RESUMO
Pulmonary tuberculosis (TB) remains to be a major global health problem despite many decades of parenteral use of Bacillus Calmette-Guérin (BCG) vaccine. Developing safe and effective respiratory mucosal TB vaccines represents a unique challenge. Over the past decade or so, the human serotype 5 adenovirus (AdHu5)-based TB vaccine has emerged as one of the most promising candidates based on a plethora of preclinical and early clinical studies. However, anti-AdHu5 immunity widely present in the lung of humans poses a serious gap and limitation to its real-world applications. In this study we have developed a novel chimpanzee adenovirus 68 (AdCh68)-vectored TB vaccine amenable to the respiratory route of vaccination. We have evaluated AdCh68-based TB vaccine for its safety, T-cell immunogenicity, and protective efficacy in relevant animal models of human pulmonary TB with or without parenteral BCG priming. We have also compared AdCh68-based TB vaccine with its AdHu5 counterpart in both naive animals and those with preexisting anti-AdHu5 immunity in the lung. We provide compelling evidence that AdCh68-based TB vaccine is not only safe when delivered to the respiratory tract but, importantly, is also superior to its AdHu5 counterpart in induction of T-cell responses and immune protection, and limiting lung immunopathology in the presence of preexisting anti-AdHu5 immunity in the lung. Our findings thus suggest AdCh68-based TB vaccine to be an ideal candidate for respiratory mucosal immunization, endorsing its further clinical development in humans.
Assuntos
Vacinas contra a Tuberculose/imunologia , Tuberculose Pulmonar/imunologia , Adenoviridae , Animais , Anticorpos Antibacterianos/sangue , Anticorpos Antibacterianos/imunologia , Anticorpos Neutralizantes/sangue , Anticorpos Neutralizantes/imunologia , Modelos Animais de Doenças , Ensaio de Imunoadsorção Enzimática , Citometria de Fluxo , Vetores Genéticos , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Pan troglodytesRESUMO
Interaction of mycobacteria with the host leads to retarded expression of T helper cell type 1 (Th1) immunity in the lung. However, the immune mechanisms remain poorly understood. Using in vivo and in vitro models of Mycobacterium tuberculosis (M. tb) infection, we find the immunoadaptor DAP12 (DNAX-activating protein of 12 kDa) in antigen-presenting cells (APCs) to be critically involved in this process. Upon infection of APCs, DAP12 is required for IRAK-M (interleukin-1 receptor-associated kinase M) expression, which in turn induces interleukin-10 (IL-10) and an immune-suppressed phenotype of APCs, thus leading to suppressed Th1 cell activation. Lack of DAP12 reduces APC IL-10 production and increases their Th1 cell-activating capability, resulting in expedited Th1 responses and enhanced protection. On the other hand, adoptively transferred DAP12-competent APCs suppress Th1 cell activation within DAP12-deficient hosts, and blockade of IL-10 aborts the ability of DAP12-competent APCs to suppress Th1 activation. Our study identifies the DAP12/IRAK-M/IL-10 to be a novel molecular pathway in APCs exploited by mycobacterial pathogens, allowing infection a foothold in the lung.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Células Apresentadoras de Antígenos/imunologia , Células Apresentadoras de Antígenos/metabolismo , Quinases Associadas a Receptores de Interleucina-1/metabolismo , Interleucina-10/metabolismo , Mycobacterium tuberculosis/imunologia , Células Th1/imunologia , Tuberculose Pulmonar/imunologia , Tuberculose Pulmonar/metabolismo , Animais , Apresentação de Antígeno/imunologia , Citocinas/metabolismo , Modelos Animais de Doenças , Regulação da Expressão Gênica , Mediadores da Inflamação/metabolismo , Quinases Associadas a Receptores de Interleucina-1/genética , Interleucina-10/genética , Pulmão/imunologia , Pulmão/metabolismo , Pulmão/microbiologia , Pulmão/patologia , Ativação Linfocitária/imunologia , Masculino , Camundongos , NF-kappa B/metabolismo , Transdução de SinaisRESUMO
Homologous and heterologous parenteral prime-mucosal boost immunizations have shown great promise in combating mucosal infections such as tuberculosis and AIDS. However, their immune mechanisms remain poorly defined. In particular, it is still unclear whether T-cell and innate immunity may be independently affected by these immunization modalities and how it impacts immune protective outcome. Using two virus-based tuberculosis vaccines (adenovirus (Ad) and vesicular stomatitis virus (VSV) vectors), we found that while both homologous (Ad/Ad) and heterologous (Ad/VSV) respiratory mucosal boost immunizations elicited similar T-cell responses in the lung, they led to drastically different immune protective outcomes. Compared with Ad-based boosting, VSV-based boosting resulted in poorly enhanced protection against tuberculosis. Such inferior protection was associated with differentially imprinted innate phagocytes, particularly the CD11c(+)CD11b(+/-) cells, in the lung. We identified heightened type 1 interferon (IFN) responses to be the triggering mechanism. Thus, increased IFN-ß severely blunted interleukin-12 responses in infected phagocytes, which in turn impaired their nitric oxide production and antimycobacterial activities. Our study reveals that vaccine vectors may differentially imprint innate cells at the mucosal site of immunization, which can impact immune-protective outcome, independent of T-cell immunity, and it is of importance to determine both T-cell and innate cell immunity in vaccine studies.
