Comparison of nonhuman primate antibodies against Haemophilus influenzae type b polysaccharide with human antibodies in oligoclonality and in vivo protective potency

Feto-placental adaptations to maternal obesity in the baboon

Maternal obesity is present in 20-34% of pregnant women and has been associated with both intrauterine growth restriction and large-for-gestational age fetuses. While fetal and placental functions have been extensively studied in the baboon, no data are available on the effect of maternal obesity on placental structure and function in this species. We hypothesize that maternal obesity in the baboon is associated with a maternal inflammatory state and induces structural and functional changes in the placenta. The major findings of this study were: 1) decreased placental syncytiotrophoblast amplification factor, intact syncytiotrophoblast endoplasmic reticulum structure and decreased system A placental amino acid transport in obese animals; 2) fetal serum amino acid composition and mononuclear cells (PBMC) transcriptome were different in fetuses from obese compared with non-obese animals; and 3) maternal obesity in humans and baboons is similar in regard to increased placental and adipose tissue macrophage infiltration, increased CD14 expression in maternal PBMC and maternal hyperleptinemia. In summary, these data demonstrate that in obese baboons in the absence of increased fetal weight, placental and fetal phenotype are consistent with those described for large-for-gestational age human fetuses.

Phenotypic changes associated with advancing gestation in maternal and fetal baboon lymphocytes

Baboons are very similar to humans in ontogeny, reproductive physiology, and placentation, and thus serve as an excellent nonhuman primate model for use in both normative and perturbation studies of pregnancy that cannot be performed on pregnant women. However, little is known about the changes induced by normal pregnancy in the maternal and fetal baboon in lymphocyte subset composition, and lymphocyte activation and proliferation. We performed multicolor flow cytometry analysis of peripheral venous blood samples obtained from pregnant baboons at mid-gestation (0.5 G), and from matched fetal heart (FH) and umbilical cord (UC) blood at the end of gestation (0.95 G). Compared with their mothers at 0.95 G, fetal lymphocytes had higher percentages of B and CD4+ T cells, and lower numbers of NK and CD8+ T cells. When comparing pregnant baboons at 0.5 and 0.95 G, we also found that pregnancy induces immune stimulation, measured as higher activation without proliferation of CD8+ T and NK cells in the maternal circulation. Our study adds new data to support the notion of pregnancy-induced immune activation and strengthens the value of the baboon as a nonhuman primate model for studies pertinent to human reproductive physiology, pathology, and vaccination.

The baboon as a nonhuman primate model for assessing the effects of maternal immunization with Haemophilus influenzae type b polysaccharide vaccines

These studies were performed to assess the utility of the baboon as a nonhuman primate model to evaluate vaccines for use in humans. Specifically, we examined the antibody response of baboons immunized during the third trimester of pregnancy with Haemophilus influenzae type b (Hib) polyribosylribitol phosphate (PRP) conjugate and unconjugated polysaccharide vaccines. Some of the vaccinated mothers failed to respond to a single immunization with unconjugated Hib PRP. Specific Hib PRP immunoglobulin G (IgG) but not IgM antibodies cross the baboon placenta and are detected in the offspring. Higher-titer baboon anti-Hib PRP did not express two previously defined cross-reactive human anti-Hib PRP idiotypes and was biased towards lambda light-chain expression. Spectrotype analysis indicated that baboon anti-Hib PRP was restricted in heterogeneity and oligoclonal.

Association of placental transfer of anti-Haemophilus influenzae type b polysaccharide antibodies with their V regions

Immunization of mothers during pregnancy may be an effective means of providing protection to infants during the first months of life against many pathogens. Previous studies have identified factors that influence the transfer of immunoglobulin across the placenta, including the time of vaccination during pregnancy and isotypes of specific immunoglobulins. By studying antibodies to Haemophilus influenzae type b polysaccharide (Hib-PS) in 26 pairs of maternal-cord sera obtained from unimmunized healthy women and 22 pairs of maternal-cord sera from women immunized with one of three different Hib vaccines, we have found that the immunoglobulin transfer is also dependent on the V region of antibodies. Anti-Hib-PS derived from the V kappa II gene "A2" was transferred about ten times more efficiently to the fetus than other anti-Hib-PS antibodies (20% vs 1-2%). It was found that antibodies derived from the A2 V kappa gene are primarily IgG whereas other antibodies are preferentially associated with the IgM isotype. The potential association between the antibody V region with preferential placental transfer should be considered for future studies involving maternal immunization.

Serologic crossreactions among primate immunoglobulins

We have generated and characterized 50 murine monoclonal antibodies (mAb) specific for baboon IgG. We examined crossreactivity of these mAb to baboon IgM and immunoglobulin (Ig) of various other primates including human, chimpanzee, rhesus monkey, cynomolgus monkey, and African green monkey. Those mAB that crossreacted with human IgG were further examined using myeloma proteins for specificity to human Ig subclasses. One mAB crossreacted with all four human IgG subclasses and with human IgM. We further analyzed this reactivity utilizing Bence Jones proteins representative of various light (L) chain germline gene family products. This mAB reacted with Bence Jones proteins indicating the recognition of a kappa (k) L chain specificity associated with the kappa I, kappa III, and kappa IV subgroups, but not with kappa II. Based on the differences between kappa II germ line gene encoded L chains and the other kappa L chain subgroups, we ascribe this reactivity to six amino acids that define a discontinuous epitope.

Haemophilus influenzae: then and now

Haemophilus influenzae has long been recognised as a major cause of serious infection and mortality in children less than 5 years old. Prior to the introduction of Haemophilus influenzae type b (Hib) immunisation, the incidence of a child suffering an invasive Haemophilus infection was 20-50/100,000 in industrialised countries and up to ten times higher in developing regions. The introduction of a Hib vaccine programme results in a rapid and dramatic decline in the incidence of Hib infection in the susceptible childhood population. For example, within two years of the introduction of routine Hib vaccination of infants in the UK, the risk of serious Hib infection had fallen from 1:600 to 1:30,000 by 5 years of age. Many other European countries have introduced, or are in the process of introducing, a routine Hib immunisation programme. Because the epidemiology of Haemophilus influenzae infection is changing so dramatically, it is opportune to review Haemophilus influenzae as it was perceived in the pre-vaccine era (the past) and during vaccine implementation (the present), and how its role may change in the post-vaccination era (the future). This review will summarise the historical landmarks that have led to our present-day understanding of Haemophilus influenzae pathogenicity, the concerns about antibiotic resistance, the features of the host immune response to Haemophilus influenzae, and the introduction of the Hib vaccine. Furthermore, the possible importance of this organism in the future will be discussed.