Leishmania

This article is about the parasite. For the infection, see Leishmaniasis.
Leishmania
L. donovani in bone marrow cell
Scientific classification
Domain: Eukaryota
(unranked): Excavata
Phylum: Euglenozoa
Class: Kinetoplastida
Order: Trypanosomatida
Genus: Leishmania
Binomial name
Leishmania
Ross, 1903
Species

L. aethiopica
L. amazonensis
L. arabica
L. archibaldi (disputed species)
L. aristedesi
L. (Viannia) braziliensis
L. chagasi (syn. L. infantum)
L. (Viannia) colombiensis
L. deanei
L. donovani
L. enriettii
L. equatorensis
L. forattinii
L. garnhami
L. gerbili
L. (Viannia) guyanensis
L. herreri
L. hertigi
L. infantum
L. killicki
L. (Viannia) lainsoni
L. major
L. mexicana
L. (Viannia) naiffi
L. (Viannia) panamensis
L. (Viannia) peruviana
L. (Viannia) pifanoi
L. (Viannia) shawi
L. tarentolae
L. tropica
L. turanica
L. venezuelensis

Leishmania /liːʃˈmeɪnɪə/ is a genus of trypanosomes that are responsible for the disease leishmaniasis.[1][2][3] They are spread by sandflies of the genus Phlebotomus in the Old World, and of the genus Lutzomyia in the New World. At least 93 sandfly species are proven or probable vectors worldwide.[4] Their primary hosts are vertebrates; Leishmania commonly infects hyraxes, canids, rodents, and humans.

History

The first written reference to the conspicuous symptoms of cutaneous leishmaniasis surfaced in the Paleotropics within oriental texts dating back to the 7th century BC (allegedly transcribed from sources several hundred years older, between 1500 and 2000 BC[5]). Due to its broad and persistent prevalence throughout antiquity as a mysterious disease of diverse symptomatic outcomes, leishmaniasis has been dubbed with various names ranging from “white leprosy” to “black fever”. Some of these names suggest links to negative cultural beliefs or mythology, which still feed into the social stigmatization of leishmaniasis today.[6] Members of an ancient genus of the Leishmania parasite, Paleoleishmania, have been detected in fossilized sand flies dating back to the early Cretaceous period,[7] however, the causative agent for the disease was only discovered in 1901 as a concurrent finding by William Boog Leishman and Charles Donovan. They independently visualised microscopic single-celled parasites (later called Leishman-Donovan bodies) living within the cells of infected human organs. The parasitic genus would later be classed as Trypanosomatid protozoans under the phylogenetic designation, Leishmania donovani. Several species have since been classified and grouped under two major subgenera i.e. Leishmania Viannia (generally located in the Neotropics) or Leishmania Leishmania (generally located in the Paleotropics, with the major exception of the L. mexicana subgroup).

Epidemiology

Leishmania currently affects 12 million people in 98 countries. About 2 million new cases occur each year, and 21 species are known to cause disease in humans.

Structure

Leishmania species are unicellular eukaryotes having a well-defined nucleus and other cell organelles including kinetoplasts and flagella. Depending on the stage of their lifecycle, they exist in two structural variants, as:[8][9]

  1. The amastigote form is found in the mononuclear phagocytes and circulatory systems of humans. It is an intracellular and nonmotile form, being devoid of external flagella. The short flagellum is embedded at the anterior end without projecting out. It is oval in shape, and measures 3–6 µm in length and 1–3 µm in breadth. The kinetoplast and basal body lie towards the anterior end.
  2. The promastigote form is found in the alimentary tract of sandflies. It is an extracellular and motile form. It is considerably larger and highly elongated, measuring 15-30 µm in length and 5 µm in width. It is spindle-shaped, tapering at both ends. A long flagellum (about the body length) is projected externally at the anterior end. The nucleus lies at the centre, and in front of it are the kinetoplast and the basal body.
L. infantum amastigote forms

Evolution

The details of the evolution of this genus are debated, but Leishmania apparently evolved from an ancestral trypanosome lineage. The oldest lineage is that of the Bodonidae, followed by Trypanosoma brucei, the latter being confined to the African continent. Trypanosoma cruzi groups with trypanosomes from bats, South American mammals, and kangaroos suggest an origin in the Southern Hemisphere. These clades are only distantly related.

