Oral allergic syndrome after ingestion of custard apple

Characterization and gene cloning of an acidic thaumatin-like protein (TLP 1), an allergen from sapodilla fruit (Manilkara zapota)

BACKGROUND

Allergy to sapodilla (Manilkara zapota) fruit ingestion is rare. An independent study from our group has identified a basic thaumatin-like protein (TLP 2) as the major allergen. The present study was aimed at identifying and characterizing additional allergens from sapodilla.

METHODS

Allergic subjects were identified by case history, skin prick test (SPT) and allergen-specific IgE. Sapodilla extract was fractionated using SP-Sepharose into 3 components (SP1, SP2 and SP3) which were analyzed by native/SDS-PAGE, IgE-immunoblot, isoelectric focusing (IEF) and N-terminal sequencing. The conserved regions of plant TLPs and the N-terminal sequence were used to design primers for PCR.

RESULTS

SPT and ELISA confirmed a subject with oral allergy syndrome (OAS) to sapodilla and custard apple. Two proteins (26.9 and 24.5kDa; reducing conditions) were detected as allergens, of which the latter in SP2 has already been identified as basic TLP (TLP 2). The 26.9kDa protein present in SP1 was identified as an acidic TLP based on native PAGE, IEF and N-terminal sequencing. Presence of a basic β-1,3-glucanase in SP3 was inferred by zymography. Sequence analysis of the genomic clone of the acidic TLP gene revealed that it is intronless and non-glycosylated. Evolutionary relatedness to olive, grape and kiwi fruit allergenic TLPs were inferred by phylogenetic analysis.

CONCLUSIONS

An acidic TLP (TLP 1) was identified as a new allergen in sapodilla. TLP 1 is a single polypeptide (207 residues) belonging to the thaumatin family of the GH64-TLP-SF superfamily. Clinically, sapodilla should be considered in the list of fruits causing OAS.

Tumour necrosis factor-alpha but not interferon-gamma is the main inducer of inducible protein-10 in skin fibroblasts from patients with atopic dermatitis

BACKGROUND

Inducible protein (IP)-10 belongs to the CXC chemokine subfamily and acts through the CXCR3 receptors that attract T lymphocytes. Keratinocytes are thought to be the main cell source of this chemokine in the skin, but other sources need to be elucidated.

OBJECTIVES

To determine whether skin fibroblasts, besides keratinocytes, are able to produce IP-10 and the possible involvement of these cells in pathogenesis of atopic dermatitis (AD).

METHODS

We studied the production pattern of IP-10 in dermal fibroblasts obtained from healthy donors, AD patients and in the HaCaT cell line (normal human keratinocytes) used as control. We stimulated fibroblasts after the sixth and seventh passage with tumour necrosis factor (TNF)-alpha, interferon (IFN)-gamma, interleukin (IL)-4, and by means of reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay analysis detected the production pattern of IP-10. To determine whether a different pattern of production of IP-10 by fibroblasts corresponds to the level of this chemokine in the plasma of patients with AD, we also checked the plasma IP-10 levels in 33 AD patients and 10 healthy donors.

RESULTS

The pattern of chemokine production between dermal fibroblasts and HaCaT cells was different. The main inducer of IP-10 in fibroblasts was TNF-alpha, whereas IFN-gamma was the main inducer of IP-10 in HaCaT cells. We demonstrate that fibroblasts from AD patients have higher IP-10 expression and are more sensitive to TNF-alpha stimulation compared with healthy controls. Consequently, IP-10 levels in plasma of AD patients were higher than in healthy donors.

CONCLUSIONS

Skin fibroblasts could be an important source of IP-10. TNF-alpha is the main inducer of IP-10 by skin fibroblasts, but not IFN-gamma or IL-4. The increased level of IP-10 in the plasma of patients with AD could be connected with increased activity of skin fibroblasts.