SAN ANTONIO – Oral and sublingual immunotherapy strategies aren’t yet ready for prime time, but they continue to show promise for inducing tolerance in children with food allergies.
Oral immunotherapy
Preliminary findings from a study of low-dose oral immunotherapy (OIT) for peanut allergy, for example, suggest this approach is an effective early-intervention strategy, Dr. Brian Vickery reported at the annual meeting of the American Academy of Allergy, Asthma, and Immunology.
In a randomized, controlled trial involving 49 peanut-sensitized children aged 9-36 months, both low- and high-dose immunotherapy resulted in a significant reduction in both peanut-specific IgE (psIgE) and skin prick test values after a median of 19 treatments, said Dr. Vickery, who is a pediatric allergist and immunologist at the University of North Carolina at Chapel Hill.
The degree of change was similar in those treated with low-dose and high-dose oral immunotherapy. The low dose slope coefficient for psIgE was -2.53 for the low dose group, compared with –1.63 for the high-dose group; and the low dose slope coefficient for the skin prick test was –0.007, compared with –0.009 for the high-dose group, he said.
Of eight subjects who met the criteria for tolerance evaluation as of the time of Dr. Vickery’s presentation, seven had successfully achieved tolerance and now eat peanut ad lib, he noted.
Study subjects were enrolled within 6 months of their index reaction or demonstration of psIgE greater than 5 kUA/L. After randomization to the low- or high-dose treatment group, they underwent serial analysis of immune responses. After at least 1 year of maintenance oral immunotherapy, clinical tolerance was assessed using a double-blinded placebo-controlled oral food challenge based on predefined clinical and immunologic benchmarks.
The findings are preliminary but suggest that early-intervention peanut oral immunotherapy is a feasible strategy. In addition, low-dose oral immunotherapy – using a 10-fold lower dose of peanut protein (the equivalent of about 1 vs. 10 peanuts comprised the maintenance doses in the low- and high-dose groups, respectively) may be sufficiently immunomodulatory in young children with newly diagnosed peanut allergy, Dr. Vickery said during a press briefing at the meeting.
Furthermore, the findings suggest that such an approach is technically possible in that young children can be recruited and treated in this manner, he noted.
Dr. Robert A. Wood, who is chief of the division of allergy and immunology at Hopkins Children’s Center at Johns Hopkins University, Baltimore, and who also presented oral immunotherapy data, noted during the press briefing that the approach used in this study "is sort of seizing on the opportunity that maybe kids early in life, when their allergy is less established, may be more amenable to treatment."
Peanut allergy that manifests in early childhood typically intensifies over 5-10 years, he explained.
The findings, however, are very preliminary.
"In order for us to really understand the impact of these two doses, we will need to assess all of the endpoints in all of the subjects who are currently enrolled, and then unblind the study at the end of it, and do an assessment to really understand whether low or high dose therapy was effective," Dr. Vickery said.
Sublingual immunotherapy
Sublingual immunotherapy (SLIT) is another promising intervention for food allergic children, according to findings from a study presented by Dr. A. Wesley Burks, who is chair of pediatrics at the University of North Carolina at Chapel Hill and physician in chief of N.C. Children’s Hospital, also in Chapel Hill.
Interim data from that study of 44 patients showed that after 36 months of dosing, peanut SLIT–induced clinical tolerance with concurrent changes in skin testing and peanut-specific immunoglobulin levels.
Of 11 patients who completed 36 months of dosing, 6 passed a peanut oral food challenge to 5,000 mg of peanut protein. The remaining five patients ingested a median of 3,750 mg of peanut protein. After SLIT discontinuation for 1 month, five of six passed an identical oral food challenge, suggesting clinical tolerance.
Children in this study were aged 2-11 years. All received open-label peanut SLIT with a daily maintenance dose of 2 mg of peanut protein, Dr. Burks said.
The findings do not say anything about long-term efficacy of SLIT, but they do show that tolerance can be induced, at least in the short term, Dr. Burke said.
Predictors of tolerance induction
Another study presented by Dr. Burke shed some light on factors associated with induction of tolerance, namely basophil hyporesponsiveness and a low peanut IgE:IgG4 ratio.
In that study of 12 patients who received SLIT and 27 who received OIT, 5 (41.7%) and 18 (66.7%), respectively, developed tolerance following immunotherapy. In the SLIT subjects, basophil responses were significantly lower among those who developed tolerance than among those who did not. This was true for each of the 4 log-fold dilutions of peanut antigen used in the assay, Dr. Burks said.