Potential Threats to Human Health from Eurasian Avian-Like Swine Influenza A(H1N1) Virus and Its Reassortants

During 2018-2020, we isolated 32 Eurasian avian-like swine influenza A(H1N1) viruses and their reassortant viruses from pigs in China. Genomic testing identified a novel reassortant H3N1 virus, which emerged in late 2020. Derived from G4 Eurasian H1N1 and H3N2 swine influenza viruses. This virus poses a risk for zoonotic infection.

The role of PA-X C-terminal 20 residues of classical swine influenza virus in its replication and pathogenicity

PA-X is a fusion protein encoded by a +1 frameshifted open reading frame (X-ORF) in PA gene. The X-ORF can be translated in full-length (61 amino acids, aa) or truncated (41 aa) form. However, the role of C-Terminal 20 aa of PA-X in virus function has not yet been fully elucidated. To this end, we constructed the contemporary influenza viruses with full and truncated PA-X by reverse genetics to compare their replication and pathogenicity. The full-length PA-X virus in MDCK and human A549 cells conferred 10- to 100-fold increase in viral replication, and more virulent and caused more severe inflammatory responses in mice relative to corresponding truncated PA-X virus, suggesting that the terminal 20 aa could play a role in enhancing viral replication and contribute to virulence.

An epidemiological investigation of porcine circovirus type 2 and porcine circovirus type 3 infections in Tianjin, North China

Novel porcine circovirus type 3 (PCV3), first identified in the United States, has been detected in many other countries. Porcine circovirus is associated with postweaning multisystemic wasting syndrome, reproductive failure, congenital tremors, and other clinical symptoms. In this study, we established a double polymerase chain reaction assay for detecting both porcine circovirus type 2 (PCV2) and PCV3. This is the first study to detect and characterize the PCV3 genome in the Tianjin region of North China. We collected a total of 169 tissue samples from seven farms between 2016 and 2018. The PCV3-positive rate of all tissue samples was 37.3% (63/169) and the rate of PCV2 and PCV3 coinfection was 14.8% (25/169). PCV2 and PCV3 coinfections with more serious clinical symptoms were found in only three farms. We sequenced three PCV3 strains selected from tissue samples that were positively identified. The complete genome sequences of the three strains shared 97.6-99.4% nucleotide identities with the PCV3 strains in GenBank. Our results showed the extent of PCV3's spread in Tianjin, and the need to further study PCV3's pathobiology, epidemiology, isolation, and coinfection.

Protective efficacy of a bivalent inactivated reassortant H1N1 influenza virus vaccine against European avian-like and classical swine influenza H1N1 viruses in mice

The classical swine (CS) H1N1 swine influenza virus (SIVs) emerged in humans as a reassortant virus that caused the H1N1 influenza virus pandemic in 2009, and the European avian-like (EA) H1N1 SIVs has caused several human infections in European and Asian countries. Development of the influenza vaccines that could provide effective protective efficacy against SIVs remains a challenge. In this study, the bivalent reassortant inactivated vaccine comprised of SH1/PR8 and G11/PR8 arboring the hemagglutinin (HA) and neuraminidase (NA) genes from prevalent CS and EA H1N1 SIVs and six internal genes from the A/Puerto Rico/8/34(PR8) virus was developed. The protective efficacy of this bivalent vaccine was evaluated in mice challenged with the lethal doses of CS and EA H1N1 SIVs. The result showed that univalent inactivated vaccine elicited high-level antibody against homologous H1N1 viruses while cross-reactive antibody responses to heterologous H1N1 viruses were not fully effective. In a mouse model, the bivalent inactivated vaccine conferred complete protection against lethal challenge doses of EA SH1 virus or CS G11 virus, whereas the univalent inactivated vaccine only produced insufficient protection against heterologous SIVs. In conclusion, our data demonstrated that the reassortant bivalent inactivated vaccine comprised of SH1/PR8 and G11/PR8 could provide effective protection against the prevalent EA and CS H1N1 subtype SIVs in mice.

