Regulation of porcine endogenous retrovirus by dual LTR1+2 (Long Terminal Region) miRNA in primary porcine kidney cells.

Porcine endogenous retroviruses (PERVs) integrate into germline DNA as proviral genome that enables vertical transmission from parents to their offspring. The provirus usually survives as part of the host genome rather than as an infectious agent, but may become pathogenic if it crosses species barriers. Therefore, replication-competent PERV should be controlled through selective breeding or knockout technologies. Two microRNAs (miRNAs), dual LTR1 and LTR2, were selected to inhibit the expression of PERV in primary porcine kidney cells. The inhibition efficiency of the miRNAs was compared based on their inhibition of different PERV regions, specifically long terminal repeats (LTRs), gag, pol, and env. Gene expression was quantified using real-time polymerase chain reaction and the C-type reverse transcriptase (RT) activity was determined. The messenger RNA (mRNA) expression of the PERV LTR and env regions was determined in HeLa cells co-cultured with primary porcine kidney cells. The mRNA expression of the LTR, gag, pol, and env regions of PERV was dramatically inhibited by dual miRNA from 24 to 144 h after transfection, with the highest inhibition observed for the LTR and pol regions at 120 h. Additionally, the RT activity of PERV in the co-culture experiment of porcine and human cells was reduced by 84.4% at the sixth passage. The dual LTR 1+2 miRNA efficiently silences PERV in primary porcine kidney cells.

Complete Genome Sequences of Porcine Deltacoronavirus Strains DH1/2016 and DH2/2016 Isolated in South Korea.

Two porcine deltacoronavirus (PDCoV) strains, named DH1/2016 and DH2/2016, were isolated from feces of piglets which had severe watery diarrhea symptoms. A comparison of the complete genome sequences suggested that the DH1/2016 and DH2/2016 strains are highly homologous to each other and to PDCoVs isolated in early 2014 from the United States.

Phylogenetic and recombination analysis of genomic sequences of PCV2 isolated in Korea.

The complete genomic sequences of 13 PCV2 viruses obtained between 2005 and 2007 were analyzed in order to determine their phylogenetic relationship and identify possible recombination events between PCV2a and PCV2b. Twelve PCV2b viruses and one PCV2a virus were identified by phylogenetic analysis. Notably, two PCV2b viruses (PF163 and C7201-1) were shown to belong to the 1B subgroup of PCV2b, which had not been previously reported in Korea. Theses two viruses were also predicted to be possible recombinants between PCV2a (the minor parent) and PCV2b (the major parent) by the RDP program (P < 0.01). A recombination site was predicted to exist in ORF1 of both viruses. This additional evidence of PCV2 recombination in Korea further supports the important role of recombination in genetic evolution.