Hemagglutinins recognize
cell-surfaceglycoconjugates containing
sialic acid on the surface of host
red blood cells with a low affinity and use them to enter the
endosome of host cells.[4] In the endosome, hemagglutinins are activated at a
pH of 5–6.5 to undergo conformational changes that enable viral attachment through a fusion
peptide.[5]
Hemagglutinins are small proteins that extend from the surface of the virus membrane as spikes that are 135 Angstroms (Å) in length and 30-50 Å in diameter..[14] Each spike is composed of three identical
monomer subunits, forming the protein a
homotrimer. These monomers are formed of two
glycopeptides, HA1 and HA2, and linked by two
disulphidepolypeptides, including membrane-distal HA1 and the smaller membrane-proximal HA2.
X-ray crystallography and
spectroscopy were used to identify that the majority of the protein structures is made of
α-helical proteins.[15] In addition to the homotrimeric core structure, hemagglutinins have four subdomains: the membrane-distal receptor binding R subdomain, the vestigial domain E, that functions as a receptor-destroying
esterase, the fusion domain F, and the membrane anchor subdomain M. The membrane anchor subdomain forms elastic protein chains linking the hemagglutinin to the
ectodomain.[16]
Uses in serology
Hemagglutination Inhibition Assay:[17] A serologic assay which can be used either to screen for antibodies using
RBCs with known surface
antigens, or to identify RBCs surface antigens such as viruses or bacteria using a panel of known antibodies. This method, performed first by
George K. Hirst in 1942, consists of mixing virus samples with serum dilutions so that antibodies bind to the virus before RBCs are added to the mix. Consequently, those viruses bound to antibodies are unable to link RBCs, meaning that a test’s positive result due to
hemagglutination has been inhibited. On the contrary, if hemagglutination occurs, the test will result negative.
A schematic diagram of the experimental setup to detect
hemagglutination for blood typing.
Hemagglutination blood typing detection:[18] This method consists of measuring the blood’s reflectance spectrum alone (non-agglutination), and that of blood mixed with antibody reagents (agglutination) using a waveguide-mode sensor. As a result, some differences in reflectance between the samples are observed. Once antibodies are added,
blood types and
Rh(D) typing can be determined using the waveguide-mode sensor. This technique is able to detect weak agglutinations that are almost impossible to detect with the human eye.
ABOblood group determination: Using anti-A and anti-B antibodies that bind specifically to either the A or to the B blood group surface antigens on
RBCs, it is possible to test a small sample of blood and determine the ABO blood type of an individual. It does not identify the
Rh(D) antigen (
Rh blood type).
The bedside card method of blood grouping relies on visual agglutination to determine an individual's blood group. The card contains dried blood group antibody
reagents fixed onto its surface. A drop of the individual's blood is placed on each blood group area on the card. The presence or absence of flocculation (visual agglutination) enables a quick and convenient method of determining the
ABO and
Rhesus status of the individual. As this technique depends on human eyes, it is less reliable than the blood typing based on waveguide-mode sensors.
In the case of red blood cells, transformed cells are known as
kodecytes. Kode technology exposes exogenous antigens on the surface of cells, allowing antibody-antigen responses to be detected by the traditional hemagglutination test.[20]
^Couch, Robert B. (1996), Baron, Samuel (ed.),
"Orthomyxoviruses", Medical Microbiology (4th ed.), Galveston (TX): University of Texas Medical Branch at Galveston,
ISBN978-0-9631172-1-2,
PMID21413353, retrieved 30 January 2024
^Donald J. Benton, Andrea Nans, Lesley J. Calder, Jack Turner, Ursula Neu, Yi Pu Lin, Esther Ketelaars, Nicole L. Kallewaard, Davide Corti, Antonio Lanzavecchia, Steven J. Gamblin, Peter B. Rosenthal, John J. Skehel (2 October 2018) [Sep 17, 2018].
"Hemagglutinin membrane anchor". Proceedings of the National Academy of Sciences of the United States of America. 115 (40): 10112–10117.
doi:10.1073/pnas.1810927115.
PMC6176637.
