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Poster Full Abstracts - Immunity and Pathogenesis
Poster board number is above title. The first author is the presenter
289
587B
Transcriptional Pausing Orchestrates A Rapid Antiviral Immune Response in
Drosophila
.
Jie Xu
1
, Gregory Grant
1
, Leah Sabin
3
, Beth Gold
1
, Rui
Zhou
2
, Gregory Hannon
3
, Sara Cherry
1
. 1) School of Medicine, University of Pennsylvania, Philadelphia, PA; 2) Dept. of Genetics, Harvard Medical School,
Howard Hughes Medical Institute, Boston, MA; 3) Watson School of Biological Sciences, Howard Hughes Medical Institute, Cold Spring Harbor
Laboratory, Cold Spring Harbor, NY.
Virus-host interactions are a delicate interplay of opposing forces: the virus subverts cellular machinery to promote its replication while the host mounts an
immune response to eliminate the infection. Innate immunity is the first and most ancient line of defense, yet little is known about the cellular factors that
restrict viral infection. Our lab uses RNAi screening in cells of
Drosophila melanogaster
, a model organism that only has an innate immune system, to
identify novel antiviral factors. Of particular interest are pan-antiviral factors that restrict arthropod-borne viruses, for which there is significant morbidity
and mortality worldwide due to the lack of vaccines or therapeutics. Using this approach, we screened a panel of genes involved in various aspects of RNA
metabolism against 4 RNA viruses, including 2 arthropod-borne pathogens. Of the genes whose depletion by RNAi leads to increased infection by at least 3
of the 4 viruses, we found that two independent subunits of the Negative Elongation Factor (NELF) complex had pan-antiviral effects. Additional directed
RNAi screening identified that key components of the NELF-mediated transcriptional pausing pathway is broadly antiviral. These pausing factors also play a
critical role in antiviral restriction
in vivo
. We are now characterizing the mechanism of antiviral restriction for this gene regulatory pathway. Funded by
RO1AI074951 to SC.
588C
Food poisoning:
lam
larvae with melanotic masses are sensitive to frassfood.
Mitchell S. Dushay, Yi Cui, Samiat Jinadu, Harshit Khasa, Neena
Majumdar, Thomas Matthews, Monica Samelson. BCHS, Illinois Institute of Technology, Chicago, IL.
When 1
st
instar
lam
D395
/Df larvae were transferred to fresh food, 33% showed melanotic masses in the 3
rd
instar. However, when they were left to develop
in normal culture vials with their faster-growing
lam
/+ siblings, only 66% of
lam
larvae survived, and none of these had melanotic masses. Similar results
were seen when larvae were transferred to frassfood; frass and medium that other larvae had churned through. Wildtype larvae were fine, but
lam
larvae with
melanotic masses died. This was not medium-limited: frassfood prepared from Nutrifly® or potato, yeast, agar medium gave similar results. Nor was
lethality due to inability to get to nutrition, since
lam
larvae with melanotic masses moved as much as
lam
larvae without masses. Instead, microbes,
presumably from larval gut were responsible. When frassfood was treated with antibiotics or autoclaved,
lam
survival and melanotic mass incidence were
similar to fresh food. Intriguingly, the sensitivity to frassfood of
lam
larvae with melanotic masses was not caused by a general susceptibility to gut infection.
Adding
Serratia marcescens
Db1140 to fresh food reduced the survival of controls and both
lam
mutant larvae with- and without melanotic masses. The oral
susceptibility of larvae with melanotic masses appears limited to
lam
mutants. Fewer
cact
and
hop
TUM
mutant larvae survived on frassfood than fresh food,
but melanotic mass incidence was similar in larvae on frassfood to those on fresh food. Thus, there is a three-way interaction between
lam
, melanotic
masses, and frassfood that relates to immune system function and interactions with gut microflora.
589A
Streptococcus gordonii
is virulent and enhances the virulence of
Porphyromonas gingivalis
in
Drosophila melanogaster
.
Christina Igboin
1
, Ann
Griffen
2
, Eugene Leys
1
. 1) Division of Oral Biology; 2) Division of Pediatric Dentistry, Ohio State University College of Dentistry, Columbus, OH.
We previously developed a
D. melanogaster
killing model to study the interactions between the periodontal pathogen,
Porphyromonas gingivalis
, and the
host, and identified bacterial and host factors that are involved in infection. Mitis group
Streptococci
, including
S. gord
, are typically associated with
periodontal health, however the bacteria possess features that may promote the development of a pathogenic oral flora. We used the model to examine
S.
gord-Drosophila
interactions, and as periodontitis is a polymicrobial infection we examined the interaction between a mixed
S. gordonii-P. gingivalis
infection and
Drosophila
. The
Drosophila
killing model was used to, determine the virulence of wt
S. gord
strains, screen
S. gord
putative virulence genes
for a role in
Drosophila
killing, screen immune-response-defective flies to identify immune response players, and compare the virulence of mixed (
Sg/Pg
)-
and mono (
Sg
,
Pg
)-infections. The bacteria were introduced into the thoraces of
Drosophila
using 30G needles, and the number of live flies was recorded
every 12 hours for 4 days. Multiple wt
S. gordonii
strains are pathogenic in
Drosophila
although with different killing kinetics, and
S. gordonii
SrtA (sortase
A), SspAB (antigen I/II family proteins) and AbpAB (amylase binding proteins) are important for
Drosophila
killing. Contrary to what was previously
observed with the Gram-
P.ging
, the
Drosophila
Toll pathway is involved in fighting a
S. gord
(Gram+) infection. Eiger (JNK pathway ligand) is also
involved in fighting a
S. gord
infection. Finally, although
S. gord
and
P. ging
monoinfections are virulent, a mixture of
S.gord
and
P. ging
is significantly
more virulent in
Drosophila
. A previous study in a rodent model also showed that a
S. gord-P. ging
mixed infection is more virulent than either bacterium
alone. These data demonstrate that
S. gord
can cause pathology in the host, and can enhance the virulence of other oral bacteria. Supported by DE10467.
590B
The anti-wasp immune response across the genus Drosophila.
Balint Z. Kacsoh, Todd A. Schlenke. Department of Biology, Emory University, Atlanta,
GA.
One of the most common parasites of Drosophila in nature are parasitic wasps, which lay their eggs in Drosophila larvae and pupae. Drosophila
melanogaster mounts an immune response against wasp eggs and larvae termed melanotic encapsulation, whereby hemocytes form a multi-cellular, multi-
layered capsule around the intruder before turning it black with melanin. We were interested in whether this melanotic encapsulation response is conserved
across the genus Drosophila, and also whether the same hemocyte cell types used by D. melanogaster are used by other Drosophila species. Thus, we
assayed fly immune mechanisms and immune success in a panel of 25 Drosophila host species using a diversity of parasitic wasp species. We found that
different Drosophila species have unique hemocyte types not found in D. melanogaster, and that certain unique hemocyte lineages are involved in wasp egg
encapsulation. Furthermore, there appear to be at least three distinct mechanisms Drosophila species use to kill wasp parasites: melanotic encapsulation,
encapsulation without melanization, and non-encapsulation. Our study uncovers newfound complexity in the immune responses of Drosophila species
against parasitic wasps.
591C