M.Sc. seminar presentation slides

1. BIOCHEMICAL AND CELLULAR
PERSPECTIVE OF DRUG-RESISTANT
MALARIA
Presented by
Offor, Gloria Nwabugwu
(14PCP00958)
B.Sc. NAU, M.Sc. UI
Supervised by: TWAS/CU Supervisors
November, 2015.
A seminar
presentation on

2. OUTLINE
• Introduction
• The malaria fight: brief history
• Lifecycle of Plasmodium
• Merozoite invasion of erythrocytes
• Mechanisms of resistance to antimalarial
drugs
• The future: prevention of drug resistance
• Conclusion and recommendations
• References
2

3. INTRODUCTION
• Malaria is a public health problem!
• Globally, an estimated 3.3 billion people
in 97 countries and territories are at risk
of being infected with malaria and
developing disease.
• According to the latest estimates, 198
million cases of malaria occurred
globally in 2013 and the disease led to3

4. 4
Fig. 1: Countries with ongoing transmission of malaria, 2013
Source: (World Health Organization, 2014)

5. CONT’
• Malaria is caused by a parasite of the genus
plasmodium, transmitted via the bites of
infected female Anopheles mosquitoes (Bray
and Garnham, 1982).
• Four plasmodium species infect humans: P.
falciparum, P. vivax, P. ovale and P.
malariae.
• Among them, P. falciparum is the most
prevalent malaria species worldwide,
especially in Africa, causing the most severe
form of the disease and being responsible5

6. CONT’
• P. vivax is the second most common
species, located mainly in Asia and South
America, and can cause a relapsing form of
malaria (Price et al., 2007).
• In recent years human cases of malaria
have also been recorded due to P. knowlesi
– a species that causes malaria among
monkeys, and occurs in certain forested
areas of South-East Asia (World Health
Organization, 2014).
• In many parts of the world, the parasites6

7. THE MALARIA FIGHT: BRIEF HISTORY
• 1898: Discovery of malaria parasite
mode of transmission
• 1900-1946: 10 countries were
declared malaria-free
• 1955-1969: Global Malaria
Eradication Programme using
chloroquine chemotherapy.
• 27 countries were declared malaria-
free. 7

8. CONT’
• 1960: Emergence of chloroquine-
resistant malaria parasites
• Other antimalarial drugs deployed
include: sulfadoxine-pyrimethamine,
mefloquine, amodiaquine, and
quinine.
• 2001: World Health Organization
ACT recommendation
• 2008: Emergence of artemisinin8

9. LIFECYCLE OF PLASMODIUM
9
• The malaria parasite exhibits a
complex life cycle involving an insect
vector (mosquito) and a vertebrate
host (human).
• Plasmodium undergo three distinct
asexual replicative stages
• exo-erythrocytic cycle
• blood stage cycle
• sporogonic cycle

10. CONT’
• This results in the production of
invasive forms (merozoites and
sporozoites).
• A sexual reproduction occurs with
the switch from vertebrate to
invertebrate host and leads to the
formation of the invasive ookinete.
10

11. 11
Fig. 2: Lifecycle of plasmodium Source:

12. MEROZOITE INVASION OF
ERYTHROCYTES
• The blood stage merozoite is the
smallest cell within the plasmodium
lifecycle.
• The acute, life threatening, phase of
malarial infection arises when the
merozoite form of the parasite
undergoes multiple cycles of red
blood cell invasion and rapid
proliferation (Cowman et al., 2012).
12

13. CONT’
• Invasion of the red blood cell by P.
falciparum merozoites occurs in four
distinct phases (Farrow et al., 2011):
• Phase 1(Adhesion)
• Phase 2 ( Reorientation)
• Phase 3 (Tight-junction formation)
• Phase 4 (Ingress)
• Finally, the erythrocyte membrane fuses so
that the merozoite becomes encapsulated,
within a so-called parasitophorous vacuole,13

14. 14
Fig. 3: Three-dimensional diagram of a merozoite and its core
secretory organelles (Cowman et al., 2012).

15. 15
Fig. 4: Early stages of red blood cell invasion by the malaria
merozoite (Chitnis and blackman, 2000).

16. 16
Fig. 5: A time course of merozoite invasion of the erythrocyte from
egress through postinvasion (Cowman et al., 2012).

