Antibacterial activity of a short de novo designed peptide against fish bacterial pathogens.

In the face of increasing antimicrobial resistance in aquaculture, researchers are exploring novel substitutes to customary antibiotics. One potential solution is the use of antimicrobial peptides (AMPs). We aimed to design and evaluate a novel, short, and compositionally simple AMP with potent activity against various bacterial pathogens in aquaculture. The resulting peptide, KK12YW, has an amphipathic nature and net charge of + 7. Molecular docking experiments disclosed that KK12YW has a strong affinity for aerolysin, a virulence protein produced by the bacterial pathogen Aeromonas sobria. KK12YW was synthesized using Fmoc chemistry and tested against a range of bacterial pathogens, including A. sobria, A. salmonicida, A. hydrophila, Edwardsiella tarda, Vibrio parahaemolyticus, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, and methicillin-resistant S. aureus. The AMP showed promising antibacterial activity, with MIC and MBC values ranging from 0.89 to 917.1 µgmL-1 and 3.67 to 1100.52 µgmL-1, respectively. In addition, KK12YW exhibited resistance to high temperatures and remained effective even in the presence of serum and salt, indicating its stability. The peptide also demonstrated minimal hemolysis toward fish RBCs, even at higher concentrations. Taken together, these findings indicate that KK12YW could be a highly promising and viable substitute for conventional antibiotics to combat microbial infections in aquaculture.

A cell line derived from heart of rainbow trout is refractory to Tilapia lake virus.

Cell lines are important in vitro models to answer biological mechanisms with less genetic variations. The present study was attempted to develop a cell line from rainbow trout, where we obtained a cell line from the heart, named "RBT-H." The cell line was authenticated using karyotyping and cytochrome c oxidase subunit I (COI) gene sequencing. The karyotype demonstrated diploid chromosome number (2n) as 62 and the sequence of partial COI gene was 99.84% similar to rainbow trout COI data set, both suggesting the origin of RBT-H from the rainbow trout. The heart cell line was mycoplasma-free and found to be refractory to infection with the Tilapia lake virus. The RBT-H cell line is deposited in the National Repository of Fish Cell Line (NRFC) at ICAR-NBFGR, Lucknow, India, with Accession no. NRFC0075 for maintenance and distribution to researchers on request for R&D.

First report of Achlya bisexualis infection in captive-reared Endangered golden mahseer Tor putitora.

Achlya bisexualis is a notorious oomycete pathogen with the potential to cause emerging disease in fish farms. In this study, we report the first isolation of A. bisexualis from captive-reared golden mahseer Tor putitora, an Endangered fish species. The infected fish showed a cotton-like growth of mycelia at the site of infection. The mycelium when cultured on potato dextrose agar produced radially growing white hyphae. The hyphae were non-septate, and some of them carried matured zoosporangium with dense granular cytoplasmic contents. Spherical gemmae with stout stalks were also observed. All the isolates had 100% identity in internal transcribed spacer (ITS)-rDNA sequence and showed highest similarity to that of A. bisexualis. In molecular phylogeny, all the isolates formed a monophyletic group with A. bisexualis which was supported by a bootstrap value of 99%. Based on the molecular and morphological findings, all the isolates were confirmed as A. bisexualis. Further, the anti-oomycete effect of boric acid, a known antifungal agent, against the isolate was evaluated. The minimum inhibitory concentration and minimum fungicidal concentration were found to be 1.25 and >2.5 g l-1, respectively. Isolation of A. bisexualis from a new fish species indicates its possible occurrence in other unreported hosts. Considering its wide infectivity and the potential to cause disease in farmed fishes, its probable prevalence in a new environment and host needs to be closely monitored to prevent the spread of infection, if any, by adopting suitable control measures.

Identification and characterization of phage display-selected peptides having affinity to Peste des petits ruminants virus.

