Using CRISPR to shed light on new solutions for two old, ‘invisible’ diseases

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Category: Network Events

July, 2018; and as the cool of evening descends over Rio de Janeiro, 22 young researchers from South America and the UK gather, excited and a little nervous, to meet each other and their tutors for the next 5 days.  The teaching team of 9 international experts are here to provide training in use of CRISPR-Cas9 technology in trypanosomes (Tryps), the parasites that cause the neglected tropical diseases (NTDs) Chagas disease (American trypanosomiasis) and leishmaniasis.  The students’ excitement is justified; their new skills will transform their professional lives, and may also be life-changing for many of the ~0.5 billion people worldwide at risk from these infections.1-4 This ground-breaking training is also available in Kolkata, India, in March 2019.

‘Invisible’ diseases: A global problem
Chagas disease and leishmaniasis, in combination, resulted in a reported ~16,000 deaths5 and ~321,000 ‘years lost to disability’6 in 2017. However, this barely reflects the true number of infections and the extent of their human impact.
These NTDs mostly afflict the poorest of the world’s poor,7 particularly in remote, rural areas where infrastructure such as sanitation and clinical resources are limited8,9 and data is under-reported.10
Many patients initially show no recognisable symptoms.4,11  In those suffering from other diseases, including HIV, the parasites present symptoms which can seem like a completely different clinical problem.10,12
Stigma also ‘hides’ many patients; the scarring from cutaneous forms of leishmaniasis excludes ~40 million sufferers from opportunities for education, marriage and employment.13,14

Leishmania parasites are spread by sandflies (Phlebotomus spp, above left) and infect white blood cells (below left); the disease appears clinically as a visceral form (above, right) which is lethal if untreated, or as cutaneous sores (right, below) causing disfiguring scars. Images: Wikimedia Commons.

The need for specific solutions
The current (chemotherapy-based) treatments licensed for these NTDs have been in use for over 40 years, and themselves can be lethal.15-17  We need alternatives; simple, safe, effective drugs that directly target the parasites without harming patients.7
Investigating which Tryp genes code for potentially suitable drug targets is difficult.  These parasites have an ‘odd’ physiology, making for a biological system in which many standard genetic techniques simply do not work.
Another problem is that few researchers in endemic countries are equipped with the specialist skills required for working with these organisms.

Chagas disease is spread by so-called ‘kissing’ or ‘assassain’ bugs (Triatoma spp, above left) which often bite patients around the eyes, causing local swelling (above, right). The parasites (Trypanosoma cruzi, below left) stay in the blood during the acute phase of the infection, but then can ‘hide’ in the body as a chronic disease, causing damage resulting later in heart failure (below right) or gastrointestinal problems. Images: Wilkimedia Commons.

Training the next Tryp pioneers
This need inspired a Global Network for Neglected Tropical Diseases to commit to training the next generation of early career Tryps researchers, alongside their mandate to find new drug targets for Chagas disease and leishmaniasis.  Their workshop programme aims to develop the necessary skills base in Tryps specialists from endemic countries, and build effective worldwide collaborative networks – both vital for a truly sustainable global health solution.7,18
CRISPR-Cas9 technology is revolutionary, enabling researchers to tag, edit or remove specific genes with exquisite precision,19,20 and can be used in Tryps.
  • “CRISPR-Cas9 impacts my research in an unprecedented way… [which] I could not achieve using other molecular methods”
    (Aitor Casas-Sanchez, UK)
This workshop, the Network’s first training event, equips the students to apply CRISPR techniques in Leishmania spp. (causing leishmaniasis) and Trypanosoma cruzi (causing Chagas disease), and has provided access to the tutors’ wealth of insights and ideas.
  • “The new strategies suggested… have opened a panorama of options”
    (Evelyn Tevere, Argentina)
  • “This course will help my career progression and allow me to play an outstanding role [in finding solutions to these diseases] in Brazil”
    (Willian Bertolo, Brazil)

Above; workshop participants and tutors in the laboratory. All students had opportunities to present their work (below left) and gain hands-on practical laboratory skills (below right).

