tailieunhanh - Báo cáo y học: " Identification of super-infected Aedes triseriatus mosquitoes collected as eggs from the field and partial characterization of the infecting La Crosse viruses"

Identification of super-infected Aedes triseriatus mosquitoes collected as eggs from the field and partial characterization of the infecting La Crosse viruses | Reese et al. Virology Journal 2010 7 76 http content 7 1 76 VIROLOGY JOURNAL RESEARCH Open Access Identification of super-infected Aedes triseriatus mosquitoes collected as eggs from the field and partial characterization of the infecting La Crosse viruses Sara M Reese2 Eric C Mossel 1 Meaghan K Beaty1 EricT Beck3 Dave Geske4 Carol D Blair1 Barry J Beaty 1 and William C Black1 Abstract Background La Crosse virus LACV is a pathogenic arbovirus that is transovarially transmitted by Aedes triseriatus mosquitoes and overwinters in diapausing eggs. However previous models predicted transovarial transmission TOT to be insufficient to maintain LACV in nature. Results To investigate this issue we reared mosquitoes from field-collected eggs and assayed adults individually for LACV antigen viral RNA by RT-PCR and infectious virus. The mosquitoes had three distinct infection phenotypes 1 super infected SI mosquitoes contained infectious virus large accumulations of viral antigen and RNA and comprised 17 of 17 825 of assayed mosquitoes 2 infected mosquitoes I contained no detectable infectious virus lesser amounts of viral antigen and RNA and comprised of mosquitoes and 3 non-infected mosquitoes I- contained no detectable viral antigen RNA or infectious virus and comprised of mosquitoes. SI mosquitoes were recovered in consecutive years at one field site suggesting that lineages of TOT stably-infected and geographically isolated Ae. triseriatus exist in nature. Analyses of LACV genomes showed that SI isolates are not monophyletic nor phylogenetically distinct and that synonymous substitution rates exceed replacement rates in all genes and isolates. Analysis of singleton versus shared mutations Fu and Li s F revealed that the SI LACV M segment with a large and significant excess of intermediate-frequency alleles evolves through disruptive selection that maintains SI alleles at higher frequencies than the average mutation rate. A QTN in the LACV