Bacterial Adaptive immunity, Gene drives and the genetic control of Malaria

ADAPTIVE BACTERIAL IMMUNITY, GENE DRIVES AND THE

GENETIC CONTROL OF MALARIA

BYONILE-ERE OLABODE

14PCQ01211

DEPARTMENT OF BIOLOGICAL SCIENCESMICROBIOLOGY UNIT

COVENANT UNIVERSITY, OTA

AUGUST, 2016.

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Outline• Background• Malaria• Adaptive Immunity In Bacteria

• CRISPR-CAS9 Genome engineering • CRISPR-CAS9 in controlling malaria• Gene Drive

• Population Replacement• Population Suppression

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MALARIA IS A COMPLEX DISEASE• Drug Resistance• Insecticide Resistance• Misdiagnosis• HRP-II Deletion• Over and under Diagnosis

• Asymptomatic Reservoir (we don’t fully understand this)• Partial Immunity• Hundreds of thousands die yearly• Costs Africa 20billion USD yearly

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VISION 0:2030- Get to Zero by 2030The WHO identified malaria control as being core to getting to zeroCurrent control strategies

• Insecticide Treated Nets• Transmission Blocking• Surveillance (T3)• Indoor Residual Spraying

Issues

• Compliance • Insecticide resistance• Interventions are not ‘Africa-

proof’

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Way(s) Forward?

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Discovery of Adaptive Immunity In Bacteria

Figure 1- CRISPR Locus

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CRISPR Mechanism

Rath et al., 2015Fig 2: CRISPR Adaptation Fig 3: Steps in CRISPR immunity

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CRISPR-CAS9- Nature’s Find and Replace Tool

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CRISPR-CAS9 Genome Editing

NHEJ- Non-homologous End Joining (Knock-out)HR- Homologous Directed Recombination (Knock-in)

Figure 4- CRISPR-CAS Genome Editing

We Will come talk about this a bit more in the slides to come

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…and the CRISPR-CAS9 revolution was born

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But how does all of this information help us control malaria?

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Genetic Control of Malaria• Gene Drive- "stimulating biased inheritance of particular genes to

alter entire populations." • Converting Heterozygous to Homozygous

• Block Parasite Development- Population Replacement• Reduce Reproductive fitness- Population Suppression

Plasmodium Mosquito Human

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GENE DRIVE• Mendelian inheritance will

eventually dilute out the transgene

• To overcome this, one would need to literally release more transgenic males than there are wild type females- UNREALISTIC

• Is there a way around this?

McLean& Jacobs-Lorena, (2016) Figure 5: Mendelian Inheritance VS Gene Drive

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CRISPR-CAS9 Gene Drive

Figure 6- CRISPR-CAS Genome EditingThis is the outcome desired in a gene drive

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Population Replacement- Gantz et al., 2015

Figure 7: Gene Drive

Mutagenic Chain Reaction

• Asian malaria vector Anopheles stephensi

• Inserted antiplasmodial effector genes m1C3 and m2A10 along with cas-gRNA gene

• They reported that over about 95% of the progeny carried inserted gene

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Population Suppression- Hammond et al., 2016

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Suppression Versus Replacement• Population Suppression• Advantages

1. Can eliminate vector for more than one disease (e.g Aedes aegypti –Zika, Yellow Fever, Dengue fever)

2. If successful can solve problem permanently• Disadvantages

1. Could lead to extinction of an organism2. Ecological safety

• Population Replacement • Advantages

1. Can eliminate targeted disease without wiping out vector2. Minimal ecological damage

• Disadvantages1. Requires multiple implementations to eliminate all vector-mediated diseases (Intervention is

diseases specific i.e. can only handle one diseases per design)

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Pros, Cons and Issues• Ethics• Ecological costs/Unintended Outcomes• Possibility of unintended outcomes• Mosquitoes are required for pollination

• Fitness cost to mosquitoes hence eventual dilution of population supressing gene• Boost In GDP of tropical nations suffering from mosquito borne

diseases• Boost in Tourism• Brazil-Zika Conspiracy

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Conclusion

Gene drives could potentially wipe out not just malaria but every mosquito borne diseases (Yellow Fever, Dengue, Zika etc). It is therefore imperative that all hands are on deck to perfect the technology in the achievement of a world free of Malaria

National Academy of Sciences, 2016

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References • Jinek, M., Chylinski, K., Fonfara, I., Hauer, M., Doudna, J. A., & Charpentier, E. (2012). A programmable dual-RNA-guided DNA

endonuclease in adaptive bacterial immunity. Science (New York, N.Y.), 337(6096), 816–21. http://doi.org/10.1126/science.1225829• McLean, K. J., & Jacobs-Lorena, M. (2016). Genetic Control Of Malaria Mosquitoes. Trends in Parasitology, 32(3), 174–176.

http://doi.org/10.1016/j.pt.2016.01.002• Rath, D., Amlinger, L., Rath, A., & Lundgren, M. (2015). The CRISPR-Cas immune system: Biology, mechanisms and applications.

Biochimie, 117, 119–128. http://doi.org/10.1016/j.biochi.2015.03.025• Gantz, V. M., Jasinskiene, N., Tatarenkova, O., Fazekas, A., Macias, V. M., Bier, E., & James, A. A. (2015). Highly efficient Cas9-mediated

gene drive for population modification of the malaria vector mosquito Anopheles stephensi. Proceedings of the National Academy of Sciences, 112(49), E6736–E6743. http://doi.org/10.1073/pnas.1521077112

• Hammond, A., Galizi, R., Kyrou, K., Simoni, A., Siniscalchi, C., Katsanos, D., … Nolan, T. (2016). A CRISPR-Cas9 gene drive system targeting female reproduction in the malaria mosquito vector Anopheles gambiae. Nature Biotechnology, 34(1), 78–83. http://doi.org/10.1038/nbt.3439

• Bolotin, A., Quinquis, B., Sorokin, A., & Dusko Ehrlich, S. (2005). Clustered regularly interspaced short palindrome repeats (CRISPRs) have spacers of extrachromosomal origin. Microbiology, 151(8), 2551–2561. http://doi.org/10.1099/mic.0.28048-0

• Mojica, F. J. M., Díez-Villaseñor, C., García-Martínez, J., & Soria, E. (2005). Intervening sequences of regularly spaced prokaryotic repeats derive from foreign genetic elements. Journal of Molecular Evolution, 60(2), 174–82. http://doi.org/10.1007/s00239-004-0046-3

• Pourcel, C., Salvignol, G., & Vergnaud, G. (2005). CRISPR elements in Yersinia pestis acquire new repeats by preferential uptake of bacteriophage DNA, and provide additional tools for evolutionary studies. Microbiology (Reading, England), 151(Pt 3), 653–63. http://doi.org/10.1099/mic.0.27437-0

• National Academy of Sciences. (2016). Gene Drives on the Horizon Advancing Science, Navigating Uncertainty, and Aligning Research with Public Values- Brief. Washington DC. Retrieved from http://nas-sites.org/gene-drives/ Assessed on 23/08/16.

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THANK YOU FOR YOUR TIME

IT BEGINS WITH YOU