The remaining clades in this tree are Blastocrithidia, Herpetomonas, and Phytomonas. The four genera Leptomonas, Crithidia, Leishmania, and Endotrypanum form the terminal branches, suggesting a relatively recent origin. Several of these genera may be polyphyletic and may need further division.[10]

The origins of genus Leishmania itself are unclear.[11][12] One theory proposes an African origin, with migration to the Americas. Another proposes migration from the Americas to the Old World via the Bering Strait land bridge around 15 million years ago. A third theory proposes a palearctic origin.[13] Such migrations would entail subsequent migration of vector and reservoir or successive adaptations along the way. A more recent migration is that of L. infantum from Mediterranean countries to Latin America (known as L. chagasi), since European colonization of the New World, where the parasites picked up their current New World vectors in their respective ecologies.[14] This is the cause of the epidemics now evident. One recent New World epidemic concerns foxhounds in the USA.[15]

Leishmania might have evolved in the Neotropics.[16]

A large data set analysis suggests that Lesihmania evolved 90 million years ago-100 million years ago in Gondwana.[17] The reptile infecting species originated in mammalian clades.

Sauroleishmania species were originally defined on the basis that they infected reptiles (lizards) rather than mammals. Molecular studies have cast doubts on this basis for classification and they have been moved to subgenus status within Leishmania. This subgenus probably evolved from a group that originally infected mammals.[18]

Taxonomy

53 species are recognised in this genus. The status of several of these is disputed, so the final number may differ. At least 20 species infect humans. To make things more complex, hybrids might be involved, as it has been reported in Brazil with an hybrid between Leishmania (V.) guyanensis and Leishmania (V.) shawi shawi.[19]

At least three subgenera exist: Leishmania, Sauroleishmania, and Viannia. The division into the two subgenera (Leishmania and Viannia) was made by Lainson and Shaw in 1987 on the basis of their location within the insect gut. The species in the Viannia subgenus develop in the hind gut: L. (V.) braziliensis has been proposed as the type species for this subgenus. This division has been confirmed by all subsequent studies.

Endotrypanum is also closely related and may also be moved to subgenus status within Leishmania. The subgenus Endotypanum is unique in that the parasites of this subgenus infect the erythrocytes of their hosts (sloths). The species in this subgenus are confined to Central and South America.[20]

Sauroleishmania was originally described by Ranquein 1973 as a separate genus, but molecular studies suggest this is actually a subgenus rather than a separate genus.

A proposed division of the Leishmania is into Euleishmania and Paraleishmania.[21] The proposed groups Paraleishmania would include all the species in the genus Endotypanum and L. colomubensis, L. deanei, L. equatorensis, and L. hertigi. The group Euleishmania would include those species currently placed in the subgenera Leishmania and Viannia. These groups may be accorded subgenus (or other) status at some point, but their positions remains undefined at present.

Five subgenera are been recognised - Leishmania, Paraleishmania, Sauroleishmania, Viannia and the L. enrittii complex. The Endotrypanum genus is now recognised as a division of Paraleishmania.

L. archibaldi may be the same species as L. dononani. L. herreri may belong to the genus Endotypanum rather than to Leishmania.

The enzyme Seltryp which is involved in selenocysteine synthesis appears to be unique to this order.[22] It has been lost in the subgenus Viannia.


Classification

Subgenus Leishmania

Subgenus Sauroleishmania

Subgenus Viannia

The genus Endotrypanum is also included here as this may be reclassified as Leishmania

Genus Endotrypanum

L. enrittii complex

Biochemistry and cell biology

The biochemistry and cell biology of Leishmania is similar to that of other kinetoplastids. They share the same main morphological features; a single flagellum which has an invagination, the flagellar pocket, at its base, a kinetoplast which is found in the single mitochondrion and a subpelicular array of microtubules which make up the main part of the cytoskeleton.

Lipophosphoglycan coat

Leishmania possesses a lipophosphoglycan coat over the outside of the cell. Lipophosphoglycan is a trigger for toll-like receptor 2, a signalling receptor involved in triggering an innate immune response in mammals.

