COMPLEMENT-MEDIATED LYSIS AND INFECTIVITY FOR MOUSE MACROPHAGES AND SANDFLIES OF VIRULENT AND ATTENUATED LEISHMANIA-MAJOR PROMASTIGOTES VARYING IN EXPRESSION OF THE MAJOR SURFACE PROTEASE AND LIPOPHOSPHOGLYCAN

The infectivity to mouse macrophages and sandflies, the expression and enzymatic activity of the major surface glycoprotein (gp63), the deve lopmental modification of lipophosphoglycan (LPG) and three metacyclog enesis markers (promastigote body size, lectin agglutination and compl ement resistance) were compared in four related Leishmania major proma stigote lines. The lines, which differed in their virulence for BALB/c mice, were examined in both logarithmic and stationary phase. Althoug h the two non-virulent lines were unable to survive and multiply withi n the macrophages, they were better at attaching to the macrophages an d infecting sandflies than the two virulent lines, which were highly i nfective for macrophages. Except for the higher resistance of the atte nuated parasites to complement-mediated lysis, there were no clear dif ferences between the metacyclogenesis markers of the four lines. The a mount and enzymatic activity of surface gp63 was relatively high in th e attenuated promastigotes and this appears to be related to a higher expression of gp63 genes. In terms of LPG, cells of all the lines had approximately twice the number of galactose and mannose residues per m olecule when in logarithmic phase than when in stationary phase. LPG o f the virulent lines also contained approximately twice the mannose an d galactose residues of the attenuated line. although L. major gp63 co uld therefore be important for promastigote survival in the sandfly an d for the resistance to complement-mediated lysis, there was no appare nt correlation between gp63 expression and promastigote survival in th e macrophage. A very elongated LPG could be necessary for the survival and proliferation of the parasite in macrophages.