Phage display is a well-established technique used for selecting novel ligands having affinity to a plethora of targets including proteins, viruses, whole bacterial and mammalian cells as well as lipid targets. In the present study, phage display technology was used to identify peptides having affinity to PPRV. The binding capacity of these peptides was characterized through various formats of ELISA using phage clones, linear and multiple antigenic peptides. The whole PPRV was used as an immobilized target in a surface biopanning process using a 12-mer phage display random peptide library. After five rounds of biopanning, forty colonies were picked and amplified followed by DNA isolation and amplification for sequencing. Sequencing suggested 12 different clones expressing different peptide sequence Phage-ELISA was performed using all 12 phage clones. Results indicated that four phage clones i.e., P4, P8, P9 and P12 had a specific binding activity to PPR virus. Linear peptides displayed by all 12 clones were synthesized using solid phase peptide synthesis and subjected to virus capture ELISA. No significant binding of the linear peptides with PPRV was evident which may be due to loss of conformation of linear peptide after coating. When the four selected phage clones displayed peptide sequences were synthesized in Multiple antigenic peptide (MAP) format and used in virus capture ELISA, the results indicated significant binding of PPRV to the MAPs. It may be due to increased avidity and/or better projection of binding residues in 4-armed MAPs as compared to linear peptides. MAP-peptides were also conjugated on gold nanoparticles (AuNPs). Visual colour change from wine red to purple was observed on addition of PPRV in MAP-conjugated AuNPs solution. This colour change may be attributable to the networking of PPRV with MAP -conjugated AuNPs resulting in aggregation of AuNPs. All these results supported the hypothesis that the phage display selected peptides were capable of binding to the PPRV. The potential of these peptides to develop novel diagnostic or therapeutic agents remains to be investigated.

Establishment and characterization of a new fibroblast-like cell line from the skin of a vertebrate model, zebrafish (Danio rerio).

BACKGROUND: The available fully sequenced genome and genetic similarities compared to humans make zebrafish a prominent in vitro vertebrate model for drug discovery & screening, toxicology, and radiation biology. Zebrafish also possess well developed immune systems which is ideal for studying infectious diseases. Fish skin confers immunity by serving as a physical barrier against the invading pathogens in the aquatic habitat. Therefore in vitro models from the skin tissue of zebrafish help to study the physiology, functional genes in vitro, wound healing, and pathogenicity of microbes. Hence the study aimed to develop and characterize a skin cell line from the wild-type zebrafish Danio rerio. METHODS AND RESULTS: A novel cell line designated as DRS (D. rerio skin) was established and characterized from the skin tissue of wild-type zebrafish, D. rerio, by the explant technique. The cells thrived well in the Leibovitz's -15 medium supplemented with 15% FBS and routinely passaged at regular intervals. The DRS cells mainly feature fibroblast-like morphology. The culture conditions of the cells were determined by incubating the cells at varying concentrations of FBS and temperature; the optimum was 15% FBS and 28 °C, respectively. Cells were cryopreserved and revived with 70-75% viability at different passage levels. Two extracellular products from bacterial species Aeromonas hydrophila and Edwardsiella tarda were tested and found toxic to the DRS cells. Mitochondrial genes, namely COI and 16S rRNA PCR amplification and partial sequencing authenticated the species of origin of cells. The modal diploid (2n) chromosome number of the cells was 50. The cell line DRS was found to be free from mycoplasma. The cells were transfected with pMaxGFP plasmid and tested positive for green fluorescence at 24-48 h post-transfection. CONCLUSION: The findings from this study thus confirm the usefulness of the developed cell line in bacterial susceptibility and transgene expression studies.

Development of multiplex PCR assay for species-specific detection and identification of Saprolegnia parasitica.

Saprolegnia parasitica is the most important pathogen under the genus, Saprolegnia which causes devastating oomycete diseases in freshwater fish. At present, the most common molecular method for identification of Saprolegnia species is sequencing of ribosomal DNA internal transcribed spacer (rDNA-ITS) region. In this study, a highly sensitive multiplex PCR targeting rDNA-ITS region and a hypothetical protein gene was developed using two sets of primer pair. In this PCR, two amplicons of different size of 750 bp and 365 bp are produced only in case of S. parasitica while other Saprolegnia species had single amplicon. This protocol could also differentiate Saprolegnia species from other fungus based on the size of rDNA-ITS region. The protocol does not require sequencing and can identify S. parasitica in a single reaction. Therefore, the multiplex PCR developed in this study may prove to be an easier, faster and cheaper molecular method for identification of S. parasitica.

