High antibody levels and reduced cellular response in children up to one year after SARS-CoV-2 infection.

The COVID-19 course and immunity differ in children and adults. We analyzed immune response dynamics in 28 families up to 12 months after mild or asymptomatic infection. Unlike adults, the initial response is plasmablast-driven in children. Four months after infection, children show an enhanced specific antibody response and lower but detectable spike 1 protein (S1)-specific B and T cell responses than their parents. While specific antibodies decline, neutralizing antibody activity and breadth increase in both groups. The frequencies of S1-specific B and T cell responses remain stable. However, in children, one year after infection, an increase in the S1-specific IgA class switch and the expression of CD27 on S1-specific B cells and T cell maturation are observed. These results, together with the enhanced neutralizing potential and breadth of the specific antibodies, suggest a progressive maturation of the S1-specific immune response. Hence, the immune response in children persists over 12 months but dynamically changes in quality, with progressive neutralizing, breadth, and memory maturation. This implies a benefit for booster vaccination in children to consolidate memory formation.

Accurate Determination of Soluble Axl by Enzyme-Linked Immunosorbent Assay.

Levels of soluble Axl (sAxl) are routinely assessed in human sera by sandwich enzyme-linked immunosorbent assay (ELISA). Although sAxl values are suggested to diagnose different types of disorders, no uniform ELISA method is available, allowing the reliable interassay comparison between results. Furthermore, little is known about the stability of sAxl under storage conditions, which is a relevant parameter for biomedical trials. The evaluation of sAxl stability under various stress conditions and the determination of proper conditions to use the sAxl ELISA for routine clinical applications are of great interest. In this study, serum samples were subjected to freeze-thaw cycles and incubation at different temperatures to analyze the stability of sAxl by ELISA. Dilution and spike-in experiments were carried out to examine the impact of serum and diluent components on the ELISA performance. Various diluents and media were employed to resolve masking effects of the serum. The assay components were further optimized for long-term usability by treatment with stabilizers and validation under temperature stress. Indeed, sAxl showed long-term stability in serum during freeze-thaw cycles and incubation under temperature stress conditions. The dilution experiments revealed that unknown components in the serum caused masking effects that can be reduced by proper dilutions. The assay performance was further increased by using a standardized buffer system to dilute serum samples. Stabilization of coated plates and of streptavidin-horseradish peroxidase allowed long-term storage for up to 6 months. In sum, our data demonstrate proper ELISA conditions, allowing the accurate analysis of sAxl levels in human serum.

Calponin-h2: a potential serum marker for the early detection of human breast cancer?

Early diagnosis is the key for the successful treatment of breast cancer. A serum marker for the early detection of breast cancer could significantly reduce breast cancer morbidity and mortality by bringing the time of diagnosis at an earlier and therefore still curable stage. So far, no biomarker for the early detection is available for the clinical routine. The aim of the present study was to evaluate the use of calponin-h2 as a blood-based biomarker for the early diagnosis of this disease. Using two monoclonal antibodies against calponin-h2, we developed a sandwich ELISA to analyze the serum levels of calponin-h2. In order to evaluate the diagnostic potential of this biomarker, patients with breast cancer (n = 76), benign diseases of the breast (n = 51) and healthy females (n = 24) were analyzed. Serum levels above 10 ng/ml were only observed in patients with breast cancer (n = 8; 10.5%). Further large-scale studies and preanalytic evaluations are necessary to clarify the definite role of calponin-h2 as a biomarker in breast cancer management.