C-reactive protein as a predictor of fetal and maternal infective morbidity and fetal mortality

The value of maternal C-reactive protein (CRP) levels as predictors of fetal and maternal infective morbidity and fetal mortality was assessed prospectively over a 6-month period in all cases of premature rupture of the fetal membranes or suspected premature labour. Statistical analysis of results showed that CRP at a level of 1.32 mg/dl is a sensitive marker of infective morbidity in mother and neonate. Furthermore, there was a significant association between raised CRP levels and low-birth-weight babies, suggesting that intra-uterine infection is a major cause of prematurity in the study population.     

Definition of the epitope recognized by the Plasmodium falciparum-reactive human monoclonal antibody 33G2.

The human monoclonal antibody 33G2 has earlier been shown to inhibit merozoite reinvasion of red blood cells in Plasmodium falciparum cultures in vitro and to inhibit cytoadherence of infected red blood cells to melanoma cells in vitro. 33G2 cross-reacts with a family of P. falciparum antigens, Ag332, Pf11.1 and Pf155/RESA, sharing a common feature of repeated sequences consisting of regularly spaced pairs of glutamic acid. Peptides corresponding to residues 2-19 of the known amino acid sequence of Ag332 have been shown earlier to have the highest inhibitory capacity of antibody binding to infected red blood cells. Using the PEPSCAN method, overlapping hepta-, hexa-, penta- and tetrapeptides corresponding to residues 1-19 of the known sequence of Ag332 were synthesized. Antibody fine specificity was examined by synthesizing an octapeptide (residues 1-8) and all possible single amino acid substitutions. The monoclonal antibody was shown to react with a linear 5-amino acid-long sequence corresponding to Ag332 residues 3-7: VTEEI. These amino acids were irreplaceable or only partially replaceable in the replacement set analysis. Furthermore, epitope analogs corresponding to sequences contained within the Pf11.1 repeats and overlapping heptapeptides corresponding to Pf155/RESA repeats were synthesized. Reactivity to epitope analogs and Pf155/RESA peptides provided information which may explain antibody cross-reactivity. The defined epitope of this monoclonal antibody is of interest as a potential B cell epitope for the development of a malaria subunit vaccine.     

Interaction of lectins with human T lymphocytes mitogenic properties,inhibitory effects,binding to the cell membrane and to isolated surface glycopeptides

The mode of interaction of twelve lectins with human T lymphocytes was investigated. In order to establish possible differences between mitogenic and nonmitogenic lectins, they were studied for their capacity to induce or inhibit DNA synthesis. Their interaction with intact T cells was studied by immunofluorescence and ⁵¹Cr release. Further, lectins conjugated to Sepharose were investigated with regard to their capacity to bind surface glycopeptides from T cell lysates. Operationally, the lectins could be divided into three groups: (a) mitogenic lectins; (b) lectins inhibitory for lymphocyte mitogenesis as induced by leucoagglutinin (La) from Phaseolus vulgaris; and (c) nonmitogenic lectins which were noninhibitory in this La system. Six lectins were nonmitogenic. For two or possibly three of these, lack of mitogenicity was due to complete or partial failure to bind to the lymphocytes. This explanation could not account for lack of mitogenicity of the other three nonmitogenic lectins. Only two of the lectins utilized inhibited La-induced mitogenesis. However, when the lectins were compared with regard to their capacity to bind surface glycopeptides from T cell lysates, important differences between mitogenic and nonmitogenic lectins were seen. As revealed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate and autoradiography, the mitogenic lectins bound a larger number of surface glycopeptides (15–20) than the nonmitogenic lectins (3–10). More importantly, five distinct glycopeptides (gp 135 K, 125 K, 105 K, 95 K and 43 K) were bound by all mitogenic lectins but not by the nonmitogenic lectins. It remains to be established whether these glycopeptides are present on the T cells which are susceptible to the mitogenic action of the lectins and whether it is the interaction of the lectins with one or several of them which triggers mitogenicity.     

