Transcriptomic and metabolomics insights into the mechanisms of chloroquine enhancing PCV2 infection of porcine epithelial cells

Circoviruses, the smallest self-replicating viruses known, appear as non-enveloped icosahedral particles with a diameter of approximately 15 to 20 nm. Their circular genomes are enclosed by 60 copies of the presumably only structural protein in their virions. They have been identified in a wide range of hosts, including fish, insects, birds, and mammals . With the development of genomics sequencing technology, an increasing number of the members of the genus circovirus, such as porcine circovirus (PCV) and human-associated circovirus (huCV), have been identified recently. The propensity barrier to adaptation to new hosts and across species is conferred by the high nucleotide substitution rate of circoviruses as single-stranded DNA (ssDNA) viruses. However, vaccine escape variants that emerge under selective pressure induced by widespread vaccination and antiviral therapy results in fulminant infection and horizontal transmission. Hence, this imposes high demands for immunological protection provided by vaccines.PCV type 2 (PCV2) infection that is widespread worldwide is associated with several diseases including postweaning multisystemic wasting syndrome (PMWS) and porcine dermatitis and nephropathy syndrome (PDNS). The low titer of PCV2 may be related to immunosuppression caused by PCV2 infection. PCV2 isolation and production is routinely performed using porcine kidney epithelial cells (PK-15). Enhanced PCV2 infection of PK-15 cells after inhibition of endosome-lysosome system acidification by chloroquine diphosphate (CQ) may be helpful in the production of PCV2 vaccines. However, the underlying mechanisms by which CQ enhances PCV2 infection of PK-15 cells remain unclear.Along with the development of genomic sequencing technology, there are other omics technologies, such as transcriptomics and metabolomics. The two analyze the expression of messenger RNA (mRNA) and small-molecule metabolites, respectively. The former is closest to the genotype, while the latter is closest to the phenotype. Hence after completing transcriptomic analysis, metabolomic analysis was conducted to comprehensively understand the effects of chloroquine on porcine immature Sertoli cells (iSCs). After transcriptomic approach, there is still a lack of metabolomic approach to be employed to identify the underlying molecular mechanisms by which PCV2 infection of PK-15 cells. In the present paper, transcriptomics and metabolomics are integrated to provide new insights regarding the molecular mechanisms by which CQ enhances PCV2 infection of PK-15 cells.