Structure

The precise structure of lipophosphoglycan varies depending on the species and lifecycle stage of the parasite. The glycan component is particularly variable and different lipophosphoglycan variants can be used as a molecular marker for different lifecycle stages. Lectins, a group of plant proteins which bind different glycans, are often used to detect these lipophosphoglycan variants. For example, peanut agglutinin binds a particular lipophosphoglycan found on the surface of the infective form of L. major.

Function

Lipophosphoglycan is used by the parasite to promote its survival in the host and the mechanisms by which the parasite does this center around modulating the immune response of the host. This is vital, as the Leishmania parasites live within macrophages and need to prevent the macrophages from killing them. Lipophosphoglycan has a role in resisting the complement system, inhibiting the oxidative burst response, inducing an inflammation response and preventing natural killer T cells recognising that the macrophage is infected with the Leishmania parasite.

Type Pathogen Location
Cutaneous leishmaniasis (localised and diffuse) infections appear as obvious skin reactions. The most common is the Oriental Sore (caused by Old World species L. major, L. tropica, and L. aethiopica). In the New World, the most common culprits is L. mexicana. Cutaneous infections are most common in Afghanistan, Brazil, Iran, Peru, Saudi Arabia and Syria.
Mucocutaneous leishmaniasis infections start off as a reaction at the bite, and can go by metastasis into the mucous membrane and become fatal. L. braziliensis Mucocutaneous infections are most common in Bolivia, Brazil and Peru. Mucocutaneous infections are also found in Karamay, China Xinjiang Uygur Autonomous Region.
Visceral leishmaniasis infections are often recognised by fever, swelling of the liver and spleen, and anemia. They are known by many local names, of which the most common is probably kala azar,[24][25] Caused exclusively by species of the L. donovani complex (L. donovani, L. infantum syn. L. chagasi).[1] Found in tropical and subtropical areas of all continents except Australia, visceral infections are most common in Bangladesh, Brazil, India, Nepal, and Sudan.[1] Visceral leishmaniasis also found in part of China, such as Sichuan Province, Gansu Province, and Xinjiang Uygur Autonomous Region.

Intracellular mechanism of infection

In order to avoid destruction by the immune system and thrive, the Leishmania 'hides' inside its host's cells. This location enables it to avoid the action of the humoral immune response (because the pathogen is safely inside a cell and outside the open bloodstream), and furthermore it may prevent the immune system from destroying its host through nondanger surface signals which discourage apoptosis. The primary cell types Leishmania infiltrates are phagocytotic cells such as neutrophils and macrophages.[26]

Usually, a phagocytotic immune cell like a macrophage will ingest a pathogen within an enclosed endosome and then fill this endosome with enzymes which digest the pathogen. However, in the case of Leishmania, these enzymes have no effect, allowing the parasite to multiply rapidly. This uninhibited growth of parasites eventually overwhelms the host macrophage or other immune cell, causing it to die.[27]

Transmitted by the sandfly, the protozoan parasites of L. major may switch the strategy of the first immune defense from eating/inflammation/killing to eating/no inflammation/no killing of their host phagocyte and corrupt it for their own benefit. They use the willingly phagocytosing polymorphonuclear neutrophil granulocytes (PMNs) rigorously as a tricky hideout, where they proliferate unrecognized from the immune system and enter the long-lived macrophages to establish a “hidden” infection.

Uptake and survival

Lifecycle of Leishmania

Upon microbial infection, PMNs move out from the bloodstream through the vessels’ endothelial layer, to the site of the infected tissue (dermal tissue after fly bite). They immediately initiate the first immune response and phagocytize the invader by recognition of foreign and activating surfaces on the parasite. Activated PMN secrete chemokines, IL-8 particularly, to attract further granulocytes and stimulate phagocytosis. Further, L. major increases the secretion of IL-8 by PMNs. This mechanism is observed during infection with other obligate intracellular parasites, as well. For microbes like these, multiple intracellular survival mechanisms exist. Surprisingly, the coinjection of apoptotic and viable pathogens causes by far a more fulminate course of disease than injection of only viable parasites. When the anti-inflammatory signal phosphatidylserine usually found on apoptotic cells, is exposed on the surface of dead parasites, L. major switches off the oxidative burst, thereby preventing killing and degradation of the viable pathogen.

