Mother-Infant Antibodies to Pneumococcal Polysaccharides and Proteins : Transfer and Persistence of Maternal Antibodies and Development of Vaccine-Induced and Naturally Acquired Antibodies in Infants

Symptomless nasopharyngeal carriage of Streptococcus pneumoniae (pneumococcus) is very common in young children. Occasionally the carriage proceeds into mild mucosal diseases, such as sinusitis or acute otitis media, or into serious life-threatening diseases, such as pneumonia, sepsis or meningitis. Each year, up to one million children less than five years of age worldwide die of invasive pneumococcal diseases (IPD). Especially in the low-income countries IPD is a leading health problem in infants; 75% of all IPD cases occur before one year of age. This stresses the need of increased protection against pneumococcus in infancy. Anti-pneumococcal antibodies form an important component in the defence against pneumococcal infection. Maternal immunisation and early infant immunisation are two possible ways by which potentially protective antibody concentrations against pneumococci could be achieved in early infancy. The aim of this thesis is to increase the knowledge of antibody mediated protection against pneumococcal disease in infants and young children. We investigated the transfer of maternal anti-pneumococcal antibodies from Filipino mothers to their infants, the persistence of the transferred antibodies in the infants, the immunogenicity of the 23-valent pneumococcal polysaccharide vaccine (PPV) in infants and the response of the children to a second dose of PPV at three years of age. We also investigated the development of antibodies to pneumococcal protein antigens in relation to culture-confirmed pneumococcal carriage in infants. Serum samples were collected from the mothers, the umbilical cords and from the infants at young age as well as at three years of age. The samples were used to determine the antibody concentrations to pneumococcal serotypes 1, 5, 6B, 14, 18C and 19F, as well as to the pneumococcal proteins PspA, PsaA, Ply, PspC, PhtD, PhtDC and LytC by the enzyme immunoassay. The findings of the present study confirm previously obtained results and add to the global knowledge of responses to PPV in young children. Immunising pregnant women with PPV provides the infants with increased concentrations of pneumococcal polysaccharide antibodies. Of the six serotypes examined, serotypes 1 and 5 were immunogenic already in infants. At three years of age, the children responded well to the second dose of PPV suggesting that maternal and early infant immunisations might not induce hyporesponsiveness to polysaccharide antigens after subsequent immunisations. The anti-protein antibody findings provide useful information for the development of pneumococcal protein vaccines. All six proteins studied were immunogenic in infancy and the development of anti-protein antibodies started early in life in relation to pneumococcal carriage.

Antigenic determinants on chicken riboflavin carrier protein. A study with monoclonal antibodies

Monoclonal antibodies raised against chicken egg white riboflavin carrier protein were classified into seven categories each recognizing a distinct epitope. Of these, six were directed against conformation dependent epitopes and one to a sequential epitope. The roles of lysine residues and the post-translationally attached phosphate and oligosaccharide moieties in the antigenicity of riboflavin carrier protein recognized by the monoclonal antibodies were investigated. The binding region of three monoclonal antibodies could be located within the 87–219 amino acid sequence of the protein and one antibody among these recognized a sequence of 182–204 amino acid residues. All the monoclonal antibodies were able to recognize riboflavin carrier proteins present in the sera of pregnant rats, cows and humans indicating that the epitopes to which they are directed are conserved through evolution from chicken to the human.

Detection of IgG, IgA, IgM and IgE Antibodies in Invasive Amoebiasis in Endemic Areas

Entamoeba histolytica-specific serum IgG, IgA, IgM and IgE antibodies were assayed in cases of amoebiasis in an endemic area. Patient groups consisted of amoebic liver abscess (n=18), pre-abscess hepatic amoebiasis (n=22) and amoebic colitis (n=30). Control subjects comprised 26 asymptomatic cyst passers, 13 giardiasis cases, 20 typhoid patients and 24 non-amoebic individuals. Serum IgG was assayed by ELISA, using a monoclonal anti IgG β- galactosidase (IgG β-gal) conjugate, a polyclonal avidin biotin horse radish peroxidase (AB-HRP), and a polyclonal anti IgG horse radish peroxidase (IgG HRP) conjugate. IgA and IgM were assayed by the β-gal ELISA and IgE by AB-HRP. Diagnostically significant IgG and IgA while lower IgM and IgE antibody levels were seen in extraintestinal cases. About 40% of suspected pre-abscess hepatic amoebiasis cases were confirmed by antibody estimation. All isotype levels in most dysentery cases were in the range of the controls.

