Differences in clinical and immunologic reactivity of patients allergic to grass pollens and to multiple-pollen species. II. Efficacy of a double-blind, placebo-controlled, specific immunotherapy with standardized extracts

Comparison of IgE and IgG antibody responses of atopic individuals with sensitization to tree and grass pollens

Sera of atopic individuals with predominant sensitization to either tree pollen (TAs) or tree and grass pollens (TGAs) as well as of nonatopic subjects (NAs) were analyzed for IgE, IgG, and IgG4 antibodies specific for grass pollens allergens. Of 600 atopic individuals with serum IgE antibodies specific for birch pollen allergens, 54% also had serum IgE antibodies specific for grass pollen. The mean titers of IgG antibodies specific for grass pollen proteins were about 10 times higher in the sera of TGAs than those in the TAs and NAs. SDS-PAGE immunoblotting analysis of grass pollen proteins using sera of TGAs, TAs, and NAs with respect to the binding of these proteins with IgE and IgG antibodies in these sera exhibited a similar pattern of variation. Quantitation by enzyme immunoassay of the antibody binding to a recombination grass pollen allergen, rKBG8.3, further demonstrated the elevated IgG antibody levels in TGAs are mainly due to a broader range of specificities, and not to high specific binding to the individual protein. Statistically significant correlation was found between IgE and IgG4 antibodies specific for the Kentucky bluegrass (KBG) extract, but not for the isolated recombinant allergen. These results indicate that the grass pollens elicit a complex array of antibody specificities in both atopics and nonatopics, and that the profile of antibodies specific to the pollen extract and pure allergens differs, suggesting that single grass allergens may be inadequate for replacing grass pollen extracts for immunotherapy.

Interleukin 4 production by CD4+ T cells from allergic individuals is modulated by antigen concentration and antigen-presenting cell type

We have previously shown that CD4+ T cells from allergic individuals are predisposed to produce interleukin (IL)-4 in response to allergens, and that allergen immunotherapy greatly reduced IL-4 production in an allergen-specific fashion. The mechanism that results in the reduction of IL-4 synthesis in treated individuals is unknown, but because clinical improvement during immunotherapy is associated with the administration of the highest doses of allergen, we hypothesized that high concentration of allergen results in the downregulation of IL-4 synthesis in CD4+ T cells. In this report, we demonstrated that CD4+ T cells from allergic donors produced high levels of IL-4 when stimulated with low concentrations of allergen (0.003-0.01 micrograms/ml), particularly when B cell-enriched populations presented the antigen. In contrast, the same responding CD4+ T cell population produced little IL-4 when stimulated with high concentrations of allergen (10-30 micrograms/ml), especially when monocytes were used as antigen-presenting cells (APC). The quantity of IL-4 produced was also found to be inversely related to the extent of proliferation of the CD4+ T cells in response to allergen/antigen; maximal proliferation of CD4+ T cells occurred in response to high concentrations of antigen when IL-4 production was minimal. Antigen presentation by B cell-enriched populations, instead of monocytes, induced less CD4+ T cell proliferation, but induced much greater IL-4 synthesis. Moreover, the addition of increasing numbers of APC (either B cells or monocytes) to cultures containing a constant number of responder T cells resulted in increased T cell proliferation and decreased IL-4 production. These results indicate that the circumstances under which memory T cells are activated, as well as the strength of the proliferative signal to T cells, greatly affect the quantity of IL-4 produced. Thus, our observations that the cytokine profile of allergen-specific memory CD4+ T cells can indeed be modulated by the antigen dose and APC type suggest that methods that preferentially enhance allergen uptake by monocytes and that enhance T cell proliferation will improve the clinical efficacy of immunotherapy in the treatment of allergic disease.

