Safety, efficacy and repeatability of a novel house dust mite allergen challenge technique in the Fraunhofer allergen challenge chamber

BACKGROUND

Efficacy testing of immunotherapy in field studies is often hampered by variation of airborne allergens. Standardized allergen exposure in challenge chamber settings might be an alternative. Therefore, we developed a universal technique to create an atmosphere loaded with allergen particles of adjustable size from aqueous solutions of licensed allergen extracts.

OBJECTIVE

The aim of this study was to apply this technique and test the safety and efficacy of challenges with house dust mite (HDM) allergen in the Fraunhofer allergen challenge chamber.

METHODS

Aerosol particles carrying HDM allergen were produced by spray-drying of an aqueous solution containing HDM allergen and lactose. In a monocenter, placebo-controlled, single-blind, dose-escalation pilot study, 18 subjects with perennial allergic rhinitis and sensitization to HDM were exposed to HDM allergen for 4 h at either 250, 500, 1000 SQE/m³ or lactose alone (0 SQE/m³ ) 7 days apart. The dose of 500 SQE/m³ was repeated to investigate reproducibility. Total nasal symptom score (TNSS) was the primary endpoint.

RESULTS

Exposure to HDM increased TNSS (mean ± SD) to 3.4 ± 1.8, 3.3 ± 2.1, and 3.6 ± 2.0 at 250, 500 and 1000 SQE/m³ , respectively, while lactose alone did not change TNSS (0.7 ± 0.6). The results were reproducible at 500 SQE/m³ . Pulmonary function and adverse event frequency did not change with escalation of allergen dose.

CONCLUSION

This HDM allergen particle generation is safe, specific and reproducible and can therefore be used for efficacy testing of immunotherapy and for basic clinical research.

A novel HLA-DRα1-MOG-35-55 construct treats experimental stroke

Chemoattraction of leukocytes into the brain after induction of middle cerebral artery occlusion (MCAO) increases the lesion size and worsens disease outcome. Our previous studies demonstrated that partial MHC class II constructs can reverse this process. However, the potential application of pMHC to human stroke is limited by the need to rapidly match recipient MHC class II with the β1 domain of the pMHC construct. We designed a novel recombinant protein comprised of the HLA-DRα1 domain linked to MOG-35-55 peptide but lacking the β1 domain found in pMHC and treated MCAO after 4 h reperfusion in humanized DR2 mice. Infarct volumes were quantified after 96 h reperfusion and immune cells from the periphery and CNS were evaluated for expression of CD74 and other cell surface, cytokine and pathway markers. This study demonstrates that four daily treatments with DRα1-MOG-35-55 reduced infarct size by 40 % in the cortex, striatum and hemisphere, inhibited the migration of activated CD11b+CD45high cells from the periphery to the brain and reversed splenic atrophy. Furthermore, DRα1-MOG-35-55 bound to CD74 on monocytes and blocked both binding and downstream signaling of macrophage migration inhibition factor (MIF) that may play a key role in infarct development. The novel DRα1-MOG-35-55 construct is highly therapeutic in experimental stroke and could be given to all patients at least 4 h after stroke onset without the need for tissue typing due to universal expression of DRα1 in humans.

Abstract W P92: Preclinical Evaluation of Recombinant T-cell Receptor Ligand RTL1000 as a Therapeutic Agent in Stroke

Objective: RTL1000, a partial human MHC molecule coupled to a human myelin peptide, reduces infarct size after experimental stroke in HLA-DR2 transgenic mice expressing the human MHC class II allele. In this study, we characterized the therapeutic window of RTL1000. We then determined if RTL1000 efficacy is altered when combined with t-PA, a standard therapy for stroke, and if it affords long-term neurobehavioral functional improvement after stroke in mice.

Methods: Male DR2 mice underwent 60 min of intraluminal MCA occlusion (MCAO). RTL1000 (100 μg) or vehicle (100 μl) was given S.C. at 4, 6 or 8 h after MCAO, followed by 3 daily S.C. injections. t-PA (10 mg/kg) or vehicle was infused I.V. over 30 min starting at 15 min into ischemia. Brains were collected at either 24 or 96 h of reperfusion. Cortical, striatal and hemispheric infarcts were measured after staining with 2, 3, 5-triphenyltetrazolium chloride. Behavioral testing neuroscore, open field, paw preference and novel object recognition was performed up to 28 days after MCAO.

Results: RTL1000 significantly reduced infarct size when administered at 4 and 6, but not 8 h after MCAO. Protection was more robust when RTL1000 was given at 4 h, and was limited to cortex when first administration was delayed for 6 h. When administered alone, t-PA reduced infarct size when measured at 24 but not 96 h after MCAO. Importantly, RTL1000 alone reduced infarct size at 96 h after MCAO, and the addition of t-PA did not reduce its ability to protect against ischemic injury. Behavioral testing showed RTL1000 had no effect on acute cognitive impairment on day 7, but improved long term cognitive outcome 28 days after MCAO.

Conclusions: RTL1000 is protective against ischemic stroke with a therapeutic window of up to 6 h. Protection by RTL1000 is preserved in the presence of t-PA, is long-lasting and improves neurobehavioral functional outcomes after experimental cerebral ischemia.