Study of the surface glycoprotein of Rift Valley fever virus using monoclonal antibodies
Date
2016-07-20
Authors
Besselaar, Terry Gail
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Abstract
The structural, functional and antigenic properties of the envelope glycoproteins
of Rift Valley fever virus (RVFV) were analyzed using a panel of monoclonal
antibodies (MAbs). In order to gain a better understanding of the role of the
RVFV surface proteins in infection and pathogenesis, the mechanisms ofanti:~odymediated
neutralization of the virus were examined, as well as the fl}action of the
glycoproteins in viral attachment and penetration.
Of the twenty three MAbs which were generated, fourteen were directed against
the G1 and nine against the G2 protein of RVFV. The topological relationship
of the antigenic determinants to each other on the viral glycoproteins was achieved
using competitive binding assays with enzyme-labelled MAbs. For the RVFV 01
protein, four antigenic domains which may be interlinked were identified. The
domains G1 I, II and IV were involved in virus neutralization and
haemagglutination, while G1 III was associated with low level C'-dependent
neutralization.
With regard to the G2 protein, four antigenic domains which appear to be
spatially distinct were identified. Domain G2 I exhibited significant neutralizing
and haemagglutination activity, while G2 II was involved in haernagglutination
and weak C(-dependent neutralization. The remaining 02 regions neutralized to
a low level only in the presence of C'. The majority of the epitopes on bath viral
glycoproteins were highly conformational, indicating that the native protein
structure is necessary for the recognition and expression of the functional
activities of these particular antibodies.
Protective determinants were shown to occur on both Gland 02, demonstrating
that both RVFV envelope proteins are important in viral pathogenesis. The
neutralization studies, in turn, revealed that the inhibition of virus attachment is
not the principal means of antibody-mediated neutralization of RVFV. Instead,
such ..ieutralization appears to be the result of several different processes,
including synergistic neutralization by combinations of different antibodies,
prevention of virus binding, virus internalization and the blocking of the viral life
cycle at an intracellular stage. Further insight into RVFV infectivity was obtained
by showing that both glycoproteins are involved in virus entry into the host cell.
Finally, the present. findings strongly support an endosomal route of entry and
penetration for RVFV, associated with concomitant allosteric changes in the 01
protein.
Description
A thesis submitted to the Faculty of Medicine
University of the Witwatersrand, Johannesburg
for the De +ee of Doctor of Philosophy
Johannesburg, 1992