Characterization of the allergen Sol gem 2 from the fire ant venom, Solenopsis geminata

Abstract

Sol i 2 is a potent allergen in Solenopsis invicta venom, and most humans exhibit reactivity to it. The Sol gem 2 allergen found in the venom of the Thai tropical fire ant Solenopsis geminata was analysed in the present study. The protein was present in higher amounts than other proteins, as determined by SDS-PAGE, and presumably has allergenic properties similar to those of Sol i 2. Sol gem 2 molecular weight is 28 and 15 kDa, respectively, under non-reducing and reducing conditions, indicating that its native form is a dimer. LC-MS/MS analysis confirmed its similarity to Sol i 2. The mono/dimeric form of Sol gem 2 was determined to be relevant by proteomic approach and immunoblotting. An anti-Sol gem 2 antibody was produced in mice, with a titer greater than 1:800 according to the Western blotting analysis. The Sol gem 2-neutralising activity of this antibody was determined in crickets. The paralytic dose 50 (PD 50 ) of crude S. geminata venom was elevated from 0.18 mg/g of body weight to more than 0.90 mg/g of body weight after preincubation with antibody at a ratio of 1:1. These results suggest that Sol gem 2 plays an important role in mediating the effects of the piperidine derivatives in the venom.Key words: allergy, ant venom, hymenoptera, immunoreactivity. Original PaPer The Journal of Venomous Animals and Toxins including Tropical Diseases ISSN 1678-9199 | 2012 | volume 18 | issue 3 | pages 325-334 INTRODUCTIONVenomous insects such as bees, wasps, hornets, yellow jackets and fire ants belong to the order Hymenoptera. These insects have a stinging apparatus at the tail end of their abdominal segment and still comprise a serious problem in tropical climates. Every year, a large number of people are stung by these insects (1). The stings are capable of delivering between 100 ng (fire ants) and 50 μg (bees) of venom (2, 3). The venom is injected from a gland through the stinger and is used to catch prey and to defend against predators. The venom of these insects is composed of various biologically active peptide and protein components, some of which can cause toxicity or anaphylaxis in humans (4).Fire ants (Solenopsis sp.) are members of the Formicidae family. The medically important aggressive species are S. invicta, S. richteri, S. geminata and S. saevissima (5, 6). The venom components of these ants and their immunoreactivity have been extensively studied. Approximately 95% of fire ant venom consists of water-insoluble piperidine alkaloids, and approximately 0.1% of its weight (10 to 100 ng of protein in 0.04 to 0.11 μL per sting) is protein (7). The toxicity of the venom is thought to be due to solenopsins and methyl-, alkylor alkenyl-substituted piperidines (7-9). The venom has cytotoxic, insecticidal, antibiotic and antimicrobial properties as well (7,(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). The protein components of venom, which are wellknown allergens, are believed to play important roles in accelerating the spread of solenopsins to nearby cells and tissues. Solenopsins are believed t...

Immunotherapy in Anaphylaxis by Tropical Fire Ant Sting: A Case Report and Literature Review

“…Cross-reactivity among insects and ants have been established for some hymenoptera venoms with studies reporting cross-reactivity among major proteins of [13]. In this case we could suggest the presence of cross-reactivity between solenopsis invicta and solenopsis geminate, as well as the cross-reactivity between solenopsis geminata and wasp, however it would be interesting to demonstrate by in-vitro study the specific allergens and offer such reactivity.…”

Solenopsis geminata (tropical fire ant) anaphylaxis among Thai patients: its allergens and specific IgE-reactivity

“…After evaluating Sol gem 2 under non-reducing and reducing conditions, its native form was identified as a dimer with molecular weights of 28 and 15 kDa and allergenic properties similar to Sol i 2 of S. invicta. 23 A previous study demonstrated that the standard dosage of 0.5 ml of 1:100 wt/vol of S. invicta used as immunotherapy for ant anaphylaxis Thai patients demonstrated only 60% efficacy for preventing a field ant re-sting. However, after increasing the dosage to 0.5 ml of 1:50 wt/vol of S. invicta, the efficacy increased to 100%.…”

Identification, expression and characterization of the recombinant Sol g 4.1 protein from the venom of the tropical fire ant Solenopsis geminata

“…In-gel digestion and mass spectrometry techniques were performed using the methods described by Sukprasert et al [ 26 ]. Briefly, the endogenous Sol g 4.1 protein and the purified recombinant protein were separated by native-PAGE and SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis), respectively.…”

“…A degenerate sense oligonucleotide primer was designed according to the sequence similarity of the conserved region of Solenopsis 4 venom proteins and the nucleotide sequences corresponding to peptide sequences obtained from previous studies [ 26 ]. The RACE procedures were performed using the RACE System (Invitrogen, Life Technologies, USA).…”

“…The venom of the tropical fire ant S. geminata produces anaphylaxis and serious medical problems in Taiwan, Indonesia and many Asian islands and in Thailand [ 5 ]. S. geminata is widely distributed throughout all areas in Thailand, and these ants are commonly found in houses and fields [ 25 , 26 ]. Major components are piperidine alkaloids [ 1 , 27 ].…”