WSU Virology

the longer the genome, the less gene overlap is present. They confirmed that this also held for DNA viruses. But when they grouped viruses by the kind of capsids they have–icosahedral vs. flexible–they found that this relationship is strong in the icosahedral capsid viruses, but weak in those with flexible capsids.

icosahedral capsids are particularly rigid and constrained in size

Even more outrageous is the notion that genes can overlap and still code for perfectly functional proteins, because this implies that, for part of the gene at least, a different reading frame still has functional meaning. This flies against our intuition that frame-shift mutations are the deadliest of all, and has been likened to taking a paragraph of text, moving all the spaces between words down by a character, and still being able to read it, but this time with a completely different meaning!

For HIV-1, the term latency was initially used in the clinical sense to describe the long asymptomatic period between initial infection and the development of AIDS. However, with the advent of sensitive RT-PCR assays for viremia (Piatak et al. 1993), it became clear that HIV-1 replicates actively throughout the course of the infection, even during the asymptomatic period. The major mechanism by which HIV-1 evades immune responses is not latency but rather through rapid evolution of escape mutations that abrogate recognition by neutralizing antibodies and cytolytic T lymphocytes (Bailey et al. 2004). Nevertheless, it has become clear that HIV-1 can establish a state of latent infection at the level of individual T cells

Within a month, health authorities in 14 countries had identified more than 1,300 cases of respiratory illness that all traced back to those brief encounters somewhere in the hotel. Within five months, the illness — dubbed SARS, for severe acute respiratory syndrome — had caused 8,098 illnesses, and 774 deaths in 26 countries around the world.