Immunotherapy decreases skin sensitivity to cat extract

Evidence-based dosing of maintenance subcutaneous immunotherapy: a contemporary review of state-of-the-art practice

BACKGROUND

Subcutaneous immunotherapy is an effective allergy treatment only if properly dosed. In this article we review the data on the probable effective dose range for subcutaneous immunotherapy and convert the recommended doses into a clinically relevant format.

METHODS

A comprehensive literature search of dose-response subcutaneous immunotherapy studies was done of EBM databases, Medline database, PreMedline, and the National Guideline Clearinghouse for the period 1980-2016. Recommended doses were converted to the volume of allergen extract that should be added to a 5-mL maintenance vial.

RESULTS

A safe and effective dose for subcutaneous immunotherapy is likely 5-20 μg of major allergen per injection. A 0.5-mL injection from a 5-mL maintenance vial containing 0.2 mL of manufacturer's extract of each allergen should reach the lower end of the probable effective dose range for most allergens. A larger volume of extract is required to reach that range when treatment includes cat, dog, or only 1 dust mite. Increasing beyond the commonly prescribed 0.2 mL of manufacturer's extract added to a 5-mL treatment vial is reasonable for nearly all allergens to achieve a maintenance dose higher in the probable effective dose range.

CONCLUSION

Current otolaryngic allergy practice usually escalates patients to 0.5-mL injections from 5-mL maintenance vials containing 0.2 mL of manufacturer's extract of each allergen. With the main exceptions of cat and dog, those injections administered 1 or 2 times per month likely provide an efficacious dose of allergen and are consistent with published guidelines. A larger volume of extract should be considered in certain clinical situations.

Hypoallergenic derivatives of Fel d 1 obtained by rational reassembly for allergy vaccination and tolerance induction

BACKGROUND AND OBJECTIVE

The major cat allergen Fel d 1 represents one of the most important respiratory allergens. Aim of this study was to engineer recombinant Fel d 1 derivatives with reduced IgE reactivity and preserved T cell epitopes for vaccination and tolerance induction.

METHODS

Seven recombinant mosaic proteins were generated by reassembly of non-IgE-reactive peptides of Fel d 1 which contained the sequence elements for induction of allergen-specific blocking IgG antibodies and T cell epitopes. Mosaic proteins were expressed in Escherichia coli using codon-optimized synthetic genes and compared with Fel d 1 regarding structural fold by circular dichroism, IgE-binding capacity, activation of allergic patients' basophils and ability to induce allergen-specific blocking IgG antibodies upon immunization.

RESULTS

Although each of the mosaic proteins had lost the alpha-helical fold typical for Fel d 1, a strong reduction in IgE reactivity as well as allergenic activity in basophil activation assays was only obtained for three constructs, two reassembled fragments (Fel d 1 MB, Fel d 1 MC) and a fusion of the latter two (Fel d 1 MF) in which the cysteines of Fel d 1 MC were replaced by serines. Immunization of rabbits with Fel d 1 MB, MC and MF induced high levels of IgG antibodies that inhibited IgE reactivity of cat-allergic patients to Fel d 1 in a comparable manner as IgG induced with the wild-type allergen.

CONCLUSIONS

We report the development of hypoallergenic reassembled Fel d 1 proteins suitable for vaccination and tolerance induction in cat-allergic patients.

Immunotherapy preparation guidelines, rules, and regulation

Allergen immunotherapy has been used to treat allergic diseases for more than 100 years. In the U.S., the preparation of diagnostic and therapeutic extracts requires the cooperation of the extract manufacturer, who provides the individual allergen concentrates, and the practicing physician who formulates, dilutes, and administers the final patient-specific treatment extract. The guidelines, rules, and regulations for these activities have been established and continue to be developed as progress is made. The molecular characterization and standardization of allergenic extracts has allowed for improvements in defining the potency of these products. In turn, these advances have led to improved dosing regimens and formulation practices. This review will describe in detail some of these interactions and will identify issues that require more attention.

Intralymphatic immunotherapy for cat allergy induces tolerance after only 3 injections

BACKGROUND

Subcutaneous allergen-specific immunotherapy frequently causes allergic side effects and requires 30 to 80 injections over 3 to 5 years.

OBJECTIVE

We sought to improve immunotherapy by using intralymphatic allergen administration (intralymphatic immunotherapy [ILIT]) and by targeting allergen to the MHC class II pathway.

METHODS

Recombinant major cat dander allergen Fel d 1 was fused to a translocation sequence (TAT) and to part of the human invariant chain, generating a modular antigen transporter (MAT) vaccine (MAT-Fel d 1). In a randomized double-blind trial ILIT with MAT-Fel d 1 in alum was compared with ILIT with placebo (saline in alum) in allergic patients (ClinicalTrials.govNCT00718679).

RESULTS

ILIT with MAT-Fel d 1 elicited no adverse events. After 3 placebo injections within 2 months, nasal tolerance increased less than 3-fold, whereas 3 intralymphatic injections with MAT-Fel d 1 increased nasal tolerance 74-fold (P < .001 vs placebo). ILIT with MAT-Fel d 1 stimulated regulatory T-cell responses (P = .026 vs placebo) and increased cat dander-specific IgG(4) levels by 5.66-fold (P = .003). The IgG(4) response positively correlated with IL-10 production (P < .001).

