醫(yī)學(xué)寄生蟲(chóng)學(xué)：利什曼

1、Leishmania Phylum Sarcomastigophora(肉足鞭毛門(mén)）Class Zoomastigophorea（動(dòng)鞭綱）OrderKinetoplastida（動(dòng)基體目）Family Trypanosomatidae (錐蟲(chóng)科）Morphologykinetoplast as characterpromastigoteAmastigote(Leishman-Donovan body,LD body)Life CycleThe parasite lives in the digestive tract of sand flies as promastigoteIn the ma

2、mmalian host parasites multiply as intracellular amastiogotesSand Fly(male, female)Leishmania is transmitted by sand flies (Phlebotomidae)Sand flies are minute diptera (they are more closely related to mosquitoes than “real” flies and only females bite)Only mosquito nets with fine meshwork hold them

3、 offIn the wild sand flies often breed in rodent burrowsOld world Phlebotomus, new world LutzomyaCan also transmit Bartonella bacilliformis (桿狀巴爾通體） and Papatsi virusprocyclics and metacyclicsInfected macrophages are taken up with the blood meal and amastigotes are released by digestion, transform i

4、nto procyclic promastigotes and attach to the midgut epitheliumAttached promastigotes divide rapidly， 24hMetacyclic (infective) promastigotes cease replication, detach and pass forward into the pharynx from where they are regurgitated into the bite site(attached)(detached)Leishmania infects and thri

5、ves in macrophagesWithin its mammalian host Leishmania infects macrophages and replicates as intracellular amastigoeMacrophages are “professional” phagocytic cells and an important part of the innate immune system (they also play a role in initiating the adaptive response by antigen presentation)The

6、 parasite invades its host cell passively by phagocytosisLeishmania infects and thrives in macrophagesUptake of Leishmania amazonensis metacyclic promastigote by a mouse macrophage. The parasite is phagocytosed with the cell body entering first and through the formation of a long tubular pseudopod.

7、(movie 1)Images were captured every 0.5 seconds over the course of 367 seconds. Courret et al. 2002 /cgi/content/full/115/11/2303Leishmania infects and thrives in macrophagesPhagocytosis of a Leishmania amazonensis metacyclic promastigote by a mouse macrophage. The parasite binds to the macrophage p

8、lasma membrane by the tip of the flagellum. It then turns around and is finally ingested via the cell body. (movie 2)Images were captured every 0.5 seconds over the course of 125 seconds. Courret et al. 2002 /cgi/content/full/115/11/2303Leishmania infects and thrives in macrophagesMacrophages are im

9、portant “microbe killers”, however several pathogens have found ways to escape killingTrypansoma cruzi - induces phagocytosis and escapes into the cytoplasm Toxoplasma - active invasion, parasitophorous vacuole is never part of the endocytic pathwayMycobacterium tuberculosis - induce phagocytosis an

10、d block lysosomal maturationLeishmania .Leishmania infects and thrives in macrophagesthrive in a fully matured lysosome with acidic pH and abundant lysosomal hydrolasesrapidly divide and will infect new macrophages after rupture of host cellThe dense surface coat covering Leishmania seems to protect

11、 the parasite from the action of the lytic enzymeswith help from T cells macrophages can be stimulated to kill the parasiteA TH1 response is required for parasite control and healingA TH1 response is required for parasite control and healingNon healing Leishmania infections are characterized by a st

12、rong TH2 response (the response useful to get rid of worms by antibody and hypersensitivity)Healing infections are characterized by TH1The immune protective reaction stays for life longThree syndromes associated with Leishmania infection in humansA variety of species and species complexes causes dis

13、ease in humansVisceral LeishmaniasisLeishmania donovaniLeishmania infantumLeishmania chagasiCutaneous LeishmaniasisLeishmania tropicaLeishmania majorLeishmania aethiopicaMucocutaneous LeishmaniasisLeishmania brazieliensisLeishmania mexicanaLeishmania amazoniensisVisceral Leishmaniasis or Kala AzarSy

14、stemic infection of reticulo-entdothelial cells (mostly macrophages) throughout multiple internal organs (In spleen, liver, bone marrow and other reticuloendothelial centers) and the bloodKala Azar - Visceral LeishmaniasisGeneral infection of macrophages in the entire RESWeeks to months incubation p

15、eriodThe lead symptom is abdominal swelling due to hepato- and splenomegalyHigh fever. Fever often oscillates with a peak every second dayAnemia, monocytosis(單核細(xì)胞增多癥) and neutropenia with granulocytopenia(粒細(xì)胞過(guò)少癥). Progressive drastic weight loss (kachexia)Darkening of the skinMortality of untreated

16、disease 75-95%Post Kala-Azar Dermal LeishmaniasisSequel of visceral leishmaniasis which may manifest years after successful treatment and resolution of Kala Azar.Dermal lesions may contain parasites in great numbersCutaneous LeishmaniasisInfection remains restricted to the initial site of infection

17、(the bite site)Cutaneous LeishmaniasisCutaneous Leishmaniasis is usually self-limitingOld world oriental sore is caused by parasites of the L. tropica complex. (similar disease in the new world is caused by L. mexicana)A chronic but self-limiting dry ulceration at the site of the biteUlceration star

