A multi-disciplinary approach to implementation science: the NIH-PEPFAR PMTCT implementation science alliance.

In resource-limited countries, interventions to prevent mother-to-child HIV transmission (PMTCT) have not yet realized their full potential health impact, illustrating the common gap between the scientific proof of an intervention's efficacy and effectiveness and its successful implementation at scale into routine health services. For PMTCT, this gap results, in part, from inadequate adaptation of PMTCT interventions to the realities of the implementation environment, including client and health care worker behaviors and preferences, health care policies and systems, and infrastructure and resource constraints. Elimination of mother-to-child HIV transmission can only be achieved through understanding of key implementation barriers and successful adaptation of scientifically proven interventions to the local environment. Central to such efforts is implementation science (IS), which aims to investigate and address major bottlenecks that impede effective implementation and to test new approaches to identifying, understanding, and overcoming barriers to the adoption, adaptation, integration, scale-up, and sustainability of evidence-based interventions. Advancing IS will require deliberate and strategic efforts to facilitate collaboration, communication, and relationship-building among researchers, implementers, and policy-makers. To speed the translation of effective PMTCT interventions into practice and advance IS more broadly, the US National Institutes of Health, in collaboration with the President's Emergency Plan for AIDS Relief launched the National Institutes of Health/President's Emergency Plan for AIDS Relief PMTCT IS Alliance, comprised of IS researchers, PMTCT program implementers, and policy-makers as an innovative platform for interaction and coordination.

HIV and noncommunicable disease comorbidities in the era of antiretroviral therapy: a vital agenda for research in low- and middle-income country settings.

In this special 2014 issue of JAIDS, international investigator teams review a host of noncommunicable diseases (NCDs) that are often reported among people living and aging with HIV in sub-Saharan Africa. With the longer lifespans that antiretroviral therapy programs have made possible, NCDs are occurring due to a mix of chronic immune activation, medication side effects, coinfections, and the aging process itself. Cancer; cardiovascular and pulmonary diseases; metabolic, body, and bone disorders; gastrointestinal, hepatic, and nutritional aspects; mental, neurological, and substance use disorders; and renal and genitourinary diseases are discussed. Cost-effectiveness, key research methods, and issues of special importance in Asia, Latin America, and the Caribbean are also addressed. In this introduction, we present some of the challenges and opportunities for addressing HIV and NCD comorbidities in low- and middle-income countries, and preview the research agenda that emerges from the articles that follow.

Structural and biochemical characterization of the essential DsbA-like disulfide bond forming protein from Mycobacterium tuberculosis.

BACKGROUND: Bacterial Disulfide bond forming (Dsb) proteins facilitate proper folding and disulfide bond formation of periplasmic and secreted proteins. Previously, we have shown that Mycobacterium tuberculosis Mt-DsbE and Mt-DsbF aid in vitro oxidative folding of proteins. The M. tuberculosis proteome contains another predicted membrane-tethered Dsb protein, Mt-DsbA, which is encoded by an essential gene. RESULTS: Herein, we present structural and biochemical analyses of Mt-DsbA. The X-ray crystal structure of Mt-DsbA reveals a two-domain structure, comprising a canonical thioredoxin domain with the conserved CXXC active site cysteines in their reduced form, and an inserted α-helical domain containing a structural disulfide bond. The overall fold of Mt-DsbA resembles that of other DsbA-like proteins and not Mt-DsbE or Mt-DsbF. Biochemical characterization demonstrates that, unlike Mt-DsbE and Mt-DsbF, Mt-DsbA is unable to oxidatively fold reduced, denatured hirudin. Moreover, on the substrates tested in this study, Mt-DsbA has disulfide bond isomerase activity contrary to Mt-DsbE and Mt-DsbF. CONCLUSION: These results suggest that Mt-DsbA acts upon a distinct subset of substrates as compared to Mt-DsbE and Mt-DsbF. One could speculate that Mt-DsbE and Mt-DsbF are functionally redundant whereas Mt-DsbA is not, offering an explanation for the essentiality of Mt-DsbA in M. tuberculosis.

The Mycobacterium tuberculosis secreted protein Rv0203 transfers heme to membrane proteins MmpL3 and MmpL11.

Mycobacterium tuberculosis is the causative agent of tuberculosis, which is becoming an increasingly global public health problem due to the rise of drug-resistant strains. While residing in the human host, M. tuberculosis needs to acquire iron for its survival. M. tuberculosis has two iron uptake mechanisms, one that utilizes non-heme iron and another that taps into the vast host heme-iron pool. To date, proteins known to be involved in mycobacterial heme uptake are Rv0203, MmpL3, and MmpL11. Whereas Rv0203 transports heme across the bacterial periplasm or scavenges heme from host heme proteins, MmpL3 and MmpL11 are thought to transport heme across the membrane. In this work, we characterize the heme-binding properties of the predicted extracellular soluble E1 domains of both MmpL3 and MmpL11 utilizing absorption, electron paramagnetic resonance, and magnetic circular dichroism spectroscopic methods. Furthermore, we demonstrate that Rv0203 transfers heme to both MmpL3-E1 and MmpL11-E1 domains at a rate faster than passive heme dissociation from Rv0203. This work elucidates a key step in the mycobacterial uptake of heme, and it may be useful in the development of anti-tuberculosis drugs targeting this pathway.

Discovery and characterization of a unique mycobacterial heme acquisition system.

Mycobacterium tuberculosis must import iron from its host for survival, and its siderophore-dependent iron acquisition pathways are well established. Here we demonstrate a newly characterized pathway, whereby M. tuberculosis can use free heme and heme from hemoglobin as an iron source. Significantly, we identified the genomic region, Rv0202c-Rv0207c, responsible for the passage of heme iron across the mycobacterial membrane. Key players of this heme uptake system were characterized including a secreted protein and two transmembrane proteins, all three specific to mycobacteria. Furthermore, the crystal structure of the key heme carrier protein Rv0203 was found to have a unique fold. The discovery of a unique mycobacterial heme acquisition pathway opens new avenues of exploration into mycobacterial therapeutics.