Page 123 - VHSA - Onderstepoort 100 Years - Part 3

ONDERSTEPOORT 100
URESEARCH ON HEARTWATER
ntil the 1970s heartwater (HW) was dealt with in the Virology Section. Up to the early 1960s heartwater-infective blood which was used as a ‘vaccine’ was produced by staff of the Virology Section. Thereafter this activity became part of the centralized vaccine production unit headed by van Rooyen.
Since the 1930s attempts have been made to cultivate the causal agent, Ehrlichia ruminantium, particularly with the objective of attenuation. Serial passage through sheep and isolation attempts in ferrets, mice, embryonated eggs and mammalian cell cultures consistently yielded negative results. Erasmus (1969) conceived the idea of cultivating the organism in bovine endothelial cells (see figures below). With the able assistance of Pieterse they succeeded
in growing calf foetal endothelial cells in vitro (the E5 endothelial cell line). The cells were obtained by passing trypsin-versene through the umbilical blood vessels of a bovine foetus. The fifth rinse contained pure endothelial cells (E5) whereas subsequent rinses contained fibroblasts which in subsequent cell passages overgrew the endothelial cells.
Erasmus and Pieterse managed to maintain the HW organisms in the E5 cultures for 14 days (two cell passages) but not for longer periods. In 1970 the HW research was terminated due to the pressure of Chlamydia diagnostic work. The E5 cells proved very susceptible to Chlamydia,
particularly once the cells were gamma-irradiated. In 1984, using gamma-irradiated E5 cells, J.D. Bezuidenhout,
Paterson and Barnard succeeded in growing heartwater organisms with ease. This enabled many research actions not only at Onderstepoort but in many
countries of the world. It is believed that the concept of using endothelial cells for the in
vitro cultivation of HW organisms was of major significance for the advances that followed.
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Virology
1908-2008
Years