Correlation of serum immunoglobulin subclass concentrations with antibody responses of children to immunization with Haemophilus influenzae type b polysaccharide-pertussis vaccine

Species-Specific Chromosome Engineering Greatly Improves Fully Human Polyclonal Antibody Production Profile in Cattle

Large-scale production of fully human IgG (hIgG) or human polyclonal antibodies (hpAbs) by transgenic animals could be useful for human therapy. However, production level of hpAbs in transgenic animals is generally very low, probably due to the fact that evolutionarily unique interspecies-incompatible genomic sequences between human and non-human host species may impede high production of fully hIgG in the non-human environment. To address this issue, we performed species-specific human artificial chromosome (HAC) engineering and tested these engineered HAC in cattle. Our previous study has demonstrated that site-specific genomic chimerization of pre-B cell receptor/B cell receptor (pre-BCR/BCR) components on HAC vectors significantly improves human IgG expression in cattle where the endogenous bovine immunoglobulin genes were knocked out. In this report, hIgG1 class switch regulatory elements were subjected to site-specific genomic chimerization on HAC vectors to further enhance hIgG expression and improve hIgG subclass distribution in cattle. These species-specific modifications in a chromosome scale resulted in much higher production levels of fully hIgG of up to 15 g/L in sera or plasma, the highest ever reported for a transgenic animal system. Transchromosomic (Tc) cattle containing engineered HAC vectors generated hpAbs with high titers against human-origin antigens following immunization. This study clearly demonstrates that species-specific sequence differences in pre-BCR/BCR components and IgG1 class switch regulatory elements between human and bovine are indeed functionally distinct across the two species, and therefore, are responsible for low production of fully hIgG in our early versions of Tc cattle. The high production levels of fully hIgG with hIgG1 subclass dominancy in a large farm animal species achieved here is an important milestone towards broad therapeutic applications of hpAbs.

Characterization of antibodies to capsular polysaccharide antigens of Haemophilus influenzae type b and Streptococcus pneumoniae in human immune globulin intravenous preparations

The most common infections in primary immune deficiency disease (PIDD) patients involve encapsulated bacteria, mainly Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae (pneumococcus). Thus, it is important to know the titers of Hib- and pneumococcus-specific antibodies that are present in immune globulin (Ig) intravenous (IGIV) preparations used to treat PIDD. In this study, seven IGIV preparations were tested by enzyme-linked immunosorbent assay and opsonophagocytic activity for antibody titers to the capsular polysaccharides of Hib and five pneumococcal serotypes. Differences in Hib- and pneumococcus-specific antibody titer were observed among various IGIV preparations, with some products having higher- or lower-than-average titers. Opsonic activity also varied among preparations. As expected, IgG2 was the most active subclass of both binding and opsonic activity except against pneumococcal serotype 6B where IgG3 was the most active. This study determines antibody titers against capsular polysaccharides of Hib and pneumococcus in seven IGIV products that have been shown to be effective in reducing infections in PIDD patients. As donor antibody levels and manufacturing methods continue to change, it may prove useful from a regulatory point of view to reassess IGIV products periodically, to ensure that products maintain antibody levels that are important for the health of IGIV recipients.

Age-dependent Neisseria meningitidis serogroup C class-specific antibody concentrations and bactericidal titers in sera from young children from Montana immunized with a licensed polysaccharide vaccine

Neisseria meningitidis serogroup C bactericidal titers and class-specific enzyme-linked immunosorbent assay (ELISA) antibody concentrations were measured in sera from 173 children (1 to 5 years old) before and 6 weeks and 7 months following vaccination with a quadrivalent (A/C/Y/W-135) polysaccharide vaccine. The immune responses of the children were compared with those of 40 adults 6 weeks postvaccination. Both bactericidal titers and ELISA antibody concentrations were significantly higher in the adults than in the children (P < 0.05). In addition, the ratio of immunoglobulin G (IgG) to IgM was higher in the children than in the adults. With an ELISA total antibody concentration of >/=2 microg/ml used as a measure of seroconversion, >/=84% of the individuals from each age group responded to the serogroup C polysaccharide. However, with a >/=4-fold-increase in bactericidal titer used, only 18% of 1-year-olds, 32% of 2-year-olds, and 50 to 60% of 3-, 4-, and 5-year-olds seroconverted. The ELISA results suggest that >50% of all children retained >/=2 microg of total antibody per ml at 7 months postimmunization. However, the bactericidal titers suggest that <10% of children <4 years old retained a >/=4-fold increase at 7 months following vaccination. Of particular note, 59 of 79 sera (75%) from the 1- and 2-year-olds had high ELISA antibody concentrations (2 to 20 microg/ml) with no associated bactericidal titer (<1:8). Discordant results between bactericidal titers and ELISA antibody concentrations were not explained by the presence of IgA blocking antibody or relative levels of IgG and IgM. The bactericidal results show age-dependent differences in the production and retention of antibody in young children immunized with serogroup C polysaccharide; these differences are not evident with the ELISA data.

