Clinical evaluation of the host gene signature for tuberculosis diagnosis and treatment response monitoring

Nakiboneka, Ritah

Clinical evaluation of the host gene signature for tuberculosis diagnosis and treatment response monitoring

Date

2021-09-15

Authors

Nakiboneka, Ritah

Publisher

Kamuzu University of Health Sciences

Abstract

This study will be a cross-sectional case-control study, accompanied by a prospective longitudinal follow-up study of patients with Xpert MTB/RIF (Xpert) confirmed active pulmonary TB. Eligible participants will be adults aged 18 years, belonging to the following groups: i) Presumptive TB cases or confirmed TB patients, these will include: • Active TB patients with confirmed TB disease (Group 1-Xpert positive) • Clinically diagnosed patients being started on TB treatment (Group 2- Xpert MTB/RIF negative) • Individuals with cough or respiratory symptoms (Group 3 - XpertMTB/RIF negative, QuantiFERON negative and not started on TB treatment) ii) Apparently Healthy individuals, these will include: • LTBI (Group 4 - QuantiFERON positive, having no clinical signs of TB) • Healthy volunteers (Group 5 - QuantiFERON test negative and no underlying medical conditions) Participants with positive Xpert MTB/RIF test without rifampicin resistance, will be placed on therapy and followed in a longtudinal study for 9 months to monitor treatment response success. These patients will be assessed at 2 weeks, and months 4, 6, and 9. At each visit blood will be collected (host gene response test) and sputum (culture, TB MBLA assay). Drug resistant TB cases and those unable to come back for follow-up visits will be excluded. The problem [to be studied]: Tuberculosis (TB) is a global health problem with a quarter of the world’s population infected with Mycobacterium tuberculosis (MTB). The current diagnostic tests for ATB are focused on detection of MTB bacilli within sputum samples and are thus not useful for diagnosing LTBI. Similarly, the immunological tests- although approved for use by the USA Food and Drug Administration (FDA) as diagnostic tests for LTBI, are not approved for ATB, and cannot differentiate between ongoing or resolved disease from either LTBI or ATB. These challenges led the WHO to call for the development of new non-sputum triage tests for TB diagnosis. These tests should detect latently infected individuals before they progress to active disease and no sputum conversion has occurred. They should detect TB in children and immunocompromised individuals who cannot produce sputum, should detect disseminated/extrapulmonary TB, and lastly, should be usable in monitoring therapy response. TB infection elicits specific gene expression in the human host to suppress or eliminate the infection. These genes can be detected in blood with over 80% specificity and sensitivity to TB disease. However, none of the gene sets has been adopted as a simple point of care diagnostic test in a clinical setting. Designing a simple gene diagnostic test and using it to diagnose TB infection will improve both diagnosis and therapy monitoring in TB disease. The objective: To clinically evaluate the accuracy of the host gene signature for diagnosis of TB and monitoring response to anti-TB therapy over the course of treatment. Methodology: Both male and female consenting adults will be enrolled into this study. A total of 266 participants will be recruited to the case-control study. Participant recruitment and treatment follow-up will be done from Blantyre, Malawi. Individuals seeking care at Queen Elizabeth Central Hospital and three health centres in Blantyre (Bangwe, Limbe, Ndirande), will be informed about the study. Those who show interest to join the study will be consented. The study will also be advertised through word of mouth to apparently - healthy participants in the Blantyre community and in HIV testing centers. Those who express interest will be invited to come to the hospital to learn more, and consider signing informed consent forms. This will be the break down of participants in each group: 116 individuals with active PTB (Group 1 and 2), 50 TB negative cases having respiratory symptoms (Group 3), 50 individuals with latent TB (Group 4), and lastly 50 healthy controls (Group 5). After consenting to join the study, 9 mL of blood will be drawn from each participant. Presumptive TB cases will also be asked to offer a sputum sample. Blood and sputum samples will be processed from Blantyre laboratory for detection of the host signature and Mycobacteria tuberulosis bacilli respectively. Expected findings and their dissemination: Upon completion of the project, Sensitivity, Specificity, Positive predictive value, and Negative predictive value of the host gene signature at detecting TB in: culture confirmed actively infected TB cases, Xpert MTB/RIF confirmed ATB cases and in latently infected individuals will be described. Treatment response monitoring by the gene sets will also be described by change in Cq values from baseline signifying change in gene expression as patient bacterial burden reduces due to therapy. This change will be compared to TB-MBLA measured sputum bacterial load. Results from this study will be analysed and published in a PhD manuscript, and in a research publication in an anonymised form. Results and data from this study may also be shared on a database accessible by other researchers but only in an anonymised form. Results from this study will also be presented in scientific meetings in an anonymised form.