The Hemagglutination Assay (HA) is a quantification of viruses or bacteria by hemagglutination.
Some viral families and all bacteria have surface or envelope proteins, that are able to agglutinate (stick to) human or animal Red blood cells (RBC) and bind to its N-acetylneuraminic acid. The RBC will form a type of lattice in this case.
The HA of a virus, in contrast to Plaque assay or LD50, does not give any measure of viral infectivity, because no virus replication is required in this assay.
The same may not be true when using HA for bacteria.
It is an easy, simple and rapid method and can be applied to large amounts of samples.
The detailed conditions depend on the type of virus or bacteria being assayed since certain pH values and ionic strengths can impact the activity of the proteins of interest in a difficult to predict manner.
Normally, a virus dilution (eg. 2-fold from 1:4 to 1:4096) will be applied to an RBC dilution (eg. 0.1% to 0.7% in steps of 0.2%) for approx. 30 min, often at 4C, otherwise viruses with neuraminidase activity will detach the virus from the RBCs. Then the lattice forming parts will be counted and the titre calculated.
Virus concentration in virions per milliliter = 107 x HA titer.[1]
For bacteria, depending on species, a bacterial dilution will be applied to an equal part RBC dilution and then incubated for 30 min to an hour at an optimal growth temperature before being observed.[2]
See also
References
- ^ Donald HB, Isaacs A (1954). "Counts of influenza virus particles". J. Gen. Microbiol. 10 (3): 457–64. PMID 13174769.
- ^ X. Chen , et al. (2007). "The S-Layer Proteins of L. crispatus strain ZJ001 is responsible for competitive exclusion against E. coli O157:h7 and S. typhimurim". Int. J. Food Microbiology 115 (3): 307-312. doi:. PMID 17289201.
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