Abstract
To determine the cross-reactivity between early (E) proteins of different human papillomavirus (HPV) types, 346 serum samples were tested with E4 and E7 of HPV 16. Two hundred and sixteen of them were also tested with HPV 1 E4, 21 with HPV 11 E4 and E7, and 109 with HPV 18 E4 and E7. Viral fusion proteins were expressed in
Escherichia coli and used as antigens in Western blot experiments. The sera were obtained from patients with HPV-associated genital lesions or cervical cancer, from renal transplant recipients and from patients hospitalized for reasons unrelated to HPV infections (the controls). In contrast to findings relating to HPV 16 E4 specific antibodies, the prevalence of antiHPV 1 E4 antibodies was not greater in renal transplant recipients than in the controls. In each age group of the control population more sera reacted with HPV 1 E4 than with HPV 16 E4. Sera of patients with HPV-associated cervical diseases and cervical cancer reacted less frequently with HPV 11 E4 or E7 and HPV 18 E4 or E7, respectively, than with the corresponding HPV 16 proteins. Thirty of 117 HPV 16 E4 or E7 positive sera showed reactivity to the corresponding protein of either HPV 1, 11 or 18. As demonstrated by cross-absorption experiments performed with 26 of the doublereacting sera, 24 contained two populations of antibodies reacting with proteins of different HPV types whereas only two contained cross-reacting antibodies. We concluded that in the majority of sera antibodies to the HPV 16 E4 and E7 proteins are type-specific.