Kobuviruses are small, non-enveloped viruses with a single-stranded, positive-sense genomic RNA, belonging to the family Picornaviridae, a highly diverse family of important pathogens of human and other animals. Porcine kobuvirus has been found recently, and consequently, information about the virus is lacking. In this study, we identified porcine kobuviruses from pigs in Korea by RT-PCR, cloning and sequencing, and we showed the existence of genetic diversity among geographically separated porcine kobuviruses through genetic and phylogenetic analysis. Epidemiological studies of porcine kobuvirus linked to diarrhea indicated that porcine kobuvirus infections are endemic in diarrheic pigs in Korea. Statistical analysis of the porcine kobuvirus positive rate between diarrheic and healthy pigs as well as a survey for other enteric pathogens in diarrheic pigs suggests that porcine kobuvirus may play a role as a causative agent of gastroenteritis in pigs.
Middle East Respiratory Syndrome coronavirus (MERS-CoV) causes severe pulmonary infection, with ∼35 % mortality. Spike glycoprotein (S) of MERS-CoV is a key target for vaccines and therapeutics because S mediates viral entry and membrane-fusion to host cells. Here, four different S subunit proteins, receptor-binding domain (RBD; 358-606 aa), S1 (1-751 aa), S2 (752-1296 aa), and SΔTM (1-1296 aa), were generated using the baculoviral system and immunized in mice to develop neutralizing antibodies. We developed 77 hybridomas and selected five neutralizing mAbs by immunization with SΔTM against MERS-CoV EMC/2012 strain S-pseudotyped lentivirus. However, all five monoclonal antibodies (mAb) did not neutralize the pseudotyped V534A mutation. Additionally, one mAb RBD-14F8 did not show neutralizing activity against pseudoviruses with amino acid substitution of L506 F or D509 G (England1 strain, EMC/2012 L506 F, and EMC/2012 D509 G), and RBD-43E4 mAb could not neutralize the pseudotyped I529 T mutation, while three other neutralizing mAbs showed broad neutralizing activity. This implies that the mutation in residue 506-509, 529, and 534 of S is critical to generate neutralization escape variants of MERS-CoV. Interestingly, all five neutralizing mAbs have binding affinity to RBD, although most mAbs generated by RBD did not have neutralizing activity. Additionally, chimeric antibodies of RBD-14F8 and RBD-43E4 with human Fc and light chain showed neutralizing effect against wild type MERS-CoV KOR/KNIH/002, similar to the original mouse mAbs. Thus, our mAbs can be utilized for the identification of specific mutations of MERS-CoV.
Porcine noroviruses (NoVs) and sapoviruses (SaVs), which belong to the family Caliciviridae, have been considered potential zoonotic agents for human infection, and several cases have been reported in Asian countries. In this study, a total of 537 porcine fecal samples collected from 64 swine farms in Korea were tested. Among 537 samples, porcine NoVs were detected by semi-nested RT-PCR in ten samples (1.9%), and porcine SaVs were detected by RT-PCR in 60 samples (11.2%), showing their circulation in Korea. The porcine NoVs were genetically related to strains of genotypes 11 and 18, of genogroup II (GII) of the genus Norovirus. The porcine SaV strains were genetically related to the porcine enteric calicivirus Cowden strain and to the previously identified Korean porcine strains in genogroup III (GIII) of the genus Sapovirus. In no case was co-infection with both NoV and SaV observed in one pig. This is the first report describing porcine NoVs identified in Korea.
Since the 2009 pandemic human H1N1 influenza A virus emerged in April 2009, novel reassortant strains have been identified throughout the world. This paper describes the detection and isolation of reassortant strains associated with human pandemic influenza H1N1 and swine influenza H1N2 (SIV) viruses in swine populations in South Korea. Two influenza H1N2 reassortants were detected, and subtyped by PCR. The strains were isolated using Madin-Darby canine kidney (MDCK) cells, and genetically characterized by phylogenetic analysis for genetic diversity. They consisted of human, avian, and swine virus genes that were originated from the 2009 pandemic H1N1 virus and a neuraminidase (NA) gene from H1N2 SIV previously isolated in North America. This identification of reassortment events in swine farms raises concern that reassortant strains may continuously circulate within swine populations, calling for the further study and surveillance of pandemic H1N1 among swine.
A vaccine protective against diverse HCV variants is needed to control the HCV epidemic. Structures of E2 complexes with front layer-specific broadly neutralizing antibodies (bNAbs) isolated from HCV-infected individuals, revealed a disulfide bond-containing CDRH3 that adopts straight (individuals who clear infection) or bent (individuals with chronic infection) conformation. To investigate whether a straight versus bent disulfide bond-containing CDRH3 is specific to particular HCV-infected individuals, we solved a crystal structure of the HCV E2 ectodomain in complex with AR3X, a bNAb with an unusually long CDRH2 that was isolated from the chronically-infected individual from whom the bent CDRH3 bNAbs were derived. The structure revealed that AR3X utilizes both its ultralong CDRH2 and a disulfide motif-containing straight CDRH3 to recognize the E2 front layer. These results demonstrate that both the straight and bent CDRH3 classes of HCV bNAb can be elicited in a single individual, revealing a structural plasticity of VH1-69-derived bNAbs.
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