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Biomedical subjects

R S Vallishayee

Publications and source records attributed to R S Vallishayee.

At least 19 recordsLinked to original sources
PubMed1992

The pattern of mycobacterial antigen recognition in sera from Mantoux-negative individuals is essentially unaffected by bacille Calmette-Guérin (BCG) vaccination in either south India or London.

Paired sera were obtained before and 8 weeks after routine BCG vaccination from 20 PPD-S Mantoux-negative individuals who were living adjacent to the Chingleput BCG vaccine trial area in Tamil Nadu and from seven Mantoux-negative school-children in London, UK. Most subjects became Mantoux-positive after vaccination. In ELISA tests against soluble extracts of BCG or Mycobacterium tuberculosis H37Rv or against PPD-S, pre-vaccination antibody titres of South Indian subjects were about twice those of British subjects but there was no increase in titre of antibodies after vaccination of either population. Western blotting showed that even before vaccination, and even in British subjects, antibodies were present that recognized numerous antigenic components in extracts of BCG and M. tuberculosis. There was no consistent difference between band patterns with South Indian and British subjects and any effect of vaccination on the patterns was minimal.

Adolescent↗
PubMed1992

Sensitization potential and reactogenicity of BCG with and without various doses of killed Mycobacterium leprae.

A study was conducted in 997 individuals in two villages in south India to find the acceptability and sensitizing effect of the antileprosy combination vaccine of BCG plus killed Mycobacterium leprae (KML). Three preparations of the combination, BCG 0.1 mg + 6 x 10(8) KML (I), BCG 0.1 mg + 5 x 10(7) KML (II), and BCG 0.1 mg + 5 x 10(6) KML (III), along with BCG 0.1 mg (IV), and normal saline (V), were used in the study. Each individual received one of the above five preparations by random allocation. They were also tested with Rees' M. leprae soluble skin-test antigen (MLSA) and lepromin-A, both at intake and 12 weeks after vaccination. Reactions to Rees' MLSA were measured after 48 hr; those to lepromin-A after 48 hr and 3 weeks. The character and size of the local response at the vaccination site were recorded at 3, 8, 12, 15, and 27 weeks after vaccination. The mean sizes of postvaccination sensitization to both Rees' MLSA and lepromin-A in the vaccine groups were significantly larger than those in the normal saline group, clearly demonstrating the ability of the vaccines to induce sensitization as measured by responses to the two skin tests. The sensitizing effect was the highest following vaccination with vaccine I. It was not significantly different for vaccines II, III, and IV, although, generally, a dose-response effect was observed. The sensitizing effect attributable to the vaccine was more clearly seen in children than in adults. The above conclusions were the same irrespective of which results were considered, reactions to Rees' MLSA or Fernandez or Mitsuda reactions to lepromin-A. A significant finding of the study was that at intake the Mitsuda reactions provided a measure of sensitizing effect due to vaccine. The healing of vaccination lesions was uneventful. In more than 90% of vaccinated individuals, the lesions had healed by the 12th week in vaccine groups II, III, and IV, and by the 15th week in vaccine group I. The results showed that vaccination with BCG or combination vaccines was equally safe in individuals with or without previous BCG scars. Thirteen persons, aged 10 years or older, developed suppurative lymphadenitis around the 8th week (7 in vaccine group I, 3 each in vaccine groups II and III). However, healing was prompt after drainage in these individuals.

Adolescent↗
PubMed1992

Effect of skin test with M. leprae soluble antigen on reaction to a subsequent test with the same antigen.

Soluble skin-test antigens (STA), produced from armadillo-derived Mycobacterium leprae by Drs. Rees and Convit, were expected to meet the long-felt need of a test for leprosy infection and also to serve as tests for measuring postvaccination sensitization induced by vaccine preparations against leprosy. The present paper reports results from two studies examining the influence, if any, of skin testing with Rees' STA on reaction to a subsequent test with the same antigen. In the first study, 2168 persons from households of leprosy patients and from neighboring households were skin tested with Rees' STA twice at an interval of 6 months. In the second study, 1700 persons, free from leprosy, received either Rees' STA or normal saline by random allocation. A random subset of 850 persons was tested with Rees' STA after 3 months. The remaining 850 persons were tested with Rees' STA after 6 months. In addition, 242 leprosy patients were given Rees' STA or normal saline by random allocation, and all of these patients were tested with Rees' STA after 6 months. The results of the two studies showed that among persons reacting with a small size of reaction to Rees' STA, the size of the reaction to the repeat test was significantly larger. However, from the results of the second study, which included a control group, it was clearly seen that the quantum of boosting or sensitizing effect of the first test as well as that of new sensitization was small over a period of 3-6 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Prevalence study of tuberculous infection over fifteen years, in a rural population in Chingleput district (south India).

