By Randall Osborne
Arthur Krieger has made a discovery of "alarming" simplicity, and he plans to take it to the marketplace.
Krieger is president and chief scientific officer of CpG ImmunoPharmaceuticals Inc., of Iowa City. The company operates from his office at the University of Iowa College of Medicine, and has no employees.
"Right now, we're virtual," said Krieger, an associate professor of internal medicine, "but we have over $6 million in the bank."
Qiagen G.m.b.H., of Hilden, Germany, contributed seed money for a $6.3 million round of venture capital financing, completed last month. CpG also has secured long-term loans for "a very substantial amount" to be disclosed in the next few weeks, Krieger said.
Funding "hasn't been a problem for us," Krieger said. The company was incorporated in March and has a subsidiary in Germany.
Krieger and his colleagues found that the immune system sniffs out bacteria and viruses not only by the invaders' protein coats, but by patterns in the microbes' DNA.
"Vertebrate DNA and bacterial DNA have a subtle chemical difference," Krieger said. "This had been realized for many years, but apparently it hadn't occurred to anyone previously that our immune system might recognize the difference."
The workings of the human immune system seem remarkable enough already. It scrutinizes the cell walls of invaders for telltale marks. It breaks up the invading cells with macrophages, and shows off the pieces to other fighters, who rush to the scene.
Now, Krieger and his University of Iowa colleagues have found that the microbes' DNA sound an "alarm" as well.
Placing the bacterial DNA with immune system B cells, they watched the B cells reproduce madly. DNA from mammals sparked no such response. Experimenting further, the researchers determined that a particular sequence of nucleic acids in DNA strands triggered the danger signals: a cytosine followed by a guanine, which is seldom found in mammalian DNA but is common in bacterial DNA.
What's more, the relatively few cytosine-guanine pairs found in mammalian DNA are chemically modified by a process called methylation, which bestows them with molecular crowns. Those in bacterial DNA are not methylated.
"DNA is taken up into B cells and other cells," Krieger said. "They take up all DNA, not just bacterial DNA, but inside the cell, there's a screening process."
Human System Slow To See Invaders
The difference between the two DNA types is the factor that alerts the human immune system's B cells that they are dealing with a foreign invader rather than friendly DNA. In puberty, for example, the body begins making new proteins that are unopposed by the immune system. When bacterial proteins show up, with their unmethylated cytosine-guanine pairs, the response changes — though not right away, which can be unfortunate for the body.
"What we're realizing," Krieger said, "is that antibodies and other specific parts of the immune system take a few weeks to be called into play. You need an early warning system that can tell rapidly when [the body] is being affected."
Enter the "CpG motif," which Krieger has named the cytosine-guanine dinucleotide. By creating DNA with the motif, scientists can jump-start the immune system. "If you want to make a vaccine, you make synthetic DNA and it works 10 to 100 times better," Krieger said. "If you want to treat a tumor, you inject the DNA into the cancer."
A series of punches attacks the tumor, Krieger said.
"You give the DNA first," he said. "That activates the immune system, which causes it to go into a hypervigilant state, looking for things to destroy. Then you give the antibody for the tumor. When you've revved up the system and inject the antibody, the immune system goes nuts killing [the cancer cells]. It's like saying, 'Kick me.'"
Krieger said his researchers took a cue from IDEC Pharmaceutical Corp.'s work with its anti-CD20 monoclonal antibody for non-Hodgkin's lymphoma. Using mice and "a different antibody that's basically equivalent, we get 80 percent survival rates."
San Diego-based IDEC's drug, Rituxan (rituximab), if approved, would be the first anticancer antibody. An FDA advisory panel has recommended approval and the FDA has asked IDEC for manufacturing data prior to marketing clearance. (See BioWorld Today, Sept. 2, 1997, p. 1.)
Clinical Trials Targeted For Canada
The approach works for asthma, too, since the allergic-type immune response is shut off by the response that is prompted by the unmethylated cytosine-guanine pairs.
Krieger is putting together the paperwork for the first stage of an investigational new drug application for a hepatitis B vaccine. This will be submitted first to Canada's Health Protection Branch, he said. Heather Davis, associate professor at the University of Ottawa, is director of vaccine research for the company, and management is being recruited.
Studies of the hepatitis B vaccine in monkeys were "pretty astonishing," Krieger said. Ordinarily, three shots of the vaccine would provide 90 percent protection. By adding a low dose of properly made DNA, all 55 monkeys developed protective antibody levels after a single dose.
"We talked to the FDA, and informally they've told us regulatory approval will be pretty easy," Krieger said. "We would just be adding a low dose of DNA to an already- approved product. We'll be able to produce it for under 10 cents per dose."
Broad patents covering the technology have been filed by the University of Iowa Research Foundation. The company opened a subsidiary in Germany in August and has collaborations with the Ottawa Civic Hospital Loeb Research Institute and the University of Ottawa; the University of Iowa; Auburn University, of Auburn, Ala.; and several academic centers in Europe.
Krieger, a physician, earned his medical degree at Washington University, in St. Louis, worked as a researcher for five years at the National Institutes of Health, and in 1991 became an assistant professor at the University of Iowa, where he is now an associate professor.
"I've never done this before," he said of his venture into biotechnology. "I'm having a blast. There's really no other immunotherapy that's gotten to this point." *