期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 104, 期 1, 页码 208-212出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0605688104
关键词
chickenpox; shingles virulence; epidemiology; IE62
资金
- NIAID NIH HHS [R21 AI024021, R01 AI024021, AI 24021, AI 127187] Funding Source: Medline
- Wellcome Trust [GR075427MA-075427] Funding Source: Medline
The Oka vaccine strain is a live attenuated virus that is routinely administered to children in the United States and Europe to prevent chickenpox. It is effective and safe but occasionally produces a rash. The vaccine virus has accumulated mutations during its attenuation, but the rashes are not explained by their reversion, unlike complications reported for other viral vaccines. Indeed, most of the novel mutations distinguishing the Oka vaccine from the more virulent parental virus have not actually become fixed. Because the parental alleles are still present, the vaccine is polymorphic at > 30 loci and therefore contains a mixture of related viruses. The inoculation of > 40 million patients has consequently created a highly replicated evolutionary experiment that we have used to assess the competitive ability of these different viral genotypes in a human host. Using virus recovered from rash vesicles, we show that two vaccine mutations, causing amino acid substitutions in the major transactivating protein IE62, are out-competed by the ancestral alleles. Standard interpretations of varicella disease severity concentrate on the undeniably important effects of host genotype and immune status, yet our results allow us to demonstrate that the viral genotype is associated with virulence and to identify the key sites. We propose that these loci have pleiotropic effects on the immunogenic properties of the virus, rash formation, and its epidemiological spread, which mould the evolution of its virulence. These findings are of practical importance for reducing the incidence of vaccine-associated rash and promoting public acceptance of the vaccine.
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