In the case of Leishmania, progeny are not generated in PMNs, but in this way they can survive and persist untangled in the primary site of infection. The promastigote forms also release Leishmania chemotactic factor (LCF) to actively recruit neutrophils, but not other leukocytes, for instance monocytes or NK cells. In addition to that, the production of interferon gamma (IFNγ)-inducible protein 10 (IP10) by PMNs is blocked in attendance of Leishmania, what involves the shut down of inflammatory and protective immune response by NK and Th1 cell recruitment. The pathogens stay viable during phagocytosis since their primary hosts, the PMNs, expose apoptotic cell-associated molecular pattern (ACAMP) signaling “no pathogen”.

Persistency and attraction

The lifespan of neutrophil granulocytes is quite short. They circulate in bloodstream for about 6 to 10 hours after leaving bone marrow, whereupon they undergo spontaneous apoptosis. Microbial pathogens have been reported to influence cellular apoptosis by different strategies. Obviously because of the inhibition of caspase3-activation, L. major can induce the delay of neutrophils apoptosis and extend their lifespan for at least 2–3 days. The fact of extended lifespan is very beneficial for the development of infection because the final host cells for these parasites are macrophages, which normally migrate to the sites of infection within two or three days. The pathogens are not dronish; instead they take over the command at the primary site of infection. They induce the production by PMNs of the chemokines MIP-1α and MIP-1β (macrophage inflammatory protein) to recruit macrophages.[28]

Silent phagocytosis theory

To save the integrity of the surrounding tissue from the toxic cell components and proteolytic enzymes contained in neutrophils, the apoptotic PMNs are silently cleared by macrophages. Dying PMNs expose the "eat me"-signal phosphatidylserine which is transferred to the outer leaflet of the plasma membrane during apoptosis. By reason of delayed apoptosis, the parasites that persist in PMNs are taken up into macrophages, employing an absolutely physiological and nonphlogistic process. The strategy of this "silent phagocytosis" has the following advantages for the parasite:

However, studies have shown this is unlikely, as the pathogens are seen to leave apoptopic cells and no evidence is known of macrophage uptake by this method.

Molecular biology

An important aspect of the Leishmania protozoan is its glycoconjugate layer of lipophosphoglycan (LPG). This is held together with a phosphoinositide membrane anchor, and has a tripartite structure consisting of a lipid domain, a neutral hexasaccharide, and a phosphorylated galactose-mannose, with a termination in a neutral cap. Not only do these parasites develop postphlebotomus digestion, but it is also thought to be essential to oxidative bursts, thus allowing passage for infection. Characteristics of intracellular digestion include an endosome fusing with a lysosome, releasing acid hydrolases which degrade DNA, RNA, proteins and carbohydrates.

Genomics

Leishmania tropica

The genomes of four Leishmania species (L. major, L. infantum, L. donovani and L. braziliensis) have been sequenced, revealing more than 8300 protein-coding and 900 RNA genes. Almost 40% of protein-coding genes fall into 662 families containing between two and 500 members. Most of the smaller gene families are tandem arrays of one to three genes, while the larger gene families are often dispersed in tandem arrays at different loci throughout the genome. Each of the 35 or 36 chromosomes is organized into a small number of gene clusters of tens-to-hundreds of genes on the same DNA strand. These clusters can be organized in head-to-head (divergent) or tail-to-tail (convergent) fashion, with the latter often separated by tRNA, rRNA and/or snRNA genes. Transcription of protein-coding genes initiates bidirectionally in the divergent strand-switch regions between gene clusters and extends polycistronically through each gene cluster before terminating in the strand-switch region separating convergent clusters. Leishmania telomeres are usually relatively small, consisting of a few different types of repeat sequence. Evidence can be found for recombination between several different groups of telomeres. The L. major and L. infantum genomes contain only about 50 copies of inactive degenerated Ingi/L1Tc-related elements (DIREs), while L. braziliensis also contains several telomere-associated transposable elements and spliced leader-associated retroelements. The Leishmania genomes share a conserved core proteome of about 6200 genes with the related trypanosomatids Trypanosoma brucei and Trypanosoma cruzi, but around 1000 Leishmania-specific genes are known, which are mostly randomly distributed throughout the genome. Relatively few (about 200) species-specific differences in gene content exist between the three sequenced Leishmania genomes, but about 8% of the genes appear to be evolving at different rates between the three species, indicative of different selective pressures that could be related to disease pathology. About 65% of protein-coding genes currently lack functional assignment.[2]

