Influenza viruses are the causative agents of outbreaks of acute respiratory diseases, called “flu”. The virus was isolated for the first time in 1933 and belong to the group of Orthomyxoviridae.
This group can be split up in 2 groups, one containing influenza A+B and the other influenza C.
These influenza viruses can be distinguished on the basis of antigenic differences on their Nuclear Proteins (NPs), and also on matrix protein M.
Influenza A can be further divided into subtypes based on antigenic differences in their surface proteins H (=haemaglutinine) an N (=neuramidase). Up to 16 different H (H1-16) and 9 different N (N1-9) types have been identified.
The Influenza virus has a spherical shape and a size of 80-120 nm. On the envelop it carriers two major proteins H and N, rod and mushroom shaped proteins respectively.
The virus is covered with approximately 500 H spikes and approx 100 N spikes per particle.
Influenza A Virus infects a wide range of animal species, including humans, pigs, dogs, cats and aquatic birds (ducks, swans, geese, etc.).
Up to now only H1, H2, H3 and incidentally H5 and H9 have been found in humans, H1 and H3 have been found in pigs and H3 and H7 in horses. In contrast, all known H subtypes are found in aquatic birds especially in ducks, which are considered to be the natural reservoir of influenza A.
This means that Influenza A Virus crosses species barriers and can be transmitted from one species to an other either directly or indirectly through an intermediate host.
The ongoing spread of avian influenza A viruses of the H5N1 subtype in Asia, Western Europe and Africa is of great concern and therefore rapid and reliable diagnostic is needed. This One-Step detects Influenza Virus type A antigen in throat swab material or tissue-culture samples. For diagnosis of influenza virus (IV) type A the demonstration of circulating influenza virus antigen is the most commonly used method. Possible false-negative results, caused by natural occurring variants of the virus, have been minimized in this assay, since two monoclonal antibodies directed against two different, well conserved, epitopes of NP (Nucleoprotein) were used in this assay. Possible false positive results can be caused by E. coli in faecal matter and is therefore not recommended to be used in this assay.
Principle Of The Test
The Influenza antigen One-Step is based on a chromatographic principle in which two monoclonal antibodies react with two different, well conserved, epitopes of Influenza Virus type A Nuclear Protein (NP). One monoclonal antibody is conjugated to colloidal gold particles and the other monoclonal antibody is immobilized on the test strip in the test zone “T”. Influenza Virus type A antigen, in the sample that is applied to the test strip at the sample zone “S”, will bind to the colloidal gold particles which then migrate to zone ”T”. A colour change in zone “T” indicates a positive test. Influenza Virus type A antigen is also immobilized on the test strip in the control zone “C”, which binds the colloidal gold particles to indicate that the test is working properly.