Tools and techniques for rational designing of antimicrobial peptides for aquaculture.

Fisheries and aquaculture industries remain essential sources of food and nutrition for millions of people worldwide. Indiscriminate use of antibiotics has led to the emergence of antimicrobial-resistant bacteria and posed a severe threat to public health. Researchers have opined that antimicrobial peptides (AMPs) can be the best possible alternative to curb the rising tide of antimicrobial resistance in aquaculture. AMPs may also help to achieve the objectives of one health approach. The natural AMPs are associated with several shortcomings, like less in vivo stability, toxicity to host cell, high cost of production and low potency in a biological system. In this review, we have provided a comprehensive outline about the strategies for designing synthetic mimics of natural AMPs with high potency. Moreover, the freely available AMP databases and the information about the molecular docking tools are enlisted. We also provided in silico template for rationally designing the AMPs from fish piscidins or other peptides. The rationally designed piscidin (rP1 and rp2) may be used to tackle microbial infections in aquaculture. Further, the protocol can be used to develop the truncated mimics of natural AMPs having more potency and protease stability.

Anti-oomycete Activity of Chlorhexidine Gluconate: Molecular Docking and in vitro Studies.

Saprolegniosis is one of the most catastrophic oomycete diseases of freshwater fish caused by the members of the genus Saprolegnia. The disease is responsible for huge economic losses in the aquaculture industry worldwide. Until 2002, Saprolegnia infections were effectively controlled by using malachite green. However, the drug has been banned for use in aquaculture due to its harmful effect. Therefore, it has become important to find an alternate and safe anti-oomycete agent that is effective against Saprolegnia. In this study, we investigated the anti-oomycete activity of chlorhexidine gluconate (CHG) against Saprolegnia. Before in vitro evaluation, molecular docking was carried out to explore the binding of CHG with vital proteins of Saprolegnia, such as S. parasitica host-targeting protein 1 (SpHtp1), plasma membrane ATPase, and TKL protein kinase. In silico studies revealed that CHG binds with these proteins via hydrogen bonds and hydrophobic interactions. In an in vitro study, the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of CHG against S. parasitica were found to be 50 mg/L. Further, it was tested against S. australis, another species of Saprolegnia, and the MIC and MFC were found to be 100 and 200 mg/L, respectively. At 500 mg/L of CHG, there was complete inhibition of the radial growth of Saprolegnia hyphae. In propidium iodide (PI) uptake assay, CHG treated hyphae had bright red fluorescence of PI indicating the disruption of the cell membrane. The results of the present study indicated that CHG could effectively inhibit Saprolegnia and hence can be used for controlling Saprolegniasis in cultured fish.

Antimicrobial activity of an artificially designed peptide against fish pathogens.

Antimicrobial peptides (AMPs) are considered alternatives to classical antibiotics and may become an excellent candidate for tackling antimicrobial resistance in aquaculture. Designing novel antimicrobial peptides for curbing antimicrobial resistance in aquaculture is paramount in one health approach. In this study, a short and compositionally simple peptide, KK16, was designed. KK16 is amphipathic with a net charge of + 6. Molecular docking results revealed that KK16 has a strong affinity towards two virulence proteins of Aeromonas sobria; aerolysin and outer membrane protein (omp). The peptide was synthesised using Fmoc-chemistry, and its antimicrobial efficacy was evaluated in vitro against A.sobria, A. salmonicida, Edwardsiella tarda, A. hydrophila, Vibrio parahaemolyticus, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis and methicillin-resistant S. aureus. The KK16 AMP showed potent activity against the tested bacterial pathogens as revealed by the MIC and MBC, ranging from 7.81 to 500 µM, and 15-900 µM, respectively. Moreover, the peptide was stable at higher temperatures and retained its activity in presence of serum and salt. The peptide displayed less haemolytic and cytotoxic activity even at higher concentrations. In peptide-DNA binding assay, KK16 showed its binding potential with bacterial genomic DNA and thus, may interfere with replication. Fluorescent microscopy revealed the uptake of propidium iodide by peptide treated bacterial cells, indicating its membrane disruption activity. In in vivo experiment, KK16 peptide completely inhibited the growth of Saprolegnia parasitica fungus at ≥ 30 µM peptide concentrations in embryonated fish eggs. The results indicate that KK16 peptide is stable, possess potent antibacterial and antifungal activity, less cytotoxic to host cells, and hence may prove to be a promising anti-infective agent for combating common bacterial and fungal infections.