Use of licensed vaccines for active immunization of the immunocompromised host

The latter part of the 20th century has witnessed an unprecedented rise in the number of individuals with impaired immunity. This is primarily attributable to the increased development and use of antineoplastic therapy for malignancies, organ and bone marrow transplantation, and the AIDS epidemic. Individuals with impaired immunity are often at increased risk for infections, and they can experience more severe and complicated courses of infection. The lack of therapy for a variety of viruses and the rise in antimicrobial resistance of many pathogens have focused attention on vaccination to prevent infectious diseases. The efficacy of most licensed vaccines has been established in immunocompetent hosts. However, there is also considerable experience with most vaccines in those with impaired immunity. We reviewed the use of licensed live, inactivated, and polysaccharide vaccines in this group, and several themes emerged: (i) most vaccines are less immunogenic in those with impaired immunity than in normal individuals; (ii) live vaccines are generally contraindicated in this group; and (iii) the efficacy of many commonly used vaccines has not been established in people with impaired immunity. This review suggests that for most vaccines there are little or no efficacy data in those with impaired immunity but their use in this patient group is generally safe.

An enzyme-linked immunosorbent assay for quantitation of Haemophilus Influenzae type b polysaccharide-specific IgG1 and IgG2 in human and infant rhesus monkey sera

An enzyme-linked immunosorbent assay (ELISA) has been developed and validated to quantitate IgG1 and IgG2 antibody to polyribosyl-ribitol phosphate (PRP), the capsular polysaccharide of Haemophilus influenzae type b (Hib). The sera of children and infant Rhesus monkeys immunized with an Hib conjugate vaccine composed of Hib PRP covalently linked to an outer membrane protein complex (OMPC) from Neisseria meningitidis serogroup B (PedvaxHIB, PRP-OMPC, Merck, Sharp and Dohme Research Laboratories). The solid-phase antigen employed in the ELISA is a conjugate of PRP to human serum albumin. The enzyme-labeled antibody is alkaline phosphatase-conjugated mouse monoclonal (mAb) anti-human IgG1 or IgG2. A human serum standard was calibrated using parallel titrations with a known antibody standard. The geometric mean titer (GMT) of the anti-PRP IgG1 response to one dose of PedvaxHIB was 3.87 micrograms/ml (n = 82), 11.80 micrograms/ml (n = 62) and 14.57 micrograms/ml (n = 74) in infants and children 12 to 17 months, 18 to 23 months and greater than or equal to 24 months old, respectively. Infants 2 to 11 months old responded with an IgG1 anti-PRP response of 7.10 micrograms/ml while infant monkeys responded with a GMT of 150.65 (n = 9) after two doses of vaccine. The anti-PRP IgG2 GMT responses in all groups were less than 0.25 micrograms/ml, except for humans greater than or equal to 18-months old who exhibited a GMT of greater than or equal to 0.40 micrograms/ml (n = 75). PedvaxHIB, immunization of human infants and children and infant Rhesus monkeys elicits primarily an IgG1 response to PRP. The monkey model appears to be a reliable indicator of the human immune response.

Impaired antibody response to Haemophilus influenzae type b polysaccharide and low IgG2 and IgG4 concentrations in Apache children

BACKGROUND AND METHODS

Because Native American children are at much higher risk for invasive Haemophilus influenzae type b infection than white children, we compared the antibody responses to H. influenzae type b polysaccharide vaccine in healthy Apache and white children.

