ABSTRACT
Hepatitis E virus (HEV) is an enteric pathogen of humans and animals, and pigs have been considered an important reservoir of this virus. Recent evidence has indicated the cross-species transmission of hepatitis E virus (HEV) from pigs to humans, causing zoonosis, mostly via consumption of uncooked or undercooked animal meat/viscera. In this study, we have developed a one-step RT-LAMP assay for rapid detection of swine HEV. Specific primer sets targeting the ORF3 gene were designed. The sensitivity of the RT-LAMP assay was 10(1) copies/µl of RNA template, which was tenfold higher than that of RT-nPCR. The specificity of this assay was demonstrated by the lack of amplification of DNA/RNA from other swine viruses. Furthermore, a total of 41 bile samples were subjected to RT-LAMP and RT-nPCR. Eighteen positive samples were detected by RT-nPCR, while 36 positive samples were detected by RT-LAMP, indicating that the sensitivity of the RT-LAMP assay was higher than that of the conventional RT-nPCR assay. The RT-LAMP assay reported here may be used for diagnosis of swine HEV, not only in laboratories but also under field conditions.
Subject(s)
Hepatitis E virus/isolation & purification , Hepatitis E/veterinary , Nucleic Acid Amplification Techniques/veterinary , Swine Diseases/virology , Animals , Bile/virology , Gene Expression Regulation, Viral , Hepatitis E/diagnosis , Hepatitis E/virology , Hepatitis E virus/genetics , Nucleic Acid Amplification Techniques/methods , Phylogeny , RNA, Viral/genetics , RNA, Viral/isolation & purification , Reverse Transcriptase Polymerase Chain Reaction/methods , Reverse Transcriptase Polymerase Chain Reaction/veterinary , Sensitivity and Specificity , Swine , Swine Diseases/diagnosisABSTRACT
BACKGROUND: Porcine reproductive and respiratory syndrome virus (PRRSV) has been acknowledged as one of the most important agents affecting swine. The scavenger receptor CD163 is one of the important entry mediators for PRRSV. RESULTS: The tD4 and tD5 CD163 genes were amplified, and the PCR products were cloned into pET-28a(+) (designated pET-28a-tD4 and pET-28a-tD5, respectively). The plasmids pET-28a-tD4 and pET-28a-tD5 were then transformed into the E. coli BL21 (DE3) strain and expressed by adding 1 mmol/L of isopropyl-beta-D-thiogalactopyranoside. The proteins were highly expressed in the supernatant from the tD4- and tD5-producing cells that were incubated with a binding buffer containing the following compounds: ß-mercaptoethanol, urea, Tween 20, glycerol, and SDS, while they were rarely expressed in the supernatant from the tD4- and tD5-producing cells that were incubated with binding buffer without the compounds. The tD4 and tD5 proteins were purified, and BALB/c mice were immunized with the purified proteins. Western blotting analysis showed that the tD4 and tD5 proteins were capable of reacting with tD5 antibodies; the titer of both the tD4 and tD5 antiserums was 1:160 against the tD5 protein, as shown by ELISA. CONCLUSIONS: These studies provide a new way for the purification of proteins expressed in inclusion bodies and the preparation of the corresponding antibodies.