Major allergen Phl p Va (timothy grass) bears at least two different IgE-reactive epitopes

It is established that most grass pollen allergens consist of several isoforms of which the function is mainly still unknown. A number of these allergens belonging to group V have been cloned, sequenced, and expressed. Antigenic sites and IgE-reactive epitopes of the major allergen Phl p Va, are unknown. We have identified the complete cDNA sequence of a Phl p Va isoallergen by immunoscreening of a timothy grass pollen cDNA library and mixed oligonucleotide primed amplification of N-terminal cDNA. Additionally, we found an incomplete isoallergenic cDNA clone of the same protein. Immunoreactivity of the fusion proteins with patients' sera and monoclonal antibodies showed that the clones represent group Va allergens. Comparison of deduced amino acid sequences with published sequences of Lol p V and Poa p IX revealed a homology of 81.1% and 86.9%, respectively. With affinity-purified IgE antibodies recognizing the recombinant fusion protein, we can demonstrate the existence of a common group V IgE-reactive epitope. By construction of both an N-terminal and a C-terminal peptide of the complete Phl p Va and cross-inhibition, we identified at least two different IgE epitopes. Eleven patients showed variable IgE immunoreactivities to both IgE-reactive epitopes.

Booster immunotherapy (BIT)

This study tries to answer two questions: 1) how long does the therapeutic effect of successful immunotherapy (IT) last after termination of the treatment? and 2) what is the best treatment for recidivist patients? To answer the first question, we asked 108 patients with rye/grass pollen allergy who had previously undergone IT for 3-4 years and had responded well to treatment to complete a questionnaire on the course of their recovery after termination of the therapy. Evaluation of the answers revealed a recidivist rate of approximately 30% in the first 3 years. According to our results, the risk of a relapse after this period seems to be low. To answer the second question, we included 40 patients suffering from type I allergy to grass/rye pollen in a clinical study. Each of them had previously undergone specific IT with a grass pollen extract mixture and had terminated this therapy after 3-4 years practically free of symptoms during the grass pollen season. As the symptoms returned and increased from year to year after the end of IT, new therapeutic steps had to be considered. We investigated the efficacy of a short preseasonal injection treatment called "booster immunotherapy" (BIT). BIT was performed with two different injection-regimens, a low-dose schedule comprising six injections and a high-dose schedule with 11 injections, in both cases administered as a build-up regimen. In the next pollen season, 28/40 (70%) patients reported strong improvement or even complete remission of the allergy symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)

Safety considerations in assessing the role of immunotherapy in allergic disorders

Specific immunotherapy (SIT) is accepted as an effective treatment of allergic diseases when high quality extracts are used. However, this form of treatment can cause untoward reactions among which systemic reactions are the most severe. Although life-threatening reactions are rare and deaths exceptionally reported, SIT should be prescribed by allergists to patients with well defined characteristics, and administered with care by (or under the close supervision of) physicians trained to deal rapidly with the reactions. Reactions with standardised extracts occur mostly during the dose increase phase but they can be prevented using adapted schedules and premedication. During maintenance injections or when vial batches are changed, standardised extracts of known shelf-life usually result in a low rate of systemic reactions. Patients with asthma are more prone to develop systemic reactions, and allergens should not be administered to patients with a forced expiratory volume in 1 second (FEV1) under 70% of predicted or in those who have unstable or symptomatic asthma. Systemic reactions may be observed with all allergens and allergenic preparations although it appears that high molecular weight extracts may be safer.

T cell clones specific for Bet v I, the major birch pollen allergen, crossreact with the major allergens of hazel, Cor a I, and alder, Aln g I

Tree pollens are responsible for type I allergies during the flowering season in spring. Pollens from birch, hazel and alder constitute the most important allergen sources in this respect in the northern hemisphere. Human IgE antibodies, specific for the major allergens of these pollens, are known to crossreact, and in general every tree pollen allergic patient is sensitized to these three pollen allergens. In this study we investigated eight T-helper cell clones (CD3+, CD4+, TCR alpha/beta) with specificity for Bet v I, the major birch pollen allergen, as proved by reactivity with purified natural as well as with recombinant allergen. The T cell clones were used to investigate common T cell epitopes of the Bet v I molecule with Cor a I, the major allergen of hazel pollen and Aln g I, the major allergen of alder pollen. All eight T cell clones reacted with all three proteins with different intensity. Moreover, three T cell clones, which were known to react with immunodominant T cell epitopes on the Bet v I molecule, were tested for reactivity with dodecapeptides synthesized according to the corresponding homologous regions of the Cor a I and Aln g I sequence. All the peptides induced strong T cell proliferation, indicating the existence of multiple cross-reacting epitopes. These findings will have an impact on the production of vaccines for immunotherapy of tree pollen allergies.