Purification of white spot syndrome virus by iodixanol density gradient centrifugation

Experimental Infection Models and Their Usefulness for White Spot Syndrome Virus (WSSV) Research in Shrimp

White spot syndrome virus (WSSV) is marked as one of the most economically devastating pathogens in shrimp aquaculture worldwide. Infection of cultured shrimp can lead to mass mortality (up to 100%). Although progress has been made, our understanding of WSSV's infection process and the virus-host-environment interaction is far from complete. This in turn hinders the development of effective mitigation strategies against WSSV. Infection models occupy a crucial first step in the research flow that tries to elucidate the infectious disease process to develop new antiviral treatments. Moreover, since the establishment of continuous shrimp cell lines is a work in progress, the development and use of standardized in vivo infection models that reflect the host-pathogen interaction in shrimp is a necessity. This review critically examines key aspects of in vivo WSSV infection model development that are often overlooked, such as standardization, (post)larval quality, inoculum type and choice of inoculation procedure, housing conditions, and shrimp welfare considerations. Furthermore, the usefulness of experimental infection models for different lines of WSSV research will be discussed with the aim to aid researchers when choosing a suitable model for their research needs.

Recent Advances in Nanoparticle Concentration and Their Application in Viral Detection Using Integrated Sensors

Early disease diagnostics require rapid, sensitive, and selective detection methods for target analytes. Specifically, early viral detection in a point-of-care setting is critical in preventing epidemics and the spread of disease. However, conventional methods such as enzyme-linked immunosorbent assays or cell cultures are cumbersome and difficult for field use due to the requirements of extensive lab equipment and highly trained personnel, as well as limited sensitivity. Recent advances in nanoparticle concentration have given rise to many novel detection methodologies, which address the shortcomings in modern clinical assays. Here, we review the primary, well-characterized methods for nanoparticle concentration in the context of viral detection via diffusion, centrifugation and microfiltration, electric and magnetic fields, and nano-microfluidics. Details of the concentration mechanisms and examples of related applications provide valuable information to design portable, integrated sensors. This study reviews a wide range of concentration techniques and compares their advantages and disadvantages with respect to viral particle detection. We conclude by highlighting selected concentration methods and devices for next-generation biosensing systems.

Kinetic analysis of internalization of white spot syndrome virus by haemocyte subpopulations of penaeid shrimp, Litopenaeus vannamei (Boone), and the outcome for virus and cell

Little is known about the innate antiviral defence of shrimp haemocytes. In this context, the haemocytes of penaeid shrimp Litopenaeus vannamei (Boone) were separated by iodixanol density gradient centrifugation into five subpopulations (sub): sub 1 (hyalinocytes), sub 2 and 3 (prohyalinocytes), sub 4 (semigranulocytes) and sub 5 (granulocytes) and exposed to beads, white spot syndrome virus (WSSV) and ultraviolet (UV)-killed WSSV. In a first experiment, the uptake of beads, white spot syndrome virus (WSSV) and UV-killed WSSV by these different haemocyte subpopulations was investigated using confocal microscopy. Only haemocytes of sub 1, 4 and 5 were internalizing beads, WSSV and UV-killed WSSV. Beads were engulfed by a much larger percentage of cells (91.2 in sub 1; 84.1 in sub 4 and 58.1 in sub 5) compared to WSSV (9.6 in sub 1; 10.5 in sub 4 and 7.9 in sub 5) and UV-killed WSSV (12.9 in sub 1; 13.3 in sub 4; and 11.8 in sub 5). In a second experiment, it was shown that upon internalization, WSS virions lost their envelope most probably by fusion with the cellular membrane of the endosome (starting between 30 and 60 min post-inoculation) and that afterwards the capsid started to become disintegrated (from 360 min post-inoculation). Expression of new viral proteins was not observed. Incubation of haemocyte subpopulations with WSSV but not with UV-killed WSSV and polystyrene beads resulted in a significant drop in haemocyte viability. To find the underlying mechanism, a third experiment was performed in which haemocyte subpopulations were exposed to a short WSSV DNA fragment (VP19) and CpG ODNs. These small DNA fragments induced cell death. In conclusion, WSSV is efficiently internalized by hyalinocytes, semigranulocytes and granulocytes, after which the virus loses its envelope; as soon as the capsids start to disintegrate, cell death is activated, which in part may be explained by the exposure of viral DNA to cellular-sensing molecules.

Identification and involvement of ferritin in the response to pathogen challenge in the abalone, Haliotis diversicolor

Accumulating data has demonstrated that ferritin plays an important role in host defense responses against infection by pathogens in many organisms. In this study, ultracentrifugation was used to isolate ferritin from abalone, Haliotis diversicolor, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed that this ferritin consisted of two subunits (designated as HdFer1 and HdFer2). There are no disulfide bonds between the HdFer1 and HdFer2 subunits; however, these subunits co-assemble to form heteropolymers. A novel ferritin subunit (HdFer2) was cloned from H. diversicolor by 5' and 3' RACE (rapid amplification of cDNA ends) approach. The full-length HdFer2 cDNA sequence consists of 878 bp with an open reading frame of 513 bp that encodes a protein that is 170 amino acids in length. Quantitative real-time PCR analysis revealed that HdFer1 and HdFer2 were transcribed in various tissues, such as the mantle, gill and hepatopancreas, with the highest levels of expression in the hepatopancreas. Following a challenge with the pathogen, Vibrio harveyi, the expression of HdFer1 and HdFer2 were markedly induced at different times. This study has identified a novel ferritin subunit in H. diversicolor which will contribute to further exploration of the role of ferritin in mollusk innate immune defense against invading pathogens.