Features of helminth infections

1
Features of helminth infections

• Chronic
• Complex life cycles
• Aggregated distributions
• Variable outcome to infection

(Maizels et al. 1993)
2
Variability of infection outcome

• Variability of host response to helminth
• Variable behavior of helminth in response to host

3
The host response to parasites

• Most effective against gastrointestinal parasites
• More often causes the disease rather than
  prevents it
• The overlap of AIDS and parasitic diseases gives
  new clues to important immune responses

4
Immune responses to gastrointestinal helminths

• Mediated by Th-2 CD4 lymphocytes
• They secrete IL-5 which supports recruitment of
  eosinophils
• IL-4/IL-13 support B cell production of IgE
• Bottom line is you force them to let go and then
  you flush the tube

5
Worms and allergy theoryScience 296, 490, 2002
6
These people all have leishmaniasis
7
Leishmania
8
Leishmania infect macrophages, an immune effector
cell
9
Parasite burden(Y-axis) as a function of length
of time of infection(days) in mice of two
different genetic backgrounds
10
Effective immune responses to intracellular
parasites are akin to those seen against
Mycobacterium

• CD4 Th-1 Tcells are the primary effector cells
• IFNgamma is the key cytokine
• These infections(but not malaria or
  schistosomiasis) are significantly worse with AIDS