Leishmania

Question 1

neglected tropical disease

Answer 1

leishmania

Question 2

the Rose of Jericho

Answer 2

Leishmania

Question 3

leishmania parasite

Answer 3

• single cell
• genus: Leishmania
• flagellate
• Trypanosomatidae family

Question 4

vector for Leishmania

Answer 4

female sand fly

Question 5

reservoirs for Leishmania

Answer 5

canines, rodents, humans

Question 6

visceral leishmaniasis

Answer 6

most severe form of leishmania

often seen in countries with lower standards of healthcare

Question 7

disease manifestations of leishmania

Answer 7

partly due to parasite = presence of RNA virus in parasite and immune response

Question 8

life cycle of leishmania

Answer 8

2 stages
- stages in human and stages in sandfly (bio vector)
- human stage = starts after being bitten; sandflies inject saliva after bloodmeal; saliva = inflammation = calls macrophages bc parasites want to be phagocytosed to hitch a ride
- stage of parasite transmitted to humans via sand fly = promastigote
- will transform into amastigotes in macrophages (human stage)
- after bursting = sandfly stage starts; sand fly will ingest macrophages parasite
- amstogotes turn into promastogotes of sandfly
- will divide in midgut and go to proboscis waiting to take another bloodmeal

Question 9

T or F. Leishmania has a sexual stage

Answer 9

F! not yet identified if there is one

Question 10

leishmania disease manifestations

Answer 10

cutaneous or mucocutaneous
- L. major, L. tropica, L. aethiopica (most popular)

Question 11

visceral leishmaniasis

Answer 11

• most severe
• often caused by L. donovani, L. infantum
• Ganges, southern Nepal, Bangladesh, Brazil, etc.
• black sickness, black fever, etc.

Question 12

T or F. A single species of Leishmania can cause more than one type of syndrome

Answer 12

T! AND a syndrome can be caused by more than one species
it all depends on host-parasite interactions

Question 13

two types of Leishmania promastigotes

Answer 13

these are in sandfly
- motile
- metacyclic

Question 14

metacyclic vs motile Leishmania promastigotes

Answer 14

after amastigote stage in humans, motile promastigotes (non-infective insect form) will attach to insect gut, then transform to non-dividing infectious forms (metacyclic promastigotes)

Question 15

transformation stimulus of Leishmania promastigotes depends on many factors, including…

Answer 15

temperature

Question 16

risk factors Leishmania

Answer 16

• poor rural housing conditions, cracked walls, earthen floors
• poor sanitation = garbage attracts sandflies and dogs
• lack of accessible medicines
• if there is conflict = hard to perform vector control and movement of troops
• HIV

Question 17

how to be a good reservoir for leishmaniasis

Answer 17

• Be in close contact with sandflies
• Should be susceptible to the infectious agent
• Should allow replication of the infectious agent to ensure delivery of large numbers to the victim
• Should ideally be the main source of food for the fly
• Disease should develop as a chronic disease giving time for the next transmission season

Question 18

zoonotic leishmaniasis

Answer 18

rural areas
animals to humans via sandflies (mostly skin manifestations)

Question 19

anthroponotic leishmaniasis

Answer 19

densely populated areas
- humans to humans and animals via vector (mostly visceral)

Question 20

how does Leishmania alter the feeding behaviour of sand fly

Answer 20

it makes fly hungrier
- secretes gel-like substance that forms a plug that blocks stomach = allows multiplication of parasites
- nutrient and food doesn’t get through until gel is disturbed
- timing of blood feeding correlated to numbers of metacylic promastigotes (increased biting when numbers of infective parasites increase)

Question 21

how does Leishmania adapt to 2 different hosts to complete its life cycle?

Answer 21

• STAGE SPECIFIC VIRULENCE DETERMINANTS = PHOSPHOGUCANS
  > repeating GalB1, 4Manalpha1-PO4
  > membrane bound lipophosphoglycan (LPG) important for delaying macrophage phagosome-lysosome fusion and for attachment/detachment from insect midgut epithelium
  > number of repeating units vary in the different functional stages (ex: 15 repats in promastigotes increases to 30 repeats in metacyclic promastigotes, elongation facilitates detachment from gut)

Question 22

what are phosphoglucans

Answer 22

they are secreted acid phosphatase + phosphoglycan

Question 23

Leishmania promastigotes characteristics

Answer 23

increased surface glycoprotein GP63 (found on the parasite membrane and aids in internalization of promastigotes)
flagellated
prefers alk pH (sandfly gut)
prefers high glucose conctn

Question 24

what is GP63

Answer 24

a zinc proteinase
also called leishmaniolysin

Question 25

Leishmania amastigote characteristics

Answer 25

reduced GP63 (don't need it in human host) if they have flagella, it's rudimentary prefers acid pH (macrophages) prefer sparse glucose conctn (shift metabolizing fats and proteins)

Question 26

T or F. Monoclonal antibodies made to one promastigotes can react with amastigotes

Answer 26

F! no cross-reaction as they have different expressions of protein, different metabolism and different drug targets should be made for different forms

Question 27

how do Leishmania parasites get in macrophages?

Answer 27

receptor-mediated phagocytosis - macs have surface components (ex: complement receptors CR1, CR3, mannose fucose receptor) = helps the binding of cell to promastigote (MAINLY LPG POTION) - parasites use macrophages as replication vessel

Question 28

Hsp100 is an important virulence factor for which Leishmania species?

