Skin testing for tuberculosis in immunocompromised persons

Abstract

Disclosed herein is the use of Mycobacterium tuberculosis antigens for use in in vivo determination of the presence of Mtb infection in immunocompromised persons or persons co-infected with HIV and the for preparing a diagnostic reagent for skin testing (a skin test reagent) for robust assessment of the presence of Mtb infection infection in an individual wherein the individual is an immunocompromised person or a person co-infected with HIV.

Claims

1. A method of eliciting an immune response in an immunocompromised subject having a latent M. tuberculosis (Mtb) infection and showing no symptoms characteristic of an active Mtb infection which comprises administering intradermally to the immunocompromised subject a cocktail comprising an ESAT6 Mtb antigen and a CFP-10 Mtb antigen.

2. The method according to claim 1, which further comprises measuring a diameter of any induration resulting from the administration to measure the magnitude of the immune response.

3. The method according to claim 1, wherein the ESAT6 Mtb antigen or both the ESAT6 Mtb and CFP-10 antigens are cloned, produced, and purified from Lactococcus lactis.

4. The method according to claim 1, wherein the cocktail further comprises a pharmaceutically acceptable carrier.

5. The method according to claim 1, wherein the cocktail further comprises phosphate buffered saline (PBS) with 0.01% polyoxyethylene (20) sorbitan monolaurate and 0.5% phenol.

6. The method according to claim 1, wherein the cocktail comprises recombinant double-ESAT6 Mtb antigen and recombinant CFP-10 Mtb antigen.

7. The method according to claim 6, wherein the recombinant double-ESAT6 and recombinant CFP-10 are present in a 1:1 (w/w) ratio.

8. The method according to claim 6, wherein the recombinant double-ESAT6 and recombinant CFP-10 are present in a ratio between 1:20 (w/w) and 20:1 (w/w).

9. The method according to claim 1, wherein the cocktail comprises a total amount of Mtb antigens ESAT6 antigen and CFP-10 Mtb antigen of an amount of 0.25-2.0 g/mL of the Mtb antigens ESAT6 antigen and CFP-10 Mtb antigen.

10. The method according to claim 2, wherein the diameter of the induration is measured between 48-72 hours after administration of said cocktail.

11. The method according to claim 1, wherein the cocktail further comprises one or more Mtb antigens in addition to the ESAT6 and CFP-10 Mtb antigens.

12. The method according to claim 11, wherein the one or more Mtb antigens are selected from the group consisting of RD1 restricted antigens, RD1 associated antigens, Rv2564, Rv3865, Rv3877, Rv2348, Rv3614, Rv3615, and Rv3616.

13. The method according to claim 1, wherein the immunocompromised subject is a child.

14. The method according to claim 1, wherein the immunocompromised subject is an adult.

15. The method according to claim 1, wherein the immunocompromised subject is infected with HIV.

16. The method according to claim 1, wherein the immunocompromised subject is suspected of having an Mtb infection.

17. The method according to claim 1, wherein the immunocompromised subject is suspected of having TB disease.

18. A method of performing a skin test on an immunocompromised subject showing no symptoms characteristic of an active Mtb infection which comprises administering intradermally to the immunocompromised subject a cocktail of Mtb antigens, said Mtb antigens consisting of an ESAT6 Mtb antigen and a CFP-10 Mtb antigen, and detecting any skin reaction by measuring a diameter of any induration resulting from the cocktail of Mtb antigens.

19. The method according to claim 18, wherein the immunocompromised subject is infected with HIV.

20. The method according to claim 18, wherein the immunocompromised subject is suspected of having an Mtb infection.

Description

FIGURE LEGENDS

(1) FIG. 1. Positivity rate of C-Tb (black; cut-off 5 mm) and QFT (white; cut-off 0.35 IU/mL) among 534 HIV negative and 277 HIV positive TB suspects. Error bar indicate 95% CI.

(2) FIG. 2. Positivity rate of C-Tb (black) and QFT (white) stratified according to CD4 count among 292 TB suspects. Error bar indicate 95% CI.

EXAMPLES

(3) The diagnostic agent C-Tb was prepared by cloning, fermenting and purifying recombinant versions of the two antigens rdESAT-6 and rCFP-10 from Lactococcus lactis. The antigens were mixed in equimolar amounts of ESAT-6 and CFP-10 corresponding to a 1:1 w/w ratio of rdESAT-6 and rCFP-10 in a vehicle of phosphate buffered saline (PBS) with 0.01% Polysorbate 20 (and 0.5% phenol)

(4) The diagnostic performance of C-Tb, PPD and an IGRA named QuantiFERON-TB Gold In Tube (QFT) were compared in a phase III trial in infants and children less than 5 years of age with suspected Mtb infection, and in older children and adults with suspected TB disease. The trial of 1190 participant included 299 HIV positives and 730 HIV negatives. Blood for QFT testing was collected prior to skin testing. CTb and PPD were injected double blind into separate arms in a randomized, split body design. Results from the volunteers with paired results available were included.

(5) As evident from FIG. 1, CTb and QFT showed the same positivity rate among HIV negatives, 292/534 (54.7%) were positive with C-Tb and 285/534 (53.4%) were positive with QFT. A total of 277 HIV infected individuals were tested with both tests. Surprisingly C-Tb disclosed significantly more Mtb infected than the QFT test, 102/277 (36.8%) tested positive with C-Tb and only 80/277 (28.9%) tested positive with QFT, (table 1, McNemar; P=0.009).

(6) TABLE-US-00001 TABLE 1 QFT HIV pos + S C-Tb + 59 43 102 21 154 175 S 80 197 277 P = 0.009

(7) When stratifying rest results by CD4 T cell count (FIG. 2), it becomes evident that the higher sensitivity by C-Tb stems from a significantly increased robustness not only in the low CD4 T cell strata but across the whole spectrum of CD4 T cell counts.