Complement factor H-based assays for serum bactericidal activity against
Assays for detection of bactericidal anti-Neisserial antibodies using a factor H polypeptide having a human amino acid sequence that mediates binding to Neisserial factor H binding protein (fHBp) are provided, as well as non-human animal models of Neisserial infection.
1. A method of detection of bactericidal antibodies specific to Neisseria meningitidis in a biological sample, the method comprising:
combining in a reaction mixture:
viable Neisseria meningitidis expressing a surface factor H binding protein (fHbp);
a biological sample from a human suspected of containing bactericidal antibodies specific to Neisseria meningitidis,
a substantially purified factor H (fH) polypeptide comprising the amino acid sequence of a human Short Consensus Repeat 6 (SCR 6); and
a complement of a non-human animal having no detectable anti- Neisseria meningitidis bactericidal activity; and
detecting the presence or the absence of the bactericidal antibodies specific to the Neisseria meningitidis in the sample by assessing viability of the Neisseria meningitidis,
wherein decreased viability of the Neisseria meningitidis in the presence of the sample indicates that the sample contains the bactericidal antibodies specific to the Neisseria meningitidis.
2. The method of claim 1 , wherein the bactericidal antibodies specific to the Neisseria meningitidis in the biological sample are antibodies to the capsular polysaccharide of the Neisseria meningitidis and the biological sample is human serum.
3. The method of claim 1 , wherein the substantially purified fH polypeptide is a human fH polypeptide.
4. The method of claim 1 , wherein the substantially purified fH polypeptide is a chimeric fH polypeptide comprising the amino acid sequence of an fH polypeptide endogenous to the non-human animal modified to contain the amino acid sequence of the human SCR6.
5. The method of claim 1 , wherein the non-human complement is rabbit complement.
6. The method of claim 1 , wherein the non-human complement is rat complement or mouse complement.
7. The method of claim 1 , wherein the Neisseria meningitidis is a Group A, B, C, X, Y or W-135 Neisseria meningitidis.
8. The method of claim 1 , wherein the sample is human serum.
9. The method of claim 1 , wherein the substantially purified fH polypeptide is added to the reaction mixture in an amount of 5 μg/ml or more.
10. The method of claim 1 , wherein the substantially purified fH polypeptide is added to the reaction mixture in an amount of 10 μg/ml or more.
11. The method of claim 1 , wherein the substantially purified fH polypeptide is added to the reaction mixture in an amount of 20 μg/ml or more.
12. The method of claim 1 , wherein the substantially purified fH polypeptide is added to the reaction mixture in an amount of 50 μg/ml or more.
13. The method of claim 3 , wherein the substantially purified fH polypeptide is added to the reaction mixture in an amount of 5 μg/ml or more.
14. The method of claim 3 , wherein the substantially purified fH polypeptide is added to the reaction mixture in an amount of 10 μg/ml or more.
15. The method of claim 3 , wherein the substantially purified fH polypeptide is added to the reaction mixture in an amount of 20 μg/ml or more.
16. The method of claim 3 , wherein the substantially purified fH polypeptide is added to the reaction mixture in an amount of 50 μg/ml or more.
17. The method of claim 5 , wherein the substantially purified fH polypeptide is added to the reaction mixture in an amount of 5 μg/ml or more.
18. The method of claim 5 , wherein the substantially purified fH polypeptide is added to the reaction mixture in an amount of 10 μg/ml or more.
19. The method of claim 5 , wherein the substantially purified fH polypeptide is added to the reaction mixture in an amount of 20 μg/ml or more.
20. The method of claim 5 , wherein the substantially purified fH polypeptide is added to the reaction mixture in an amount of 50 μg/ml or more.