Autoantibodies (Abs) to thyroid antigens are associated with autoimmune thyroid disease (AITD), although sometimes they have no clear clinical significance. The aim of this study was to evaluate the avidity of thyroid Abs in the sera of AITD patients and non-AITD Abs carriers. A multiplex microarray-based assay was developed to detect the avidity of thyroid disease-associated Abs, including Abs to thyroperoxidase (TPO), thyroglobulin (Tg), pendrin, thyroid hormones T3 and T4, pyruvate kinase, and carbonic anhydrase 2. The method is based on indirect multiplex assay with an additional step involving the chaotrope destruction of the autoantibody-antigen complexes. The avidity index (AI) is then calculated. The method was tested on clinical cohort (n =117) and then confirmed by studies with another independent cohort (n =123). For the confirmation study, the median AI for AbTg was 29.9% among healthy Abs carriers, 52.6% for AITD patients, and 92.7% for non-AITD type 1 diabetes (T1D) patients. Median AI for AbTPO were 39.9% in healthy carriers, 73.4% in AITD patients, 83.2% in T1D patients, and 98.5% in AITD patients with thyroid neoplasm. The presence of high-avidity AbTg in T1D patients was also confirmed by a modified ELISA. Identification of high-avidity autoantibodies to thyroid proteins in non-thyroid T1D patients requires further studies.

Several methods can be used to evaluate antibody avidity, one of which is the modified ELISA, in which a chaotropic agent is added to disrupt the binding between the antigen and the antibody. Although the avidity index provides relevant information about the functionality of antibodies, it does not allow us to characterize which antigens the antibodies are strongly bound to. To this end, we adapted the Immunoblot and Dot-Blot techniques by adding potassium thiocyanate (KSCN) after incubating nitrocellulose membranes with serum from mice immunized with Neisseria meningitidis outer membrane vesicles (OMVs) or serum from mice immunized with recombinant receptor-binding domain (RBD) of SARS-CoV-2, with different adjuvants for each antigen. In terms of results, when standardizing the incubation time of sera with KSCN, we observed that 5 minutes was the ideal time for both assays, however, when using different dilutions of serum from mice immunized with RBD, there was an influence on the strength of antigen-antibody binding. For the N. meningitidis assay, the antibodies maintained high avidity for the antigens present in the OMVs, PorA, NadA, and Opa, especially in the presence of the aluminum hydroxide adjuvant. The research showed that standardizing the Immunoblot and Dot-Blot in the same assay optimizes time and resources, allowing qualitative analysis for two different antigens, and resulting in more robust information for immunization studies against these pathogens.

: (1) Background: Healthcare workers (HCWs) are a well-known risk group for coronavirus infections with increased working hours in a potentially infectious environment. We evaluated both IgG and Neutralizing antibody levels, with IgG avidity index and persistence among health workers. (2) Methods: 1001 HCWs were tested for both IgG and Neutralizing antibodies. IgG avidity testing and one-year follow-up testing were done on selected HCWSs. (3) Results: COVID-19 IgG antibody levels were high among 299 (94.62%) HCWs with a history of COVID-19 infection (p <0.0001) compared with 479 (69.92%) HCWs who were not infected with COVID-19 during the first and second wave. A total of 899 (89.81%) HCWs had more than 50% neutralizing antibodies while the remaining 102 (10.19%) HCWs had less than 50% of Neutralizing antibodies. The avidity index was maintained at almost 40% (Gray zone). Both antibody levels were found markedly increased after one year when compared to initial results. (4) Conclusions: Healthcare workers are at a 2.29-fold higher risk of infection; Two folds higher IgG levels in HCWs involved in COVID-19 duty and their persistence for a longer time than in other groups signifies IgG antibody role in the prevention of severe disease in HCWs involved in Covid-19 patient care.

To increase the prediction accuracy of positive oral food challenge (OFC) outcome during stepwise slow oral immunotherapy (SS-OIT) in children with hen’s egg (HE) allergy, we evaluated the predictive value of the combination of antigen-specific IgE (sIgE) with antigen binding-avidity and sIgG4 values. Sixty-three children with HE allergy undergoing SS-OIT were subjected to repeated OFC with HE. We measured the ovomucoid (OVM)-sIgE by ImmunoCAP or densely carboxylated protein (DCP) microarray, sIgG4 by DCP microarray, and the binding-avidity of OVM-sIgE defined as the level of 1/ IC50 (nM) measured by competitive binding inhibition assays. The OFC was positive in 37 (59%) patients undergoing SS-OIT. Significant differences in DCP-OVM-sIgE, CAP-OVM-sIgE, I/ IC50, DCP-OVM-sIgG4, the multiplication products of DCP-OVM-sIgE and binding-avidity of DCP-OVM-sIgE (DCP-OVM-sIgE/IC50) and DCP-OVM-sIgE/sIgG4 were compared between the negative and positive groups (p<0.01). Among them, the variable with greatest area under the receiver operating characteristic curve was DCP-OVM-sIgE/IC50 (0.84), followed by DCP-OVM-sIgE/sIgG4 (0.81). DCP-OVM-sIgE/IC50 and DCP-OVM-sIgE/sIgG4 are potentially useful markers for the prediction of positive OFC during HE-SS-OIT and may allow proper evaluation of the current allergic status in the healing process during HE-SS-OIT

Although the existing paradigm states that CMV reactivation is under control of cellular immune response, the role of humoral counterpart is underestimated. Anti-CMV positive woman after conditioning with Bu-Flu-ATG underwent stem cell transplantation from fully matched, seronegative sibling donor. In immunodeficient recipient fast and significant decrease of specific immune response was observed but reconstitution of marrow-derived B and NK cells was prior thymic origin T cells. The lowest CMV-IgG(89 U/ml) was observed just before CMV viremia. Noteworthy, the sole and exclusive factor of CMV-specific immune response is a residual recipient antibody class IgG. The CMV-quantiferon increase was observed later, but in the first phase immune reconstitution of the PHA-induced IFNγ release was significantly lower than that CMV-induced. It corresponds with NK cells increase at the top of lymphocyte reconstitution and undetected CMV-specific CD8 cells by pentamer technique. Most of NK cells are CD16+, thus are stimulated by residual IgG. In immunocompetent donor the cellular and humoral immune response increases in parallel manner but symptoms of CMV mononucleosis were observed till the increase of specific IgG. Our observations shed light on a unique host-CMV interaction: indicate that significant decrease of CMV-IgG is a good predictor for CMV reactivation during secondary immunodeficiency.