Method for diagnosing and differentiating HIV-2 infections

1. An in vitro method for determining whether a normalized value or a mean value of normalized values for at least one HIV-1 envelope antigen is above or below a predetermined threshold in a fluid sample obtained from a subject who is either HIV-2 positive or HIV-1/HIV-2 positive, the method comprising:

(a) contacting the fluid sample from the subject with the at least one HIV-1 envelope antigen and a control reagent that can bind human immunoglobulins, wherein said antigen and said control reagent are immobilized on distinct sites on a solid support, for a time and under conditions allowing the formation of complexes between antibodies present in the sample and (i) said at least one HIV-1 envelope antigen and (ii) said control reagent;

(b) detecting the formation of said complexes using a system generating quantifiable signal;

(c) dividing the intensity of the signal obtained for said at least one HIV-1 envelope antigen by the intensity of the signal obtained for the control reagent to obtain the normalized value for said at least one HIV-1 envelope antigen;

(d) if several HIV-1 envelope antigens are used, optionally calculating the mean value of normalized values for HIV-1 envelope antigens; and

(e) determining whether the normalized value or the mean value of the normalized values of the at least one HIV-1 envelope antigen is above or below the predetermined threshold.

2. The method according to claim 1 , wherein said at least one HIV-1 envelope antigen is selected from the group consisting of recombinant gp160, gp41 and gp120, an antigenic fragment thereof, and a peptide comprising an immunodominant epitope of gp160, gp41 or gp120.

3. The method according to claim 1 , wherein said at least one HIV-1 envelope antigen is selected from the group consisting of recombinant gp160, an antigenic fragment thereof, or a peptide comprising an immunodominant epitope of gp160.

4. The method according to claim 3 , wherein said at least one HIV-1 envelope antigen is recombinant gp160.

5. The method according to claim 3 , wherein in step (a) the fluid sample is further contacted with an HIV-1 envelope antigen selected from the group consisting of recombinant gp41, an antigenic fragment thereof, or a peptide comprising an immunodominant epitope of gp41.

6. The method according to claim 5 , wherein in step (a) the fluid sample is further contacted with a peptide comprising an immunodominant epitope of gp41.

7. The method according to claim 3 , wherein the predetermined threshold for the normalized value for gp160 antigen is about 0.3.

8. The method according to claim 7 , wherein the predetermined threshold for the normalized value for gp160 antigen is between 0.27 and 0.33.

9. The method according to claim 5 , wherein the predetermined threshold for the mean value for gp160 and gp41 antigens is about 0.6.

10. The method according to claim 9 , wherein the predetermined threshold for the mean value for gp160 and gp41 antigens is between 0.54 and 0.66.

11. The method according to claim 1 , wherein in step (a) the fluid sample is further contacted with at least one HIV-2 antigen.

12. The method according to claim 11 , wherein said at least one HIV-2 antigen is selected from the group consisting of recombinant gp36, gp105 and gp140, an antigenic fragment thereof, and a peptide comprising an immunodominant epitope of gp36, gp105 or gp140.

13. The method according to claim 1 , wherein in step (a) the fluid sample is further contacted with at least one HIV-1 core antigen and/or at least one HIV-1 pol antigen.

14. The method according to claim 1 , wherein in step (a) the fluid sample is further contacted with at least one HIV-1 antigen selected from the group consisting of recombinant p31 and p24, an antigenic fragment thereof, and a peptide comprising an immunodominant epitope of p31 or p24.

15. The method according to claim 1 , wherein the fluid sample is selected from the group consisting of whole blood, serum and plasma.

16. The method according to claim 1 , wherein the immunoassay is a migration type assay, a flow-through test, a dipstick assay or a microfluidic assay.

17. The method according to claim 16 , wherein the immunoassay is a migration type assay.

18. The method according to claim 1 , wherein the control reagent is selected from the group consisting of protein A, protein G, protein A/G, protein L and derivatives thereof, and an anti-human immunoglobulin antibody.

19. The method according to claim 18 , wherein the control reagent is protein A.

20. The method according to claim 1 , wherein in step (b) the system generating quantifiable signal is a reagent binding to human immunoglobulins, and wherein the reagent is conjugated with a detectable label.

21. The method according to claim 20 , wherein the reagent binding to human immunoglobulins is selected from the group consisting of protein A, protein G, protein A/G, protein L and derivatives thereof, and an anti-human immunoglobulin antibody.

22. The method according to claim 21 , wherein the reagent binding to human immunoglobulins is protein A.

23. The method according to claim 20 , wherein the detectable label is selected from the group consisting of colloidal metals; non-metallic colloids; carbon; visible, fluorescent, luminescent and chemiluminescent dyes; magnetic particles; radioactive elements; and enzymes.

24. The method according to claim 1 , wherein the system generating quantifiable signal is a conjugate comprising a protein selected from the group consisting of protein A, protein G, protein A/G, protein L and derivatives thereof, coupled with a colloidal metal or a fluorescent, luminescent or chemiluminescent dye.

25. The method according to claim 1 , wherein the system generating quantifiable signal is protein A conjugated with colloidal gold.

26. The method according to claim 1 , wherein the normalized level of only the at least one HIV-1 envelope antigen is determined to be above or below the predetermined threshold.