[African aspects of vaccination in prevention of purulent meningitis].
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Biomedical subjects
Publications and source records attributed to M Rey.
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Few data are available on the blood lymphocyte response to revaccination in man. The anamnestic response to tetanus toxoid challenge was evaluated by a variety of techniques during the first week after revaccination. Out of twenty subjects used, eight were evaluated before and 5 days after the injections (days 1--8). Analytical cell electrophoresis showed important variation in the B and two T lymphocyte populations. The B cell percentages, assessed by EAC-rosettes and electrophoretic mobility, were found to decrease by days 2 and 3, and return to former levels by day 8, when a rise in specific antibodies was detected. A similar response was found in the T1 population generally considered to be composed of low affinity E-rosette-forming cells. Conversely, a significant increase (50--100%) in circulating T2 lymphocytes (active rosette-forming cells) was found by days 2 and 3, followed by a rapid decrease of these 'differenciated' cells. The increase in the T2 lymphocytes appeared earlier in skin test positive subjects. These changes were correlated with E-rosettes, mitogen stimulation, peripheral leucocyte migration inhibition and transformation in the presence of the antigen. EA-IgG rosettes and ADCC varied similarly. These results may indicate a significant non-specific cell mobilization following revaccination.
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The risk of tetanus is universal, but it depends on numerous factors (socio-economic, environmental and biological) which combine to determine the force of infection. Tetanus is a murderous and costly disease. Its morbidity has greatly regressed in industrialized countries (less than 1 case per 100,000, involving mainly aged persons). On the contrary, developing countries are still severely affected (10 to 50 cases per 100,000, involving mainly neonates and children). Tetanus vaccine is one of the most effective, best tolerated and least expensive vaccines. Vaccination is the main weapon for starting disease control in developing countries, and the only way of eradicating tetanus in developed countries. Whatever the socio-economic level may be, some evaluations show that immunization cost is approximately equal to avoided treatment and seroprevention expenditures. The essential benefit of vaccination is the prevention of death, suffering and disability.
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Two commercialized anatoxins, titrating 30 Lf per dose and adsorbed on Ca phosphate and Al hydroxide respectively, were studied in comparison with an experimental anatoxin titrating 25 Lf per dose and adsorbed on Al phosphate, and with a placebo. 595 schoolchildren from Cameroun were randomly assigned to four groups and inoculated twice, with a year's interval between the two inoculations. Serological checks were carried out by double-blind trials using the passive hemagglutination (HA) method on days 7, 90, 365 and 395. HA titers rose substantially after three months and then fell during the 12th month. The HA method does not give a clear indication of the amount of protection obtained after only one inoculation, but this amount would seem to be small according to the results of neutralization tests carried out on samples. It is only after the second injection that protection is provided for most subjects. Results vary depending on the anatoxin and are not linked to the--benign--clinical reactions observed. This study confirms that if anatoxins with high antigenicity are to be used, two injections are necessary and sufficient to guarantee good immunity protection.
The authors report a case of bilharzia localised to one of the ureters in a case of double renal pelvis and ureter. The parasitic infection was identified only at the time of exploratory surgery (laboratory investigations and preoperative endoscopy negative). The "providential" double ureter made it possible to combine excision of the pathological ureter with a termino-lateral anastomosis between the lower renal pelvis and the ureter of the upper renal pelvis. The result remains very satisfactory with a follow-up of 13 months.
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The conditioned, passive hemagglutination method, which is simple, quick, economical and very sensitive, is suited for large-scale studies in which it is not possible to carry out the in vivo seroneutralization. However, our experience has confirmed that it has certain drawbacks and restrictions: (1) the technique must be applied very carefully and good laboratory training is required. The results obtained by this method vary according to several factors, especially the degree to which the antigen has been purified and its blood carriers, therefore these results are not always consistent; (2) the antibodies found were not a good indication of the degree of protection except at high titers. A study of correlations between HA titers and neutralizing (mice) titers carried out on the basis of 509 double titrations has demonstrated that, whereas they are satisfactory in clearly immune subjects, they show only mediocre results in subjects who are receptive or who are displaying a primary response: a wide range of variation has been observed as well as an optimalization of HA titers, perhaps because of IgM's. Therefore, the HA method, despite its usefulness, cannot provide precise evaluations for: --the amount of protection provided by an anti-tetanus vaccine, --the proportion of protected subjects in a certain group of people, --an injured person's anti-tetanus immunity. We should work to develop in vitro tests which are both sensitive and reliable in terms of the anti-tetanus protection threshold.
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