Identification of the mimotopes within the major capsid protein L1 of human papillomavirus types 18 and 45, using neutralizing monoclonal antibodies

A sensitive double antibodies sandwich ELISA for the diagnosis and therapeutic evaluation of cervical cancer

BACKGROUND

Vascular endothelial growth factor (VEGF) is a highly specific factor for tumors growth. However, the study on the mechanism of VEGF in cervical cancer, and the correlation between the expression level of VEGF and the therapeutic evaluation, prognosis of cervical cancer is not clear till now.

METHODS

In this study, RT-qPCR and IHC were used to evaluate the abnormal expression of VEGF in cervical cancer. The survival plots of the VEGF expression related to OS were observed by using the KM plotter. The mAbs against VEGF were screened and identified by ELISA addicted test, indirect ELISA, Western-blot, and dot-ELISA. We designed and prepared the overlapping truncations (V1, V2, V3) of VEGF to identify the B cell epitopes. Then, the epitopes recognized by anti-VEGF mAbs were mapped and displayed on a 3D structure of VEGF by using the PyMOL software. The highly specific and sensitive sandwich ELISA was established to detect the total VEGF quantification in 206 clinical sera samples, thus to evaluate the changes of VEGF before and after chemoradiotherapy in cervical cancer patients.

RESULTS

The VEGF was high expressed in cervical cancer tissues and cells, resulting a poor prognosis of cervical cancer. The mAbs 2E5 and 6D9 were selected with the titer of 1:256000 and 1:128000 respectively. The mAbs both had strong ability to combine with VEGF protein within 15 min and were identified as subclass IgG1 with κ-type light chains. 2E5 bound to V1 and V2, recognizing the N-terminal (1-121 aa) of VEGF, however 6D9 bound to V3, recognizing the C-terminal (116-174 aa) of VEGF. The 206 clinical samples were tested with the established VEGF-DAS-ELISA and calculated according to the equation (y = 0.0042088× + 0.105109, R² = 0.998). The results indicated that the expression levels of VEGF in cervical cancer samples were positively higher than those in normal samples. Importantly, we found the expression level of sera VEGF in cervical cancer patients decreased significantly after chemoradiotherapy. Therefore, the variable of VEGF levels in cervical cancer patients before and after treatment can be used as a new indicator of efficacy evaluation to guide the clinical treatment of cervical cancer.

CONCLUSION

A sensitive DAS-ELISA was established successfully, using which we can track the VEGF to evaluate the efficacy and estimate prognosis of cervical cancer. It is helpful for the diagnosis, therapeutic evaluation and prognosis of cervical cancer.

Screening of sperm antigen epitopes by phage display technique and its preliminary clinical application

Background

At present, there is a lack of standardized preparation methods of sperm antigen for the detection of antisperm antibody (AsAb). To screen sperm antigen mimotopes from a phage display random peptide library and use them to establish an enzyme-linked immunosorbent assay (ELISA) for the detection of AsAb, immunoglobulins were extracted from the sera of rabbits with positive AsAb and negative AsAb, respectively, by the saturated ammonium sulfate method, and a phage display 12-mer peptide library was affinity panned by the extracted immunoglobins coated on the ELISA plate. Then, the obtained positive phage clones were identified by ELISA and sent for sequencing and peptides synthesis. Last, a diagnostic ELISA was established to detect clinical serum and seminal plasma samples.

Results

A total of sixty phage clones were chosen by affinity panning, and sixteen of them reacted positively with AsAb in indirect ELISA and sandwich ELISA. Following DNA sequencing and translation, the peptide sequences of the sixteen positive clones were obtained. By comparison in Blast database, four of sixteen positive clones were found to be closely related to male reproduction. Two (#1 and #25) of four mimotopes were synthesized, and an ELISA method was established using the two mimotopes as sperm specific antigens. One hundred and thirty-four serum samples and seventy-four seminal plasma samples from infertile couples were analyzed by the established ELISA with #1 and #25 mimotopes, respectively. The positive rates of AsAb in serum samples were 20.15% (27/134) for #1 and 11.19% (15/134) for #25, respectively, and the coincidence rate between them was 91.04% (122/134). The positive rates of AsAb in seminal plasma samples were 1.35% (1/74) for both #1 and #25, and the coincidence rate was 100%.

Conclusion

Sperm antigen mimotopes can be obtained successfully by the phage display technique, and can be used as standard sperm specific antigens to establish an ELISA method for the detection of AsAb.