CCR5 and Protection from AIDS

Brian Foley btf at
Thu Dec 24 13:20:36 EST 1998

Stefanie Greve wrote:
> Hello!
> After reading this thread I am quite puzzled. Until now 
> I have believed infection with HIV depends mostly on an 
> individuals cirumstances of living.  That is in most cases 
> on his or her sexual habits regardless of colour of skin 
> or sex.

	It depends not only on the individuals' habits but
also on those of the partner.  If one partner is monogamous,
they are still at risk if the other partner is not.
	The 32 base-pair deletion in the CCR5 gene is rare
in Africans, Native Americans, and other groups.  It is 
more common (roughly 10% of the population has one of these
delta-32 alleles and 1% is homozygous for delta-32) in 
norhtern Europeans and people of northern European descent.
So it is not skin color per se, but the delta-32 CCR5 allele
which plays a role, and it in turn is more common is a subset
of pale-skinned people.

> As males of all colours tend to have more sexual partners 
> than females testosterone indirectly but definitely plays a 
> significant role in achieving infection with HIV.

	There are numerous factors relating to sex and risk
of HIV infection.  As I said above, it matters not only how many
partners a person has, but also how many partners each of those
partners previously had.  If women have on average just 2 
partners, one in a steady relationship but the second tends to
be one who sleeps with hundreds, they are at huge risk.
Another factor to consider is that it makes lots of sense
that the woman (or the "receptive partner" in homosexual 
acts) is at greater risk than the man (or "insertive
partner"), due to the amount of boldily fluid exchanged, the
length of time in contact with that virus-laden fluid, and
the surfaces in which the fluid makes contact.

	We hope that women do not feel safe to engage in
unsafe sex, just because they do not "sleep around".  They
are at risk, even in a monogamous relationship, if the
partner has put himself at risk.  The idea that women are at
less risk because they have fewer partners is not correct.

|Brian T. Foley               btf at                       |
|HIV Database                 (505) 665-1970                         |
|Los Alamos National Lab     |
|Los Alamos, NM 87544  U.S.A. |

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