TY - JOUR

T1 - Viral RNA modulates the acid sensitivity of foot-and-mouth disease virus capsids

AU - Curry, Stephen

AU - Abrams, Charles C.

AU - Fry, Elizabeth

AU - Crowther, John C.

AU - Belsham, Graham J.

AU - Stuart, David I.

AU - King, Andrew M.Q.

PY - 1995/1

Y1 - 1995/1

N2 - Foot-and-mouth disease virus (FMDV) manifest an extreme sensitivity to acid, which is thought to be important for entry of the RNA genome into the cell. We have compared the low-pH-induced disassembly in vitro of virions and natural empty capsids of three subtypes of serotype A FMDV by enzyme-linked immunosorbent assay and sucrose gradient sedimentation analysis. For all three subtypes (A22 Iraq 24/64, A1061, and A24 Cruzeiro), the empty capsid was more stable by 0.5 pH unit on average than the corresponding virion. Unexpectedly, in the natural empty capsids used in this study, the precursor capsid protein VP0 was found largely to be cleaved into VP2 and VP4. For picornaviruses the processing of VP0 is closely associated with encapsidation of viral RNA, which is considered likely to play a catalytic role in the cleavage. Investigation of the cleavage of VP0 in natural empty capsids failed to implicate the viral RNA. However, it remains possible that these particles arise from abortive attempts to encapsidate RNA. Empty capsids expressed from a vaccinia virus recombinant showed essentially the same acid lability as natural empty capsids, despite differing considerably in the extent of VP0 processing, with the synthetic particles containing almost exclusively uncleaved VP0. These results indicate that it is the viral RNA that modulates acid lability in FMDV. In all cases the capsids dissociate at low pH directly into pentameric subunits. Comparison of the three viruses indicates that FMDV A22 Iraq is about 0.5 pH unit more sensitive to low pH than types A1061 and A24 Cruzeiro. Sequence analysis of the three subtypes identified several differences at the interface between pentamers and highlighted a His-α-helix dipole interaction which spans the pentamer interface and appears likely to influence the acid lability of the virus.

AB - Foot-and-mouth disease virus (FMDV) manifest an extreme sensitivity to acid, which is thought to be important for entry of the RNA genome into the cell. We have compared the low-pH-induced disassembly in vitro of virions and natural empty capsids of three subtypes of serotype A FMDV by enzyme-linked immunosorbent assay and sucrose gradient sedimentation analysis. For all three subtypes (A22 Iraq 24/64, A1061, and A24 Cruzeiro), the empty capsid was more stable by 0.5 pH unit on average than the corresponding virion. Unexpectedly, in the natural empty capsids used in this study, the precursor capsid protein VP0 was found largely to be cleaved into VP2 and VP4. For picornaviruses the processing of VP0 is closely associated with encapsidation of viral RNA, which is considered likely to play a catalytic role in the cleavage. Investigation of the cleavage of VP0 in natural empty capsids failed to implicate the viral RNA. However, it remains possible that these particles arise from abortive attempts to encapsidate RNA. Empty capsids expressed from a vaccinia virus recombinant showed essentially the same acid lability as natural empty capsids, despite differing considerably in the extent of VP0 processing, with the synthetic particles containing almost exclusively uncleaved VP0. These results indicate that it is the viral RNA that modulates acid lability in FMDV. In all cases the capsids dissociate at low pH directly into pentameric subunits. Comparison of the three viruses indicates that FMDV A22 Iraq is about 0.5 pH unit more sensitive to low pH than types A1061 and A24 Cruzeiro. Sequence analysis of the three subtypes identified several differences at the interface between pentamers and highlighted a His-α-helix dipole interaction which spans the pentamer interface and appears likely to influence the acid lability of the virus.

UR - http://www.scopus.com/inward/record.url?scp=0028917761&partnerID=8YFLogxK

U2 - 10.1128/jvi.69.1.430-438.1995

DO - 10.1128/jvi.69.1.430-438.1995

M3 - Journal article

C2 - 7983739

AN - SCOPUS:0028917761

VL - 69

SP - 430

EP - 438

JO - Journal of Virology

JF - Journal of Virology

SN - 0022-538X

IS - 1

ER -