Comparative study of pituitary and bacteria-derived human growth hormone by monoclonal antibodies

We have established hybridoma lines which secrete mouse monoclonal antibodies (Mabs) to human pituitary growth hormone, hGH. Using indirect competitive ELISA and indirect passive hemagglutination inhibition twelve different Mabs were characterized with regard to cross-reactivity with the hGH-related hormones, human chorionic somatomammotropin, hCS, and human prolactin, hPRL. The reactivity of these Mabs with pituitary hGH was compared to that with either bacterially-produced methionyl-hGH or to that of reduced and S-carboxymethylated hGH, which has an altered conformation. None of the Mabs reacted with hPRL. Four did not react with hCS whereas the others showed varying degree of cross-reactivity with hCS. All Mabs reacted more weakly with reduced and S-carboxymethylated hGH than with the native form of the hormone, which was not seen with conventional rabbit antisera to hGH. Thus in the case of hGH the Mabs are superior to conventional antisera in revealing small conformational differences. However the pituitary and bacterially-derived methionyl-hGH were indistinguishable as determined by the 12 Mabs.     

Immunological studies in ulcerative colitis. VI. Light microscopic studies with peroxidase conjugated antibodies

Cryostat sections of colon from germ-free rats were incubated with sera from patients with ulcerative colitis or healthy controls. With peroxidase-conjugated antibody from sheep to human immunoglobulin, a distinct staining of goblet cell surface was observed with the patients' sera but not with the controls. The staining compares well with that obtained by indirect immunofluorescence. It could easily be distinguished from staining due to endogenous peroxidase.     

Quantitative studies on phytohaemagglutinin-induced cytotoxicity by human lymphocytes against homologous cells in tissue culture

The cytotoxic effect of normal human blood lymphocytes on Chang cells in tissue culture was investigated. Cell damage was measured by release of ⁵¹Cr from pre-labelled tissue culture `target' cells. This method was sensitive and rendered highly reproducible results. Released ⁵¹Cr was not re-utilized.

About 25 per cent of the ⁵¹Cr was spontaneously released from labelled Chang cells when incubated for 24 hours at 37°. Lymphocytes at a lymphocyte/Chang cell ratio of 25:1 led to a slight increase of this release. When phytohaemagglutinin was also present, about 50–60 per cent of the isotope appeared in the medium. Under these conditions target cells were significantly damaged within 1 hour. At a lymphocyte/Chang cell ratio of only 1:1, weak cytotoxic effects were also noted after 24 hours of incubation. The results of dose—response experiments suggested that a considerable proportion of the lymphocytes participated in the reaction. Individual variation of the cytotoxic effect of lymphocytes from different donors suggested that it could be related to the degree of histoincompatibility between lymphocytes and Chang cells. Under the present conditions contaminating erythrocytes or granulocytes did not interfere with the cytotoxic action of the lymphocytes.

     

T cell reactivity of defined peptides from a major Plasmodium falciparum vaccine candidate: the Pf155/RESA antigen

Several immunodominant B-cell epitopes of the P. falciparum antigen blood stage Pf155/RESA, a major vaccine candidate antigen, are located in the molecular regions containing amino acid repeats. We started to map Pf155/RESA for T cell reactive epitopes. For this purpose, short synthetic peptides corresponding to the 3'- and 5' repeat regions of the molecule as well as to non-repeated sequences outside these regions were prepared. T cells from P. falciparum primed donors from two highly endemic areas of Africa were tested for their responsiveness to the peptides by thymidine incorporation and/or interferon gamma (IFN-gamma) release. There was a considerable variation in the response to the different peptides. However, the strongest and most frequent responses were seen with a few peptides from the 3'- and 5'-repeat regions. Thus, the immunodominant B cell epitope regions of Pf155/RESA, contain several T cell epitopes. Since the repeat regions are known to be conserved in different P. falciparum strains, the T cell epitopes reported here may be suitable constituents of a P. falciparum subunit vaccine.     

Studies on the specificity of anti-erythrocyte antibodies in the serum of patients with malaria

Sera from patients with Plasmodium falciparum, P. vivax or P. ovale malaria were selected according to their high levels of antibodies against human erythrocyte membranes as measured in a microELISA. The specificity of the anti-erythrocyte antibodies in these sera and two normal sera was investigated by means of an immunoblotting technique in combination with SDS-polyacrylamide gel electrophoresis. All the patients' sera as well as the control sera contained antibodies against several erythrocyte polypeptides. As compared with normal sera, most malaria sera showed elevated levels of antibodies against polypeptides of 80K, 70K, 40K and 28K molecular weights. Two sera reacted strongly against a polypeptide with an electrophoretic mobility similar to the alpha subunit of spectrin. One serum showed strong reaction and several other sera, including normal sera, showed weak reaction against a 45K molecular weight polypeptide corresponding to actin. No pervading differences were seen in the pattern of specificities of the anti-erythrocyte ghost antibodies between sera from patients with P. falciparum, P. vivax or P. ovale infections.