PAICS and infection: In R20523 family, VpAHPND infection up-regulated the expression of glucose-6-phosphate 1-dehydrogenase (G6PD), phosphoribosylformylglycinamidine synthase (PFAS), ALDO, phosphoribosylaminoimidazole-succinocarboxamide synthase (PAICS), IMP cyclohydrolase (purH), adenylate cyclase (AC), 5'-nucleotidase, beta-ureidopropionase (UPB1), and cAMP-specific phosphodiesterase (PDE), and increased the content of adenosine, adenine, deoxyinosine for purine and pyrimidine metabolism.