Antigenic sugars identified for Chagas disease

Chemistry World ^ | 23 July 2013 | Sonja Hampel

[neverdem]

The triatomine beetles that transmit Chagas disease are known as kissing bugs because they tend to feed on people’s faces

Scientists in the US and Spain have synthesised the combinations of sugars from the surface of the Chagas disease parasite that trigger the human immune response to it. This could help establish better diagnostic tests for the disease, and even a vaccine.

Chagas disease is caused by the parasite Trypanosoma cruzi. The parasite is transmitted by contaminated food, blood transfusions and blood sucking beetles commonly known as kissing bugs. After a phase of acute local infection, the disease becomes chronic and can eventually lead to life-threatening heart and digestive system disorders. Already endemic in Latin America, Chagas disease is also becoming more of a health issue in Europe and the US with blood banks now screening for it.

Currently, Chagas diagnosis involves spotting the parasite during microscopic investigation of blood samples or checking to see if antibodies in blood samples of infected patients bind to a lysate of Chagas parasites, but these tests are not very sensitive. As treatment is only effective at the acute stage of infection, better diagnostics are highly desirable.

The surface of the parasite is garnished with unusual sugars, but until now it has not been clear which ones elicit antibodies to the parasite. Sugar chemist Katja Michael and glycobiologist Igor Almeida from the University of Texas at El Paso and colleagues have synthesised combinations of α-galactose sugars from the Chagas parasites’ surface to solve the mystery. Sera of blood samples from infected patients were added to fluorescent immunoassays of the different sugar combinations. The assay revealed the disaccharide Galα(1,3)–Galβ as the immunodominant glycotope on the parasite’s cell surface.

This information will aid the development of better diagnostics for Chagas disease and could even be used to develop a vaccine. ‘Mice immunised with certain sugars survived a lethal dose of the parasites for much longer,’ says Michael.

‘The immune response to Chagas is very complex – there are some infected patients without detectable antibodies, especially in the chronic phase of the disease,’ says Pedro do Brasil from the Institute of Clinical Chagas Research in Rio de Janeiro, Brazil. He says that vaccines against parasites are controversial and that there may be difficulties in studying their clinical effects.

Michael’s group is now synthesising additional sugars from the parasites’ surface to make a combination cocktail vaccine.

References

R A Ashmus et al, Org. Biomol. Chem., 2013, DOI: 10.1039/c3ob40887f

[Right Wing Assault]

Article about the bug and the disease:

http://articles.chicagotribune.com/1995-01-28/news/9502020004_1_chagas-beetle-latin-america

I had to find out how something like that could bite you on the face and you wouldn’t notice. They inject an anesthetic as they bite.

[texas_mrs]

We have bugs here that look very much like these and they are called kissing bugs. Seen them all my life but never knew anyone to be bitten by one. Always see them in my garden but just kept my distance. But after reading up on them this year because there are many, many more this year I am scared to pick the okra. There are 2-6 on every plant out there. One day I was in the kitchen putting away my harvest when I felt something on the top of my head. I brushed it off onto the floor and it was one of these bugs. That’s when I read up on them and found they use your breath, like a mosquito, to guide them to you and it really creeped me out that it was trying to make it’s way to my face!

[neverdem]

Thanks for the link.