Serial Interferon-Gamma Release Assay (IGRA) Testing to Monitor Treatment Responses in Cases of Feline Mycobacteriosis.

Jordan L Mitchell,Jayne C Hope,Paul Burr,Conor O’Halloran,Danièlle A Gunn-Moore,Kieran Mcdonald,Paul Stanley

doi:10.3390/pathogens10060657

Jordan L Mitchell, Jayne C Hope + Show 5 more

Open Access

https://doi.org/10.3390/pathogens10060657

Copy DOI

Journal: Pathogens	Publication Date: May 26, 2021
Citations: 1	License type: CC BY 4.0

Affiliation: Roslin Institute, University of Edinburgh

Abstract

The interferon-gamma release assay (IGRA) is used to diagnose cases of feline mycobacteriosis, but the use of serial testing to monitor treatment responses has not been evaluated in this species. From a population of cats that underwent IGRA testing for diagnostic investigation, individuals were identified with a pre- and end-of-treatment IGRA that passed control thresholds. The number of cats which reverted to negative at the end-of-treatment IGRA, changes in paired antigen-specific optical density (OD) values and differences in the pre-treatment antigen-specific OD values for those which underwent reversion were compared. Factors to explain reversion or recurrence of disease post-treatment were explored. Four of 18 cats (22%) reverted to negativity at the point of clinical resolution (p = 0.33), there was no difference in paired antigen-specific OD values (p ≥ 0.12), and cats that reverted did not have a lower baseline OD value (p = 0.63). No statistically significant factors were identified to predict reversion (p ≥ 0.08). Remaining positive at the end of treatment IGRA was not associated with recurrence of disease post-treatment (p = 0.34). Overall, these data suggest there is limited value in the use of the IGRA to monitor treatment responses in cats.

Highlights

Mycobacteriosis is a substantial issue within the domestic cat population in Great Britain, with an estimated 1% of all routine feline biopsy submissions showing changes suggestive of mycobacterial disease [1]; many cases may not initially be recognised by practitioners
Of the 56 cats that did not pass these criteria: 49 were excluded as they did not meet the conditions for a passing optical density (OD) positive control (PC) and/or positive control–negative control (NC) OD values, four had coefficient of variation (CV) values exceeding 30% for at least one test condition, and three had average ODNC values greater than 0.30
Active mycobacterial disease was diagnosed in 36 of the 51 cats with at least two tests meeting the interferon-gamma (IFNγ) release assay (IGRA) inclusion criteria, and of these 18 were included for final analysis as they did not have a previous history of being treated for mycobacterial disease

Summary

Introduction

Mycobacteriosis is a substantial issue within the domestic cat population in Great Britain, with an estimated 1% of all routine feline biopsy submissions showing changes suggestive of mycobacterial disease [1]; many cases may not initially be recognised by practitioners. Established for diagnosing tuberculosis (TB) in cattle where tuberculin skin testing failed to identify all infected animals [3], the IGRA has since been adapted for the diagnosis of TB in other species [4,5], including cats [6]. These assays detect the cellular immune response through secretion of IFNγ by T-cells following stimulation with mycobacterial antigens [7]. While the IGRA appears useful for diagnosing mycobacteriosis in cats, its clinical utility for monitoring the response to treatment in this species is unknown

Objectives

Methods

Results

Conclusion