Transcript expression by immunoprecipitation (A) and Western blotting (B). HPV-L1 expression was tested in cells infected with 5 PFU/cell of the FPL1 recombinant virus. By immunoprecipitation, HPV-L1 was detected only in MRC-5 cells (A, lane 6), whereas by Western blotting HPV-L1 expression was seen not only in MRC-5 cells (B, lane 5), but also in Vero cells (B, lane 2). Both immunoprecipitation and Western blotting were performed using the CamVir-1 monoclonal antibody. HPV-L1 produced by an engineered bacterial vector was used as a molecular weight marker (lane 6) and CaSki cells as a positive control (lane 3). No specific proteins were seen in mock-infected (A, lanes 1, 4) and FPwt-infected (A, lanes 2, 5; B, lanes 1, 4) cells or in replication-permissive CEFs (data not shown). HPV-L1 (B, lane 6) and CaSki cells (A, lane 7; B, lane 3), used as positive controls, also showed a clear 55-kDa band.