Your own genome can make your more susceptible to TB infection and recurrent TB

Your own genome can make your more susceptible to TB infection and recurrent TB

Tuberclosis(TB) being the infectious disease is communicated almost exclusively by coughed aerosols carrying pathogens of Mycobacterium tuberclosis (Mtb). As reported by World Health Organization (WHO) it causes disease in 9.6 millions people each year and ranks with human immunodeficiency virus (HIV) as a leading cause of disease. A well timed diagnosis and appropriate treatment can cure almost all infected people. It is estimated that almost one third of population is infected by Mtb, though only 5-15% infected people develop TB, and infection in rest of the 90% infected people stays in dormant stage, which is known as latent TB. This suggests the host contribution in developing TB, specially host genetic factors contributing to onset of TB. The contribution of host genetic factors in onset of TB has been shown in twin studies, which concluded that monozygotic twin have 2.5 times higher chance of developing TB compared to dizygotic twins[1].

To identify host genetic factors contributing to onset of TB genome wide association studies(GWAS) studies has been done. GWAS studies compares the difference in genetic make up of infected and non infected people and suggests which of the genetic changes can lead to a particular condition.

GWAS studies in TB can associate which of the individual with a certain genetic makeup in terms of genetic variants such as mutation can make an individual more prone to infection compared to other individuals. In a recent study done by Yosuke Omae from Department of Human Genetics in The University of Tokyo has found one such mutation in individual in Thailand (non-Beijing) population which make them more susceptible for TB infection compared to individuals not carrying that mutation. Identified mutation was found in CD53 gene which has a suggested important role in immunity also[2]. They also found higher expression of CD53 gene in active TB patients. This study also points to the information that most of these individuals carrying this particular mutation in CD53 gene belonged to reactivated TB cases of old age people.

More of such studies are needed to determine which genetic factors carried by susceptible individuals can lead to an active TB case from a latent TB case in different population. These kind of studies can reveal why a particular individual is more prone to have an active TB or having a chance of reactivated TB and hence can lead to improved care and cure of TB patients.

References : [1] Tuberculosis biomarkers: from diagnosis to protection Delia Goletti,1 Elisa Petruccioli,1 Simone A. Joosten,2 Tom H.M. Ottenhoff2. Infectious Disease Reports 2016; volume 8:6568

[2] Pathogen lineage-based genome-wide association study identified CD53 as susceptible locus in tuberculosis. Yosuke Omae of Human Genetics (2017) 62, 1015–1022

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