Dietary lutein supplementation improves immunity and antioxidant status of captive Indian leopards (Panthera fusca).

Indian leopards kept in zoos are fed solely on carabeef on bone (CBB) diets. Carabeef contains lesser or no carotenoids. Hence, the captive Indian leopard diets are suspected to be deficient in carotenoids while their wild counterparts acquire these pigments from their natural prey. Lutein is a vital carotenoid that plays its role as an antioxidant and immunomodulator. This experiment investigates the effect of lutein supplementation on antioxidant status, immunity, and stress in captive Panthera fusca fed CBB diets. Nine leopards were used based on 3 × 3 replicated Latin square designs in the experiment. Groups CON, LUT20, and LUT40 were supplemented with 0, 20, and 40 ppm of lutein, respectively. Each experiment comprised of 10 days of wash-out period, 11 days of adaptation, and 4 days of collection. Digestibility of crude protein (CP) was higher (p < .01) in groups LUT20 and LUT40. Serum concentration of protein, globulin, urea (p < .05), total carotenoids, total antioxidant capacity (TAC), catalase (CAT) activity, and lymphocyte transformation test (LTT) index were higher (p < .001) in groups LUT20 and LUT40. Activity of superoxide dismutase (SOD) and serum concentration of immunoglobulin were higher (p < .001) in group LUT20. Serum concentration of malonaldehyde (MDA) and fecal concentration of cortisol decreased (p < .001) in groups LUT20 and LUT40. Serum concentration of total immunoglobulin (µg/ml) and LTT were higher in group LUT20. Fecal concentration of cortisol (ng/g) was lower in LUT20 and LUT40. The study concludes that supplementation of lutein at 20 ppm would improve antioxidant status and immunity and alleviate stress in captive Indian leopards.

Lethal dose and histopathological alterations induced by Aeromonas salmonicida in experimentally challenged common carp, Cyprinus carpio.

Aeromonas salmonicida is the obligate pathogen of fishes having zoonotic potential. It is reported to cause considerable losses in world aquaculture. The current study has successfully demonstrated the induction of histopathological lesions in experimentally infected common carp. In the current study, the lethal concentration (LD50-96 h) of typical A. Salmonicida for common carp was found to be 1.5 × 107CFU mL-1. About 40% and 60% fish mortalities occurred after 72 h in the groups inoculated with 107 and 108 CFU mL-1 bacterial suspension, respectively. The fish challenged with A. salmonicida showed symptoms like abnormal swimming behaviour, lethargy, intra-abdominal fluid, haemorrhages on the ventral side of the body, vent and fins. The signs proceeded with the death of fish. In the histological sections, severe pathological alterations were reported in the tissue sections of internal organs. The microscopic observation showed sinusoidal and large blood vessel congestion in the liver, profuse haemorrhage, necrosis and infiltration of blood cells in the internal organs. The tubular architecture was lost with the infiltration of leucocytes in the kidney. In gills, more intense and prominent lamellar fusion was observed with leucocytic infiltration, telangiectasia and hyperplasia of lamellar epithelial cells. In summary, we have experimentally induced the typical A. salmonicida infection in common carp. The study will provide a research foundation for further studies on the host-pathogen interaction, therapeutics and epidemiology of A. salmonicida.

Anti-oomycetes and immunostimulatory activity of natural plant extract compounds against Saprolegnia spp.: Molecular docking and in-vitro studies.