Leishmania species produce several different heat shock proteins. These incluse Hsp83, a homolog of Hsp90. A regulatory element in the 3' UTR of Hsp83 controls translation of Hsp83 in a temperature-sensitive manner. This region forms a stable RNA structure which melts at higher temperatures.[29]

Sexual reproduction

A microbial pathogen’s reproductive system is one of the basic biologic processes that condition the micoroorganism’s ecology and disease spread.[30] Akopyants et al.[31] demonstrated that L. major has a sexual cycle, including a meiotic process. Hybrid progeny are formed that have full genomic complements from both parents. Mating only occurs in the sand fly vector, and hybrids can be transmitted to the mammalian host by sand fly bite. In L. braziliensis matings in nature are predominantly between related individuals resulting in extreme inbreeding.[32] The rate of outcrossing between different strains of Leishmania in the sand fly vector depends on the frequency of co-infection. Such outcrossing events appear to be rare in L. major [31] and L. donovani.[33]

L. infantum produces proteins BRCA1 and RAD51 that interact with each other to promote homologous recombinational repair.[34] These proteins play a key role in meiosis. Thus, meiotic events provide the adaptive advantage of efficient recombinational repair of DNA damages even when they do not lead to outcrossing.[35]

See also

References

  1. 1 2 3 Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. pp. 749–54. ISBN 0-8385-8529-9.
  2. 1 2 Myler P; Fasel N (editors) (2008). Leishmania: After The Genome. Caister Academic Press. ISBN 978-1-904455-28-8.
  3. ↑ Ansari MY, Equbal A, Dikhit MR, Mansuri R, Rana S, Ali V, Sahoo GC, Das P. (Nov 2015). "Establishment of Correlation between In-Silico &In-Vitro Test Analysis against Leishmania HGPRT to inhibitors". International Journal of Biological Macromolecules 83: 78–96. doi:10.1016/j.ijbiomac.2015.11.051. PMID 26616453.
  4. ↑ WHO (2010) Annual report. Geneva
  5. ↑ Cox, F.E. (2002). "History of human parasitology". Clin Microbiol Rev 15 (4): 595.
  6. ↑ Yanik, M.; et al. (2004). "The psychological impact of cutaneous leishmaniasis". Clin Exp Dermatol 29 (5): 464–467. doi:10.1111/j.1365-2230.2004.01605.x.
  7. ↑ Poinar, G (2008). "Lutzomyia adiketis sp. n. (Diptera: Phlebotomidae), a vector of Paleoleishmania neotropicum sp. n. (Kinetoplastida: Trypanosomatidae) in Dominican amber". Parasit Vectors 1 (1): 2. doi:10.1186/1756-3305-1-22. PMC 2491605. PMID 18627624.
  8. ↑ "Morphology and Life Cycle". UCLA. Retrieved 24 January 2014.
  9. ↑ Pulvertaft, RJ; Hoyle, GF (1960). "Stages in the life-cycle of Leishmania donovani.". Transactions of the Royal Society of Tropical Medicine and Hygiene 54 (2): 191–6. doi:10.1016/0035-9203(60)90057-2. PMID 14435316.
  10. ↑ Hughes, AL; Piontkivska, H. "Phylogeny of Trypanosomatidae and Bodonidae (Kinetoplastida) based on 18S rRNA: evidence for paraphyly of Trypanosoma and six other genera". Mol Biol Evol 20 (4): 644–652. doi:10.1093/molbev/msg062.
  11. ↑ Momen H, Cupolillo E (2000). "Speculations on the origin and evolution of the genus Leishmania". Mem. Inst. Oswaldo Cruz 95 (4): 583–8. doi:10.1590/S0074-02762000000400023. PMID 10904419.
