Enzyme-Linked Immunosorbent Assay Using Fusion Protein for Detection of Serum Antibodies to Human Papillomavirus Type 16 E7 in Patients with Cervical Cancer

Kim, Jae Weon; Park, Noh Hyun; Kee, Sun Ho; Song, Yong Sang; Kang, Soon Beom; Lee, Hyo Pyo

Abstract

BACKGROUND: Human papillomavirus(HPV) 16 is the most frequently found oncogenic HPV type in cervical cancer and the early protein E7 is considered to be one of the two major proteins involved in malignant transformation and maintenance of the transformed phenotype of the cells. It is suggested that serologic detection of anti-HPV antibody in serum can be used as a marker for HPV-associated cervical cancer. We evaluated the efficacy of enzyme-linked immunosorbent assay(ELISA) method for detecting antibodies circulating in human sera against E7 proteins of HPV 16 in patients with cervical cancer/cervical intraepithelial neoplasia(CIN) and in normal controls.
MATERIALS AND METHODS
We have developed a ELISA method using fusion proteins of HPV 16 E7, expressed in E. coli, as antigen to detect the anti-E7 antibody in human sera. Sera from 276 women(90 patients with invasive cervical cancers, 8 patients with CIN III and 178 healthy women) were tested for the presence of antibodies to E7 proteins. The results were compared with that of polymerase chain reaction(PCR) method.
RESULTS
Fifteen(16.7 %) of the 90 cervical cancer sera, one(12.5 %) of the 8 CIN sera and twelve (6.7 %) of the 178 normal sera were reactive with E7 proteins(cut-off value : absorbance (A) = 0.079, x + 3 SD). The detection rate of HPV 16 DNA by PCR were 45.5 %(41/90) in cervical cancer patients, 37.5 %(3/8) in CIN III patients, and 11.8 %(21/178) in normal controls Twelve(29.3 %) of 41 cervical cancer patients harboring HPV 16 DNA showed positive for the anti-E7 antobody. Although the positivity with ELISA was rather lower that of PCR. A statistically significant trend of increasing seropositivity was obtained( 2=6.48 ; df=1 ; p=0.011). The concordance rate between the results of ELISA and PCR was 64.4 %.
CONCLUSION
The increasing seropositivity for HPV 16 E7 antibodies in association with malignant progression suggest that these antibodies may be a useful marker for HPV 16-associated cervical cancer. But the facts that in only about one-fifth portion of patients with cervical cancer showed the positive results in ELISA restricts the direct clinical applications. A search for more sensitive and specific serologic method for the detection of antibodies to HPV 16 E7 is needed.