Preparation of Polyclonal Antiserum to the Recombinant TiLV-S8 Protein and Its Application in the Detection of Naturally Tilapia Lake Virus (TiLV) Infected Tilapia

Tilapia lake virus (TiLV) is classified as a negative-sense, single-stranded RNA virus in the family Amnoonviridae. It is an enveloped virus with 10 genomic RNA segments, each coding for a protein. TiLV causes disease in tilapia, and outbreaks can lead to significant economic losses for the tilapia aquaculture industry. In this study, the gene encoding the segment 8 protein of TiLV was cloned into the expression vector pET15-b and then transformed into Escherichia coli strain BL21. After induction, the recombinant TiLV-S8 protein (rTiLV-S8), with a molecular mass of 20 kDa, was expressed, purified, and used to immunize mice. The mouse antiserum against rTiLV-S8 protein demonstrated specific immunoreactivity for the viral protein, approximately 19 kDa in TiLV-infected fish tissues, as determined by Western blotting. According to the results of the dot blotting assay, the antiserum was about 80 times less sensitive than one-step RT-PCR in detecting TiLV in homogenates of infected fish samples and showed no cross-reaction with uninfected fish tissues, other common fish viruses, or prevalent bacterial species found in aquatic animals. Furthermore, this polyclonal antiserum could be employed to identify TiLV-infected fish in the field using dot blotting assay, and the results can be confirmed by immunohistochemistry

Emergency response to emerging disease: AHPND in shrimp

Outbreaks of acute hepatopancreatic necrosis disease (AHPND) have caused great economic losses to many shrimp producing countries in Asia since its first appearance in 2009. The causative agent was first reported in 2013 as specific isolates of Vibrio parahaemolyticus (VPAHPND) that were later found to harbor a plasmid (pVA) encoding the Pir-like binary toxin genes PirvpA and PirvpB. More recent information indicates that pVA plasmid and variants occur in many Vibrio parahaemolyticus serotypes and also in other Vibrio species such as V. campbellii, V. harveyi and V. owensii. Information on such genomic and proteomic studies of different VPAHPND isolates from different countries are reviewed. A cohort study carried out in Thailand in 2014 indicated that AHPND outbreaks account for only a portion of the disease outbreaks reported by shrimp farmers as outbreaks of early mortality syndrome (EMS). It is urgent that the etiology of the other EMS-associated mortalities be investigated and not be overlooked. It is recommended that a regional research network and surveillance program for newly-emerging or re-emerging pathogens be established to speed up the process of diagnosis and the implementation of coordinated control measures and to avoid a repeat of the EMS/AHPND scenario