Measurement of pneumococcal IgA and IgM responses may identify antibody-deficient patients who are most at risk of infection. Here we measured the specific IgA and IgM response to Prevnar13® (PCV13) and Pneumovax®23 (PPV23).
Pneumococcal responses were measured using the VaccZyme™ pneumococcal capsular polysaccharide (PCP) IgA and IgM ELISAs (The Binding Site Group Ltd, Birmingham, UK) in control (median 59 years, range 16-86) and antibody-deficient (median 66 years, 44-86) patients recruited from the Immunodeficiency Unit at the Birmingham Heartlands Hospital, UK. Patients were vaccinated with either PCV13 (n=16 control, 10 antibody-deficient) or PPV23 (n=31 control, 18 antibody-deficient) and serum samples collected pre- and 4 weeks post-vaccination.
PCP-Ig responders (+) and non-responders (-) were defined from the lower 95th percentile range of the control population (for PPV23, PCP-IgA: 0.49U/mL and PCP-IgM: 24.6U/mL; for PCV13, PCP-IgA: 6.0U/mL and PCP-IgM: 6.4U/mL). For the PPV23 group, 6% were PCP-IgA-/IgM-, 44% were PCP-IgA+/IgM+ and 50% were PCP-IgA+IgM-. For PCV13, 40% were PCP-IgA-/IgM+ and 60% were PCP-IgA+/IgM+. For PPV23, significant positive correlation was observed between PCP-IgA and PCP-IgM (Spearman r=0.68, p=0.002). However, PCP-IgA-/IgM+ and PCP-IgA-/IgM- patients were associated with a more severe phenotype requiring IVIG replacement therapy (56%) compared to PCP-IgA+/IgM+ patients (44%). For PCV13, no significant difference in infection frequency and severity was observed between PCP-IgA-/IgM+ and PCP-IgA+/IgM+ patients.
The measurement of PCP-IgA and PCP-IgM potentially stratifies the patient cohort and provides further information to the clinician.