Efficacy of an infectious hematopoietic necrosis (IHN) virus DNA vaccine in Chinook Oncorhynchus tshawytscha and sockeye O. nerka salmon

The level of protective immunity was determined for Chinook Oncorhynchus tshawytscha and sockeye/kokanee salmon (anadromous and landlocked) O. nerka following intramuscular vaccination with a DNA vaccine against the aquatic rhabdovirus, infectious hematopoietic necrosis virus (IHNV). A DNA vaccine containing the glycoprotein gene of IHNV protected Chinook and sockeye/kokanee salmon against waterborne or injection challenge with IHNV, and relative percent survival (RPS) values of 23 to 86% were obtained under a variety of lethal challenge conditions. Although this is significant protection, it is less than RPS values obtained in previous studies with rainbow trout (O. mykiss). In addition to the variability in the severity of the challenge and inherent host susceptibility differences, it appears that use of a cross-genogroup challenge virus strain may lead to reduced efficacy of the DNA vaccine. Neutralizing antibody titers were detected in both Chinook and sockeye that had been vaccinated with 1.0 and 0.1 pg doses of the DNA vaccine, and vaccinated fish responded to viral challenges with higher antibody titers than mock-vaccinated control fish.     

Altered cholesterol metabolism in Niemann-Pick type C1 mouse brains affects mitochondrial function

Niemann-Pick type C1 (NPC1) disease is a fatal hereditary disorder characterized by a defect in cholesterol trafficking and progressive neurodegeneration. Although the NPC1 gene has been identified, the molecular mechanism responsible for neuronal dysfunction in brains of patients with NPC1 disease remains unknown. This study demonstrates that the amount of cholesterol within mitochondria membranes is significantly elevated in NPC1 mouse brains and neural cells. In addition, the mitochondrial membrane potential, the activity of ATP synthase, and henceforth the level of ATP are markedly decreased in NPC1 mouse brains and neurons. Importantly, reducing the level of cholesterol within mitochondrial membranes using methyl-beta-cyclodextrin can restore the activity of ATP synthase. Finally, NPC1 neurons show an impaired neurite outgrowth, which can be rescued by exogenous ATP. These results suggest that mitochondrial dysfunctions and subsequent ATP deficiency, which are induced by altered cholesterol metabolism in mitochondria, may be responsible for neuronal impairment in NPC1 disease.     

A single-molecule method for the quantitation of microRNA gene expression

MicroRNAs (miRNA) are short endogenous noncoding RNA molecules that regulate fundamental cellular processes such as cell differentiation, cell proliferation and apoptosis through modulation of gene expression. Critical to understanding the role of miRNAs in this regulation is a method to rapidly and accurately quantitate miRNA gene expression. Existing methods lack sensitivity, specificity and typically require upfront enrichment, ligation and/or amplification steps. The Direct miRNA assay hybridizes two spectrally distinguishable fluorescent locked nucleic acid (LNA)-DNA oligonucleotide probes to the miRNA of interest, and then tagged molecules are directly counted on a single-molecule detection instrument. In this study, we show the assay is sensitive to femtomolar concentrations of miRNA (500 fM), has a three-log linear dynamic range and is capable of distinguishing among miRNA family members. Using this technology, we quantified expression of 45 human miRNAs within 16 different tissues, yielding a quantitative differential expression profile that correlates and expands upon published results.     

Estimation of Parameters Influencing Waterborne Transmission of Infectious Hematopoietic Necrosis Virus (IHNV) in Atlantic Salmon (Salmo salar)

Understanding how pathogenic organisms spread in the environment is crucial for the management of disease, yet knowledge of propagule dispersal and transmission in aquatic environments is limited. We conducted empirical studies using the aquatic virus, infectious hematopoietic necrosis virus (IHNV), to quantify infectious dose, shedding capacity, and virus destruction rates in order to better understand the transmission of IHN virus among Atlantic salmon marine net-pen aquaculture. Transmission of virus and subsequent mortality in Atlantic salmon post-smolts was initiated with as low as 10 plaque forming units (pfu) ml⁻¹. Virus shedding from IHNV infected Atlantic salmon was detected before the onset of visible signs of disease with peak shed rates averaging 3.2×10⁷ pfu fish⁻¹ hour⁻¹ one to two days prior to mortality. Once shed into the marine environment, the abundance of free IHNV is modulated by sunlight (UV A and B) and the growth of natural biota present in the seawater. Virus decayed very slowly in sterilized seawater while rates as high as k =  4.37 d⁻¹ were observed in natural seawater. Decay rates were further accelerated when exposed to sunlight with virus infectivity reduced by six orders of magnitude within 3 hours of full sunlight exposure. Coupling the IHNV transmission parameter estimates determined here with physical water circulation models, will increase the understanding of IHNV dispersal and provide accurate geospatial predictions of risk for IHNV transmission from marine salmon sites.