We have previously provided conclusive evidence that the invertebrate stages of Leishmania are fully capable of a sexual cycle during their growth and development in the sand fly vector. The priority of our studies in 2012 has been to extend the findings of sexual competence to other species and strains of Leishmania and to additional sand fly vector species. We have been able to recover L. major hybrids from Lutzomyia longipalpis, demonstrating that the main genus of sand flies found in the New World are capable of supporting the sexual reproductive cycle of the Leishmania parasites that they transmit. Hybrids were recovered as early as three days post infection, indicating that early developmental stages, e.g. procyclic and/or nectomonad promastigotes, are able to mate. We have also been able to successfully cross L. major sub-strains from West Africa, the Middle East, and Southern Russia, demonstrating that L. major isolates from across the full range of their geographic distribution are sexually competent. Furthermore, we have been able for the first time to generate interspecies hybrids between L. major and L. infantum. The occurrence of intra- and inter-species allelic hybrids amongst natural populations has been substantiated by multi-locus genotyping of over 300 strains. The differentiation of midgut promastigotes into the infectious, metacyclic stage is essential for the development of transmissible infections. We have been able to predict transmission success based on the efficiency of this differentiation process in the anterior midgut. Meta-analysis of multiple transmission experiments allowed us to establish a percent-metacyclic cutoff value that strongly predicted transmission competence. We have also identified the normal midgut microbiome as an essential factor controlling metacyclogenesis. L. major infected P. duboscqi sand flies treated with penicillin/streptomycin were completely inhibited in their ability to support the normal differentiation of promastigotes into the metacyclic stage. The bacterial diversity in normal and antibiotic treated flies was characterized by both culture dependent and independent methods by sequencing of the 16s rDNA. The possible roles of the normal bacterial communities in providing nutritional supplements essential to parasite differentiation, or displacement of the normal midgut microbiota by communities that are harmful to the parasite, will be investigated in future studies.

Project Start
Project End
Budget Start
Budget End
Support Year
31
Fiscal Year
2012
Total Cost
$545,955
Indirect Cost
City
State
Country
Zip Code
Inbar, Ehud; Lawyer, Philip; Sacks, David et al. (2016) The Potential Use of Forensic DNA Methods Applied to Sand Fly Blood Meal Analysis to Identify the Infection Reservoirs of Anthroponotic Visceral Leishmaniasis. PLoS Negl Trop Dis 10:e0004706
Sacks, David (2015) Gateway to deLiver: How malaria sporozoites cross the sinusoidal barrier. J Exp Med 212:1340
Romano, Audrey; Inbar, Ehud; Debrabant, Alain et al. (2014) Cross-species genetic exchange between visceral and cutaneous strains of Leishmania in the sand fly vector. Proc Natl Acad Sci U S A 111:16808-13
Inbar, Ehud; Akopyants, Natalia S; Charmoy, Melanie et al. (2013) The mating competence of geographically diverse Leishmania major strains in their natural and unnatural sand fly vectors. PLoS Genet 9:e1003672
Stamper, Lisa W; Patrick, Rachel L; Fay, Michael P et al. (2011) Infection parameters in the sand fly vector that predict transmission of Leishmania major. PLoS Negl Trop Dis 5:e1288
Secundino, Nagila; Kimblin, Nicola; Peters, Nathan C et al. (2010) Proteophosphoglycan confers resistance of Leishmania major to midgut digestive enzymes induced by blood feeding in vector sand flies. Cell Microbiol 12:906-18
Dobson, Deborah E; Kamhawi, Shaden; Lawyer, Phillip et al. (2010) Leishmania major survival in selective Phlebotomus papatasi sand fly vector requires a specific SCG-encoded lipophosphoglycan galactosylation pattern. PLoS Pathog 6:e1001185
Akopyants, Natalia S; Kimblin, Nicola; Secundino, Nagila et al. (2009) Demonstration of genetic exchange during cyclical development of Leishmania in the sand fly vector. Science 324:265-8
Peters, Nathan C; Sacks, David L (2009) The impact of vector-mediated neutrophil recruitment on cutaneous leishmaniasis. Cell Microbiol 11:1290-6
Kimblin, Nicola; Peters, Nathan; Debrabant, Alain et al. (2008) Quantification of the infectious dose of Leishmania major transmitted to the skin by single sand flies. Proc Natl Acad Sci U S A 105:10125-30

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