Abstract
In HIV patients, the set-point viral load (SPVL) is the most widely used predictor of disease severity. Yet SPVL varies over several orders of magnitude between patients. The heritability of SPVL quantifies how much of the variation in SPVL is due to transmissible viral genetics. There is currently no clear consensus on the value of SPVL heritability, as multiple studies have reported apparently discrepant estimates. Here we illustrate that the discrepancies in estimates are most likely due to differences in the estimation methods, rather than the study populations. Importantly, phylogenetic estimates run the risk of being strongly confounded by unrealistic model assumptions. Care must be taken when interpreting and comparing the different estimates to each other.
Glossary
- Asymptomatic phase
- HIV infections are generally split into three characteristic stages: (I) Primary infection/Acute phase; (II) Chronic asymptomatic phase; (III) AIDS phase.
- Viral load
- The density of virus in the blood of a patient. It is a proxy for the amount of virus in the rest of the body.
- Set-point viral load
- The viral load during the asymptomatic phase fluctuates around a remarkably stable level, the set-point viral load.
- Genetic variance
- Amount of variance in the trait (e.g. SPVL) that is due to differences in transmissible viral genetics.
- Environmental variance
- Amount of variance in the trait (e.g. SPVL) that is due to anything other then viral genetics.
- Viral heritability
- The fraction of phenotypic variance that is explained by transmissible genetic factors.
- Donor-recipient regression
- Method to estimate heritability by regressing the trait values in the recipients on the traits values of the donors.
- Seronegative
- Negative for HIV infection.
- Serodiscordant couples
- Sexual partnerships where only a single individual is infected.
- Pedigree
- Ancestral tree linking parents to their offspring.
- Genetic bottlneck
- Sudden decrease in population size where only a few genetic variants are selected. This leads to a drastic decrease in genetic variation in the population.
- Genetic drift
- Change in the genotype distribution over time due to the finite size of a population.