THE LIPIDS OF PNEUMOCYSTIS-CARINII

Information about a number of Pneumocystis carinii lipids obtained by the analyses of organisms isolated and purified from infected lungs of corticosteroid-immunosuppressed rats has been reported in recent year s. Of the common opportunistic protists associated with AIDS (Cryptosp oridium, Toxoplasma, and the microsporidia), more is currently known a bout the lipids of P. carinii than the others. Lipids that are synthes ized by the organism but not by humans are attractive targets for drug development. thus, the elucidation of Delta(7)C-24-alkylated sterol a nd cis-9,10-epoxystearic acid biosyntheses in P. carinii is currently being examined in detail, since these have been identified as P. carin ii-specific lipids. the development of low-toxicity drugs that prevent sterol C-24 alkylation and the specific inhibition of the lipoxygenas e that forms cis-9,10-epoxystearic acid might prove fruitful. Although humans can synthesize coenzyme Q(10) the anti-P. carinii activity and low toxicity of ubiquinone analogs such as atovaquone suggest that th e electron transport chain in the pathogen may differ importantly from that in the host. Although resistance to atovaquone has been observed , development of other naphthoquinone drugs would provide a broader ar mamentarium of drugs to treat patients.