This study aimed to investigate the effectiveness of five natural plant extract compounds Curcumin (CUR); Eugenol (EUG), Cinnamaldehyde (CIN), Stigmasterol (ST) and Morin (MOR), on two species of Saprolegnia; Saprolegnia parasitica and S. australis. Selective compounds were screened for the minimum inhibitory concentration, first for anti-oomycetes activity and then mycelium growth inhibition, spore germination inhibition and colonisation test. Nitric oxide production and myeloperoxidase activity of the compounds were tested in head kidney leukocytes of rainbow trout, Oncorhynchus mykiss to assess the immunostimulatory potential. Molecular docking of effective compounds was carried out with effector proteins of S. parasitica to investigate the target binding sites. Among all, CUR could completely inhibit zoospore production and significantly (p ≤ .05) inhibit hyphal growth at 16 mg l-1 against S. parasitica and S. australis. CIN at the concentration of 50 mg l-1 completely inhibited hyphal growth of both Saprolegnia spp., although the zoospore production of S. parasitica and S. australis was reduced at 25 mg l-1 and 10 mg l-1. In the case of EUG, significant inhibition of the hyphal growth and germination of S. parasitica zoospores was observed at 50 mg l-1. ST and MOR did not show antioomycetes activity. The molecular docking results were consistent with in vitro studies, possibly due to the binding with the vital proteins (Plasma membrane ATPase, V-type proton ATPase, TKL protein kinase, Host targeting protein 1) of S. parasitica and ultimately inhibiting their activity. CUR and CIN showed increased nitric oxide production at the highest concentration of 250 and 256 mg l-1 but the value was not significant (p ≤ .05) with control. CUR showed significantly higher peroxidase activity (p ≤ .05) at a concentration of 256 mg l-1 though values were significantly similar with concentration from 16 to 128 mg l-1. The nitric oxide and total peroxidase activity of rainbow trout leukocytes in the case of CIN showed a significant difference only at 250 mg l-1 against the control. The results conclude that CUR, CIN showed the better anti-Saprolegnia activity and could be used as phyto-additives in aquaculture. Among all, the inclusion of CUR as phyto-additives will provide additional immunostimulatory activity.

Antibacterial and antioomycete activities of a novel designed RY12WY peptide against fish pathogens.

In the present study, we have designed and synthesized a short compositionally simple peptide RY12WY having potent antimicrobial activity. The molecular docking study results showed that peptide has a strong affinity towards two protein targets of A. sobria; aerolysin and outer membrane protein (OMP). The MIC values ranged from 0.98 to 500 µM and MBC values ranged from 4 to 650 µM against the selected bacterial and fungal pathogens. The intense antimicrobial activity of RY12WY is reported against A. sobria, A. hydrophila, E. tarda, S. aureus, V. parahaemolyticus, P. aeruginosa and E.coli at low concentration.The peptide also showed good activity against A. salmonicida and S. parasitica zoospores. The peptide retained its antimicrobial activity at higher temperatures. Besides, it was active in the presence of physiological salts and serum.The peptide showed negligible haemolytic activity at 125 µM and HC50 was found to be 1437.10 µM. The DNA binding assay indicated that peptide can bind with the genetic material of the bacteria and may inhibit its replication. The bacterial viability assay reported that the peptide interferes with bacterial membrane integrity. To conclude, the results suggest that RY12WY could be a promising therapeutic agent in aquaculture and has possible application in food processing industry which warrants higher temperatures.

Characterization of a new cell line from ornamental fish Amphiprion ocellaris (Cuvier, 1830) and its susceptibility to nervous necrosis virus.

Amphiprion ocellaris (ocellaris clownfish) is one of the most commercially important marine ornamental fish. A cell line designated as OCF was developed for the first time from the caudal fin of this fish species. The cell line was maintained in Leibovitz's-15 medium supplemented with 15% FBS (Fetal Bovine Serum) and was successfully subcultured up to 34 passages. The cell line was authenticated by sequencing mitochondrial cytochrome C oxidase subunit I (COI) and 16S rRNA genes. The growth rate of the OCF cell line was maximum in medium containing 20% FBS and 1% of 0.2 M NaCl at 28 °C. Chromosome analysis revealed 48 diploid chromosomes. The OCF cell line was transfected with the pMaxGFP plasmid vector with 7% efficiency and GFP expression was observed. The OCF cell line was used for testing nervous necrosis virus (NNV) susceptibility. Cytopathic effect (CPE) was observed in terms of plaque formation after virus inoculation. Nested PCR confirmed the susceptibility of the OCF cell line to NNV. The cell line was successfully cryopreserved by a slow freezing procedure at - 80 °C with a revival efficiency of 70-75%. The study revealed that the OCF cell line would be useful for virological studies. In addition, the cell line would play an important role as an in vitro tool for carrying out toxicological and biotechnological studies.

