I was reading the question about the K103N mutation. I think you said it can occur if a person isn't taking an NNRTI. It got me thinking about something. Are HIVers who are delaying meds because they have high CD4s in danger of developing this mutation or others? Is is possible to have genotype with no mutations and then find out in a few years when you do start meds that you now have developed them, because you weren't on meds for so long?

Thanks so much

Hi,

I feared my response to that question was going to be too technical and that no one would bother reading it. Thanks for disproving that concern!

Spontaneous mutations, including K103N, can occur whenever HIV replicates; however, there is usually a "cost" to the virus for many mutations. In essence this means the virus becomes less "fit" (less capable of dividing rapidly and infecting cells). Mutations, like K103N, are much more likely to occur due to so-called selective pressure. This would include taking suboptimal or intermittent doses of a non-nucleoside reverse transcriptase inhibitor antiretroviral medication, such as nevirapine or efavirenz (Sustiva). Another way of getting a K103N mutation is to acquire a viral strain that already has developed this mutation. Transmission of viral strains that have viral mutations is becoming a more prevalent problem.

Dr. Bob

Viral Strain Interpretation (K103N, VIRAL MUTATIONS, 2010) Jan 9, 2010

How dangerous is K103N? Been undetectable since MArch 2009, want to know the history of this particular strain

Response from Dr. Frascino

Hello,

K103N is an HIV mutation. Mutations are slight changes within HIV's RNA, the genetic material that provides all the information and instructions for how HIV functions. Mutations can (and do) occur naturally in many living organisms. They can be induced or encouraged to occur by selective pressure, which is an external influence, such as a drug that affects the virus, radiation, etc.

K103N is the most common mutation found in HIVers who are taking non-nucleoside reverse transcriptase inhibitors or NNRTIs (drugs such as nevirapine or efavirenz). The "103" is called a "codon." It identifies the specific position on HIV's RNA genetic strand where the mutation is located. The "K" stands for the amino acid that is normally found at that position ("wild type" HIV); the "N" stands for the amino acid that's been substituted. The "N" is the mutation.

K103N involves a mutation in HIV's reverse transcriptase gene. The "K" (lysine) has been replaced by "N" (asparagine). This substitution mutation, K103N, makes HIV highly resistant to many approved drugs in the NNRTI class. Not all mutations are so troublesome and dangerous. Some mutations will have no impact on how well your HIV drugs works; others, like K103N, can knock out a number of available antiretrovirals.

Hope that helps clarify things. I know this gets a bit technical, but hey, you asked, right?

Dr. Bob