Native and splice variant mRNA transcripts of PAP are detectable in patients prior to vaccination. Panel A: Shown schematically are the four protein-coding transcripts of PAP including exons which are retained or excluded. Primer sets for ACPP-002 and ACPP-004 were designed to yield a native PAP product of indicated size as well as, if present, a variant PAP product of indicated size and as indicated by the gray boxes. Primer set for ACPP-003 was designed to yield a PAP-TM product of indicated size specific to the transmembrane domain-coding region of that transcript. Panel B: A representative agarose gel image of RTPCR products shows β-actin in lane 1, KLK3 (PSA) in lane 2, ACPP-002 native and variant bands in lane 3, ACPP-003 in lane 4, ACPP-004 native and variant bands in lane 5, no template control in lane 6, and 50 bp DNA ladder in lane 7.