The rapid spread of recombinants during a natural in vitro infection with two human immunodeficiency virus type 1 strains.

We quantified a population of recombinants in a natural in vitro infection, using wild-type viruses without any pressure. It was found that recombinants emerged early after infection and constituted more than 20% of the whole proviral population 15 days after infection. Furthermore, recombinants were isolated as infectious viruses by simple limiting dilution. These results imply that, in addition to the high mutation rate of human immunodeficiency virus type 1 (HIV-1), recombination among HIV-1 strains plays a significant part in the development of the high diversity of HIV-1.