Dandan Yi, Aiying Lei, Yu Liu, Guixiang Tong, Ting Huang, Chenyu Quan, Ming Chen, Liping Li
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The results of the backpropagation safety test showed that the S02 strain did not cause disease or death to tilapia after continuous passage for 50 generations. AfterS02 was injected, the immunoglobulin M (IgM) level in the serum was significantly higher than that in the GX005 infection group within 28 days and reached its peak at 14 days. An intraperitoneal injection of 10<sup>9</sup> CFUs/mL of S02 at a dose of 0.2 mL per fish had the best relative protection rate of 92.58%. The whole-genome sequencing results showed that the S02 strain had two large 0.2 Mbp segments of inversion compared to its parent virulence strain GX005, encoding 372 genes, including the virulence genes of the GNAT family N-acetyltransferase and the hyaluronic acid lyase genes of the hysA, hylA, and hylB, which are related to virulence factors.</p><p><strong>Conclusion: </strong>This study provides theoretical data support for the prevention and control of the <i>S. iniae</i> infection in tilapia. The abnormal expression of important virulence genes GNAT family N-acetyltransferase and hyaluronic acid lyase genes hysA, hylA, and hylB caused by the inversion and translocation of large fragments could be the main mechanism for their attenuated virulence. This study provided theoretical support for the prevention and treatment of <i>S. iniae</i> infection in tilapia and the application of S02-attenuated vaccine.</p>","PeriodicalId":12466,"journal":{"name":"Frontiers in Microbiology","volume":"16 ","pages":"1550544"},"PeriodicalIF":4.0000,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12170510/pdf/","citationCount":"0","resultStr":"{\"title\":\"Immunoprotective test and whole-genome sequencing analysis of the attenuated S02 strain of <i>Streptococcus iniae</i>.\",\"authors\":\"Dandan Yi, Aiying Lei, Yu Liu, Guixiang Tong, Ting Huang, Chenyu Quan, Ming Chen, Liping Li\",\"doi\":\"10.3389/fmicb.2025.1550544\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p><strong>Background: </strong><i>Streptococcus iniae</i> is one of the most serious diseases threatening tilapia aquaculture, causing huge economic losses every year. 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引用次数: 0
摘要
背景：牛链球菌是威胁罗非鱼养殖业最严重的疾病之一，每年造成巨大的经济损失。注射减毒疫苗仍然是预防罗非鱼链球菌病的最佳选择。目的：评价猪链球菌S02减毒株的安全性、稳定性、免疫原性、抗体产生时间和免疫剂量，并在全基因组水平上全面分析其减毒的可能机制。结果：S02菌株脱毒后对罗非鱼的致病性完全丧失，具有良好的免疫原性。反向传代安全性试验结果表明，S02菌株连续传代50代后，对罗非鱼无致病或致死现象。注射s02后，血清免疫球蛋白M （IgM）水平在28 d内显著高于GX005感染组，并在14 d达到峰值。以0.2 mL /条鱼腹腔注射109cfus /mL的S02，相对保护率为92.58%。全基因组测序结果显示，菌株S02与其亲本毒力菌株GX005相比有2个0.2 Mbp的大反转片段，编码372个基因，包括GNAT家族n -乙酰基转移酶毒力基因和与毒力因子相关的hysA、hylA、hylB的透明质酸裂解酶基因。结论：本研究为罗非鱼猪链球菌感染的防治提供了理论数据支持。重要毒力基因GNAT家族n -乙酰转移酶和透明质酸裂解酶基因hysA、hylA、hylB因大片段倒位和易位导致的表达异常可能是其毒力减弱的主要机制。本研究为罗非鱼链球菌感染的防治及s02减毒疫苗的应用提供了理论支持。
Immunoprotective test and whole-genome sequencing analysis of the attenuated S02 strain of Streptococcus iniae.
Background: Streptococcus iniae is one of the most serious diseases threatening tilapia aquaculture, causing huge economic losses every year. Injectable attenuated vaccines are still the best choice for preventing streptococcal diseases affecting the tilapia.
Objective: This study evaluated the safety, stability, immunogenicity, antibody production time, and immune dose of the attenuated S02 strain of S. iniae and comprehensively analyzed the possible mechanisms of its attenuated virulence at the whole-genome level.
Results: After detoxification, the S02 strain completely loses its pathogenicity to tilapia and has good immunogenicity. The results of the backpropagation safety test showed that the S02 strain did not cause disease or death to tilapia after continuous passage for 50 generations. AfterS02 was injected, the immunoglobulin M (IgM) level in the serum was significantly higher than that in the GX005 infection group within 28 days and reached its peak at 14 days. An intraperitoneal injection of 109 CFUs/mL of S02 at a dose of 0.2 mL per fish had the best relative protection rate of 92.58%. The whole-genome sequencing results showed that the S02 strain had two large 0.2 Mbp segments of inversion compared to its parent virulence strain GX005, encoding 372 genes, including the virulence genes of the GNAT family N-acetyltransferase and the hyaluronic acid lyase genes of the hysA, hylA, and hylB, which are related to virulence factors.
Conclusion: This study provides theoretical data support for the prevention and control of the S. iniae infection in tilapia. The abnormal expression of important virulence genes GNAT family N-acetyltransferase and hyaluronic acid lyase genes hysA, hylA, and hylB caused by the inversion and translocation of large fragments could be the main mechanism for their attenuated virulence. This study provided theoretical support for the prevention and treatment of S. iniae infection in tilapia and the application of S02-attenuated vaccine.
期刊介绍：
Frontiers in Microbiology is a leading journal in its field, publishing rigorously peer-reviewed research across the entire spectrum of microbiology. Field Chief Editor Martin G. Klotz at Washington State University is supported by an outstanding Editorial Board of international researchers. This multidisciplinary open-access journal is at the forefront of disseminating and communicating scientific knowledge and impactful discoveries to researchers, academics, clinicians and the public worldwide.
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