As in the earlier BCG trial against tuberculosis conducted in Chingleput district in south India (in 1969), the entire study population was tuberculin tested (Survey I), a study was undertaken subsequently to see whether in this population there was any change in the tuberculosis situation in terms of prevalence of infection in children. For this purpose, in two of the panchayat unions, in a random sample of panchayats, tuberculin testing was repeated twice at an interval of 10 yr (Survey II) and 15 yr (Survey III) after the initial testing in children aged 1-9 yr. High coverages were obtained for tuberculin testing and reading. Data from 8,703 and 9,709 children at Surveys I and II respectively was used for comparing the prevalence of infection over a period of 10 yr and from 4,808, 4,965 and 4,889 children at Surveys I, II and III respectively for comparing the prevalence of infection over a period of 15 yr. The results showed that although the prevalence of infection varied in the two panchayat unions, within each panchayat union it did not differ significantly at the three surveys. The overall prevalence of infection at the three surveys was 9.0, 10.2 and 9.1 per cent respectively. The average annual risk of tuberculous infection was estimated to be 1.7, 1.9 and 1.7 per cent at the three surveys respectively. Thus, the results clearly showed that, over a period of 15 yr, there was no change in the tuberculosis situation, in terms of prevalence of infection, in the study population.

Adolescent↗
PubMed1990

Experiences with Mycobacterium leprae soluble antigens in a leprosy endemic population.

Rees and Convit antigens prepared from armadillo-derived Mycobacterium leprae were used for skin testing in two leprosy endemic villages to understand their use in the epidemiology of leprosy. In all, 2602 individuals comprising 202 patients with leprosy detected in a prevalence survey, 476 household contacts and 1924 persons residing in non-case households were tested with two antigens. There was a strong and positive correlation (r = 0.85) between reactions to the Rees and Convit antigens. The distribution of reactions was bimodal and considering reactions of 12 mm or more as 'positive', the positivity rate steeply increased with the increase in age. However, the distributions of reactions to these antigens in patients with leprosy, their household contacts and persons living in non-case households were very similar. These results indicate that Rees and Convit antigens are not useful in the identification of M. leprae infection or in the confirmation of leprosy diagnosis in a leprosy endemic population with a high prevalence of nonspecific sensitivity.

Adolescent↗
PubMed1987

Virulence for guinea pigs of tubercle bacilli isolated from the sputum of participants in the BCG trial, Chingleput District, South India.

This study, conducted in Madras, India and in Madison, Wisconsin, USA, was concerned with the virulence of isolates of Mycobacterium tuberculosis obtained from the sputum of individuals living in the Chingleput district of south India. The following results were obtained. 1. The findings of Mitchison with respect to the predominance of low virulence for guinea pigs among isolates from persons living Madras, were confirmed on isolates from the sputum of residents of the Chingleput district. 2. A high correlation was found between the log10 number of tubercle bacilli recovered from the spleen of guinea pigs infected intramuscularly with 1.0 mg of tubercle bacilli and the root index of virulence. 3. A high correlation was found between the log10 number of tubercle bacilli recovered from the spleen of guinea pigs infected intramuscularly with 1.0 mg of tubercle bacilli and the number recovered from the spleen of guinea pigs infected by the respiratory route with 5-10 tubercle bacilli. 4. Relatively low correlations were found between RIV and the susceptibility of isolates to thiophene-2 carboxylic acid hydrazide or to hydrogen peroxide.

Animals↗
PubMed1981

Post-vaccination tuberculin sensitivity for assessing BCG vaccination in areas with high prevalence of non-specific sensitivity.

The relationship of non-specific sensitivity to post-vaccination tuberculin sensitivity has been the subject of controversy. This relationship has an important bearing on the common practice of using post-vaccination tuberculin sensitivity for assessing BCG vaccination in areas with a high prevalence of non-specific sensitivity. If post-vaccination tuberculin sensitivity is found to be dependent on the amount of already existing, naturally acquired, non-specific sensitivity it could not be considered a reliable measure of the success of BCG vaccination. In a recent BCG trial in India a large number of persons were tested with PPD-S and PPD-B and also vaccinated with BCG vaccine or injected with placebo, by random allocation. Mutually exclusive random samples of the study population were retested with PPD-S at 2 1/2 months, 2 1/2 years and 4 years after vaccination. At each post-vaccination test the tuberculin sensitivity obtained among the placebo-injected controls provided a measure of the tuberculin sensitivity due to non-specific sensitivity that would have been present in the absence of BCG vaccination. The difference between the mean size of reactions to the post-vaccination test among the vaccinated and among the unvaccinated controls provided a measure of tuberculin sensitivity that was wholly due to BCG vaccination. Thus it was possible to separate and study the two components of post-vaccination tuberculin sensitivity. The results of the study indicate that post-vaccination tuberculin sensitivity can be used to assess BCG vaccination in areas with a high prevalence of non-specific sensitivity, provided the assessment is done in younger age groups and based on post-vaccination tuberculin sensitivity as measured at 2-3 months after vaccination and not later.

Adolescent↗