A new cohort of enthusiasm
Beyond their own research, the students’ CRISPR-Cas9 expertise also expands the possibilities for others at their home institutions.  Attendees in Rio represented 14 research organisations from Brazil, Argentina, Uruguay and the UK; many are the first amongst their colleagues to gain this vital expertise.
  • “The course has proved essential for …strengthening my research group and the institution where I work… I have now trained others to work with CRISPR”
    (Ana-Maria Murta Sante; Brazil)
Even more significant, these students have formed for themselves a network of ongoing support, inspired by their shared determination to find solutions for these diseases in their respective countries.
  • “Ties were forged that have led to cooperation… [including] sharing of protocols, materials, and strategies” (Evelyn Tevere, Argentina)
The end-of-course celebration in Rio completed only the first step of the task for the NTD Network.  Their next workshop, in Kolkata, in March, 2019 will introduce CRISPR-Cas9 techniques to Tryps researchers in India for the first time.

 

Mags Leighton

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References

  1. Alvar J,et al. 2012 PLoS One 2012; 7: e35671;
  2. Drugs for Neglected Diseases initiative. Leishmaniasis disease factsheet. 2018.  Available at https://www.dndi.org/wp-content/uploads/2018/12/Factsheet2018_Leishmaniasis.pdf  (accessed December 2018)
  3. Drugs for Neglected Diseases initiative. About Chagas disease. Available at https://www.dndi.org/diseases-projects/chagas/ (accessed December 2018);
  4. Mora, G. Chagas cardiomyopathy. E-J Cardiol Pract 2016; 14:(31) Available at https://www.escardio.org/Journals/E-Journal-of-Cardiology-Practice/Volume-14/Chagas-cardiomyopathy (accessed December 2018).
  5. GBD 2017 Causes of Death Collaborators. Lancet 2018; 392: 1736–1788.
  6. GBD 2017 Disease and Injury Incidence and Prevalence Collaborators. Lancet 2018; 392: 1789–858.
  7. World Health Organization. Accelerating work to overcome the global impact of neglected tropical diseases: a road map for implementation. 2012. Available at http://www.who.int/neglected_diseases/NTD_RoadMap_2012_Fullversion.pdf (accessed December 2018).
  8. Martins Melo FR, et al. Acta Tropica 2014; 130: 167–174.
  9. Medecin Sans Frontieres. Bringing hope to sufferers of a neglected disease. 5th December 2018.  Available at https://msfaccess.org/bringing-hope-sufferers-neglected-disease (accessed December 2018).
  10. Singh OP and Sundar S. J Parasitol Res 2015; 2015: 239469.
  11. Ready PD. Clin Epidemiol 2014; 6: 147–154.
  12. World Health Organization. Chagas disease epidemiology. Available at https://www.who.int/chagas/epidemiology/en/ (accessed December 2018).
  13. Medecin Sans Frontieres. Bringing hope to sufferers of a neglected disease. 5th December 2018.  Available at https://msfaccess.org/bringing-hope-sufferers-neglected-disease (accessed December 2018).
  14. Bennis et al. BMC Public Health 2018; 18: 358.
  15. Sundar S and Chakravarty J. Int. J. Environ. Res. Public Health 2010; 7: 4267-4277.
  16. Crespillo-Andújar C, et al. Drug Safety 2018; 41:1035–1048.
  17. McGwire BS and Satoskar AR. Q J Med 2014; 107: 7–14.
  18. United Nations Development Programme. UNDP support to the implementation of sustainable development goal 3: Ensure healthy lives and promote wellbeing for all at all ages. Updated June 2018. Available at file:///C:/Users/dul6ml2/Downloads/SDG-3%2520Health.pdf / (accessed December 2018).
  19. Plumer B et al. A simple guide to CRISPR, one of the biggest science stories of the decade. Blog article. Available at https://www.vox.com/2018/7/23/17594864/crispr-cas9-gene-editing (accessed December 2018).
  20. Dy, A. 2017. When will CRISPR get a Nobel prize? 5th October, 2017. Available at https://blogs.plos.org/synbio/2017/10/05/when-will-crispr-get-a-nobel-prize/ (accessed December 2018).