Assuntos
Infecções por Adenoviridae/imunologia , Adenoviridae/imunologia , Vetores Genéticos/imunologia , Fagócitos/imunologia , Infecções por Rhabdoviridae/imunologia , Linfócitos T/imunologia , Vacinas contra a Tuberculose/administração & dosagem , Vesiculovirus/imunologia , Animais , Células Cultivadas , Feminino , Imunidade Celular , Imunidade Inata , Interferon Tipo I/metabolismo , Interleucina-12/metabolismo , Camundongos , Camundongos Endogâmicos BALB C , Óxido Nítrico/metabolismoRESUMO
The immune mechanisms underlying unsatisfactory pulmonary mucosal protection by parenteral Bacillus Calmette-Guérin (BCG) immunization remain poorly understood. We found that parenteral BCG immunization failed to elicit airway luminal T cells (ALT) whereas it induced significant T cells in the lung interstitium. After Mycobacterium tuberculosis (M.tb) challenge, ALT remained missing for 10 days. The lack of ALT correlated with lack of lung protection for 14 days post-M.tb challenge. To further investigate the role of ALT, ALT were elicited in BCG-immunized animals by intranasal inoculation of M.tb culture-filtrate (CF) proteins. Installment of ALT by CF restored protection in the early phases of M.tb infection, which was linked to rapid increases in ALT, but not in lung interstitial T cells. Also, adoptive transfer of T cells to the airway lumen of BCG-immunized animals also accelerated protection. This study thus provides novel evidence that unsatisfactory lung protection by parenteral BCG immunization is due to delayed ALT recruitment after pulmonary M.tb exposure.
Assuntos
Vacina BCG/imunologia , Mucosa Respiratória/imunologia , Linfócitos T/imunologia , Tuberculose Pulmonar/imunologia , Tuberculose Pulmonar/prevenção & controle , Transferência Adotiva , Animais , Antígenos de Bactérias/imunologia , Modelos Animais de Doenças , Feminino , Memória Imunológica , Ativação Linfocitária/imunologia , Camundongos , Camundongos Endogâmicos BALB C , Mycobacterium tuberculosis/imunologia , Mucosa Respiratória/microbiologiaRESUMO
BACKGROUND: A third of the world's population has latent infection with Mycobacterium tuberculosis, and in areas of low endemicity, most cases of active tuberculosis arise as a result of reactivation of latent bacilli. We sought to establish the cellular location of these latent organisms to facilitate their elimination. METHODS: We applied in-situ PCR to sections of macroscopically normal lung tissue from 13 individuals from Ethiopia and 34 from Mexico who had died from causes other than tuberculosis. Sections of lung tissue from six Norwegian individuals (ie, individuals from a non-endemic population) acted as negative controls, and six Ethiopian tuberculosis cases acted as positive controls. FINDINGS: Control necropsy samples from the Norwegian individuals were all negative by in-situ PCR and conventional PCR, whereas all samples from known Ethiopian tuberculosis cases were positive by both methods. However, in macroscopically normal lung tissue from Ethiopian and Mexican individuals without tuberculous lesions, the in-situ PCR revealed five of 13 and ten of 34 positive individuals, respectively. These results were confirmed by conventional PCR with extracted DNA. Positive cells included alveolar and interstitial macrophages, type II pneumocytes, endothelial cells, and fibroblasts. INTERPRETATION: M. tuberculosis can persist intracellularly in lung tissue without histological evidence of tuberculous lesions. M. tuberculosis DNA is situated not only in macrophages but also in other non-professional phagocytic cells. These findings contradict the dominant view that latent organisms exist in old classic tuberculous lesions, and have important implications for strategies aimed at the elimination of latent and persistent bacilli.