CRISPR gene editing technology offers a path to a possible cure
The ability for HIV to integrate its genome into a host’s DNA makes it very difficult to eliminate, leaving people with HIV reliant on lifelong antiretroviral therapy to prevent the virus from reactivating. After entering an immune cell, HIV’s single-stranded RNA genome reverse-transcribes into double-stranded DNA. This lets the virus’ genome establish itself in the cell’s nuclear DNA, allowing constant replenishing of virus particles.
But preliminary findings presented showed how gene editing could be used to precisely alter these genomes, which would be a significant breakthrough to eliminating HIV from the body.
The research involves CRISPR technology, which won its inventors a Nobel Prize in 2020. CRISPR slices up genes of invading viruses and it can be directed to guide DNA to make cuts at specific genomic sequences to remove and even replace those sequences inside living cells, and it’s the basis of new gene editing treatments that promise to cure sickle cell disease. A team of researchers from Amsterdam Medical University in the Netherlands and the Paul Ehrlich Institute in Germany showed how it does the same for HIV. Their results presented at ESCMID Global showed how CRISPR-Cas gene editing technology acts like molecular “scissors” to eliminate the HIV virus from infected cells in the laboratory using guide RNA (gRNA) to tell CRISPR-Cas exactly where to cut at designated spots on the virus genome.
The authors emphasize that their work represents a proof of concept rather than a cure. However, they say it could lead to a cure that would inactivate diverse HIV strains in multiple parts of the body. “The studies present a significant breakthrough in the search for an HIV cure,” said lead author Elena Herrera-Carrillo, PhD, an associate professor in the Department of Medical Microbiology, Laboratory of Experimental Virology at the University of Amsterdam Medical Center.
The authors shared their evaluation of how well two CRISPR-Cas systems, saCas9 and cjCas, treated CD4+ T cells infected with HIV. SaCas9, they said, was highly effective in inactivating HIV with a single gRNA and in cutting out the viral DNA with two gRNAs. Researchers used CRISPR-Cas and two gRNAs against “conserved” HIV sequences, which are parts of the virus genome that stay the same across all known HIV strains. The idea is that by focusing on conserved sections, a broad-spectrum therapy could be developed, one that combats multiple HIV variants.
The team faced a logistical obstacle: the size of the “vehicle,” or vector, that was used for transporting the cassette encoding the therapeutic CRISPR-Cas reagents into the cells was too large to be used in a clinical setting—think of stuffing a compact car full of luggage for a long journey. The researchers found a way of downsizing the “luggage” (the cassette) for easier transport. They were also able to target “hidden” HIV reservoir cells by focusing on proteins found on the surfaces of the cells (CD4+ and CD32a+).
Researchers say their goal is targeting reservoir cells and to avoid delivering CRISPR-Cas into non-reservoir cells to make the system as safe as possible for clinical application. The team says they’ll also explore how to effectively target HIV in all the different types of cells and tissues, each with unique environments and characteristics.
Obstacles to PrEP use in Europe and Central Asia
World Health Organization (WHO) guidelines recommend PrEP for key populations considered especially vulnerable to acquiring HIV, including sex workers, men who have sex with men (MSM), people who inject drugs (PWID), incarcerated people, and transgender and gender diverse people.
However, the implementation of PrEP throughout Europe and Central Asia (ECA) varies significantly by country and these key populations face significant obstacles in obtaining PrEP, according to WHO researcher Viatcheslav Grankov, who presented some disappointing PrEP uptake numbers at a symposium at ESCMID. The United Kingdom, France, Germany and Spain, he reported, account for 77% of total PrEP usage across the ECA region. In other countries, Grankov said, including Armenia, Lithuania and Tajikistan, “PrEP usage is too low to have any meaningful impact at the public health level.”
