Richard J. Brenner

Isolation and characterization of a clone encoding a major allergen (Bla g Bd90K) involved in IgE-mediated cockroach hypersensitivity

Previous studies have established that atopic individuals living in cockroach-infested housing become sensitized to cockroach aeroallergens and produce IgE antibodies to a variety of proteins. We describe the isolation of a complementary DNA clone from an expression library, constructed with messenger RNA from German (Blattella germanica) cockroaches, which encodes a major allergen involved in mediating cockroach hypersensitivity. Approximately 0.2% of the clones from a lambda ZAP XR cDNA library bound IgE from a patient with cockroach sensitivity. A randomly selected subset of these clones revealed that they were either different isolates of the same gene or members of a closely related gene family. One of the largest clones (a 4 kb insert) from this subset, Bla g Bd90K hybridized to a single mRNA of approximately the same size. DNA sequence analysis showed that this gene consisted of seven 576 bp tandem repeats with a short unique region at either end. No significant sequence homologies were found between the cockroach clone and any other gene reported in the GenBank database. Serum from 17 of 22 (77%) patients with cockroach hypersensitivity identified IgE-binding recombinant protein expressed from clone Bla g Bd90K in Escherichia coli XL-Blue cells as determined by sodium dodecylsulfate-polyacrylamide gel electrophoresis/immunoblot analysis. This recombinant protein migrates with a molecular weight (90 kd) apparently similar to one identified in whole body extracts. We have identified and isolated a cDNA that encodes a major cockroach allergen (Bla g Bd90K) present in German cockroaches.

Insecticide Susceptibility in Coptotermes formosanus and Reticulitermes virginicus (Isoptera: Rhinotermitidae)

Abstract Lethal time to mortality responses were established for eight insecticides against workers and soldiers of the Formosan subterranean termite, Coptotermes formosanus Shiraki, and workers of Reticulitermes virginicus (Banks). There were significant differences in the tolerance ratios between workers of C. formosanus colonies to all toxicants tested except fipronil. One colony was 16 times more tolerant than another to deltamethrin. C. formosanus soldiers had significant differences in tolerance ratios among colonies exposed to all toxicants except chlorpyrifos. Methoxychlor, permethrin, deltamethrin, and fipronil did not kill soldiers from two, one, one, and three colonies, respectively, within 8 h. Seventy-five percent of R. virginicus colonies were significantly less susceptible than the most susceptible colony to chlordane, methoxychlor, chlorpyrifos, cypermethrin, and fipronil, with 50% of the colonies less susceptible to permethrin and bendiocarb. In 50% of C. formosanus colonies the worker lethal time curves displayed substantial flattening in response to permethrin, and deltamethrin. Lethal time curves for C. formosanus soldiers exposed to chlordane, chlorpyrifos, permethrin, cypermethrin, deltamethrin, and bendiocarb showed substantial flattening. R. virginicus workers demonstrated substantial curve flattening when exposed to chlordane, methoxychlor, chlorpyrifos, deltamethrin, and fipronil. These findings indicate substantial inter-colony and intra-colony differences in susceptibility to insecticides.

Comparative insecticide susceptibility and detoxification enzyme activities among pestiferous blattodea.

Topical bioassays using propoxur, chlorpyrifos, and lambda-cyhalothrin were conducted on eight cockroach species. Based on lethal dose values, the relative toxicities of the insecticide classes were generally pyrethroid > carbamate > organophosphorous. Lambda-Cyhalothrin and propoxur were more toxic toward the Blattidae as compared with the Blattellidae. The order of lambda-cyhalothrin toxicity was Periplaneta americana > Periplaneta brunnea = Periplaneta australasiae = Periplaneta fuliginosa = Blatta orientalis > Blattella asahinai = Blattella germanica > Blattella vaga. The order of propoxur toxicity was B. orientalis > P. americana > P. brunnea = P. australasiae > B. asahinai > P. fuliginosa = B. germanica > B. vaga. The order of chlorpyrifos toxicity was P. americana > B. asahinai = B. vaga > B. orientalis = P. australasiae = P. brunnea > B. germanica = P. fuliginosa. Detoxification enzyme activities for each species also were measured and compared with insecticide toxicity. Propoxur LD50 was significantly (P = 0.01; r = 0.81) correlated with glutathione S-transferase activity. Lambda-Cyhalothrin LD50 correlated with methoxyresorufin O-demethylase activity (P = 0.01; r = 0.81), carboxylesterase activity (P = 0.03; r = - 0.75), general esterase activity (P = 0.02; r = - 0.79), and cockroach weight (P = 0.01; r = -0.95).

