RESUMO
We evaluated the functional activity of Haemophilus influenzae B (Hib) antibodies elicited in a group of infants immunized with the diphtheria-tetanus-pertussis vaccine combined with an Hib vaccine produced totally in Brazil after technological transfer of Hib vaccine production from Glaxo SmithKline, Belgium. Blood samples from immunized infants (N = 985) were collected for the determination of Hib antibodies. Total Ig and IgM and IgG subclasses of antibodies against polyribosyl ribitol phosphate (PRP) were analyzed by ELISA. Almost all vaccinees (97.56 percent, 961/985) developed a strong anti-PRP IgG antibody response (¡Ý1.0 ¦Ìg/mL), while an anti-PRP IgM response was observed in 64.24 percent (634/985) of them (¡Ý0.15 ¦Ìg/mL). Only 18.88 percent (186/985) of the infants in the group with high PRP antibody IgG concentrations (¡Ý1.0 ¦Ìg/mL) developed a high IgM antibody response. Anti-PRP IgG antibody levels were significantly higher than anti-PRP IgM. These results demonstrate the predominance of IgG antibodies over IgM antibodies in response to PRP, with a ratio of 17:1. IgG antibodies were predominantly of the IgG1 subclass. An increase in IgG avidity was also observed during the course of immunization.