Biology subjects

Kamhawi, S.

Publications and source records attributed to Kamhawi, S..

2 recordsLinked to original sources

bioRxiv2019

Distinct gene expression patterns in vector-residing Leishmania infantum identify parasite stage-enriched markers

Promastigotes of Leishmania infantum undergo a series of extracellular developmental stages inside the natural sand fly vector Lutzomyia longipalpis to reach the infectious stage, the metacyclic promastigote. There is limited information regarding the expression profile of L. infantum developmental stages inside the sand fly vector, and molecular markers that can distinguish the different parasite stages are lacking. We performed RNAseq on unaltered midguts of the sand fly Lutzomyia longipalpis after infection with L. infantum parasites. RNAseq was carried out at various time points throughout parasite development. Principal component analysis mapped the sequences corresponding to the procyclic, nectomonad, leptomonad or metacyclic promastigote stage into distinct positions, with the procyclic stage being the most divergent population. Transcriptional levels across genes varied on average between 10- to 100-fold. Comparison between procyclic and nectomonad promastigotes resulted in 836 differentially expressed (DE) genes; between nectomonad and leptomonad promastigotes in 113 DE genes; and between leptomonad and metacyclic promastigotes in 302 DE genes. Most of the DE genes do not overlap across stages, highlighting the uniqueness of each stage. Furthermore, the different stages of Leishmania parasites exhibited specific transcriptional enrichment across chromosomes. Using the transcriptional signatures exhibited by distinct Leishmania stages during their development in the sand fly midgut, we determined the genes predominantly enriched in each stage, identifying multiple stage-specific markers for L. Infantum. Leading stage-specific marker candidates include genes encoding a zinc transporter in procyclics, a beta-fructofuranidase in nectomonads, a surface antigen-like protein in leptomonads, and an amastin-like surface protein in metacyclics. Overall, these findings demonstrate the transcriptional plasticity of the Leishmania parasite inside the sand fly vector and provide a repertoire of stage-specific markers for further development as molecular tools for epidemiological studies.

microbiology↗

bioRxiv2019

Phlebotomus papatasi sand fly salivary protein diversity and immune response potential in Egypt and Jordan populations

Phlebotomus papatasi sand flies inject their hosts with a myriad of pharmacologically active salivary proteins to assist with blood feeding and to modulate host defenses. These salivary proteins have been studied for their role in cutaneous leishmaniasis disease outcome with different salivary proteins attenuating or exacerbating lesion size. Studies have shown that while co-administered sand fly saliva exacerbates Leishmania major infections in naive mice, animals pre-exposed to saliva are protected, with the infection attenuated via a delayed-type hypersensitivity immune reaction. These studies highlight the potential of the salivary components to be used as a vaccine. One protein in particular, P. papatasi salivary protein 15 (PpSP15) has been intensively studied because of its ability to protect mice against Le. major challenge. The number of antigenic molecules included in vaccines is restricted thus emphasizing the role of population genetics to identify molecules, like PpSP15, that are functionally significant, conserved across populations and do not experience selection. Three distinct ecotope study sites, one in Egypt (Aswan) and two in Jordan (Swaimeh and Malka), were chosen based on their elevation, rainfall, vegetation, differing reservoir species, and the presence or absence of Le. major. The objective of this work was to analyze the genetic variability of nine of the most abundantly expressed salivary proteins including PpSP12, PpSP14, PpSP28, PpSP29, PpSP30, PpSP32, PpSP36, PpSP42, and PpSP44 and to predict their ability to elicit an immune response. Two proteins, PpSP12 and PpSP14, demonstrated low genetic variability across the three sand fly populations represented in this study, with multiple predicted MHCII epitope binding sites, identified by alleles present in the human populations from the study sites. The other seven salivary proteins revealed greater allelic variation across the same sand fly populations indicating that their use as vaccine targets may prove to be challenging.

genetics↗