RICIN-RESISTANT MUTANTS OF LEISHMANIA-MAJOR WHICH EXPRESS MODIFIED LIPOPHOSPHOGLYCAN REMAIN INFECTIVE FOR MICE

Glycosylation variants of the virulent Leishmania major clone V121 wer e generated by mutagenesis with N-methyl-N-nitroso-N-nitroguanidine an d selected using the galactose-specific lectin Ricinus communis II (RC A II). Three mutants, 4B9, 1D1 and 1C12, which failed to bind RCA II, were found to have an altered expression of lipophosphoglycan (LPG), a molecule implicated in the attachment to host macrophages and surviva l within the phagolysosome. There were differences in the antigenicity , molecular weight and localization of LPG from mutant parasites as co mpared to V121. Expression of gp63, a surface molecule also implicated in attachment to macrophages, was unaltered. All 3 mutants caused dis ease when injected into genetically susceptible BALB/c mice but lesion s developed at a much slower rate than those caused by the virulent V1 21 clone. This slow rate of lesion development did not correlate with promastigotes' ability to invade macrophages in vitro. Karyotype analy sis showed that there was a reduction in the size of chromosome band n umber 2 in all 3 mutants. The differences in LPG and chromosome band 2 were retained by mutant clones following passage through mice, sugges ting that these phenotypes are stable. Although the mutant parasites w ere infective and caused lesions, the changed structure of the LPG app eared to influence the virulence of the parasites.