Kim M Pepin, Kalli Lambeth and Kathryn A Hanley
Department of Biology, New Mexico State University, Las Cruces, NM, 88003, USA
BMC Microbiology 2008,
8:28.
Abstract
Background
Within-host competition between strains of a vector-borne pathogen
can affect strain frequencies in both the host and vector, thereby
affecting viral population dynamics. However little is known about
inter-strain competition in one of the most genetically diverse and
epidemiologically important mosquito-borne RNA virus: dengue virus
(DENV). To assess the strength and symmetry of intra-host competition
among different strains of DENV, the effect of mixed infection of two
DENV serotypes, DENV2 and DENV4, on the replication of each in cultured
mosquito cells was tested. The number of infectious particles produced
by each DENV strain in mixed infections was compared to that in single
infections to determine whether replication of each strain was
decreased in the presence of the other strain (i.e., competition). The
two DENV strains were added to cells either simultaneously
(coinfection) or with a 1 or 6-hour time lag between first and second
serotype (superinfection).
Results
DENV2 and DENV4 showed significantly reduced replication in mixed
infection relative to single infection treatments. In superinfection
treatments, replication was suppressed to a greater extent when the
interval between addition of each strain was longer, and when a strain
was added second. Additionally, competitive effects were asymmetric:
although both strains replicated to similar peak population sizes in
single infections, DENV2 was more suppressed than DENV4 in mixed
infections. Superinfection treatments yielded significantly lower
combined virus titers than coinfection or single infection treatments.
Conclusion
Competition between DENV strains in cultured mosquito cells can
cause a significant decrease in peak viral population sizes, which
could translate to decreased transmission by the vector. Effects of
competition were asymmetric between DENV2 and DENV4, probably
reflecting significant variation in the competitive ability of DENV
strains in nature. Competition was strongest in superinfection
treatments, suggesting that colonization of new DENV strains could be
impeded in areas where numerous mosquitoes are infected with endemic
DENV strains.