RESUMO
The control of ticks through vaccination offers a sustainable alternative to the use of chemicals that cause contamination and the selection of resistant tick strains. However, only a limited number of anti-tick vaccines have reached commercial realization. In this sense, an antigen effective against different tick species is a desirable target for developing such vaccines. A peptide derived from the tick P0 protein (pP0) conjugated to a carrier protein has been demonstrated to be effective against the Rhipicephalus microplus, Rhipicephalus sanguineus, and Amblyomma mixtum tick species. The aim of this work was to assess the efficacy of this peptide when conjugated to the Bm86 protein against Dermacentor nitens and Ixodes ricinus ticks. An RNAi experiment using P0 dsRNA from I. ricinus showed a dramatic reduction in the feeding of injected female ticks on guinea pigs. In the follow-up vaccination experiments, rabbits were immunized with the pP0-Bm86 conjugate and challenged simultaneously with larvae, nymphs, and the adults of I. ricinus ticks. In the same way, horses were immunized with the pP0-Bm86 conjugate and challenged with D. nitens larva. The pP0-Bm86 conjugate showed efficacies of 63% and 55% against I. ricinus and D. nitens ticks, respectively. These results, combined with previous reports of efficacy for this conjugate, show the promising potential for its development as a broad-spectrum anti-tick vaccine.
RESUMO
Canine leishmaniosis is an important vector-borne zoonosis caused mainly by Leishmania infantum. Diagnosis and treatment of affected individuals can be particularly complex, hindering infection control in endemic areas. Methods to prevent canine leishmaniosis include the use of topical insecticides, prophylactic immunotherapy and vaccination. Four vaccines against canine leishmaniosis have been licensed since 2004, two in Brazil (Leishmune®, the production and marketing licence of which was withdrawn in 2014, and Leish-Tec®) and two in Europe (CaniLeish® and LetiFend®). After several years of marketing, doubts remain regarding vaccine efficacy and effectiveness, potential infectiousness of vaccinated and infected animals or the interference of vaccine-induced antibodies in L. infantum serological diagnosis. This review summarises the scientific evidence for each of the vaccines commercially approved for canine leishmaniosis, while discussing possible weaknesses of these studies. Furthermore, it raises the need to address important questions related to vaccination impact in Leishmania-endemic countries and the importance of post-marketing pharmacological surveillance.
La leishmaniose canine est une importante zoonose à transmission vectorielle causée principalement par Leishmania infantum. Le diagnostic et le traitement des personnes atteintes peuvent être particulièrement complexes, entravant la lutte contre l'infection dans les zones d'endémie. Les méthodes de prévention de la leishmaniose canine comprennent l'utilisation d'insecticides topiques, l'immunothérapie prophylactique et la vaccination. Quatre vaccins contre la leishmaniose canine ont été homologués depuis 2004, deux au Brésil (Leishmune®, dont la licence de production et de commercialisation a été retirée en 2014 et Leish-Tec®) et deux en Europe (CaniLeish® et LetiFend®). Après plusieurs années de commercialisation, des doutes subsistent quant à l'efficacité et à l'effet du vaccin, au potentiel infectieux des animaux vaccinés et infectés ou à l'interférence des anticorps induits par le vaccin dans le diagnostic sérologique de L. infantum. Cette revue résume les données scientifiques de chacun des vaccins commercialement approuvés pour la leishmaniose canine, tout en discutant des possibles faiblesses de ces études. En outre, il soulève la nécessité de répondre à des questions importantes liées à l'impact de la vaccination dans les pays où la Leishmania est endémique et à l'importance de la surveillance pharmacologique post-marketing.