US – Administration of specific antibodies protected monkeys over months from a variant of the AIDS pathogen HIV. The researchers treated the monkeys with each a certain type of antibody, and then a exposed them for a week to the pathogen. Malcolm Martin’s team of the National Institute of Allergy and infectious diseases in Bethesda, Maryland, found that the unique antibody treatment can keep the animals from infection for up to 23 weeks.

A type of antibody, whose resistance was previously extended by chemical modifications in the body, proved to be particularly effective. While the monkeys got protected for an average of 14.5 weeks from being infected, monkeys without antibody treatment were infected on average after three weeks. The study has been published in the journal Nature.

More effective than previously tested vaccines

The approach by the researchers is called passive immunization. The problem with this method is that the antibodies are removed from the body and need to be given again and again. If it were possible to develop antibodies with a very high resistance, this would represent a major breakthrough. This study appears to have the passive transfer of antibodies which are more effective than previously tested vaccines.

The US researchers had oriented in its approach to successful strategies to protect against hepatitis A. Under certain circumstances, Martin and colleagues said, the protection in passive immunization against HIV could even be increased by a combination of the antibodies tested.

Three approaches in search for effective protection

Looking for an effective protection against HIV infection, three different ways are currently: i) passive immunization with antibodies that are administered as an infusion, ii) the active vaccination that causes an own immune response of the body and iii) the preventive administration of drugs that are already proven to the therapy in HIV-infected individuals. The third approach is being used in the US in high-risk groups while being used sporadically in Europe only.

The new study is a step forward for the antibody approach. However, it is still unclear whether the human immune system would accept or reject the antibodies.