Lentivirus

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  eBook - ePub

  Evolutionary Dynamics

  Exploring the Equations of Life

  • Martin A. Nowak(Author)
  • 2006(Publication Date)
  • Harvard University Press

    (Publisher)

  HIV INFECTION 10 THE EMERGENCE of the human immunodeficiency virus (HIV) in the early 1980s demonstrated that infectious diseases represent a major problem for human health all over the world and that newly arising infectious agents can be especially devastating. As the human species becomes more abundant on the globe, having crossed the six billion threshold in 1999, the opportunity increases dramatically for infectious agents of other species to invade the human host. Despite tremendous progress in molecular biology and medicine, our methods to combat infectious diseases are limited. There are successful vaccines against a number of agents, but all attempts have so far failed to construct an HIV vaccine. The reasons for this failure are not clear, but include the virus’s ability to infect cells of the immune system and to mutate away from any opposing selective forces. HIV belongs to the class of retroviruses, which reversely transcribe their RNA genome into DNA (Figure 10.1). Howard Temin and David Baltimore won a Nobel Prize in Medicine for the discovery of the reverse transcriptase enzyme. The viral DNA can be integrated into the genome of the host cell and can remain there for an effectively unlimited time. Anywhere between 2% and 8% of the human genome consists of “burnt-out” retroviruses that have integrated at some point in our genomic history and have subsequently received inactivating mutations. Figure 10.1 The life cycle of the human immunodeficiency virus (HIV). The virion contains two copies of the viral genome in form of single-stranded RNA. After entry into the host cell, the reverse transcriptase that comes with the virion uses both copies of the RNA genome to produce an RNA-DNA hetero-duplex and subsequently double-stranded viral DNA. This viral DNA (the provirus) is integrated into the genome of the host cell. The provirus can remain silent for a long time or can immediately induce the host cell to produce messenger RNA (mRNA)

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