CONCLUSION

In a first-in-human clinical study ILIT with MAT-Fel d 1 was safe and induced allergen tolerance after 3 injections.

Effect of allergen immunotherapy practice parameters on cat extract prescribing patterns, 1993-2009

BACKGROUND

Cat extract allergen immunotherapy (AIT) is an effective treatment for cat allergy. The prescribed dose for cat AIT varies among prescribers, despite published data supporting an effective dose range. The original practice parameter published in December 1996 did not recommend a dose of cat allergen, but updates in January 2003 and September 2007 recommend cat extract dose ranges of 2,000 to 3,000 BAU and 1,000 to 4,000 BAU, respectively.

OBJECTIVE

To describe the prescribing patterns for cat AIT among practicing allergists in a large health care system and the effect of practice parameters on these patterns.

METHODS

A total of 27,788 prescriptions were analyzed to determine the date and amount of maintenance dose cat allergen prescribed. The data were subdivided into periods before and after the 3 published AIT practice parameters.

RESULTS

From January 2003 to September 2007, 1,810 prescriptions (18.0%) were written in the recommended range. From September 2007 to May 2009, 3,143 prescriptions (82.6%) were written in the recommended range. Cat AIT maintenance doses were 1,000 to 4,000 BAU 22.1% of the time before January 2003, 61.8% from January 2003 to September 2007, and 82.6% from September 2007 to May 2009.

CONCLUSIONS

In this large systemic evaluation of cat AIT prescribing patterns, maintenance dose recommendations in the AIT practice parameters were associated with changes in the prescribing patterns for cat AIT. Most prescriptions for cat AIT were inconsistent with recommended doses in the AIT practice parameters between 2003 and 2007. Dosing within recommended ranges improved after 2007, in part due to a widening of the recommended dose range.

A hypoallergenic cat vaccine based on Fel d 1-derived peptides fused to hepatitis B PreS

BACKGROUND

Allergen-specific immunotherapy is clinically effective for the treatment of cat allergy but shows a high rate of side effects.

OBJECTIVE

We sought to engineer recombinant fusion proteins for cat immunotherapy that allow reducing both IgE-mediated and T cell-mediated side effects.

METHODS

Fusion proteins consisting of the hepatitis B virus-derived PreS domain and 2 nonallergenic Fel d 1-derived peptides were expressed in Escherichia coli and purified. IgE reactivity and allergenic activity of Fel d 1 and the fusion proteins were compared by using IgE-binding assays and basophil activation tests in patients with cat allergy. Mice and rabbits were immunized subcutaneously with Fel d 1 and the fusion proteins to investigate the allergenicity of the vaccines and the development of Fel d 1-specific IgG antibodies.

RESULTS

The recombinant fusion proteins showed no relevant IgE reactivity and exhibited more than 1000-fold reduced allergenic activity in basophil activation tests. On immunization of mice and rabbits, the fusion proteins induced Fel d 1-specific IgG antibodies that inhibited the binding of allergic patients' IgE to the allergen without allergic sensitization to Fel d 1.

CONCLUSION

The described recombinant fusion proteins exhibit strongly reduced IgE-mediated allergenic activity, contain less than 40% of the Fel d 1 sequence, and thus lack many of the specific T-cell epitopes. Therefore they should represent safe vaccines for the treatment of cat allergy.

The role of intradermal skin testing in inhalant allergy

OBJECTIVE

To provide an overview of the role of intradermal skin testing (IDST) in inhalant allergy.

DATA SOURCES

A literature search was conducted in MEDLINE to identify peer-reviewed articles related to IDST using the following keywords: skin testing, intradermal, intracutaneous, aeroallergen, and inhalant allergen. In addition, references cited within these articles were also reviewed.

STUDY SELECTION

Articles were selected based on their relevance to the topic.

RESULTS

The use of IDST for inhalant allergy varies widely among allergists. When performed, it is necessary to use a 100- to 1,000-fold dilution from the stock allergen extract. IDST is used routinely in the standardization of extracts in the United States. With a negative skin prick test result, a positive IDST result has low agreement with in vitro and challenge results and generally adds little to the diagnostic evaluation. In contrast, a negative IDST result generally has a high negative predictive value. Only a few inhalant allergens have been evaluated with challenge models for IDST. A summary of the data is also presented in tabular form.

CONCLUSIONS

Most of the literature suggests that with a negative skin prick test result, a positive IDST result adds little to the diagnostic evaluation of inhalant allergy. However, additional studies are necessary using challenge models for less potent and nonstandardized inhalant allergens (molds, trees, dog, weeds).

New approaches to allergen immunotherapy

Allergic diseases are common problems affecting 20% to 30% of the US population. Mast cells and basophils are the primary effector cells mediating allergic inflammation through the triggering of membrane immunoglobulin E receptors (FceRI) with antigen. Allergen immunotherapy is used as one treatment for allergic disease and results in the inhibition of mast cell and basophil responses through unknown mechanisms. In this review, we examine potential mechanisms that could result in blunted human mast cell/basophil functional responses, strategies aimed at using these mechanisms to develop new immunologically based therapies, and recent findings that have broad implications toward our understanding of how mast cells/basophils become desensitized.

