Disseminated disease severity as a measure of virulence of Mycobacterium tuberculosis in the guinea pig model.

Virulence is the measure of pathogenicity of a microorganism as determined by its ability to invade host tissues and to produce severe disease. In the low-dose aerosol guinea pig model the virulence of multiple strains of Mycobacterium tuberculosis was determined by measuring time of survival, bacterial loads in target organs, and the severity of pulmonary and extra-pulmonary lesions. Erdman K01, CSU93/CDC1551 and HN878 had shorter survival times compared to the common laboratory strain H37Rv. After 30 days of the infection bacilli had disseminated from the lungs resulting in microscopically visible lesions in peribronchial lymph nodes, peripancreatic lymph nodes, spleen, liver, pancreas, adrenal and heart. The extent of the lesion necrosis paralleled virulence when survival times were used as a measure as Erdman K01 and the two clinical isolates caused more necrosis and resulted in sooner death in infected animals than the H37Rv. The extent of extra-pulmonary lesion necrosis was a better predictor of virulence than the number of viable bacilli in the tissue. Overall, this study emphasizes the point that extra-pulmonary disease is a prominent feature of the guinea pig model and dissemination to organs not normally assayed such as the heart and adrenal glands should be taken into account in the assessment of the disease process.

Lymphadenitis as a major element of disease in the guinea pig model of tuberculosis.

Guinea pigs infected by low dose aerosol with the H37Rv strain of Mycobacterium tuberculosis rapidly developed granulomatous lesions in the pulmonary parenchyma and within the intra-thoracic hilar lymph node cluster. Lung lesions showed no predilection for specific lobes and were perivascular, peribronchial and peribronchiolar throughout the subpleural, hilar and pulmonary parenchyma. Marked hilar lymph node enlargement was due to coalescing foci of subcapsular, paracortical and medullary granulomatous inflammation that progressed to necrosis that effaced normal lymph node architecture. Lymph node lesions became severe and progressed more rapidly than pulmonary lesions. Immunization with BCG 6 weeks prior to infection significantly reduced the lung and lymph node lesion burden as well as the progression to necrosis in both tissues. Lymph node inflammation in BCG immunized animals partially resolved and was replaced by fibroblasts and fibrous connective tissue while lesions from non-immunized animals continued to progress to necrosis. We discuss here the observation that the distribution and progression of lung and lymph node lesions in the guinea pig aerosol model of tuberculosis have considerable similarity to the naturally occurring disease in children.

Comprehensive RNA Polymerase II Interactomes Reveal Distinct and Varied Roles for Each Phospho-CTD Residue.

Transcription controls splicing and other gene regulatory processes, yet mechanisms remain obscure due to our fragmented knowledge of the molecular connections between the dynamically phosphorylated RNA polymerase II (Pol II) C-terminal domain (CTD) and regulatory factors. By systematically isolating phosphorylation states of the CTD heptapeptide repeat (Y1S2P3T4S5P6S7), we identify hundreds of protein factors that are differentially enriched, revealing unappreciated connections between the Pol II CTD and co-transcriptional processes. These data uncover a role for threonine-4 in 3' end processing through control of the transition between cleavage and termination. Furthermore, serine-5 phosphorylation seeds spliceosomal assembly immediately downstream of 3' splice sites through a direct interaction with spliceosomal subcomplex U1. Strikingly, threonine-4 phosphorylation also impacts splicing by serving as a mark of co-transcriptional spliceosome release and ensuring efficient post-transcriptional splicing genome-wide. Thus, comprehensive Pol II interactomes identify the complex and functional connections between transcription machinery and other gene regulatory complexes.

Post-exposure vaccination against Mycobacterium tuberculosis.

Enhancing immunity to tuberculosis in animal models after exposure to the infection has proved difficult. In this study we used a newly described flow cytometric technique to monitor changes in cell populations accumulating in the lungs of guinea pigs challenged by low-dose aerosol infection with Mycobacterium tuberculosis and vaccinated 10 days later. On day 40 after infection the fusion protein F36 and a pool of Ag85A and ESAT6 vaccines had significant effects on the bacterial load, showed increased expression of the activation marker CD45+ on CD4+ T cells, and reduced numbers of heterophils. Lung pathology and pathology scores were marginally improved in animals given these vaccines, but lymph node pathology was not influenced. Despite early effects no changes in long-term survival were seen. These results suggest that a single post-exposure vaccination can initially slow the disease process. However, this effect is transient, but this could be of use in an multidrug resistant/extremely drug resistant outbreak situation because it could potentially slow the infection long enough to complete drug susceptibility testing and initiate effective chemotherapy.

Flexible low-cost system for small animal aerosol inhalation exposure to drugs, proteins, inflammatory agents, and infectious agents.

The design for a simple, low-cost aerosol generation system for rodent inhalation studies is described here. This system is appropriate for low biohazard-level agents. In this study, two biosafety level 2 agents, Pasturella pneumotropica and Pseudomonas aeruginosa, were tested successfully. This system was also used to immunize mice and guinea pigs in ovalbumin-based models of pulmonary inflammation. This design is appropriate for studies with limited budgets and lower-level biosafety containment.

Influence of Mycobacterium bovis BCG vaccination on cellular immune response of guinea pigs challenged with Mycobacterium tuberculosis.