  12. ↑ Noyes HA, Morrison DA, Chance ML, Ellis JT (2000). "Evidence for a neotropical origin of Leishmania". Mem. Inst. Oswaldo Cruz 95 (4): 575–8. doi:10.1590/S0074-02762000000400021. PMID 10904417.
  13. ↑ Kerr SF (2000). "Palaearctic origin of Leishmania". Mem. Inst. Oswaldo Cruz 95 (1): 75–80. doi:10.1590/S0074-02762000000100011. PMID 10656708.
  14. ↑ Kuhls, Katrin; Alam, Mohammad Zahangir; Cupolillo, Elisa; Ferreira, Gabriel Eduardo M.; Mauricio, Isabel L.; Oddone, Rolando; Feliciangeli, M. Dora; Wirth, Thierry; Miles, Michael A.; Schönian, Gabriele; Kamhawi, Shaden (7 June 2011). "Comparative Microsatellite Typing of New World Leishmania infantum Reveals Low Heterogeneity among Populations and Its Recent Old World Origin". PLoS Neglected Tropical Diseases 5 (6): e1155. doi:10.1371/journal.pntd.0001155.
  15. ↑ Duprey, Z. H.; Steurer, F. J.; Rooney, J. A.; Kirchhoff, L. V.; Jackson, J. E.; Rowton, E. D.; Schantz, P. M. (2006). "Canine Visceral Leishmaniasis, United States and Canada, 2000–2003". Emerging Infectious Diseases 12 (3): 440–446. doi:10.3201/eid1203.050811. PMC 3291440. PMID 16704782.
  16. ↑ Noyes, HA; Arana, BA; Chance, ML; Maingon, R (1997). "The Leishmania hertigi (Kinetoplastida; Trypanosomatidae) complex and the lizard Leishmania: their classification and evidence for a neotropical origin of the Leishmania-Endotrypanum clade". J Eukaryot Microbiol 44 (5): 511–557. doi:10.1111/j.1550-7408.1997.tb05732.x.
  17. ↑ Harkins KM, Schwartz RS, Cartwright R, Stone AC (2015) Phylogenomic reconstruction supports supercontinent origins for Leishmania. Infect Genet Evol pii: S1567-1348(15)30060-5. doi: 10.1016/j.meegid.2015.11.030
  18. ↑ Croan, DG; Morrison, DA; Ellis, JT (1997). "Evolution of the genus Leishmania revealed by comparison of DNA and RNA polymerase gene sequences". Mol Biochem Parasitol 89 (2): 149–159.
  19. ↑ Jennings, Y. L.; de Souza, A. A. A.; Ishikawa, E. A.; Shaw, J.; Lainson, R.; Silveira, F. (2014). "Phenotypic characterization of Leishmania spp. causing cutaneous leishmaniasis in the lower Amazon region, western Pará state, Brazil, reveals a putative hybrid parasite, Leishmania (Viannia) guyanensis × Leishmania (Viannia) shawi shawi". Parasite 21: 39. doi:10.1051/parasite/2014039.
  20. ↑ Franco, AM; Grimaldi, G Jr (1999). "Characterization of Endotrypanum (Kinetoplastida: Trypanosomatidae), a unique parasite infecting the neotropical tree sloths (Edentata)". Mem Inst Oswaldo Cruz 94 (2): 261–268. doi:10.1590/s0074-02761999000200026.
  21. ↑ Momen, H; Cupolillo, E (2000). "Speculations on the origin and evolution of the genus Leishmania". Mem Inst Oswaldo Cruz 95 (4): 583–588. doi:10.1590/s0074-02762000000400023.
  22. ↑ Mariana B, Erika K, Irigoín F, Gustavo S, Comini MA (2016) Selenoproteins of African trypanosomes are dispensable for parasite survival in an animal host. Mol Biochem Parasitol pii: S0166-6851(16)30018-4. doi: 10.1016/j.molbiopara.2016.03.002
