The acute phase response and vitamin A status in malaria

Plasma retinol and 5 carotenes were assayed by high performance liquid chromatography in Thai rural and urban malaria patients and matched control subjects. Plasma retinol was lower in the rural than in the urban controls and both groups of malaria patients had lower serum retinol concentrations than their respective controls. 29% (6/21) of the rural patients were biochemically deficient in retinol (less than or equal to 0.35 mumol/litre), suggesting severely depleted liver stores of vitamin A. The carotene data suggest that the intake of total carotenoids may be 50 to 100% greater than in the UK and that a much higher proportion of dietary beta-carotene is converted to vitamin A than in British adults. The concentrations of non-pro-vitamin A carotenoids in both groups of malaria patients were not compatible with vitamin A deficiency. The differences between patient and control median concentrations of pro-vitamin A (PVA) carotenoids were greater than those of non-PVA carotenoids, suggesting increased utilization of vitamin A in malaria. There was no evidence of clinical vitamin A deficiency in either of the communities studied; therefore, severely depleted stores of retinol are very unlikely. There is an alternative explanation for low plasma retinol levels in malaria patients because retinol is bound to the negative acute phase proteins, retinol binding protein and transthyretin. We suggest that the behaviour of retinol during infection indicates a rapid distribution into extravascular fluids and an increased availability to the tissues; i.e., it may be another beneficial effect of the acute phase response.