Date of Award
Master of Science
The mRNA for GP46, an abundant surface glycoprotein of most Leishmania spp., is expressed at high levels only in infectious Leishmania chagasi promastigotes. To investigate a possible role for GP46 in infectivity we analyzed the relationship between GP46 and resistance to complement-mediated lysis (CML). L. chagasi promastigotes passed for 2-3 weeks in culture were about 9-times more resistant to CML (in the presence of 25 and 50% human serum) when in stationary phase of growth than in logarithmic phase of growth. Cells passed for>100 weeks were extremely sensitive to CML regardless of the phase of growth. GP46 expression levels paralleled CML resistance phenotype: low to non-detectable in higher passage cells (cells passed for 15-18 weeks, or for>100 weeks) and in low passage cells in logarithmic growth phase. Earlier studies with L. chagasi reported the identification of GP46A and GP46B coding sequences, and these varied mainly in the number of leucine rich repeats found in the amino-terminal half of the predicted protein sequences. GP46A and GP46B were re-expressed in higher passage cells transformed with pX[beta]GAL2 plasmids that contained GP46 coding sequence in place of [beta]-galactosidase coding sequence. These higher passage cells were significantly more resistant to CML (p<0.01 when incubated with 25 and 50% serum) as compared to control cells transfected with the unmodified pX[beta]GAL2 plasmid: at 50% serum, about 80% versus 20% survival in the controls. Levels of CML resistance in the GP46-expressing higher passage cells approached that seen in low passage stationary phase cells. The data support a role for GP46 in evasion of lysis by complement.
Leslie Maree Lincoln
Lincoln, Leslie Maree, "Leishmania chagasi surface glycoprotein GP46 functions in parasite resistance to lysis by complement" (2002). Retrospective Theses and Dissertations. 17561.