Ability of Innate Defence Regulator Peptides IDR-1002, IDR-HH2 and IDR-1018 to Protect against Mycobacterium tuberculosis Infections in Animal Models Bruno Rivas-Santiago 1 , Julio E. Castan ˜ eda-Delgado 1,4 , Cesar E. Rivas Santiago 2,3 , Matt Waldbrook 5 , Irma Gonza ´ lez-Curiel 1,4 , Juan C. Leo ´ n–Contreras 3 , Jose Antonio Enciso-Moreno 1 , Victor del Villar 2 , Jazmin Mendez-Ramos 2 , Robert E. W. Hancock 5 , Rogelio Hernandez-Pando 3 * 1 Medical Research Unit Zacatecas, Mexican Institute of Social Security-IMSS, Zacatecas, Mexico, 2 Section of Experimental Pathology, National Institute of Medical Sciences and Nutrition ‘‘Salvador Zubira ´n’’, Mexico City, Mexico, 3 UMDNJ-School of Public Health, Department of Environmental and Occupational Health, Center for Global Public Health, Piscataway, New Jersey, United States of America, 4 Department of Immunology, School of Medicine, Autonomous University of San Luis Potosi, San Luis Potosi, Mexico, 5 Centre for Microbial Diseases and Immunity Research, University of British Columbia, Vancouver, British Columbia, Canada Abstract Tuberculosis is an ongoing threat to global health, especially with the emergence of multi drug-resistant (MDR) and extremely drug-resistant strains that are motivating the search for new treatment strategies. One potential strategy is immunotherapy using Innate Defence Regulator (IDR) peptides that selectively modulate innate immunity, enhancing chemokine induction and cell recruitment while suppressing potentially harmful inflammatory responses. IDR peptides possess only modest antimicrobial activity but have profound immunomodulatory functions that appear to be influential in resolving animal model infections. The IDR peptides HH2, 1018 and 1002 were tested for their activity against two M. tuberculosis strains, one drug-sensitive and the other MDR in both in vitro and in vivo models. All peptides showed no cytotoxic activity and only modest direct antimicrobial activity versus M. tuberculosis (MIC of 15–30 mg/ml). Nevertheless peptides HH2 and 1018 reduced bacillary loads in animal models with both the virulent drug susceptible H37Rv strain and an MDR isolate and, especially 1018 led to a considerable reduction in lung inflammation as revealed by decreased pneumonia. These results indicate that IDR peptides have potential as a novel immunotherapy against TB. Citation: Rivas-Santiago B, Castan ˜ eda-Delgado JE, Rivas Santiago CE, Waldbrook M, Gonza ´lez-Curiel I, et al. (2013) Ability of Innate Defence Regulator Peptides IDR-1002, IDR-HH2 and IDR-1018 to Protect against Mycobacterium tuberculosis Infections in Animal Models. PLoS ONE 8(3): e59119. doi:10.1371/ journal.pone.0059119 Editor: Olivier Neyrolles, Institut de Pharmacologie et de Biologie Structurale, France Received November 7, 2012; Accepted February 11, 2013; Published March 21, 2013 Copyright: ß 2013 Rivas-Santiago et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: REWH funding from the Grand Challenges in Global Health Research program through the Foundation of the National Institutes of Health and the Canadian Institutes for Health Research. REWH holds a Canada Research Chair in antimicrobials and genomics, BRS acknowledges the Mexican Institute for Social Security-IMSS grant project FIS/IMSS/PROT/G10/832. RHP holds the grant project CONACyT (contract: 84456). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: Peptides IDR-1018, HH2 and 1002, discovered by Hancock and colleagues, have been filed for patent protection in multiple jurisdictions, assigned to UBC and licenced to Elanco (IDR-1018,HH2) for Animal Health applications and IDR-1018 is also under development as a potential therapeutic for hyperinflammation in Cystic Fibrosis with funding from Cystic Fibrosis Canada’s Translational Initiative. Peptides 1002 and HH2 have also been developed as components of vaccine adjuvant formulations which have been licensed to Prepare with other licences pending. The peptide IDR-1018 has received Notice of allowance in the United States of America and New Zealand. * E-mail: rhdezpando@hotmail.com Introduction Mycobacterium tuberculosis (Mtb), the cause of human tuberculosis (TB) is one of the major killers among the infectious organisms causing around 1.5 to 3 million deaths per year [1]. It has been estimated that one third of the human population carries Mtb and 10% of these people will develop active disease at some time in their lives, creating an enormous reservoir. Although the incidence of TB [1] has decreased during the past two decades, the rise of multi drug-resistant (MDR) and extensively drug-resistant (XDR) and, in the Middle East, completely resistant strains, is creating concerns regarding how to effectively treat TB infections by these recalcitrant strains [1]. In the past 40 years there has no broadly successful new Mtb drug developed. Therefore, there is a strong incentive to develop new treatments for TB and/or improve the ones currently in use to enable significant reductions in the duration of therapy and enhance patient survival. In addition to the development of new anti-tubercular drugs, immunotherapy has strong potential in treatment of this significant disease [2]. Endogenous host defence peptides are well recognized compo- nents of the innate immunity and they have been suggested to have an important role in TB infections. Such peptides can inhibit microbial growth directly through a variety of membrane and non-membrane targets [3]. However we and others have argued that their major activity involves the favourable modulation of innate immunity [2–6], upregulating protective immunity by mechanisms such as increasing the production of chemokines to enable the recruitment of immune cells including phagocytes, while dampening potentially harmful inflammation [3,4]. The major groups of host defence peptides in humans are the defensins and a single cathelicidin, LL-37. It has been reported that alterations in the production of these molecules increases susceptibility to infectious diseases, including TB [7]. There are PLOS ONE | www.plosone.org 1 March 2013 | Volume 8 | Issue 3 | e59119