RESULTS

The concentrations of H. influenzae type b antibody after immunization with polysaccharide vaccine were approximately 10-fold lower in 24-month-old Apache children than in whites of a similar age (P less than 0.01). The decreased response involved H. influenzae type b antibodies of the IgG, IgM, and IgA classes. Concentrations of IgG antibody to tetanus toxoid did not differ significantly, and IgG antibodies to diphtheria toxoid were only twofold lower (P = 0.028). Although total IgG, IgM, and IgA levels were higher in two-year-old Apaches than in whites (all P less than 0.001), IgG2 and IgG4 subclasses were lower (both P less than 0.001). Among the Apaches, individual immunoglobulin levels and allotypes were not significantly correlated with their antibody responses to H. influenzae type b polysaccharide.

CONCLUSIONS

Apache children have significant impairment of their antibody response to H. influenzae type b polysaccharide and little or no impairment of their antibody responses to protein toxoids. This immunodeficiency may explain the high incidence of H. influenzae type b infection in this population.

Selective IgG subclass deficiency: quantification and clinical relevance

Each of the four human IgG subclasses exhibits a unique profile of effector functions relevant to the clearance and elimination of infecting microorganisms. The quantitative response within each IgG subclass varies with the nature of the antigen, its route of entry and, presumably, the form in which it is presented to the immune system. This results in antibody responses to certain antigens being predominantly or exclusively of a single IgG subclass. An inability to produce antibody of the optimally protective isotype can result in a selective immunodeficiency state. This is particularly apparent for responses to certain bacterial carbohydrate antigens that are normally of IgG2 isotype. A failure to produce the appropriate specific antibody response may result in recurrent upper and/or lower respiratory tract infection. Careful patient investigation can identify such deficiencies and suggest appropriate clinical management. In this review we outline the biology and clinical relevance of the IgG subclasses and summarize current rational treatment approaches.

Relationship between serum IgG2 concentrations and antibody responses to pneumococcal polysaccharides in children with chronic chest symptoms

We measured IgG-class antibodies to 12 pneumococcal antigens pre- and post-immunization with polyvalent pneumococcal vaccine in 31 children who had experienced chronic chest symptoms. The purpose of the study was to determine the relation of IgG subclasses, especially IgG2, to the subjects' antibody responses to bacterial polysaccharide antigens, to see if measuring IgG subclasses would predict these responses. Twenty-nine children (90%) had low or low-normal levels of one or more IgG subclasses, including 20 out of 31 (65%) with low or low-normal levels of IgG2. Children studied had a relatively poor increase in levels of antibody to 10 of the 12 pneumococcal vaccine antigens investigated. Both pre- and post-immunization antibody levels were related to pre-immune serum concentrations of IgG2. Pre-immunization antibody levels were strongly related to post-immunization levels; when post-immunization antibody levels were adjusted for pre-immunization levels by partial correlation, the correlation between anticapsular antibody level post-immunization and IgG2 was no longer significant. Thus, in children with chronic chest symptoms, levels of antibody measured at a random interval after natural exposure to these bacterial polysaccharide antigens are related to levels of IgG2 subclass, but antibody increases after vaccination appear to be affected more by other factors.

Serum IgG subclass levels in patients with primary immunodeficiency syndromes or abnormal susceptibility to infections

Serum IgG subclass levels were measured using an indirect competitive immunoenzymatic assay with monoclonal antibodies in 221 patients affected with definite immunodeficiency (ID) syndromes and 229 patients presenting with infection patterns suggestive of ID, but with normal immunoglobulin class levels and no clear evidence of ID. In common variable ID and IgG-IgA deficiency with normal or high IgM, subclass imbalance (mostly IgG1-IgG3 or IgG2-IgG4 deficiency) was the rule, with a higher incidence of severe infections in IgG2-IgG4 defects. One-fifth of patients with IgA deficiency, especially those with autoimmune cytopenia, had subclass deficiencies with no significant correlation with the occurrence of infections. Subclass (mostly IgG2-IgG4) deficiencies were also observed in severe combined ID, defective expression of HLA class II antigens, chronic mucocutaneous candidiasis, and IgM deficiency. Subclass levels were normal in all but one (who was IgG3 deficient) patient with the Wiskott-Aldrich syndrome and in the Buckley's syndrome, except for an unusual patient who presented with low IgG and IgA levels. Subclass (mainly IgG2) deficiency occurred in 24% of infected patients without known ID.