FIG 7.
Pretreatment of macrophages with 1,25D3 increases GAS survival through an SLO-dependent mechanism. THP-1 macrophages were pretreated with 100 nM 1,25D3 for 24 h prior to infection with GAS. GAS 854, 854csrSTM, 854ΔhasB, 854Δslo, 854ΔcsrR, and 854ΔcsrR/ΔhasB were used for infection; data are presented in separate panels for clarity. Viable GAS released into the cell culture medium plus GAS associated with the macrophages were quantified after 90 min of incubation (time zero) and 2 and 4 h later. For each strain, the number of GAS at each time point, reported as a percentage of the number at time zero, is shown. Data are means and standard errors from at least three separate experiments. *, P < 0.05; **, P < 0.01. NS, not significant.