New Knowledge In Search For Rubella Vaccine

Press, Volume CVIII, Issue 31672, 7 May 1968, Page 25

New Knowledge In Search For Rubella Vaccine

Australian scientists are working to develop a vaccine to prevent rubella, or German measles, which can cause abnormalities in children if the mothers become infected during early pregnancy.

It has been known for some time that rubella is strictly not a form of measles, but is caused by a completely different type of virus. In the United States, scientists have developed a vaccine which is in small scale experimental use.

The Australian team is headed by Dr M. F. Warburton, controller of virology research at Australia’s Commonwealth Serum Laboratories, Melbourne, and Dr lan Holmes, a Melbourne University lec-_ turer, assisted by Miss M. C. Wark.

Dr Holmes said improved methods of diagnosis and new knowledge of the virus would make the task of developing a vaccine more straightforward. Using an electron microscope which magnifies 50,000 times, the Melbourne team believe they are the first scientists to have seen how the virus grows in the cells. They have shown that rubella is not caused by the Paramyxo group of viruses as had been believed until now. Evidence points the virus being similar to arbovirus which are transmittted by insects. Dr Holmes said that

rubella was such a mild disease that scientists would not normally put so much time and effort in trying to find a vaccine, but the tragic side-effects on children made it imperative to keep on with the search. A rubella attack often passed almost unnoticed, he said, but if the infection occurred in the first three months of pregnancy the results could be devastating for the child. The virus entered the foetus, often lodging in the embryonic eye, preventing cell division and causing babies to be born with cataracts and other defects such as hole in the heart. The connection between rubella and these defects was discovered in Australia by Sir Norman Gregg in 1941. It was hoped that by the 1970 s a vaccine would be in general use. Dr Holmes said that although American scientists had succeeded in growing rubella virus in the laboratory in 1962 nobody had been able to see the virus. He said that since rubella was being grown successfully in a number of Melbourne laboratories it was decided a few years ago to have a fresh look at the problem. Recognition Dr lan Jack, of the Royal Children’s Hospital, Melbourne, and Miss Norean Lehman, of Melbourne’s Fairfield Hospital, supplied cultures of cells which had been infected with pedigreed rubella virus, which are from strains that have been tested and proved genuine. The cells were embedded in plastic and cut into slices about one 500,000 th of an inch thick so that they could be examined under electron microscope.

After some searching it was possible to identify virus particles in and around infected cells. Once they had been recognised the task became much easier. The particles were not of ■ the expected type: they were considerably smaller than measles virus and had a different internal structure.

The only known virus which they resembled were those of the arbovirus type. Dr Holmes said this was completely unexpected because arboviruses (for example yellow fever) were by definition transmitted by insects and found mainly in the tropics. There was no previous suggestion that rubella could be related to them. Conclusive Proof After an American report that rubella virus would clump the red blood cells of chickens, Dr Warburton found that the blood cells of pigeons were an even more sensitive indicator. This test was a much quicker and easier method for detection and measurement of the amount of rubella virus than those previously available. Dr Holmes said that when pigeon red blood cells which had been clumped with a large amount of rubella virus were examined in the electron mircoscope particles identical to those in rubellainfected cell cultures were seen sticking to the outside of the blood cells and forming bridges between them. The red blood cells with particles attached were capable of transmitting rubella infection to fresh cell cultures. This was regarded as conclusive proof that the particles were rubella virus. Dr Holmes said the knowledge that rubella was related to the arboviruses was likely to have various effects. “First, it will influence studies aimed at the production of rubella vaccines,” he added. “Second, if rubella virus is like other arboviruses rubella may not be an exclusively human disease, as has always been believed, but may affect birds or animals, from

which the virus could be transferred to humans by insect bites. It is unlikely that this sort of process is important in temperate zones where the virus is known to pass directly from person to person, but it could be important in the tropics." Dr Holmes said it was of more than academic interest to know whether rubella had close relatives among the previously known arboviruses. There were more than 200 other viruses now and more were being discovered. “About 50 are known to infect man,” he added. “In recent years a couple of these have caused very widespread epidemics. While Australia

had not been involved we feel that more should be known about the arboviruses found in Australia. For this reason, in addition to carrying out studies on rubella further, we are also collaborating with Dr Ralph Doherty, of the Queensland Institute of Medical Research, and looking at a number of arboviruses found in the north of Australia.”— Australian News and Information Bureau..

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