Antiviral action of the antimicrobial peptide ALFPm3 from Penaeus monodon against white spot syndrome virus

The anti-lipopolysaccharide factor isoform 3 (ALFPm3), the antimicrobial peptide from Penaeus monodon, possesses antibacterial and antiviral activities. Although the mechanism of action of ALFPm3 against bacteria has been revealed but its antiviral mechanism is still unclear. To further study how the ALFPm3 exhibits antiviral activity against the enveloped virus, white spot syndrome virus (WSSV), the ALFPm3-interacting proteins from WSSV were sought and identified five ALFPm3-interacting proteins, WSSV186, WSSV189, WSSV395, WSSV458, and WSSV471. Only the interaction between ALFPm3 and WSSV189, however, has been confirmed to be involved in anti-WSSV activity of ALFPm3. Herein, the interactions between ALFPm3 and rWSSV186, rWSSV395, rWSSV458, or rWSSV471 were further analyzed and confirmed by in vitro pull-down assay. Western blot analysis and immunoelectron microscopy showed that the uncharacterized proteins, WSSV186 and WSSV471, were nucleocapsid and envelope proteins, respectively. The decrease of shrimp survival after injection the shrimp with mixtures of each rWSSV protein, rALFPm3 and WSSV as compared to those injected with rALFPm3-neutralizing WSSV was clearly observed indicating that all rWSSV proteins could interfere with the neutralization effect of rALFPm3 on WSSV similar to that reported previously for WSSV189. Morphological change on WSSV after incubation with rALFPm3 was observed by TEM. The lysed WSSV virions were clearly observed where both viral envelope and nucleocapsid were dismantled. The results lead to the conclusion that the ALFPm3 displays direct effect on the viral structural proteins resulting in destabilization and breaking up of WSSV virions. •The interactions between ALFPm3 and its interacting proteins, WSSV186, WSSV395, WSSV458, and WSSV471 were confirmed.•WSSV186 and WSSV471 proteins are structural proteins located on WSSV-nucleocapsid and -envelope, respectively.•All ALFPm3-interacting proteins could interfere with the WSSV-neutralizing activity of rALFPm3.•The ALFPm3 performed its anti-WSSV action by binding to the target structural proteins complex leading to WSSV virion damage.