862 Transplacental transmission of serotype-specific pneumococcal antibodies in a Brazilian population

Abstract

The highest incidence of severe pneumococcal infections in children occurs in the first 6 months of life; however, immunization of infants with the existing polysaccharide vaccines is ineffective. We wished to determine the prevalence of immunoglobulin G (IgG) pneumococcal antibodies in unimmunized Brazilian mothers and their transplacental transmission to term and preterm infants. Total IgG, IgG1 and -2 subclass levels, and IgG antibodies against Streptococcus pneumoniae serotypes 1, 3, 6B, 9V, and 14 were determined in 15 pairs of mothers and term newborns (gestational age, >37 weeks) and in 18 pairs of mothers and preterm newborns (gestational age, 32 to 36 weeks). Serotype-specific anti-pneumococcal antibodies were detected by a recently standardized enzyme-linked immunosorbent assay calibrated with the 89-SF reference serum. Varying percentages of the mothers had antibody concentrations below arbitrarily defined protective levels: 33% for serotype 1, 67% for serotype 3, 30% for serotype 6B, 52% for serotype 9V, and 22% for serotype 14. In term newborns, IgG1 concentrations were slightly higher than maternal concentrations; in preterm newborns, the concentrations were much lower. Concentrations of IgG2 in term and preterm infants were significantly lower than in the mothers. Transplacental transmission of antibodies to serotypes 3 and 14 was clearly different from that of antibodies to serotypes 1, 6B, and 9V. Concentrations of IgG antibodies against serotypes 3 and 14 were similar to or higher than those of the mothers; against serotypes 1, 6B, and 9V they ranged from 77 to 83% of maternal concentrations in term newborns and also in preterm infants, although transplacental transmission of antibodies was proportionally lower for each specific serotype in preterm than in term infants. These data are relevant for developing strategies to protect infants against pneumococcal infections in the first months of life. Our findings and a review of existing information stress the importance of understanding the relationships among pneumococcal immunization, IgG subclass antibodies to individual serotypes, transplacental transport, half-life, and antibody function and their protective values against infection.Pneumococcal infections cause high morbidity and mortality in children during the first 2 years of life, with the highest incidence of severe, systemic pneumococcal infections occurring in the first year of life (15,18). Immunization of infants with the existing polysaccharide vaccines, however, becomes effective only after 2 years of age.Conjugate pneumococcal vaccines containing five or seven polysaccharides have been found to be immunogenic in the first year of life in several studies (1,3,31). However, these vaccines are still experimental and the small number of serotype polysaccharides included in the vaccines may limit the coverage they offer. A 10-year study of 308 cases of meningitis in children under 2 years of age in São Paulo, Brazil (48), reveals that vaccine formula B, which includes serotypes 1, 5,...

Effects of Absorption with Pneumococcal Type 22F Polysaccharide on Maternal, Cord Blood, and Infant Immunoglobulin G Antipneumococcal Polysaccharide Antibodies

“…Transmission rates for both absorbed and nonabsorbed antibodies ranged from 0.34 to 0.65. These results confirm prior observations of significantly lower antibody concentrations in the cord blood than in the mother despite significantly greater total IgG concentrations in cord blood than in maternal blood (1,6,8). The lower ratio may be explained by the fact that antipneumococcal antibodies are predominantly IgG2 antibodies, which are not transported across the placenta as well as IgG1 antibodies, as shown in a previous study on transplacental transmission of serotype-specific pneumococcal antibodies in a Brazilian population (5).…”

“…These results for infants were expected since IgG antibodies found in cord blood and early infancy are maternal antibodies transmitted across the transplacental barrier (1,8). Transmission rates for both absorbed and nonabsorbed antibodies ranged from 0.34 to 0.65.…”

“…In contrast, the transmission of antibodies to serotypes 1, 6B, and 9V ranged from 77 to 83%, suggesting a predominant IgG2 response to these serotypes (8). Maternal antibody concentrations were measured at the time of delivery in the Brazilian study.…”

“…Some protection against invasive infections in the first few months of life is afforded by the transplacental transfer of maternal antibodies. The concentration of antibodies measured in cord blood samples is related to the concentration of antibodies present in unimmunized mothers (6,1,8), as well as in mothers immunized with the 23-valent pneumococcal polysaccharide vaccine during pregnancy (16,14,12).…”

Influence of Patient Age on Streptococcus pneumoniae Serotypes Causing Invasive Disease

“…Transplacental transmission of immunoglobulin G (IgG) antibodies is very efficient for serotypes 3 and 14 (5), so that this is an unlikely explanation for the absence of serotype 3 infections and the high incidence of serotype 14 infections in young children. Furthermore, transplacentally transmitted antibodies decrease rapidly during the first 6 months of life (22).…”