Sabin and Koprowski created their vaccines by culturing a strain of polio virus on monkey

Origins of a Plague

Some gaybashers believe it is God's way of punishing homosexuals(同性恋). Some Africans suspect it is just another of the white man's weapons of genocide(种族灭绝). Others have suggested that it was hatched in a biologicalweapons laboratory. There has been no shortage of theories about the origins of the virus that caused the current worldwide AIDS epidemic, but most have ranged from truly bizarre to scientifically implausible at best.

Scientists were drawn into the battle earlier this month, when an article in Rolling Stone magazine contended that the AIDS epidemic was sparked 30 years ago by a polio (小儿麻痹症) vaccine(疫苗), which was accidentally contaminated with a monkey virus. The controversial idea had been completely dismissed by most scientists as simplistic and unprovable, but it does reveal one major point of consensus: African monkeys are almost certainly the source of the deadly virus. Just how the virus made the leap from its simian(猴类的) host to people is still being hotly debated, however, and the more likely explanations are far more complex, involving shifts in African society that turned an isolated disease into a plague.

The polio vaccine theory was actually first proposed in a 1988 editorial in Child and Family, by Herbert Ratner, a former public health officer in Illinois. But the story begins in the mid1950s with Hilary Koprowski, former director of the Wistar Institute in Philadelphis, who, like his colleagues Jonas Salk and Albert Sabin, was racing to produce the vaccine that would protect the world against the scourge(折磨) of polio.

According to the scenario painted in Rolling Stone, batches of Koprowski's vaccine were inadvertently(不小心地) contaminated with a simian AIDS virus. Unlike Salk's vaccine, which contained polio virus that had been killed with formaldehyde, Koprowski and Sabin created their vaccines from a weakened strain of polio virus that would invoke immunity but was too weak to cause disease. Sabin and Koprowski manufactured their vaccines by culturing this weakened strain of polio virus on monkey, kidneys, a fertile medium for the microbe(微生物) and supposedly the source of the simian AIDS virus, now called SIV.

Such accidental contamination is not as farfetched as it might seem. Between 1954 and 1963, an estimated 10 million to 30 million Americans were inadvertently infected with SV40, an apparently harmless monkey virus borne as a silent passenger by both Salk's and Sabin's polio vaccines. SV40 was not discovered until 1961, and the U.S. Food and Drug Administration has since acted to ensure against similar contamination. Vaccine cultures are now carefully screened for all manner of viral contaminations.

Nor is it implausible that human AIDS came from monkey. Researchers got their first hint of this possibility in the mid1980s, when it was discovered that a group of Asian monkeys used for biomedical research had fallen ill with a virus picked up from other monkeys caught from Africa. The germ turned out to be SIV, and subsequent research showed that in the wild at least six species of African monkeys carry their own strain of the virus. It does not make the African monkeys sick, but it proved deadly to Asian monkeys.

Though researchers initially resisted the idea that human AIDS also came from African monkeys, that fact now seems wellestablished. Later last year, molecular(分子) virologists Beatrice Hahn and George Shaw of the University of Alabama presented convincing evidence that the simian virus. that infects sooty(似煤烟般黑的) mangabey, a type of monkey found in West Africa, carries virtually the same genetic material as HIV2, one of the two strains of human AIDS virus. This finding, says Shaw, provides direct evidence that AIDS originated in monkeys.

If the AIDS virus did infect humans through a polio vaccine, Koprowski's is the most likely candidate. The Sabin v

A．Y

B．N

C．NG

A．Y

B．N

C．NG

Salk 疫苗 和Sabin 疫苗皆为脊髓灰质炎病毒减毒活疫苗。()

A.TAT（破伤风抗毒素）

B.Sabin 疫苗

C.Salk 疫苗

D.DPT（百白破三联疫苗）

E.BCG

A.死疫苗

B.类毒素

C.减毒活疫苗

D.亚单位疫苗