The Role of Aldehyde Dehydrogenase and Hsp70 in Suppression of White Spot Syndrome Virus Replication at High Temperature

Abstract

High temperature (32 to 33°C) has been shown to reduce mortality in white spot syndrome virus (WSSV)-infected shrimps, but the mechanism still remains unclear. Here we show that in WSSV-infected shrimps cultured at 32°C, transcriptional levels of representative immediate-early, early, and late genes were initially higher than those at 25°C. However, neither the IE1 nor VP28 protein was detected at 32°C, suggesting that high temperature might inhibit WSSV protein synthesis. Two-dimensional gel electrophoresis analysis revealed two proteins, NAD-dependent aldehyde dehydrogenase (ALDH) and the proteasome alpha 4 subunit (proteasome ␣4), that were markedly upregulated in WSSV-infected shrimps at 32°C. Reverse transcription-PCR (RT-PCR) analysis of members of the heat shock protein family also showed that hsp70 was upregulated at 32°C. When aldh, proteasome ␣4, and hsp70 were knocked down by double-stranded RNA interference and shrimps were challenged with WSSV, the aldh and hsp70 knockdown shrimps became severely infected at 32°C, while the proteasome ␣4 knockdown shrimps remained uninfected. Our results therefore suggest that ALDH and Hsp70 both play an important role in the inhibition of WSSV replication at high temperature.White spot syndrome virus (WSSV) is a notorious pathogen in shrimp aquaculture. It has caused huge economic losses since it was first reported in 1992 in East Asia (6), and the virus is presently endemic in many parts of the world. WSSV is an ovoid to rod-shaped, enveloped, double-stranded DNA virus which belongs to the genus "Whispovirus" of the family Nimaviridae (35). The destructiveness of WSSV is partly due to its wide host range, which includes shrimp, crayfish, crabs, lobsters, and copepods (2, 9). In shrimps, mortality can reach 100% in 3 to 10 days after WSSV infection (20).Shrimps are exothermic animals, and unlike the case for endotherms, the body temperature of exotherms is directly susceptible to change depending on environmental conditions. Shrimp culture records show that outbreaks of WSSV are less likely to occur during warm seasons (29, 39), and there is other evidence suggesting that high temperature might protect shrimps from WSSV. Vidal et al. (34) reported that temperatures of 32 to 33°C can significantly reduce mortality in WSSVinfected shrimps. Other research has suggested that the water temperature needs to be maintained at 33°C for only 12 or 18 h per day in order to delay or reduce mortality in WSSV-infected shrimps (26). However, even though the use of warm water for shrimp cultivation has generally been accepted as beneficial by the shrimp culture industry and is already applied in some commercial shrimp farms, the exact mechanisms that underlie this phenomenon are still unknown. Granja et al. (12) proposed that high temperature might increase cell apoptosis and that this would help to prevent the replication of WSSV. However, apoptosis is no longer thought to be a principal protective factor against WSSV in shrimps (10, 40). Others have suggested that high tempera...

Collaboration between a Soluble C-Type Lectin and Calreticulin Facilitates White Spot Syndrome Virus Infection in Shrimp

“…For example, a previous study found that WSSV could consistently promote the synthesis of CRT by 3-fold, regardless of the temperature in a culture of Penaeus monodon (25). Similarly, another report found that CRT protein expression in the stomach of L. vannamei was significantly upregulated by WSSV infection (27).…”

“…4A). Nevertheless, the CRT protein drew our attention, because it was found to be: 1) clearly induced by WSSV infection in many organisms (25)(26)(27); 2) present in the extracellular matrix or on the cell surface, as well as in the endoplasmic reticulum as a chaperone (28); and 3) the receptor of mammalian MBL (29). This background information prompted us to further study the potential role of CRT in the MjsvCL-mediated virus infection.…”

Hsp70 gene polymorphisms in farmed marine shrimp Litopenaeus vannamei populations exposed to white spot disease and infectious myonecrosis

“…In addition to that, induction of Hsp70 gene transcription at 32°C during WSSV infection suggests a connection between this gene and WSSV resistance in shrimp (Lin et al, 2011). In the present study, we have challenged a virus-free population with WSSV, and no significant genetic differences were found between the dead and surviving groups.…”

“…One of the most studied HSPs is the Hsp70, for its ubiquity and essential role in the cell (Morano, 2007). In Litopenaeus vannamei the transcription of the Hsp70 gene is induced at 32°C during white spot syndrome virus (WSSV) infection, suggesting a functional role of HSPs in suppressing virus replication and reducing mortality in WSSV-infected shrimps (Lin et al, 2011).…”

The DNA Virus White Spot Syndrome Virus Uses an Internal Ribosome Entry Site for Translation of the Highly Expressed Nonstructural Protein ICP35

“…dsRNAi technology is widely used in shrimp to systemically suppress expression of a target gene (25)(26)(27)(28), and here, to investigate the importance of ICP35 to WSSV pathogenesis, we used this technology to knock down the expression of icp35 during WSSV infection.…”