Flavivirus Infection and Regulation of Host Immune and Tissue Homeostasis in Insects

The isolation and identification of a novel flavivirus from diseased Chinese soft-shelled turtle (Pelodiscussinensis)

In recent years, mass mortality of Pelodiscus sinensis has occurred in many Chinese turtle farms and no etiological research on this disease has been conducted to date. The main clinical manifestation of sick P. sinensis was telangiectasis induced bleeding occurred in the limbs, calipash and plastron. After dissection, we found that the blood viscosity was reduced. Typical clinical manifestations included light abdominal cavity effusion, intestine and gastric wall edema and transparency. HE staining showed distinct lesions in liver, intestine, kidney, spleen, heart and lung tissues of infected P. sinensis. TEM observation showed that the spherical virions were approximately 30 nm in diameter. Partial genome of the pathogen was obtained by Illumina sequencing and then assembled and annotated. Phylogenetic analysis of the polyprotein amino acid sequences of this pathogen and other flaviviruses showed that it was closely related to Chinese soft-shelled turtle flavivirus isolate HZ-2017. RT-PCR detection of this virus in the sick P. sinensis from turtle farms showed a high infection rate. QRT-PCR analysis of viral distribution in P. sinensis tissues indicated that the kidney contains the highest amount of virus. The virus was tentatively named "Pelodiscus sinensis flavivirus" (PSFV). In this study, the results of PSFV pathological characteristic and genome information laid a good foundation for further study of this virus.

Immune Reactions of Vector Insects to Parasites and Pathogens

This overview initially describes insect immune reactions and then brings together present knowledge of the interactions of vector insects with their invading parasites and pathogens. It is a way of introducing this Special Issue with subsequent papers presenting the latest details of these interactions in each particular group of vectors. Hopefully, this paper will fill a void in the literature since brief descriptions of vector immunity have now been brought together in one publication and could form a starting point for those interested and new to this important area. Descriptions are given on the immune reactions of mosquitoes, blackflies, sandflies, tsetse flies, lice, fleas and triatomine bugs. Cellular and humoral defences are described separately but emphasis is made on the co-operation of these processes in the completed immune response. The paper also emphasises the need for great care in extracting haemocytes for subsequent study as appreciation of their fragile nature is often overlooked with the non-sterile media, smearing techniques and excessive centrifugation sometimes used. The potential vital role of eicosanoids in the instigation of many of the immune reactions described is also discussed. Finally, the priming of the immune system, mainly in mosquitoes, is considered and one possible mechanism is presented.

Interactions of host miRNAs in the flavivirus 3´UTR genome: From bioinformatics predictions to practical approaches

The genus Flavivirus of the Flaviviridae family includes important viruses, such as Dengue, Zika, West Nile, Japanese encephalitis, Murray Valley encephalitis, tick-borne encephalitis, Yellow fever, Saint Louis encephalitis, and Usutu viruses. They are transmitted by mosquitoes or ticks, and they can infect humans, causing fever, encephalitis, or haemorrhagic fever. The treatment resources for these diseases and the number of vaccines available are limited. It has been discovered that eukaryotic cells synthesize small RNA molecules that can bind specifically to sequences present in messenger RNAs to inhibit the translation process, thus regulating gene expression. These small RNAs have been named microRNAs, and they have an important impact on viral infections. In this review, we compiled the available information on miRNAs that can interact with the 3’ untranslated region (3’UTR) of the flavivirus genome, a conserved region that is important for viral replication and translation.