Specific
IgG subclasses were investigated in two villages (Okoumbi and Ndjokaye) in southeast Gabon with different Loa loa transmission intensities of approximately 9,000 and 1,300 infective larvae (L3) per person per year, respectively.
IgG subclasses were measured by an
enzyme-linked
immunosorbent assay (ELISA) using extracts of L. loa L3, microfilariae (MF), or adult worms. Levels of L3-specific
IgG3 were significantly higher in the village with low transmission (Ndjokaye) (P = 0.006). In contrast, MF-specific
IgG2 was significantly higher in Okoumbi than in Ndjokaye (P = 0.0009). In the high-transmission village (Okoumbi), levels of both MF- and adult-specific
IgG4 were significantly increased in MF carriers compared with amicrofilaremic subjects (P = 0.0015 and P = 0.003, respectively), while levels of L3- and MF-specific
IgG1 were significantly higher in amicrofilaremic individuals compared with MF carriers (P = 0.04 and P = 0.03, respectively). Furthermore, among microfilaremic individuals, the level of the specific
IgG1 subclass was much lower in Okoumbi than in Ndjokaye (P = 0.036). These results suggest that the expression of
antigen-specific
IgG3 and
IgG2 is more likely to vary with transmission intensity, whereas
antigen-specific
IgG4 and
IgG1 varies with adult worm and MF burden.