12th Annual Conference of the British HIV Association 29 March–1 April 2006, Brighton, UK

APPLICATION OF AN INTERFERON-GAMMA RELEASE ASSAY TO INVESTIGATE TRANSMISSION OF MYCOBACTERIUM TUBERCULOSIS TO HIV-INFECTED PEOPLE

HIV Med 2006; 7(Suppl. 1):5 (abstract no. O20)

Ila Aggarwal¹, Graeme Meintjes¹, John Walsh², Annette Jepson², Onn Min Kon², Marcela Simsova³, Robert Wilkinson¹ and Katalin Wilkinson^1
1 Wellcome Trust Centre for Research in Clinical Tropical Medicine, Imperial College, London, ² St Mary’s NHS Trust, London, UK, ³ Institute of Microbiology of the Czech Academy of the Sciences, Prague, Czech Republic

BACKGROUND: The control of tuberculosis (TB) requires an accurate diagnostic test for latent infection. The tuberculin skin test (TST) lacks specificity and sensitivity in an HIV-infected population. Assays that measure interferon-γ (IFN-γ) production in response to the RD1-encoded M. tuberculosis antigens such as culture filtrate protein 10 (CFP-10) show evidence of improved specificity and sensitivity in HIV-uninfected people, but have rarely been evaluated in the setting of HIV.

METHODS: We aimed to assess the diagnostic value of the IFN-γ assay in the detection of latent tuberculosis among 16 HIV-infected individuals exposed to an index case of smear-positive pulmonary tuberculosis and 18 non-exposed HIV-infected controls. IFN-γ production in response to T-cell stimulation with CyaA-CFP10 (CFP-10 presented as a toxoid antigen within the inactivated adenylate cyclase of Bordetella pertussis) and PPD was measured using an ELISA. The results were correlated with the degree of exposure to the index case and results of the TST.

RESULTS: Four patients in the exposed group produced IFN-γ in response to CyaA-CFP10. This correlated with an increased duration of exposure and a strongly positive TST in one patient. In the control group, 3/5 patients with positive responses to CyaA-CFP10 may have been latently infected as they were born in high-incidence areas. Two exposed patients responded to PPD in vitro; there was no correlation with duration of exposure. A trend towards a higher CD4 count in responders was observed.

CONCLUSIONS: IFN-γ production in response to CyaA-CFP10 correlates with the degree of exposure to M. tuberculosis in an HIV-infected cohort.

2006-03-29
O20

Copyright © 2006 - British HIV Association (BHIVA) Reproduction of this abstract (other than one copy for personal reference) must be cleared through the BHIVA Organising Secretariat 1 Mountview Court, 310 Friern Barnet Lane, London N20 0LD