title: Serum antibodies against native and denaturated hemagglutinin glycoproteins detected by ELISA as correlates of protection after influenza vaccination in healthy vaccinees and in kidney transplant recipients.
abstract: The microneutralization assay is the standard method to investigate immune responses to influenza vaccination. However there remains some uncertainty as to whether ELISA results are a true measure of immunity in healthy or immuno-compromised vaccines. Furthermore it has been questioned if antibodies against native ("folded") and against denaturated ("unfolded") viral glycoproteins can equally be used as a marker of protection. In this study, two different quantitative IgG-ELISA assays detecting (i) antibodies against unfolded recombinant hemagglutinin (HA) (r-ELISA) and (ii) antibodies against the native HA on the influenza virus surface captured by fetuin-linkage (f-ELISA) were compared to microneutralization titers in sera from 29 healthy vaccinees (n=87 sera) and 39 kidney transplant recipients (n=117 sera) collected before, three weeks after and six months after vaccination against influenza A (H1N1) 2009. With both ELISAs a significant increase in antibody levels was detected after vaccination and linear regression analysis demonstrated that r-ELISA and f-ELISA correlated with microneutralization (R=0.622 for r-ELISA vs. R=0.56 for f-ELISA). For the healthy vaccinees both ELISAs were found to be adequate to distinguish protected from non-protected individuals (sensitivity and specificity: 87.5%/85.3% for r-ELISA and 87.5%/88.3% for f-ELISA). Results from the transplant recipients showed a slightly reduced sensitivity of 73.3% for r-ELISA while the f-ELISA demonstrated similar sensitivity and specificity as in the healthy vaccinees. However, in order to obtain these assay performances the cut-off-values for protection had to be adjusted for both assays and both investigation cohorts respectively limiting their application in routine laboratories.
authors.affiliation: University of Düsseldorf, Medical Faculty, Institute for Virology, D-40225 Düsseldorf, Germany. Electronic address: sebastian.grund@med.uni-duesseldorf.de.
authors.forename: S
authors.initials: S
authors.lastname: Grund
authors.forename: S
authors.initials: S
authors.lastname: Pietzonka
authors.forename: S
authors.initials: S
authors.lastname: Michel
authors.forename: O
authors.initials: O
authors.lastname: Adams
mesh_terms: D000328:Adult; D000368:Aged; D000914:Antibodies, Viral / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D064368:Healthy Volunteers; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D007251:Influenza, Human / Q000276:immunology / Q000517:prevention & control*; D016030:Kidney Transplantation; D008297:Male; D008875:Middle Aged; D011489:Protein Denaturation; D012680:Sensitivity and Specificity; D014180:Transplantation
chemical_list: D000914:Antibodies, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007074:Immunoglobulin G; D007252:Influenza Vaccines
keywords: ELISA; Influenza virus; Kidney transplant recipients; Neutralization assay; Vaccination