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Comparative Study
. 2017 Mar 22;10(1):152.
doi: 10.1186/s13071-017-2080-1.

A repertoire of protease inhibitor families in Amblyomma americanum and other tick species: inter-species comparative analyses

Lindsay M Porter  1 , Željko M Radulović  1 , Albert Mulenga  2
Affiliations
Comparative Study

A repertoire of protease inhibitor families in Amblyomma americanum and other tick species: inter-species comparative analyses

Lindsay M Porter et al. Parasit Vectors. .

Abstract

Background: Protease inhibitors (PIs) are important regulators of physiology and represent anti-parasitic druggable and vaccine targets. We conducted bioinformatic analyses of genome and transcriptome data to determine the protease inhibitor (PI) repertoire in Amblyomma americanum and in 25 other ixodid tick species. For A. americanum, we compared the PI repertoires in fed and unfed, male and female A. americanum ticks. We also analyzed PI repertoires of female 48, 96 and 120 h-fed midgut (MG) and salivary gland (SG) tissues.

Results: We found 1,595 putative non-redundant PI sequences across 26 ixodid tick species. Ticks express PIs from at least 18 different families: I1, I2, I4, I8, I21, I25, I29, I31, I32, I35, I39, I43, I51, I53, I63, I68, I72 and I74 (MEROPS). The largest PI families were I2, I4 and I8 and lowest in I21, I31, I32, I35 and I68. The majority (75%) of tick PIs putatively inhibit serine proteases, with ~11 and 9% putatively regulating cysteine or metalloprotease-mediated pathways, respectively, and ~4% putatively regulating multiple/mixed protease types. In A. americanum, we found 370 PIs in female and 354 in male ticks. In A. americanum we found 231 and 442 in unfed and fed ticks, respectively. In females, we found 206 and 164 PIs in SG and MG, respectively. The majority of highly cross-tick species conserved PIs were in families I1, I2, I8, I21, I25, I29, I39 and I43.

Conclusions: Ticks appear to express large and diverse repertoires of PIs that primarily target serine protease-mediated pathways. We speculate that PI families with the highest repertoires may contain functionally redundant members while those with the lowest repertoires are functionally non-redundant PIs. We found some highly conserved PIs in the latter category, which we propose as potential candidates for broad-spectrum anti-tick vaccine candidates or druggable targets in tick control.

Keywords: Amblyomma americanum; Hard ticks; Protease inhibitors in ticks.

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Figures

Fig. 1
Fig. 1
PI repertoire for four major medically important tick species. The count of protease inhibitors (PIs) in each PI family for Amblyomma americanum, Amblyomma maculatum, Ixodes scapularis and Ixodes ricinus are shown. PI families where total count was less than ten were excluded from the graphs
Fig. 2
Fig. 2
Amblyomma americanum PI repertoire according to sex, unfed/fed and SG/MG tissues. The count of protease inhibitors (PIs) for each PI family that were found exclusively in males, exclusively in females or in both; found exclusively in unfed ticks, exclusively in fed ticks or found in both; and found exclusively in salivary glands (SG), exclusively in midgut (MG) or found in both are shown. PI families where total count was less than 10 were excluded from the graphs
Fig. 3
Fig. 3
Proportions of tick protease inhibitors (PIs) which are predicted inhibit each protease catalytic type. Tick PIs with putative activity against serine or multiple/mixed activity represent the vast majority of tick PIs. Serpins are shown separately from other PI families showing activity against multiple catalytic types to illustrate that most tick PIs likely do inhibit proteases of the serine catalytic type
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References

    1. Sonenshine DE, Roe RM. Biology of ticks. 2. New York: Oxford University Press; 2014.
    1. Centers for Disease Control and Prevention: Tickborne Diseases of the United States. http://www.cdc.gov/ticks/diseases/. Accessed 1 Aug 2016.
    1. Parola P, Raoult D. Ticks and tickborne bacterial diseases in humans: An emerging infectious threat. Clin Infect Dis. 2001;32:897–928. doi: 10.1086/319347. - DOI - PubMed
    1. Jongejan F, Uilenberg G. The global importance of ticks. Parasitology. 2004;129(Suppl):S3–14. - PubMed
    1. Reichard MV, Edwards AC, Meinkoth JH, Snider TA, Meinkoth KR, Heinz RE, et al. Confirmation of Amblyomma americanum (Acari: Ixodidae) as a vector for Cytauxzoon felis (Piroplasmorida: Theileriidae) to domestic cats. J Med Entomol. 2010;47:890–896. doi: 10.1093/jmedent/47.5.890. - DOI - PubMed

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