RT Journal Article T1 Measurement of Typhim Vi IgG as a Diagnostic Tool to Determine Anti-polysaccharide Antibody Production Deficiency in Children A1 Guevara-Hoyer, Kissy et al. A1 Pérez de Diego, Rebeca A1 Gil López, Celia A1 Recio Hoyas, María José A1 Fernández Arquero, Miguel A1 Ramos Amador, José Tomás A1 Sánchez Ramón, Silvia María AB Background: The assessment of specific polysaccharide antibody production plays a pivotal role in the diagnosis of humoral primary immunodeficiencies (PID). The response to 23-valent pneumococcal vaccine (PPV) remains the gold standard for the diagnosis of polysaccharide antibodies. However, in Spain, the interpretation of pure polysaccharide 23-valent immunization is hampered by the high endemicity of pneumococcal disease and the generalization of the 13-valent adjuvant pneumococcal vaccination. Specific Typhim Vi vaccination (TV) immunoglobulin G IgG response to immunization is useful in adult PID, but there is no data regarding children.Objectives: To evaluate the clinical utility of TV IgG production as a diagnostic tool to determine anti-polysaccharide antibody production deficiency in children, when the response to PPV is unclear and isolated determination of serotypes is unfeasible.Methods: We conducted a single-institution prospective observational study on 61 children with recurrent infections. Baseline specific antibodies against PPV and TV were evaluated. In 28 children (46%), the response to the production of antibodies confirmed a clinical suspicion of humoral PID, and they were therefore immunized with 23-valent pneumococcal vaccine and Typhim Vi. Both specific antibody responses were measured by ELISA (The Binding Site Group Ltd, Birmingham, UK) using previously published cut-offs.Results: Seventy percent of the 61 children displayed baseline PPV IgG > 27 mg/L, whereas only 8% showed TV IgG > 28 U/mL (p < 0.0001). Twenty-one of 28 children (75%) achieved a 3-fold increase in post-vaccination TV IgG levels, whereas only 3% achieved a 4-fold increase in PPV IgG post vaccination, mainly due to high baseline PPV IgG titers. When we classified children according to their response to TV as responders or non-responders and compared this with the well-known clinical warning signs of the Jeffrey Modell Foundation. The proportions of children with history of pneumonia and the need for intravenous antibiotics were significantly higher in TV IgG non-responders than in TV IgG responders (p = 0.02 and p = 0.01, respectively).Conclusion: Response to TV can be considered an ancillary diagnostic tool to determine polysaccharide antibodies in children, particularly when isolated determination of pneumococcal serotypes is not feasible. TV provides a useful asset for clinicians in the era of conjugate PPV vaccination, with clinical relevance. Further research is warranted for validation. PB Frontiers Media S.A SN 1664-3224 YR 2019 FD 2019-04-02 LK https://hdl.handle.net/20.500.14352/92632 UL https://hdl.handle.net/20.500.14352/92632 LA eng NO Guevara-Hoyer K, Gil C, Parker AR, Williams LJ, Orte C, Rodriguez de la Peña A, Ochoa-Grullón J, Rodriguez De Frias E, García IS, García-Gómez S, Recio MJ, Fernández-Arquero M, Pérez de Diego R, Ramos JT, Sánchez-Ramón S. Front Immunol. 2019 Apr 2;10:654. DS Docta Complutense RD 20 ago 2024