The information to make antibodies is encoded in DNA and inserted into the virus. In this case, researchers encoded the information to make three different antibodies into a strain of rAAV. The scientists then infected four monkeys with a virus called SHIV.
It can therefore speed up the pace of experiments. Further analysis revealed that only this animal had maintained robust [production] of more than one of the bNAbs. The Miami researchers found that three of the animals developed antibodies that attacked all three bNAbs. This monkey continues to have an undetectable viral load three years after first receiving rAAV therapy via intramuscular injection.
The researchers then attempted a similar experiment with 12 additional monkeys. However, the immune systems of these monkeys also attacked the bNAbs. The experiments in gene transfer seemed safe. There were 21 participants in this study, all of whom were healthy and HIV negative and who received different doses of rAAV injected into muscle.
The gene transfer was safe and side effects were generally mild to moderate and included the following:. All side effects were temporary and resolved without treatment. No serious side effects occurred and no one died. There were no abnormal laboratory test results. Technicians detected evidence of PG9 production from muscle cells. However, the levels of this antibody were too low to be detected in the blood. Scientists are not certain why antibody levels were so low. Some vaccine recipients developed antibodies that attacked PG9.
Different teams of researchers are trying to find ways to solve this problem of the immune system attacking bNAbs that are made via gene transfer. It is likely that there will be additional gene transfer experiments in the future. The lone success of the Miami monkey heralds a potential approach where people could one day receive gene transfer for antibodies that attack HIV.
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This would be helpful both to protect HIV-negative people and also to treat HIV-positive people, perhaps freeing them from the need to take anti-HIV drugs on a regular basis. Do you work in HIV or hep C? FDA—Rare cases of liver injury with some hepatitis C treatments. British Columbia — Increasing cases of syphilis affecting the eye.
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Production of this Web site has been made possible through a financial contribution from the Public Health Agency of Canada. We comply with the HONcode standard for trustworthy health information: verify here. Some of the cells then migrated to the brain and formed neuron-supporting cells called glia that produced a needed protein. Italian gene therapy researchers have reported comparable results for a similar treatment given to young patients with the brain disease metachromatic leukodystrophy.
For many disorders, the missing protein operates within cells, and so all cells that need it must receive the vector. The story of the viral vector that seems to answer this need begins with a death. In the early s a leader of the field, geneticist James Wilson of the University of Pennsylvania UPenn , was forced to redirect his research. Wilson had led the trial in which year-old Jesse Gelsinger died from a massive immune reaction to a potent adenovirus vector that he had received to treat his liver disease. Wilson, who had a financial interest in the trial, faced a lawsuit by the family and an FDA investigation, and he eventually agreed to a 5-year ban on leading clinical trials.
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So he turned to finding new types of AAVs, which were safer than adenoviruses and had become a popular vector. Most tantalizing of all was its ability to home in on neurons, which are the key to treating many brain and spinal diseases. In , a French team and the lab of Brian Kaspar at Nationwide published separate papers that galvanized the field: Given intravenously to newborn mice, AAV9 crossed the blood-brain barrier—the tight network of cells that protects the central nervous system from pathogens and toxins—and infected neurons throughout the spinal cord and the brain.
Infants with it lack a functioning SMN1 gene, which codes for a protein called survival motor neuron SMN that sustains spinal neurons throughout life. Most people have multiple copies of a backup gene, SMN2, that can produce small amounts of SMN, limiting the severity of the disease. But those with SMA1 have only two of those backup genes, and far too little of the crucial protein. They planned to inject it intravenously, after showing that newborn mice with SMA1 that were treated in this way had normal motor function and life spans.
But that would likely require massive amounts of viral vector. Because liver cells are also a favorite target of AAVs, the liver removes most AAV9 injected into the blood; much of what remains goes to other tissues. Yet tests with monkeys suggested the dose would be safe. A new company co-founded by Kaspar called AveXis funded the later stages of the trial after licensing the therapy from Nationwide. Still, many gene therapy researchers held their breath, fearing another Gelsinger-like disaster.
Soon after the first baby received a test dose of the AAV9 therapy, her liver enzymes soared to 31 times normal, signaling possible cell damage. But steroids quickly brought the levels down, and FDA advised him to keep going, he says. Three other infants developed elevated liver enzymes, but there were no clinical signs of liver damage and the trial continued. This was not a modest improvement. This is a transformational change. Instead of becoming floppier and struggling to breathe, they got stronger.
Lying on her stomach, Evelyn one day started to lift her head, Elena Villarreal recalls. And 11 of the 12 who received the larger of two AAV9 doses—one of whom was treated late, at 6 months—can sit at least briefly without help, eat, and speak. Matteo, a boy in Miami, Florida, who got the therapy just 27 days after birth, can run and is hitting normal developmental milestones, says his father, Derwin Almeida.
How long the treatment will work is unknown.
But Nationwide researchers are working on countermeasures, such as filtering antibodies from the blood or giving certain immunosuppressing drugs, Mendell says. Another distant worry is cancer. AveXis has launched a second SMA1 study, and it also plans to treat milder forms of the condition. Delivering gene therapy to the brain has meant drilling into the skull.
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A new vector may reach the brain more easily, through the blood. Now that high-dose, systemically delivered AAV gene therapy appears safe, teams at Nationwide and elsewhere are launching trials for other neuromuscular diseases, which will aim to deliver a new gene by IV to muscle cells rather than neurons. Scientists are also exploring the next question for AAV9: Can it go beyond helping spinal neurons and reach deep into the brain at levels high enough to halt diseases there? The first results could come from an ongoing trial, sponsored by the company Abeona Therapeutics and run by Nationwide, that is using IV delivery of an AAV9 gene therapy for Sanfilippo type A syndrome.
Research Focus: Gene therapy offers new hope for Fabry disease | Nova Scotia Health Authority
Children with the disease lack an enzyme needed to break down heparan sulfate, a molecule that builds up in the brain and causes damage that is evident at ages 2 to 6. One year after three children were treated, levels of heparan sulfate in their spinal fluid have dropped sharply, their enlarged livers have shrunk, and their scores on nonverbal cognitive tests appear to have stabilized, Flanigan has reported at meetings. And spinal delivery should reduce any immune response. For patients with SMA1 and other progressive disorders, early treatment is critical.
For now, siblings of children already afflicted by these genetic diseases are the most likely to be identified early enough for preventive treatment. Some researchers remain skeptical that the new, less invasive ways of delivering AAV9 will reach enough brain cells. Other gene therapists are pinning their hopes on finding new AAV vectors that are even better at crossing the blood-brain barrier.
Voyager Therapeutics in Cambridge, Massachusetts, says these vectors appear to work in monkeys, too, though those data remain unpublished. By Kristen McTighe Sep. By Jeffrey Mervis Sep.