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Co-replication of several isotypes of foot-and-mouth disease virus
D Leister1, K H Adam, O Marquardt
1Bundesforschungsanstalt für Viruskrankheiten der Tiere, Tübingen, Germany.
Abstract:
Genome segments of the foot-and-mouth disease virus isolates O1Lombardy and O3 Venezuela that encode, among other products, capsid protein VP1 were amplified using PCR, and the products were cloned and sequenced. The alignment of up to 11 O3-specific sequences revealed six silent nucleotide changes a well as six changes that cause amino acid substitutions in capsid protein VP1 at positions 45, 83, 141, 145, 170 and 178. The heterogeneity of three O1-specific sequences consisted of seven silent exchanges and amino acid changes at positions 85 and 134 on VP1. Amplification, subclonning and sequencing of cloned O3-specific cDNA was performed to examine the nature of the sequence heterogeneity. As no difference was found among five subcloned sequences, we conclude that the Taq polymerase copied the DNA correctly. The sequence heterogeneity observed with both virus isolates is, therefore, consistent with the quasispecies structure of foot-and-mouth disease virus. Furthermore, amino acid changes at a number of sites have been found to be involved in the formation or modulation of neutralizing epitopes. The novel aspect of this study is the ability to estimate, by cloning of PCR products, the number of virus isotypes, possibly varying in antigenicity, that are able to co-propagate. Seven isotypes of O3 Venezuela were identified. Some are of particular interest because they exhibit a change at VP1 codon 145 that causes the replacement of arginine, possibly essential for virus attachment to cells, by isoleucine.
Insights
This study reveals significant genetic diversity within foot-and-mouth disease virus (FMDV) isolates, identifying multiple co-propagating virus isotypes with potential antigenic variations. These findings highlight the quasispecies nature of FMDV and its implications for vaccine development.
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- Foot-and-mouth disease virus (FMDV) is a highly contagious pathogen with significant economic impact.
- Understanding FMDV genetic diversity is crucial for effective control strategies and vaccine design.
Purpose of the Study:
- To analyze the genetic heterogeneity of FMDV capsid protein VP1 in O1Lombardy and O3 Venezuela isolates.
- To investigate the quasispecies structure and identify co-propagating virus isotypes.
- To assess potential antigenic variations arising from amino acid substitutions in VP1.
Main Methods:
- Polymerase chain reaction (PCR) amplification of FMDV genome segments encoding VP1.
- Cloning and sequencing of PCR products from O1Lombardy and O3 Venezuela isolates.
- Sequence alignment and analysis to identify nucleotide and amino acid variations.
- Subcloning and sequencing to confirm accuracy of PCR amplification.
Main Results:
- Identified significant nucleotide and amino acid substitutions in VP1 of both FMDV isolates.
- Observed sequence heterogeneity consistent with the quasispecies nature of FMDV.
- Estimated and identified seven distinct virus isotypes for the O3 Venezuela isolate.
- Highlighted specific VP1 mutations, including a key change at codon 145 (arginine to isoleucine), potentially affecting cell attachment and antigenicity.
Conclusions:
- The genetic heterogeneity observed supports the quasispecies model for FMDV.
- Amino acid changes in VP1 can influence neutralizing epitopes and potentially virus-host interactions.
- The identification of multiple co-propagating isotypes provides insights into FMDV evolution and antigenic variation.