The outbreak of COVID-19 poses unprecedent challenges to global health 1 . The new coronavirus, SARS-CoV-2, shares high sequence identity to SARS-CoV and a bat coronavirus RaTG13 2 . While bats may be the reservoir host for various coronaviruses 3,4 , whether SARS-CoV-2 has other hosts remains ambiguous. In this study, one coronavirus isolated from a Malayan pangolin showed 100%, 98.6%, 97.8% and 90.7% amino acid identity with SARS-CoV-2 in the E, M, N and S genes, respectively. In particular, the receptor-binding domain within the S protein of the Pangolin-CoV is virtually identical to that of SARS-CoV-2, with one noncritical amino acid difference. Results of comparative genomic analysis suggest that SARS-CoV-2 might have originated from the recombination of a Pangolin-CoV-like virus with a Bat-CoV-RaTG13-like virus. The Pangolin-CoV was detected in 17 of 25 Malayan pangolins analyzed. Infected pangolins showed clinical signs and histological changes, and circulating antibodies against Pangolin-CoV reacted with the S protein of SARS-CoV-2. The isolation of a coronavirus that is highly related to SARS-CoV-2 in pangolins suggests that they have the potential to act as the intermediate host of SARS-CoV-2. The newly identified coronavirus in the most-trafficked mammal could represent a future threat to public health if wildlife trade is not effectively controlled.As coronaviruses (CoVs) are common in mammals and birds 5 , we used the whole genome sequence of SARS-CoV-2 (WHCV; GenBank accession No. MN908947) in a Blast search of SARS-relate CoV (SARSr-CoV) sequences in available mammalian and avian viromic, metagenomic, and transcriptomic data. This led to the identification of 34 highly related contigs in a set of pangolin viral metagenomes (Extended

The outbreak of 2019-nCoV in the central Chinese city of Wuhan at the end of 2019 poses unprecedent public health challenges to both China and the rest world 1 . The new coronavirus shares high sequence identity to SARS-CoV and a newly identified bat coronavirus 2 . While bats may be the reservoir host for various coronaviruses, whether 2019-nCoV has other hosts is still ambiguous. In this study, one coronavirus isolated from Malayan pangolins showed 100%, 98.2%, 96.7% and 90.4% amino acid identity with 2019-nCoV in the E, M, N and S genes, respectively. In particular, the receptor-binding domain of the S protein of the Pangolin-CoV is virtually identical to that of 2019-nCoV, with one amino acid difference. Comparison of available genomes suggests 2019-nCoV might have originated from the recombination of a Pangolin-CoV-like virus with a Bat-CoV-RaTG13-like virus. Infected pangolins showed clinical signs and histopathological changes, and the circulating antibodies reacted with the S protein of 2019-nCoV.

bPorcine circovirus type 2 (PCV2) is the primary causative agent of porcine circovirus-associated diseases in pigs. To date, viral proteins Cap, Rep, Rep=, and ORF3, encoded by the PCV2 genome, have been described. Here, transcription and translation of a novel viral gene within the PCV2 genome (designated ORF4) was determined and functionally analyzed in vitro and in vivo. Northern blot analysis indicated that the RNA transcribed from the ORF4 gene is about 180 bp in length and overlaps ORF3 in the same direction. Site-directed mutagenesis confirmed that the viral ORF4 protein is not essential for virus replication in PK-15 cells and in mice infected with an ORF4-deficient PCV2 (PCV2⌬). PCV2⌬ triggered higher activity levels of caspase-3 and -8 than wild-type PCV2 (wPCV2) in PK-15 cells. The antigenic epitopes of two mouse monoclonal antibodies (MAbs) raised against the viral ORF4 protein were mapped to the same 19KSSASPR25 peptide. Expression of ORF4 was confirmed using the specific MAbs in wPCV2-infected PK-15 cells and mice. Mice infected with PCV2⌬ had a higher serum viral load (genomic copies) and more severe lymphoid tissue damage in the spleen than those infected with wPCV2. Meanwhile, flow-cytometric analysis indicated that the PCV2⌬ infection caused a significant decrease of CD4 ؉ and CD8 ؉ T lymphocytes. Our results demonstrate that ORF4 is a newly discovered viral protein that is not essential for PCV2 replication but plays a role in suppressing caspase activity and regulating CD4؉ and CD8 ؉ T lymphocytes during PCV2 infection.

Microtubule transport of circovirus from the periphery of the cell to the nucleus is essential for viral replication in early infection. How the microtubule is recruited to the viral cargo remains unclear. In this study, we observed that circovirus trafficking is dependent on microtubule polymerization and that incoming circovirus particles colocalize with cytoplasmic dynein and endosomes. However, circovirus binding to dynein was independent of the presence of microtubular ␣-tubulin and translocation of cytoplasmic dynein into the nucleus. The circovirus capsid (Cap) subunit enhanced microtubular acetylation and directly interacted with intermediate chain 1 (IC1) of dynein. N-terminal residues 42 to 100 of the Cap viral protein were required for efficient binding to the dynein IC1 subunit and for retrograde transport. Knockdown of IC1 decreased virus transport and replication. These results demonstrate that Cap is a direct ligand of the cytoplasmic dynein IC1 subunit and an inducer of microtubule ␣-tubulin acetylation. Furthermore, Cap recruits the host dynein/microtubule machinery to facilitate transport toward the nucleus by an endosomal mechanism distinct from that used for physiological dynein cargo. IMPORTANCEIncoming viral particles hijack the intracellular trafficking machinery of the host in order to migrate from the cell surface to the replication sites. Better knowledge of the interaction between viruses and virus proteins and the intracellular trafficking machinery may provide new targets for antiviral therapies. Currently, little is known about the molecular mechanisms of circovirus transport. Here, we report that circovirus particles enter early endosomes and utilize the microtubule-associated molecular motor dynein to travel along microtubules. The circovirus capsid subunit enhances microtubular acetylation, and N-terminal residues 42 to 100 directly interact with the dynein IC1 subunit during retrograde transport. These findings highlight a mechanism whereby circoviruses recruit dynein for transport to the nucleus via the dynein/microtubule machinery. P orcine circovirus (PCV) belongs to the genus Circovirus of the family Circoviridae. This small icosahedral nonenveloped virus is 17 nm in diameter and has circular single-stranded DNA (1). Two genotypes of PCV have been identified: PCV type 1 (PCV1), which is nonpathogenic to pigs (2), and PCV type 2 (PCV2), which is the etiological agent of PCV2-associated disease leading to swine immunosuppression (3-7). Antibodies (Ab) in humans share antigenic epitopes with PCV (8). Unexpectedly, PCV1 contamination was recently detected in live poliovirus seeds and commercial live-attenuated human rotavirus vaccines (9, 10), and infectious PCV1 was found in the human hepatocellular carcinoma Huh-7 cell line (11). Undoubtedly, PCV exposure poses a potential risk to public health.Of the 11 potential open reading frames (ORF) within the PCV genome, four encode viral proteins (12-15). ORF1 encodes a replicase (Rep) that is responsible for the rolling-circl...