MRC National Institute for Medical Research, London
Science for Health
Chronic infection maintains immunological memory in malaria
25 November 2010
Protective immunity against Malaria develops only after several infections and can be lost on leaving an area in which malaria is transmitted. Human vaccine trials and mouse models have shown that immunity decays with time after vaccination and that treatment of infection reduces protection. These observations suggest that continuous or repeated exposure to the parasite may be required for the maintenance of immunological protection from malaria, as has also been suggested in Leishmania and other chronic infections.
There have been relatively few studies of CD4+ T cell memory in malaria, however it is known that immunity to the blood stages of Plasmodium is dependent on both CD4+ T cells and B cells. Learning more about the generation and maintenance of memory T cells in malaria and what constitutes a protective CD4 T cell may help in the design of more protective vaccines.
Jean Langhorne (pictured) and Robin Stephens, in NIMR’s Divison of Parasitology, have used a mouse model of a blood-stage malaria infection to examine the memory
response of CD4 T cells during chronic infection. They have shown that these memory CD4 T cells persist in an activated state following infection, produce the inflammatory cytokines TNFα and IFNγ, and are more protective than “resting” memory CD4 T cells obtained from mice in which the infection has been eliminated.
Our current studies suggest a role for cytokine production by memory T cells in long-term protection. This may be one of the reasons why people are better protected against malaria when they are re-infected frequently. It suggests that vaccination methods which enhance production, and survival of cells which maintain effector functions, may be the most successful in protection against severe malaria, although this must be balanced with the well-tuned production of regulatory cytokines.
Jean Langhorne
Memory T cells with an activated phenotype can be distinguished from effector T cells
Click image to view at full-size
Original article
Robin Stephens and Jean Langhorne (2010)
Effector memory Th1 CD4 T cells are maintained in a mouse model of chronic malaria
PLoS Pathogens 6(11): e1001208. Article fulltext.
© MRC National Institute for Medical Research
The Ridgeway, Mill Hill, London NW7 1AA
Top of page