Foot-and-mouth-disease virus protein Structural proteins Non-structural proteins

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Introduction

Foot-and-mouth disease virus (FMDV) was identified by Loeffler and Frosch in 1898 as the first filtrable viral agent to cause animal disease. It is a highly contagious virus affecting over 60 species of cloven-hoofed domestic and wild animals (Hedger, 1981). The disease has a high morbidity and mortality is rare in adult animals, however myocarditis may occur in young animals resulting in death. The recovered animals remain in poor physical condition over long periods of time leading to sustained economic losses for the livestock industry.

Picornaviridae family

Viruses which are insensitive to ether, chloroform, non-ionic detergents and which have viral ribonucleic acid (RNA) functioning as messenger RNA or as template for progeny RNA are classified as members of the picornavirus family (Melnick et al., 1975). Viruses within this family cause diseases of medical and agricultural importance, e.g. poliovirus, common cold virus, human hepatitis A virus and FMDV. The family consists of 20 virus species divided into nine genera and is summarized in Table 1.1.

Morphology & biophysical characteristics of foot-and-mouth disease virus

The name picornavirus comes from the word “pico” which means very small and “rna” for the genome type. They are among the smallest known RNA viruses and have a naked, ether-resistant, icosahedral protein shell with a symmetry of 22-30 nm in diameter (Melnick et al., 1975; Cooper et al., 1978).

Structural proteins

The P1-2A gene product is the precursor of the capsid proteins 1A, 1B, 1C, and 1D named viral proteins 1-4 (VP4, VP2, VP3, and VP1), while P2 and P3 are precursors to non-structural proteins (Fig. 1.1b) (Brown, 1976; Ryan et al., 1989; Belsham, 1993). The genome segment P2 encodes for proteins 2B, 2C and 2A. While, the P3 region is a precursor of 3A, 3B, 3C and 3D. The protein 3C is the major protease and 3D is the RNA-dependent RNA polymerase or RNA replicase gene (Caliguiri, 1974).

Acknowledgments
CHAPTER 1 Literature review
1.1 Introduction
1.2 Picornaviridae family
1.3 Properties of foot-and-mouth-disease virus
1.3.1 Morphology & Biophysical characteristics of FMDV
1.3.2 Genome structure
1.3.3 Foot-and-mouth-disease virus protein Structural proteins Non-structural proteins
1.4 Properties and functions of the VP1 protein
1.4.1 Importance of VP1 in the antigenicity of FMDV
1.4.2 Importance of VP1 protein in virus-cell attachment
1.5 Antigenic variation
1.5.1 Mutation
1.5.2 Recombination
1.5.3 Quasi-species concept
1.6 Virus replication
1.7 Epidemiology
1.7.1 Distribution of FMD serotypes
1.8 Foot and mouth disease
1.8.1 Clinical symptoms
1.8.2 Pathology
1.8.3 Susceptible host range
1.8.4 Carrier animals
1.8.5 Transmission
1.8.6 Socio-economical impact of the disease
1.9 Control of FMD
1.9.1 Vaccines & vaccination
1.9.2 Control strategy in endemic & disease free zones
1.9.3 Immune response
1.10 Diagnosis of foot-and-mouth-disease
1.10.1 Antigen detection tests
Specimens for antigen detection
Virus isolation
Complement fixation test
Enzyme-linked immunosorbent assays (ELISA)
Sandwich ELISA
Polymerase chain reaction-PCR
Polyacrylamide gel electrophoresis
1.10.2 Antibody detection tests Virus neutralization test Liquid phase blocking ELISA
2.3.5 Complementary DNA synthesis-cDNA
2.3.6 Polymerase chain reaction
2.3.7 Gel electrophoresis and purification of amplified DNA
2.3.8 Nucleotide sequencing
2.3.9 Data analysis
2.4 Results
2.4.1 VP1 gene relationships
2.4.2 Sequence variation & determination of the geographical origin of type O outbreaks (1988-1993) in West Africa
2.5 Discussion
CHAPTER 3 Molecular epidemiological study of SAT-2 type foot-and-mouth-disease virus recovered from outbreaks in West Africa (1974-1991)
3.1 Summary
3.2 Introduction
3.3 Materials and methods
3.3.1 Viruses used in the study
3.3.2 Cell cultures, RNA extraction & cDNA synthesis
3.3.3 PCR amplification and DNA purification
3.3.4 Sequencing and data analysis
3.4 Results
3.4.1 VP1 sequence analysis
3.4.2 Amino acid variation
3.5 Discussion 64
CHAPTER 4 Retrospective genetic analysis of SAT-1 type foot-and-mouth-disease outbreaks in West Africa (1975-1981)
4.1 Summary
4.2 Introduction
4.3 Materials and methods
4.3.1 Viruses used in the study
4.3.2 Reverse transcriptase, PCR, nucleotide sequencing & data analysis
4.4 Results
4.5 Discussion
CHAPTER 5
5.1 Summary and conclusions