The viruses that cause diseases as varied as AIDS, hepatitis and West Nile Virus may actually have more in common than was previously thought, new research reveals. According to a study that will appear in the March issue of the journal Molecular Cell, three major groups of viruses use similar mechanisms to replicate their genetic information after they have infiltrated the cells of a host.

There are six broad classes of viruses, each thought to represent a major evolutionary lineage. Michael Schwartz, Jianbo Chen and colleagues at the University of Wisconsin, Madison studied the viral replication process and found that key features of the procedure run parallel in three of the six groups. Positive-strand RNA viruses, reverse transcribing viruses and double-stranded RNA viruses, they report, use similar basic mechanisms to replicate, despite differences in how the viruses move between host cells. The scientists determined that the three groups, which together comprise more than half of the world's known virus families, all replicate their genome using messenger RNA and generate spherules to sequester them within newly infected cells. "This new virus-induced compartment, in which the virus genome is reserved and copied, shows surprising similarities across these different virus groups," notes study co-author Paul Ahlquist of the Howard Hughes Medical Institute at the University of Wisconsin, Madison.

Such fundamental similarities in replication among the viruses suggest they may have common evolutionary origins, the authors write. "These results have added considerably to our understanding of these viruses, and any new basic knowledge is useful in control," Ahlquist says. "If you know the machinery, you know where to throw the wrench to mess it up."