Quality of Housing and Allergy to Cockroaches in the Dominican Republic

Fifty-one atopic asthmatic and/or allergic rhinitic children and 23 nonatopic control from Santo Domingo, the Dominican Republic, were skin tested with an extract mix of three cockroach species (Blattella germanica, Blatta orientalis, and Periplaneta americana). Sixteen percent of the atopics and none of the nonatopics demonstrated positive immediate skin reactions to the cockroach mix (chi 2 = 4.05, p = 0.04). Hypersensitivity was correlated with the quality of the homes; 22% (8/36) of the atopics who lived in a concrete home were skin test positive to the cockroach mix, while none (0/15) of the atopics who lived in a wood home were skin test positive (chi 2 = 4.86, p = 0.03). Although the incidence of cockroach allergy in this study is lower than that found elsewhere, these data support the notion that, in this tropical environment, sensitization to cockroaches is associated with housing quality.

Toxicity and In Vitro Metabolism of t-Permethrin in Eastern Subterranean Termite (Isoptera: Rhinotermitidae)

Abstract Toxicity and metabolism of t-permethrin were evaluated in two colonies (UF and ARS) of the eastern subterranean termite, Reticulitermes flavipes (Kollar), collected in Gainesville, FL. The UF colony (LC50 = 1.86 μg per vial) was approximately twofold more tolerant of t-permethrin than the ARS colony (LC50 = 0.89 μg per vial) at the LC50. The synergists piperonyl butoxide and S,S,S-tributylphosphorotrithioate increased t-permethrin toxicity four- and threefold (at the LC50) in the UF and ARS colonies, respectively. Despite these differences in t-permethrin susceptibility, microsomal oxidase activities toward surrogate substrates (aldrin epoxidase, and methoxyresorufin O-demethylase), cytochrome P450 content, and microsomal esterase activity toward α-naphthyl acetate did not differ significantly between the colonies. Moreover, no significant differences in qualitative and quantitative metabolism of [14C]t-permethrin were observed between the UF and ARS colonies for three enzyme sources (microsomal oxidase, microsomal esterase, and cytosolic esterase). Based on in vitro metabolism assays, the major detoxification route of t-permethrin in the UF and ARS termite colonies appears to be hydrolysis catalyzed by microsomal esterases.

TEMPERATURE EFFECTS ON k-CYHALOTHRIN TOXICITY IN INSECTICIDE-SUSCEPTIBLE AND RESISTANT GERMAN COCKROACHES (DICTYOPTERA: BLATTELLIDAE)

Pre- and post-treatment temperature effects on -cyhalothrin toxicity were determined in insecticide-susceptible and resistant German cockroach, Blattella germanica (L.), strains. Acclimation at 19, 26, or 31C for 10 days before insecticide treatment had no effect on l- cyhalothrin toxicity in either strain. No differences were observed in aldrin epoxidase and glutathione S-transferase activities when “Orlando” (susceptible) cockroaches were incubated for 10 days at 19, 26, and 31C. When temperature treatment followed insecticide application, a negative temperature coefficient of toxicity (greater toxicity at lower temperature) toward l- cyhalothrin was observed for the Orlando but not the kdr-type resistant “Village Green” cockroaches. Piperonyl butoxide synergized l- cyhalothrin in “Orlando” cockroaches 3 and 5-fold at 26 and 31C, respectively. Conversely, piperonyl butoxide pre-treatment did not cause a significant reduction in the LD 50 value in the “Village Green” strain regardless of temperature.

RESIDUAL EFFICACY OF BLATTICIDES APPLIED TO SURFACES CONTAMINATED WITH GERMAN COCKROACH (DICTYOPTERA: BLATTELLIDAE) FECES

Crack-and-crevice treatments were simulated in the presence and absence of German cockroach [Blattella germanica (L.)] feces to evaluate its effect on insecticide efficacy toward the German cockroach. The LT50 of German cockroaches exposed to 0.39 g of cypermethrin/cm2 (Demon EC formulation) on glass Mason jars was 26 min. The LT50 increased 2.5- and 4.5-fold when Demon EC was mixed with 123 and 184 mg of cockroach feces, respectively. The presence of German cockroach feces increased the LT50 2.5-fold in Dursban EC (chlorpyrifos) and 1.2-fold in Baygon EC (propoxur). Longevity experiments with 3 l-cyhalothrin formulations in the presence of German cockroach feces resulted in significant decreases in insecticide efficacy. Feces reduced the performance of Commodore WP (l-cyhalothrin) by 12.5, 35, 55, and 97.5% on days 0, 10, 20, and 30, respectively. Initial reductions in efficacy were observed for the Demand CS (l-cyhalothrin) and Karate (l-cyhalothrin) formulations when in the presence of German cockroach feces.