Recombinant Tula hantavirus shows reduced fitness but is able to survive in the presence of a parental virus: analysis of consecutive passages in a cell culture

Plyusnina, Angelina; Plyusnin, Alexander

Recombination in RNA viruses serves two main purposes: (i) it generates and spreads advantageous genetic combinations; and (ii) it counters the deleterious effect of mutations that, due to the low fidelity of viral RNA polymerases and lack of proofreading, occur with high frequency [1] . The purging function is, naturally, attributed to the homologous recombination (HRec), i.e. recombination between homologous parental molecules through crossover at homologous sites. HRec was first described for the positive-sense RNA viruses [2, 3] and subsequent studies lead to the widely accepted copychoice model [4] . HRec was later shown to occur in rotaviruses thus adding double-stranded RNA viruses to the list of viruses capable of recombination [5] . Negativesense RNA viruses that occupy the largest domain in the virus kingdom until recently were known to undergo nonhomologous recombination only, forming either defective genomes, like polymerase "mosaics" of influenza A virus DI-particles [6] and "copy-backs" of parainfluenza virus [7] or hybrids between viral and cellular genes [8] or between different viral genes [9] . The first evidence for HRec in a negative-sense RNA virus has been obtained on hantaviruses [10, 11] .