Studies of biological significance of apoptosis upon white-spot syndrome virus infection in penaeid shrimp

การศึกษาความสำคัญทางชีวภาพของการตายของเซลล์แบบอะพอพโทสิสต่อการติดเชื้อไวรัสตัวแดงดวงขาวในกุ้งกลุ่มพีเนียด

Name: Anchukorn Rijiravanich

MeSH: Apoptosis

MeSH: Caspase 3

MeSH: RNA, Double-Stranded

MeSH: White spot syndrome virus 1

Abstract: Apoptosis has long been observed in viral target organs of white-spot syndrome virus (WSSV)-infected shrimp and its level has been reported to increase as the shrimp approach death. Although apoptosis is purported to be an effective anti-viral defense mechanism in invertebrates, its benefits are controversial with respect to shrimp infected with WSSV. While other studies have focused on verifying apoptosis as a host defense mechanism in ‘immune’ or viral resistant/tolerant shrimp, observations of viral epizootics in Thai farming practices have led to an interesting proposal that shrimp mortality due to WSSV infection is a result of triggered apoptosis. This study attempted to investigate if viral triggered apoptosis is protective or detrimental to infected shrimp. First, the mechanism of death protection from WSD by hyperthermia was tested and it has been shown that hyperthermia-induced viral resistance in black tiger shrimp Penaeus monodon is not correlated with apoptosis but is instead a result of the inhibition of virus production. Secondly, reverse genetics (e.g. RNAi) has been applied on a caspase-3 homologue (cap-3), a key protein in induction of apoptosis, from the American white shrimp Penaeus (Litopenaeus) vannamei and wsv390, ORF390 of WSSV (which has been demonstrated to have an anti-apoptotic activity in vitro) to test the earlier proposal. Effects on mortality, apoptosis induction and viral production at low- and high- doses of WSSV were evaluated. In a high-dose WSSV challenge, both cap-3 and wsv390 silencing had no significant effect on WSSV-induced mortality, except for a delay in mean time to death, which was attributed to a non-specific anti-viral response induced by injection of dsRNA. An increase in viral yield was shown in cap-3 RNAi shrimp whereas a decrease was shown in wsv390 RNAi shrimp compared to the viral challenged control and dsRNA treatment control shrimp. A continual increase in apoptosis was detected in hemocytes of cap-3 dsRNA, viral control and dsRNA control shrimp. wsv390 RNAi, however; displayed a significant boost of apoptosis in the beginning and kept steady at that level along the progression of disease. At a low dose WSSV challenge, cap-3 but not wsv390 silencing co-related with a lower level of cumulative mortality, relative to silencing of a control gene. Although more extensive studies will be required to resolve the role of apoptotic response of shrimp to WSSV, this study suggests that cap-3 controls WSSV replication in an apoptosis-independent manner; wsv390 exerts dual roles on regulating host apoptosis and it is necessary for viral replication but not for severity of infection; and finally, apoptosis may exacerbate rather than decrease mortality in WSSV-challenged shrimp.

Mahidol University

Address: NAKHON PATHOM

Email: liwww@mahidol.ac.th

Name: Boonsirm Withyachumnarnkul

Role: Thesis Advisor

Created: 2007

Modified: 2020-11-03

Issued: 2010-06-09

วิทยานิพนธ์/Thesis

application/pdf

CallNumber: TH A539s 2007

eng

DegreeName: Doctor of Philosophy

Level: Doctoral Degree

Descipline: Anatomy

Grantor: Mahidol University

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