Giardia lamblia variant surface protein H7 stimulates a heterogeneous repertoire of antibodies displaying differential cytological effects on the parasite.
Previous investigations had shown that the Giardia lamblia clone GS/M-83-H7-specific variant surface protein (VSP) H7 consists of at least two antigenically distinct parts: (i) a variable 314-aa N-terminal region which contains one, or more, variant-specific epitopes eliciting a transient and consequently low-level antibody response preferentially detectable during the early phase of G. lamblia infection in mice; and (ii) a 171-aa C-terminal region which contains relatively conserved epitope(s) causing a persistent and consequently high-level antibody response during the later phase of an infection. The present study indicated that monoclonal antibody G10/4 and polyclonal antibodies from early-phase infected or hyperimmunized mice, directed against the variant-specific N-terminal regional exclusively recognized conformational cysteine-containing epitopes. These antibodies caused detachment and aggregation of trophozoites, and exhibited complement-independent cytotoxic effect towards the parasite. In contrast, polyclonal antibodies from late-phase infected mice, directed against the semi-conserved peptidyl structures in the C-terminal region, preferentially reacted with non-conformational epitopes. Such antibodies had no cytotoxic effect, but provoked parasite-detachment and -aggregation. These findings indicated that infection of mice with G. lamblia clone GS/M-83-H7 generates a heterogeneous repertoire of cytologically active anti-VSP antibodies which may have a direct influence on the course of the parasite infection.
Stäger
S
S
Institute of Parasitology, Berne, Switzerland.
Felleisen
R
R
Gottstein
B
B
Müller
N
N
D000818:Animals; D000913:Antibodies, Protozoan / Q000096:biosynthesis / Q000276:immunology*; D000940:Antigenic Variation; D000953:Antigens, Protozoan / Q000276:immunology*; D000954:Antigens, Surface / Q000276:immunology*; D001665:Binding Sites; D003602:Cytotoxicity, Immunologic; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes; D005260:Female; D016829:Giardia lamblia / Q000276:immunology*; D005873:Giardiasis / Q000276:immunology; D007132:Immunoglobulin Isotypes; D051379:Mice; D015800:Protozoan Proteins; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000276:immunology
D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D000954:Antigens, Surface; D000939:Epitopes; D007132:Immunoglobulin Isotypes; D015800:Protozoan Proteins; D011994:Recombinant Proteins; C072464:variant surface protein H7, Giardia lamblia