C3b/iC3b deposition on Streptococcus pneumoniae is not affected by HIV infection

Abstract

Streptococcus pneumoniae is a common cause of infection in both HIV positive patients and those with complement deficiencies. We hypothesised that HIV positive individuals might exhibit reduced opsonisation of pneumococcus with complement due to reduced levels of S. pneumoniae specific IgG. We discovered no difference in C3 deposition on S. pneumoniae between HIV positive or negative individuals, and furthermore C3 deposition remained unchanged as HIV progressed towards AIDS. We found no correlation between C3 deposition on S. pneumoniae and CD4 cell count in HIV infected individuals. Hence we have demonstrated no failure of complement immunity in HIV positive patients.

Figure 1. The effect of HIV infection on C3b/iC3b deposition on Streptococcus pneumoniae.

(A) Fluorescent Index (FI) of C3b/iC3b deposition on D39 S. pneumoniae incubated in 20% human serum from HIV positive (open bars, n = 23) or negative individuals (slashed bars, n = 15), P = 0.037 Mann-Whitney U test. (B). FI of C3b/iC3b deposition on D39 incubated in 20% serum from HIV positive (open bars) or negative (slashed bars) individuals over time. Samples 1, 2 and 3 were collected sequentially from individuals. ANOVA P = 0.42) (C) C3b/iC3b deposition on D39 from HIV positive individuals was plotted against the CD4 cell count for that individual, Pearson's correlation co-efficient P = 0.382 R² = 0.029).