Antimicrobial peptides of buffalo and their role in host defenses.

Antimicrobial peptides (AMPs) are highly conserved components of the innate immune system found among all classes of life. Buffalo (Bubalus bubalis), an important livestock for milk and meat production, is known to have a better resistance to many diseases as compared to cattle. They are found to express many AMPs such as defensins, cathelicidins, and hepcidin which play an important role in neutralizing the invading pathogens. Buffalo AMPs exhibit broad-spectrum antimicrobial activity against both Gram-positive and Gram-negative bacteria. Similar to its natural form, synthetic analogs of buffalo AMPs are also antimicrobial against bacteria and even fungus making them a good target for the development of therapeutic antimicrobials. In addition to its antimicrobial effect, AMPs have been demonstrated to have a number of immunomodulatory functions, and their genes are responsive to infections. Further, induction of their gene expression by external factors may help in preventing infectious diseases. This review briefly discusses the AMPs of buffalo identified to date and their possible role in innate immunity.

Conformational analysis of a synthetic fish kisspeptin 1 peptide in membrane mimicking environments.

Kisspeptin 1 is a neuropeptide hormone of the RFamide family, which act as an upstream regulator of brain-pituitary-gonad (BPG) axis in most vertebrates including teleosts. In the present study, a 16 amino acid long putative mature bioactive peptide (kiss 1) from preprokisspeptin 1 of golden mahseer, Tor putitora (Hamilton, 1822), was synthesized and characterized using an integrated (experimental and in silico) approach. The far-UV circular dichroism (CD) spectrum of this peptide was evaluated both in aqueous and membrane mimicking solvents (TFE, HFIP and Dioxane). The results indicate that kiss 1 peptide adopted helical, turn and ß conformations in membrane like environments. The near-UV CD spectroscopy was also carried out to examine the tertiary packing around aromatic residues of kiss 1 peptide and the peptide-membrane complex. The kiss 1 peptide exhibited little signal in water, but a prominent negative band was observed at around 275 nm when membrane mimetic solution was added. The observed ordered conformations of kiss 1 peptide in the different solvents indicated its potential biological activity which could enhance the secretion of gonadotropin-releasing hormone (GnRH) at BPG axis. The conformational information generated from the present study reinforces the application prospects of bioactive synthetic peptide analogs of kisspeptin 1 in improving the reproductive performances of important cultivable fish species.

Nicotinic acetylcholine receptor alpha 1(nAChRα1) subunit peptides as potential antiviral agents against rabies virus.

Rabies virus (RABV) is neurotropic and infects all warm-blooded animals. The binding of the virus with host cell receptor components is critical for infection. The present study reports the interaction of nicotinic acetylcholine receptor alpha 1 (nAChRα1) peptides with the rabies virus glycoprotein (RABVG) to design potential anti-rabies agents. The nAChRα1peptide sequences from different species (bovine, human and electric fish/torpedo) were synthesized and their secondary structures were characterized using CD spectroscopy. The molecular docking analysis of nAChRα1 peptides with RABVG indicated the involvement of specific domains and their particular amino acid contributions. Bovine peptide (C-32) (docking score of 14146kJ/mol) and torpedo peptide (T-32) (docking score of 13704kJ/mol) were found to interact strongly with RABVG. T-32 peptides had the highest binding and inhibiting property against RABV compared to other peptide sequences. The results of both computational and experimental methods demonstrated that nAChRα1 peptides and their analogs may serve as potential antiviral agents against RABV infection.

Molecular cloning, characterization and expression profile of kisspeptin1 and kisspeptin1 receptor at brain-pituitary-gonad (BPG) axis of golden mahseer, Tor putitora (Hamilton, 1822) during gonadal development.

