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This Week in PLOS: Sep 23, 2014

A genome sequencing study in PLOS Genetics suggests that an obligate mutualist bracoviruses have undergone dramatic genome reorganization during adaptation to life inside parasitoid wasps. Researchers from the University of Georgia and elsewhere sequenced a draft genome sequence for the parasitoid wasp species Microplitis demolitor, simultaneously characterizing sequences for the bracovirus living within it. The team's comparisons between the M. demolitor bracovirus and similar viruses that parasitize rather than help out insects indicate that adaptation to the mutualistic lifestyle involved the dispersal of bracovirus genes that cluster in the genomes of related viruses.

Efforts to eradicate the dengue fever virus-carrying mosquito Aedes aegypti from Brazil during the 1940s and 50s seem to have been successful, according to a genetic study in PLOS Neglected Tropical Diseases, though the pest has since crept back into the country from neighboring nations in northern South America and the Caribbean. A team from Brazil and the US collected Ae. aegypti mosquitos from 11 sites in Brazil and analyzed their genetic profiles at a dozen microsatellite markers. In so doing, the study's authors determined that "the genetic patterns in present day populations of Ae. aegypti in Brazil are more consistent with a complete eradication of the species in the recent past followed by re-colonization, rather than the alternative possibility of expansion from residual pockets of refugia."

In PLOS Biology, investigators involved in the Swiss HIV Cohort Study report on an effort aimed at defining differences in HIV resistance and tolerance based on factors such as an individual's age at the time of infection and his or her genetic variation across immune-related sequences, including human leukocyte antigen, or HLA, genes. The team considered variant patterns across the HLA and CC chemokine receptor 5 genes — along with age, viral load set point, and more — in thousands of individuals infected with HIV-1. The analysis indicated that HIV tolerance varies between different HLA-B genotypes. In particular, individuals who carried heterozygous versions of the gene were more tolerant to HIV infection, as were younger individuals.