Aquatain® causes anti-oviposition, egg retention and oocyte melanization and triggers female death in Aedes aegypti.

BACKGROUND: In arboviral disease systems where the virus can be transmitted from male to female vectors and from one generation to the next, targeting the female (especially when she is gravid) can help alter the persistence of the virus in nature and its transmission. A typical example is Aedes aegypti, which has become unmanageable due to the development of insecticide resistance. Despite evidence that monomolecular surface films prevent the selection of genetic resistance, their potential in Aedes vector control remains largely unexplored. METHODS: We examined the oviposition, egg retention, oocyte melanization, and female mortality of the Cayman Islands strain of Ae. aegypti, using choice (balanced and unbalanced) and no-choice bioassays involving Aquatain® Mosquito Formulation (AMF; Aquatain Products Pty Ltd.), a polydimethylsiloxane-based liquid used for mosquito control. RESULTS: When presented with similar opportunities to oviposit in two sites treated with AMF and two other sites with untreated water (control), egg deposition rates were significantly higher in the untreated water sites than in the AMF-treated sites (P < 0.05). We also observed a matching pattern of egg deposition preference in environments with more options in terms of AMF-treated sites. Females laid significantly more eggs when water was the only available medium than when all sites were treated with AMF (P < 0.05). Also, significantly more mature eggs were withheld in the AMF no-choice environment than in the no-choice test involving only water (P < 0.05). Internal oocyte melanization was not observed in females from the oviposition arenas with the lowest AMF presence (equal-choice and water-based no-choice); in contrast, this physiological response intensified as the number of AMF-treated sites increased. Female death occurred at high rates in AMF-treated environments, and this response increased with the increasing presence of such egg deposition sites. CONCLUSIONS: This study demonstrated that AMF acted as a deterrent signal to ovipositing Ae. aegypti and as an indirect adulticide. These results suggest that AMF may be a promising control tool against the dengue vector, and this warrants further evaluation under field settings.

Evaluation of a Novel User-Friendly Arthropod Repellent Gel, Verdegen.

Hand sanitizers are developed as alcohol-based liquid gel formulations, generally used to decrease the amount of infectious agents on human hands. Verdegen, LLC proposed to prepare an arthropod repellent gel for public use when the recent outbreaks of Zika infection vectored through Aedes mosquitoes in the American continents prompted multi-faceted emergency measures. Four different gel formulations were developed, comprising two of the most efficacious commercial arthropod repellent active ingredients, N,N-diethyl-3-methyl benzamide (deet) and 2-(2-hydroxyethyl)-1-piperidinecarboxylic acid 1-methylpropyl ester (picaridin), each at different concentrations (20 and 33% deet, or 20 and 33% picaridin). Compliance with the use of topical arthropod repellents remains an issue among military personnel. One of the most common complaints by Soldiers is that they do not like how the repellents applied on their skin leave behind an oily or greasy residue. These new gel formulations offer a user-friendly alternative for commonly used arthropod repellents formulations for the military and civilian personnel. We tested the efficacy and protection time of these new gel formulations in comparison with the commercially available cream formulations of deet and picaridin at similar concentrations. Our data show that gel formulations have better topical attributes, and offer equal or better biting protection for up to 48 h against host-seeking Aedes aegypti (L.) (Diptera: Culicidae) female mosquitoes.

Introduction, control, and spread of Aedes albopictus on Grand Cayman Island, 1997-2001.

Infestations of Aedes albopictus were first identified in the Cayman Islands on June 19, 1997. Control techniques that had previously been effective in the elimination of Ae. aegypti from these islands were employed with the aim of eliminating this species. Chemical control methods against adult mosquitoes used a combination of ultra-low-volume applications of fenthion, backpack spraying with permethrin, and residual wall treatments with lambda-cyhalothrin. Larval stages were also targeted with the use of granular formulations of temephos and methoprene applied to all containers capable of sustaining larval development. For a 2-year period after the discovery of the introduction the abundance of this mosquito remained low (Breteau index = 0.6); however, in 1999 Ae. albopictus became firmly established (Breteau index = 5.5). By the end of 2001 it was apparent that the control methods utilized had failed to stop the spread of this species. This work describes the control methods utilized and discusses possible reasons for the failure of the elimination campaign.

