University of Michigan scientists have provided the most detailed picture yet of a key HIV accessory protein that foils the body's normal immune response. Based on the findings, which appear online in the journal PLoS Pathogens, the team is searching for new drugs that may someday allow infected people to be cured and no longer need today's AIDS drugs for a lifetime.

At left, a normal, uninfected cell with green-stained MHC-I protein on the cell surface. At right, an HIV infected cell -- most of the MHC-I builds up inside, keeping the cell from telling the immune system that it harbors a virus. (Credit: Kathleen Collins, University of Michigan)

"There's a big hole in current therapies, in that all of them prevent new infection, but none attack the cells that are already infected and hidden from the immune response," says Kathleen L. Collins, M.D., Ph.D., the study's senior author and a U-M associate professor in both internal medicine and microbiology and immunology.

In people infected with HIV (human immunodeficiency virus), the virus that causes AIDS, there's an unsolved problem with current anti-viral drugs. Though life-saving, they cannot root the virus out of the body. Infected cells are able to live on, undetected by the immune system, and provide the machinery for the virus to reproduce and spread.

"People have to be on the existing drugs, and when they're not, the virus rebounds. If we can develop drugs that seek out and eradicate the remaining factories for the virus, then maybe we could eradicate the disease in that person," Collins says.

Research details

The new research details the complex actions of a protein, HIV-1 Nef, that is known to keep immune system cells from doing their normal jobs of detecting and killing infected cells.

Collins and her team show how Nef disables two key immune system players inside an infected cell. These are molecules called major histocompatability complex 1 proteins (MHC-1) that present HIV antigens to the immune system, and CD4, the cell-surface receptor that normally locks onto a virus and allows it to enter the cell.

Collins likens MHC-1 to motion detectors on a house, which send the first signal to a monitoring station if an invader breaks in.

"The immune system, especially the cytotoxic T lymphocytes, are like the monitors who get the signal that there's a foreign invader inside the cell, and send out police cars," she says. "The 'police' are toxic chemicals produced by T lymphocyte cells, which kill the cell that harbors the invader."

By in effect pushing the MHC-I proteins into an infected cell's "trash bin" so they fail to alert the T lymphocytes, Nef's actions allow active virus to hide undetected and reproduce. Also, once a cell has been infected, Nef destroys CD4. The result is that this encourages new virus to spread to uninfected cells.

Nef's activities are variable and complex. But the research team's findings suggest that the many pathways involved may end in a final common step. That could make it possible to find a drug that could block several Nef functions.

Implications

Collins' lab is now screening drug candidates to find promising Nef inhibitors. Such drugs, which are at least 10 years away from use in people, would supplement, not replace, existing anti-viral drugs given to HIV-infected people. The new drugs would target the reservoirs where the virus hides.

In developing countries, the new drugs could have a huge impact, Collins says. Today, children born with HIV infection start taking the existing anti-HIV drugs at birth. It's very hard to continue costly treatments for a lifetime. But if children could be cured within a few years, global HIV treatment efforts could spread their dollars further and be much more successful, she says.

GeneWorks to expand into South-East Asia


Adelaide -based reagent and service company GeneWorks is partnering Malaysian bioinformatics company Synamatix to initiate sequencing of microbial organisms.

Researchers at the University of Pennsylvania School of Medicine have modified a honeybee venom toxin so that it can be used as a tool to study the inner workings of ion channels that control heart rate and the recycling of salt in kidneys. In general, ion channels selectively allow the passage of small ions such as sodium, potassium, or calcium into and out of the cell.

The study, published in the Proceedings of the National Academy of Sciences, is from the laboratory of Zhe Lu, M.D, Ph.D., Professor of Physiology and a Howard Hughes Medical Institute Investigator, who looked at the action of a natural bee toxin on inward-rectifier potassium channels, Kir channels for short, to identify new approaches to treat cardiovascular disease.

The honeybee venom toxin, called tertiapin, or TPN, stops the flow of potassium ions across cell membranes by plugging up the opening of Kir channels on the outside of cells. Kir channels in kidneys are potential new targets for treating hypertension. "The clue comes from patients with genetic defects in these channels who lose a lot of sodium because it cannot be effectively reabsorbed and thus have low blood pressure," notes Lu. "An inhibitor specifically against these kidney channels will allow this idea to be tested."

Developing a specific inhibitor for one type of Kir channel has been challenging because the target site is very similar among different types of Kir channels. For example, while TPN inhibits Kir type 1 channels in kidney cells, it also inhibits other types of Kir channels in heart cells. After more than a decade, Lu and his colleagues succeeded in bioengineering a TPN that selectively inhibits Kir channels important for salt recycling in kidneys.

By introducing two mutations into TPN, they engineered a variant, called TPNLQ, which stems the flow of potassium ions in renal Kir type 1 channels at low concentrations, and with a 250-fold sensitivity over six other types of Kir channels.

The development of TPNLQ demonstrates that a highly specific inhibitor of potassium channels can be engineered. TPNLQ can now be used as a tool to prove the concept, in animal studies, that reducing salt reabsorption by plugging up renal Kir type 1 potassium channels is a potential new way to treat hypertension.

Yajamana Ramu and Yanping Xu of Penn conducted this study with Dr. Lu. The research was supported by the National Institutes of General Medical Sciences and the University of Pennsylvania Research Foundation.

Transgenic plants

Transgenic plants are plants that have been genetically engineered, a breeding approach that uses recombinant DNA techniques to create plants with new characteristics.They are identified as a class of genetically modified organism (GMO)..

Genetically modified organism

A genetically modified organism (GMO) is an organism whose genetic material has been altered using techniques in genetics generally known as recombinant DNA technology.

Biopharmaceutical

Biopharmaceuticals are medical drugs produced using biotechnology.

The first such substance approved for therapeutic use was recombinant human insulin.

The large majority of biopharmaceutical products are pharmaceuticals that are derived from life forms.

A potentially controversial method of producing biopharmaceuticals involves transgenic organisms, particularly plants and animals that have been genetically modified to produce drugs..

Pharmacology

Pharmacology is the study of how substances interact with living organisms to produce a change in function.

The field encompasses drug composition and properties, interactions, toxicology, therapy, and medical applications and antipathogenic capabilities. Development of medication is a vital concern to medicine, but also has strong economical and political implications.

To protect the consumer and prevent abuse, many governments regulate the manufacture, sale, and administration of medication.

Key analytical and laboratory equipment in a biotechnology labs are shown here.

Spectrum Spotlight scanning FT-IR

(Perkin Elmer)

Applications:

ICP-MS

(Perkin Elmer ELAN DRC II)

AAS

(Perkin Elmer AAnalyst 200)

Epifluorescence Microscope (Zeiss Axioplan 2)

Application:

Cell imaging (3D), enumeration of total, live and dead cells; study of biofilm development, respiratory activity, EPS production

Drug Delivery
Nanoparticles hitchhike on red blood cells for drug delivery