Multicenter Study for the Evaluation of the Antibody Response against Salmonella Typhi Vi Vaccination (EMPATHY) for the Diagnosis of Anti-Polysaccharide Antibody Production Deficiency in Patients with Primary Immunodeficiency

Abstract Evaluation of specific antibody (Ab) response to polysaccharide antigens is essential for diagnosis of primary immunodeficiencies. We assessed the specific Ab responses to the pneumococcal-polysaccharide (PPV) and to Salmonella typhi-polysaccharide (TyphimVi) vaccines in a prospective study (EMPATHY) in patients with common variable immunodeficiency (CVID-Group, n = 22), hypogammaglobulinemia (HYPOG-Group; n = 27) and healthy controls (HC-Group; n = 16). Specific Ab concentrations in response to PPV and to TyphimVi vaccines were measured by ELISA (The Binding Site, UK), defining 3-fold increase as normal response (Ratio:3x). The RatioTyphimVi:3x was significantly greater in HC than in CVID-Group (p < 0.0001), but not than HYPOG-Group (p = 0.138). However, the RatioPPV:3x showed no significant differences among the three groups. By ROC analysis, TyphimVi better differentiated HC from CVID (AUC:0.893, IC95%: 0.791-0.996, p < 0.0001) than PPV. Our results suggest that the use of specific Ab response to TyphimVi could represent a complementary assay for the diagnosis of anti-polysaccharide Ab production deficiency in patients with CVID.