A paper published in the Journal 'Blood' entitled "HIV-1 incorporates ABO histo-blood group antigens that sensitise virions to complement-mediated inactivation" [1] suggests that transmission of HIV-1 is modified by both ABO blood group and the immune system enzyme complement. The premise is based on research showing how the ABO antigen (blood group marker) of the infected person is incorporated into the HIV virus that is replicated in their cells. Because the virus is coated in the person's blood group antigen, it then acts in the same way a red blood cell would when someone with an incompatible blood group becomes exposed to it, and the part of the immune system that would normally cause an incompatible blood transfusion reaction is activated against the virus, helping to protect the recipient against infection. This would mean that it would be harder for an individual of blood group O (the 'universal donor') to contract HIV infection from people of any other blood group apart from blood group O, as the recipient will have both anti-A and anti-B antigens in their blood. Conversely those with blood group AB (the 'universal recipient') who have no opposing blood group antibodies would contract HIV infection more easily from people of any blood group.



This paper follows previous research [2] on how complement is activated by anti-B IgM (the immune complex involved in incompatible transfusion reactions where the donor is blood group B or AB and the recipient is blood group A or O) and other factors, in blood from HIV-negative donors. In the research by Saarloos et. al. complement was however more easily activated against HIV by antibodies to HIV itself as a result of HIV infection than by IgM.



Later research [3] suggests that the immune system of some people with AIDS (PWA) who are blood group A or AB may form anti-A IgA, IgG and IgM (antibodies against their own blood group).



The HIV virus made in cells of an HIV-infected person will show their blood group antigen only when the originating cell expresses ABO antigens or is a lymphocyte (white blood cell). As ABH non-secretors have fewer cells expressing their blood group, it follows that they may produce more HIV viruses without blood group antigens than would ABH secretors. This could mean that it is as easy to become infected with HIV-1 from non-secretors of any blood group as it is from secretors of transfusion-compatible blood groups.



ABH non-secretors would be at some disadvantage in protection against HIV infection transmitted via mucous membranes, as they secrete lower levels of immune-protective substances [4].



HIV positive individuals and PWA should always take steps to avoid transmission of the HIV virus, whatever their blood group or secretor status. Neil and colleagues have however demonstrated a key concept in the relationship between blood groups and immunity, which is mirrored in numerous other blood group-disease connections. It also gives new meaning to the idea of universality in terms of blood group transfusion with relation to infection susceptibility.



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References:



1. Neil SJ, McKnight A , Gustafsson K, Weiss RA

HIV-1 incorporates ABO histo-blood group antigens that sensitise virions to complement-mediated inactivation.

Blood Online



2. Saarloos MN, Lint TF, Spear GT

Efficacy of HIV-specific and 'antibody-independent' mechanisms for complement activation by HIV-infected cells.

Clin Exp Immunol. 1995 Feb;99(2):189-95.

PMID 7851010



3. Friedli F, Rieben R, Wegmuller E et. al.

Normal levels of allo- but increased levels of potentially autoreactive antibodies against ABO histo-blood group antigens in AIDS patients.

Clin Immunol Immunopathol. 1996 Jul;80(1):96-100.

PMID 8674246



4. D'Adamo PJ.

Eat Right 4 Your Type Complete Blood Type Encyclopedia. p.320.

Pub. Penguin, 2002.