VP24 Is a Chitin-Binding Protein Involved in White Spot Syndrome Virus Infection

Abstract

Oral ingestion is the major route of infection for the white spot syndrome virus (WSSV). However, the mechanism by which virus particles in the digestive tract invade host cells is unknown. In the present study, we demonstrate that WSSV virions can bind to chitin through one of the major envelope proteins (VP24). Mutagenesis analysis indicated that amino acids (aa) 186 to 200 in the C terminus of VP24 were required for chitin binding. Moreover, the P-VP24 186 -200 peptide derived from the VP24 chitin binding region significantly inhibited the VP24-chitin interaction and the WSSV-chitin interaction, implying that VP24 participates in WSSV binding to chitin. Oral inoculation experiments showed that P-VP24 186 -200 treatment reduced the number of virus particles remaining in the digestive tract during the early stage of infection and greatly hindered WSSV proliferation in shrimp. These data indicate that binding of WSSV to chitin through the viral envelope protein VP24 is essential for WSSV per os infection and provide new ideas for preventing WSSV infection in shrimp farms. IMPORTANCEIn this study, we show that WSSV can bind to chitin through the envelope protein VP24. The chitin-binding domain of VP24 maps to amino acids 186 to 200 in the C terminus. Binding of WSSV to chitin through the viral envelope protein VP24 is essential for WSSV per os infection. These findings not only extend our knowledge of WSSV infection but also provide new insights into strategies to prevent WSSV infection in shrimp farms. W hite spot syndrome virus (WSSV) is an enveloped doublestranded DNA (dsDNA) virus belonging to the genus Whispovirus, family Nimaviridae (1). WSSV has caused enormous economic losses to the shrimp farming industry since 1993. Infectious WSSV virions are typically 250 to 380 nm in length and 120 to 150 nm in diameter (2, 3), and they contain a genome of ϳ300 kb that encodes ϳ180 proteins (4, 5).Ingestion of WSSV-infected sick or dead shrimp has been accepted as the major route of natural infection due to the cannibalistic nature of shrimp (6-11). Therefore the digestive tract of shrimp may be a primary site of infection. The digestive tract of shrimp is composed of the esophagus, stomach, midgut, and hindgut. The esophagus, stomach, and hindgut possess a chitinous lining, which is not present in the midgut (12, 13). Instead, the midgut epithelium is generally lined with the peritrophic membrane (PM), which is a noncellular structure surrounding the food bolus. The PM is composed of regularly arranged chitin fibrils embedded in a matrix of proteins, proteoglycans, and mucopolysaccharides (14-17). Therefore, WSSV must cross the PM in the midgut or the chitinous lining in the other parts of the digestive tract to traverse the basal membranes and reach the host cells. We speculate that the interaction between WSSV and chitin may be important for WSSV infection in the shrimp digestive tract.More than 40 WSSV structural proteins have been identified using proteomic methods to date (18)(19)(20). Among them, VP28,...

Crustacean Genome Exploration Reveals the Evolutionary Origin of White Spot Syndrome Virus

“…PF12175; https://pfam .xfam.org/family/PF12175) is composed of three major WSSV structural protein genes: wsv002 (coding for VP24), wsv311 (VP26), and wsv421 (VP28). The three WSS_VP proteins are the most abundant structural proteins and play important roles in establishing infection (27)(28)(29)(30)(31)(32). VP24 and VP28 are the major components of the viral envelope (30,31); VP26 seems to be localized in the viral tegument, or the inner space between the nucleocapsid and the envelope (32).…”

Comparative Efficacy of dsRNA VP24, VP26, RR1 and WSV477 Gene against WSSV Infection in Penaeus monodon

“…P. monodon challenged with VP26 dsRNA conferred 50% survival till the10th day of post viral infection. VP24, the chitin binding protein (Li et al, 2015) play a vital role as an anchor protein with other structural proteins viz. VP28, VP26 and WSV010.…”

Crystal Structure of Major Envelope Protein VP24 from White Spot Syndrome Virus

“…This might suggest different preference of ligand recognition of them. Furthermore, VP24 is considered the core of the infectome, these distinct surface features should reasonably explain the mechanism underlying the different binding property of them with other viral proteins or host protein as previously described1823242526, and further provide insight into their different roles in WSSV assembly and infection.…”