Surface lipidome of the lone star tick, Amblyomma americanum, provides leads on semiochemicals and lipid metabolism

Identification of Alpha-Gal glycolipids in saliva of Lone-Star Tick (Amblyomma americanum)

Alpha-Gal Syndrome (AGS) is a delayed allergic reaction triggered by IgE antibodies targeting galactose-α-1,3-galactose (α-gal), prevalent in red meat. Its global significance has increased, with over 450,000 estimated cases in the United States alone. AGS is linked to tick bites, causing sensitization and elevated α-gal specific IgE levels. However, the precise mechanisms and tick intrinsic factors contributing to AGS development post-tick bites remain unclear. This study aims to characterize the alpha-gal conjugated lipid antigens in Amblyomma americanum (Am. americanum) salivary glands and saliva. Nanospray ionization mass spectrometry (NSI-MS) analysis revealed the identification of α-gal bound lipid antigens in Am. americanum saliva. Additionally, the activation of basophils by extracted alpha-gal bound lipids and proteins provides evidence of their antigenic capabilities.

Factors to Male-Female Sex Approaches and the Identification of Volatiles and Compounds from the Terminalia of Proholopterus chilensis (Blanchard) (Coleoptera: Cerambycidae) Females in Nothofagus obliqua (Mirb.) Oerst. (Nothofagaceae) Forests in Chile

During the spring-summer seasons between 2019 and 2023, in the localities of Maquehue (La Araucanía Region) and Llifén (Los Ríos Region), we collected 262 virgin Proholopterus chilensis (1 female/2.3 males) specimens emerging from the live trunks of N. obliqua trees, an atypical sex ratio in Cerambycidae, suggesting high male competition for females. Virgin specimens of both sexes were individually placed in panel traps in the field, capturing only males (n = 184) over the field study seasons and only in traps baited with females. This fact preliminarily suggests the P. chilensis females emit possible "volatile or airborne" pheromones (eventually being a long-range sex pheromone), something unusual in Cerambycinae, the subfamily to which it currently belongs, although the taxonomic status of the species is under debate. In Llifén and Santiago (Metropolitan Region), behavioral observations were conducted, which allowed us to define the conditions necessary for male-female encounters that were replicated when carrying out volatile captures (Head Space Dynamic = HSD) and collections of compounds from terminalias excised from females. In field trials, virgin females less than ten days old were more attractive than older ones and attracted males during the night, i.e., between 23:00 and 5:00 AM, when the ambient temperature exceeded 11.6 °C. The aeration of females under the conditions described above and subsequent analysis of extracts by GC-MS allowed the identification of compounds absent in males and the control, including two oxygenated sesquiterpenes, a nitrogenous compound (C20), and a long-chain hydrocarbon (C26). From the terminalia extracts, hentriacontane, heptacosane, and heneicosyl, heptacosyl and docosyl acetates were identified by GC-MS, and their roles are unknown in the development of short-distance sexual behaviors, but they could serve to mark a trail leading the male towards the female in the final stage of approach for courtship/mating. Thus, we proposed the hypothesis that P. chilensis females emit both a long-range and a trail-pheromone, which, if confirmed, would be a rare case in this family. The specific identity of the compounds obtained by HSD, as well as the activities of these chemicals and those obtained from the terminalias, should be evaluated in future behavioral studies, as well as regarding their potential to attract males under field conditions. The current document is the first report on volatiles obtained from aerations and compounds extracted from female terminalia in P. chilensis.

Characterization of Leptoglossus occidentalis Eggs and Egg Glue

The western conifer seed bug (Leptoglossus occidentalis Heidemann, 1910, Heteroptera: Coreidae) has a significant economic impact due to the reduction in the quality and viability of conifer seed crops; it can feed on up to 40 different species of conifers, showing a clear predilection for Pinus pinea L. in Europe. Its incidence is especially relevant for the pine nut-producing industry, given that the action of this pest insect can reduce the production of pine nuts by up to 25%. As part of ongoing efforts aimed at the design of control strategies for this insect, this work focuses on the characterization (by scanning electron microscopy-energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and gas chromatography-mass spectroscopy, GC-MS) of the compounds released by these insects during oviposition, with emphasis on the adhesive secretion that holds L. occidentalis eggs together. Elemental analysis pointed to the presence of significant amounts of compounds with high nitrogen content. Functional groups identified by infrared spectroscopy were compatible with the presence of chitin, scleroproteins, LNSP-like and gelatin proteins, shellac wax analogs, and policosanol. Regarding the chemical species identified by GC-MS, eggs and glue hydromethanolic extracts shared constituents such as butyl citrate, dibutyl itaconate, tributyl aconitate, oleic acid, oleamide, erucamide, and palmitic acid, while eggs also showed stearic and linoleic acid-related compounds. Knowledge of this composition may allow advances in new strategies to address the problem caused by L. occidentalis.

