Genetically Modified Mosquitoes
While pursuing my PhD at the Johns Hopkins Bloomberg School
of Public Health, I worked with Dr.
George Dimopoulos on various aspects of mosquito
immunity. Dr. Dimopoulos had acted as Dr. Xi's post-doctoral
mentor prior to Dr. Xi moving to Michigan State University,
meaning that a lot of the skills I learned during my Master's
degree transferred directly into the experiments I would be
doing with Dr. Dimopoulos. Consequently, I was able to hit the
ground running while working on my PhD and quickly make
multiple novel observations about the Anopheles
mosquitoes I began studying.
Physiological changes brought about by genetic upregulation of the mosquito immune system
Dr. Dimopoulos' group focuses on the ways that the mosquito
immune system can be used to help control vector-borne
disease. While there are many projects going on in the
laboratory, including projects on dengue virus and various
aspects of the mosquito microbiota, I began working on the
ways in which the mosquito innate immune system controls
infection by the Plasmodium parasites that cause human
malaria. Previous members of the group had already created
multiple strains of genetically modified Anopheles
stephensi mosquitoes with greatly increased resistance
to P. falciparum, and I set out to characterize those
strains. I began by studying two specific strains with
blood-meal inducible increased expression of the transcription
factor Rel2. Rel2 is a positive regulator of the mosquito IMD
immune pathway, and increased expression of Rel2 following a
blood meal leads to a cascade of immune responses and killing
of the parasite. I measured changes in the transcriptome and
proteome of the mosquitoes following immune induction,
allowing me to identify a large number of genes under the
control of the IMD pathway. Further characterization of these
genes led to the identification of novel anti-Plasmodium
factors that are being studied further for their potential as
targets for interrupting malaria transmission.

Fitness effects of short term immune activation on Anopheles
stephensi mosquitoes
Multiple laboratory groups have created genetically modified
mosquitoes with limited ability to spread human pathogens, but
none of these mosquitoes have been released as part of
vector-borne disease control programs. While the release of
genetically sterilized Aedes aegypti males to reduce
the mosquito population is a promising step forward for the
use of genetically modified mosquitoes to control human
disease, these differ fundamentally from those meant to
replace the natural population. One reason for the delay in
releasing a strain to replace wild-type mosquitoes with
refractory mosquitoes hinges on concerns that the genetically
modified mosquitoes will be less fit than the wild-type
mosquitoes, and therefore will be unable to compete with them.
I tested various aspects of mosquito fitness, including
lifespan and fecundity under various conditions, and found no
difference between wild-type and our genetically modified
mosquitoes in the laboratory. Further, I saw that, under some
circumstances, the genetically modified mosquitoes could have
a mating advantage over wild-type mosquitoes. This advantage
appears to be brought about by changes in the mosquito
microbiota in response to the genetic modification, and
represents the first observation of a genetically modified
mosquito outcompeting wild-type mosquitoes.
My time with Dr. Dimopoulos was highly productive, and taught
me a great many things. In addition to increasing my knowledge
of molecular biology techniques such as DNA microarrays and
iTRAQ, I was able to go on two field trips and gain experience
working outside of the laboratory. I first went on a mosquito
collecting trip to Puerto Rico with Dr. Dimopoulos and two
fellow graduate students. We spent a week collecting
mosquitoes, mostly from the genus Aedes, in order to
learn more about the natural microbiota of wild mosquitoes.
Later in my thesis work, I spent a month working with Dr.
Kevin Kobylinski and the entomology group at the Armed Forces
Research Institute of Medical Sciences in Bangkok. There, I
taught the entomologists how to perform RNA interference and
adult injections while testing the effects of the mosquito
immune system on Plasmodium vivax infection in the
mosquitoes. While my results were largely inconclusive, it was
a great opportunity to learn to work in a resource limited
setting, and to work with human samples for the first time.
To learn more about the research in Dr. Dimopoulos' lab,
check out his group
website or that of his current postdoc Dr. Sarah M. Short.