Changes in oxidative burst capacity during murine malaria and the effect of vaccination.

Adherent spleen and liver cells from mice infected with Plasmodium yoelii 17X or P. chabaudi AS were tested for production of reactive oxygen intermediates to measure their state of activation. Phorbol myristate acetate (PMA) was used to trigger the respiratory burst and production of superoxide anions was measured by the reduction of nitroblue tetrazolium. Spleen cells from mice infected with P. chabaudi showed an early increase in oxidative activity on day 3, and when the oxidative capacity of the whole spleen was calculated, it was maximal on day 9, just as the mice began to recover. In mice infected with P. yoelii, spleen cells showed an early peak in activity on day 5, and then returned to normal, although the mice did not recover for a further 2-3 weeks. However the total oxidative capacity of the spleen remained high throughout the infection. Mice vaccinated against P. yoelii with a killed blood-stage vaccine showed increased activity on day 3 (spleen) and day 5 (liver), compared with infected control mice. Thus macrophages in these organs could, if given an appropriate trigger, release high levels of these potentially toxic molecules during infection.