Not many books consider the place of viruses in nature from their own standpoint. It is refreshing to read about the marvellous range of mechanisms by which viruses are selected to survive and flourish in a variety of hosts and environments. As the human population increases, encroaching on the natural habitats of other species, exposure of humans to viruses carried by wild animals will increase. We can only hope that knowledge of viruses' survival mechanisms will yield clues to ways we can limit their harm to us.
Figure 1.
Jaap Goudsmit
Oxford University Press, £18.50, pp 202 ISBN 0 19 513034 0
Rating: ★★★
Many people know that after Koch thought he had established Vibrio cholerae as the cause of cholera a sceptical colleague drank a culture without ill effect. Clearly there was more to it: an X factor was at work. This proved to be not one but two bacterial viruses. One induces the bacterium to produce a receptor for the bacteriophage so that it can enter the bacterial cell; the second phage codes for the cholera toxin that causes the watery diarrhoea. If drinking water is kept free of the V cholerae infected with the phage all is well, just as phage and bacterium live harmlessly together in zooplankton infested coastal waters of the Pacific.
At the other extreme is HIV, which almost certainly came from infection in chimpanzees and eventually was able to pass from human to human, aided in this process by reverse transcriptase, an enzyme that converts viral RNA to DNA and enables it to integrate into the host cell's DNA and thus to survive for as long as the host lives. The book considers the possibility of controlling the disease through live attenuated virus, exploiting the phenomenon called superinfection interference. Attenuated monkey virus quickly establishes durable immunity covering a wide range of antigenic variants. The protection seems to result from interference, as it cannot be passively transferred to normal monkeys by serum antibodies and seems not to involve immune cells. Reversion to virulence is, of course, a problem, but Goudsmit clearly thinks it is an approach worth pursuing.
This is a good read but will be hard going for the lay readers for whom it is written. The author, unfortunately, often ascribes human qualities to viruses, whereas he knows that survival depends on a high rate of replication and mutation to provide candidates to fit the challenge of the ever changing environment.