18、ts months after infectionParasites are not found outside the lesionA granuloma is formed which finally leads to healing leaving a depressed scarNearly absolute resistance to reinfectionInoculation to vaccinate has long been practiced in the middle east Espundia or mucocutaenous leishmaniasisCaused b

19、y L. braziliensis20% of infected patients develop ulcers of the oral and nasal mucosaEspundia or mucocutaenous leishmaniasisCaused by L. braziliensis20% of infected patients develop ulcers of the oral and nasal mucosaProgression of the ulceration is slow but steady, ultimately destroying all soft pa

20、rts of the nose, the lips, and the soft palateDeath can occurs through secondary bacterial infectionDiagnosisGold standard of diagnosisis: demonstration of parasites in the blood or lymph (kala azar) or in scrapings of the ulcer (cutaneous versions)Marrow smear (80-90%)Lymph note puncture (40-50%)Ce

21、ll cultureMcAb-AST: Ag?ELISA, IHA, IF: Ab?PCRDip-stickTreatmentTreatment for all forms of Leishmaniasis is not satisfactory at the momentVisceral Leishmaniasis - pentavalent antimonials國(guó)產(chǎn)：斯銻黑克 （Stiviihexonas）Cutaneous - amphotheracin BThe available drugs have significant side effects and resistance

22、has emerged (pentavalent antimonials)HIV coinfection further complicates treatmentNew drugs are urgently needed（One of the new hopes includes paramomycin an old antibiotic which has shown promising activity in clinical studies done by the Institute of One World Health )Leishmania distribution (all s

23、pecies)Leishmaniasis is found in parts of about 88 countries. Approximately 350 million people live in these areas15 million people are infected, with 400,000 new cases annually, in 67 countries. （Low estimated）. Being broadly overlap areas in which HIV infection are increasing, about 1/3 of these p

24、atients die during their first visceral leishmaniasis episode.Ecology of old world LeismaniasisClose contact of humans and their domestic animals can provide optimal conditions for sand flies and Leishmania transmission (stables provide good breeding ground for larvae)In urban environments infection

25、 is mostly human to humanIn rural areas Leishmaniasis can be a zoonosis Infection in dogs is quite frequent in the Mediterranean Ecology of new world leishmaniasisIn the new world most people get infected while working or hunting in the forestHere wild animals including rodents, monkeys and sloths p

26、rovide a reservoir for the parasiteA transmission pattern within a population of wild animals that result in occasional infection of humans is called sylvaticPrevalence in China since 1990s 年發(fā)病人數(shù) 250 350例；6 省: 新疆、內(nèi)蒙、甘肅、陜西、山西、四川；人源型：平原型，已控制，極少皮膚型；犬源型：山丘型，兒童為主、散發(fā)；自然疫源：荒漠型，人90%2歲，散發(fā)More than a 1000 Ame

27、rican soldiers contracted Leishmaniasis in IraqA REGION INFLAMED: Hundreds of U.S. Troops Infected by Parasite Borne by Sand Flies, Army SaysBy DONALD G. MCNEIL JR.Published: December 6, 2003Hundreds of American troops in Iraq have been infected with a parasite spread by biting sand flies, and the l

28、ong-term consequences are still unknown, Army doctors said Friday Prevention ,Block transmission, treat patients, vermicide for sand fly；Kill dogs；SummaryLeishmania species cause three clinical syndromes depending on the spread of the infection in the bodyThe intermediate hosts & vectors are sand fl

29、ies. Leishmania provoke phagocytosis by macrophages and develop intracellular in an fully acidified lysosomeLPG and its interactions with the sand fly midgutPromastigotes attach and detach to the midgut epitheliumAttachment helps them to remain in the insect gut when the blood meal is passedHowever,

30、 later they need to detach to move to the pharynx and proboscis for infectionHow is this accomplished at the molecular level?Lipophosphoglycans play important roles in Leishmania pathogenesisLipophosphglycan or LPG is the dominant molecule on the surface of LeishmaniaLPG is not a protein but a glyco

31、lipidThe molecule is anchored in the membrane by a lipid to which a long chain of highly hydrophilic sugar-phosphate repeats are attachedThe structure of LPG changes over the life cycle to adapt to various functionsLPG is a pathogenesis factor in the mammalian host and important for the life cycle w

32、ithin the sandflyStructural modification of LPG during the sand fly cycleLPG is structurally modified during the developmental process of metacylogenesis (parasites decide to stop replicating and begin to pre-adjust to the mammalian host)LPG in metacylics has 2-3 times the number of repeat unitsSide

33、chains with terminal galactose are downregulated and the remaining galactose residues are capped with another terminal sugar (arabinopyranose)Are these chemical changes responsible for the pathogens attachment phenotype?Only LPG from procyclics attaches to the midgutPhosphoglycans were isolated from

34、 procyclics (those that attach) and metacyclics (those that detach and infect) and were labeled with a dye (resulting in fluorescence seen as white in the lower panels to the right)Opened sandfly midguts were incubated with PG from procyclics (A/B) and metacyclics (C/D) and detected with an antibody

35、Only procyclic phosphoglycan binds to the midgutLPG binds to the microvilli of the sandfly midgut epitheliumOK, LPG appears to be the molecule on the parasite responsible forthe attachment of parasites to the sandfly midgut, but what kind ofhost molecule does it bind to?LPG binds to a species specific galectin in the sandfly midgutA gene for an abundantly expressed galactose binding protein or lectin (galectin) was identified in