HIV-1

HIV-1, the causative agent of acquired immunodeficiency syndrome (AIDS), contains an RNA genome that produces a chromosomally integrated DNA during the replicative cycle.

Dendritic cells

Dendritic cells (DCs) are thought to mediate HIV-1 transmission but it is becoming evident that different DC subsets at the sites of infection have distinct roles.

In the genital tissues, two different DC subsets are present: the Langerhans cells (LCs) and the DC-SIGN(+)-DCs.

Although DC-SIGN(+)-DCs mediate HIV-1 transmission, recent data demonstrate that LCs prevent HIV-1 transmission by clearing invading HIV-1 particles.

However, this protective function of LCs is dependent on the function of the C-type lectin Langerin (CD207) : blocking Langerin function by high virus concentrations enables HIV-1 transmission by LCs.

tat and Tar

The HIV Tat protein (MIM.601409), a transcription-activating protein that binds to the bulge region of a stable stem-bulge-loop structure, TAR RNA, activates the HIV-1 long terminal repeat (LTR).

Tat activates the LTR less efficiently in rodent than in human cells, suggesting that cellular RNA-binding proteins are also involved in the regulation of HIV replication.

TAR DNA may possess distinct regulatory elements that play a role in modulating HIV-1 gene expression.

References

 de Witte L, Nabatov A, Geijtenbeek TB. Distinct roles for DC-SIGN(+)-dendritic cells and Langerhans cells in HIV-1 transmission. Trends Mol Med. 2007 Dec 3; PMID: 18055263