Proteomics informed by transcriptomics identifies novel secreted proteins in Dermacentor andersoni saliva

Abstract

Dermacentor andersoni, known as the Rocky Mountain wood tick, is found in the western United States and transmits pathogens that cause diseases of veterinary and public health importance including Rocky Mountain spotted fever, tularemia, Colorado tick fever and bovine anaplasmosis. Tick saliva is known to modulate both innate and acquired immune responses, enabling ticks to feed for several days without detection. During feeding ticks subvert host defences such as hemostasis and inflammation, which would otherwise result in coagulation, wound repair and rejection of the tick. Molecular characterization of the proteins and pharmacological molecules secreted in tick saliva offers an opportunity to develop tick vaccines as an alternative to the use of acaricides, as well as new anti-inflammatory drugs. We performed proteomics informed by transcriptomics to identify D. andersoni saliva proteins that are secreted during feeding. The transcript data generated a database of 21,797 consensus sequences, which we used to identify 677 proteins secreted in the saliva of D. andersoni ticks fed for 2 and 5days, following proteomic investigations of whole saliva using mass spectrometry. Salivary gland transcript levels of unfed ticks were compared with 2 and 5day fed ticks to identify genes upregulated early during tick feeding. We cross-referenced the proteomic data with the transcriptomic data to identify 157 proteins of interest for immunomodulation and blood feeding. Proteins of unknown function as well as known immunomodulators were identified.

Subdominant Outer Membrane Antigens in Anaplasma marginale: Conservation, Antigenicity, and Protective Capacity Using Recombinant Protein

“…In this study and a study by Saleh et al, challenge was done using infected ticks. Because tick salivary secretions are immunomodulatory, it is possible that tick feeding potentiates infection such that the level of protection achieved with any immunogen is diminished [33, 44, 45]. …”

De novo assembly and annotation of the salivary gland transcriptome of Rhipicephalus appendiculatus male and female ticks during blood feeding

“…Next generation sequencing, which produces millions of sequencing reads, can achieve the sequence depth required to elucidate even lowly expressed genes of complex protein families. To exploit these advances, a number of de novo sialotranscriptomes (sets of RNA molecules in tick salivary glands) have recently been generated using NGS technologies for a number of tick species; A. maculatum (Karim et al, 2011), Ixodes ricinus (Schwarz et al, 2013), Dermacentor andersoni (Mudenda et al, 2014), A. triste, A. parvum and A. cajennense (Garcia et al, 2014), Haemaphysalis flava (Xu et al, 2015) and R. pulchellus (Tan et al, 2015a). These transcriptomes highlighted the true expansion within salivary protein families in the different tick species and identified new candidate genes involved in feeding.…”

Ixodes scapularistick saliva proteins sequentially secreted every 24h during blood feeding

“…It is interesting to note that both iron and heme-binding proteins were also detected in high abundance in saliva of D. andersoni [51], R. microplus [50], and H. longicornis [52]. However only the latter was detected in this study.…”

“…Additionally one protein was identified in I. scapularis nymphs as an immunogenic protein that bound to human serum from exposure to tick bites [198]. The remaining proteins were found in saliva proteomes of R. microplus (n = 28, [50]), H. longicornis (n = 22, [52]), D. andersoni (n = 2, [51]), O. moubata (n = 5, [53], sequencing of I. scapularis tick saliva by Edman degradation (n = 4) [48], and others were verified as secreted in western blotting studies [42,43,[199][200][201][202][203][204].…”

“…In a related study, saliva of I. scapularis was analyzed by Edman degradation identifying 15 proteins [48]. Recently proteins in saliva of ixodid ticks from replete fed Rhipicephalus sanguineus [49], partial and replete fed Rhipicephalus microplus [50], three and five day fed Dermacentor andersoni [51], and replete fed adult and nymph Haemaphysalis longicornis [52] were identified. In argasid ticks, a lone study identified saliva proteins from twice fed Ornithodoros moubata ticks with saliva collected after 4 months from feeding [53].…”