We induced in allergic humans the counterpart of murine experimental T-cell tolerance. T-cell lines from cat-allergic humans were used to map T-cell epitopes for the principal allergen of cat dander, Fel d 1. Two peptides of 27 amino acids each were synthesized to contain the dominant epitopes (ALLERVAX CAT). After a safety trial, we carried out a blinded study of the dose required for efficacy. We randomly divided 95 cat-sensitive patients into placebo, 7.5 micrograms, 75 micrograms, and 750 micrograms groups. Patients received a subcutaneous injection weekly for 4 wk. Before and after treatment, patients were exposed in a room inhabited by live cats and scored by nose and lung symptoms. Baseline nasal and lung scores (+/-SEM) were 6.2 +/- 0.56 and 5.4 +/- 0.73 in the 750 micrograms group; 7.8 +/- 0.53 and 4.7 +/- 0.68 in the placebo group. Six weeks after treatment, scores adjusted for baseline differences were reduced in the 750 micrograms group: -2.3 +/- 4.9 and -2.3 +/- 0.59 compared with -0.84 +/- 0.50 and -0.85 +/- 0.62 in the placebo group. The 75 micrograms group showed intermediate effects and the 7.5 micrograms group no effect. Linear trend analysis indicated a significant dose response effect: p = 0.05 for nose and 0.03 for lung symptoms. Allergic side effects occurred an hour or more after the first 750 micrograms dose in 16 of 24 patients but required little or no treatment with one exception. T-cell reactive treatment peptides safely improved allergic responses to cats.

Slow-reacting substance of anaphylaxis (composed of leukotrienes C, D, and E) is released in vitro by the interaction of antigen and IgE antibody on human mast cells and basophils. When we challenged ragweed-sensitive patients intranasally with pollen grains, their clinical response was significantly correlated with the release of the peptide leukotrienes (P less than 0.001). Nonallergic subjects had neither symptoms nor leukotriene release. The leukotrienes were released in a dose-dependent fashion, with a peak mean level of 827 +/- 234 pg per 0.1 ml of a 10-ml nasal wash. High-performance liquid chromatography revealed the presence of leukotrienes C, D, and E, suggesting that nasal cells or fluids had the ability to degrade leukotriene C enzymatically. The in vivo release of these potent inflammatory mediators after exposure to pollen suggests that leukotrienes may have an important role in human allergic reactions.

Although immunotherapy for adults with asthma exacerbated by seasonal ragweed exposure had positive effects on objective measures of asthma and allergy, the clinical effects were limited and many were not sustained for two years.