Two novel C-type lectins with a low-density lipoprotein receptor class A domain have antiviral function in the shrimp Marsupenaeus japonicus

C-type lectins (CTLs) are pattern-recognition receptors (PRRs) that play important roles in immune response. In this study, two new CTLs containing a low-density lipoprotein receptor class A domain (LDLR) and a carbohydrate recognition domain (CRD) were identified in Marsupenaeus japonicus and designated as LdlrLec1 and LdlrLec2. The two CTLs expressed in all the tested tissues of shrimp, however, LdlrLec1 was mainly expressed in hemocytes, heart, gill and intestines, whereas LdlrLec2 was expressed in hepatopancreas and heart. The expression patterns of both LdlrLec1 and LdlrLec2 mRNA were obviously upregulated upon white spot syndrome virus (WSSV) challenge. Injection of recombinant LdlrLec1 or LdlrLec2 into shrimp inhibited WSSV replication, whereas knocking down the expression of LdlrLec1 and LdlrLec2 by RNA interference increased WSSV replication in vivo. The infection rates of WSSV incubated with LdlrLecs were reduced significantly compared with the control group. The LdlrLec proteins could interact with VP28, a major envelope protein of WSSV, which is necessary for the attachment and penetration of WSSV into shrimp cells. These results indicate that LdlrLec1 and LdlrLec2 may function in antiviral response by binding to WSSV and inhibiting their pervasion and replication in shrimp.