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  • Title: Early treatment during a primary malaria infection modifies the development of cross immunity.
    Author: Legorreta-Herrera M, Ventura-Ayala ML, Licona-Chávez RN, Soto-Cruz I, Hernández-Clemente FF.
    Journal: Parasite Immunol; 2004 Jan; 26(1):7-17. PubMed ID: 15198641.
    Abstract:
    We have used a murine model to study the kinetics of cross-protection when a primary infection is halted at different times. We analysed how parasitaemia is modified during a second infection with the homologous parasite, a heterologous parasite, or a mixture of the two. In addition, possible mechanisms involved in cross-protection were analysed. Results show that treatment with pyrimethamine on day 5 during a primary infection with P. chabaudi AS (non-lethal), prevents the generation of cross-protection to a new challenge with lethal P. yoelii 17XL. In contrast, when treatment is on day 7, mice survive a P. yoelii infection. Differences between both groups suggest that in order for 'preimmune' mice to survive a lethal challenge, a predominantly TH2-type response is required, with a higher mRNA expression level of IL-4 and IL-10, and a lower mRNA expression of IFN-gamma. This work shows that an early treatment of a malaria infection produced by a non-lethal parasite drives the immune response towards a loss of cross-protection to further infections, in particular with more virulent parasites. This finding should be taken into account for the development of effective malaria vaccines.
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