gene therapy

Silencing the Immunogenicity of AAV Vectors 

Posted on by Jordan Nutting

Recombinant adeno-associated viral (AAV) vectors are an appealing delivery strategy for in vivo gene therapy but face a formidable challenge: avoiding detection by an ever-watchful immune system (1,2). Efforts to compensate for the immune response to these virus particles have included immunosuppressive drugs and engineering the AAV vector to be especially potent to minimize its effective dosage. These methods, however, come with their own challenges and do not directly solve for the propensity of AAV vectors to induce immune responses.  

A recent study introduced a new approach to reduce the inherent immunogenicity of AAV vectors (2). Researchers strategically swapped out amino acids in the AAV capsid to remove the specific sequences recognized by T-cells that elicit the most pronounced immune response. As a result, they significantly reduced T-cell mediated immunogenicity and toxicity of the AAV vector without compromising its performance.  

Read on to get more of the study details, which include the use of NanoLuc® luciferase and Nano-Glo® Fluorofurimazine In Vivo Substrate for in vivo bioluminescent imaging of the AAV variants’ distribution and transduction efficiency in mice. 

A teal colored ribbon model of a AAV virus capsid floats against a black background.
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Discovery of Protein Involved in TDP-43 Cytoplasmic Re-Localization Points to Potential Gene Therapy for ALS and FTD

Posted on by Kelly Grooms
A mouse stands on test tubes next to graphic of DNA double helix.

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are fatal and rapidly progress as neurodegenerative diseases. While inherited mutations can cause both conditions, they mostly appear sporadically in individuals without a known family history. Despite affecting different neurons, both diseases share a common hallmark: the pathogenic buildup of abnormal nuclear TAR-binding protein 43 (TDP-43) in the cytoplasm of affected motor neuron cells. Current theories propose that this cytoplasmic re-localization triggers toxic phosphorylation and fragmentation of TDP-43. Concurrently, a decrease of TDP-43 in the nucleus diminishes TDP-43-related physiological nuclear functions, contributing to the diseases’ progression (1).

Although this cytoplasmic accumulation of TDP-43 plays a significant role in the pathogenesis of ALS and FTD, the cellular mechanisms involved in the re-localization of TDP-43 to the cytoplasm is not known (2). A team of Australian neuroscientists led by Dr. Lars Ittner believe that they have found part of the answer for sporadic forms of the diseases. They identified novel interactions between pathogenic or dysfunctional forms of TDP-43 and the 14.3.3ɵ isoform of the cytoplasmic protein 14-3-3. By targeting this interaction with an AAV-based gene therapy vector, they were able to block and even partially reverse neurodegeneration in ALS/FTD mouse models.  

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Addressing the Problem of Dosing in Gene Therapy

Posted on by AnnaKay Kruger

One key obstacle to crafting effective gene therapies is the ability to tailor dosing according to a patient’s needs. This can be tricky because even if protein production is successful, staying within the therapeutic window is paramount—too much of a protein could be toxic, and too little will not produce the desired effect. This balance is difficult to achieve with current technologies. In a study recently published in Nature Biotechnology, researchers at Baylor College of Medicine investigated a possible solution to this problem, engineering a molecular “on/off” switch that could regulate gene expression and maintain protein production at dose-dependent, therapeutic levels.

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Transformative Gene Therapies Greenlit for Sickle Cell Disease

Posted on by AnnaKay Kruger
In sickle cell anemia, red bloods cells elongate into an abnormal “sickled” shape

Sickle cell disease is a debilitating blood disorder that causes recurrent pain crises and severe health effects, and can drastically impact quality of life. Recently, Vertex Pharmaceuticals and CRISPR Therapeutics introduced Casgevy, or exa-cel, a novel form of gene therapy that could radically change the management of sickle cell disease. On the heels of exa-cel’s approval in Britain, this groundbreaking therapy was also recently approved in the U.S.

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A One-Two Punch to Knock Out HIV

Posted on by Sara Klink
This schematic of HIV life cycle summarizes years of research to understand HIV and get to a potential cure for HIV infection
HIV-1 lifecycle illustration. Copyright Promega Corporation.

Scientists investigating the human immunodeficiency virus (HIV) have learned much about the retrovirus’s lifecycle, but their ultimate goals were to discover a cure and prevent infection. In the decades since HIV was discovered, basic research and pharmaceutical drug development have expanded the antiviral toolbox, but these HIV treatments do not provide a functional cure, only manage the infection. However, two techniques may offer a potential cure for HIV infection using CRISPR and a possible vaccine using mRNA.

CRISPR-Based Therapy May Cure HIV Infection

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Twisted CRISPR: A Novel Activation Strategy to Treat Genetically Driven Obesity

Posted on by Ken Doyle

Two Is Better Than One

Obese and normal mouse

Redundancy equips us to survive. We have more than one lung or one kidney for a reason—if one organ in a pair gets damaged, we can still manage if the other is functional. At the cellular level, we have two copies of each chromosome in every non-germline cell. Each copy was inherited originally from a single sperm and ovum, which are “haploid” cells. Consequently, there are two copies of any given gene in non-germline “diploid” cells. In many cases, should one copy of a gene be damaged, the cell can still survive with the other, functional copy of a gene. In plants, this redundancy is common, and many plants exhibit polyploidy. In an extreme example of polyploidy, the large (by bacterial standards) but otherwise unassuming species Epulopiscium contains tens of thousands of copies of its genome.

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A Crash Course in CRISPR

Posted on by Darcia Schweitzer

CRISPR is a hot topic right now, and rightly so—it is revolutionizing research that relies on editing genes. But what exactly is CRISPR? How does it work? Why is everyone so interested in using it? Today’s blog is a beginner’s guide on how CRISPR works with an overview of some new applications of this technology for those familiar with CRISPR.

Introduction to CRISPR/Cas9

27850283-June-13-CRISPR-image-WEB

Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) were discovered in 1987, but it took 30 years before scientists identified their function. CRISPRs are a special kind of repeating DNA sequence that bacteria have as part of their “immune” system against invading nucleic acids from viruses and other bacteria. Over time, the genetic material from these invaders can be incorporated into the bacterial genome as a CRISPR and used to target specific sequences found in foreign genomes.

CRISPRs are part of a system within a bacterium that requires a nuclease (e.g. Cas9), a single guide RNA (sgRNA) and a tracrRNA. The tracrRNA recruits Cas9, while sgRNA binds to Cas9 and guides it to the corresponding DNA sequence of the invading genome. Cas9 then cuts the DNA, creating a double-stranded break that disables its function. Bacteria use a Protospacer Adjacent Motif, or PAM, sequence near the target sequence to distinguish between self and non-self and protect their own DNA.

While this system is an effective method of protection for bacteria, CRISPR/Cas9 has been manipulated in order to perform gene editing in a lab (click here for a video about CRISPR). First, the tracrRNA and sgRNA are combined into a single molecule. Then the sequence of the guide portion of this RNA is changed to match the target sequence. Using this engineered sgRNA along with Cas9 will result in a double-stranded break (DSB) in the target DNA sequence, provided the target sequence is adjacent to a compatible PAM sequence.

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