BSR-T7/5 cells (a cell line derived from BHK-21, which constitutively expresses T7

RNA polymerase [44]) were maintained in Glasgow minimal essential medium (GMEM) supplemented with 4% tryptose phosphate broth, 10% fetal bovine serum (FBS) and were additionally provided with G418 (1 mg mL-1) on every second passage to ensure maintenance of the T7 polymerase gene. BHK-21 cells were grown in Eagle’s minimal essential medium (EMEM) supplemented with 10% FBS. RNA extraction, RT-PCR and nucleotide sequencing RNA was extracted from virus stock of Asia1/JSp1c8, Asia1/JSM4, and Asia1/JS/China/2005 using RNeasy mini kit (Qiagen, Valencia, CA) according to the VRT752271 purchase manufacturer’s instructions. Viral cDNAs were synthesized from the viral RNAs, as previously described [45]. Briefly, viral cDNAs were synthesized using M-MLV reverse transcriptase (Invitrogen, Carlsbad, CA, USA)

with NK61 primer (5′-GACATGTCCTCCTGCATCTG-3′) and the VP1 coding regions were amplified by PCRs with the primer pair NK61/VP31 (5′-TAGTGCTGGYAARGACTTTG-3′). The PCRs were performed using PrimeSTAR HS DNA Polymerase (Takara, Dalian, China). PCR amplifications were carried out for 30 cycles of denaturation at 98°C for 20 s, annealing at 68°C for 1 min, and extension at 72°C for 8 min. Following amplification, the cDNA fragments were purified from agarose gels using a kit (Qiagen) and sequenced YH25448 nmr by Sunny Biotech (Shanghai, China). In order to detect heterogeneity of the VP1 gene,

the amplicons were cloned into a pGEM-T vector (Promega, Madison, WI, USA) using standard molecular cloning techniques [46] and plasmids derived from 10 positive clones for each sample were sequenced. Additionally, the capsid-encoding regions of Asia1/JSp1c8, Asia1/JSM4, and Asia1/JS/CHA/05 were also amplified and sequenced. Construction of genome-length Tyrosine-protein kinase BLK cDNA clone of Asia1/JSp1c8 and derivation of G-H loop VP1 mutants Recombinant DNA techniques were used according to standard procedures [46]. The viral RNA of Asia1/JSp1c8 was used as a template for first-strand cDNA synthesis with M-MLV reverse transcriptase by using specific oligonucleotide primers (E1′, E2′, E3′, E4′, and E5′). A total of five fragments (E1-E5; Figure 5), covering the complete virus genome, were subsequently amplified by PCR. Two fragments (E1 and E2 corresponding to nucleotide 1-390, 362-700) were amplified with the E1/E1′ and E2/E2′ primer pairs by PCR. T7 RNA polymerase promoter was introduced in the E1 primer. Cycling conditions for both PCRs were as follows: initial denaturation at 94°C for 1 min, 30 cycles of 98°C for 20 s, 68°C for 40 s, and then 72°C for 8 min. E12 fragments were generated by overlap PCR fusion E1 and E2 fragments with primer pair E1/E2′. PCR amplifications involved initial denaturation at 94°C for 1 min, followed by 30 cycles of 98°C for 20 s, 68°C for 1 min, then 72°C for 8 min.