Fixing a Baby’s Abnormal Genes in the Womb May Soon Be Possible
A couple holds up a picture of their ultrasound.
By now you have probably heard something about CRISPR, the simple and relatively inexpensive method of precisely editing the genomes of plants, animals, and humans.
The treatment of disease in fetuses, the liminal category of life between embryos and humans, poses the next frontier.
Through CRISPR and other methods of gene editing, scientists have produced crops to be more nutritious, better able to resist pests, and tolerate droughts; engineered animals ranging from fruit flies to monkeys to make them better suited for scientific study; and experimentally treated the HIV virus, Hepatitis B, and leukemia in human patients.
There are also currently FDA-approved trials to treat blindness, cancer, and sickle cell disease in humans using gene editing, and there is consensus that CRISPR's therapeutic applications will grow significantly in the coming years.
While the treatment of human disease through use of gene editing is not without its medical and ethical concerns, the avoidance of disease in embryos is far more fraught. Nonetheless, Nature reported in November that He Jiankui, a scientist in China, had edited twin embryos to disable a gene called CCR5 in hopes of avoiding transmission of HIV from their HIV-positive father.
Though there are questions about the effectiveness and necessity of this therapy, He reported that sequencing has proven his embryonic gene edits were successful and the twins were "born normal and healthy," although his claims have not been independently verified.
More recently, Denis Rebrikov, a Russian scientist, announced his plans to disable the same gene in embryos to be implanted in HIV-positive women later this year. Futuristic as it may seem, prenatal gene editing is already here.
The treatment of disease in fetuses, the liminal category of life between embryos and humans, poses the next frontier. Numerous conditions—some minor, some resulting in a lifetime of medical treatment, some incompatible with life outside of the womb—can be diagnosed through use of prenatal diagnostic testing. There is promising research suggesting doctors will soon be able to treat or mitigate at least some of them through use of fetal gene editing.
This research could soon present women carrying genetically anomalous fetuses a third option aside from termination or birthing a child who will likely face a challenging and uncertain medical future: Whether to undergo a fetal genetic intervention.
However, genetic intervention will open the door to a host of ethical considerations, particularly with respect to the relationship between pregnant women and prenatal genetic counselors. Current counselors theoretically provide objective information and answer questions rather than advise their pregnant client whether to continue with her pregnancy, despite the risks, or to have an abortion.
In practice, though, prenatal genetic counseling is most often directive, and the nature of the counseling pregnant women receive can depend on numerous factors, including their religious and cultural beliefs, their perceived ability to handle a complicated pregnancy and subsequent birth, and their financial status. Introducing the possibility of a fetal genetic intervention will exacerbate counselor reliance upon these considerations and in some cases lead to counseling that is even more directive.
Some women in the near future will face the choice of whether to abort, keep, or treat a genetically anomalous fetus.
Future counselors will have to figure out under what circumstances it is even appropriate to broach the subject. Should they only discuss therapies that are FDA-approved, or should they mention experimental treatments? What about interventions that are available in Europe or Asia, but banned in the United States? Or even in the best case of scenario of an FDA-approved treatment, should a counselor make reference to it if she knows for a fact that her client cannot possibly afford it?
Beyond the basic question of what information to share, counselors will have to confront the fact that the very notion of fixing or "editing" offspring will be repugnant to many women, and inherent in the suggestion is the stigmatization of individuals with disabilities. Prenatal genetic counselors will be on the forefront of debates surrounding which fetuses should remain as they are and which ones should be altered.
Despite these concerns, some women in the near future will face the choice of whether to abort, keep, or treat a genetically anomalous fetus in utero. Take, for example, a woman who learns during prenatal testing that her fetus has Angelman syndrome, a genetic disorder characterized by intellectual disability, speech impairment, loss of muscle control, epilepsy, and a small head. There is currently no human treatment for Angelman syndrome, which is caused by a loss of function in a single gene, UBE3A.
But scientists at the University of North Carolina have been able to treat Angelman syndrome in fetal mice by reactivating UBE3A through use of a single injection. The therapy has also proven effective in cultured human brain cells. This suggests that a woman might soon have to consider injecting her fetus's brain with a CRISPR concoction custom-designed to target UBE3A, rather than terminate her pregnancy or bring her fetus to term unaltered.
