Foot-and-Mouth Disease Virus (FMDV) induces rearrangements of host-cell
membranes to generate vesicles that are believed to provide platforms for
formation of the viral replication complex. The cellular origin of these vesicles
and the properties that make them favourable for replication are poorly
understood. For some Picornaviruses these vesicles are thought to derive from
membranes of the secretory pathway. In this thesis, I have investigated a role
for membranes of the secretory pathway in FMDV infection. Key cellular
proteins involved in regulating the flow of membranes through the secretory
pathway between the ER and Golgi were inhibited using expression of
dominant-negative (dn) proteins and small interfering RNA (siRNA) and the
effect on FMDV infection determined. Inhibition of ER export using a drug (H89)
or Sar1 (the GTPase required for COPII transport vesicle formation at ER exit
sites) reduced FMDV infection. In contrast, stabilisation of COPII coats, or
inhibition of Arf1 or Rab proteins, that are involved in the secretory pathway
after the formation of COPII vesicles, had little or no inhibitory effect on
infection. Interestingly inhibition of Arf1, Rab1 or Rab2 enhanced infection. In
contrast, Arf1 reduced infection by bovine enterovirus which is inhibited by
Brefeldin-A, and therefore likely to be dependent on Arf1 for replication. These
results show that Sar1 and/or COPII vesicle formation is necessary for FMDV
infection and that inhibiting the formation of COPI coats is in some way
advantageous to FMDV infection. These results suggest that FMDV targets
COPII vesicles membranes before the COPII/COPI exchange and facilitates
FMDV infection and that COPI components are not required.