T. Rajkumar

RETRACTED: Chitosan tripolyphosphate (CS/TPP) nanoparticles: Preparation, characterization and application for gene delivery in shrimp

The present study examines the use of CS/TPP nanoparticles for gene delivery in different tissues of shrimp through oral route. The viral gene of WSSV was used to construct DNA vaccines using pcDNA 3.1, a eukaryotic expression vector and the constructs were named as pVP28. The CS/TPP nanoparticles were synthesized by ionic gelation process and these particles were characterized. The structure and morphology of the nanoparticles were studied by field emission scanning electron microscopy (FE-SEM) and FTIR (Fourier Transform Infrared Spectra). The cytotoxicity of CS/TPP nanoparticles was evaluated by MTT assay using fish cell line. The expression of gene was confirmed by Immuno-dot blot, ELISA and RT-PCR analyses. The results indicate that DNA can be easily delivered into shrimp by feeding with CS/TPP nanoparticles.

Studies on the occurrence of infectious myonecrosis virus in pond-reared Litopenaeus vannamei (Boone, 1931) in India

Whiteleg shrimp, Litopenaeus vannamei, with clinical sign of muscle opaqueness with reddish colour at the distal abdominal segments were observed in farms located in West Bengal State, India. The mortality of shrimp in all disease outbreak ponds ranged from 20% to 50%, and mortality increased gradually. The RT-PCR assay of these samples using primer sets specific to infectious myonecrosis virus (IMNV) revealed its presence in the disease outbreak ponds. The IMNV infection was reproduced in healthy shrimp by intramuscular injection to satisfy Rivers postulates. The virus caused mortality in intramuscularly challenged shrimp, but failed to cause mortality by oral route. Tissue distribution of IMNV in infected shrimp by RT-PCR assay revealed the presence of this virus in haemolymph, gill, hepatopancreas and muscle. This study confirms that the disease outbreak which occurred in the shrimp farms located at Purba Medinipur District, West Bengal, India, was due to IMNV.

Ontogenetic changes in the expression of immune related genes in response to immunostimulants and resistance against white spot syndrome virus in Litopenaeus vannamei

Abstract In recent years, researchers have focused on viral and plant immunostimulants which could have beneficial effects in disease prevention and control in shrimp culture. At present, the application of the recombinant VP28 protein (r‐VP28) and herbal immunostimulant has been considered as a more effective approach to prevent white spot syndrome (WSS) by enhancing the immune response in shrimp. In the present study, expression of selected immune related genes in response to r‐VP28 and herbal immunostimulant mix (HIM) were separately studied qualitatively and quantitatively by RT‐PCR and real time PCR, respectively during ontogenetic development from nauplius to juvenile stage in Litopenaeus vannamei. The mRNA expression level of immune related genes such as anti‐lipopolysaccharides (ALF), Lysozyme, cMnSOD, Crustin, Prophenoloxidase, Tumor necrosis factor receptor‐associated factor 6 (TRAF6) and Haemocyanin were found to be up‐regulated significantly in different ontogenetic development stages of shrimp fed with r‐VP28 and HIM formulated diets. Relative percent survival (RPS) was determined in shrimp fed with immunostimulants formulated diets after oral challenge with WSSV. The survival of WSSV challenged shrimp was found to be higher in immunostimulants treated groups when compared to untreated group. The results of PCR, ELISA and real time PCR revealed the absence of WSSV in WSSV‐challenged shrimp after 20 days of treatment with immunostimulants. Among these immunostimulants, HIM was found to be more effective when compared to r‐VP28. After a survey of literature, we are of the opinion that this might be the first report on the expression of immune genes during ontogenetic development of L. vannamei in response to immunostimulants. HighlightsExpression of immune related genes during ontogenetic development in shrimp.Oral application of viral and herbal immunostimulants in shrimp.Immune response of shrimp to viral protein and herbal immunostimulant.Efficacy of viral protein and herbal immunostimulant to protect shrimp from WSSV infection.