Recombinant pseudorabies virus expressing E2 of classical swine fever virus (CSFV) protects against both virulent pseudorabies virus and CSFV

Both classical swine fever (CSF) and pseudorabies are highly contagious, economically significant diseases of swine in China. Although vaccination with the C-strain against classical swine fever virus (CSFV) is widely carried out and severe outbreaks of CSF seldom occur in China, CSF is sporadic in many pig herds and novel sub-subgenotypes of CSFV endlessly emerge. Thus, new measures are needed to eradicate CSFV from Chinese farms. The emergence of a pseudorabies virus (PRV) variant also posed a new challenge for the control of swine pseudorabies. Here, the recombinant PRV strain JS-2012-ΔgE/gI-E2 expressing E2 protein of CSFV was developed by inserting the E2 expression cassette into the intergenic region between the gG and gD genes of the gE/gI-deletion PRV variant strain JS-2012-ΔgE/gI. The recombinant virus was stable when passaged in vitro. A single vaccination of JS-2012-ΔgE/gI-E2 via intramuscular injection fully protected against lethal challenges of PRV and CSFV. Vaccination of piglets with the recombinant JS-2012-ΔgE/gI-E2 in the presence of high levels of maternally derived antibodies (Abs) to PRV can provide partial protection against lethal challenge of CSFV. Vaccination of the recombinant PRV JS-2012-ΔgE/gI-E2 strain did not induce the production of Abs to the gE protein of PRV or to the CSFV proteins other than E2. Thus, JS-2012-ΔgE/gI-E2 appears to be a promising recombinant marker vaccine candidate against PRV and CSFV for the control and eradication of the PRV variant and CSFV.

Identification of two novel epitopes targeting glycoprotein E of pseudorabies virus using monoclonal antibodies

Pseudorabies virus (PRV), the agent of pseudorabies, has raised considerable attention since 2011 due to the outbreak of emerging PRV variants in China. In the present study, we obtained two monoclonal antibodies (mAbs) known as 2E5 and 5C3 against the glycoprotein E (gE) of a PRV variant (JS-2012 strain). The two mAbs reacted with wild PRV but not the vaccine strain (gE-deleted virus). The 2E5 was located in ¹⁶¹RLRRE¹⁶⁵, which was conserved in almost of all PRV strains, while 5C3 in ¹⁴⁸EMGIGDY¹⁵⁴ was different from almost of all genotype I PRV, in which the 149th amino acid is methionine (M) instead of arginine (R). The two epitopes peptides located in the hydrophilic region and reacted with positive sera against genotype II PRV (JS-2012), which suggests they were likely dominant B-cell epitopes. Furthermore, the mutant peptide ¹⁴⁸ERGIGDY¹⁵⁴ (genotype I) did not react with the mAb 5C3 or positive sera against genotype II PRV (JS-2012). In conclusion, both mAb 2E5 and 5C3 could be used to identify wild PRV strains from vaccine strains, and mAb 5C3 and the epitope peptide of 5C3 might be used for epidemiological investigation to distinguish genotype II from genotype I PRV.

MOV10 inhibits replication of porcine reproductive and respiratory syndrome virus by retaining viral nucleocapsid protein in the cytoplasm of Marc-145 cells

Porcine reproductive and respiratory syndrome virus (PRRSV) has been a major threat to global industrial pig farming ever since its emergence in the late 1980s. Identification of sustainable and effective control measures against PRRSV transmission is a pressing problem. The nucleocapsid (N) protein of PRRSV is specifically localized in the cytoplasm and nucleus of virus-infected cells which is important for PRRSV replication. In the current study, a new host restricted factor, Moloney leukemia virus 10-like protein (MOV10), was identified as an inhibitor of PRRSV replication. N protein levels and viral replication were significantly reduced in Marc-145 cells stably overexpressing MOV10 compared with those in wild-type Marc-145 cells. Adsorption experiments revealed that MOV10 did not affect the attachment and internalization of PRRSV. Co-immunoprecipitation and immunofluorescence co-localization analyses showed that MOV10 interacted and co-localized with the PRRSV N protein in the cytoplasm. Notably, MOV10 affected the distribution of N protein in the cytoplasm and nucleus, leading to the retention of N protein in the former. Taken together, these findings demonstrate for the first time that MOV10 inhibits PRRSV replication by restricting the nuclear import of N protein. These observations have great implications for the development of anti-PRRSV drugs and provide new insight into the role of N protein in PRRSV biology.

