University of São Paulo: Dengue mosquito saliva protein has potential to treat inflammatory bowel diseases

A peptide (small protein) found in greater amounts in the saliva of female Aedes aegypti mosquitoes , was shown to be effective in treating colitis, an inflammatory bowel disease. The mosquito is well known to Brazilians for being the vector of diseases such as dengue, zika and chikungunya. This result was obtained in a survey led by the Institute of Biomedical Sciences (ICB) of USP, in partnership with the Faculty of Pharmaceutical Sciences of Ribeirão Preto (FCFRP) of USP, Butantan Institute and the National Institutes of Health (NIH), of the States United.

Therapeutic administration of a synthetic version of the peptide in sick mice reduced leukocytosis (increase of white blood cells in the blood, which occurs when there is an ongoing infection in the body), the activity of macrophages (host body’s defense cells) and expression cytokines (substances that participate in inflammation and communicate with components of the immune system), as well as nitric oxide levels in the intestine of animals, which resulted in an improvement in clinical signs.

Nitric oxide is a free radical synthesized by several cells in our body, especially macrophages, and plays an important role in inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis.

Scientists have also shown that the pure peptide has its expression increased by 30 times in the salivary glands of female mosquitoes when compared to males, and its secretion in the insect’s saliva induces the production of specific antibodies in animals exposed to mosquito bites.

Because of the properties described above and the fact that there are no similar molecules in other mosquitoes, the scientists named the molecule Ae des -specific MO dulatory PE ptide (AeMOPE-1), something like “ Aedes Specific Modulator Peptide ”. .

Over the past 30 years, several research groups have been studying Aedes aegypti saliva and it has already been possible to demonstrate the role of it and its isolated molecules in allergic reactions, platelet aggregation, vasoconstriction and blood coagulation. But until the conclusion of this work, there was little information about the biological activities of saliva on inflammation and host immunity.

“We used the databases of sialotranscriptomes [set of transcripts – messenger RNAs – from mosquito saliva] as a starting point to identify new molecules such as AeMOPE-1, whose function was previously unknown”, explains Priscila Lara, biologist and first author of the study.

Available data, multiple questions
To Jornal da USP , ICB professor Anderson de Sá-Nunes, Priscila’s advisor, explained that the characterization of molecules in the saliva of Aedes aegypti began in the 1990s and, with it, it was possible to gather information and assemble several databases, which are now available to researchers. “The database already exists. It is up to the scientist to use this information to elaborate his questions and develop in vitro and in vivo research .”

Sá-Nunes coordinates the ICB’s Laboratory of Experimental Immunology (LIE) and, since its creation in 2009, his line of research is focused on the study of immunomodulating activities of the saliva of hematophagous arthropods (invertebrate animals that feed on blood and which are vectors of diseases).

The first stage of Priscila’s doctoral work consisted of showing, in vitro , whether the AeMOPE-1 peptide was present in the mosquito’s saliva, since the only consistent information was from the available databases ( in silico ). After analysis showed that it is more present in the salivary glands of females than in males (and only in adult insects), the researchers identified that the peptide naturally secreted in the mosquito’s saliva was able to trigger a production of specific antibodies in animals exposed to mosquito bites.

Putative immunomodulatory activities (hypothesized in silico) were also investigated. “In previous studies, our group had strong evidence that the gross saliva of the mosquito modulates different cells of the immune system. Therefore, the next step was to see if the synthetic peptide reproduced some of these activities in in vitro assays ”, explains Priscila.

The possible biological activities of the peptide were tested on T lymphocytes (cells responsible for the adaptive immune response), mast cells (cells of the connective tissue and mucosa that participate in inflammatory reactions ) and dendritic cells (cells responsible for processing and presenting antigens), without satisfactory results.

In macrophages, AeMOPE-1 inhibited the production of nitric oxide and cytokines involved in inflammation. Previous studies have shown that nitric oxide and its metabolites are present in the intestine, plasma and urine of sick patients, and their overproduction is associated with increased gastrointestinal inflammation.

More experiments
Given this finding, the researchers decided to test the therapeutic effect of the synthetic peptide (made in the laboratory) in animals with induced inflammatory bowel disease. The experiments were carried out at the Faculty of Pharmaceutical Sciences of Ribeirão Preto (FCFRP) at USP, in collaboration with professor Cristina Ribeiro de Barros and then doctoral student Helioswilton Sales.

The sick mice were divided into two groups. The first of them received the synthetic peptide AeMOPE-1 and the second, only the peptide diluting substance.

Mice treated with AeMOPE-1 showed clinical improvement of the disease when compared to animals that did not receive the peptide. A more detailed evaluation showed less bleeding and diarrhea and better stool consistency in animals treated with AeMOPE-1.

Treatment with the synthetic peptide also reduced leukocytosis in sick animals and, consequently, there was a reduction in lymphocytes, monocytes and neutrophils.

Priscila also evaluated the expression of cytokines present in the animals’ intestines. The analyzes showed a decrease in IL-6 (considered one of the main mediators of the acute phase of inflammation), IFN-γ (cytokine capable of activating macrophages ) and CCL2 (chemokine capable of recruiting a series of inflammatory cells, including macrophages) in animals who received AeMOPE-1. Furthermore, there was a notable reduction in macrophage activity and nitric oxide production in the colon of mice treated with AeMOPE-1, indicating that the peptide may influence the accumulation and/or functionality of these cells in the inflamed intestine.

future applications
“We showed to the entire scientific community that AeMOPE-1 has anti-inflammatory activity in an experimental model of a clinically important disease”, emphasizes Sá-Nunes. “In the future, we plan to propose this molecule as a potential therapy not only for this disease, but for other inflammatory and autoimmune diseases.”

For this to be possible, there is a need to arrive at a viable pharmaceutical formulation and optimize administration routes, and then apply for a patent on the peptide. “The next step is to carry out pre-clinical and clinical trials”, explains Priscila’s advisor.

“We need to establish partnerships and raise funds to advance to the next phases”, completes Sá-Nunes.


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