Evidence for the Effect of Vaccination on Host-Pathogen Interactions in a Murine Model of Pulmonary Tuberculosis by Mycobacterium tuberculosis.

The global control of Tuberculosis remains elusive, and Bacillus Calmette-Guérin (BCG) -the most widely used vaccine in history-has proven insufficient for reversing this epidemic. Several authors have suggested that the mass presence of vaccinated hosts might have affected the Mycobacterium tuberculosis (MTB) population structure, and this could in turn be reflected in a prevalence of strains with higher ability to circumvent BCG-induced immunity, such as the recent Beijing genotype. The effect of vaccination on vaccine-escape variants has been well-documented in several bacterial pathogens; however the effect of the interaction between MTB strains and vaccinated hosts has never been previously described. In this study we show for the first time the interaction between MTB Beijing-genotype strains and BCG-vaccinated hosts. Using a well-controlled murine model of progressive pulmonary tuberculosis, we vaccinated BALB/c mice with two different sub-strains of BCG (BCG-Phipps and BCG-Vietnam). Following vaccination, the mice were infected with either one of three selected MTB strains. Strains were selected based on lineage, and included two Beijing-family clinical isolates (strains 46 and 48) and a well-characterized laboratory strain (H37Rv). Two months after infection, mice were euthanized and the bacteria extracted from their lungs. We characterized the genomic composite of the bacteria before and after exposure to vaccinated hosts, and also characterized the local response to the bacteria by sequencing the lung transcriptome in animals during the infection. Results from this study show that the interaction within the lungs of the vaccinated hosts results in the selection of higher-virulence bacteria, specifically for the Beijing genotype strains 46 and 48. After exposure to the BCG-induced immune response, strains 46 and 48 acquire genomic mutations associated with several virulence factors. As a result, the bacteria collected from these vaccinated hosts have an increased ability for immune evasion, as shown in both the host transcriptome and the histopathology studies, and replicates far more efficiently compared to bacteria collected from unvaccinated hosts or to the original-stock strain. Further research is warranted to ascertain the pathways associated with the genomic alterations. However, our results highlight novel host-pathogen interactions induced by exposure of MTB to BCG vaccinated hosts.

Tipificación con oligonucleótidos espaciadores de Mycobacterium tuberculosis en Cuba / Spacer oligonucleotide typing of Mycobacterium tuberculosis in Cuba

Introducción: el conocimiento de los linajes de Mycobacterium tuberculosis es importante para entender el origen, evolución y propagación de la bacteria. Objetivo: determinar los patrones genéticos de M. tuberculosis circulantes en Cuba. Métodos: estudio descriptivo de corte transversal con un componente analítico en Cuba, en el período comprendido de enero de 2009 a diciembre de 2010. Se aplicó la tipificación con oligonucleótidos espaciadores (Spoligotyping) a 308 aislamientos de M. tuberculosis del período 2009-2010. La clasificación en genotipos se realizó según la base de datos internacional SpolDB4. Los resultados se analizaron además con la herramienta web en línea MIRU-VNTRplus y se compararon con los patrones genéticos de M. tuberculosis identificados en 1993-1995 en Cuba. Resultados: se definieron 79 patrones genotípicos diferentes, de los cuales 46 (62 por ciento) fueron patrones no reportados anteriormente en SpolDB4. Los 22 agrupamientos definidos incluyeron al 75,4 por ciento de los aislamientos estudiados. Se encontraron cinco familias genéticas fundamentales: Beijing (25,6 por ciento), S (19,2 por ciento), LAM (16,9 por ciento), Haarlem (16,9 por ciento) y T (5,8 por ciento). La familia S prevaleció en la región Occidental (OR=3,4; 95 por ciento IC:1,8-6,3; p<0,05), Beijing en el Centro de Cuba (OR=6,7; 95 por ciento IC:3,7-11,9; p<0,05) y LAM (OR=3,0; 95 por ciento IC:1,6-5,6; p<0.05) y Haarlem en la zona Oriental (OR=1,8; 95 por ciento IC:1,0-3,4; p<0,05). Conclusiones: se observó una gran diversidad genética entre los aislamientos de M. tuberculosis circulante en Cuba en 2009-2010. En el país, la estructura genética de la población de M. tuberculosis ha variado en el tiempo con una disminución de genotipos endémicos como Haarlem y T y un aumento significativo de S y Beijing. Estos datos aportan elementos importantes para la epidemiología y control de la TB en Cuba(AU)

