Digital PCR detection ofMycobacterium tuberculosisand HIV-1 co-localization in spinal tuberculosis biopsies
Abstract
Background.
The paucibacillary nature of spinal tuberculosis (STB) makes diagnosis challenging, particularly in people living with HIV-1 (PLWH). It is suggested that HIV-1 andMycobacterium tuberculosis(Mtb) co-infection in tissues favours reciprocal replication, infection and reservoir expansion. Yet, confirmation of this detrimental synergism in diseased tissues is scant.
Methods
In a prospective study of 25 adults (13 (52%) people living with HIV-1 (PLWH) on antiretroviral treatment (ART)) undergoing spinal biopsy investigation for STB in South Africa, droplet digital PCR (ddPCR) was used to detect and quantifyMtbcomplex (MTBC) DNA (rpoBandIS6110) in 93 biopsy segments, and HIV-1 DNA (polandgag) in 41 segments from PLWH. ddPCR sensitivity forMtbwas validated against Xpert-Ultra and culture. Relationships between pathogen DNA abundance, co-detection, human cellularity, HIV status, and peripheral viral load (VL) were evaluated.
Findings
ddPCR detected MTBC DNA in 19/25 (76%) patients (range: 8- 59,144rpoBcopies/biopsy), with increased detection in those with confirmed STB and a history of TB. MTBCrpoBcopies/million cells were higher in biopsies from PLWH (p=0.0096) and positively correlated with matched biopsy segment HIV-1polcopies/million cells (r=0.40; p=0.0003), but not peripheral VL. HIV-1 DNA was detected in all biopsies from PLWH, four with undetectable VL. HIV-1polcopies/million cells were higher in biopsy segments with MTBC DNA co-detected (p=0.011) and strongly correlated with VL (r=0.91; p=0.0003).
Interpretation
ddPCR has high sensitivity forMtband HIV-1 DNA quantification in STB biopsies.Mtbtissue abundance correlated with localised but not systemic HIV-1 abundance. Increased HIV-1 DNA detection at sites co-localised withMtbsupports further investigating the TB microenvironment as a site for HIV-1 reservoir persistence and expansion in PLWH on ART.
Funding
Wellcome (203135Z/16/Z); Academy of Science of SA (ASSAf); ORU, UCT; UCT Merit Award.
Contacts
Anna Coussens, Walter and Eliza Hall Institute of Medical Research (WEHI), 1G Royal Parade, Parkville, 3052, Australia; Tel: +61 3 39452699; Email:<email>coussens.a@wehi.edu.au</email>Robyn Waters, Division of Orthopaedic Surgery, University of Cape Town, Anzio Rd, Observatory, 7925, South Africa; Email:<email>robyn.waters@uct.ac.za</email>
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