Assuming she receives the adequate information to make an informed choice, she too will face an ethical conundrum. There will be the inherent risks of injecting anything into a developing fetus's brain, including the possibility of infection, brain damage, and miscarriage. But there are also risks specific to gene editing, such as so-called off-target effects, the possibility of impacting genes other than the intended one. Such effects are highly unpredictable and can be difficult to detect. So too is it impossible to predict how altering UBE3A might lead to other genetic and epigenetic changes once the baby is born.
There are no easy answers to the many questions that will arise in this space.
A woman deciding how to act in this scenario must balance these risks against the potential benefits of the therapy, layered on top of her belief system, resources, and personal ethics. The calculus will be different for every woman, and even the same woman might change her mind from one pregnancy to the next based on the severity of the condition diagnosed and other available medical options.
Her genetic counselor, meanwhile, must be sensitive to all of these concerns in helping her make her decision, keeping up to date on the possible new treatments, and carefully choosing which information to disclose in striving to be neutral. There are no easy answers to the many questions that will arise in this space, but better to start thinking about them now, before it is too late.
Catching colds may help protect kids from Covid
A new study shows that the immune system's response to colds can help prepare it to defend against COVID-19 - but only in the very young.
A common cold virus causes the immune system to produce T cells that also provide protection against SARS-CoV-2, according to new research. The study, published last month in PNAS, shows that this effect is most pronounced in young children. The finding may help explain why most young people who have been exposed to the cold-causing coronavirus have not developed serious cases of COVID-19.
One curiosity stood out in the early days of the COVID-19 pandemic – why were so few kids getting sick. Generally young children and the elderly are the most vulnerable to disease outbreaks, particularly viral infections, either because their immune systems are not fully developed or they are starting to fail.
But solid information on the new infection was so scarce that many public health officials acted on the precautionary principle, assumed a worst-case scenario, and applied the broadest, most restrictive policies to all people to try to contain the coronavirus SARS-CoV-2.
One early thought was that lockdowns worked and kids (ages 6 months to 17 years) simply were not being exposed to the virus. So it was a shock when data started to come in showing that well over half of them carried antibodies to the virus, indicating exposure without getting sick. That trend grew over time and the latest tracking data from the CDC shows that 96.3 percent of kids in the U.S. now carry those antibodies.
Antibodies are relatively quick and easy to measure, but some scientists are exploring whether the reactions of T cells could serve as a more useful measure of immune protection.
But that couldn't be the whole story because antibody protection fades, sometimes as early as a month after exposure and usually within a year. Additionally, SARS-CoV-2 has been spewing out waves of different variants that were more resistant to antibodies generated by their predecessors. The resistance was so significant that over time the FDA withdrew its emergency use authorization for a handful of monoclonal antibodies with earlier approval to treat the infection because they no longer worked.
Antibodies got most of the attention early on because they are part of the first line response of the immune system. Antibodies can bind to viruses and neutralize them, preventing infection. They are relatively quick and easy to measure and even manufacture, but as SARS-CoV-2 showed us, often viruses can quickly evolve to become more resistant to them. Some scientists are exploring whether the reactions of T cells could serve as a more useful measure of immune protection.
Kids, colds and T cells
T cells are part of the immune system that deals with cells once they have become infected. But working with T cells is much more difficult, takes longer, and is more expensive than working with antibodies. So studies often lags behind on this part of the immune system.
A group of researchers led by Annika Karlsson at the Karolinska Institute in Sweden focuses on T cells targeting virus-infected cells and, unsurprisingly, saw that they can play a role in SARS-CoV-2 infection. Other labs have shown that vaccination and natural exposure to the virus generates different patterns of T cell responses.
The Swedes also looked at another member of the coronavirus family, OC43, which circulates widely and is one of several causes of the common cold. The molecular structure of OC43 is similar to its more deadly cousin SARS-CoV-2. Sometimes a T cell response to one virus can produce a cross-reactive response to a similar protein structure in another virus, meaning that T cells will identify and respond to the two viruses in much the same way. Karlsson looked to see if T cells for OC43 from a wide age range of patients were cross-reactive to SARS-CoV-2.
And that is what they found, as reported in the PNAS study last month; there was cross-reactive activity, but it depended on a person’s age. A subset of a certain type of T cells, called mCD4+,, that recognized various protein parts of the cold-causing virus, OC43, expressed on the surface of an infected cell – also recognized those same protein parts from SARS-CoV-2. The T cell response was lower than that generated by natural exposure to SARS-CoV-2, but it was functional and thus could help limit the severity of COVID-19.
