3.2 The GD/104 virus exhibits low antigenic cross-reactivity
with antibodies against GX/18 virus.
The representative viruses in group A and B, GX/18 and GD/104, were used
as models to explore the genetic basis for antigenic drift of EA H1N1
SIVs. To further investigate their antigenic relationship, ferret, and
guinea pig antisera against the two viruses and a monoclonal antibody
(mAb), named mAb102-95, targeted to the HA protein of GX/18 virus, were
successfully generated. Additionally, four viruses, designated rGX/18,
rGD/104, rGX/18-GDHA and rGD/104-GXHA, were rescued to evaluate the
cross-reactivity with these antibodies.
As shown in Table 2, the antisera against GX/18 reacted well with rGX/18
and rGD/104-GXHA viruses (titers 1:1,280 to 1:2,560) but poorly with
rGD/104 and rGX/18-GDHA viruses (titers 1:40 to 1:80). Similarly, the
antisera against GD/104 reacted well rGD/104 and rGX/18-GDHA viruses
(titers 1:1,280 to 1:2,560) but poorly with rGX/18 and rGD/104-GXHA
viruses (titers 1:80 to 1:160). Moreover, the reactive titers of rGX/18
and rGD/104-GXHA viruses with the mAb102-95 were high up to 1:5,120,
which was 32-fold higher than those of rGD/104 and rGX/18-GDHA viruses
with mAb102-95. Since the significantly different reactivity of rGX/18
and rGD/104 with mAb102-95, the critical antigenic amino acid was
explored by use of mAb102-95 in the following study.