Demographics of natural oral infection of mosquitos by Venezuelan equine encephalitis virus

RNA viral infections generally generate large and diverse populations within the infected host. This diversity plays a key role in important epidemiological and evolutionary processes. However, several steps during transmission can constrain the demographics and genetics of the virus population, with host primary infection being one of the main barriers. During primary infection, the number of initially infected cells is not infinite, potentially lowering the size and genetic diversity of the colonizing population compared to that present in the donor host. The multiplicity of cellular infection (MOI) in those cells is thus a fundamental parameter determining the demographics and genetics of the colonizing population. The MOI is the number of genomes of a virus that enter and replicate in a cell. This parameter impacts the size of population bottlenecks during primary infection because, for a given number of primary infected cells, the higher the MOI, the larger the colonizing population. Furthermore, the MOI also influences genetic diversity as it largely defines the intensity of genetic exchange and complementation among genotypes during cell co-infection. Despite the importance of the MOI and population bottlenecks, there is a striking lack of formal estimates of these parameters, not only during primary infections but throughout the virus transmission cycle. Here, we use available datasets to estimate the demographics of Venezuelan equine encephalitisvirus (VEEV), a mosquito-borne arbovirus, during the primary oral infection (i.e. the midgut infection) of its mosquito vectors. We estimated the MOI during primary infection in the two transmission cycles using the method developed in Gutiérrez et al. (2010), and we use the results to model the potential for within-cell interactions among viral genotypes during primary infection. We also estimated the population bottleneck Ne endured by VEEV during bloodmeal ingestion and midgut infection. The methodology used is based on Fst statistics and uses genetic variance within and between populations (i.e. the virus populations in the inoculum and midguts) to estimate the effective population size. Despite of the fact that severe bottlenecks, in the order of single digits, are the rule during primary infection in the few virus models analyzed so far, VEEV population sizes were between one and two orders of magnitude higher. Larger populations at primary infection could be crucial during the arboviral cycle of VEEV because they can preserve diversity and facilitate adaptation during the compulsory alternation between arthropod and vertebrate hosts.

Bibliographic Details

Main Author:	Gutiérrez, Serafin
Format:	conference_item biblioteca
Language:	eng
Published:	CIRAD
Subjects:	L73 - Maladies des animaux, L72 - Organismes nuisibles des animaux, U10 - Informatique, mathématiques et statistiques,
Online Access:	http://agritrop.cirad.fr/583670/ http://agritrop.cirad.fr/583670/1/p.50-51%20Gutierrez.pdf
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