Effect of recurrent invasive pneumococcal disease on serum anti-pneumolysin IgG titres in HIV infected adults

Abstract

We measured serum anti-pneumolysin IgG concentrations in a prospective cohort of 34 HIV infected adults who developed recurrent pneumococcal bacteraemia, and compared baseline levels with HIV positive and HIV negative control subjects that remained free of pneumococcal disease. Anti-pneumolysin concentrations in HIV positive cases and controls were higher compared to HIV negative controls. There was no significant difference in levels between HIV positive subjects who did and did not subsequently develop pneumococcal bacteraemia (geometric means 849.1 U/ml vs. 564.6 U/ml, p=0.059). Anti-pneumolysin IgG titres before, and after the recurrent episode of pneumococcal bacteraemia did not differ significantly (p=0.95). High levels of anti-pneumolysin IgG do not predict protection from invasive pneumococcal disease or indicate that an effective immune response has occurred in HIV infected patients.

Fig. 1

Baseline serum IgG antibodies to pneumolysin in HIV positive cases with recurrent pneumococcal bacteraemia (n = 34) matched HIV positive controls (n = 34) and matched HIV negative controls (n = 34) displayed as box-and-whisker plots. The circle represents an outlier (value between 1.5 and 3 interquartile ranges from the end of the box), asterisks are extreme outliers (>3 interquartile range from box). HIV positive cases and HIV positive controls had significantly higher IgG titres than HIV negative controls. There was no significant difference in levels between cases and HIV positive controls (p = 0.059).

Fig. 2

Profile plot of change in specific IgG titres against pneumolysin before (baseline) and after the recurrent pneumococcal bacteraemia episode in the 29 cases with paired titres.