Biomedical subjects
Publications and source records attributed to L Saarinen.
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The major outer membrane protein of Haemophilus influenzae type b (Hib) is porin (Mr 38,000, 341 amino acids). To identify antigenic determinants on Hib porin that might be exposed at the bacterial cell surface, seven mouse monoclonal anti-Hib porin antibodies were generated. The monoclonal antibodies were tested for their binding to intact cells by flow cytometry; all but one bound to the cell surface. Digestions of Hib porin with cyanogen bromide, hydroxylamine or trypsin generated fragments, the identities of which were confirmed by microsequencing of the amino termini. Following electrophoresis and immunoblotting of the fragments, the specificities of the monoclonal antibodies for their cognate sequences were determined. The porin gene ompP2 was expressed in the baculovirus expression vector system; the recombinant porin was recognized by all of the monoclonal antibodies. Deletions were created by omega mutagenesis of ompP2, generating proteins truncated after amino acids 139, 174, 182, and 264. These deletion proteins were tested for reactivities with the monoclonal antibodies, thereby establishing the boundaries of three antigenic determinants that were recognized by the monoclonals: domain (i), amino acids 104-139; domain (ii) amino acids 162-174; and domain (iii), amino acids 267-341. The biological activities of monoclonal antibodies that were representative of these three classes were tested for their bactericidal activity in complement-mediated lysis of whole cells. The monoclonal antibodies were also tested for their immunoprotective properties in the infant rat model of bacteraemia. Although the monoclonal antibodies were surface-binding, they were neither bactericidal nor protective.
Synthetic oligosaccharides derived from the capsular polysaccharide (PRP) of Haemophilus influenzae type b were conjugated to carrier proteins via a thioether linkage. Conjugates were made of trimeric and tetrameric ribose-ribitol-phosphate and tetanus toxoid or diphtheria toxin. All conjugates elicited anti-PRP antibody responses with an increasing immunoglobulin G/immunoglobulin M ratio in adult mice and monkeys. Trimer conjugates elicited lower anti-PRP antibody responses compared with tetramer conjugates. Adult monkeys responded equally well to the tetrameric oligosaccharide-tetanus toxoid conjugate as to the oligosaccharide-CRM197 conjugate (HbOC), which elicits protective levels of serum antibodies in human infants after two or three injections.
Serum antibody responses to four Haemophilus influenzae type b capsular polysaccharide-protein conjugate vaccines (PRP-D, HbOC, C7p, and PRP-T) were studied and compared in 175 infants, 85 adults and 140 2-year-old children. Antibodies to the H influenzae type b polysaccharide vaccines were determined with a Farr-type radioimmunoassay. The infants received two doses of vaccine at the ages of 4 and 6 months. After the first dose of vaccine, the geometric mean antibody concentration measured at the age of 6 months was 0.09 to 0.10 mg/L, only marginally higher than that measured before immunization in all infants who had received PRP-D, HbOC, or C7p but increased to 0.82 mg/L in those who had received PRP-T. One month after the second dose, the geometric mean antibody concentration was increased in all vaccine groups. No significant differences were noted between recipients of HbOC, C7p, or PRP-T (geometric mean antibody concentrations, 4.32, 3.10, and 6.10 mg/L, respectively), whereas the PRP-D recipients had a significantly lower geometric mean antibody concentration (0.63 mg/L). In contrast, PRP-D, HbOC, C7p, and PRP-T were all highly immunogenic in adults, with no differences noted among them. The 2-year-old children also responded to one dose of these vaccines with a high antibody concentration.
The effects of occupational exposure to chlorodifluoromethane (FC 22) and dichlorodifluoromethane (FC 12) on cardiac rhythm were examined. The subjects were six men who repaired refrigerators (age 31-56, mean 46 years) and a control group of six plumbers (age 29-54, mean 45 years). Ambulatory electrocardiograms (ECG) were recorded for 24 hours on the day of exposure and on a control day. The ECG tapes were automatically analysed with a Reynolds pathfinder 3 apparatus and all aberrant complexes recorded by the machine were checked. One person read all the tapes without knowing whether or not they were recorded during exposure. The number of ventricular ectopic beats were compared between the day of exposure and the control day and with the tape of the control. In addition, the number of ventricular ectopic beats during exposure was compared with the number occurring during the rest of the day. The concentrations of fluorocarbons were measured in four instances. High peak concentrations of fluorocarbons (1300-10,000 cm3/m3) were measured during refrigerator repair work. No clear connection between fluorocarbons and cardiac arrhythmia was found, although one subject had several ventricular ectopic beats which may have been connected with exposure.
The serum antibody response to Haemophilus influenzae type b capsular polysaccharide or its protein conjugate vaccine (PRP and PRP-D, respectively) was studied in 28 children initially immunized at the age of 24 mo with either vaccine and in 10 children immunized for the third time with PRP-D at the age of 18 mo. The methods used were isotype-resolving enzyme immunoassay, Farr-type radioimmunoassay, and the in vitro bactericidal activity (BCA) test. Immunization with PRP evoked a higher proportion of IgA antibodies than did either the first or third dose of PRP-D, whereas the latter vaccine evoked a somewhat higher IgG response, but the differences were not statistically significant. In all groups the IgG antibody responses were predominantly IgG1, with the mean proportions being 82.2%, 84.2%, and 65.9% in the PRP, first-dose PRP-D, and third-dose PRP-D groups, respectively. Postimmunization antibodies were functionally active in the BCA test.
In Finland occupational asthma caused by protein allergens and reactive chemicals present in the air of work environments is increasing. This communication describes provocative challenge tests and methods for measuring exposure under simulated work conditions. The importance of lung function measurements during non-exposure and placebo periods is stressed. Especially late reactions are difficult to assess because of the great circadian variation in the lung function parameters of asthmatics. For a positive challenge test, a decrease in peak flow values of at least 15% and a clear deviation from normal circadian variation and placebo periods is required. The allergens of vegetable or animal origin primarily affect patients with an atopic constitution. Chemical allergens seem to attack all exposed workers in the same way. The report lists the occupations with risk for asthma and refers to the population at risk; bakers seem to be the group with the most risk. The importance of early diagnosis, removal of the worker from exposure and improvement of the hygienic aspects of the work environment are stressed.
Home-made but commercially available alcoholic beverages were collected in Dar es Salaam, Tanzania and analysed for their congener alcohol, additive, aflatoxin and heavy metal contents. Ethanol concentrations of the 15 brewed samples ranged from 2.2 to 8.5% w/v whilst the 2 distilled samples contained ethanol 24.2 and 29.3% w/v. Aflatoxin B1 was found in 9 brewed beverages, suggesting the use of contaminated grain or fruit for their production. The amount of zinc in 4 samples was double the World Health Organization recommended maximum for drinking water (5 mg/litre). One brewed beverage contained toxic amount of manganese (12.8 mg/litre). Both distilled spirits were rich in fusel alcohols and one was fortified by caffeine. The results suggested that impurities and contaminants possibly associated with severe health risks, including carcinogens, are often found in traditional alcoholic beverages. Continuous daily drinking of these beverages is certain to increase health risks. Contaminated grain or fruit rejected from foodstuff production should not be used for the production of alcoholic beverages.