Eczematous skin reaction to atopy patch testing with cockroach in patients with atopic dermatitis

BACKGROUND: Aeroallergens from house dust mite (HDM) may be an important trigger in a subgroup of patients with atopic dermatitis (AD). HDM and cockroach (CR) contain cross-reactive allergens, such as tropomyosin. OBJECTIVE: To investigate the diagnostic value of patch testing with an aeroallergen and the role of CR allergen and HDM allergen in persons with AD. METHODS: We performed skin prick tests (SPT) with a panel of common aeroallergens and total serum immunoglobulin (Ig)E and specific IgE tests for CR and HDM on 23 patients with AD and 9 nonatopic control participants. Atopy patch tests (APT) were performed with CR and HDM extracts on clinically uninvolved skin on the back, and evaluated after 48 and 72 hours. RESULTS: A positive APT reaction to CR was found in 10/23 (43%) patients with AD. No positive reactions were observed in the nonatopic control participants. Positive APT reactions for CR showed no significant correlation with SPT or specific IgE levels for this allergen. Twelve of the 23 (52%) patients with AD were also sensitized to HDM. There was no significant correlation between positive results for SPT, APT, and specific IgE to CR and HDM. CONCLUSION: We demonstrate that CR allergens can induce positive patch test reactions in patients with AD. The absence of a significant correlation to SPT and specific IgE antibodies suggests that T-cell- and IgE-sensitization may be mediated by different allergens. There was no significant relationship between CR and HDM sensitivity, thus indicating no major cross-reactivity.

CSTX-1, a toxin from the venom of the hunting spider Cupiennius salei, is a selective blocker of L-type calcium channels in mammalian neurons

The inhibitor cystine-knot motif identified in the structure of CSTX-1 from Cupiennius salei venom suggests that this toxin may act as a blocker of ion channels. Whole-cell patch-clamp experiments performed on cockroach neurons revealed that CSTX-1 produced a slow voltage-independent block of both mid/low- (M-LVA) and high-voltage-activated (HVA) insect Ca(v) channels. Since C. salei venom affects both insect as well as rodent species, we investigated whether Ca(v) channel currents of rat neurons are also inhibited by CSTX-1. CSTX-1 blocked rat neuronal L-type, but no other types of HVA Ca(v) channels, and failed to modulate LVA Ca(v) channel currents. Using neuroendocrine GH3 and GH4 cells, CSTX-1 produced a rapid voltage-independent block of L-type Ca(v) channel currents. The concentration-response curve was biphasic in GH4 neurons and the subnanomolar IC(50) values were at least 1000-fold lower than in GH3 cells. L-type Ca(v) channel currents of skeletal muscle myoballs and other voltage-gated ion currents of rat neurons, such as I(Na(v)) or I(K(v)) were not affected by CSTX-1. The high potency and selectivity of CSTX-1 for a subset of L-type channels in mammalian neurons may enable the toxin to be used as a molecular tool for the investigation of this family of Ca(v) channels.