Travel Report: Nicolas Salcedo, Biological Sciences

September 11, 2017

Nicolas Salcedo, a PhD candidate in Biological Sciences, received a Graduate International Research Travel Award (GIRTA) to further his research in Brazil. His report: 

One remarkable aspect of insects’ biology is their immune system. Usually, we divide immunity into two branches: the adaptive immunity and the innate immunity. In the former, almost any pathogen (or molecule) will trigger an immune response, and a specific “memory response” will be constructed against this pathogen, so that a secondary infection will elicit a stronger and more explicit immune response.

Innate immunity on the other hand has only a few and well conserved pathogen recognition molecules that will trigger an immune response, and no “memory response” will be created. Insects only possess an innate immune system, which is divided into a handful of processes. Incredibly, this simpler immune system is robust enough to insure insect survival.

In my PhD research I aim to understand how this is possible by studding the immune system of the kissing bug Rhodnius prolixus (R. prolixus). This insect, which transmits the parasite that causes Chagas disease in humans, is believed to have a reduced immune system. My analysis of the genome of R. prolixus challenges this idea, showing that the main components of the insects’ immune system are also present in R. prolixus.

In R. prolixus, one of the main innate immune pathways is known as IMD (IMmune Deficiency). This pathway was reported as incomplete, and believed to be non-functional, a very rare instance that deviates from the known immune system composition for most insects. According to my bioinformatics analyses, the majority of the pathway is, in fact, complete. To confirm that IMD genes are part of the immune system, a direct functional test of each gene in the pathway needs to be done.

The GIRTA allowed me to collaborate and be trained in one of the most renowned tropical disease centers in the world. I stayed in the city of Belo Horizonte, Brazil, from February to May 2017, working in the Vector Behaviour and Pathogen Interaction Group at Fundação Oswaldo Cruz, under the supervision of Dr. Alessandra Guarneri. In her lab, the function of individual genes is assessed by repressing the expression of each targeted gene using a dsRNA silencing technique.  The main objectives of my visit were to: learn rearing techniques for kissing bug lab colonies, and test the functional role of the IMD pathway genes I discovered.

After practicing on over a hundred insects, I was ready to perform my experiments. First, the insects feed from a chicken or an artificial blood feeder, and 12-15 days later the kissing bugs will molt into a new developmental stage. I then injected dsRNA for each of my target genes to the induce silencing. Finally I exposed the insects to bacteria to evaluate their immune response at different time points post exposure. This was a hard and slow process, but in the end was quite rewarding, due to the large amount of data I was able to collect. When I was not in the insect colony or dissecting insects in the lab, I was eating delicious food, enjoying the Carnaval, or visiting the vast number of museums in Belo Horizonte.  

The samples I obtained from this experiment are currently being processed in our lab in SFU. We are currently measuring the silencing extent, and how these levels of silencing correlate with the expression level of immune molecules. This experience helped me to improve the experimental design of my experiments, allowed our lab to start a Rhodnius prolixus colony here at SFU, and strengthened our relations with Dr. Guarneri’s lab, as well as with other labs in Brazil. I sincerely am sincerely grateful for the opportunities and learning experiments the GIRTA granted me. 

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