Objective. An increased risk of tuberculosis has been documented in humans treated with tumor necrosis factor ␣ (TNF␣)-neutralizing agents. In murine models, impaired signaling by TNF causes exacerbation of both acute and chronic infection associated with aberrant granuloma formation and maintenance. This study was undertaken to investigate immune modulation in the setting of TNF neutralization in primary and latent tuberculosis in a non-human primate model.Methods. Cynomolgus macaques 4 years of age or older were infected with Mycobacterium tuberculosis and subjected to clinical, microbiologic, immunologic, and radiographic examinations. Monkeys were classified as having active or latent disease 6-8 months after infection, based on clinical criteria. Monkeys used in acute infection studies were randomized to receive either adalimumab (prior to and during infection) or no treatment. Monkeys with latent infection that were randomized to receive TNF-neutralizing agent were given either an inhibitor of soluble TNF, recombinant methionyl human soluble TNF receptor I (p55-TNFRI), or adalimumab. Control monkeys with latent infection were given no treatment or saline. Data from previously studied monkeys with active or latent disease were also used for comparison.Results. Administration of TNF-neutralizing agents prior to M tuberculosis infection resulted in fulminant and disseminated disease by 8 weeks after infection. Neutralization of TNF in latently infected cynomolgus macaques caused reactivation in a majority of animals as determined by gross pathologic examination and bacterial burden. A spectrum of dissemination was noted, including extrapulmonary disease. Surprisingly, monkeys that developed primary and reactivation tuberculosis after TNF neutralization had similar granuloma structure and composition to that of control monkeys with active disease. TNF neutralization was associated with increased levels of interleukin-12, decreased levels of CCL4, increased chemokine receptor expression, and reduced mycobacteria-induced interferon-␥ production in blood but not in the affected mediastinal lymph nodes. Finally, the first signs of reactivation often occurred in thoracic lymph nodes.
Previous studies in mice and humans have suggested an important role for CD8+ T cells in host defense to Mtb. Recently, we have described human, Mtb-specific CD8+ cells that are neither HLA-A, B, or C nor group 1 CD1 restricted, and have found that these cells comprise the dominant CD8+ T cell response in latently infected individuals. In this report, three independent methods are used to demonstrate the ability of these cells to recognize Mtb-derived antigen in the context of the monomorphic HLA-E molecule. This is the first demonstration of the ability of HLA-E to present pathogen-derived antigen. Further definition of the HLA-E specific response may aid development of an effective vaccine against tuberculosis.
The epithelial Na ؉ channel (ENaC) regulates epithelial salt and water reabsorption, processes that require significant expenditure of cellular energy. To test whether the ubiquitous metabolic sensor AMP-activated kinase (AMPK) regulates ENaC, we examined the effects of AMPK activation on amiloride-sensitive currents in Xenopus oocytes and polarized mouse collecting duct mpkCCD c14 cells. Microinjection of oocytes expressing mouse ENaC (mENaC) with either active AMPK protein or an AMPK activator inhibited mENaC currents relative to controls as measured by two-electrode voltageclamp studies. Similarly, pharmacological AMPK activation or overexpression of an activating AMPK mutant in mpkCCD c14 cells inhibited amiloride-sensitive short circuit currents. Expression of a degenerin mutant -mENaC subunit (S518K) along with wild type ␣ and ␥ increased the channel open probability (P o ) to ϳ1. However, AMPK activation inhibited currents similarly with expression of either degenerin mutant or wild type mENaC. Single channel recordings under these conditions demonstrated that neither P o nor channel conductance was affected by AMPK activation. Moreover, expression of a Liddle's syndrome-type -mENaC mutant (Y618A) greatly enhanced ENaC whole cell currents relative to wild type ENaC controls and prevented AMPKdependentinhibition.ThesefindingsindicatethatAMPKdependent ENaC inhibition is mediated through a decrease in the number of active channels at the plasma membrane (N), presumably through enhanced Nedd4-2-dependent ENaC endocytosis. The AMPK-ENaC interaction appears to be indirect; AMPK did not bind ENaC in cells, as assessed by in vivo pull-down assays, nor did it phosphorylate ENaC in vitro. In summary, these results suggest a novel mechanism for coupling ENaC activity and renal Na ؉ handling to cellular metabolic status through AMPK, which may help prevent cellular Na ؉ loading under hypoxic or ischemic conditions.The maintenance of transmembrane ion and solute gradients is a crucial process that permits normal cellular functioning, viability, and coordinated transepithelial transport but also consumes a substantial portion of total cellular energy (1). Under conditions of metabolic stress, the expression and activity of many membrane transport proteins including ENaC 1 are inhibited, thereby limiting the dissipation of ionic gradients and preserving the cellular energy required to maintain them (2). However, the cellular mechanisms that link membrane transport to energy production and metabolic status have remained elusive.AMPK is a ubiquitous metabolic-sensing Ser/Thr kinase that exists as a heterotrimer composed of a catalytic ␣ subunit and regulatory  and ␥ subunits. Its activity increases during conditions of metabolic stress, in response to elevated intracellular AMP:ATP ratios (3). A parallel activation pathway involves phosphorylation of the ␣ subunit by a recently identified upstream LKB1 kinase complex at a Thr residue in its activation loop (4). The earliest discovered substrates of AMPK were important ...
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta variant quickly rose to dominance in mid-2021, displacing other variants, including Alpha. Studies using data from the United Kingdom and India estimated that Delta was 40-80% more transmissible than Alpha, allowing Delta to become the globally dominant variant. However, it was unclear if the ostensible difference in relative transmissibility was due mostly to innate properties of Delta's infectiousness or differences in the study populations. To investigate, we formed a partnership with SARS-CoV-2 genomic surveillance programs from all six New England US states. By comparing logistic growth rates, we found that Delta emerged 37-163% faster than Alpha in early 2021 (37% Massachusetts, 75% New Hampshire, 95% Maine, 98% Rhode Island, 151% Connecticut, and 163% Vermont). We next computed variant-specific effective reproductive numbers and estimated that Delta was 58-120% more transmissible than Alpha across New England (58% New Hampshire, 68% Massachusetts, 76% Connecticut, 85% Rhode Island, 98% Maine, and 120% Vermont). Finally, using RT-PCR data, we estimated that Delta infections generate on average ~6 times more viral RNA copies per mL than Alpha infections. Overall, our evidence indicates that Delta's enhanced transmissibility could be attributed to its innate ability to increase infectiousness, but its epidemiological dynamics may vary depending on the underlying immunity and behavior of distinct populations.
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