Reintroduction of Aedes aegypti into Grand Cayman.

In October 2002 Aedes aegypti was detected on Grand Cayman after an absence of 5 years. This study outlines the techniques used by the Mosquito Research & Control Unit of the Cayman Islands to monitor the reintroduction of Ae. aegypti and to determine the extent of the new infestation. Suggestions are made for improvements of port disinsection activities to minimize further introductions.

A novel adjuvant complex, tyrosine-MPL, for prophylactic and therapeutic vaccines.

Therapeutic vaccination for the treatment of allergy has been used for nearly a century but it is only recently that the mechanisms whereby benefits can be achieved have begun to be identified [Bousquet J, Lockey FR, Mailing HJ. Allergy immunotherapy: therapeutic vaccines for allergic diseases. WHO Position Paper. Allergy 1998;53:1-42.]. The induction of blocking antibodies was originally thought to lead to amelioration of allergic symptoms. There is now evidence that a switch from a Th2 (IgE/inflammatory) response to a Thl biased allergen specific response is part of the answer [Durham SR, Till SJ, Immunologic changes associated with allergen immunotherapy. J Allergy Clin Immunol, 1998; 102:157-64.]. Specific anergy induced by raised IL 10 and TGF3 and the induction of regulatory T cells may also be important [Akdis CA, Blaser K, Allergen-specific immunotherapy. Allergy 2000;55:522-30.]. A new adjuvant complex, L-tyrosine-MPL can accelerate these processes.

Modern approaches to therapeutic vaccination as treatment for type 1 respiratory hypersensitivity (allergy) treatment.

The incidence of respiratory and other allergies has increased dramatically in many countries over the last few decades. Drug treatment is symptomatic and has a minimal effect on the underlying immunological dysfunction. This disease process may, however, be modified by allergy vaccination, which is typically applied by injecting increasing strengths of the offending allergens. Its use has been fairly limited owing to long injection schedules involving many visits to the physician, occasional local or systemic side effects, perceived limited efficacy and poor compliance. A greater understanding of the immunological mechanisms involved in allergy vaccination has led recently to the development of new generations of products with properties that address some of these issues, and these advances are likely to increase the successful use of the therapy.

Allergy vaccines--new approaches to an old concept.

Allergy vaccination (AV) consists of injecting increasing amounts of offending allergens into sensitive patients with the intention of reducing their level of sensitivity to allergens. This form of therapy was first used over one hundred years ago and until recently had not changed in principle. The vaccines themselves are now far better characterised and standardised, according to new regulatory requirements. The therapy is believed to exert its effects by a combination of means: by the induction of blocking antibodies; a switch from a T helper (Th)2 to a more Th1 allergen-specific immune response; and induction of anergy, probably via the development of allergen-specific regulatory T cells. New allergen forms and formulations are being designed with these targets in mind. Allergoids (allergens chemically modified to reduce allergenicity, but to retain immunogenicity) are becoming employed more frequently. More modern depot forms, such as those containing tyrosine or calcium phosphate, are replacing aqueous extracts and older depot adjuvants such as alum. T cell-reactive peptides and recombinant allergens or their muteins are also being studied as replacements for whole extracts and have shown some potential. Immunomodulators, such as monophosphoryl lipid A (MPL), designed with defined targets in mind are now included in some vaccines and help to accelerate the process. All these measures have led to a reduction in the need for the traditional long injection schedules. The authors are very familiar in particular with the background to the use of MPL as an adjuvant. They have been personally involved in the development of this approach, which has led to a product being available for use on a regular basis in some European countries. Hence, this work is reported in considerable detail. Other similar immunomodulators, such as CpG motifs, are in development, while new targets, such as the Notch protein/receptor interaction, are exciting new developments that may eventually bear fruit. The excellent safety profile of the sublingual route of administration of allergy vaccines could lead to the wider use of AV, and locally active immunomodulators could make AV a therapy of choice for many more patients than at present.

