FIG 7.

P. carinii cell wall preparations incorporate β-1,6 glucans, which can be inhibited by the β-1,6 glucan synthase inhibitors D75-4590 and compound 16b. To assess whether P. carinii actively incorporates UDP-glucose into insoluble β-1,6-containing carbohydrates, P. carinii organisms were purified and cell wall preparations were generated and reacted with UDPG as described in Materials and Methods. The resulting derived β-1,6 glucans were assayed by IEIA. The assays were conducted in the presence of either DMSO diluent alone (positive control) or D75-4590 or compound 16b (0.06 μg/ml each in DMSO diluent), which are agents that specifically inhibit β-1,6 glucan synthase-type proteins. The negative control was P. carinii cell wall preparations alone, without UDPG substrate, which represents the basal β-1,6 glucans already present in these preparations. The positive control was P. carinii cell wall preparations incubated in reaction mixtures containing both UDPG and DMSO diluent. Both D75-4590 and compound 16b significantly inhibited the generation of new P. carinii β-1,6 glucan compared to positive-control reaction mixtures. Shown are data derived from three experimental runs, each performed in duplicate. *, P < 0.05, contrasting β-1,6 glucan generated in the presence of UPDG and DMSO diluent alone but with no inhibitor (positive control) and reactions performed with UPDG with inhibitor diluted in DMSO. The data are expressed as means and SEM derived from multiple experimental runs.