GIARDIA-LAMBLIA VARIANT SURFACE PROTEIN H7 STIMULATES A HETEROGENEOUSREPERTOIRE OF ANTIBODIES DISPLAYING DIFFERENTIAL CYTOLOGICAL EFFECTS ON THE PARASITE
S. Stager et al., GIARDIA-LAMBLIA VARIANT SURFACE PROTEIN H7 STIMULATES A HETEROGENEOUSREPERTOIRE OF ANTIBODIES DISPLAYING DIFFERENTIAL CYTOLOGICAL EFFECTS ON THE PARASITE, Molecular and biochemical parasitology, 85(1), 1997, pp. 113-124
Previous investigations had shown that the Giardia lamblia clone GS/M-
83-H7-specific variant surface protein (VSP) H7 consists of at least t
wo antigenically distinct parts: (i) a variable 314-aa N-terminal regi
on which contains one, or more, variant-specific epitopes eliciting a
transient and consequently low-level antibody response preferentially
detectable during the early phase of a G. lamblia infection in mice; a
nd (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 ind
icated that monoclonal antibody G10/4 and polyclonal antibodies from e
arly-phase infected or hyperimmunized mice, directed against the varia
nt-specific N-terminal region, exclusively recognized conformational c
ysteine-containing epitopes. These antibodies caused detachment and ag
gregation of trophozoites, and exhibited complement-independent cytoto
xic effect towards the parasite. In contrast, polyclonal antibodies fr
om late-phase infected mice, directed against the semi-conserved pepti
dyl structures in the C-terminal region, preferentially reacted with n
on-conformational epitopes. Such antibodies had no cytotoxic effect, b
ut provoked parasite-detachment and -aggregation. These findings indic
ated that infection of mice with G. lamblia clone GS/M-83-H7 generates
a heterogeneous repertoire of cytologically active anti-VSP H7 antibo
dies which may have a direct influence on the course of the parasite i
nfection. (C) 1997 Elsevier Science B.V.