Ring Stage Survival Assay training – Interview with Naomi Lucchi

WWARN Published Date

Dr Naomi Lucchi, Associate Service Fellow, Malaria Branch, Center for Global Health, Centers for Disease Control and Prevention in Atlanta, discusses her recent Ring Stage Survival Assay training hosted by the Institut Pasteur and WWARN in Phnom Pehn. Naomi explains how this technique can benefit the surveillance of antimalarial drug resistance in East Africa.

What is the scale of the malaria challenge?

The multi-prong approach to prevent and control malaria (using ACTs, LLIN, IRS, improved diagnosis) has led to some progress towards reducing the morbidity and mortality of malaria. However, challenges still exist: the number of deaths due to malaria is still unacceptable for a disease that can be prevented and cured; the challenge of drug resistance is resurging with several countries now demonstrating artemisinin resistance and we don’t have a ready replacement for ACTs.

Why is it important to look at the ring stage of the malaria parasite when studying artemisinin resistance?

Parasites that are sensitive to artemisinin are cleared very quickly from the host’s system; in contrast artemisinin resistant parasites are characterized by a slow clearance rate. Studies have shown that the standard in vitro drug sensitivity assays do not correlate well with therapeutic efficacy studies. Witkoswki et al. demonstrated that in vitro assays carried out using young rings (0-3 hours old) allowed for the distinction between parasites with either slow-clearing phenotype and those that were fast-clearing.

What research are you/your team working on?

Our team is involved in a wide range of malaria research including understanding general malaria parasite biology, development and evaluation of diagnostic tools for malaria, immuno-epidemiology, molecular epidemiology and monitoring antimalarial drug resistance, in which we are involved in therapeutic efficacy studies; in vitro drug sensitivity assays and molecular surveillance of drug resistance.

Why did you want to attend this training course?

I wanted to gain first hand knowledge on the RSA which was developed in the Institut Pasteur in vitro lab. The training gave me first-hand training from Dr. Benoit Witkowski and his team on how to correctly perform this assay; my questions were answered and my skills sharpened. I am now more confident that I can perform this assay in my lab and provide training for others.

What were the overall highlights from the training?

We were able to perform an RSA assay with some field isolates and it was very satisfying to compare our results with those previously obtained by Dr. Witkoswki’s team – especially confirming the same results. Participants’ presentations and interaction allowed me to understand what other labs are working on and compare information.

How are you planning to use the skills you have gained from this training?

We plan to use this assay to determine the artemisinin phenotype of parasites in our on-going domestic malaria surveillance studies; these are imported malaria cases obtained from travellers coming from visits to different endemic countries. In addition, we will help implement this assay (wherever possible) as an additional tool for drug resistance surveillance studies with our partner countries e.g. in Africa or South America.

How important is training like this for the broader malaria community in Kenya and worldwide?

Hands on training like this provides an opportunity to perform this new assay with the experts, giving you an opportunity to correctly learn the technical skills and ask questions related to the assay. Meeting other people you also get an opportunity to share experiences and help each other to hone skills. I think this assay can only be performed in a well-equipped and technically- supported lab; ideally a reference lab in a country or region. For example, in Kenya, this assay can be implemented in the KEMRI centre, however training of technicians and staff to perform the assay would be important.

How do you think this assay can support the global surveillance and monitoring of the spread / emergence of artemisinin resistance?

The use of the RSA for the identification of slow-clearing parasites provides an additional tool for therapeutic efficacy studies in malaria endemic countries. It is not always possible to carry out a therapeutic efficacy study, and the ex vivo RSA can be used to monitor artemisinin resistance and, therefore, provide some data/evidence to the malaria control programs. For example, a country can establish several sentinel sites in the country in regions where malaria is a problem, and every year collect blood samples for the RSA assay and molecular genotyping in order to monitor the circulating parasite phenotypes and genotypes in the country. Important signals on the emergence / spread of resistance.

Why is this particularly important in East Africa?

The emergence of artemisinin failure in Southeast Asia (Cambodia, Thailand, and Viet Nam) makes it imperative that the malaria community in endemic countries closely monitor the situation in their countries. Historically resistance to other antimalarials, such as chloroquine and sulphadoxine-pyrimethamine, spread from Southeast Asia to East Africa first and then spread to other parts of Africa. To date, no study has reported therapeutic failure of ACTs in East Africa. However it is important to determine if slow-clearing parasites evolve and carefully monitor changing patterns in drug sensitivity to artemisinin. We also need to plan therapeutic studies to confirm evolving patterns of resistance. All this evidence will be helpful to support regional and national institutions to make informed and appropriate policy decisions. 

For more information or if you have any questions, please contact Benoit Witkoswki and Didier Menard email: invitro@wwarn.org