  23. ↑ Desbois, Nicole; Pratlong, Francine; Quist, Danièle; Dedet, Jean-Pierre (2014). "Leishmania (Leishmania) martiniquensis n. sp. (Kinetoplastida: Trypanosomatidae), description of the parasite responsible for cutaneous leishmaniasis in Martinique Island (French West Indies)". Parasite 21: 12. doi:10.1051/parasite/2014011. ISSN 1776-1042. PMC 3952653. PMID 24626346.
  24. ↑ Visceral leishmniasis: The disease
  25. ↑ kala-azar. The American Heritage Dictionary of the English Language
  26. ↑ Vannier-Santos, MA,; Martiny A; de Souza W. (August 2002). "Cell biology of Leishmania spp.: invading and evading.". Current Pharmaceutical Design 8 (4): 297–318. doi:10.2174/1381612023396230. PMID 11860368.
  27. ↑ Paul, William E. (September 1993). "Infectious Diseases and the Immune System". Scientific American: 94–95.
  28. ↑ Laskay T, et al. (2003). "Neutrophil granulocytes – Trojan horses for Leishmania major and other intracellular microbes?". Trends in Microbiology 11 (5): 210–4. doi:10.1016/S0966-842X(03)00075-1. PMID 12781523.
  29. ↑ David, M; Gabdank, I; Ben-David, M; Zilka, A; Orr, I; Barash, D; Shapira, M (February 2010). "Preferential translation of Hsp83 in Leishmania requires a thermosensitive polypyrimidine-rich element in the 3' UTR and involves scanning of the 5' UTR.". RNA (New York, N.Y.) 16 (2): 364–74. doi:10.1261/rna.1874710. PMC 2811665. PMID 20040590.
  30. ↑ Rougeron V, De Meeûs T, Kako Ouraga S, Hide M, Bañuls AL (2010). ""Everything you always wanted to know about sex (but were afraid to ask)" in Leishmania after two decades of laboratory and field analyses". PLoS Pathog. 6 (8): e1001004. doi:10.1371/journal.ppat.1001004. PMC 2924324. PMID 20808896.
  31. 1 2 Akopyants NS, Kimblin N, Secundino N, Patrick R, Peters N, Lawyer P, Dobson DE, Beverley SM, Sacks DL (April 2009). "Demonstration of genetic exchange during cyclical development of Leishmania in the sand fly vector". Science 324 (5924): 265–8. doi:10.1126/science.1169464. PMC 2729066. PMID 19359589.
  32. ↑ Rougeron V, De Meeûs T, Hide M, Waleckx E, Bermudez H, Arevalo J, Llanos-Cuentas A, Dujardin JC, De Doncker S, Le Ray D, Ayala FJ, Bañuls AL (June 2009). "Extreme inbreeding in Leishmania braziliensis". Proc. Natl. Acad. Sci. U.S.A. 106 (25): 10224–9. doi:10.1073/pnas.0904420106. PMC 2700931. PMID 19497885.
  33. ↑ Rogers MB, Downing T, Smith BA, Imamura H, Sanders M, Svobodova M, Volf P, Berriman M, Cotton JA, Smith DF (January 2014). "Genomic confirmation of hybridisation and recent inbreeding in a vector-isolated Leishmania population". PLoS Genet. 10 (1): e1004092. doi:10.1371/journal.pgen.1004092. PMC 3894156. PMID 24453988.
  34. ↑ Genois MM, Mukherjee A, Ubeda JM, Buisson R, Paquet E, Roy G, Plourde M, Coulombe Y, Ouellette M, Masson JY (August 2012). "Interactions between BRCA2 and RAD51 for promoting homologous recombination in Leishmania infantum". Nucleic Acids Res. 40 (14): 6570–84. doi:10.1093/nar/gks306. PMC 3413117. PMID 22505581.
  35. ↑ Harris Bernstein, Carol Bernstein and Richard E. Michod (2011). Meiosis as an Evolutionary Adaptation for DNA Repair. Chapter 19 in DNA Repair. Inna Kruman editor. InTech Open Publisher. DOI: 10.5772/25117 http://www.intechopen.com/books/dna-repair/meiosis-as-an-evolutionary-adaptation-for-dna-repair

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