Acaricidal action of ozone on larvae and engorged females of Rhipicephalus microplus: a dose-dependent relationship

The tick Rhipicephalus microplus is a vector of infectious agents that causes great economic loss in the productivity of cattle herds. Several studies have sought natural compounds with acaricidal activity to control ticks, without allowing the development of resistance, without causing environmental damage, and without presenting toxicity to the hosts. The activity of ozone on the natural biomolecules of living beings has been studied as an alternative to control arthropods and acaricidal effects were shown on ticks. The aim of the present study was to assess the acaricidal effect on larvae and engorged females of R. microplus according to ozone dose. Larvae (n = 377) were distributed in 10 groups and engorged females (n = 284) were distributed in 14 groups. One group was used as control (not exposed to ozone) and the other groups were exposed to ozone gas for 5-105 min. Ozone had a dose-dependent acaricidal effect on both larvae and engorged females. Dosages between 355 and 2130 mg/L min had a delayed acaricidal effect (12-180 h), leading to the death of all engorged females before laying eggs, whereas doses between 3195 and 7455 mg/L min showed immediate acaricidal effect (5 min to 4 h). Doses between 1775 and 6390 mg/L min had an immediate (up to 5 min) acaricidal effect on the larvae of this species. Further studies should consider longer follow-up times during the assessment of the acaricidal activity against ticks.

Interfering with cholesterol metabolism impairs tick embryo development and turns eggs susceptible to bacterial colonization

Cholesterol is a known precursor of arthropod molecules such as the hormone 20-hydroxyecdysone and the antimicrobial boophiline, a component of tick egg wax coat. Because the cholesterol biosynthetic pathway is absent in ticks, it is necessarily obtained from the blood meal, in a still poorly understood process. In contrast, dietary cholesterol absorption is better studied in insects, and many proteins are involved in its metabolism, including Niemann-Pick C (NPC) transporter and acyl-CoA:cholesterol acyltransferase (ACAT), as well as enzymes to convert between free cholesterol and esterified cholesterol. The present work addresses the hypothesis that tick viability can be impaired by interfering with cholesterol metabolism, proposing this route as a target for novel tick control methods. Two drugs, ezetimibe (NPC inhibitor) and avasimibe (ACAT inhibitor) were added to calf blood and used to artificially feed Rhipicephalus microplus females. Results show that, after ingesting avasimibe, tick reproductive ability and egg development are impaired. Also, eggs laid by females fed with avasimibe did not hatch and were susceptible to Pseudomonas aeruginosa adhesion and biofilm formation in their surfaces. The immunoprotective potential of ACAT against ticks was also accessed using two selected ACAT peptides. Antibodies against these peptides were used to artificially feed female ticks, but no deleterious effects were observed. Taken together, data presented here support the hypothesis that enzymes and other proteins involved in cholesterol metabolism are suitable as targets for tick control methods.

Comparative response of Metarhizium brunneum to the cuticles of susceptible and resistant hosts

Earlier studies demonstrated that Metarhizium brunneum, usually a broad-host pathogen of arthropods, is unable to complete its pathogenic life cycle when inoculated on the fungus-resistant tick, Hyalomma excavatum engorged females. While the fungus penetrates the cuticle of fungus-susceptible tick, Rhipicephalus annulatus females, it is unable to penetrate the cuticle of fungus-resistant tick, and even perishes on its surface. This is probably due to high concentration of antifungal fatty acids and probably also due to a hypersensitive-like response of the tick. To understand the metabolic pathways occurring in the fungal hyphae upon encountering the cuticles, we compared the response of the fungus to cuticle from susceptible and resistant tick cuticles by 2D-gels. The intracellular proteomes of M. brunneum Mb7 exposed to cuticle of the fungus-susceptible tick, R. annulatus, and to the fungus-resistant tick, H. excavatum engorged females were compared after exposure to either cuticles. By means of liquid chromatography-mass spectrometry/mass spectrometry we identified in both proteomes common proteins involved in biological processes as well as unique proteins identified only in the proteome of fungus exposed to fungus-resistant tick cuticle. These proteins were identified in high probability as heat shock proteins, four key enzymes of the glyoxylate cycle, and proteins associated with hypoxia, and exposure to antifungal drugs. These findings are discussed within the M. brunneum-tick pathosystem in relation to tick resistance and host resistance in general.