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(Cowman et al., 2012)

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19. MECHANISMS OF RESISTANCE TO ANTIMALARIA
DRUGS
• Normally, eukaryotic cells evade
xenobiotics toxicity through trafficking them
into the Digestive vacuole (DVs) or
lysosomes for further procession or expel
them extracellularly (Dobson et al., 2009).
• In plasmodium, two types of transporters
mediate xenobiotics trafficking to the DV
(Djimde´ et al., 2001) :
• P-glycoprotein related transporters- pfmdr-
1, pfmdr-2 and pfmrp
• drug metabolite transporter (DMT)- pfcrt
19

20. CONT’
• P-Glycoprotein Transporters. pump
xenobiotics outside the cytosolic
compartment into the DV (Anderson et al.,
2005).
• Pfmdr-1 and pfmrp-1 point mutations ablate
the transporter capacity to drift drugs,
namely, CQ, quinoline (QN), mefloquine
(MQ), halofantrine (HF), and lumefantrine
(LM), into the DV.
• Pfcrt- acts as an anion channel and
mediates CQ efflux outside the DV. 20

21. 21Fig. 6: Detailed structure of P-glycoprotein molecule (Ibraheem et

22. 22
Fig. 7: Detailed structure of pfcrt protein (Ibraheem et al.,

23. CONT’
• Other mechanisms of antimalarial drug-
resistance include:
• Gene mutations encoding two key
enzymes involved in folate synthesis
(DHFR and DHPS) confer varying
degrees of resistance to anti-folate
combination drugs eg sulfadoxine-
pyrimethamine which block these
enzymes.
• single-point mutations in the
cytochrome-b gene confers resistance23

24. THE FUTURE: PREVENTION OF DRUG
RESISTANCE
• Interventions aimed at preventing drug
resistance generally focus on:
• Reducing overall drug pressure.
• Improving the way drugs are used
• Combination therapy
• In the future, antimalarial therapy may be
expanded by combining chemotherapy with
vaccines (or other drugs) specifically
designed to inhibit transmission of malaria.
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25. CONCLUSION
• With the emergence of drug resistance to
the artemisinin derivatives, often referred to
as the last stronghold in malaria
chemotherapeutical treatment, it is of critical
importance to implement antimalarial drug
policies to contain, and hopefully curtail the
spread of resistance.
• Failure to do so would lead to a tragic
setback in the current efforts to eliminate
malaria, and achieved reductions in malaria-
related morbidity and mortality. 25

26. RECOMMENDATIONS
• Support ways of reducing malaria infection
rates or transmission rates which Include:
• the use of insecticide-treated bednets,
• indoor residual insecticide spraying
• environmental control (mosquito breeding site )
• other personal protection measures (e.g. use of
repellent soap)
• An effective and deliverable vaccine would also be
greatly beneficial
• Support new drug development! Support CU
Malaria Bioinformatics Group!!
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27. REFERENCES
1. Anderson, T. J. C., S. Nair, H. Qin, H., Singlam, S., Brockman, A., Paiphun, L. and Nosten, F. (2005). Are
transporter genes other than the chloroquine resistance locus (pfcrt) and multidrug resistance gene (pfmdr)
associated with Antimalaria drug resistance? Antimicrobial Agents and Chemotherapy 49:2180–2188.
2. Bray, R.S. and Garnham, P.C. (1982). The life-cycle of primate malaria parasites. British Medical Bulletin
38:117–122.
3. Chitnis, C.E. and Blackman, M.J. (2000). Host cell invasion by malaria parasite. Parasitology Today 16: 411-
415.
4. Cowman, A.F., Berry, D. and Baum, J. (2012). The cellular and molecular basis for malaria parasite invasion of
the human red blood cell. Journal of Cell Biology 19:961-971.
5. Dobson, P.D., Lanthaler, K., Oliver, S.G. and kell, D.B. (2009). Implications of the dominant role of transporters
in drug uptake by cells. Current Topics in Medicinal Chemistry 9:163-181.
6. Djimde’, A.D., Doumbo, O.K., Cortese, J.K., Kayentao, K., Doumbo, S., Diourte, Y., Coulibaly, D., Dicko, A.,
Su, X.Z., Nomura, T., Fidck, D.A., Wellems, T.E. and Plowe, C.V. (2001). A molecular marker for chloroquine-
resistant falciparum malaria. The New England Journal of Medicine 344:257–263.
7. Farrow, R.E., Green, J., Katsimitsoulia, W.R., Holder, A.A. and Molloy, J.E. (2011). The mechanism of
erythrocyte invasion by the malaria parasite, plasmodium falciparum. Cell and Developmental Biology 22:953-
960.
8. Ibraheem, Z.O., Majid, R.A., Noor, S.M., Sedik, H.M. and Basir, R. (2014). Role of different pfcrt and pfmdr-1
mutations in conferring Resistance to Antimalarial Drugs in plasmodium falciparum. Malaria Research and
Treatment 1-17.
9. Lifecycle of plasmodium falciparum. http://www.dpd.cdc.gov/dpdx sourced on Monday, 9 November 2015 at
11:30 p.m.
10. Price, R.N., Tjitra, E., Guerra, C.A., Yeung, S., White, N.J. and Anstey, N.M. (2007). Vivax malaria: neglected
and not benign. American Journal for Tropical Medicine and Hygiene 77: 79–87.
11. World Health Organization (2014) World malaria report 2014, WHO Press 1–126.
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28. THANK YOU
FOR
LISTENING
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