ABSTRACT
Porcine deltacoronavirus (PDCoV) has been recently recognized as an emerging viral pathogen that causes diarrhea in newborn piglets. A total of 254 small intestinal or fecal samples collected from 10 provinces including Henan, Hunan, Zhejiang, Jiangxi, Anhui, Hebei, Heilongjiang, Jiangsu, Shandong and Shanghai between 2014 and 2015, were screened by quantitative RT-PCR targeting the viral M gene. Eleven PDCoV positive samples were identified with a total positive rate of 4.33%. An indirect enzyme-linked immunosorbent assay (ELISA) was developed based on the recombinant S1 protein of PDCoV. This assay was used to test 609 serum samples of pigs with diarrhea symptoms collected from 10 provinces between 2015 and 2016. The positive rate of PDCoV antibody was 44.17% (269/609). The two methods can be used to monitor the PDCoV epidemiology in the levels of PDCoV specific RNA or antibody, helping better prevent and control PDCoV.
ABSTRACT
The recovery of the virus from genetic materials in in vitro culture systems or sensitive animals is called virus rescue. A functional infectious clone of RNA virus provides unlimited possibility for genetic studies and the related reverse genetics system that allows directed genetic manipulation of an RNA virus is an extremely powerful research tool. In the past twenty years, especially since the first infectious clone of a negative-stranded RNA virus was reported in the mid-1990's, the reverse genetics systems have been available for nearly all the major human and animal RNA virus groups. The article reviews the progress of this technology, highlighting the obstacles in the construction of reverse genetics systems for major groups of human as well as animal RNA viruses and how the virologists overcame them. There are mainly four external expression systems for construction of the RNA virus reverse genetics systems basing on the kind of RNA viruses. These systems include in vitro RNA transcripts, RNA polymerase I-driven expression plasmids, RNA polymerase II-driven expression plasmids and modified vaccinia virus/T7 RNA polymerase-driven expression system. In particular, the viral nucleoprotein and polymerase proteins are required to assemble the viral ribonucleoprotein (RNP) complexes for the rescue of the negative-stranded RNA viruses. Relevant topics about the rescue of the typical viruses are discussed, including poliovirus with the de novo synthesis, Coronaviridae with the largest size of genome, Flaviviridae with the instable clones, HCV with the quasispecies nature, nodaviruses with the virus-host interaction, influenza virus with the RNA pol I transcription system, Arenavirdae with the ambisense coding strategies etc.