Host factors are important in determining the outcome of genital human papillomavirus(HPV) infection as demonstrated by an increase in cervical cancers in immunosuppressed patients. HPV proteins may represent immunological target such as serum
antibodies against HPV infection. However, evaluation of the antibody response in patients exposed to high-risk HPV types has been hampered by the lack of a readily avilable source of viral proteins for use as target antigens in serologic assay.
The
goals of the study presented here are 1) to determine whether serum antibodies recognized HPV fusion proteins, 2) to identify which antigens are targets of the humoral immune response, and 3) to assess the prevalence of HPV antibodies in defined
populations. In this study, the assay was tested on selected group of sera from the patients with carcinomas(n=81), squamous intraepithelial lesions(SILs)(n=25) of uterine cervix and normal controls(n=40)using the purified TrpE fusion open
reading
frame
(ORE) proteins of HPV-6b and HPV-16 by Western blot immunoassay.
Restriction enzyme fragement from ORFs of HPV-6b and HPV-16 were expressed in E. Coli as tryptophan E synthetase-HPV fusion proteins through the expression vector pATH. Each fusion protein was induced by 3-indoleacrylic acid and was purified from
the
bacterial lysates for polyacrylamide gel electrophoresis and Western blot immunoassay.
Among women with cervical cancer, 15/81 (19%) and 54/81 (67%) were positive for antibodies by Western blot immunoassay to any gene products of HPV-6b and HPV-16, respectively. And in 25 patients with HPV-related SIL, 10(40%0 were positive for any
of
antibodies for HPV-6b gene products(40%)and 11 were positive for HPV16 related antibodies(44%) the positive prevalence rate for HPV-6b in the sera of SIL patients was significantly higher than that of in the sera of cervical cancer
patients(p<0.05). The
prevalence rates of antibodies to ORF proteins of HPV-16 in the sera of cervical cancer patients were 12%(10/81;E1), 10%(8/81;E2), 21%(17/81;E4), 33%(27/81;E6), 36%(29/81; E7), 37%(30/81;L1), and 11%(9/81;L2) respectively, while 8%(2/25) were for
E1,
8%(2/25)for E2, 12%(3/25) for E4, 40%(10/25) for E6, 32%(8/25) for E7, 28%(7/25)for L1, and 8%(2/25)for L2 among the patients with HPV-related cervical SILs. The positive prevalence rate for HPV-16 in the sera of SIL and cervical cancer patients
was
significantly higher than that of in the sera of normal controls(p<0.01).
There was decreasing pattern of positivity against E6 protein of HPV-16 with the severity of cervical cancer, but there were no significant differences in positivities of other antibodies in the patients of cervical cancers according to the
different
stage of disease.
These results suggest that the recombinant proteins from HPV-6b and HPV-16 may be useful in the immunologic diagnosis of HPV-related cervical SILs and cervical cancers respectively and antibodies to HPV-16 E7 and L1 proteins appear to be
virus-specific
and disease-specific markers for HPV-associated cervical neoplastic lesions.
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