Introduction: knowledge about Mycobacterium tuberculosis lineages is important to understand the origin, evolution and spread of this bacterium. Objective: determine the genetic patterns of M. tuberculosis circulating in Cuba. Methods: adescriptive cross-sectional study was conducted with an analytical component in Cuba in the period extending from January 2009 to December 2010. Spacer oligonucleotide typing (Spoligotyping) was applied to 308 M. tuberculosis isolates from the period 2009-2010. Classification into genotypes was carried out according to the international database SpolDB4. Results were additionally analyzed with the online tool MIRU-VNTRplus and compared with the M. tuberculosis genetic patterns found in Cuba in 1993-1995. Results: 79 different genotypic patterns were defined, of which 46 (62 percent) had not been previously reported in SpolDB4. The 22 clusters defined included 75.4 percent of the isolates studied. Five main genetic families were found: Beijing (25.6 percent), S (19.2 percent), LAM (16.9 percent), Haarlem (16.9 percent) and T (5.8 percent). The S family prevailed in the Western region (OR=3.4; CI 95 percent:1.8-6.3; p<0.05), Beijing in Central Cuba (OR=6.7; CI 95 percent:3.7-11.9; p<0.05), and LAM (OR=3.0; CI 95 percent:1.6-5.6; p<0.05) and Haarlem in the Eastern region (OR=1.8; CI 95 percent:1.0-3.4; p<0.05). Conclusions: great diversity was observed among the M. tuberculosis isolates circulating in Cuba in the period 2009-2010. The genetic structure of M. tuberculosis has changed in the country with the passing of time, with a reduction in endemic genotypes like Haarlem and T, and a significant increase in S and Beijing. These data contribute important information for epidemiology and TB control in Cuba(AU)

Mycobacterium tuberculosis phylogeography in the context of human migration and pathogen's pathobiology: Insights from Beijing and Ural families.

Here, I review the population structure and phylogeography of the two contrasting families of Mycobacterium tuberculosis, Beijing and Ural, in the context of strain pathobiology and human history and migration. Proprietary database (12-loci MIRU-VNTR profiles of 3067 Beijing genotype isolates) was subjected to phylogenetic and statistical analysis. The highest rate (90%) and diversity (HGI 0.80-0.95) of the Beijing genotype in North China suggest it to be its area of origin. Under VNTR-based MDS analysis the interpopulation genetic distances correlated with geography over uninterrupted landmasses. In contrast, large water distances together with long time generated remarkable outliers. Weak and less expected affinities of the distant M. tuberculosis populations may reflect hidden epidemiological links due to unknown migration. Association with drug-resistance or increased virulence/transmissibility along with particular human migration flows shape global dissemination of some Beijing clones. The paucity of data on the Ural genotype prevents from high-resolution analysis that was mainly based on the available spoligotyping data. The North/East Pontic area marked with the highest prevalence of the Ural family may have been the area of its origin and primary dispersal in Eurasia. Ural strains are not marked by increased pathogenic capacities, increased transmissibility and association with drug resistance (but most recent reports describe an alarming increase of MDR Ural strains in some parts of eastern Europe and northwestern Russia). Large-scale SNP or WGS population-based studies targeting strains from indigenous populations and, eventually, analysis of ancient DNA will better test these hypotheses. Host genetics factors likely play the most prominent role in differential dissemination of particular M. tuberculosis genotypes.

Emerging multidrug resistant Mycobacterium tuberculosis strains of the Beijing genotype circulating in Russia express a pattern of biological properties associated with enhanced virulence

The epidemiologically important Mycobacterium tuberculosis Beijing genotype strains, highly endemic in East Asia, have become an emerging infection in certain geographic areas, including Russia, because of its increasing prevalence and association with multidrug resistance (MDR). The aim was to verify whether MDR Beijing strains circulating in the emerging regions present some biological particularities that could contribute to their success in causing disease in comparison with the sporadic strains from locations with low prevalence of the Beijing genotype. We evaluated virulence-associated characteristics of the MDR Beijing strains isolated in Russia and compared them with those of the drug-resistant and susceptible Beijing strains from Brazil and reference H37Rv strain. We found that Russian MDR strains demonstrated an increased bacterial fitness and growth in THP-1 macrophage-like cells, as well as a higher capacity to induce non-protective cytokine synthesis and necrotic macrophage death. By contrast, the biological properties of the strains isolated in Brazil largely resembled those of the H37Rv strain, with the exception of the drug-resistant isolates that presented significantly reduced fitness. The data demonstrate that the emerging MDR strains of the Beijing genotype circulating in Russia do express a pattern of properties associated with the enhanced virulence favouring its clonal dissemination in this region.