Capsid intermediates assembled in a foot-and-mouth disease virus genome RNA-programmed cell-free translation system and in infected cells

Abstract

Structural protein complexes sedimenting at 140S, 70S (empty capsids), and 14S were isolated from foot-and-mouth disease virus-infected cells. The empty capsids were stable, while 14S complexes were relatively short-lived. Radioimmune binding assays involving the use of neutralizing monoclonal antibodies to six distinct epitopes on type A12 virus and polyclonal antisera to A12 structural proteins demonstrated that native empty capsids were indistinguishable from virus. Infected cell 14S particles possessed all the neutralizing epitopes and reacted with VP2 antiserum. Cell-free structural protein complexes sedimenting at 110S, 60S, and 14S containing capsid proteins VP0, VP3, and VP, are assembled in a rabbit reticulocyte lysate programmed with foot-and-mouth viral RNA. These structures also contain the six epitopes, and cell-free 14S structures like their in vivo counterparts reacted with VP2 antiserum. Capsid structures from infected cells and the cell-free complexes adsorbed to susceptible cells, and this binding was inhibited, to various degrees, by saturating levels of unlabeled virus. These assays and other biochemical evidence indicate that capsid assembly in the cell-free system resembles viral morphogenesis in infected cells. In addition, epitopes on the virus surface possibly involved in interaction with cellular receptor sites are found early in virion morphogenesis.

Antibody Response in Mice Inoculated with DNA Expressing Foot-and-Mouth Disease Virus Capsid Proteins

“…This study has demonstrated that delivery of an FMDV cDNA construct containing the P1-2A and 3C coding regions as a DNA vaccine results in the assembly of FMDV capsid structures and that these plasmids are capable of inducing a neutralizing antibody response in mice. These results support immunological studies demonstrating the broad serological specificity of cell culture-derived empty capsids (13,18,32) and encourage the continued development of this approach as a potentially viable alternative to inactivated virus vaccines. Introduction of the P1-2A and 3C cassettes directly into animals appears to avoid observed problems of 3C cytotoxicity which have hampered other empty-capsid approaches (see above).…”

“…Noninfectious provirions consist of RNA, VP0, VP1, and VP3, and cleavage of VP0 to VP4 and VP2, by an unknown mechanism, results in conversion of provirions to mature virions (21,33). Immunological studies have identified linear and conformational sites that are present on both empty capsids and virions (13,18,32), and antisera raised against empty capsids have serological specificity which is indistinguishable from that of sera prepared against virions (34).…”

Synthesis of empty capsid-like particles of Asia I foot-and-mouth disease virus in insect cells and their immunogenicity in guinea pigs

“…Studies in immunology have identified the presence of linear and conformational sites present on both empty capsids and virions (Rowlands et al, 1975;Doel and Chong, 1982;Grubman et al, 1985), and antisera raised against empty capsids had serological specificities that were indistinguishable from those of sera prepared against virions (Rweyemamu et al, 1979). All of these results demonstrated that empty capsids of FMDV were similar to virions, and could be used to mimic virions immunologically.…”

Expression, processing, and assembly of foot-and-mouth disease virus capsid structures in heterologous systems: induction of a neutralizing antibody response in guinea pigs

“…Rweyemamu et al (41) have shown that FMDV type A empty capsids (subviral particles lacking nucleic acid) are as immunogenic as virions in guinea pigs and that antisera raised against empty capsids have the same serological specificity in neutralization tests as do sera prepared against virions. By MAb analysis, we have demonstrated that empty virus capsids isolated from infected cells antigenically resemble virus particles (21). Furthermore, we and others have shown that, in a cell-free translation system programmed with FMDV RNA or subgenomic RNA transcripts, viral structural proteins self-assemble into various capsid intermediates (12,18,21).…”