Protective efficacy of a high-growth reassortant H1N1 influenza virus vaccine against the European Avian-like H1N1 swine influenza virus in mice and pigs

Swine influenza A viruses (SIVs) causing outbreaks of acute, highly contagious respiratory disease in pigs also pose a potential threat to public health. European avian-like H1N1 (EA H1N1) SIVs are the predominant circulating viruses in pigs in China and also occasionally cause human infection. In this study, a high-growth reassortant virus (SH1/PR8), with HA and NA genes from a representative EA H1N1 isolate A/Swine/Shanghai/1/2014 (SH1) in China and six internal genes from the high-growth A/Puerto Rico/8/34 (PR8) virus, was generated by plasmid-based reverse genetics and tested as a candidate seed virus for the preparation of inactivated vaccine. The protective efficacy of inactivated SH1/PR8 was evaluated in mice and pigs challenged with wild-type SH1 virus. After primer and boost vaccination, the SH1/PR8 vaccine induced high-level hemagglutination inhibiting (HI) antibodies, IgG antibodies, and neutralization antibodies in mice and pigs. Mice and pigs in the vaccinated group showed less clinical phenomena and pathological changes than those in the unvaccinated group. In conclusion, the inactivated high-growth reassortant vaccine SH1/PR8 could induce high antibody levels and complete protection is expected against SH1 wild type SIV, and protection against heterologous EA H1N1 SIV needs further evaluation.

Monoclonal Antibody Against HA Protein of the European Avian-Like H1N1 Swine Influenza Virus

The purified whole-virus proteins derived from A/swine/Shanghai/1/2014 (H1N1) (SH1) were chosen to immunize BALB/c mice to prepare the monoclonal antibody (MAb) against hemagglutinin (HA) protein of an European avian-like (EA) H1N1 swine influenza virus (SIV). After cloning three times by limiting dilution, one strain of hybridoma cells named 3C7 secreting anti-HA protein MAb was obtained by hybridoma technique. The results of indirect immunofluorescence assay and western blot analyses showed that the MAb 3C7 specifically reacted with the HA protein of EA H1N1 SIV. This work indicated that the MAb 3C7 would be a valuable tool as a specific diagnostic reagent for SIV epidemiological surveys and identification of HA protein epitopes of the EA H1N1 SIVs in the future.

The PB2-K627E mutation attenuates H3N2 swine influenza virus in cultured cells and in mice

PB2-627K is an important amino acid that determines the virulence of some influenza A viruses. However, it has not been experimentally investigated in the H3N2 swine influenza virus. To explore the potential role of PB2-K627E substitution in H3N2 swine influenza virus, the growth properties and pathogenicity between H3N2 swine influenza virus and its PB2-K627E mutant were compared. For the first time, our results showed that PB2-K627E mutation attenuates H3N2 swine influenza virus in mammalian cells and in mice, suggesting that PB2-627K is required for viral replication and pathogenicity of H3N2 swine influenza virus.

Genomic characterization of a bovine viral diarrhea virus 1 isolate from swine

The SD0803 strain of the bovine viral diarrhea virus (BVDV) was isolated from a piglet in China in 2008 and has been classified as a novel subgenotype of BVDV-1. To describe the molecular features of this novel subgenotype, we sequenced and characterized the complete genome of the SD0803 virus. The genome is 12,271 bp in length and contains 5' and 3' untranslated regions (UTRs) that flank an open reading frame (ORF) encoding a 3,898-amino-acid polypeptide. The full-length genome of the SD0803 strain shares 78.8% to 83.3% identity with those of other BVDV-1 strains, 70.0% to 70.7% identity with those of BVDV-2 strains, and less than 67.6% identity with those of other pestiviruses. The highest level of shared identity was 83.3% between the complete SD0803 genome and that of the ZM-95 strain of BVDV-1. Phylogenetic analysis of the 5' UTR and the coding sequence for the N-terminal protease fragment of the SD0803 polyprotein indicated that the SD0803 virus is a member of the novel subgenotype BVDV-1q, isolates of which have been identified recently in dairy cattle and camels in China.

