A SARS-CoV-2, N15 strain was successfully isolated from the nasal swab of a pediatric patient after five blind passages in Vero cells. The biological properties of this isolate were investigated extensively. Cytopathic effects (CPE) were observed within 48 hours post- infection, characterized by aggregates of dead cells. The N15 isolate demonstrated the ability to replicate across various human-origin cell lines, albeit with different growth kinetics. Genetic analyses revealed that the strain belongs to the 19B lineage of SARS-CoV-2, showing 99.9% similarity to the original Wuhan 1 strain. Importantly, the N15 strain did not exhibit genetic signatures of in-vitro adaptation and possessed rare mutations N709S in the spike protein and T11M in the E protein. Drug testing indicated that Remdesivir, Molnupiravir, and Nirmatrelvir effectively inhibited this isolate at varying concentrations. The N15 isolate may serve as valuable material for comparative studies with currently circulating SARS-CoV-2 variants.

Porcine circovirus 4 (PCV4), a novel and unclassified member of the genus Circovirus, was first reported in China in 2019. Aimed at providing more evidence about the active circulation of PCV4, this study screened 335 pooled internal organs and detected the virus (i) at the rates of 3.28%, (ii) from both clinical healthy and clinical sick pigs of various age groups, and (iii) in six out of nice provinces of Korea. The complete genomic sequence of a Korean PCV4 strain (E115) was 1,770 nucleotides in length and had 98.5% to 98.9% identity to three PCV4 strains available at GenBank up to date. Utilizing a set of bioinformatic programs, it was revealed that the Korean PCV4 strain contained several genomic features of (i) a palindrome stem-loop structure with conserved nonanucleotide, (ii) packed overlapping ORFs oriented in different directions, and (iii) two intergenic regions in between genes encoding putative replication- associated protein (Rep) and capsid (Cap) proteins. This study also predicted the presence of essential elements known so far for the replication of circoviruses, for example, the origin of DNA replication, endonuclease and helicase domains of Rep, the nuclear localization signal on the putative Cap protein. Finally, based on the phylogeny inferred from sequences of the putative Rep protein, it was suggested that PCV4 belong to genus Circovirus of family Circoviridae and losely related to three previous known porcine circoviruses of PCV1, PCV2 and PCV3.