Training cells to control AIDS

A new treatment for AIDS has shown promise in controlling the infection in macaques. The new technique is a form of immune therapy that uses the subject's own blood cells. Cells are exposed to proteins extracted from the simian immunodeficiency virus (SIV, which is similar to the human version, HIV) in vitro and then infused back into the subject. The exposure is thought to 'train' the blood cells to recognize the virus so that the immune system can fight it more effectively.

The research, led by Stephen J. Kent (University of Melbourne, Victoria, Australia), used 36 pigtail macaques infected with SIV. Virus titers were 10 times lower in treated macaques than in untreated controls, and this reduction persisted for up to 1 year after the initial treatment (PLoS Pathog. 4, e1000055; 2008). The treatment also prolonged the lives of infected macaques, delaying mortality.

Clinical trials evaluating the immunotherapy in humans are already planned. HIV infection affects more than 33 million people worldwide. Though medical therapies exist, the drugs are expensive, must be taken long-term, may lose effectiveness over time and may have adverse side effects. The results of Kent's study suggest that the new immune approach may offer an effective alternative for controlling AIDS.

Females sniff out inbred males

It is well known that female animals prefer to mate with heterozygous males. It remains unclear, however, whether females can identify heterozygosity by a specific genetic marker, or whether heterozygous males are more attractive because they are generally healthier than homozygous males and are more likely to prevail in a competition.

Jane Hurst of the University of Liverpool (UK) and colleagues targeted two genetic markers that might enable mice to identify heterozygosity by scent: the major histocompatibility complex and the major urinary proteins (Curr. Biol. 18, 619–623; 2008). They set up a construct in which females could choose between two males that were either heterozygous or homozygous in one of the genetic regions (zygosity of the other region was kept constant). The males were restricted to separate areas to reduce potential for competition. Females distinctly preferred males that were heterozygous in the major urinary proteins. Zygosity in the major histocompatibility complex did not affect female preference.

This is the first evidence that females can identify heterozygosity through a signal that does not directly affect male health. The researchers note that their findings show only that females prefer to associate with heterozygous males. Their next step will be to investigate whether females' actual mating preference is affected.

Why bats dig dirt

Many animals, including humans, regularly consume clay and dirt. This is thought to be a way of supplementing a diet with essential nutrients such as sodium and calcium. A study led by Christian Voigt of the Leibniz Institute for Zoo and Wildlife Research (Berlin, Germany) now shows that fruit-eating bats that visit 'mineral licks' do so for different reasons.

The researchers captured 28 bats of two different species at mineral licks and control sites in Ecuador (PLoS ONE 3, e2011; 2008). One bat species ate solely fruit and the other was omnivorous. Because the mineral content of fruit is relatively high, the researchers predicted that omnivorous bats would be more likely to consume additional minerals. Surprisingly, there were many more frugivorous bats than omnivorous ones at the mineral licks. Furthermore, analysis of bat tissue samples showed that frugivores captured at mineral licks were not lacking minerals.

The researchers concluded that frugivorous bats consumed dirt primarily for its ability to counteract the toxins found in fruit rather than for mineral supplementation. Pregnant and lactating bats in particular are known to frequent mineral licks; this may be because they consume more fruit than usual and are therefore more vulnerable to toxic effects.