T cell function in children with acute lymphoblastic leukaemia.

Modern intensive chemotherapy has dramatically improved the prognosis of acute lymphoblastic leukaemia (ALL) in children. However, once remission has been established, quality of life and even survival may be threatened by exacerbation of viral infections in the prolonged period of continuation therapy necessary to prevent relapse. Often the viruses involved in the most severe infections are from the herpesvirus and paramyxovirus groups, suggesting that patients suffer from a defect in the cellular immunity thought essential to control such cell-associated infections. This may result from a T cell defect and, in this study, T cell responsiveness of patients under therapy for leukaemia has been investigated. In vitro proliferative responses of peripheral blood leucocytes (PBL) to the T cell mitogen phytohaemagglutinin (PHA) were impaired in children with ALL before treatment and in the induction of remission. Impairment was attributable to reduced T cell numbers, the presence of inhibitors in the patient's serum and direct damage to lymphocytes. On achieving remission, proliferative responses to PHA of both CD4+ and CD8+ T cell subsets quickly returned to normal levels with the switch to continuation chemotherapy. Proliferative responses to Herpes simplex virus antigens were also apparently normal in the majority of patients tested in remission. Further investigations, however, have suggested a persisting defect in CD8+ lymphocyte function. Gamma interferon secretion by PHA-stimulated PBLs was severely reduced for children with ALL in remission when compared with control children of similar age. Further, cytotoxic T lymphocyte responses to allogeneic cells could only be induced in PBL isolated from two of 13 children in remission from ALL whilst all control children of similar age and adults produced anti-allogeneic responses.

Production of type 1 fimbriae by Escherichia coli HB101.

Escherichia coli HB101 is frequently used as a host in the cloning of bacterial virulence genes because of its reported lack of virulence determinants such as fimbriae, adhesins and haemagglutinins. However, passage of HB101 in standing broth culture rapidly induced the production of fimbriae which mediated adhesion to HEp-2 cells and mannose-sensitive haemagglutination of human and guinea-pig erythrocytes. Fimbrial serology, morphology and pilin molecular mass of 18 kDa were consistent with those of type 1 fimbriae.

Characterisation of the urease from Helicobacter pylori and comparison with the ureases from related spiral gastric bacteria.

The urease enzyme of Helicobacter pylori was partially purified from whole cell extracts and found to have a molecular weight of 484 +/- 12 kDa. Ten monoclonal antibodies (mAbs) were produced against four different epitopes of the native enzyme. These mAbs also recognised the ureases of H. pylori-like organisms isolated from monkeys and pigs and the H. mustelae urease from ferrets. The urease enzymes of each of these organisms were found to be of the same molecular weight. The urease enzyme of H. pylori consisted of two subunits of 68.2 and 31.3 kDa.

Production and characterization of monoclonal antibodies to Aeromonas sobria surface antigens.

A panel of eight murine monoclonal antibodies (Mabs) was raised against the surface antigens of Aeromonas sobria isolated from a patient with diarrhoea. Antibodies to the LPS core and O-antigen and to protein antigens were generated. Three Mabs of the IgM isotype against either protein or LPS agglutinated 34/75 Aeromonas isolates from clinical and environmental sources. Similar numbers of A. hydrophila, A. sobria and A. caviae isolates were agglutinated. The Mabs were screened for their ability to inhibit A. sobria adhesion to HEp-2 cells, and haemagglutination (HA). Two Mabs directed against conformationally dependent epitopes on a 43-kDa protein blocked both functions. Of the anti-LPS Mabs one blocked adhesion only, and another blocked HA but not adhesion. Immunoprecipitation studies suggested that LPS-protein complexes may be involved in these potential virulence functions of A. sobria.

Mammary immunity in mothers of infants with respiratory syncytial virus infection.

Seven of 230 breast fed infants followed prospectively from birth through their first winter contracted RS virus infections. The colostral from five of the mothers of these infants contained antiviral IgA antibodies. In each case antibody levels were above the mean for a group of 36 mothers whose infants were age matched to infected infants but for whom there was no evidence of RS virus infection in their first winter. Four colostral samples from mothers of infected infants also contained antiviral IgG antibody. Colostral lymphocyte reactivity to RS virus antigen was tested in three mothers of infected infants and two showed significant proliferation. There was, therefore, no evidence that mothers of infected infants lacked mammary immunity to the virus. Maternal mammary IgA and IgG responses following diagnosis of RS virus infection in the infant were followed for the seven cases identified prospectively and for a further 23 infants admitted to hospital with RS virus infections of varying severity. There was no evidence that the mothers of more severely affected infants were deficient in IgA or IgG milk antibody.

