Researchers at the Max Planck Institute of Psychiatry are taking advantage of the Swedish Human Proteomic Resource program to obtain antibodies against 200 cerebral spinal fluid proteins, which they plan to turn into an array to study depression, anxiety, schizophrenia, Alzheimer's disease, and other brain disorders.
The HPR program, which is part of the Human Proteome Organization's Human Antibody Initiative, has been soliciting applications for projects that need a lot of antibodies against human proteins, explained Christoph Turck, a professor of biochemistry at Max Planck who is leading the effort to develop the CSF array.
"It's free of charge. The only condition is they are using the antibodies themselves to do immunohistochemistry, and they could also use whatever antibodies they're interested in to do similar things as what we're doing," said Turck.
Even though the CSF antibodies are free through the HPR program, which is funded by the Knut and Alice Wallenberg Foundation, it will still take about $12,000 to put the antibodies onto an array such as the ones made by Luminex, said Turck. That cost doesn't include the light reader necessary to read the multiplexed Luminex arrays, which costs more than $120,000, he added.
"It's free of charge. The only condition is they are using the antibodies themselves to do immunohistochemistry, and they could also use whatever antibodies they're interested in to do similar things as what we're doing."
For the array, Turck and his colleagues picked 200 CSF proteins for antibody development out of a list of 400 CSF proteins that they had identified through their work in trying to find biomarkers for brain disorders. They chose proteins that were exclusively expressed in the brain, as well as proteins that were involved in signaling cascades. CSF proteins that they left out included serum proteins involved in inflammation.
Turck's application to the HPR for antibody development was one of about a dozen applications that were accepted by the program last spring.
The antibodies against CSF proteins are in the production process now, Turck said.
"They're immunizing those chickens right now, and they tell me by the end of this year they'll have the antibodies," he said.
Currently, there are no commercially available arrays that contain CSF antibodies, Turck told ProteoMonitor. He added that it is possible that he and the HPR would commercialize the CSF antibody array that he plans to develop.
"Definitely, there would be a market for such a thing, especially if these antibodies will provide us with biomarkers to distinguish patient phenotypes," said Turck. "I haven't seen any arrays out there with regard to brain disorders."
Turck said he does not have any experience in making arrays.
"If I go with this Luminex system, that's supposed to be relatively simple," he said. "Alternatively, I could enter into a collaboration with an [undisclosed] colleague in Heidelberg who makes very-high-density arrays."
Up until now, Turck and his colleagues have used 2D gels and iTRAQ labeling to study human CSF fluid, as well as brains from mouse models of anxiety.
The Max Planck Institute of Psychiatry is unusual in that it has established a large CSF bank from psychiatric patients who are carefully phenotyped and documented, said Turck.
"Lumbar puncture [to obtain CSF] is done more frequently here than it is in the US," said Turck. "They carry it out on a routine basis in neurology and also in psychiatry."
Last month, a paper was published in the European Archives of Psychiatry and Clinical Neuroscience describing Turck's team's work analyzing the proteomes of CSF samples from unmedicated patients with depression who had attempted suicide.
When the researchers used 2D gels to compare the CSF of suicide attempters with the CSF of depressed patients who had not attempted suicide, they found one protein difference. The protein, which was not identified, had a molecular weight of 33 kD and an isoelectric point of 5.2.
The proteomic analysis of suicide attempters is just a small part of the work that is going on in Turck's lab to try to identify biomarkers for brain disorders.
"We're doing a lot with people suffering from depression, unipolar and bipolar disorder, as well as schizophrenia, and people suffering from psychosis versus others not suffering from psychosis," said Turck. "Some depressed patient groups respond to treatment with antidepressants in a very rapid manner. Others don't respond at all to the same antidepressant. We're trying to see what the difference is."
In addition to studies of human CSF, Turck's research group is studying mouse models of anxiety. The researchers found an enzyme called glyoxalase-I that is consistently expressed more in mice with low-anxiety behavior than in mice with high-anxiety behavior.
"The enzyme is responsible for the detoxification of methyl glyoxal, which is very toxic if the cell doesn't get rid of it it modifies arginines and lysines in proteins," said Turck. "It's hard to know what this enzyme has to do with anxiety or depression, but when you have too little of this enzyme, the mouse is very anxious."
Turck noted that the CSF antibody array will allow researchers to use a lot less sample when conducting proteomic experiments.
"With an antibody array, you can get away with a lot less material," he said.
The array will also allow multiplexed, quantitative comparisons between CSF fluids.
"Right now, with iTRAQ, we can label up to four different CSF fluids," said Turck. "That's not as much as you can do with an antibody array. With the array, we have to expect that there'll be a number of proteins that will change their expression levels. Hopefully we can use those as biomarkers."
Tien-Shun Lee ([email protected])