Grankov pointed out some reasons why this is the case. In many countries, the law prohibits undocumented migrants, incarcerated people and PWID from being eligible for PrEP. Even in areas where a larger number of people can access PrEP, usage is poor. For example, a recent study from France, one of the higher PrEP uptake countries, concluded that less than a quarter of MSMs who could benefit from PrEP are accessing it.
In 2022, the WHO released guidelines recommending that people who may be especially vulnerable to acquiring HIV should have access to CAB-LA, stating that CAB-LA as PrEP could help close the gaps in HIV prevention in ECA. The reasoning is that CAB-LA could improve adherence and reduce stigma associated with oral PrEP. But Grankov suggested that unless countries eliminate some of the hurdles that have hampered use of oral PrEP, uptake of CAB-LA will also be minimal.
Grankov stated that across low-income and middle-income countries, long-acting injectable Cabenuva should be, but not always is, reasonably priced. But cost isn’t the only obstacle facing vulnerable people in these countries. “In many countries, PrEP is still provided as a pilot project, mainly for MSM, and the number of PrEP clients is very limited. In many cases, [prevention] services [are] highly medicalized, which creates additional barriers in a stigmatized environment.” Other issues, Grankov said, include excessive clinical monitoring, which are not in line with WHO recommendations, and even requirements to provide passport data in order to receive PrEP. “And of course, insufficient awareness and misconceptions among target populations, and even low knowledge of PrEP among providers affects retention and continuation of PrEP.”
Previously incarcerated people living with HIV are highly vulnerable to dropping out of care, study says
One vulnerable population, incarcerated people, was the topic of an ESCMID presentation by Maximo Brito, MD, MPH, a professor at the University of Illinois in Chicago. People who have been previously incarcerated, he pointed out, are especially vulnerable to being lost to care soon after being released. Some reasons include poverty, poor mental health, lack of support, and lack of employment and housing.
“Retention remains suboptimal for many HIV programs and effective strategies to retain and re-engage patients living with HIV are urgently needed,” Dr. Brito said.
He indicated how urgently such strategies are needed by sharing data from a quality improvement implementation project in which researchers estimated how many patients living with HIV dropped out of care, who they were and whether they could be re-engaged. Results were taken from six HIV primary care settings in the University of Illinois Community Clinic Network that serve PLWH in Chicago. Researchers reviewed medical records for all patients at the clinics to determine who tested positive for HIV but had not attended an HIV care appointment within the past year and were not on ART.
Outreach workers used phone calls, letters (mail and email), home visits and internet searches to contact this group of patients; once they located a patient—if they located the patient—they offered to help re-engage with treatment services and restart HIV care. Of 491 PLWH identified in the network, most were male (89%) and Black (63%) or Hispanic (19%), with an average age of 41 years. A small percentage had transferred to other clinics, been re-incarcerated, or had died. That left a small but significant number, 85 out of 491, who were likely alive but out of care, including 33 who were previously incarcerated.
Of the group lost to care, communication presented a barrier: three-quarters could not be contacted due to an invalid phone number, 16% did not answer and 2% were contacted but declined to return to care. Only five patients (6%) were successfully located, and of these, only one returned to care.
Dr. Brito said that these discouraging numbers suggest that interventions must be made prior to release from corrections.
“We need dedicated resources to optimize people’s HIV care while they are in prison and to link them to community-based care upon release,” he said. He added that case management, health insurance and treatment for addiction and mental illness—again, before release—will help incarcerated PWH remain treatment adherent, virally suppressed, and, as a side benefit, reduce recidivism.
All ESCMID Global 2024 sessions are available on the conference website until October 30, 2024. GO TO eccmid.org/online-platform.
LARRY BUHL is a multimedia journalist based in Los Angeles. He has covered HIV/AIDS and other infectious diseases for more than two decades. In addition to POSITIVELY AWARE, he is a regular contributor to TheBody.com, Everyday Health and capitalandmain.com. His work has appeared in USA Today, Salon, Undark, KQED, The New York Times and others.