Analysis of cytokine expression in avian peripheral blood in response to malaria infections
(2019) MOBM02 20192Degree Projects in Molecular Biology
- Abstract
- The outcome of malaria infections in humans and mice, including the symptoms experienced by the host, the clearance of the parasite, and the host survival; is highly dependant on the balance between inflammatory and anti-inflammatory immune mechanisms. Cytokines, which are signalling molecules involved in cell-cell communication, play a central role in such balance. Given the limited knowledge about cytokines in the avian immune response against malaria, I aimed to measure cytokine expression in Eurasian siskins (Spinus spinus) experimentally infected with Plasmodium relictum (lineage SGS1), and to compare the cytokine expression levels relative to uninfected birds. Peripheral blood was collected at different sampling days post-inoculation... (More)
- The outcome of malaria infections in humans and mice, including the symptoms experienced by the host, the clearance of the parasite, and the host survival; is highly dependant on the balance between inflammatory and anti-inflammatory immune mechanisms. Cytokines, which are signalling molecules involved in cell-cell communication, play a central role in such balance. Given the limited knowledge about cytokines in the avian immune response against malaria, I aimed to measure cytokine expression in Eurasian siskins (Spinus spinus) experimentally infected with Plasmodium relictum (lineage SGS1), and to compare the cytokine expression levels relative to uninfected birds. Peripheral blood was collected at different sampling days post-inoculation (dpi): at 8, 20 and 36 dpi; and the parasitemia was also recorded. Four cytokines were initially targeted for expression analyses using quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR); Interferon gamma (IFN-γ), Interleukin-6 (IL-6), Interleukin-5 (IL-15) and Transforming Growth Factor - beta 2 (TGF-β2). Only IL-15, a pro-inflammatory cytokine, fulfilled the criteria for reliable quantification after standardization. A negative relationship between parasitemia and IL-15 expression was found at 8 dpi, where highly parasitized birds express less IL-15. This might be related to the high exposure to antigens experienced by the host in high parasitemia infections, which would trigger an excessive immune response, and thus individuals with high parasitemia react by lowering the expression of pro-inflammatory cytokines as IL-15. Alternatively, the antigens themselves might modulate the pro-inflammatory response of the host. The IL-15 expression tended to be higher in infected siskins at 20 dpi where after the parasitemia decreased sharply. Interestingly, IL-15 has been related to malaria parasite clearance in humans and murine models, so it is likely that IL-15 has a role in controlling the parasitemia also in birds. Finally, a positive relationship between parasitemia and IL-15 was found at 36 dpi, which is when adaptive responses are taking place. As IL-15 is related to antibody production and B cell proliferation, IL-15 expression might be responding to the presence of the parasite in the cases where the infection has not been controlled yet. (Less)
- Popular Abstract
- Immune responses to malaria in birds
GENERAL INTRODUCTION Malaria, a parasite that infects and reproduces in the blood, can also infect birds. But differently from humans and mice, we do not know how the immune system of birds faces the infection. Therefore, I studied the immune response of European siskins (Spinus spinus), which were experimentally infected with malaria in the laboratory. Namely, I examined the changes of Interleukin-15 (IL-15) in siskins response to malaria, which is a protein involved in the immune response as observed in humans and mice.
One of the main strategies of the immune system when facing malaria, is to trigger an inflammatory response. Inflammation causes fever and accelerates the action of the immune... (More) - Immune responses to malaria in birds
GENERAL INTRODUCTION Malaria, a parasite that infects and reproduces in the blood, can also infect birds. But differently from humans and mice, we do not know how the immune system of birds faces the infection. Therefore, I studied the immune response of European siskins (Spinus spinus), which were experimentally infected with malaria in the laboratory. Namely, I examined the changes of Interleukin-15 (IL-15) in siskins response to malaria, which is a protein involved in the immune response as observed in humans and mice.
One of the main strategies of the immune system when facing malaria, is to trigger an inflammatory response. Inflammation causes fever and accelerates the action of the immune system. IL-15 is a protein promoting inflammation, and accordingly, I found higher IL-15 levels in infected birds compared to uninfected birds. However, at day 8 after the infection (which is when the parasite is reproducing in the blood, Figure 1), birds having more parasites circulating in their blood produce less IL-15.