Tissue distribution of hepatopancreatic parvo‐like virus of shrimp in freshwater rice‐field crab, Paratelphusa hydrodomous (Herbst)

An attempt was made to determine the replication efficiency of hepatopancreatic parvo-like virus (HPV) of shrimp in different organs of freshwater rice-field crab Paratelphusa hydrodomous (Herbst) using bioassay, PCR, RT-PCR, ELISA, Western blot and q-PCR analyses. Another attempt was made to use this crab as an alternative to penaeid shrimp for the large-scale production of HPV. This crab was found to be highly susceptible to HPV by intramuscular injection. The systemic HPV infection was confirmed by PCR and Western blot analyses in freshwater crab. The expression of capsid protein gene in different organs of infected crab was revealed by RT-PCR analysis. Indirect ELISA was used to quantify the capsid protein in different organs of the crab. The copy number of HPV in different organs of the infected crab was quantified by q-PCR. The results revealed a steady decrease in CT values in different organs of the infected crab during the course of infection. The viral inoculum that was prepared from different organs of the infected crab caused significant mortality in post-larvae of tiger prawn, Penaeus monodon (Fabricius). The results revealed that this rice-field crab could be used as an alternative host for HPV replication and also for large-scale production of HPV.

Antiviral viral compound from Streptomyces ghanaensis like strain against white spot syndrome virus (WSSV) of shrimp

Actinomycetes isolates collected from different environments were screened for antiviral activity against WSSV. One isolate designated as CAHSH-2 showed antiviral activity against WSSV at the concentration of 0.2 mg per shrimp. The laboratory trial of determining antiviral activity of ethyl acetate extract (EtOAcE) of CAHSH-2 against WSSV was carried out 21 times since 2014. CAHSH-2 isolate which showed antiviral activity was characterized and identified as Streptomyces ghanaensis like strain. Among the five fractions obtained from EtOAcE of potential actinomycetes isolate, F1 was found to have strong antiviral activity. The F1A and F1B sub-fractions from F1 fraction were subjected to GC-MS, FTIR, 1H and 13C NMR analyses and, the compounds identified were di-n-octyl phthalate and bis (2-methylheptyl) phthalate, respectively. Among these compounds, di-n-octyl phthalate showed strong antiviral activity against WSSV. Molecular docking studies revealed that di-n-octyl phthalate was found to have high binding affinity with VP26 and VP28 proteins of WSSV, whereas the bis (2-methylheptyl) phthalate showed low binding affinity with VP26 and VP28. The antiviral activity of EtOAcE of actinomycetes against WSSV was confirmed by PCR, RT-PCR, Western blot and ELISA. The EA extract of active isolate was found to be non-toxic to Artemia, post-larvae and adult Litopenaeus vannamei. Importance White spot syndrome virus (WSSV) is an important shrimp viral pathogen and responsible for huge economic loss to shrimp culture industry worldwide including India. The global loss due to WSSV has been estimated about USD 10 billion and the loss continues at the same extent even now. Various strategies have been followed to prevent or control diseases of aquatic animals. In spite of various preventive and control strategies, WSSV has been still persisting for more than two decades. No control strategies have so far been evolved to put a break to WSSV. In this situation, an attempt was made in the present work to screen some actinomycetes isolates for antiviral activity against WSSV. Among these isolates, one isolate identified as Streptomyces ghanaensis like isolate CAHSH-2 showed activity against WSSV. This article gives the information about the antiviral compound against WSSV and the mechanism of viral inhibition.

Retraction notice to “Chitosan tripolyphosphate (CS/TPP) nanoparticles: Preparation, characterization and application for gene delivery in shrimp” [Acta Tropica (2013) 486–493]

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This paper has been retracted at the request of the Editor due to very significant similarity between it and two other published articles nd the suspected duplication of data. Below are the two articles: 1. Vimal et al., Aquacuture 358–359, 14–22, 2012: http://www.sciencedirect.com/science/article/pii/S0044848612003651. 2. Venkatesan et al., J Biochem Molecular Toxicology 27: 406–411, 2013 http://onlinelibrary.wiley.com/doi/10.1002/jbt.21502/full.