Table 3.
Prevalence of the high, intermediate, and low avidity of IgG, IgG1, and IgG3 antibodies to PvDBP-II variants in individuals with patent P. vivax infection
| Antigens | Avidity | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Total IgG (%) | IgG1 (%) | IgG3 (%) | |||||||
| HAI | IAI | LAI | HAI | IAI | LAI | HAI | IAI | LAI | |
| PvDBP-I | 10/27 (37.03) | 12/27 (44.4) | 5/27 (18.5) | 9/23 (39.1) | 12/23 (52.2) | 2/23 (8.7) | 3/8 (37.5) | 5/8 (62.5) | – |
| AI ± SD | 57.7 ± 5.81 | 44.76 ± 2.9 | 23.08 ± 5.86 | 59.5 ± 8.8 | 41.8 ± 6.25 | 16.45 ± 1.2 | 71.3 ± 11.7 | 45.1 ± 6.1 | – |
| PvDBP-VI | 11/27 (40.8) | 11/27 (40.8) | 5/27 (18.5) | 9/23 (39.1) | 12/23 (52.2) | 2/23 (8.7) | 3/8 (37.5) | 4/8 (50) | 1/8 (12.5) |
| AI ± SD | 57.8 ± 7.89 | 40.81 ± 4.39 | 26 ± 5.39 | 59.47 ± 9.65 | 42.9 ± 5.6 | 23.65 ± 8.85 | 71.6 ± 10.56 | 44.1 ± 5.8 | 27.6 |
Avidity index (AI) was calculated by the ratio of the OD value of urea-treated samples to untreated samples multiplied by 100. An AI value less than 30% was considered as low-avidity antibodies, between 30% and 50% was intermediate-avidity antibodies, and greater than 50% was high-avidity antibodies. HAI = high-avidity index; IAI = intermediate-avidity index; LAI = low-avidity index; SD = standard deviation. A significant correlation was observed between AI for IgG and IgG1 and the two variant antigens (r = 0.717, P < 0.0001 and r = 0.567, P = 0.005, respectively; Spearman's correlation test).