FIG. 2.
Some plasma samples contain MSP1 secondary-processing-inhibitory antibodies. Fifty samples (dry season set) chosen at random were analyzed for their ability to inhibit the processing of MSP142 in P. falciparum FCB-1 merozoite preparations. The samples comprised merozoites resuspended in (i) reaction buffer alone (positive control) (no Ab), (ii) reaction buffer followed by immediate solubilization in detergent (zero hour), (iii) reaction buffer after pretreatment with a 10% (vol/vol) plasma sample as indicated (remaining samples shown, individually labeled), (iv) reaction buffer after pretreatment with MAb 12.8 (data not shown), and (v) reaction buffer containing 1 mM phenylmethylsulfonyl fluoride (negative control, data not shown). After 1 h, the samples were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and blotted onto nitrocellulose, and MSP142 and MSP133 were identified and quantified. The results (vertical bars, percent MSP1 processing) are shown for 20 plasma samples. The remainder of the 50 samples analyzed showed either no effect or enhanced MSP1 processing. The MSP119-specific antibody titers of the individual samples are also shown as log reciprocal antibody titers (⧫).