VACCINATION AGAINST MYCOBACTERIUM TUBERCULOSIS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Tuberculosis is an international public health problem of enormous magnitude and remains the number one cause of death from an infectious disease world-wide. Tuberculosis is primarily a respiratory disease, and Mycobacterium tuberculosis (M.tb), the bacteria which causes tuberculosis, is spread via the inhalation of aerosolized droplets. We propose to utilize the technique of bronchoscopic segmental antigen challenge to elicit pulmonary immune responses to protein antigens of M.tb. This technique involves wedging the bronchoscope into specific segmental bronchi to locally instill diluted antigens. After allowing sufficient time for an immune response to develop, repeat bronchoscopy is performed with lavage of antigen-challenged and control lung segments. We will utilize the standard skin test reagent tuberculin (also known as purified protein derivative of M.tb, or PPD) as the antigen. We hypothesize that a protective recall response to antigens of M.tb can be elicited in individuals who are PPD-positive because of previous aerosol exposure to M.tb, and that this response is both quantitatively and qualitatively different from that of non-exposed individuals who have been vaccinated with BCG. We will investigate this hypothesis using the following specific aims: 1) To determine whether M.tb-specific lymphocytes can be recruited to the lung by segmental pulmonary challenge with purified protein derivative of M.tb; 2) To characterize the cellular infiltrate into alveolar segments in response to PPD challenge in terms of cell type, cytokine production, cytotoxic capacity, and ability to mediate killing of intracellular M.tb with human mononuclear phagocytes; 3) To compare the local pulmonary recall response to segmental PPD challenge in individuals with respiratory exposure to M.tb and in unexposed BCG-vaccinated subjects. Our human studies will consist of segmental pulmonary challenge of PPD-positive subjects with a history of clear exposure to M.tb or of BCG vaccination. Design of antigen challenge is adapted from studies of asthmatic subjects. Subjects will be nonsmokers age 18-50 who have no history of asthma or other chronic respiratory disease. Individuals with a history of PPD skin test response greater than 30 mm of induration, with a history of local ulceration in response to PPD testing, or with a history of systemic symptoms (such as fever, chills, and myalgias) in response to skin testing will be excluded from the study. We will perform an initial bronchoscopy to instill PPD, and a repeat procedure 48 hours later. In the initial bronchoscopy, PPD diluted in warmed sterile saline will be instilled into the lingular bronchus of the left lung, and the same volume of saline alone will be instilled into the right middle lobe bronchus. No bronchoalveolar lavage will be performed. The second bronchoscopy, performed 48 hours after the PPD challenge, will consist of the performance of bronchoalveolar lavage of both the challenge and control segments. In some studies, blood samples will also be obtained to allow for determination of the specificity of the pulmonary immune response elicited PPD by comparison to responses of unsorted blood lymphocytes. Initial studies will be aimed at determining the minimal dose of PPD needed to induce influx of lymphocytes into the challenged bronchial segment.