Page 10 - VHSA - Onderstepoort 100 Years - Part 3

OND
ERSTEPOORT 100
tion were consequently restructured into two components: the diagnostic part was incorporated into an institute-wide Diagnostic Programme, whereas the research activities were coordinated in a Bacterial Vaccine Development Programme. The result of this restructuring was gratify-
in 1994/95 the same technique was applied by Sharon de Wet to Salmonella dublin in an attempt to develop a bivalent vaccine. At the same time Botha made the first attempts to clone the toxin encoding genes of Clostridium perfringens
ing. Within a year there was an increase of 37% in the number of specimens submitted for bacteriological diagnoses. This was not only the result of active marketing but also of public concern about the possible contamination of eggs with Salmonella enteritidis, similar to that of a reported outbreak in the UK, and about a limited outbreak of Johne’s disease in sheep in the then Eastern Transvaal (now Mpumalanga).
“Significant progress was also made in the development of in vitro tests such as western blots to replace the animal tests previously used for the typing of clostridial antigens.”
using DNA recombinant techniques. He was successful in cloning the gene for the type D epsilon toxin in E. coli but unfortunately the yield of toxin was too low for practical application. In the case of C. botulinum, cloning of the gene coding for the H- chain of the type C neurotoxin was also achieved.
Significant progress was also made in the development of in vitro tests such as western blots to replace the animal tests previously used for the typing of clostridial antigens. Contracted by the vaccine facto- ry, now called Onderstepoort Biological
A new manager for the vaccine deve-
lopment programme was appointed in the
person of M. (Mike) Odendaal. He intro-
duced a totally new approach in terms of the application of molecular techniques with the assistance of newly appointed staff with the necessary experience and training, i.e. A.D. (Adriaan) Botha and C.E. (Christine) Ellis. An early success was the development of a new generation vaccine against calf scours. A mutant of Salmonella typhimurium was developed by means of chemical mutagenesis of a virulent field strain and found to be safe and effective as a vaccine strain for use in calves. It was shown to be attenuated because of the complete loss of the plasmid which codes for virulence and therefore is a stable mutant. It also contained a metabolic marker so that the live vaccine strain, once released in the field, can be accurately detected and distinguished from a mixed population of other bacteria. It was the first time in the world that a Salmonella
100 strain was attenuated by plasmid curing. In a follow-up project
Products (OBP), Odendaal studied the use and evaluation of new adjuvants to replace the traditional oil formulations. He identified a vitamin E-based water miscible agent which is well tolerated by animals and produced high antibody levels against epsilon toxoid when used as adjuvant. He also continued the work on the P. haemolytica leukotoxin vaccine which later turned out to be very successful in the market place. In 1999 Odendaal resigned and was succeeded by Botha. E.E. de Bruyn and E.C. du Plessis were new appointees in the period 1997-1998 and were respectively involved in further work on developing a recombinant lamsiekte vaccine and a lamsiekte challenge model in cattle.
A highlight during this period was the official launching of the Leukopast vaccines against pasteurellosis by the then Minister of Agriculture, Mr. D.A. Hanekom. The two original
Bacterial vaccine production
PART 3
History of Individual Disciplines
1908-2008
Years