These slides briefly describe the relation of dengue virus and an endosymbiont bacteria Wolbachia. We can eliminate Dengue fever by using the strategy to manipulate mosquito biology such that it would be unable to transfer virus to humans.

1. FIZZA ALI
Wolbachia and the Biological
Control of Mosquito-borne
Disease

3. INTRODUCTION
Maternally inherited, endosymbiotic bacteria.
New approach of Biological Control.
 Native D. melanogastar strain can invade and sustain in
mosquito population.
In host mosquito:
oReduce adult lifespan
oAffect mosquito reproduction
oInterfere with pathogen replication

4. MOSQUITO BORN DISEASES
Malaria Lymphatic
filariasis
Dengu
e Fever

5. CONTD…
West Nile
virus
Yellow Fever Chikungunya

6. Region of analysis and points with reported
mosquito-borne disease outbreaks between 1980
and 2009. Latitude bands are shown that were used
in analysis.
https://doi.org/10.1016/j.jiph.2017.12.006

8. DENV and MOSQUITO
oDengue fever is arboviral disease.
oSingle stranded RNA virus.
o50-100 million cases of dengue infection appear each
year.
oDengue virus is transmitted by primarily Aedes
aegypti mosquitoes, and secondarily by Aedes
albopictus mosquitoes.
oThese are anthropophilic species.
oInsecticides are effective to control mosquito
population, but are expensive and environmentally
undesirable and their use may produce resistance to
them.
oAlternative approaches are also used.

10. Wolbachia pipientis and
Disease Control
Environmentally benign, More cost effective.
CI was proposed as tool in 1967 in Culex mosquito control, and
then in India n 1970, but not operationally implemented.
Wolbachia was first discovered in ovaries of Culex mosquito in
1924.
Obscure alpha-proteobacterium.
Affect 76% of 2-5 million species of insects.
0.5-1 micro meter size.
Enhance maternal transmission of Wolbachia strain.
Modify infected male’s sperms.

11. CONTD…
 Parthenogentic reproduction of females.
 May provide direct fitness to host as by affecting
nutrition and development, influence fecundity and
provide resistance to pathogens.
 wMelPop strain shortens fruit fly lifespan by 50%.
 wMelPop fails to synchronize its replication with the
host cell, causing shorter lifespan of the host.
 Popcorn
 Extrinsic Incubation Period of DENV is 10-14 days,
only mosquitoes of this age can transmit DENV.

12. A. aegypti and Anophiline mosquitoes do not naturally infected by Wolbachia.
Embryonic microinjections of Wolbachia infected Cytoplasm.
Embryo injections must target the region near the pole cell, in pre-blastoderm
embryo.
Create stable transinfected lines of mosquitoes.
Wolbachia transinfected experiment.
wMelPop-CLA in A. aegypti.
Lifespan reduction.
High bacterial densities in head, salivary glands, ommatida, reproductive
tissues, Malpighian tubules etc.
wAlbB strain.
Wolbachia TRANSFER INTO A.
aegypti MOSQUITOES

13. Anopheles AND Plasmodium
Causes Malaria
Protozoan parasite
1-2 million deaths per year.

14. Wolbachia INTERFERENCE
WITH VIRUSES AND
Can protect fruit fly from DCV, cricket paralysis, flock house and Nora
viruses etc
Wolbachia interferes with transinfacted mousquito’s pathogen such as
DENV, CHIKV and plasmodium etc.
Anti-microbial peptides and pre-activation of innate immune response in
insects may be the reason of pathogen interference ability of Wolbachia.
Immune effector molecule include cecropin, defensin, thio-ester, and C-type
lectins.
Upregulation of immune genes into Anopheles gambiae results in inhibition
of palasmodium.
Opsonization pathway.
Co-expression cecropin A and defensin A in A. aegypti induces resistance

15. CONTD…
Haemolymph Melanization.
New host-symbiont combination.
Direct competition for resources explains:
oHigh density of wMelPop-CLA in A. aegypti tissues.
oExclusion b/w DENV and Wolbachia in fat tissues.
oDENV reliance on host fatty acid synthesis.
Wolbachia mediated viral interference seems to
depend on bacterial loads.
Wolbachia co-exists with japanese encephalitis
viruses in Armigeres mosquitoes.

16. MOLECULAR GENETICS OF
Wolbachia
Ankyrin domain proteins (ANK)
•ANK genes are abundant among Wolbachia.
•Involved in protein-protein interaction.
•ANK repeats in proteins involved in cell cycle regulation,
transcriptional regulators, toxins and cyclin-dependent
kinase inhibitors.
•ANK from closely related strains induce different phenotypes.
•Variability among ANK proteins affect affinity, specificity,
localization and expression of these proteins.
•Expression of single ANK gene is not enough for CI (Yamada
and colleagues)

17. WO Wolbachia bacteriophage
oInfects up to 90% of insect Wolbachia strains.
oHas been suggested to induced CI as viral filtrate
induced CI in Nosania wasp.
oWO-encoded genes, such as virulence factor VrlC,
have been implicated to Wolbachia pathogenicity due
to correlation b/w sequence variation in these genes
and induction of CI in Culex.
oNo correlation b/w phage capsid genes presence and
CI induction.

18. wMel AND wMelPop

19. WOLBACHIA INVASION IN MOSQUITO
POPULATION
Maternal transmission
rate must be high
Produce reproductive
distortions that favors
infected females
High CI induction

20. FITNESS OF Wolbachia INFECTED
MOSQUITOES
Pathogen protection
High metabolic rates
Fecundity cost( low hatch rate)
Reduction of egg survival during embryonic
quiescence
Reduction in no. and size of blood meals
Shaky and bendy
Smaller volumes of saliva