Tuberculosis (TB) is a global pandemic, partially due to the failure of vaccination approaches. Novel anti-TB vaccines are therefore urgently required. Here we show that aerosol immunization of macaques with the Mtb mutant in SigH (MtbΔsigH) results in significant recruitment of inducible bronchus-associated lymphoid tissue as well as CD4+ and CD8+ T cells expressing activation and proliferation markers to the lungs. Further, the findings indicate that pulmonary vaccination with MtbΔsigH elicited strong central memory CD4+ and CD8+ T cell responses in the lung. Vaccination with MtbΔsigH results in significant protection against a lethal TB challenge, as evidenced by a ~three log reduction in bacterial burdens, significantly diminished clinical manifestations and granulomatous pathology and characterized by the presence of profound iBALT. This highly protective response is virtually absent in unvaccinated and BCG-vaccinated animals after challenge. These results suggest that future TB vaccine candidates can be developed based on MtbΔsigH.
Delayed adaptive responses, a hallmark of M. tuberculosis infection, not only lead to persistence but also interfere with the development of effective antituberculosis vaccines. The DosR regulon therefore modulates both the magnitude and the timing of adaptive immune responses in response to hypoxia in vivo, resulting in persistent infection. Hence, DosR regulates key aspects of the M. tuberculosis life cycle and limits lung pathology.
Mycobacterium tuberculosis (MTB) is a highly successful pathogen because of its ability to persist in human lungs for long periods of time. MTB modulates several aspects of the host immune response. Lymphocyte-activation gene 3 (LAG3) is a protein with a high affinity for the CD4 receptor and is expressed mainly by regulatory T cells with immunomodulatory functions. To understand the function of LAG3 during MTB infection, a nonhuman primate model of tuberculosis, which recapitulates key aspects of natural human infection in rhesus macaques (Macaca mulatta), was used. We show that the expression of LAG3 is highly induced in the lungs and particularly in the granulomatous lesions of macaques experimentally infected with MTB. Furthermore, we show that LAG3 expression is not induced in the lungs and lung granulomas of animals exhibiting latent tuberculosis infection. However, simian immunodeficiency virus-induced reactivation of latent tuberculosis infection results in an increased expression of LAG3 in the lungs. This response is not observed in nonhuman primates infected with non-MTB bacterial pathogens, nor with simian immunodeficiency virus alone. Our data show that LAG3 was expressed primarily on CD4(+) T cells, presumably by regulatory T cells but also by natural killer cells. The expression of LAG3 coincides with high bacterial burdens and changes in the host type 1 helper T-cell response.
Acute phase serum amyloid A proteins (A-SAAs) are multifunctional apolipoproteins produced in large amounts during the acute phase of an inflammation and also during the development of chronic inflammatory diseases. In this study we present a Saa1-luc transgenic mouse model in which SAA1 gene expression can be monitored by measuring luciferase activity using a noninvasive imaging system. When challenged with LPS, TNF-α, or IL-1β, in vivo imaging of Saa1-luc mice showed a 1000- to 3000-fold induction of luciferase activity in the hepatic region that peaked 4–7 h after treatment. The induction of liver luciferase expression was consistent with an increase in SAA1 mRNA in the liver and a dramatic elevation of the serum SAA1 concentration. Ex vivo analyses revealed luciferase induction in many tissues, ranging from several-fold (brain) to >5000-fold (liver) after LPS or TNF-α treatment. Pretreatment of mice with the proteasome inhibitor bortezomib significantly suppressed LPS-induced SAA1 expression. These results suggested that proteasome inhibition, perhaps through the NF-κB signaling pathway, may regulate SAA1 expression. During the development of acute arthritis triggered by intra-articular administration of zymosan, SAA1 expression was induced both locally at the knee joint and systemically in the liver, and the induction was significantly suppressed by bortezomib. Induction of SAA1 expression was also demonstrated during contact hypersensitivity induced by topical application of oxazolone. These results suggest that both local and systemic induction of A-SAA occur during inflammation and may contribute to the pathogenesis of chronic inflammatory diseases associated with amyloid deposition.
Mycobacterium tuberculosis (Mtb) persists within lung granulomas, despite being subjected to diverse stress conditions, including hypoxia. We hypothesized that the response of host phagocytes to Mtb experiencing hypoxia is radically altered and designed in vitro experiment to study this phenomenon. Hypoxia-stressed (Mtb-H) and aerobically grown Mtb (Mtb-A) were used to infect Rhesus Macaque Bone Marrow Derived Macrophages (Rh-BMDMs) and the comparative host response to Mtb infection studied. Mechanistic insights were gained by employing RNAi. Mtb-H accumulated significantly lower bacterial burden during growth in Rh-BMDMs, concomitantly generating a drastically different host transcriptional profile (with only <2% of all genes perturbed by either infection being shared between the two groups). A key component of this signature was significantly higher TNF and apopotosis in Mtb-H- compared to Mtb-A-infected Rh-BMDMs. Silencing of TNF by RNAi reversed the significant control of Mtb replication. These results indicate a potential mechanism for the rapid clearance of hypoxia-conditioned bacilli by phagocytes. In conclusion, hypoxia-conditioned Mtb undergo significantly different interactions with host macrophages compared to Mtb grown in normoxia. These interactions result in the induction of the TNF signaling pathway, activation of apoptosis, and DNA-damage stress response. Our results show that Mtb-H bacilli are particularly susceptible to killing governed by TNF.