Vaccine 33 (2015) 1353–1359 Contents lists available at ScienceDirect Vaccine j our na l ho me page: www.elsevier.com/locate/vaccine Deletion of zmp1 improves Mycobacterium bovis BCG-mediated protection in a guinea pig model of tuberculosis Peter Sander a,b,∗ , Simon Clark c , Agnese Petrera a,1 , Cristina Vilaplana d , Michael Meuli a , Petra Selchow a , Andrea Zelmer e , Deepa Mohanan f , Nuria Andreu e , Emma Rayner c , Michael Dal Molin a , Gregory J. Bancroft e , Pål Johansen f , Pere-Joan Cardona d , Ann Williams c , Erik C. Böttger a,b a Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland b Nationales Zentrum für Mykobakterien, Gloriastrasse 30/32, 8006 Zurich, Switzerland c Microbiology Services, Public Health England, Porton Down, Salisbury, Wiltshire, United Kingdom d Unitat de Tuberculosi Experimental, Fundació Institut d’Investigació en Ciències de la Salut Germans Trias i Pujol, Universitat Autonoma de Barcelona, CIBERES, Badalona, Catalonia, Spain e Deptartment of Immunology and Infection, London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom f Department of Dermatology, University Hospital Zurich, Zurich, Switzerland a r t i c l e i n f o Article history: Received 10 December 2014 Accepted 14 January 2015 Available online 2 February 2015 Keywords: Tuberculosis BCG Protection Safety Live vaccine Protease Guinea pig a b s t r a c t Having demonstrated previously that deletion of zinc metalloprotease zmp1 in Mycobacterium bovis BCG increased immunogenicity of BCG vaccines, we here investigated the protective efficacy of BCG zmp1 deletion mutants in a guinea pig model of tuberculosis infection. zmp1 deletion mutants of BCG provided enhanced protection by reducing the bacterial load of tubercle bacilli in the lungs of infected guinea pigs. The increased efficacy of BCG due to zmp1 deletion was demonstrated in both BCG Pasteur and BCG Denmark indicating that the improved protection by zmp1 deletion is independent from the BCG sub-strain. In addition, unmarked BCG zmp1 mutant strains showed a better safety profile in a CB-17 SCID mouse survival model than the parental BCG strains. Together, these results support the further development of BCG zmp1 for use in clinical trials. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Tuberculosis (TB) caused by the bacterial pathogen Mycobac- terium tuberculosis, is a major cause of human morbidity and mortality. It is estimated that 1.5 million people, among them 80 000 children, died of the disease in 2013. About 9 million new cases of TB, including 550 000 in children, occur each year and one third of the world’s population, 2 billion people, is latently infected according to WHO (Global Tuberculosis Report 2014, WHO; http://www.who.int/tb/publications/global report/en/). Approxi- mately 5% of these latently infected individuals will develop active TB at a later time point. WHO has declared elimination of TB by the year 2050 a global target [1]. The low decline in ∗ Corresponding author. Tel.: +41 44 634 2684; fax: +41 44 634 4906. E-mail address: psander@imm.uzh.ch (P. Sander). 1 Present address: Institut für Molekulare Medizin und Zellforschung, Universität Freiburg, Freiburg, Germany. the incidence of TB observed in the past years is insufficient to reach this goal. Even the most stringent implementation of diagnostic techniques and medication currently available will not suffice. Continuous in vitro passaging of Mycobacterium bovis, the causative agent of bovine tuberculosis, gave rise to the currently available attenuated TB live vaccine. Deletion of the Region of Dif- ference 1 (RD1), encoding the specialized protein secretion system ESX-1, is considered the primary genetic alteration responsible for attenuation [2]. Named after its inventors, the live vaccine M. bovis bacille Calmette-Guérin (BCG) was first applied to humans in 1921. Still today, BCG is the only licensed TB vaccine and more than 4 bil- lion doses have been applied [3]. BCG confers consistent protection against TB meningitis and disseminated TB in children. However, protective efficacy of BCG against the most prevalent form of TB, adult lung TB, is highly variable. Protective efficacy varied between 0% and 85% in different trials [4,5]. According to WHO, improve- ment of TB vaccines has high priority and is a corner stone in TB elimination. http://dx.doi.org/10.1016/j.vaccine.2015.01.058 0264-410X/© 2015 Elsevier Ltd. All rights reserved.