Review of L-tyrosine confirming its safe human use as an adjuvant.

Although there is a long history of exposure to allergy vaccines containing L-tyrosine, there has been no central publication reviewing its adjuvant properties in animal and human studies together with an assessment of its safe use. This paper summarizes a range of investigational data (unpublished) available to the authors as well as published literature reports. An array of in vitro and in vivo studies showed that L-tyrosine has ideal adjuvant properties, comprising a high adsorptive power for proteins, enhancement of IgG antibody induction with no stimulatory effect on IgE antibody level and action as a short-term depot adjuvant, delaying the bioavailability of allergenic materials rather than directly influencing immunocompetent cells. A series of preclinical safety investigations comprised single-dose parenteral studies in the mouse and rat, repeat-dose parenteral toxicity studies over 28 days in the rat and dog (up to 25 mg kg(-1) day(-1)) plus genotoxicity and local tolerance studies. No signs of toxicity or genotoxicity were seen; repeat-dose toxicity studies showed expected white cell and spleen weight immunostimulatory effects; local-dose site reactions were also seen and were confirmed in local tolerance studies. Findings from a range of clinical studies using allergy vaccines containing L-tyrosine reflected the lack of toxicity seen in animal work and showed evidence of enhanced immunostimulatory activity. Local injection site reactions (a common response to any form of clinical vaccination) in these studies were likely to be due to the presence of L-tyrosine per se. The lack of findings of toxicological concern found during this review supports the hypothesis that L-tyrosine is a safe adjuvant for human use.

Safety evaluation of monophosphoryl lipid A (MPL): an immunostimulatory adjuvant.

Animal models have shown the potential use of monophosphoryl lipid A (MPL), a detoxified bacterial lipopolysaccharide, as a vaccine adjuvant. Immunostimulatory activity with diverse effects on the cellular elements of the immune system has been demonstrated and a range of vaccines incorporating MPL, including allergy vaccines, are currently under clinical evaluation. A series of preclinical safety investigations was performed to support clinical use of MPL as used in allergy vaccines and comprised cardiovascular/respiratory assessment in dog (up to 100 microg/kg/day); repeat-dose toxicity in rat, rabbit, and dog (up to 2500 and 1200 microg/kg/day in the rat and dog, respectively); reproduction toxicity in rat and rabbit (up to 100 microg/kg/day); and genotoxicity studies. Overall, repeat-dose toxicity studies in the rat and dog showed expected immunostimulatory effects and/or signs of toxicity associated with overstimulation of the immune system (notably increased spleen weight and white blood cell values). Studies in the rabbit with weekly doses of MPL produced no effects. MPL was shown to have no adverse effects on cardiovascular/respiratory function, reproduction, and genotoxicity.

Safety evaluation of a new allergy vaccine containing the adjuvant monophosphoryl lipid A (MPL) for the treatment of grass pollen allergy.

A novel allergy vaccine (Pollinex Quattro) has been developed for the prevention or relief of allergic symptoms caused by a variety of pollens. Within this range, the grass pollen allergy vaccine contains extracts of 12 grass pollens and rye cereal (all chemically modified by glutaraldehyde) that are adsorbed onto L-tyrosine with addition of the immunostimulatory adjuvant monophosphoryl lipid A (MPL). A specific preclinical safety testing strategy was developed to support clinical use, comprising single-dose toxicity, repeat-dose toxicity and local tolerance studies. Dose levels of up to 0.5 ml per animal (mouse) and up to 1.0 ml per animal (rat and rabbit) were used with vaccines containing 2000 or 12 000 standardized units (SU) ml(-1) of grass pollen allergoids, 50 micro g ml(-1) of MPL adjuvant and 20 mg ml(-1) of tyrosine. Overall, the product showed no toxicological findings of significance at levels greatly in excess of those proposed for clinical use. A not unexpected, but relatively minor, immunostimulatory effect was seen following repeated dosing (once weekly for 3 weeks) at 1.0 ml per rat.