Free-roaming kissing bugs, vectors of Chagas disease, feed often on humans in the Southwest.

BACKGROUND: Kissing bugs, vectors of Trypanosoma cruzi, the parasite that causes Chagas disease, are common in the desert Southwest. After a dispersal flight in summer, adult kissing bugs occasionally gain access to houses where they remain feeding on humans and pets. How often wild, free-roaming kissing bugs feed on humans outside their homes has not been studied. This is important because contact of kissing bugs with humans is one means of gauging the risk for acquisition of Chagas disease. METHODS: We captured kissing bugs in a zoological park near Tucson, Arizona, where many potential vertebrate hosts are on display, as well as being visited by more than 300,000 humans annually. Cloacal contents of the bugs were investigated for sources of blood meals and infection with T. cruzi. RESULTS: Eight of 134 captured bugs were randomly selected and investigated. All 8 (100%) had human blood in their cloacae, and 7 of 8 (88%) had fed on various vertebrates on display or feral in the park. Three bugs (38%) were infected with T. cruzi. Three specimens of the largest species of kissing bug in the United States (Triatoma recurva) were captured in a cave and walking on a road; 2 of 3 (67%) had fed on humans. No T. recurva harbored T. cruzi. CONCLUSIONS: This study establishes that free-roaming kissing bugs, given the opportunity, frequently feed on humans outside the confines of their homes in the desert Southwest and that some harbored T. cruzi. This could represent a hitherto unrecognized potential for transmission of Chagas disease in the United States.

The structure of helokinestatin-5 and its biosynthetic precursor from Gila monster (Heloderma suspectum) venom: evidence for helokinestatin antagonism of bradykinin-induced relaxation of rat tail artery smooth muscle.

Here we report the primary structure of a novel peptide, named helokinestatin-5 (VPPPLQMPLIPR), from the venom of the Gila monster (Heloderma suspectum). Helokinestatin-5 differs in structure from helokinestatin-3 by deletion of a single prolyl residue in the N-terminally located polyproline region. Two different biosynthetic precursors were consistently cloned from a venom-derived cDNA library. The first encoded helokinestatins 1-4 and a single copy of C-type natriuretic peptide, as previously described, whereas the second was virtually identical, lacking only a single prolyl codon as found in the mature attenuated helokinestatin-5 peptide. Helokinestatins 1-3 and 5 were synthesized by solid-phase fmoc chemistry and each synthetic replicate was found to antagonize the relaxation effect induced by bradykinin on rat tail artery smooth muscle. Helokinestatins thus represent a novel family of vasoactive peptides from the venom of helodermatid lizards.

Helokinestatin: a new bradykinin B2 receptor antagonist decapeptide from lizard venom.

Synthetic bradykinin antagonist peptides/peptoids have been powerful tools for delineating the roles of kinins in both normal physiology and in pathological states. Here, we report the identification of a novel, naturally occurring bradykinin B2 receptor antagonist peptide, helokinestatin, isolated and structurally characterized from the venoms of helodermatid lizards-the Gila monster (Heloderma suspectum) and the Mexican beaded lizard (Heloderma horridum). The primary structure of the peptide was established by a combination of microsequencing and mass spectroscopy as Gly-Pro-Pro-Tyr-Gln-Pro-Leu-Val-Pro-Arg (Mr 1122.62). A synthetic replicate of helokinestatin was found to inhibit bradykinin-induced vasorelaxation of phenylephrine pre-constricted rat tail artery smooth muscle, mediated by the B2 receptor sub-type, in a dose-dependent manner. Natural selection, that generates functional optimization of predatory reptile venom peptides, can potentially provide new insights for drug lead design or for normal physiological or pathophysiological processes.

Isolation and cloning of exendin precursor cDNAs from single samples of venom from the Mexican beaded lizard (Heloderma horridum) and the Gila monster (Heloderma suspectum).

Reptile venoms are complex cocktails of bioactive molecules, including peptides. While the drug discovery potential of most species remains unrealized, many are endangered and afforded protection under international treaties. In this study, we describe how potential clinically important bioactive peptides and their corresponding mRNAs can be structurally characterized from single, small samples of reptile venom. The potential type-2 diabetes therapeutics, exendin-3 and exendin-4, from the Mexican beaded lizard (Heloderma horridum) and the Gila monster (Heloderma suspectum), respectively, have been characterized at both protein and nucleic acid levels to illustrate the efficacy of the technique and its contribution to biodiversity conservation.

Unmasking venom gland transcriptomes in reptile venoms.

While structural studies of reptile venom toxins can be achieved using lyophilized venom samples, until now the cloning of precursor cDNAs required sacrifice of the specimen for dissection of the venom glands. Here we describe a simple and rapid technique that unmasks venom protein mRNAs present in lyophilized venom samples. To illustrate the technique we have RT-PCR-amplified a range of venom protein transcripts from cDNA libraries derived from the venoms of a hemotoxic snake, the Chinese copperhead (Deinagkistrodon acutus), a neurotoxic snake, the black mamba (Dendroaspis polylepis), and a venomous lizard, the Gila monster (Heloderma suspectum). These include a metalloproteinase and phospholipase A2 from D. acutus, a potassium channel blocker, dendrotoxin K, from D. polylepis, and exendin-4 from H. suspectum. These findings imply that the apparent absence and/or lability of mRNA in complex biological matrices is not always real and paves the way for accelerated acquisition of molecular genetic data on venom toxins for scientific and potential therapeutic purposes without sacrifice of endangered herpetofauna.