Effects of antimalarial drugs on human natural killer cell activity.

Separation of null cell fraction from the other cellular components of human peripheral blood obtained from normal healthy individuals was effected through the Ficoll-Hypaque density gradient centrifugation, carbonyl iron phagocytosis-magnet application, E-rosette forming and binding to 19S-EAC respectively. The null cells were used as effector cells in the cytotoxic assay. The spontaneous cell-mediated cytotoxicity assay was employed and the highly NK-sensitive K562 labelled with Na251 CrO4 were used as targets. The null cell fraction was divided into several portions to allow for normal control, diluent control and tests. The test portions were those exposed to the various antimalarial drugs employed. It was observed that the T cell, B cells and null cell fractions accounted for 72%, 18% and 10% of the total lymphocyte population respectively. The mean cytotoxicity generated by the natural killer subset was 63%. The antimalarial drugs/drug combination used were chloroquine, quinine, pyrimethamine and sulfadoxine/pyrimethamine combination. Concentrations used were their respective minimal inhibitory concentration (MIC) and corresponding 5 X MIC. The inhibitory effects on natural killer cell activity of these drugs were observed. The possible reasons for these observations are discussed.

Soluble haemagglutinin of classical vibrios: isolation and protection against cholera by its antibodies.

Soluble haemagglutinin was isolated from a late culture supernatant of classical Vibrio cholerae grown in casein-peptone broth with aeration by saturated ammonium sulphate precipitation in the cold, followed by gel filtration, electrophoresis, ether extraction and electrophoresis respectively. The antigen was found to consist of three protein fractions with different electrophoretic mobilities. Antibodies to these fractions afforded low but significant protection against oral challenges with homologous classical V. cholerae in the infant mouse cholera model.

Protection afforded by anti-hemolysin against V. cholerae El Tor infection in experimental cholera.

Specific antisera to V. cholerae El Tor hemolysin were prepared. The sera exhibited the following characteristics: formed a single precipitin band in immunoelectrophoresis against the crude preparation of hemolysin, had no passive hemagglutinating antibodies against V. cholerae LPS sensitized cells, possessed neutralizing property to the homologous hemolysin, and afforded some small degree of protection to oral challenge of V. cholerae El Tor in experimental animals.

Assessment of antibody responses and protective immunity in cholera vaccinated subjects.

Cross-reactive antibody responses were assessed in volunteers vaccinated with classical Inaba and Ogawa cholera vaccines. The El Tor, Ogawa vibrios, the most often biotype, and serotype found to be the causative agent of cholera in Thailand, or their product were used throughout the in vitro and in vivo tests. The test involved were the passive hemagglutination test, vibriocidal tests and the mouse protection test. Classes of specific immunoglobulins produced in the volunteers were determined using anti-immunoglobulin enhancement of hemagglutination. It was found that the levels of hemagglutinating and vibriocidal antibodies reached their peaks on day 7 after the vaccination and were statistically constant for 3 months. Significant decrease was observed thereafter. The mouse protective antibody titer was highest at 1 month after the vaccination then declined significantly at the 6th month. Classes of specific immunoglobulins were found to be either IgM or IgG alone or mixture of both.

The study of intestinal immunity against V. cholerae: purification of V. cholerae El Tor haemagglutinin and the protective role of its antibody in experimental cholera.

V. cholerae El Tor Ogawa strain O17SR grown on trypticase soy agar were extracted with 0.05 M cyclohexylamino propane sulfonic acid (CAPS) pH 9.5 at 37 degrees C for 1 hour. The bacteria were then removed by centrifugation and millipore filtration. The filtered fluid, after being dialysed against many changes of cold distilled water, was concentrated and passed through Sephadex G200 column. Three protein profiles were eluted out with 0.05 M Tris buffer pH 8.6. The haemagglutinin and the bacterial lipopolysaccharide (LPS) were confined to the first profile. They were subsequently separated by agarose gel electrophoresis. The haemagglutinin was found to be more anodic than the LPS. After homogenization of the gel strips containing the haemagglutinin followed by centrifugation at 9,000 g pure haemagglutinin was obtained in the supernatant. Rabbit aniserum against pure haemagglutinin contained protective antibodies against V. cholerae infection in the baby mouse model. Specific antibodies prepared from this antiserum was as protective as the antibodies directed against whole V. cholerae and heat stable somatic antigens of V. cholerae upon the same weight unit.