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Opsonophagocytic Antibodies to Serotype Ia, Ib, and III Group B Streptococcus among Korean Infants and in Intravenous Immunoglobulin Products

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ABSTRACT

Group B streptococcus (GBS) infection is a leading cause of sepsis and meningitis among infants, and is associated with high rates of morbidity and mortality in many countries. Protection against GBS typically involves antibody-mediated opsonization by phagocytes and complement components. The present study evaluated serotype-specific functional antibodies to GBS among Korean infants and in intravenous immunoglobulin (IVIG) products. An opsonophagocytic killing assay (OPA) was used to calculate the opsonization indices (OIs) of functional antibodies to serotypes Ia, Ib, and III in 19 IVIG products from 5 international manufacturers and among 98 Korean infants (age: 0–11 months). The GBS Ia, Ib, and III serotypes were selected because they are included in a trivalent GBS vaccine formulation that is being developed. The OI values for the IVIG products were 635–5,706 (serotype Ia), 488–1,421 (serotype Ib), and 962–3,315 (serotype III), and none of the IVIG lots exhibited undetectable OI values (< 4). The geometric mean OI values were similar for all 3 serotypes when we compared the Korean manufacturers. The seropositive rate among infants was significantly lower for serotype Ia (18.4%), compared to serotype Ib and serotype III (both, 38.8%). Infant age of ≥ 3 months was positively correlated with the seropositive rates for each serotype. Therefore, only a limited proportion of infants exhibited protective immunity against serotype Ia, Ib, and III GBS infections. IVIG products that exhibit high antibody titers may be a useful therapeutic or preventive measure for infants. Further studies are needed to evaluate additional serotypes and age groups.

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OIs for GBS according to serotype (Ia, Ib, and III) and age among Korean infants (n = 98). The lower limit of detection for the opsonization index was 4. The numbers of individuals in each age group are given in parentheses.OIs = opsonization indices, GBS = group B streptococcus.
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Figure 3: OIs for GBS according to serotype (Ia, Ib, and III) and age among Korean infants (n = 98). The lower limit of detection for the opsonization index was 4. The numbers of individuals in each age group are given in parentheses.OIs = opsonization indices, GBS = group B streptococcus.

Mentions: The OIs of the infants' sera to GBS were 2–119 for serotype Ia, 2–2,486 for serotype Ib, and 2–1,557 for serotype III (Fig. 3). The seropositive rates were 18.4% (18/98) for serotype Ia, 38.8% (38/98) for serotype Ib, and 38.8% (38/98) for serotype III (Table 1). The seropositive rate for serotype Ia was significantly lower, compared to the rates for serotypes Ib or III. The seropositive rates were lowest for all 3 serotypes among infants who were 3–5 months old. The seropositive rates for each serotype were higher among younger infants (0–2 months old). Infant age of ≥ 3 months was positively correlated with the seropositive rates for each serotype. There were positive correlations between age and the OIs against serotypes Ia, Ib, and III (r = 0.49–0.57).


Opsonophagocytic Antibodies to Serotype Ia, Ib, and III Group B Streptococcus among Korean Infants and in Intravenous Immunoglobulin Products
OIs for GBS according to serotype (Ia, Ib, and III) and age among Korean infants (n = 98). The lower limit of detection for the opsonization index was 4. The numbers of individuals in each age group are given in parentheses.OIs = opsonization indices, GBS = group B streptococcus.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383604&req=5

Figure 3: OIs for GBS according to serotype (Ia, Ib, and III) and age among Korean infants (n = 98). The lower limit of detection for the opsonization index was 4. The numbers of individuals in each age group are given in parentheses.OIs = opsonization indices, GBS = group B streptococcus.
Mentions: The OIs of the infants' sera to GBS were 2–119 for serotype Ia, 2–2,486 for serotype Ib, and 2–1,557 for serotype III (Fig. 3). The seropositive rates were 18.4% (18/98) for serotype Ia, 38.8% (38/98) for serotype Ib, and 38.8% (38/98) for serotype III (Table 1). The seropositive rate for serotype Ia was significantly lower, compared to the rates for serotypes Ib or III. The seropositive rates were lowest for all 3 serotypes among infants who were 3–5 months old. The seropositive rates for each serotype were higher among younger infants (0–2 months old). Infant age of ≥ 3 months was positively correlated with the seropositive rates for each serotype. There were positive correlations between age and the OIs against serotypes Ia, Ib, and III (r = 0.49–0.57).

View Article: PubMed Central - PubMed

ABSTRACT

Group B streptococcus (GBS) infection is a leading cause of sepsis and meningitis among infants, and is associated with high rates of morbidity and mortality in many countries. Protection against GBS typically involves antibody-mediated opsonization by phagocytes and complement components. The present study evaluated serotype-specific functional antibodies to GBS among Korean infants and in intravenous immunoglobulin (IVIG) products. An opsonophagocytic killing assay (OPA) was used to calculate the opsonization indices (OIs) of functional antibodies to serotypes Ia, Ib, and III in 19 IVIG products from 5 international manufacturers and among 98 Korean infants (age: 0–11 months). The GBS Ia, Ib, and III serotypes were selected because they are included in a trivalent GBS vaccine formulation that is being developed. The OI values for the IVIG products were 635–5,706 (serotype Ia), 488–1,421 (serotype Ib), and 962–3,315 (serotype III), and none of the IVIG lots exhibited undetectable OI values (< 4). The geometric mean OI values were similar for all 3 serotypes when we compared the Korean manufacturers. The seropositive rate among infants was significantly lower for serotype Ia (18.4%), compared to serotype Ib and serotype III (both, 38.8%). Infant age of ≥ 3 months was positively correlated with the seropositive rates for each serotype. Therefore, only a limited proportion of infants exhibited protective immunity against serotype Ia, Ib, and III GBS infections. IVIG products that exhibit high antibody titers may be a useful therapeutic or preventive measure for infants. Further studies are needed to evaluate additional serotypes and age groups.

No MeSH data available.


Related in: MedlinePlus