Vaccines for Foot and Mouth Disease Virus (FMDV)
Foot and mouth disease (FMD) is a serious disease caused by Aphthovirus. The primary control measure of the disease has been the slaughter of FMDV - infected animals. Chemotherapeutic way of FMD control is vaccination. Vaccines are produced by inactivation of virus grown in bovine tongue epithelium. A detailed study of FMDV reveals that it contains a single stranded RNA covered in a capsid of four polypeptides, for example, VP1, VP2, VP3 and VP4 where only VP1 has a little immunogenic activity. However, the nucleotide sequence encoding for VP1 was identified on the single stranded RNA genome and cloned on double stranded pBR322 in E. coli. About 1,000 molecules of VP1 per bacterial cell were synthesized (Kupper et al, 1981).
Vaccines produced from genetically engineered E. coli cells cannot compete with those extracted from virus particle. Therefore, much more work is to be done to make the vaccines available for FMDV on a large scale at low price. An outline for production of FMD vaccine is given in Fig. 5.6.
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Fig. 5.6. Recombinant DNA technology for making foot and mouth disease vaccine |
Synthetic peptides have also been produced and used for immunization against bacterial (Diphtheria, Streptococcus pyogenes) and viral (Hepatitis virus, FMDV) diseases. For the production of synthetic polypeptide to be used as vaccines, it is necessary to have the knowledge of structure and function of proteins and the regions involved in immunogenic response. For example, synthetic polypeptides having immunogenic affects against HBV contain disulphide bond in the region between amino acids 117 and 137 corresponding to the viral surface antigen. After injection into mice the polypeptides elicited antibodies against HBsAg and protected half of mice.
Similarly, a synthetic polypeptide has been identified that corresponds several regions of FMDV protein VP1. The region between amino acids 141 and 160 elicited and production of antibodies against FMDV in guinea pigs, rabbits and swine. Likewise, another polypeptide was synthesized and the region between amino acids 200 to 213 also VPI also elicited antibodies against FMDV. There are other examples also for the synthesis of vaccines against viral diseases; such vaccines too have a great promise for the immunization purposes. |
