SOLUBLE HEMOGLOBIN IS A MARKER OF RECENT PLASMODIUM-FALCIPARUM INFECTIONS

Monoclonal antibodies (Mab) were raised against haemoglobin (Hb) assoc iated with Plasmodium falciparum protein and used to develop an ELISA, measuring circulating levels of released Hb. This assay was evaluated in different malaria patients in parallel with ELISA assays for C-rea ctive protein (CRP) and haptoglobin, Levels of Hb were negatively asso ciated with levels of haptoglobin. Increased levels of serum Hb and CR P and decreased levels of haptoglobin were seen in Danish malaria pati ents. Consecutive studies showed that increased Hb levels were detecta ble 3-7 days after initiation of treatment probably because of drug in duced destruction of infected erythrocytes, Increased levels of CRP we re measured 0-3 days after initiation of treatment. The Hb assay was u sed in an epidemiological study of malaria in an area of Sudan with un stable malaria transmission. The proportion of Sudanese adults with de tectable soluble Hb was higher in the rainy season with malaria transm ission compared to the dry season. Hb levels in the rainy season were negatively associated with levels of haptoglobin. Most adults had incr eased levels of soluble Hb and decreased levels of haptoglobin 7 and 3 0 days after their treatment of P. falciparum malaria compared to the levels during acute disease. Thus, both soluble Hb and haptoglobin app ear to be markers of recent P. falciparum infections. Very high levels of CRP protein were measured in some of the malaria patients at the d ay of treatment while lower levels were recorded 7 and 30 days after t reatment. Soluble Hb levels were associated with malariometric paramet ers in a similar fashion to haptoglobin. The new Mab-based assay for m easuring soluble Hb in the peripheral blood of malaria patients may be useful for future epidemiological studies of malaria. (C) 1997 Elsevi er Science B.V.