Question

Where can I get a genetic test for delta 32 gene?

26 March 2010. Related: All topics.

Hi, I have been reading about delta 32 gene mutation and I want to know if I can be tested for this on the NHS. If not do you know where I can get a test and how much it will cost? Thank you.

Answer

Answer: Charlotte Walker

Thank you for your question.

Genetic testing for the delta 32 mutation is not available on the NHS. It would only be available as part of a research programme and I am not aware of research studies in the UK at the moment.

The delta 32 gene mutation is a deletion of part of the genetic sequence making up the CCR5 receptor which is found on the surface of the CD4 cell. HIV uses this receptor to connect with and infect a CD4 cell.

We all have two genes for each characteristic (two sets of chromosomes), one from the mother and one from the father. Having one mutated gene for delta 32 and one regular gene (called heterozygous) is related to a reduced risk from HIV compared to someone with two regular genes. This type of heterozygous mutation occurs in about 20% of Caucasians but in about 1% of people from African origin.

If both genes carry the delta 32 mutation this is called homozygous and occurs in only about 1% of causations. This provides a much stronger protection against HIV. However, this protection is only against a type of HIV that uses the CCR5 co-receptor (called R5 tropic).

Approximately 10% of infections are related to a type of HIV that uses CXCR4 (called X4 tropic) and the delta 32 mutation provide no protection here. The chance someone has X4 tropic HIV increase with the time they have been HIV positive.

Therefore people who are homozygous for delta 32 can still become infected with HIV.

For further information explaining the effect of this mutation please follow this link.

Please see this more recent question that discusses why this test in not very helpful in terms of protection from HIV.