Abstract
White spot syndrome virus (WSSV) is a major pathogen of penaeid shrimp. Here we identified a new WSSV strain, WSSV-CN04, from naturally infected Marsupenaeus japonicus. Whole genomic sequencing results indicate that the WSSV-CN04 genome was 281 054 bp in length, and encoded 157 hypothetic proteins. The genome sequence of WSSV-CN04 was most closely related to the low-virulent strain WSSV-CN03, sharing 97.5% sequence identity. Notably, in WSSV-CN04, the major envelop protein VP24 was not only truncated but also absent in the virions. Since VP24 was previously reported to be essential for WSSV per os infection by mediating WSSV-chitin interaction, we further analyzed the peroral infection of WSSV-CN03 and -CN04 in Litopenaeus vannamei, and show that the infectivity of WSSV-CN04 was significantly lower than that of WSSV-CN03. When compared with WSSV-CN03-infected shrimp, fewer virions were detected in the digestive tract tissues of WSSV-CN04-infected shrimp at 4 hours post-infection (hpi), and the viral titers in the animals at 24 hpi were much lower. Moreover, a peptide corresponding to VP24 chitin-binding domain reduced the amount of WSSV-CN03 in the midgut to a level similar to that of WSSV-CN04 at 4 hpi. These findings indicate that the truncation of VP24 may attenuate the peroral infectivity of WSSV-CN04, and therefore verify the important role of VP24 in WSSV per os infection.
Highlights
White spot syndrome virus (WSSV) is a major viral pathogen that affects shrimp aquaculture all over the world [1, 2]
The genomic sequence identities between WSSV-CN04 and the seven other WSSV isolates were determined by pairwise alignment; WSSV-CN04 shared the highest identity (97.5%) with WSSV-CN03
Comparative genomic analysis of WSSV‐CN03 and ‐CN04 Because the genome of WSSV-CN04 is most closely related to that of WSSV-CN03, the genomic sequences of WSSV-CN3, and CN04 were further aligned with the “align whole genomes” function of MAUVE (Figure 1A)
Summary
White spot syndrome virus (WSSV) is a major viral pathogen that affects shrimp aquaculture all over the world [1, 2]. The virus infects multiple crustacean species including penaeid shrimp, crayfish, crab and lobster [4,5,6,7]. WSSV can cause up to 100% cumulative mortality within 3–10 days of infection [3]. Different WSSV isolates have been isolated from either penaeid shrimp or crayfish (Table 1), and the complete genome sequences have been determined for seven of them: WSSV-CN [8], WSSV-CN01, WSSVCN02, WSSV-CN03 [9], WSSV-TH [10], WSSV-TW [11], WSSV-KR [12].
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