Sequence analyses of the representative Chinese-prevalent strain of avian nephritis virus in healthy chicken flocks

Avian nephritis virus (ANV), which belongs to the Astroviridae family, has been associated with acute nephritis in chickens. Cases of ANV infection have been recorded in Japan and in several European countries. However, related studies have never been performed in China. Thus, this study isolated ANV in Chinese chicken flocks. ANV RNA was detected by reverse transcription-PCR in stool samples collected from healthy layer chickens in the Sichuan Province of China in 2009. Of the 192 stool specimens collected, 32.3% (62/192) were positive for ANV infection. The whole genome of ANV-Sichuan54, the first representative Chinese strain, was 6941 nucleotides in length, including the 5' untranslated region, three open reading frames (ORFs), a 3' UTR, and a poly-(A) tail. Comparative and phylogenetic analyses based on partial RNA-dependent RNA polymerase (ORF1b) demonstrated that the majority of ANV investigations were more closely related to the U.S. ANV strain (DQ324827-324836) than to the G-4260 (AB033998).

Human parechovirus infections in monkeys with diarrhea, China

Information about human parechovirus (HPeV) infection in animals is scant. Using 5' untranslated region reverse transcription-PCR, we detected HPeV in feces of monkeys with diarrhea and sequenced the complete genome of 1 isolate (SH6). Monkeys may serve as reservoirs for zoonotic HPeV transmissions and as models for studies of HPeV pathogenesis.

Human parechovirus infections in monkeys with diarrhea, China

Information about human parechovirus (HPeV) infection in animals is scant. Using 5′ untranslated region reverse transcription–PCR, we detected HPeV in feces of monkeys with diarrhea and sequenced the complete genome of 1 isolate (SH6). Monkeys may serve as reservoirs for zoonotic HPeV transmissions and as models for studies of HPeV pathogenesis.

Sequence analysis of an isolate of minute virus of canines in China reveals the closed association with bocavirus

In the present study, we have cloned and sequenced the nearly-full-length genome of minute virus of canines (MVC), SH26, in China. The genome of MVC, 5,132 nucleotides (nts) in length, contains three open reading frames (ORFs), which are 2,325-bp of NS1, 561-bp of NP1 and 2,112-bp of VP1/VP2 encoding three proteins of 774, 186 and 703 residues, respectively. Predicted amino acids sequence of NS1 of MVC has 44% identity with human bocavirus (HBoV) and human boacvirus 2 (HBoV2), NP1 has 48 and 45% identity with HBoV and HBoV2, VP1/VP2 has 45 and 46% identity with HBoV and HBoV2, respectively. Phylogenetic analysis showed that the present Chinese MVC strain was also closely clustered with the previous American and Japanese MVC isolates, and MVCs formed a different branch together with bovine parvovirus and HBoVs from other parvoviruses classified into Parvovirinae.

Full-length coding sequences, polymorphism and chromosomal localizations of the porcine EDG4 and EDG7 genes

EDG4 and EDG7 are identified as cellular receptors for lysophosphatidic acid (LPA), belonging to the endothelial cell differentiation gene (EDG) family of G protein-coupled receptors (GPCR) which play an important role in the function of LPA. In this study, we presented the complete coding sequences of porcine EDG4 and EDG7 genes. The nucleotide sequences and the predicted protein sequences share high sequence identity with other mammals. Spatial expression analysis by reverse transcriptase-polymerase chain reaction (RT-PCR) revealed that porcine EDG4 and EDG7 genes are mainly expressed in brain, liver, spleen, lung, kidney, large intestine, small intestine, but absent in muscle tissues. Radiation hybrid mapping data indicated that EDG4 and EDG7 map to q2.1 of pig chromosome 2 (SSC2) and q2.6-3.2 of pig chromosome6 (SSC6), respectively. A T/C single nucleotide polymorphism (SNP) in the coding sequence of porcine EDG4 was identified. A PCR-restriction fragment length polymorphism (PCR-RFLP) method was employed to genotype this locus among Guizhou Miniature, Guangxi Miniature, Laiwu, Wuzhishan, Tongcheng, Landrace and Yorkshire pigs. The association analysis suggested that the EDG4 genotype was associated with carcass length (P < 0.05) and drip loss percentage (P < 0.05) in the experimental population consisting of Tongcheng, Landrace, Yorkshire and two crossbred porcine populations (Wang et al. Biochem Genet (1-2):51-62, 2007).