Patent ID: 6841364

Claim:
A method of producing a full-length infectious North American PRRSV cDNA having a sequence at least 98% identical to SEQ ID NO:1, the method comprising the steps of: (a) purifying viral genomic RNA from a North American PRRSV virus; (b) generating five overlapping cDNA fragments from the viral genomic RNA using primer pairs comprising: i. SEQ ID NO:2 and SEQ ID NO:6; ii. SEQ ID NO:5 and SEQ ID NO:8; iii. SEQ ID NO:7 and SEQ ID NO:10; iv. SEQ ID NO:9 and SEQ ID NO:13; and v. SEQ ID NO:11 and SEQ ID NO:4; (c) preparing five primary clones, each primary clone comprising a cDNA fragment generated in step (b); (d) preparing intermediate clones, each intermediate clone comprising at least two contiguous primary clones from step (c); and (e) combining the intermediate clones of step (d) in a cloning vector to obtain a full-length cDNA clone; and (f) operably linking at least one promoter sequence to the transcriptional start site of the full-length cDNA clone to obtain a full-length infectious North American PRRSV cDNA having a sequence at least 98% identical to SEQ ID NO:1.