Immune cells infected by HIV extend long thin tube-like structures that deliver virus-derived inhibitory proteins to disable non-infected immune cells. The report published online this week in Nature Immunology, sheds light on the processes that allow HIV to disrupt the immune system.

The Nef protein from HIV can block the generation of neutralizing antibodies against HIV; however, it was previously unclear how this occurs as antibody-producing B cells are not themselves infected by the virus. Andrea Cerutti and colleagues show that Nef triggers the formation of nanotubule-like structures to transport the protein to other immune cells, such as the B cells.

The new findings provide an explanation for how Nef protein is delivered to, and arrests B cell function, without becoming infected by HIV itself. The authors call this stealth delivery of immunosuppressive Nef protein the 'Trojan horse' of immune evasion.