A high abundancy of parasites will cause a more severe inflammatory response, which could lead to the bird´s death if not controlled. Therefore, as observed in mice and humans, birds having an excess of parasite circulating in their blood limit the production of pro-inflammatory proteins, which might include a reduction in IL-15 levels. Moreover, some parasitic particles released by the parasite while reproducing can also block the inflammatory response, similar to human and mice models.
At day 20 after the infection, the parasite population was greatly reduced in the siskins blood. This is the day point when IL-15 levels were the highest in infected siskins compared to uninfected siskins. IL-15 has a role on clearing the infection in mice and might therefore have a role in siskins too. Finally, at day 36 after the infection, there is still parasitic presence in the siskins blood, but it is very low. Nevertheless, IL-15 seems to respond to this remnant parasitic presence. At this day point, siskins having more circulating parasites have higher levels of IL-15, which is likely due to its function in antibody production.
Conclusions
A first insight on the immune system in birds has revealed that the IL-15 production is enhanced by malaria parasites. Also, that IL-15 production changes depending on the timepoint analysed during the infection, and in response to parasitic abundance in the blood. Future studies can focus in measuring the production of more anti and pro-inflammatory proteins to have a more complete picture of the avian immune response to malaria.
Master’s Degree Project in Biology/Molecular Biology/General 30 credits 2019
Department of Biology, Lund University
Advisor: Staffan Bensch
Head of MEMEG, Biologiska institutionen, Department of Biology (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/8998936
- author
- Esteban Henao, Maria Camila
- supervisor
- organization
- course
- MOBM02 20192
- year
- 2019
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 8998936
- date added to LUP
- 2019-12-20 13:43:46
- date last changed
- 2019-12-20 13:43:46
@misc{8998936,
abstract = {{The outcome of malaria infections in humans and mice, including the symptoms experienced by the host, the clearance of the parasite, and the host survival; is highly dependant on the balance between inflammatory and anti-inflammatory immune mechanisms. Cytokines, which are signalling molecules involved in cell-cell communication, play a central role in such balance. Given the limited knowledge about cytokines in the avian immune response against malaria, I aimed to measure cytokine expression in Eurasian siskins (Spinus spinus) experimentally infected with Plasmodium relictum (lineage SGS1), and to compare the cytokine expression levels relative to uninfected birds. Peripheral blood was collected at different sampling days post-inoculation (dpi): at 8, 20 and 36 dpi; and the parasitemia was also recorded. Four cytokines were initially targeted for expression analyses using quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR); Interferon gamma (IFN-γ), Interleukin-6 (IL-6), Interleukin-5 (IL-15) and Transforming Growth Factor - beta 2 (TGF-β2). Only IL-15, a pro-inflammatory cytokine, fulfilled the criteria for reliable quantification after standardization. A negative relationship between parasitemia and IL-15 expression was found at 8 dpi, where highly parasitized birds express less IL-15. This might be related to the high exposure to antigens experienced by the host in high parasitemia infections, which would trigger an excessive immune response, and thus individuals with high parasitemia react by lowering the expression of pro-inflammatory cytokines as IL-15. Alternatively, the antigens themselves might modulate the pro-inflammatory response of the host. The IL-15 expression tended to be higher in infected siskins at 20 dpi where after the parasitemia decreased sharply. Interestingly, IL-15 has been related to malaria parasite clearance in humans and murine models, so it is likely that IL-15 has a role in controlling the parasitemia also in birds. Finally, a positive relationship between parasitemia and IL-15 was found at 36 dpi, which is when adaptive responses are taking place. As IL-15 is related to antibody production and B cell proliferation, IL-15 expression might be responding to the presence of the parasite in the cases where the infection has not been controlled yet.}},
author = {{Esteban Henao, Maria Camila}},
language = {{eng}},
note = {{Student Paper}},
title = {{Analysis of cytokine expression in avian peripheral blood in response to malaria infections}},
year = {{2019}},
}