Studies on the prevalence of oncogenic HPV types among Lithuanian women with cervical pathology.

Human papillomavirus (HPV) is the main cause of cervical cancer. Therefore, the detection of oncogenic HPV types is important in predicting the risk of cervical cancer. The aim of the current study was to estimate the prevalence of 16 carcinogenic and potentially carcinogenic HPV types in the study group of Lithuanian women with various grades of cervical pathology in comparison to healthy women. A total of 824 cervical specimens were investigated for HPV DNA: 547 specimens of women with abnormal cytology and 277 specimens of healthy women. Cytological diagnosis was confirmed by histology. For the detection of HPV infection, HPV DNA was amplified by PCR using three different primer systems. HPV DNA was detected in 67.6% of specimens collected from women with abnormal cytology and 24.2% of specimens collected from healthy women. The frequency of HPV-positive specimens correlated with the severity of cervical pathology: it ranged from 50.0% in the subgroup of atypical squamous cells to 80.6% in cervical cancer. In cases confirmed by histology the frequency of HPV-positive specimens ranged from 68.6% in the subgroup of cervical intraepithelial neoplasia grade 1 to 89.2% in cervical intraepithelial neoplasia grade 3 or carcinoma in situ. HPV DNA-positive samples were further investigated for the presence of 16 HPV types by multiplex PCR. The most common HPV type was HPV 16 (detected in 42.3% of HPV-positive specimens) followed by HPV 31 (10.1%), HPV 33 (8.2%), and HPV 56 (5.7%). In contrast, the frequency of HPV 18 was lower as compared to other countries.

Development and characterization of new monoclonal antibodies against human recombinant CA XII.

Carbonic anhydrases (CAs) are enzymes that catalyse the reversible hydration of CO2 to bicarbonate. CA XII is considered a potential biomarker of tumor cells and a promising target for specific therapies. The aim of the current study was to develop new monoclonal antibodies (MAbs) against human recombinant CA XII and evaluate their diagnostic potential. An extracellular catalytic domain of human CA XII was expressed in E. coli and used as an immunogen. Seven stable hybridoma cell lines producing high-affinity IgG antibodies against human CA XII were generated. The majority of MAbs were highly specific to CA XII and did not cross-react with human recombinant CA I, CA II, CA VII, and CA XIII. In order to demonstrate the diagnostic value of the MAbs, they were employed for the immunohistochemistry analysis of CA XII expression in tissues. Two MAbs (15A4 and 4A6) demonstrated a strong and specific immunostaining of CA XII in human tissue specimens. Flow cytometry analysis of 5 human tumor cell lines with the MAb 15A4 revealed its immunoreactivity with cellular CA XII. In conclusion, the MAbs raised against recombinant catalytic domain of CA XII recognize cellular CA XII and represent a promising diagnostic tool for the immunodetection of CA XII-expressing cells.

Monoclonal antibodies raised against 167-180 aa sequence of human carbonic anhydrase XII inhibit its enzymatic activity.

Abstract Human carbonic anhydrase XII (CA XII) is a single-pass transmembrane protein with an extracellular catalytic domain. This enzyme is being recognized as a potential biomarker for different tumours. The current study was aimed to generate monoclonal antibodies (MAbs) neutralizing the enzymatic activity of CA XII. Bioinformatics analysis of CA XII structure revealed surface-exposed sequences located in a proximity of its catalytic centre. Two MAbs against the selected antigenic peptide spanning 167-180 aa sequence of CA XII were generated. The MAbs were reactive with recombinant catalytic domain of CA XII expressed either in E. coli or mammalian cells. Inhibitory activity of the MAbs was demonstrated by a stopped flow CO2 hydration assay. The study provides new data on the surface-exposed linear CA XII epitope that may serve as a target for inhibitory antibodies with a potential immunotherapeutic application.

The use of recombinant pseudotype virus-like particles harbouring inserted target antigen to generate antibodies against cellular marker p16INK4A.

Protein engineering provides an opportunity to generate new immunogens with desired features. Previously, we have demonstrated that hamster polyomavirus major capsid protein VP1-derived virus-like particles (VLPs) are highly immunogenic and can be employed for the insertion of foreign epitopes at certain surface-exposed positions. In the current study, we have designed pseudotype VLPs consisting of an intact VP1 protein and VP2 protein fused with the target antigen--cellular marker p16(INK4A)--at its N terminus. Both proteins coexpressed in yeast were self-assembled to pseudotype VLPs harbouring the inserted antigen on the surface. The pseudotype VLPs were used for generation of antibodies against p16(INK4A) that represents a potential biomarker for cells transformed by high-risk human papillomavirus (HPV). The pseudotype VLPs induced in immunized mice a strong immune response against the target antigen. The antisera raised against pseudotype VLPs showed specific immunostaining of p16(INK4A) protein in malignant cervical tissue. Spleen cells of the immunized mice were used to generate monoclonal antibodies against p16(INK4A) protein. The specificity of antibodies was proven by the immunostaining of HPV-transformed cells. In conclusion, the current study demonstrates the potential of pseudotype VLPs with inserted target antigen as a new type of immunogens to generate antibodies of high diagnostic value.