Naturally circulating antibodies could dramatically change the activity of immunogens. In some cases, cross-interference between antibodies led to the loss of their opsonizing ability. Therefore, the study of antibody repertoire in blood sera of healthy donors is helpful for the development of vaccines and diagnostic kits. Levels of antibodies to fragments of biologically significant glucosamine and galactosamine polysaccharides and their N-acetylated derivatives were first studied in blood sera of 34 healthy donors using six biotinylated carbohydrate ligands. The highest titer of antibodies was found to poly-β-(1→6)-N-acetylglucosamine (PNAG), including its fully de-N-acetylated fragment. High antibody titers to the galactosaminoglycan (GG) fragments were also detected. For both PNAG and GG, the level of antibodies to N-acetylated ligands was higher than to the ligands with free amino groups. A correlation between the antibody titers for the respective N-acetylated and N-deacetylated forms was observed, which may suggest a cross interaction. No significant amounts of the antibodies to the chitooligosaccharides were detected. The results obtained will help to rationally plan further immunological studies aimed at the development of new vaccines and diagnostic kits.

Fungal mannans are polysaccharide antigens located on the cell wall surface of various representatives of the fungal kingdom. Titers of the IgG antibodies to Candida albicans mannan are determined in the diagnosis of the candidiasis infection. Owing to high complexity and heterogeneity of the structure of natural mannans, the determination of the exact epitope structure recognized by antibodies is extremely important for the improvement of diagnostic tools based on the detection of anti-mannan antibodies. A high level of the antibodies to mannan was also found in healthy donors. However, it remains undetermined what structural epitope was recognized in this case. The levels of the IgG and IgM antibodies against individual structural fragments of mannan in the blood sera of healthy donors were determined. The anti-mannan antibody response was measured using enzyme immunoassay in a random sample of 31 blood sera of healthy donors on a panel of 11 synthetic mannooligosaccharides of various structures. A high antibody titer was found for the antigens containing the β-mannosidic bond, and the highest values were achieved in the case of two (1→2)-linked β-mannose residues. No significant level of the antibodies was revealed for antigens containing only α-mannose residues. Thus, it can be concluded that β-mannans appear to be much stronger antigens. It is assumed that the detection of antibodies to β-mannans in the sera of healthy donors can be a source of false positive results in the serological diagnosis of the Candida infection.

Background. Implementation of immunotherapy in clinical oncological practice has significantly improved the results of cancer treatment. It resulted in the need for seeking new markers to assess the effectiveness of therapy and the disease prognosis.Aim. To analyze the content of soluble forms of PD-1 and PD-L1 immune checkpoint proteins in the blood serum of patients with non-small cell lung cancer and esophageal squamous cell carcinoma and their association with clinical and morphological characteristics of the disease and the disease prognosis.Materials and methods. The study included tumor samples obtained from 43 patients with non-small cell lung cancer and 21 patients with esophageal squamous cell carcinoma. The concentration of sPD-L1 and sPD-1 in the blood serum was determined using enzyme-linked immunosorbent assay (ELISA). The Mann – Whitney test was used to determine statistically significant differences in independent groups. A correlation analysis was performed using the Spearman’s rank correlation coefficient. Overall survival was analyzed by constructing survival curves using the Kaplan – Meier method and a Cox proportional hazards model. The differences were considered statistically significant at p < 0.05.Results. The study showed that sPD-1 and sPD-L1 were found in the blood serum of both cancer patients and healthy donors, and their concentrations did not differ significantly. It was shown that the high concentration of sPD-L1 in the blood serum of patients with non-small cell lung cancer was significantly associated with the late stage of the disease and was an independent unfavorable prognostic factor. It should be noted that for patients with esophageal cancer, an unfavorable prognostic marker was the high concentration of the soluble form of PD-1 protein, and not PD-L1 ligand, as in case of lung cancer.Conclusion. The content of sPD-1 and sPD-L1 in the blood serum can have different prognostic significance for various types of cancer, and further studies are required to confirm their clinical usability.

Zonulin content in blood serum of patients with colorectal cancer (CRC; n =152; 30-84 years) and patients with large bowel adenomas ( n =32; 39-82 years) was measured by standardized kit IDK Zonulin ELISA (Immundiagnostik AG). The healthy control group ( n =50) comprised volunteers (27 women, 23 men; 25-68 years); pathological control group ( n =84) — patients (55 women, 29 men;18-84 years) with irritable bowel syndrome ( n =29), Crohn’s disease ( n =5), and ulcero-necrotic colitis ( n =50). In comparison to healthy control group, the level of zonulin was significantly increased in CRC patients ( p <0.0000001) and in patients with benign large bowel tumors ( p <0.004), as well as in patients with inflammatory intestine diseases and with irritable bowel syndrome ( p <0.0002). Zonulin level in blood serum of CRC patients was slightly, but significantly higher ( p <0.05) than in the group of pathological control. ROC curve construction revealed that at optimal zonulin cut-off level (52.2 ng/ml), the diagnostic sensitivity of CRC detection was 66.7% and specificity relative to healthy control was 81.8%. The specificity relative to the combined control group (healthy control+non-tumor bowel diseases) was only 68.9%. Thus, no acceptable cut-off levels for differentiation between malignant and benign tumors, as well as between tumor and non-tumor large bowel pathologies were found. Analysis of the associations between serum zonulin level and the main clinical and pathological characteristics of CRC demonstrated that the level of this marker increased with disease progression ( p <0.01; Kruskal—Wallis test), but was not associated with individual criteria of the TNM system, tumor localization, histological structure, and malignancy grade.