Biology Reference
In-Depth Information
FIGURE 6.7
Containment chamber in greenhouse facility, Centers for Disease Control and Prevention,
Chamblee campus, Georgia.
ENVIRONMENTAL IMPLICATIONS
OF A PARATRANSGENIC STRATEGY
The symbiont/vector association of
R. rhodnii
and
Rhodnius prolixus
satisÝes several requirements
of a paratransgenic strategy:
1.
Symbiotic bacteria that are closely associated with a disease-transmitting vector can be
readily isolated
in vitro
.
2.
Methods exist for genetic transformation of the symbiont.
3.
The genetically transformed symbiont is stable, with minimal loss of the foreign genes
both
in vitro
and
in vivo
.
4.
Genetic transformation of the symbiont does not attenuate its role in the host arthropod.
Sexual maturation and fecundity of the host is not affected by genetic manipulation of
the symbiont.
5.
Delivery of antiparasite molecules by the genetically altered symbiont
in vivo
results in
reduction or clearance of the parasite. Appropriate targeting of the parasite effects a
signiÝcant reduction in host vector competence.
6.
A method exists for Ýeld delivery of genetically altered symbionts. This method mimics
naturally occurring modes of symbiont dispersal in the target vector.
7.
The approach may be customized to other symbiont/reduviid vector relationships. Appli-
cation of this strategy to the ChagasÔ disease vectors
Triatoma infestans
and
T. dimidata
is under way.
Field use of the paratransgenic approach, with environmental release of genetically altered
bacteria, remains a future prospect. The environmental impact of such a release must be considered
carefully, with attention to limits of foreign-gene spread. Issues of regulatory control and policy
pertaining to release of genetically modiÝed organisms are reviewed elsewhere (Beard et al., 2002).
Ongoing studies address issues of nontarget spread of foreign genetic material introduced via
engineered bacterial symbionts.
The paratransgenic approach is predicated on the speciÝc relationship between the target
arthropod and its bacterial symbiont. Methods of dispersal of foreign genetic material to Ýeld
