Excising HIV DNA

[MitchMiller]

Tailored Enzyme Excises HIV DNA Inserted Into Genome


NEW YORK (Reuters Health) Jun 28 - Researchers have developed a tailored recombinase that is capable of recognizing and excising HIV DNA that has become integrated into the host cell genome.

Current treatments against HIV primarily target virus enzymes or work to prevent virus-cell fusion, senior author Dr. Frank Buchholz, from the Max-Planck-Institute for Molecular Cell Biology and Genetics in Dresden, Germany, and colleagues note. At present, there are no treatments against the integrated provirus, the viral DNA that is inserted in the host genome.

In the new study, reported in the June 19th issue of Science, the investigators describe the substrate-linked protein evolution of a recombinase that detects the asymmetric DNA patterns flanking the integrated provirus. The enzyme then excises the integrated HIV DNA.

"Although a long way from use in the clinic, we speculate that this type of technology might be adapted in future antiretroviral therapies, among other possible uses," the authors conclude.

Science 2007;29:1912-1915.

[Cerrid]

Here's the link to the Science paper:
http://www.sciencemag.org/cgi/content/abstract/316/5833/1912

Abstract:

HIV-1 Proviral DNA Excision Using an Evolved Recombinase
Indrani Sarkar,1* Ilona Hauber,2* Joachim Hauber,2{dagger} Frank Buchholz1{dagger}

HIV-1 integrates into the host chromosome and persists as a provirus flanked by long terminal repeats (LTRs). To date, treatment regimens primarily target the virus enzymes or virus-cell fusion, but not the integrated provirus. We report here the substrate-linked protein evolution of a tailored recombinase that recognizes an asymmetric sequence within an HIV-1 LTR. This evolved recombinase efficiently excised integrated HIV proviral DNA from the genome of infected cells. Although a long way from use in the clinic, we speculate that this type of technology might be adapted in future antiretroviral therapies, among other possible uses.

Heinrich-Pette-Institute for Experimental Virology and Immunology at the University of Hamburg

From their press release:

HIV kicked out: Fundament for a new therapy established
28. June 2007

A complete cure from an HIV-infection is currently not available. At present, lifelong treatment regimes are required to block the outbreak of AIDS, and these treatments do not eliminate the integrated provirus from infected cells. Now, scientists from the Heinrich-Pette-Institute for Experimental Virology and Immunology (HPI) in Hamburg and the Max-Planck-Institute of Molecular Cell Biology und Genetics in Dresden (MPI-CBG) have developed an enzyme that specifically cuts out the viral genome and eradicates the virus from the host cell.
(Science, June, 29th 2007).

Frank Buchholz, MPI Dresden (left), Ilona Hauber and Joachim Hauber, both HPI Hamburg; foto: HPI

HIV introduces its genetic material into the DNA of body cells permanently. In particular, the immune cells are doomed due to the production of new viruses. The teams of Joachim Hauber from the HPI and Frank Buchholz from the MPI-CBG have now succeeded in specifically removing the viral DNA from infected cells. “We got rid of the virus from the infected cells; nobody has done this before”, the scientists commented.

To achieve this result they genetically engineered a recombinase, an enzyme that works like molecular scissors. Recombinases cut and paste DNA sequences at specific sites. “Naturally occurring recombinases do not recognize viral sequences and are therefore not useful for an anti-viral approach”, said Buchholz: “So we had to develop a recombinase that recognizes the viral sequence and removes the virus with precision.”

The molecular biologists started from a recombinase that naturally is found in a bacteriophage. This enzyme, termed “Cre”, does not recognize sequences from the HIV genome. Using the forces of evolution the scientists used more than 120 generation cycles to breed the enzyme “Tre”, which is now able to recognize HIV sequences.

“Although Tre has so far only been tested in tissue culture cells, this work lays the technical foundation for a novel therapeutic approach that one day might be used to eradicate the HIV from cells of infected patients” said Hauber. However, it is still a long way until this approach can be used in clinical practice. “We will first go back to the bench to further improve the enzyme and then test whether the recombinase can be delivered efficiently and safely to cells in the human body”, said Buchholz and Hauber.

[hahaha]

Very interesting.  This is the first time I heard about "Recombinase".  Is it just like Ribonzyme in J&J Gene therapy?