Mycobacterium bovis bacillus Calmette-Guérin (BCG) currently remains the only licensed vaccine for the prevention of tuberculosis. In this study, we used a newly described flow cytometric technique to monitor changes in cell populations accumulating in the lungs and lymph nodes of naïve and vaccinated guinea pigs challenged by low-dose aerosol infection with virulent Mycobacterium tuberculosis. As anticipated, vaccinated guinea pigs controlled the growth of the challenge infection more efficiently than controls did. This early phase of bacterial control in immune animals was associated with increased accumulation of CD4 and CD8 T cells, including cells expressing the activation marker CD45, as well as macrophages expressing class II major histocompatibility complex molecules. As the infection continued, the numbers of T cells in the lungs of vaccinated animals waned, whereas the numbers of these cells expressing CD45 increased. Whereas BCG vaccination reduced the influx of heterophils (neutrophils) into the lungs, an early B-cell influx was observed in these vaccinated animals. Overall, vaccine protection was associated with reduced pathology and lung damage in the vaccinated animals. These data provide the first direct evidence that BCG vaccination accelerates the influx of protective T-cell and macrophage populations into the infected lungs, diminishes the accumulation of nonprotective cell populations, and reduces the severity of lung pathology.

The cellular immune response to Mycobacterium tuberculosis infection in the guinea pig.

Pulmonary tuberculosis in guinea pigs is an extremely useful model for drug and vaccine testing due to the fact that its pathological disease process is similar to that present in humans. Progress in this field has been hindered because the tools necessary to undertake a complete immunological analysis of the guinea pig cellular immune response against Mycobacterium tuberculosis have been lacking. In this study, we combined a new flow cytometric gating strategy with immunohistochemistry to track T cells, B cells, and the MIL4 Ab, which detects both guinea pig heterophils (neutrophils) and eosinophils, to provide the first documentation of the kinetics of influx and positioning of these cell populations. The results show that the responding T cells are mostly CD4 cells and that after day 30 of the infection numbers of these cells in the lungs drops dramatically. These appear to be replaced by a steady increase in B cells and granulocytes which was associated with worsening lung pathology. These data reveal new information about the cellular phenotypes which mediate protective immunity or host immunopathogenesis during M. tuberculosis infection in this key animal model.

Imaging of amyloid burden and distribution in cerebral amyloid angiopathy.

OBJECTIVE: Cerebrovascular deposition of beta-amyloid (cerebral amyloid angiopathy [CAA]) is a major cause of hemorrhagic stroke and a likely contributor to vascular cognitive impairment. We evaluated positron emission tomographic imaging with the beta-amyloid-binding compound Pittsburgh Compound B (PiB) as a potential noninvasive method for detection of CAA. We hypothesized that amyloid deposition would be observed with PiB in CAA, and based on the occipital predilection of CAA pathology and associated hemorrhages, that specific PiB retention would be disproportionately greater in occipital lobes. METHODS: We compared specific cortical PiB retention in 6 nondemented subjects diagnosed with probable CAA with 15 healthy control subjects and 9 patients with probable Alzheimer's disease (AD). RESULTS: All CAA and AD subjects were PiB-positive, both by distribution volume ratio measurements and by visual inspection of positron emission tomographic images. Global cortical PiB retention was significantly increased in CAA (distribution volume ratio 1.18 +/- 0.06) relative to healthy control subjects (1.04 +/- 0.10; p = 0.0009), but was lower in CAA than in AD subjects (1.41 +/- 0.17; p = 0.002). The occipital-to-global PiB ratio, however, was significantly greater in CAA than in AD subjects (0.99 +/- 0.07 vs 0.86 +/- 0.05; p = 0.003). INTERPRETATION: We conclude that PiB-positron emission tomography can detect cerebrovascular beta-amyloid and may serve as a method for identifying the extent of CAA in living subjects.

Pulmonary lymphatics are primary sites of Mycobacterium tuberculosis infection in guinea pigs infected by aerosol.

Mycobacterium tuberculosis causes a lymphatic vasculitis in the lungs of guinea pigs infected by a low-dose aerosol. This observation suggests that in addition to being a direct conduit from the lungs to the regional lymph nodes, pulmonary lymphatics are themselves sites of infection and could be the site of latent infection.

Effects of major histocompatibility complex class II knockout on mouse bone mechanical properties during development.

We investigated the effect of major histocompatibility complex class II (MHC II) knockout on the development of the mouse peripheral skeleton. These C2D mice had less skeletal development at 8, 12 and 16 weeks of age compared to wild-type C57BL/6J (B6) male mice. The C2D mice had decreased femur mechanical, geometric and compositional measurements compared to wild type mice at each of these ages. C2D femur stiffness (S), peak force in 3-pt bending (Pm), and mineral mass (Min-M) were 74%, 64% and 66%, respectively, of corresponding B6 values at 8 weeks of age. Similar differences were measured at 12 weeks (for which C2D femoral S, Pm and Min-M were 71%, 72% and 73%, respectively, of corresponding B6 values) and at 16 weeks (for which C2D femoral S, Pm and Min-M were 80%, 66% and 61%, respectively, of corresponding B6 values). MHC II knockout delays the development of adult bone properties and is accompanied by lower body mass compared to wild-type controls.