Seasonal variations in maternal serum and mammary immunity to RS virus.

We have recorded the systemic and mammary/mucosal immune responses of women following natural infection with RS virus during the second and third trimesters of pregnancy. Anti-RS virus IgG antibody levels in the sera of women collected in the first trimester of pregnancy showed a bimodal distribution with high and low antibody groups. Antibody levels increased after exposure to the winter RS virus epidemic in the second trimester of pregnancy, probably as a result of infection but only for women in the low antibody group. Despite the increases, antibody levels for these women remained well below those of the high antibody group. There was no rise in mean antibody levels after exposure in the third trimester, even among women with low antibody, suggesting a degree of immunosuppression in late pregnancy. There was no evidence that infection during pregnancy was associated with adverse consequences for the infant. Exposure to RS virus in the first two trimesters, but not the third, was associated with high colostral IgA antibody levels that were maintained in the milk throughout the first 7 weeks of lactation. There was a significant correlation between colostral and maternal nasal IgA antibody levels at delivery. Levels of blood or colostral lymphocyte transformation responses at delivery were unaffected by exposure to RS virus in pregnancy. These observations upon natural infection suggest that vaccination during pregnancy is likely to achieve only marginal effects upon serum antibody levels but boost maternal mammary/mucosal immunity.

An enzyme-linked immunosorbent assay (ELISA) for IgG and IgA antibodies to respiratory syncytial virus in low dilutions of secretions of human serum and secretions.

An enzyme-linked immunosorbent assay (ELISA) has been developed for titration of IgG and IgA antibodies to respiratory syncytial (RS) virus in low dilutions of human serum, colostrum, and nasopharyngeal secretions. Previously the sensitivity of RS virus ELISA on such specimens has been limited by nonspecific absorption of antibody, particularly IgA, to crude antigen preparations. For IgG antibody estimation in infant sera, this unwanted binding was reduced to workable levels by increasing the serum, salt, and detergent concentration of the diluent. Residual nonspecific binding of IgA in colostra appeared mainly due to antigen lipids or to lipoproteins. This was markedly reduced by partitioning Triton X-100-treated infected cell lysate antigens in Arklone. Using the modified ELISA technique for anti-RS virus IgA, good correlations were found with unfixed cell membrane immunofluorescence (MIF) for colostra (r = 0.81, P less than 0.001) and nasal secretions from adult volunteers. In several samples nonspecific absorption of antibody precluded MIF assay, but did not affect the ELISA. Although there was an overall correlation between ELISA for anti-RS IgG antibody in sera, the complement fixation test (r = 0.75, P less than 0.001), and MIF test (r = 0.82, P less than 0.001), the sensitivity of ELISA for antibody responses in convalescent sera of infants from 3 months to 2 years was poor. Conversely, the sensitivity of ELISA for antibody in the sera of older children and for transplacentally acquired antibody in very young infants was higher than that for the other two tests. ELISA was thus less reliable than either CF or MIF for detecting antibody rises in paired infant sera, particularly where maternally acquired antibody remained in the acute serum. The reasons for this apparent disparity are discussed.

Comparison of a microneutralisation test with ELISA and precipitin tests for detection of antibodies to infectious bronchitis virus in chickens.

A microneutralisation test for infectious bronchitis virus using virus antigens available in Australia, cell culture medium containing low concentrations of serum and an elevated incubation temperature is described. The technique was economical on reagents and of comparable sensitivity to the enzyme-linked immunosorbent assay (ELISA). The value of the microneutralisation, ELISA and precipitin tests in assessing the serological response of a flock of commercial chickens to vaccine and natural virus challenge was determined.

Enzyme-linked immunosorbent assay for the detection of antibodies to infectious bronchitis virus.

An enzyme-linked immunosorbent assay (ELISA) for antibodies to avian infectious bronchitis (IB) virus is described. The immune response of chickens following vaccination with IB virus was monitored using this test, and the titers were compared with those obtained by serum neutralization. The ELISA appears to be suitable for IB serology.