Detection of antibodies against H5 and H7 strains in birds: evaluation of influenza pseudovirus particle neutralization tests.
BACKGROUND
Avian influenza viruses circulate in bird populations, and it is important to maintain and uphold our knowledge of the viral strains that are currently of interest in this context. Here, we describe the use of hemagglutinin-pseudotype retroviruses based on highly pathogenic influenza viruses for the screening of avian sera for influenza A antibodies. Our aim was also to determine whether the pseudovirus neutralization tests that we assessed were sensitive and simple to use compared to the traditional methods, including hemagglutination inhibition assays and microneutralization tests.


METHODS
H5 and H7 pseudovirus neutralization tests were evaluated by using serum from infected rabbits. Subsequently, the assays were further investigated using a panel of serum samples from avian species. The panel contained samples that were seropositive for five different hemagglutinin subtypes as well as influenza A seronegative samples.


CONCLUSIONS
The results suggest that the pseudovirus neutralization test is an alternative to hemagglutination inhibition assays, as we observed comparable titers to those of both standard microneutralizations assays as well as hemagglutinin inhibition assays. When evaluated by a panel of avian sera, the method also showed its capability to recognize antibodies directed toward low-pathogenic H5 and H7. Hence, we conclude that it is possible to use pseudoviruses based on highly pathogenic avian influenza viruses to screen avian sera for antibodies directed against influenza A subtypes H5 and H7.
Karolinska Institutet, Department of Microbiology, Tumor and Cell Biology, Stockholm, Sweden ; Swedish Institute for Communicable Disease Control, Department of Diagnostics and Vaccinology, Solna, Sweden.
Sofie
S
Wallerström
Karolinska Institutet, Department of Microbiology, Tumor and Cell Biology, Stockholm, Sweden ; Swedish Institute for Communicable Disease Control, Department of Diagnostics and Vaccinology, Solna, Sweden.
Nina
N
Lagerqvist
Viral Pseudotype Unit, University of Kent, Kent, UK.
Nigel J
NJ
Temperton
Swedish Institute for Communicable Disease Control, Department of Diagnostics and Vaccinology, Solna, Sweden.
Michaela
M
Cassmer
Reparto di Virologia, Istituto Zooprofilattico Sperimentale della Lombardia ed Emilia Romagna, Brescia, Italy.
Ana
A
Moreno
Swedish Institute for Communicable Disease Control, Department of Diagnostics and Vaccinology, Solna, Sweden.
Malin
M
Karlsson
National Veterinary Institute, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Mikael
M
Leijon
Karolinska Institutet, Department of Microbiology, Tumor and Cell Biology, Stockholm, Sweden ; Swedish Institute for Communicable Disease Control, Department of Diagnostics and Vaccinology, Solna, Sweden ; Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
Ake
A
Lundkvist
Karolinska Institutet, Department of Microbiology, Tumor and Cell Biology, Stockholm, Sweden ; Swedish Institute for Communicable Disease Control, Department of Diagnostics and Vaccinology, Solna, Sweden.
Kerstin I
KI
Falk
antibodies; avian; influenza A; neutralization; pseudovirus