫保护效果
Immune Protection of Recombinant Chlorella Expressing LrrG Antigen on Tilapia
摘要
Abstract
[Objective]This study aims to develop an oral vaccine which is high efficiency,safety,residue free and easy to roll out for the prevention and treatment of Streptococcus agalactiae disease in tilapia(Oreochromis spp.).[Method]The surface antigen gene of S.agalactiae outer membrane protein LrrG_epitope(706-756)was constructed into the expression vector pCAMBIA1302 to obtain the recombinant plasmid,which was then transformed into Chlorella vulgaris HOC5.Positive algal strains were screened using the antibiotic hygromycin and identified by PCR.Positive algal strains were cultured on large-scale,and made into immune oral feed(containing mass fraction 50%recombinant algal strains).Domesticated GIFT tilapia(Oreochromis niloticus)were fed with the immune feed for 28 days to investigate the distribution of immune-related genes in liver and midgut tissues,non-specific serum immune indicators,and serum antibody titer.The growth performance of tilapia(body weight,body length,weight gain rate,feed conversion ratio)was determined.After determining the median lethal dose(LD50)of S.agalactiae to tilapia,a challenge test was conducted on tilapia after 28 days of immune feeding,and the mortality rate and relative protection rate within 14 days were calculated.The external signs of fish,as well as the microscopic characteristics of gills and midgut,were observed.[Results]Successfully constructed recombinant plasmid pCAMBIA1302-LrrG_epitope(706-756),and obtained recombinant microalgae(oral vaccine)through transformation.The recombinant plasmid pCAMBIA1302-LrrG_epitope(706-756)was successfully constructed and recombinant microalgae(oral vaccine)was obtained using electroporation.The expression levels of 9 immune-related genes(IgM,TNF,IFN,MHCⅠ,MHCⅡ,CD4,CD8,IL-1β,IL-10)in liver and midgut of tilapia fed on the immune feed were significantly higher than those fed on normal diet(the control)(P<0.05).The immune feed did not significantly affect the growth performance of tilapia(P>0.05),and there were no significant differences in weight gain rate and feed conversion rate on 28th day(P>0.05).Within 14 days after challenge,the mortality rate of the immune group was consistently lower than that of the control group,the survival rate was significantly higher,and the relative protection rate was 80.18%.The immune group did not show obvious surface lesions in the immune group,whereas the positive control group showed typical symptoms of S.agalactiae disease.Microscopic observation revealed no obvious lesions in the gill and midgut tissues of the immune group,while the gill tissues of the positive control group were ulcerated and the midgut tissues showed hyaline degeneration.[Conclusion]This study successfully developed an oral tilapia vaccine based on the microalgae expression system,which has a highly immunoprotective effect without affecting growth performance.关键词
吉富罗非鱼/无乳链球菌/小球藻/外膜蛋白/疫苗/口服免疫Key words
GIFT Oreochromis niloticus/Streptococcus agalactiae/Chlorella/outer membrane protein/vaccine/oral immunization分类
农业科技引用本文复制引用
肖子淳,胡永华,邓晓东,许殿龙,穆丹,费小雯..小球藻表达LrrG抗原罗非鱼口服疫苗的免疫保护效果[J].广东海洋大学学报,2025,45(6):1-12,12.基金项目
海南省种业实验室资助项目(B24H10034) （B24H10034）
农业农村部财政专项(NFZX2024) （NFZX2024）
