The effect of exposure to ozone and nitrogen dioxide on the airway response of atopic asthmatics to inhaled allergen: dose- and time-dependent effects.

Eleven mild atopic asthmatic patients were exposed for 6 h, in randomized order, to air, 100 ppb O3, 200 ppb NO2, and 100 ppb O3 + 200 ppb NO2, followed immediately by bronchial allergen challenge. Subsequently 10 of these patients were exposed for 3 h to air, 200 ppb O3, 400 ppb NO2, and 200 ppb O3 + 400 ppb NO2, followed immediately by bronchial allergen challenge. All exposures were carried out in an environmental chamber, with intermittent moderate exercise, and a minimal interval of 2 wk. Exposure for 6 h to 100 ppb O3, 200 ppb NO2, and 100 ppb O3 + 200 ppb NO2 did not lead to any significant increase in the airway response of these individuals to inhaled allergen, when compared with exposure for 6 h to air. In contrast, exposure for 3 h to 200 ppb O3, 400 ppb NO2, and 200 ppb O3 + 400 ppb NO2 significantly decreased the dose of allergen (in log cumulative breath units [CBU]) required to decrease FEV1 by 20% (allergen PD20FEV1), compared with exposure to air (geometric mean CBU: 3.0 for air versus 2.66 for O3 [p = 0.002]; 2.78 for NO2 [p = 0. 018]; 2.65 for O3 + NO2 [p = 0.002]). These results suggest that the pollutant-induced changes in airway response of mild atopic asthmatics to allergen may be dependent on a threshold concentration rather than the total amount of pollutant inhaled over a period of time.

A single-radial haemolysis technique for measurement of antibody to influenza virus neuraminidase in equine sera.

A modified single-radial-haemolysis (SRH) test for measurement of antibody to influenza virus neuraminidase (NA) is described. The test requires treatment of sheep erythrocytes with butanol to increase sensitivity. In comparative assays, SRH was found to be more sensitive than the conventional neuraminidase-inhibition test. The SRH test was reproducible, specifically measured antibody to influenza NA and was easy to use. SRH antibody responses in ponies vaccinated with bivalent equine influenza vaccine were shown to be vaccine dose-related but were lower in magnitude and shorter in duration than comparable anti-haemagglutinin responses.

Responses of volunteers to inactivated influenza virus vaccines.

Three different types of bivalent influenza virus vaccine, a whole virus, an aqueous-surface-antigen vaccine and an adsorbed-surface-antigen vaccine were tested at three dosage levels in volunteers primed with respect to only one of the haemagglutinin antigens present in the vaccines. The local and systemic reactions to all three vaccine types were mild in nature and, following first immunization, the aqueous-surface-antigen vaccine was the least reactogenic. The serum haemagglutination-inhibiting antibody response to the A/Victoria/75 component of the vaccines to which the volunteer population was primed, was greatest following immunization with the aqueous-surface-antigen vaccine; the greatest antibody response to the A/New Jersey/76 component of the vaccines was observed following immunization with whole virus vaccine.

Standardization of assays of neuraminidase and its antibody.

The effect of various factors on the reproducibility of neuraminidase and NI antibody assays has been investigated. These factors include the substrate, strain of virus, nature of virus, i.e. whole, subunit or recombinant, temperature and pH. In assaying antibody levels the challenge virus should be standardized by a method other than optical density. It is recommended that a collaborative study should be set up to establish an international standard for neuraminidase and that this should incorporate a comparison of different methods.

Neuraminidase assay of influenza vaccines.

At present influenza vaccines are standardized on their haemagglutinin content only. Recently it has been shown that both neuraminidase and haemagglutinin antibodies are important in providing protection against the influenza virus. We have, therefore, developed an automated neuraminidase assay, based on the enzymic method of Kendal, but modified to minimise the interference by sucrose. A neuraminidase standard has been established and samples assayed against the standard have a coefficient of variation of plus or minus 6.8 percent. The assay has been adapted to measure the neuraminidase antibody level in serum. The neuraminidase to haemagglutinin ratio has been determined for various influenza strains. Both neuraminidase and haemagglutinin titres are being compared with results obtained by the single radial diffusion method.