Abstract
BackgroundSand fly saliva has been shown to help parasite establishment and to induce immune responses in vertebrate hosts. In the current study, we investigated the pattern of expression of two Phlebotomus papatasi salivary transcripts in specific physiological and seasonal conditions at a hyperendemic area of zoonotic cutaneous leishmaniasis (ZCL) in Iran.MethodsSand flies were collected during 2012–2013, and grouped according to physiological stages such as unfed, fed, semi-gravid, gravid, parous, nulliparous, infected or non-infected with Leishmania major and also based on the season in which they were collected. Quantitative Real-Time PCR was applied for assessment of the expression of two relevant salivary transcripts, PpSP15 and PpSP44, associated to protection from and exacerbation of ZCL, respectively.ResultsThe expression of PpSP15 and PpSP44 transcripts was significantly up-regulated (1.74 and 1.4 folds, respectively) in blood fed compared to unfed flies. Among four groups of fed, unfed, semi-gravid and gravid flies, the lowest levels of PpSP15 and PpSP44 expression were observed in gravid flies. Additionally, the expression levels of both PpSP15 and PpSP44 transcripts in P. papatasi collected during summer were significantly up-regulated (3.7 and 4.4 folds, respectively) compared to spring collections. In addition, the PpSP15 transcript exhibited a significant up-regulation (P < 0.05) in non-infected flies compared to those infected with L. major.ConclusionsThis study contributes to our knowledge of the differential expression of salivary genes among different groups within a P. papatasi population under natural field conditions. Cutaneous and visceral leishmaniasis are of public health importance in many parts of Iran and neighbouring countries where P. papatasi is the proven and dominant sand fly vector for ZCL, the most prevalent and endemic form of the disease in Iran. Therefore, the current study could be helpful in understanding the influence of salivary genes on Leishmania transmission by phlebotomine sand flies. Our findings demonstrate the differential expression of salivary transcripts under various physiological conditions potentially influencing the sand fly capacity for parasite transmission as well as the outcome of disease.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1633-z) contains supplementary material, which is available to authorized users.
Highlights
Sand fly saliva has been shown to help parasite establishment and to induce immune responses in vertebrate hosts
The expression profiles of Phlebotomus papatasi SP15 (PpSP15) and Phlebotomus papatasi SP44 (PpSP44) salivary genes were determined for female P. papatasi sand flies at different physiological stages and in different environmental factors
The authors concluded that no major variation at the genetic and amino acid level of PpSP15 reinforces its suitability as a vaccine candidate
Summary
Sand fly saliva has been shown to help parasite establishment and to induce immune responses in vertebrate hosts. The incidence rate of ZCL in Esfahan Province, a hyperendemic zone of ZCL in central Iran, is reported to be around 2400 cases per year (communication from the Esfahan Center for Public Health). This is considered to be an underestimation of the actual incidence. Sand fly saliva contains a series of bioactive molecules which are necessary for the successful uptake of blood meals and for establishment of Leishmania in vertebrate hosts [5, 6]
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