The Regulatory Effect and Molecular Mechanism of the Anti-Lipopolysaccharide Factor-like Gene on the Resistance of Shrimp (Litopenaeus vannamei) to White Spot Syndrome Virus Infection

Anti-lipopolysaccharide factors (ALFs) are an important molecular category within the antimicrobial peptide family. They play a crucial role in resisting pathogen infections and are of importance in the innate immune system of shrimp. A novel <i>ALF-like</i> gene was identified from <i>L. vannamei</i> in this study. Its expression profile was investigated after WSSV infection. Results demonstrated that the mRNA transcription level of the <i>ALF-like</i> gene was significantly upregulated in hemocytes, hepatopancreas, gills, and intestines of <i>L. vannamei</i>. When the mRNA transcription level of the <i>ALF-like</i> gene was inhibited, the expression levels of key WSSV genes (<i>VP 28</i> and <i>IE 1</i>) were significantly upregulated, accompanied by a decrease in shrimp survival rate. Meanwhile, the expression of genes involved in the apoptotic pathway (<i>Lv-Caspase 3</i>, <i>Lv-Caspase 8</i>, and <i>Lv-Bcl 2</i>) and antioxidant enzyme pathway (<i>Lv-GST</i>, <i>Lv-CAT</i>, <i>Lv-Prx</i>, <i>Lv-GPX</i>, and <i>Lv-SOD</i>) was also significantly increased. Flow cytometry further revealed that the hemocyte apoptosis rate induced by WSSV infection was reduced when the transcription level of the target gene was inhibited. These results indicate that the <i>Lv-ALF-like</i> gene plays an important regulatory role in the resistance of <i>L. vannamei</i> to WSSV infection, and studying the function of this gene is of great significance for disease prevention and control of shrimp.