Apoptosis of hemocytes is associated with the infection process of white spot syndrome virus in Litopenaeus vannamei.

Previous studies have demonstrated that white spot syndrome virus (WSSV) could induce hemocytes apoptosis in shrimps, however the inter-relationship between apoptotic process and the WSSV infection status is still currently underexplored. In the present work, the apoptosis and the viral proliferation in hemocytes of Litopenaeus vannamei were simultaneously investigated post WSSV infection by two-color immunofluorescence flow cytometry and real-time quantitative PCR. The apoptotic hemocytes of WSSV-infected shrimp was significantly increased at 12 h post infection (hpi), whereas underwent a slight decline at 24 hpi subsequently. Since 24 hpi, the apoptotic rate of hemocytes in the WSSV-infected shrimp exhibited a rapid and significant increase, and reached the peak level at 48 hpi with the ratio of 18.1 ± 2.0%. Meanwhile, the percentage of WSSV-infected hemocytes and WSSV copies in hemocytes significantly increased at 24 hpi and maintained at a high level afterwards. With the rapid increase of hemocytes apoptosis, hemocyte density in hemolymph decreased dramatically to less than 20% of the mean value of control. Co-localization assay showed that the apoptotic WSSV-infected hemocytes occupied the dominant proportion of total apoptotic hemocytes, which reached the peak at 48 hpi with 12.6 ± 1.5%. The expression profiles of seven pro-apoptotic genes and two apoptosis-inhibiting genes showed significant differential responses at different stages of WSSV infection, reflecting the interplay between the virus and the host immune response. Our results demonstrated that the apoptotic response of shrimp hemocytes could be significantly influenced by the WSSV infection process, which might provide an insight into deeper relationships between viral infection and apoptosis.

Tang X ，Cui C ，Liang Q ，Sheng X ，Xing J ，Zhan W ... -  《-》

Analysis and identification of tyrosine phosphorylated proteins in hemocytes of Litopenaeus vannamei infected with WSSV.

Tang X ，Li X ，Zhai F ，Xing J ，Sheng X ，Zhan W ... -  《-》

Single-cell RNA-seq revealed heterogeneous responses and functional differentiation of hemocytes against white spot syndrome virus infection in Litopenaeus vannamei.

Cui C ，Tang X ，Xing J ，Sheng X ，Chi H ，Zhan W ... -  《-》

Shrimp hemocyte homeostasis-associated protein (PmHHAP) interacts with WSSV134 to control apoptosis in white spot syndrome virus infection.

Hemocyte homeostasis-associated protein (PmHHAP) was first identified as a viral-responsive gene, due to a high upregulation in transcription following white spot syndrome virus (WSSV) infection. Functional studies using RNA interference have suggested that PmHHAP is involved in hemocyte homeostasis by controlling apoptosis during WSSV infection. In this study, the role of PmHHAP in host-viral interactions was further investigated. Yeast two-hybrid assay and co-immunoprecipitation revealed that PmHHAP binds to an anti-apoptosis protein, WSSV134. The viral protein WSSV134 is a late protein of WSSV, expressed 24 h post infection (hpi). Gene silencing of WSSV134 in WSSV-infected shrimp resulted in a reduction of the expression level of the viral replication marker genes VP28, wsv477, and ie-1, which suggests that WSSV134 is likely involved in viral propagation. However, co-silencing of PmHHAP and WSSV134 counteracted the effects on WSSV infection, which implies the importance of the host-pathogen interaction between PmHHAP and WSSV134 in WSSV infection. In addition, caspase 3/7 activity was noticeably induced in the PmHHAP and WSSV134 co-silenced shrimp upon WSSV infection. Moreover, PmHHAP and WSSV134 inhibited caspase-induced activation of PmCasp in vitro in a non-competitive manner. Taken together, these results suggest that PmHHAP and WSSV134 play a role in the host-pathogen interaction and work concordantly to control apoptosis in WSSV infection.

Apitanyasai K ，Amparyup P ，Charoensapsri W ，Sangsuriya P ，Tassanakajon A ... -  《-》

Molecular characterization of a novel white spot syndrome virus response protein (dubbed LvWRP) from Litopenaeus vannamei.

White spot syndrome, which is caused by white spot syndrome virus (WSSV), is a highly contagious disease of penaeid shrimp. However, there is currently incomplete understanding of the infection mechanism and pathogenesis of WSSV. In this study, a novel gene of a previously uncharacterized WSSV response protein (LvWRP) in Litopenaeus vannamei was identified and characterized. The LvWRP gene has an open reading frame (ORF) of 879 bp encoding a putative protein of 292 amino acids. Sequence analysis revealed that LvWRP shared 24.9% identity with an uncharacterized protein of Penaeus monodon nudivirus. Real-time qPCR analysis showed that LvWRP was ubiquitously expressed in shrimp tissues, with transcript levels induced in hemocytes upon immune challenge with Vibrio parahaemolyticus, Streptoccocus iniae, lipopolysaccharide (LPS), and WSSV. In addition, RNA interference-mediated knockdown of LvWRP followed by WSSV challenge revealed significant decrease in the transcript levels of WSSV IE1 and VP28 genes coupled with a reduction in WSSV copies in shrimp hemocytes. Moreover, depletion of LvWRP followed by WSSV challenge significantly increased the transcript levels of Vago4 and Vago5 as well as increased the phosphorylation of STAT, while hemocytes apoptosis in terms of caspase 3/7 activity was decreased. These results suggest that LvWRP is important for WSSV replication in shrimp, and therefore one of the vital host factors in WSSV infection.

Gao G ，Lin R ，Tao M ，Aweya JJ ，Yao D ，Ma H ，Li S ，Zhang Y ，Wang F ... -  《-》