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Vaccine. 2016 Jan 20;34(4):458-465. doi: 10.1016/j.vaccine.2015.12.022. Epub 2015 Dec 18.

Comparability of neuraminidase inhibition antibody titers measured by enzyme-linked lectin assay (ELLA) for the analysis of influenza vaccine immunogenicity.

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Division of Viral Products, CBER, Food and Drug Administration, Silver Spring, MD, USA. Electronic address:
Division of Viral Products, CBER, Food and Drug Administration, Silver Spring, MD, USA.
BARDA, Department of Health and Human Services, Washington, DC, USA.
Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA, USA.
Paul Ehrlich Institute, Langen, Germany.
Public Health England, London, United Kingdom.
WHO Collaborating Center, Melbourne, Australia.
WHO Collaborating Center, National Institute for Viral Disease Control and Prevention, Beijing, China.
National Institute for Biological Standards and Control, Medicines and Healthcare Products Regulatory Agency, Potters Bar, United Kingdom.
Formerly National Institute for Biological Standards and Control, United Kingdom.


Neuraminidase-inhibition (NI) antibody titers can be used to evaluate the immunogenicity of inactivated influenza vaccines and have provided evidence of serologic cross-reactivity between seasonal and pandemic H1N1 viruses. The traditional thiobarbituric acid assay is impractical for large serologic analyses, and therefore many laboratories use an enzyme-linked lectin assay (ELLA) to determine serum NI antibody titers. The comparability of ELLA NI antibody titers when measured in different laboratories was unknown. Here we report a study conducted through the Consortium for the Standardisation of Influenza SeroEpidemiology (CONSISE) to evaluate the variability of the ELLA. NI antibody titers of a set of 12 samples were measured against both N1 and N2 neuraminidase antigens in 3 independent assays by each of 23 laboratories. For a sample repeated in the same assay, ≥96% of N1 and N2 assays had less than a 4-fold difference in titer. Comparison of the titers measured in assays conducted on 3 different days in the same laboratory showed that a four-fold difference in titer was uncommon. Titers of the same sera measured in different laboratories spanned 3 to 6 two-fold dilutions (i.e., 8-64 fold difference in titer), with an average percent geometric coefficient of variation (%GCV) of 112 and 82% against N1 and N2 antigens, respectively. The difference in titer as indicated by fold range and %GCV was improved by normalizing the NI titers to a standard that was included in each assay. This study identified background signal and the amount of antigen in the assay as critical factors that influence titer, providing important information toward development of a consensus ELLA protocol.


Assay; CONSISE; ELLA; Influenza; Neuraminidase; Variability

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