Answer 28

L. donovanii and L. major

Question 29

steps to internalization of Leishmania promastigotes

Answer 29

- LPG influence on the phagocytic mechanisms: attachment & hindering endosome-lysosome fusion - Promastigotes internalized in phagosome (survival is dependent on LPG which activates F actin and proteins that delay the interaction of phagosomes with endosomes and lysosomes) - Production of heat shock proteins to protect parasite & contribute to resistance to oxidants Differentiate into amastigotes in phagosomes

Question 30

how does Leishmania destroy macrophages?

Answer 30

- Replicating Leishmania destroy macrophages - Depending on the species, they stay in the lymphatics (cutaneous and mucocutaneous) or disseminate through the reticuloendothelial system (macrophage system) to liver, spleen, and cause further damage and recruitment of T cells (visceral) (granuloma formation) - Decreased numbers of tissue and circulating macrophages cause a type of immunosuppression and shift to Th2 response which furthers the spread of infection - Visceral leishmaniasis is a problem in HIV + individuals

Question 31

Role of the immune system in protection from leishmaniasis

Answer 31

- Abs have no protrective effect; associated with non-healing type of disease syndrome - control of infection has to be mediated by CMI = CD4 T cells esp. important!! - spleen = major site for killing parasites and removal of infected macs and neutrophils

Question 32

tegumentary vs visceral leishmaniasis

Answer 32

disease progression: cutaneous to mucocutaneous to visceral lab diagnosis difficult = unless bone marrow aspirate shows macs with parasites **NEGLECTED DISEASE in Africa**

Question 33

ATL (american tegumentary leishmaniasis)

Answer 33

Disease manifestations: LCL: immunocompetent patients, normally 1-10 ulcerated lesions Diffuse CL: nodules on at least 2 body parts MCL: extensive lesions prone to relapse Disseminated L: immunodeficient patients, numerous nodules, papules and plaques

Question 34

this RNA virus is correlated to clinical severity of leishmaniasis

Answer 34

LRV1

Question 35

localized cutaneous leishmaniasis characteristics

Answer 35

- Well-defined round painless ulcer with raised edges and central crust - May heal spontaneously after ~2 months - Ulcer develops to a typical epitheloid granuloma, predominance of Th1 response - Often leaves a hypopigmented smooth thin scar

Question 36

diffuse cutaneous leishmania characteristics

Answer 36

- ofteen seen in anergic individuals (don't response to immune system), lifelong - Subcutaneous nodules that do not usually ulcerate unless trauma - No cell-mediated immunity that responds to leishmania but might have some antibody production - Invasion of nasal mucosa if disease persists

Question 37

disseminated cutaneous leishmaniasis

Answer 37

- worst of cutaneous leishmaniasis - 10-300 pleomorphic lesions in > 2 different sites of the body - Mucocutaneous lesions found in about 30% of the cases

Question 38

mucocutaneous Leishmanaisis characteristics

Answer 38

- Upper respiratory tract mucosa commonly affected: destruction of walls of oral-nasal and pharyngeal cavities - Usually L. braziliensis; often seen in south America - Can appear years after onset of cutaneous leishmania

Question 39

visceral leishmaniasis

Answer 39

- spleen and liver enlarged - Kala-azar (black fever or fatal illness in Hindi) - Usually “old world leishmaniasis” caused by L. donovani and L. infantum - .5 million new cases/yr, most in India/Nepal - Systemic and most severe form of leishmania - If untreated ~100% mortality rate

Question 40

PKDL

Answer 40

post kala-azar dissimentated leishmaniasis - chronic - granulomatous syndrome that happens after treated VL - we don't know why this happens, autoimmune?; 10% of treated VL

Question 41

HIV & Leishmania

Answer 41

- HIV has changed the profile of Leishmania disease, both diseases target similar immune cell; together are much worse than individually - HIV infection increases risks of getting VL and reduces the chances for successful treatment - VL progresses faster in HIV positive individuals - Co-infected patients are a possible source of drug resistant parasites

Question 42

why is leishmania diagnosis a challenge?

Answer 42

- Disease can mimic malaria, typhoid fever, tuberculosis, sporotrichosis, etc - Parasites sequestered in spleen and lymph nodes = invasive biopsies required to get a good specimen - Molecular techniques are very good, but not practical in many areas with leishmaniasis – resources are not there. - Antibodies – not always present, especially in immunocompromised. Cannot reliably diagnose recurrent disease - Severity is due to several factors – including state of the adaptive immune system and presence of the LRV1 virus in the parasite.

Question 43

how to diagnose leishmania

Answer 43

- could confirm if there is lesion! but very insensitive!! - only 10-30% sensitive by direct smear - ~50% by culture; - PCR is best but only done in reference centres - indirect method = antibodies > BUT sensitivity low, some cross-reactivity with other organisms; IFA, ELISA *problem = many species!*

Question 44

treatment of leishmania

Answer 44

- can clean with topical antiseptics - can treat 2ry bacterial infections - reconstruct damaged tissues **treatment failure common due to complex factors = host, parasite species, drug factors, simultaneous infection of parasite with LRV1**

Question 45

important vaccine considerations for Leishmania vaccine

Answer 45

- vaccine must be feasible since patients get immunity to the particular parasitic species after an infection - need to activate the Th1 arm: (IFNy and IL-12 = CELL IMMUNITY) and not Th2 (Ab)