“One of the most politicized aspects of our pandemic response was not accepting that children are so much less at risk for severe disease with COVID-19,” because usually young children are among the most vulnerable to pathogens, says Monica Gandhi, professor of medicine at the University of California San Francisco.
“The cross-reactivity peaked at age six when more than half the people tested have a cross-reactive immune response,” says Karlsson, though their sample is too small to say if this finding applies more broadly across the population. The vast majority of children as young as two years had OC43-specific mCD4+ T cell responses. In adulthood, the functionality of both the OC43-specific and the cross-reactive T cells wane significantly, especially with advanced age.
“Considering that the mortality rate in children is the lowest from ages five to nine, and higher in younger children, our results imply that cross-reactive mCD4+ T cells may have a role in the control of SARS-CoV-2 infection in children,” the authors wrote in their paper.
“One of the most politicized aspects of our pandemic response was not accepting that children are so much less at risk for severe disease with COVID-19,” because usually young children are among the most vulnerable to pathogens, says Monica Gandhi, professor of medicine at the University of California San Francisco and author of the book, Endemic: A Post-Pandemic Playbook, to be released by the Mayo Clinic Press this summer. The immune response of kids to SARS-CoV-2 stood our expectations on their head. “We just haven't seen this before, so knowing the mechanism of protection is really important.”
Why the T cell immune response can fade with age is largely unknown. With some viruses such as measles, a single vaccination or infection generates life-long protection. But respiratory tract infections, like SARS-CoV-2, cause a localized infection - specific to certain organs - and that response tends to be shorter lived than systemic infections that affect the entire body. Karlsson suspects the elderly might be exposed to these localized types of viruses less often. Also, frequent continued exposure to a virus that results in reactivation of the memory T cell pool might eventually result in “a kind of immunosenescence or immune exhaustion that is associated with aging,” Karlsson says. https://leaps.org/scientists-just-started-testing-a-new-class-of-drugs-to-slow-and-even-reverse-aging/particle-3 This fading protection is why older people need to be repeatedly vaccinated against SARS-CoV-2.
Policy implications
Following the numbers on COVID-19 infections and severity over the last three years have shown us that healthy young people without risk factors are not likely to develop serious disease. This latest study points to a mechanism that helps explain why. But the inertia of existing policies remains. How should we adjust policy recommendations based on what we know today?
The World Health Organization (WHO) updated their COVID-19 vaccination guidance on March 28. It calls for a focus on vaccinating and boosting those at risk for developing serious disease. The guidance basically shrugged its shoulders when it came to healthy children and young adults receiving vaccinations and boosters against COVID-19. It said the priority should be to administer the “traditional essential vaccines for children,” such as those that protect against measles, rubella, and mumps.
“As an immunologist and a mother, I think that catching a cold or two when you are a kid and otherwise healthy is not that bad for you. Children have a much lower risk of becoming severely ill with SARS-CoV-2,” says Karlsson. She has followed public health guidance in Sweden, which means that her young children have not been vaccinated, but being older, she has received the vaccine and boosters. Gandhi and her children have been vaccinated, but they do not plan on additional boosters.
The WHO got it right in “concentrating on what matters,” which is getting traditional childhood immunizations back on track after their dramatic decline over the last three years, says Gandhi. Nor is there a need for masking in schools, according to a study from the Catalonia region of Spain. It found “no difference in masking and spread in schools,” particularly since tracking data indicate that nearly all young people have been exposed to SARS-CoV-2.
Both researchers lament that public discussion has overemphasized the quickly fading antibody part of the immune response to SARS-CoV-2 compared with the more durable T cell component. They say developing an efficient measure of T cell response for doctors to use in the clinic would help to monitor immunity in people at risk for severe cases of COVID-19 compared with the current method of toting up potential risk factors.
In this week's Friday Five: The eyes are the windows to the soul - and biological aging?
Plus, what bean genes mean for health and the planet, a breathing practice that could lower levels of tau proteins in the brain, AI beats humans at assessing heart health, and the benefits of "nature prescriptions"
The Friday Five covers five stories in research that you may have missed this week. There are plenty of controversies and troubling ethical issues in science – and we get into many of them in our online magazine – but this news roundup focuses on new scientific theories and progress to give you a therapeutic dose of inspiration headed into the weekend.
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Here are the stories covered this week:
- The eyes are the windows to the soul - and biological aging?
- What bean genes mean for health and the planet
- This breathing practice could lower levels of tau proteins
- AI beats humans at assessing heart health
- Should you get a nature prescription?