Human papillomavirus type 6 and 11 E4 gene products in condyloma acuminata

The human papillomavirus type 6 (HPV-6) E4 gene was expressed in Escherichia coli as a fusion protein with E. coli beta-galactosidase (E4-beta-Gal), and rabbit antibody against the E4-beta-Gal was prepared. By Western blotting with this antibody, we detected E4 gene products in six out of 18 condyloma acuminata specimens. In four specimens (C-1, C-13, C-14 and C-19), the E4 protein was found as a 10K/11K doublet, but in other specimens (C-8 and C-23), only the 11K protein was detected. By Southern blot analysis, it was found that C-13 harboured HPV-6 DNA but that C-1 and C-8 harboured HPV-11 DNA, indicating that the E4 proteins of HPV-6 and -11 have cross-reactive antigenicity. After incubation at 37 degrees C of the C-23 tissue specimen, the 10K protein was clearly detected. These results suggest that the 10K protein may be derived from the 11K protein by a modification such as proteolytic cleavage before and/or after specimens were taken.