The vast majority of tolerant subjects (91.3%) had a peanut-IgE:IgG4 ratio below 0.92, compared with only 20% of nontolerant subjects.
All subjects underwent double-blind placebo-controlled food challenges to assess desensitization while they were on daily immunotherapy, and those passing the challenge ceased daily therapy and avoided all peanut products for 4 weeks. At 4 weeks, a second food challenge was administered.
The findings suggest that basophil suppression and the balance of antigen-specific IgE and IgG4 may be important in the development of tolerance following peanut immunotherapy, Dr. Burks said.
Long-term immunotherapy outcomes
One missing piece of the immunotherapy puzzle are data on long-term outcomes, as most studies report only 1-2 year outcomes. Another study presented by Dr. Wood, however, takes a step toward filling the gap – with underwhelming results.
The small study looked at long-term outcomes following milk oral immunotherapy in children, and showed that at 4.5 year follow-up, only about 25% of 32 patients were tolerating at least one serving of milk daily and 25% were consuming only trace amounts or were on strict avoidance mainly because of reactions. About 40% of patients were having frequent reactions to milk, 20% had required epinephrine for reactions, and 30% had experienced systemic reactions.
The patients were treated in two studies during 2006 and 2007 with a dose escalation to 500 mg of milk protein over about 8 weeks, followed by 3 months of maintenance dosing. Dietary milk was introduced in amounts ranging from 500 to 4,000 mg daily based on the results of a double-blind placebo-controlled food challenge.
Of note, one subject who passed a 16-g challenge without symptoms went on to become reactive again and now consumes only minimal milk, Dr. Wood said
In fact, one of the surprising things in this study was that some of the more dramatic failures long-term were in children who had achieved success in the initial studies.
These were children who "looked like absolute successes" at the end of the study, because there were tolerating large amounts of milk, he said.
"We really thought – and we hesitate to use the word "cure" – that they were about as close to cured as we could really imagine. And now, 3-5 years later, they are having anaphylactic reactions and are back on strict milk avoidance," he said.
As a result, the excitement following the initial studies has waned somewhat.
"We had a very high degree of optimism. I’m not saying we lost that optimism, but it is certainly tempered a bit by looking at where these kids now stand 3-5 years out," he said, concluding that more research with respect to long-term outcomes of food oral immunotherapy is needed, including investigation of whether longer treatment would improve outcomes, and whether certain factors can predict response and failure.
"The most important message is that this sort of adds another caveat about why we need more research before we can bring this out to our patient population. A message that I think all of us who are doing this research have come to agree upon is that we need long-term follow-up and that letting these kids go at the end of the study is not the end of the story."
Taken together, the findings of these studies underscore a need for more research regarding SLIT vs. OIT, higher vs. lower dosing, and treatment duration, as well as long-term follow-up, the investigators agreed.
"The message is that what we are doing so far is very encouraging, but it’s not the final answer. Where we need to be to bring this out to the general public is several steps beyond where we are now," Dr. Wood said.
The investigators reported having no disclosures.