Demonstration of IgE Antibodies to Nucleic Acid Antigens in Patients with Sle

Using a combination of avidin-biotin microELISA and solid phase radioimmunoassay, we examined sera from 23 patients with systemic lupus erythematosus (SLE), two patients with established sensitivity to ingested shrimp, and 15 healthy normal subjects. In addition to IgG antibodies, varying amounts of IgE antibodies specific for native DNA (nDNA), denatured or single-stranded DNA (dnDNA), RNA, and tRNA were demonstrable in the sera of SLE patients, but not in the sera of normal subjects. A comparison of the specificity of nucleic acid-specific IgE antibodies present in the sera of shrimp-sensitive patients with those present in the sera of seven SLE patients revealed that the IgE antibodies in the sera of shrimp-sensitive patients specifically recognized shrimp tRNA but not yeast tRNA, calf thymus RNA, or calf thymus DNA, while those present in the sera of patients with SLE recognized all these nucleic acid antigens. The IgE antibodies directed against nDNA, dnDNA, RNA, and tRNA may mediate mast cell and basophil degranulation and thus contribute both to immediate-type hypersensitivity phenomena including hives seen in patients with SLE and to the localization of IgE-nucleic acid complexes in target

Common epitopes of serum retinol-binding proteins: a study with monoclonal antibodies

Monoclonal antibodies were raised against purified chicken retinol-binding protein. These were characterised extensively with respect to their ability to recognize retinol-binding proteins from different species. The monoclonal antibodies exhibited differential recognition characteristics. Though the majority presented restricted reactivities, one out of the four monoclonal antibodies studied cross-reacted with retinol-binding proteins from all species tested so far.

Antigenic determinants of human serum retinol binding protein as probed with monoclonal antibodies

Monoclonal antibodies raised against human serum retinol-binding protein (hRBP) were used as probes for the study of the antigenic determinants of hRBP and those shared with the same protein from other species. The antibodies could be classified into four distinct groups and react with the homologous proteins from the rat as well as the rabbit sera. Three of these antibodies recognize sequential or continuous epitopes while the remaining antibody is directed against a discontinuous or conformational epitope. By chemical cleavage with cyanogen bromide, the domains recognized by the monoclonal antibodies could be delineated. By solid-phase synthetic approach, the core sequences recognized by two of these monoclonal antibodies were identified to amino acid sequences 45–51 and 128–131 of the primary amino acid sequence of hRBP.

Architecture of Physalis Mottle Tymovirus as Probed by Monoclonal Antibodies and Cross-Linking Studies

Physalis mottle tymovirus (previously named belladonna mottle virus, Iowa strain) RNA was cross-linked to its coat protein by exposure of the intact virus to ultraviolet light. The site of cross-linking of the coat protein with the RNA was identified as Lys-10 by sequencing the oligonucleotide-linked tryptic peptide obtained upon HPLC separation subsequent to enzymetic digestion of the cross-linked and dissociated virus. Three monoclonal antibodies PA3B2, PB5G9, and PF12C9, obtained using denatured coat protein as antigen, cross-reacted effectively with the intact virus indicating that the epitopes recognized by these monoclonals are on the surface of the virus. Using the peptides generated by digestion with CNBr, clostripain, V-8 protease, or trypsin and a recombinant protein lacking the N-terminal 21 residues expressed from a cDNA clone, it was shown that PA3B2 recognizes the sequence 22-36 on the coat protein while PB5G9 and PF12C9 recognize region 75-110. These results suggest that Lys-10 is one of the specific sites through which the RNA interacts in the intact virus. The polypeptide segment (region 22-36) following this buried portion as well as the epitope within the region 75-110 are exposed in the intact virus. These observations are consistent with the canonical β-barrel structure observed in certain other plant viruses.

Characterization of poly- and monoclonal antibodies to physalis mottle (tymo) virus

Polyclonal antibodies were raised against the Physalis mottle virus (PhMV) and its denatured coat protein (PhMV-P). Analysis of the reactivity of the polyclonal antibodies with tryptic peptides of PhMV-P in dot-blot assays revealed that many of the epitopes were common to intact virus and denatured coat protein. Five monoclonal antibodies to the intact virus were obtained using hybridoma technology. These monoclonal antibodies reacted well with the denatured coat protein. Epitope analysis suggested that probably these monoclonal antibodies recognize overlapping epitopes. This was substantiated by epitope mapping using the CNBr digest of PhMV-P in western blots. All the five monoclonals recognized the N-terminal 15 K fragment. Attempts to further delineate the specific region recognized by the monoclonals by various enzymatic cleavages resulted in the loss of reactivity in all the cases. The results indicate that these monoclonals probably recognize epitopes within the N-terminal 15 K fragment of the coat protein.

Inhibition of in Vitro Aminoacylation and Translation by RNA Reactive Antibodies

Antibodies were raised against guanosine-BSA, GMP-BSA and tRNA-mBSA conjugates separately in rabbits. Binding characteristics of these antibodies to various RNAs were studied using a sensitive avidin-biotin micro ELISA. These antibodies inhibited in vitro aminoacylation of tRNA in a dose dependent manner. This inhibition was reversed by the addition of the respective homologous haptens thereby showing the specificity of these antibodies. In vitro translation of endogenous mRNAs in rabbit reticulocyte lysate was also inhibited by these antibodies in a dose dependent manner.