Complete cDNA sequences of kiss1 (gmkiss1) and its receptor kiss1r (gmkiss1r) were cloned and characterized from brain tissue of adult golden mahseer (Tor putitora). Thereafter, quantification of gmkiss1 and gmkiss1r mRNA expression in brain-pituitary-gonad (BPG) axis of male and female golden mahseer was carried out using quantitative real-time (qRT)-PCR assay during an annual reproductive cycle, at different gonadal development stages. The gmkiss1 cDNA was 508bp, with 330bp open reading frame (ORF), encoding a precursor protein of 109 amino acids, whereas gmkiss1r cDNA was 1383bp with an ORF of 1004bp, which encodes a 334 amino acid protein residue. The qRT-PCR study shows that gmkiss1 and gmkiss1r are expressed in brain, pituitary and gonads of both the sexes of golden mahseer. An apparent sexual dimorphism in transcript level of gmkiss1 and gmkiss1r in brain and gonads was evident during the reproductive cycle. Overall, in brain, testis and ovary, the gmkiss1 and gmkiss1r mRNA expression level was comparatively higher during the initial stages of gonadal development, than that of spermiation or ovulation stage. In pituitary of both the sexes, throughout the gonadal development, consistently low transcript level of gmkiss1 and gmkiss1r was observed. The gmkiss1 mRNA expression level in brain and ovary of female golden mahseer was several folds higher than the brain and testis of male fish. In conclusion, we confirm the presence of kiss1 and its receptor in golden mahseer, and results of our study strongly suggested the involvement of kisspeptin1 system in gonadal development and annual reproductive cycle of this species.

Molecular Cloning and Expression Profile of Toll-Like Receptor 3 from an Indian Coldwater Fish, Schizothorax richardsonii(Gray).

The innate immune system recognizes pathogens through pattern recognition receptors (PRRs), and toll-like receptors (TLRs) are one of the most important PRRs. TLR3 is a unique member of TLR family that recognizes double-stranded RNA (dsRNA), a viral replication intermediate. There is a variation in its response among diverse fish species toward the same stimulants. We identified and cloned TLR3 from Indian snow trout, Schizothorax richardsonii and carried out its expression analysis in un-induced and poly (I:C) challenged fish. It has an open reading frame (ORF) of 2712 bases that encodes a polypeptide of 904 amino acids. The molecular weight of the polypeptide was predicted to be 102.4482 kDa with an isoelectric point of 7.40. Quantitative real time PCR (qRT-PCR) was carried out after 24 hours of poly (I:C) treatment and expression of TLR3 was analyzed in different tissues. As compared with untreated fish the poly (I:C) challenged fish revealed significantly high expression of TLR3 in kidney followed by liver and gills.

Rapid label-free visual assay for the detection and quantification of viral RNA using peptide nucleic acid (PNA) and gold nanoparticles (AuNPs).

A rapid label-free visual assay for the detection of viral RNA using peptide nucleic acid (PNA) probes and gold nanoparticles (AuNPs) is presented in this study. Diagnosis is a crucial step for the molecular surveillance of diseases, and a rapid visual test with high specificity could play a vital role in the management of viral diseases. In this assay, the specific agglomerative behavior of PNA with gold nanoparticles was manipulated by its complementation with viral RNA. The assay was able to detect 5-10 ng of viral RNA from various biological samples, such as allantoic fluids, cell culture fluids and vaccines, in 100 µl of test solution. The developed assay was more sensitive than a hemagglutination (HA) test, a routine platform test for the detection of Newcastle disease virus (NDV), and the developed assay was able to visually detect NDV with as little as 0.25 HA units of virus. In terms of the specificity, the test could discriminate single nucleotide differences in the target RNA and hence could provide visual viral genotyping/pathotyping. This observation was confirmed by pathotyping different known isolates of NDV. Further, the PNA-induced colorimetric changes in the presence of the target RNA at different RNA to PNA ratios yielded a standard curve with a linear coefficient of R(2)=0.990, which was comparable to the value of R(2)=0.995 from real-time PCR experiments with the same viral RNA. Therefore, the viral RNA in a given samples could be quantified using a simple visual spectrophotometer available in any clinical laboratory. This assay may find application in diagnostic assays for other RNA viruses, which are well known to undergo mutations, thus presenting challenges for their molecular surveillance, genotyping and quantification.