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Updated: Jun 19, 2026
Optimization of a Quantitative Micro-neutralization Assay
Published on: December 14, 2016
Defective particles can lead to underestimated antibody titers in virus neutralization tests
Wiebke Handke1, Detlev H Krüger, Andreas Rang
1Institute of Virology, University Hospital Charité, Berlin, Germany.
Objective:
Stocks of RNA viruses often contain divergent mixtures of infectious and defective particles (DPs). Since the surface of both particles share the same immunoreactivity, differing ratios of these particles in stocks used for virus neutralization tests might alter the results. Here the impact of such off-target effects were measured.
Methods:
To determine the relative content of DPs in 3 stocks with high, medium and low titers of infectious virions, the amounts of nucleocapsid protein and viral RNA were quantified by Western blot and quantitative RT-PCR. Thereafter, stocks with different amount of DPs were used to determine the titer of neutralizing antibodies in serum from a convalescent Puumala virus-infected patient by a focus reduction neutralization test.
Results:
The relative amount of DPs was at least 5-fold higher in the stock with the lowest titer compared to the stock with the highest. Stocks with lower levels of DPs led to higher antibody titers compared to the analysis performed with stocks containing higher levels of DPs.
Conclusion:
These results imply that DPs in virus stocks should be considered when performing virus neutralization tests to quantify neutralizing antibodies.
