Measurement and interpretation of Salmonella typhi Vi IgG antibodies for the assessment of adaptive immunity

Response to polysaccharide vaccination can be an invaluable tool for assessing functionality of the adaptive immune system. Measurement of antibodies raised in response to Pneumovax®23 is the current gold standard test, but there are significant challenges and constraints in both the measurement and interpretation of the response. An alternative polysaccharide vaccine approach (Salmonella typhi Vi capsule (ViCPS)) has been suggested. In the present article, we review current evidence for the measurement of ViCPS antibodies in the diagnosis of primary and secondary antibody deficiencies. In particular, we review emerging data suggesting their interpretation in combination with the response to Pneumovax®23 and comment upon the utility of these vaccines to assess humoral immune responses while receiving immunoglobulin replacement therapy (IGRT).