Cardiomyopathies--an international problem.

Abstract

certain biochemical aspects of its multiplication may have more in common with the bacteria than with many of the viruses. It is therefore of great interest that two independent groups of workers' 2 have reported that a conventional antibacterial antibiotic of proved pharmacological acceptability in man inhibits the growth of some viruses. This agent is rifampicin, and both reports describe the inhibitory effect it exerts on vaccinia virus. In addition, the second report2 shows that, as well as various poxviruses, it also inhibits an adenovirus. Though it is not new to find an antibacterial agent also active against viruses (methisazone is known to work against the tubercle bacillus as well as against poxviruses) it is of great microbiological interest. The discovery was not the result of an empirical observation but sprang from sound reasoning. It had been shown that the drug inhibits the D.N.A.dependent R.N.A. polymerase of Escherichia coli.3 This enzyme has a vital role in the bacterial cell. Mammalian cells also contain an R.N.A. polymerase, and what makes rifampicin usable as an antibiotic is that the enzyme of the animal cell is much less sensitive to the drug than the bacterial one. Recently it has been shown that vaccinia virus also has an R.N.A. polymerase in the virus particle.4 Hence it was a logical step to see if rifampicin inhibited the growth of vaccinia, and of other D.N.A. viruses too, even though at present it is uncertain whether they contain their own R.N.A. polymerase or whether they use that of the cell. The inhibition of the trachoma agent by rifampicin is no surprise, because this organism is much nearer to the bacteria than are the poxviruses, but a report last week by Y. Becker and Z. ZakayRones5 has the important suggestion that it may be of immediate clinical application in ophthalmology. So far as its clinical use as an antiviral agent is concerned, rifampicin has several hurdles to pass. Its activity against viruses is 500-1,000-fold less than against bacteria, and hence the maintenance of a suitable concentration in the body without serious toxic effects might be impossible. Another difficulty is the matter of timing. In the experimental work it was applied one hour after absorption of virus and was effective when applied up to five hours later, but it is an open question whether it would be too late to apply this drug when a viral infection is well under way. Besides this it is clear from the paper by J. H. Subak-Sharpe and others2 that antibioticresistant variants of vaccinia virus only too readily appear, and this might also be true of adenoviruses. It seems likely that rifampicin will be of value only for infections by viruses which have their own R.N.A. polymerase, and these may be only a minority of D.N.A. viruses. This excludes all D.N.A. viruses which do not have their own R.N.A. polymerase, and all of the R.N.A. viruses, so that there is no question of its becoming a universal antiviral agent. Nevertheless the fact that antiviral activity has been detected in any compound as the result of a logical deduction from known biochemical effects,6 rather than from a hit-and-miss screening project, gives ground for hope in a field where for years optimism has been all too scarce a commodity.