Pulike Biological Engineering, Inc.

Gemykibiviruses are circular, replication-associated protein (REP) encoding single-stranded DNA (ssDNA) viruses classified within the genus Gemykibivirus of the family Genomoviridae. In recent years, several gemykibiviruses have been detected in humans presenting with clinical symptoms, such as encephalitis, respiratory illness, sepsis, pericarditis, diarrhea, and multiple sclerosis. However, the presence of gemykibiviruses in other animal hosts, as well as the evolution of the Gemykibivirus genus, remains poorly understood. In this study, we identified a novel gemykibivirus from a diarrheic pig in China using metagenomic sequencing, which we designated as pGkV. The pGkV genome comprises 2200 nucleotides and encodes two key proteins as follows: the capsid-associated protein (CAP) and the REP. Phylogenetic analyses revealed that pGkV clusters within the zoonotic gemykibivirus (ZooGkV) clade, which includes nearly all gemykibivirus species recently identified in humans. Mutation and haplotype analyses revealed that pGkV is closely related to an avian gemykibivirus, while its CAP and REP proteins are identical to those of a human gemykibivirus, underscoring its potential zoonotic capability. Furthermore, recombination signals were detected among Zoo-GkVs, suggesting that recombination may contribute to the emergence of novel gemykibivirus strains. The identification of pGkV provides new insights into the evolution and cross-species transmission of gemykibiviruses.

Canine parvovirus-2 (CPV-2) infection causes serious multisystemic disease in dogs and many animal species worldwide. Previously, a monoclonal antibody (MAb) of CPV-2, 10H4, showed high neutralizing activity and therapeutic effect against CPV-2 in dogs. However, the application of mouse MAb is limited in other animals due to immune rejection. Here, the variable regions of the heavy and light chains of 10H4 were cloned and ligated with constant canine antibody regions to produce a canine-derived chimeric MAb 11D9, in a CHO-S cell expression system. The cell supernatant of the CHO cell line 11D9 exhibited a HI titer of 1:2560 against all the variants of CPV-2 (new CPV-2a, new CPV-2b, and CPV-2c), and had the same average neutralization titer as the new CPV-2a (1:11,046.5) and new CPV-2b (1:11,046.5) variants, which was slightly higher than that of CPV-2c variants (1:10,615.7). In animal experiment, the treatment of chimeric MAb 11D9 had a high therapeutic effect in beagles infected with the new CPV-2a. Overall, the canine-derived chimeric MAb 11D9 produced by CHO-S cells showed a high HI and neutralization titer against CPV-2 and the therapeutic effects against the new CPV-2a in beagles, providing potential for the prevention or treatment of CPV-2 infections in dogs.

Porcine epidemic diarrhea (PED) caused by porcine epidemic diarrhea virus (PEDV) is one of the most devastating diseases in the global pig industry due to its high mortality rate in piglets. Maternal vaccines can effectively enhance the gut-mammary gland-secretory IgA axis to boost lactogenic immunity and passive protection of nursing piglets against PEDV challenge. From 2017 to 2021, we collected 882 diarrhea samples from 303 farms in China to investigate the epidemiology of PEDV. The result showed that about 52.15% (158/303) of the farms were positive for PEDV with an overall detection rate of 63.95% (564/882) of the samples. The S1 fragments of S gene from 104 strains were sequenced for the phylogenetic analysis. A total of 71 PEDV strains (68.27%) sequenced in this study were clustered into the predominant G2c subgroup, while the newly-defined G2d strains (9.62%) were identified in three provinces of China. The NH-TA2020 strain of G2c subgroup was isolated and cultured, and its infection to piglets caused watery diarrhea within 24 ​h, indicating its strong pathogenicity. Oral administration of NH-TA2020 strain to pregnant gilts stimulated high levels of IgA antibody in colostrum. The piglets fed by the gilts above were challenged with NH-TA2020 strain or CH-HeB-RY-2020 strain from G2d subgroup, and the clinical symptoms and virus shedding were significantly reduced compared to the mock group. Our findings suggest that G2c subgroup is the predominant branch circulating in China from 2017 to 2021. Oral administration of NH-TA2020 enhances maternal IgA and lactogenic immune responses, which confer protection against the homologous and emerging G2d PEDV strains challenges in neonates.