ONE spring day, a 7-year-old girl was sitting outside her house in Prachinburi, northern Thailand. She was tying her shoes ready for school when the neighbour’s puppy attacked her. Her grandmother rushed her to hospital, where she was treated with a potent modern rabies vaccine. Yet two weeks later she died.
Thousands of people bitten by rabid animals in poor countries face the same fate because they are not given a treatment called equine rabies immunoglobulin (ERIG), which blocks the infection while the vaccine takes effect. ERIG is a soup of antibodies harvested from the blood of horses infected with weakened rabies virus. Western pharmaceutical companies have stopped making it and the last stocks are running out. Now a Dutch biotech company, and the World Health Organization, may have alternative solutions.
It is more than a century since Louis Pasteur first used a rabies vaccine to save a boy bitten by a rabid dog. But at least 60,000 people a year, mostly children in Asia and Africa, still die of rabies. Most received no treatment, but an unknown number died despite vaccination.
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Even good vaccines can fail without globulins, and only 1 or 2 per cent of the nearly 8 million people treated for rabies each year get ERIG. For most it is too expensive. A course costs nine times the minimum daily wage in Bangkok, for example. And now it is hard to come by.
Christian Herzog of Berna Biotech in Berne, Switzerland, the last western company to make ERIG, says it stopped because animal rights activists protested against its use of horses, and because the regulatory standards for blood products have become increasingly stringent. ERIG simply became unprofitable.
The Thai Red Cross is now making ERIG for Thailand, and production is starting elsewhere in Asia. But at a meeting in Geneva in October, the WHO’s expert group on rabies decided to organise animal trials with a replacement, made by blending two monoclonal antibodies to rabies derived from mice.
ERIG is cumbersome and expensive to manufacture, and it could contain viruses from horses. Monoclonals are single antibodies that bind specifically to the virus. Because they can be grown in cultured cells they can be made to a high degree of purity in practically unlimited quantities. The WHO thinks its mouse antibodies might be marketable for a quarter the price of ERIG.
Meanwhile, Dutch company Crucell of Utrecht has two human-derived monoclonals in the pipeline. In trials on animals they performed as well as the human-derived version of ERIG, says Jaap Goudsmid, Crucell’s chief scientist.