Sensibilidade tuberculínica pós-vacinal e sua irrelevância para a revacinação BCG

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Abstract

Revisão realizada com o objetivo de mostrar que a prática de revacinar com BCG, baseada na negatividade do teste tuberculínico pós-vacinal, é destituída de fundamentos científicos. São apresentados alguns fatos nos quais se baseia o teste tuberculínico padronizado, seguidos de comentários sobre o perfil tuberculínico de populações não vacinadas. Considerações sobre o perfil tuberculínico de populações vacinadas e suas variações no indivíduo e no grupo vacinado como um todo, conduzem ao questionamento sobre uma possível correspondência entre alergia pós-vacinal e resistência à tuberculose. Fatos de natureza epidemiológica e dados experimentais são arrolados, mostrando que a proteção conferida pela vacina não é proporcional ao grau de alergia induzida nos indivíduos; a esses argumentos se acrescenta a recente demonstração de que, embora tuberculino-negativas, crianças vacinadas podem apresentar intensa reatividade linfocitária ao PPD. Discute-se a utilização do teste tuberculínico na avaliação do processo de vacinação.

Translated abstract

This article demonstrates that BCG revaccination when tuberculin test results are used as the reason for the revaccination of people with doubtful reactions or no reactions at all should be considered outdated. To show this a brief exposition on tuberculin sensitivity and acquired resistance to tuberculosis and then the technical background of the tuberculin test are presented followed by comments concerning tuberculin profiles of general population groups. Individual variations in BCG - induced allergy raise questions about a possible correlation of post-vaccination allergy and resistance. Epidemiological data and experimental facts, however, demonstrate that the degree of protection given the individual is not proportional to the degree of tuberculin skin sensitivity induced by vaccination. Recent findings show that lymphocytes from BCG vaccinated children retain sensitivity to tuberculin years after vaccination and even when skin reactivity has disappeared. Finally, tuberculin testing for the evaluation of BCG vaccination is discussed.

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BCG and vole bacillus vaccines in the prevention of tuberculosis in adolescence and early adult life.

I Sutherland, Ronald Hart (1977)

The Medical Research Council's trial of BCG and vole bacillus vaccines in the prevention of tuberculosis in Great Britain has ended after 20 years' follow-up of the 54 239 participants, who were aged 14 to 15 years when the entered the trial in 1950-2. Participants who were tuberculin positive on entry were left unvaccinated; those who were tuberculin negative were allocated at random to an unvaccinated or to a vaccinated group. The protective efficacy of each of the two vaccines, among those initially tuberculin negative, was 84% during the first five years, and gradually decreased, averaging 77% for each vaccine over the whole period. The incidence of tuberculosis decreased substantially in all groups during the trial, however, and of the total of 610 cases of tuberculosis only 27 developed between 15 and 20 years. Thus we cannot make a reliable assessment of efficacy during this final period. The prevalence and incidence of tuberculosis in Great Britain have decreased radically since this trial began. The expected benefit from large-scale BCG-vaccination of children is now far less, and may decrease further if the incidence of tuberculosis continues to decline.

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THE INFLUENCE OF IMMUNOLOGICALLY COMMITTED LYMPHOID CELLS ON MACROPHAGE ACTIVITY IN VIVO

G. B. Mackaness (1969)

It has been shown that the immune response of mice to infection with L. monocytogenes gives rise to a population of immunologically committed lymphoid cells which have the capacity to confer protection and a proportionate level of delayed-type hypersensitivity upon normal recipients. The cells were most numerous in the spleen on the 6th or 7th day of infection, but persisted for at least 20 days. Further study revealed that the immune cells must be alive in order to confer protection, and free to multiply in the tissues of the recipient if they are to provide maximum resistance to a challenge infection. The antibacterial resistance conferred with immune lymphoid cells is not due to antibacterial antibody; it is mediated indirectly through the macrophages of the recipient. These become activated by a process which appears to depend upon some form of specific interaction between the immune lymphoid cells and the infecting organism. This was deduced from the finding that immune lymphoid cells from BCG-immunized donors, which were highly but nonspecifically resistant to Listeria, failed to protect normal recipients against a Listeria challenge unless the recipients were also injected with an eliciting dose of BCG. The peritoneal macrophages of animals so treated developed the morphology and microbicidal features of activated macrophages. It is inferred that acquired resistance depends upon the activation of host macrophages through a product resulting from specific interaction between sensitized lymphoid cells and the organism or or its antigenic products. Discussion is also made of the possibility that activation of macrophages could be dependent upon antigenic stimulation of macrophages sensitized by a cytophilic antibody.