PMID30224494.{{
cite journal}}: CS1 maint: multiple names: authors list (
link)
^Theis, Samuel R.; Hashmi, Muhammad F. (2022),
"Coombs Test", StatPearls, Treasure Island (FL): StatPearls Publishing,
PMID31613487, retrieved 16 December 2022
Hemagglutinins recognize
cell-surfaceglycoconjugates containing
sialic acid on the surface of host
red blood cells with a low affinity and use them to enter the
endosome of host cells.[4] In the endosome, hemagglutinins are activated at a
pH of 5–6.5 to undergo conformational changes that enable viral attachment through a fusion
peptide.[5]
Hemagglutinins are small proteins that extend from the surface of the virus membrane as spikes that are 135 Angstroms (Å) in length and 30-50 Å in diameter..[14] Each spike is composed of three identical
monomer subunits, forming the protein a
homotrimer. These monomers are formed of two
glycopeptides, HA1 and HA2, and linked by two
disulphidepolypeptides, including membrane-distal HA1 and the smaller membrane-proximal HA2.
X-ray crystallography and
spectroscopy were used to identify that the majority of the protein structures is made of
α-helical proteins.[15] In addition to the homotrimeric core structure, hemagglutinins have four subdomains: the membrane-distal receptor binding R subdomain, the vestigial domain E, that functions as a receptor-destroying
esterase, the fusion domain F, and the membrane anchor subdomain M. The membrane anchor subdomain forms elastic protein chains linking the hemagglutinin to the
ectodomain.[16]
Uses in serology
Hemagglutination Inhibition Assay:[17] A serologic assay which can be used either to screen for antibodies using
RBCs with known surface
antigens, or to identify RBCs surface antigens such as viruses or bacteria using a panel of known antibodies. This method, performed first by
George K. Hirst in 1942, consists of mixing virus samples with serum dilutions so that antibodies bind to the virus before RBCs are added to the mix. Consequently, those viruses bound to antibodies are unable to link RBCs, meaning that a test’s positive result due to
hemagglutination has been inhibited. On the contrary, if hemagglutination occurs, the test will result negative.
A schematic diagram of the experimental setup to detect
hemagglutination for blood typing.
Hemagglutination blood typing detection:[18] This method consists of measuring the blood’s reflectance spectrum alone (non-agglutination), and that of blood mixed with antibody reagents (agglutination) using a waveguide-mode sensor. As a result, some differences in reflectance between the samples are observed. Once antibodies are added,
blood types and
Rh(D) typing can be determined using the waveguide-mode sensor. This technique is able to detect weak agglutinations that are almost impossible to detect with the human eye.
ABOblood group determination: Using anti-A and anti-B antibodies that bind specifically to either the A or to the B blood group surface antigens on
RBCs, it is possible to test a small sample of blood and determine the ABO blood type of an individual. It does not identify the
Rh(D) antigen (
Rh blood type).
The bedside card method of blood grouping relies on visual agglutination to determine an individual's blood group. The card contains dried blood group antibody
reagents fixed onto its surface. A drop of the individual's blood is placed on each blood group area on the card. The presence or absence of flocculation (visual agglutination) enables a quick and convenient method of determining the
ABO and
Rhesus status of the individual. As this technique depends on human eyes, it is less reliable than the blood typing based on waveguide-mode sensors.
In the case of red blood cells, transformed cells are known as
kodecytes. Kode technology exposes exogenous antigens on the surface of cells, allowing antibody-antigen responses to be detected by the traditional hemagglutination test.[20]
^Couch, Robert B. (1996), Baron, Samuel (ed.),
"Orthomyxoviruses", Medical Microbiology (4th ed.), Galveston (TX): University of Texas Medical Branch at Galveston,
ISBN978-0-9631172-1-2,
PMID21413353, retrieved 30 January 2024
^Donald J. Benton, Andrea Nans, Lesley J. Calder, Jack Turner, Ursula Neu, Yi Pu Lin, Esther Ketelaars, Nicole L. Kallewaard, Davide Corti, Antonio Lanzavecchia, Steven J. Gamblin, Peter B. Rosenthal, John J. Skehel (2 October 2018) [Sep 17, 2018].
"Hemagglutinin membrane anchor". Proceedings of the National Academy of Sciences of the United States of America. 115 (40): 10112–10117.
doi:10.1073/pnas.1810927115.
PMC6176637.
PMID30224494.{{
cite journal}}: CS1 maint: multiple names: authors list (
link)
^Theis, Samuel R.; Hashmi, Muhammad F. (2022),
"Coombs Test", StatPearls, Treasure Island (FL): StatPearls Publishing,
PMID31613487, retrieved 16 December 2022