Pigs with highly prevalent antibodies to human coronavirus and swine haemagglutinating encephalomyelitis virus in the Tohoku District of Japan

Evidence for cross-species transmission of human coronavirus OC43 through bioinformatics and modeling infections in porcine intestinal organoids

Cross-species transmission of coronaviruses has been continuously posing a major challenge to public health. Pigs, as the major animal reservoirs for many zoonotic viruses, frequently mediate viral transmission to humans. This study comprehensively mapped the relationship between human and porcine coronaviruses through in-depth bioinformatics analysis. We found that human coronavirus OC43 and porcine coronavirus PHEV share a close phylogenetic relationship, evidenced by high genomic homology, similar codon usage patterns and comparable tertiary structure in spike proteins. Inoculation of infectious OC43 viruses in organoids derived from porcine small and large intestine demonstrated that porcine intestinal organoids (pIOs) are highly susceptible to human coronavirus OC43 infection and support infectious virus production. Using transmission electron microscopy, we visualized OC43 viral particles in both intracellular and extracellular compartments, and observed abnormalities of multiple organelles in infected organoid cells. Robust OC43 infections in pIOs result in a significant reduction of organoids viability and widespread cell death. This study bears essential implications for better understanding the evolutionary origin of human coronavirus OC43, and provides a proof-of-concept for using pIOs as a model to investigate cross-species transmission of human coronavirus.

Development of an Immunochromatographic Strip for Serological Diagnosis of Porcine Hemagglutinating Encephalomyelitis Virus

An immunochromatographic strip was developed for the detection of an antibody against Porcine hemagglutinating encephalomyelitis virus (PHEV). Colloidal gold–labeled rabbit anti-pig immunoglobulin G (IgG) was used as the detection reagent, and the PHEV recombinant antigens and goat anti-rabbit IgG were coated on the prototype strip and the control lines, respectively. The immunochromatographic strip was capable of specifically detecting PHEV antibodies in serum with a hemagglutination inhibition (HI) titer of 2 within 10 min. Storage of the strips at room temperature for 6 months or at 4°C for 12 months did not change their sensitivity and specificity. Using HI as a reference test, the relative specificity and sensitivity of the immunochromatographic strip were determined to be 93.41% and 98.42%, respectively. There was a strong agreement between the results obtained by HI and the immunochromatographic strips (κ = 0.926). Additionally, there was a strong agreement between enzyme-linked immunosorbent assay and immunochromatographic strips (κ = 0.929). When the immunochromatographic strip was used for serological diagnosis of 1,117 serum samples in Jilin Province in China, the seropositivity ranged from 6.5% in the Liaoyuan District to 81.6% in the Changchun District. Furthermore, many piglets were seropositive to PHEV, indicating the possible transfer of maternal antibodies via the colostrum. Based on the high specificity, sensitivity, and stability of the immunochromatographic strip, it would be suitable for on-site detection of PHEV antibodies in order to monitor PHEV infections in an animal population.

Detection and genetic analysis of porcine hemagglutinating encephalomyelitis virus in South Korea

Porcine hemagglutinating encephalomyelitis virus (PHEV) causes vomiting and wasting disease (VWD) or encephalomyelitis, and primarily affects pigs under 3 weeks of age. In this study, we detected PHEV from clinically ill pigs in conventional pig farms in South Korea. From November 2009 to March 2010, a total of 239 pig tissue samples from 91 farms were tested by nested RT-PCR. Among 239 samples, 22 samples from 17 farms were positive for PHEV. The detection rate of suckling pigs, weaning pigs, growers and finishers were 14.3% (12/84), 6.5% (7/107), 7% (3/43), and 0% (0/5), respectively. Symptoms were neurological, respiratory, enteric sign (diarrhea), or nasal bleeding. All pigs were co-infected with other viruses and bacteria and this might have resulted in age variation and clinical signs in the affected pigs. Phylogenetic analysis showed that the PHEV-positive samples and PHEV reference strains were clustered in the same group. These findings imply the presence of only one genogroup of PHEV, regardless of porcine age, clinical signs, and geographical location.

Neutralizing test of hemagglutinating encephalomyelitis virus (HEV) in FS-L3 cells cultured without serum

FS-L3 cells, originating from porcine kidney, were used for propagation of Hemagglutinating encephalomyelitis virus (HEV) and development of a virus neutralizing (VN) test. Sera of pigs, rats, cows and dogs had VN activities to HEV. On the other hand, sera of mice, rabbits, goats, sheep, horses, cats, chickens, hamsters and human did not have measurable VN activities, although these sera had high HI activities. Our results support the idea that the VN is a more reliable measure of HEV infection than the conventionally used HI test.