I know there are lots of "bio-nerds" in this forum.  Any one can help to explain?

[gvcmdny]

Here is a research information from The Heinrich-Pette-Institute for Experimental Virology and Immunology (HPI), Germany.

http://www.hpi-hamburg.de/news/press/press/period/1041375600/31535999/1/article/52/rausschmiss.html?L=1&cHash=31d0b704e0

It's a little different then Ribozyme approach, ribozyme does not have enough catalytic power: it is able to add up to 14 nucleotides to a primer template in 24 hours until it is decomposed.

[bimazek]

looks impressive, the east europeans never stopped studying basic science and math even during the dark period, i visited and you would see them reading advanced physics and bio and math on the subway, there not being alot of diversions during communism, the intellectual pursuits were rigorous and strong, of course west german and germans in general have been med discover-ers for hundreds of years

i wish them good fortunes

[J220]

Very exciting stuff...see this is why I always remain hopeful about a cure being found. There was another thread asking the possibility of a cure, and one point alsways raised was that the virus inserts itself in the cells and becomes part of it. Well, now it seems that this could possibly be reversed! Fantastic. I only hope they move quickly on this, years for sure, but hopefully not decades.

By the way, Forbes.com (at http://www.forbes.com/markets/feeds/afx/2007/06/28/afx3868315.html )has an article where they portray this in very glowing terms..it reads:

Potential cure for HIV discovered
06.28.07, 4:07 PM ET

CHICAGO (Thomson Financial) - In a breakthrough that could potentially lead to a cure for HIV infection, scientists have discovered a way to remove the virus from infected cells, a study released today said.

The scientists engineered an enzyme which attacks the DNA of the HIV virus and cuts it out of the infected cell, according to the study published in Science magazine.

The enzyme is still far from being ready to use as a treatment, the authors warned, but it offers a glimmer of hope for the more than 40 mln people infected worldwide.

'A customized enzyme that effectively excises integrated HIV-1 from infected cells in vitro might one day help to eradicate (the) virus from AIDS patients,' Alan Engelman, of Harvard University's Dana-Farber Cancer Institute, wrote in an article accompanying the study.

Current treatments focus on suppressing the HIV virus in order to delay the onset of AIDS and dramatically extend the life of infected patients.

What makes HIV so deadly, however, is its ability to insert itself into the body's cells and force those cells to produce new infection.

'Consequently the virus becomes inextricably linked to the host, making it virtually impossible to 'cure' AIDS patients of their HIV-1 infection,' Engelman explained.

That could change if the enzyme developed by a group of German scientists can be made safe to use on people.

That enzyme was able to eliminate the HIV virus from infected human cells in about three months in the laboratory.

The researchers engineered an enzyme called Tre which removes the virus from the genome of infected cells by recognizing and then recombining the structure of the virus's DNA.

This ability to recognize HIV's DNA might one day help overcome one of the biggest obstacles to finding a cure: the ability of the HIV virus to avoid detection by reverting to a resting state within infected cells which then cease to produce the virus for months or even years.

'Numerous attempts have been made to activate these cells, with the hope that such strategies would sensitize the accompanying viruses to antiviral drugs, leading to virus eradication,' Engelman wrote.

'Advances with such approaches in patients have been slow to materialize.'

New experiments must be designed to see if the Tre enzyme can be used to recognize these dormant infected cells, he wrote.

'Although favorable results would represent perhaps only a baby step toward eventual use in patients, the discovery of the Tre recombinase proves that enzymatic removal of integrated HIV-1 from human chromosomes is a current-day reality,' he said.

The researchers who developed the enzyme were optimistic about their ability to design additional enzymes which would target other parts of the virus's DNA.

However they warned that there were significant barriers to overcome before the enzyme could be used to help cure patients.

'The most important, and likely most difficult, among these is that the enzyme would need efficient and safe means of delivery and would have to be able to function without adverse side effects,' wrote lead author Indrani Sarkar of the Max Planck Institute for Molecular Cell Biology and Genetics in Dresden.

'Nevertheless the results we present offer an early proof of principal for this type of approach, which we speculate might form a useful basis for the development of future HIV therapies,' Sarkar concluded.

tf.TFN-Europe_newsdesk@thomson.com