TABLE 2.
Antibody responses to MSP4 proteins in Vietnam residents susceptible to and potentially protected against P. falciparum infection based on the presence or absence of P. falciparum parasitemia during the surveillance period
| Target antigen | Antibody prevalence (%)a
|
Median antibody level (OD)b
|
||||
|---|---|---|---|---|---|---|
| Susceptible (n = 47) | Protected (n = 33) | P (χ2)c | Susceptible (n = 47) | Protected (n = 33) | P (U)c | |
| EcMSP4-His | 80.9 | 84.8 | 0.643 | 0.333 (0.107, 0.633) | 0.246 (0.112, 0.404) | 0.390 |
| ScMSP4-His | 93.6 | 90.9 | 0.651 | 0.296 (0.087, 0.659) | 0.210 (0.089, 0.404) | 0.280 |
| MSP4A | 76.6 | 78.8 | 0.817 | 0.368 (0.098, 1.496) | 0.384 (0.133, 0.900) | 0.864 |
| MSP4B | 91.5 | 84.8 | 0.355 | 0.799 (0.352, 1.759) | 0.541 (0.162, 1.179) | 0.186 |
| MSP4C | 70.2 | 81.8 | 0.238 | 0.285 (0.122, 0.681) | 0.461 (0.168, 1.119) | 0.113 |
| MSP4D | 63.8 | 75.8 | 0.257 | 0.177 (0.048, 0.615) | 0.173 (0.077, 0.383) | 0.657 |
Antibody prevalence is represented as the proportion of positive sera, which are defined as those giving an OD value greater than the mean + 3 standard deviations for the ODs of 30 control sera from nonimmune individuals.
Antibody level is represented as the median (lower quartile, upper quartile) of the OD values.
Antibody prevalence in susceptible and protected individuals is compared using the χ2 test, whereas antibody level in the two different groups is compared using the Mann-Whitney test. P (χ2) and P (U) are the associated levels of significance, respectively. The threshold for significance is 0.0085 after an adjustment is made for the number of comparisons.