Antigen-Induced Reduction in Mast Cell and Basophil Functional Responses due to Reduced Syk Protein Levels

BACKGROUND

The high-affinity IgE receptor, FcepsilonRI, is unresponsive on mast cells and basophils from people in several populations through an unknown mechanism. Similarly, FcepsilonRI-positive basophils from 'nonreleasers' are IgE-unresponsive and are deficient in the tyrosine kinase Syk.

OBJECTIVE

To test the hypothesis that cross-linking FcepsilonRI on mast cells and basophils leads to FcepsilonRI nonresponsiveness through reduction in Syk protein levels.

METHODS

Human mast cells and basophils were used to determine if FcepsilonRI hyporesponsiveness correlated with reduced Syk levels.

RESULTS

It is shown that suboptimal antigen challenge, that did not lead to significant mediator release, induced nonresponsiveness and correlated with reduced Syk. Other IgE-associated signaling molecules were unaffected by the same treatment. The ability of IgE-unresponsive mast cells to regain FcepsilonRI responsiveness is paralleled by increased cellular Syk levels in vitro. The reduction of Syk levels with suboptimal antigen concentrations was calcium independent and mediated through a proteasome-dependent mechanism.

CONCLUSION

These findings confirm and extend our knowledge about a novel regulatory mechanism for maintaining FcepsilonRI in a quiescent state. This mechanism may also explain why low concentrations of allergen given to patients during allergen immunotherapy induce FcepsilonRI nonresponsiveness and therapeutic benefit without inducing systemic anaphylaxis.

Mouse/human chimeric IgG1 and IgG4 antibodies directed to the house dust mite allergen Der p 2: use in quantification of allergen specific IgG

BACKGROUND AND OBJECTIVE

Chimeric mouse/human monoclonal IgG1 and IgG4 antibodies were developed against the house dust mite allergen Der p 2. These chimeric IgG antibodies, hIgG1-Dp2 A and hIgG4-Dp2 A, have the same binding characteristics as the previously reported chimeric hIgE-Dp2 A and are composed of the heavy chain variable domains and light chains of the original murine monoclonal antibody 2B12, whereas the heavy chain constant domains have been replaced by the human IgG1 or IgG4 heavy chain. The expression level of hIgG1-Dp2 A and hIgG4-Dp2 A was 1 and 3.5 microg/mL, respectively.

METHODS AND RESULTS

Since all IgG in these culture supernatants is allergen-specific, they are useful reference reagents and enable the calculation of the amount of allergen specific IgG1 and IgG4 antibodies in absolute IgG amounts. The results obtained with two panels of sera from patients in immunotherapeutic treatment were evaluated and compared in Der p 2 IgE, IgG1 and IgG4 RAST and with reversed IgG4 RAST using labelled purified Der p 2. Close agreement between the results for the two IgG4 assays was found.

CONCLUSION

With these chimeric reference reagents the quantities of isotype specific antiallergen antibodies can be calculated and compared.

Allergen immunotherapy. Review of efficacy and current practice

The modern use of allergen immunotherapy is described. Evidence for efficacy in inhalant allergy and insect sting allergy is reviewed. Current indications for allergen immunotherapy are discussed.

Airborne dust mite allergens: comparison of group II allergens with group I mite allergen and cat-allergen Fel d I

The form in which allergens become airborne is important because it may influence both symptoms caused by allergen exposure and methods used to reduce exposure. The group I allergens from dust mites only become airborne during disturbance and fall rapidly, which is in keeping with their being carried on fecal pellets. Their mean size is approximately 20 microns in diameter. By contrast, the cat-allergen Fel d I is airborne on particles varying from greater than 10 to less than 2 microns in diameter, some of which remain airborne even without disturbance. A second group of mite allergens, molecular weight 14,000, are equally important and are associated predominantly with mite bodies. With a monoclonal antibody-based assay and a cascade impactor, we have investigated the form in which group II mite allergens become airborne. The results reveal that these allergens only become airborne during disturbance and that they fall within 15 minutes. However, the mean size of particles carrying group II allergens appears to be slightly smaller than the mean size of particles carrying group I allergens. In addition, the quantities of group II allergen becoming airborne during disturbance (mean, 26 ng/m3) could not be explained by the quantity found in fecal particles. Thus, group II mite allergens become airborne in a form quite distinct from cat allergens and very similar to group I mite allergens; however, it appears unlikely that fecal particles are the main form in which group II allergens become airborne.

Long-term management of atopic disease in the dog

Canine atopy is a common dermatologic disorder. Because the disease most frequently strikes young dogs, lifetime management strategies are necessary. Consideration must be given to the treatment of pruritus and secondary manifestations of the allergy, such as pyoderma, otitis externa, and seborrhea, to manage these patients successfully. The use of glucocorticoid therapy and hyposensitization are discussed.