Saturday, September 17, 2022

Immune system uses two-step verification to defend against HIV

Good news!

"Human immunodeficiency virus 1, more commonly known as HIV-1, is known for its uncanny ability to evade the immune system. Scientists ... have now uncovered how our innate immune system – the body’s first line of quick defense in attacking foreign invaders – detects HIV-1, even when the virus is present in very small amounts.   ...
two-step molecular strategy that jolts the innate immune response into action when exposed to HIV-1. This discovery could impact drug development for HIV treatments and vaccines, as well as shape our understanding of how the innate immune response is implicated in other areas – including neurodegenerative disorders such as Alzheimer’s. ...
Cyclic GMP-AMP synthase (cGAS) is a key signaling protein in the innate immune system that senses DNA floating in a cell. If cGAS does detect a foreign presence, it activates a molecular pathway to fight off the invader.
However, because HIV-1 is an RNA virus, it produces very little DNA – so little, in fact, that scientists have not understood how cGAS and the innate immune system are able to detect it and distinguish it from our own DNA. ...
the innate immune system requires a two-step security check for it to activate against HIV-1. The first step involves an essential protein – polyglutamine binding protein 1 (PQBP1) – recognizing the HIV-1 outer shell as soon as it enters the cell and before it can replicate. PQBP1 then coats and decorates the virus, acting as an alert signal to summon cGAS. Once the viral shell begins to disassemble, cGAS activates additional immune-related pathways against the virus. ...
This two-part mechanism also opens the door to vaccination approaches ...
these findings also illuminate how our bodies respond to other autoimmune or neurodegenerative inflammatory diseases. For example, PQBP1 has been shown to interact with tau – the protein that becomes dysregulated in Alzheimer’s disease – and activate the same inflammatory cGAS pathway. ..."

From the abstract:
"We have previously described polyglutamine-binding protein 1 (PQBP1) as an adapter required for the cyclic GMP-AMP synthase (cGAS)-mediated innate response to the human immunodeficiency virus 1 (HIV-1) and other lentiviruses. Cytoplasmic HIV-1 DNA is a transient and low-abundance pathogen-associated molecular pattern (PAMP), and the mechanism for its detection and verification is not fully understood. Here, we show a two-factor authentication strategy by the innate surveillance machinery to selectively respond to the low concentration of HIV-1 DNA, while distinguishing these species from extranuclear DNA molecules. We find that, upon HIV-1 infection, PQBP1 decorates the intact viral capsid, and this serves as a primary verification step for the viral nucleic acid cargo. As reverse transcription and capsid disassembly initiate, cGAS is recruited to the capsid in a PQBP1-dependent manner. This positions cGAS at the site of PAMP generation and sanctions its response to a low-abundance DNA PAMP."

Immune system uses two-step verification to defend against HIV | Scripps Research Scripps Research discovery could offer new methods for treating HIV, while uncovering the innate immune system’s role in other diseases.




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