Development of vaccines against Ornithodoros soft ticks: An update

Abstract

Ticks are parasites of great medical and veterinary importance since they are vectors of numerous pathogens that affect humans, livestock and pets. Among the argasids, several species of the genus Ornithodoros transmit serious diseases such as tick-borne human relapsing fever (TBRF) and African Swine Fever (ASF). In particular, Ornithodoros erraticus is the main vector of these two diseases in the Mediterranean while O. moubata is the main vector in Africa. The presence of these Ornithodoros ticks in domestic and peridomestic environments may greatly hinder the eradication of TBRF and ASF from endemic areas. In addition, there is a constant threat of reintroduction and spreading of ASF into countries from where it has been eradicated (Spain and Portugal) or where it was never present (the Caucasus, Russia and Eastern Europe). In these countries, the presence of Ornithodoros vectors could have a tremendous impact on ASF transmission and long-term maintenance. Therefore, elimination of these ticks from at least synanthropic environments would contribute heavily to the prevention and control of the diseases they transmit. Tick control is a difficult task and although several methods for such control have been used, none of them has been fully effective against all ticks and the problems they cause. Nevertheless, immunological control using anti-tick vaccines offers an attractive alternative to the traditional use of acaricides. The aim of the present paper is to offer a brief overview of the current status in control measure development for Ornithodoros soft ticks, paying special attention to the development of vaccines against O. erraticus and O. moubata. Thus, our contribution includes an analysis of the chief attributes that the ideal antigens for an anti-tick vaccine should have, an exhaustive compilation and analysis of the scant anti-soft tick vaccine trials carried out to date using both concealed and salivary antigens and, finally, a brief description of the new reverse vaccinology approaches currently used to identify new and more effective protective tick antigens.

Gut transcriptome analysis on females of Ornithodoros mimon (Acari: Argasidae) and phylogenetic inference of ticks

“…Therefore, more research is needed in this field, especially in relation to the members of the Argasidae family. Díaz-Martín et al (2015) and Oleaga et al (2015) warn of the need for more transcriptomic studies of gut tissue from soft ticks, for a better understanding of the proteins and genes of biological and pharmacological interest.…”

“…Thus, knowledge about the vital molecular constituents of ticks, such as genes and/or proteins, have become the target of several studies (CASTRO et al, 2016;CHMELAŘ et al, 2016;DÍAZ-MARTÍN et al, 2015;HEEKIN et al, 2013;KOTSYFAKIS et al, 2015;PERNER et al, 2016;RIBEIRO et al, 2017;XU et al, 2016). These studies have sought to ascertain and understand the roles of the molecules involved in the tick-host or tick-pathogen relationship.…”

“…These studies have sought to ascertain and understand the roles of the molecules involved in the tick-host or tick-pathogen relationship. In addition, there is great interest in discovering new molecules with potential for use within biotechnology and pharmacology, which might help in developing new control methods (CHMELAŘ et al, 2016;DÍAZ-MARTÍN et al, 2015;RIBEIRO et al, 2017). The evolutionary context of bloodsucking organisms is another prominent approach that has been studied, through making inferences about the evolution of genes and proteins, thereby helping to improve knowledge about the hematophagic behavior of the arthropods (MANS et al, 2008).…”

“…Peptidases such as cathepsins, legumain, aspartic, metallo and serine proteinase are cited as the main proteolytic enzymes actives in the digestive machinery of hemoglobin (SOJKA et al, 2013). All these peptidases have been identified and characterized by biochemical, proteomic and transcriptomic studies in different tick species, such as Dermacentor variabilis (Say, 1821) (ANDERSON et al, 2008), Rhipicephalus microplus (Canestrini, 1888) (MENDIOLA et al, 1996;KONGSUWAN et al, 2010;HEEKIN et al, 2013), Ixodes ricinus Linneaus, 1758 (SOJKA et al, 2007(SOJKA et al, , 2008(SOJKA et al, , 2013HORN et al, 2009;FRANTA et al, 2010;KOTSYFAKIS et al, 2015;PERNER et al, 2016), Haemaphysalis longicornis Neumann, 1901(KOH et al, 1990BOLDBAATAR et al, 2006), Haemaphysalis flava Neumann 1897 (XU et al, 2016), Ornithodoros tholozani (Laboulbène and Mégnin, 1882) (AKOV et al, 1976), Ornithodoros moubata (Murray, 1877) (GRANDJEAN, 1984) and Ornithodoros erraticus (Lucas, 1849) (OLEAGA et al, 2015).…”

“…Nevertheless even with all the current knowledge about the constituents of the gut, mainly the midgut, little is known about the true role and activity of intestinal proteins from ticks (DÍAZ-MARTÍN et al, 2015;OLEAGA et al, 2015). This is evidenced by the fact that there are scarce transcriptomic studies of gut tissue of ticks, especially with soft ticks.…”