Blog

Gene editing "deletes" contagion mechanism of sexually transmitted infection

Laboratory tests show that the CRISPR-Cas9 technique cuts and deactivates genes essential for the survival and multiplication of the virus that causes HTLV

 Publicado: 06/11/2024 às 15:10

Text: Júlio Bernardes
Design: Diego Facundini*

Originally part of the DNA of bacteria, CRISPR works as a defense mechanism against viruses; in the gene editing technique, the Cas9 protein, associated with CRISPR, is responsible for cutting the DNA in specific locations - ”Photo montage Jornal da USP with images from: PantheraLeo1359531/Wikimedia Commons/Domínio público ; Freepik

Leia este conteúdo em PortuguêsThe CRISPR-Cas9 gene editing technique has been researched as a promising tool for the treatment of genetic diseases and infections, by “cutting” and “deleting” parts of the genome related to these disorders. Researchers from USP point out, in a review article, that the method is tested to stop the spread of HTLV, an infection transmitted by virus in sexual relations and blood transfusions, which in some cases can lead to serious diseases such as leukemia and problems in the nervous system. The studies, in the laboratory phase, show that the editing interrupts the integration of the viruses with the host cells that it uses to multiply, in addition to deactivating essential genes for its survival.

“HTLV is a sexually transmitted infection (STI) that is spread mainly through
unprotected sexual intercourse, with a higher frequency of transmission from
men to women,” researcher Wilson Domingues, first author of the article, Victor
Folgosi, and professor Jorge Casseb, from the Institute of Tropical Medicine of the Faculty of Medical Sciences of USP, who supervised the work,
explained to Jornal da USP. “Virus transmission can occur through blood
transfusions, sharing needles among drug users, and vertically, from mother to
child, during pregnancy, childbirth, or breastfeeding.”

“The majority of those infected, about 90%, remain asymptomatic throughout
their lives, contributing to silent transmission,” point out Domingues, Folgosi, and Casseb.” However, approximately 10% of those infected develop serious diseases, such as adult T-cell leukemia, uveitis, myelopathy, in addition to other conditions such as infectious dermatitis, arthritis and peripheral neuropathy.”Uveitis is the inflammation of the pigmented inner lining of the eye, the uvea; myelopathy is a disorder of the nervous system that affects the spinal cord, and peripheral neuropathy is damage to the nerves that go from the spinal cord to the limbs, such as the hands and feet.

“The goal of the article was to review and discuss, in a comprehensive way, the advances and challenges associated with the use of CRISPR/Cas9 gene editing technology in the genetic modification of retroviruses, specifically HTLV-1,”the researchers highlight.” Through the critical analysis of current studies, the publication addressed the potential of this tool for the development of new therapeutic approaches, in addition to highlighting the technical and ethical limitations that still need to be overcome for its clinical application in retroviral infections.”

According to Domingues, Folgosi and Casseb, gene editing with CRISPR-Cas9 is a revolutionary genetic engineering technique that allows for precise modification of the DNA of cells and organisms. "CRISPR works as a defense mechanism against viruses. The Cas9 protein, associated with CRISPR, is responsible for cutting DNA at specific locations,” they report. Originally, CRISPR is a part of bacterial DNA. “The technique works in the following way: an RNA guide is designed to bind to a specific sequence in the genome, and the Cas9 protein is recruited to this region, where it makes a precise cut in the DNA.”

Pesquisador tem cabelos curtos, usa bigode e uma camisa de cor clara

Wilson Domingues - Credit: CV Lattes

Pesquisador tem cabelos claros e curtos, usa barba e uma blusa de frio cor cinza

Victor Angelo Folgosi - Credit: CV Lattes

Professor tem cabelos curtos e escuros, e usa uma camiseta de cor cinza sob um jaleco branco

Jorge Simao do Rosario Casseb - Credit: CV Lattes

In the image on the left, recognition and division of the target DNA based on the single guide RNA (sgRNA); on the right, DNA repair processes known as non-homologous end joining (NHEJ) and Homology Directed Repair (HDR), along with essential components of the system, such as the sgRNA and the a) Recognition and breaks of genomic DNA b) Recognition and breaks of DNA Non-Homologous End Joining (NHEJ) Homology Directed Repair (HDR) Target DNA Insertion/Deletion Homologous DNA Precise editing protospacer adjacent motif (PAM), which allows the recognition of the target DNA - Photo: provided by the researchers.

Cell Repair

“The cell repair process can then be directed to make corrections or insert new DNA sequences,” the researchers describe. “Editing can occur through two main repair mechanisms: the specificity of non-homologous ends [not similar to each other], which can introduce loss-of-function lesions, or homology-directed repair, which allows the insertion of a new DNA sequence at the cut site,” the researchers describe.

“The CRISPR-Cas9 has various potential applications, including gene therapy for the correction of genetic mutations in hereditary diseases, modification of immune cells in cancer treatments, and combating infectious diseases such as HIV and HTLV-1 to eliminate viral DNA from host cells,” emphasize the researchers. “Furthermore, it is widely used in the creation of disease models and in the genetic improvement of plants, promoting resistance to pests and increased productivity. In biotechnology, CRISPR-Cas9 optimizes the industrial production of biopharmaceuticals and biofuels, with future potential to prevent hereditary diseases in embryos.”

According to the researchers, studies on the use of CRISPR-Cas9 gene editing to stop HTLV-1 infection are in early stages, focusing mainly on in vitro experiments and cell models tested in the laboratory. “Research has been exploring the ability of CRISPR Cas9 to disrupt the integration of HTLV-1 into the genome of host cells or to deactivate essential viral genes,” they report. “Furthermore, the difficulty in developing delivery methods for the CRISPR-Cas9 system in specific target cells, such as infected T cells, and the absence of robust clinical trials [with a large number of patients] still limit the progress towards clinical applications.”

“Future research focuses on the development of techniques that increase the efficiency and accuracy of genetic editing, such as the design of new gRNAs [RNA sequences that guide DNA cutting in the editing process] and the use of more efficient delivery methods,” observe Domingues, Folgosi and Casseb. “Therefore, although studies are advancing, further progress is still needed for CRISPR-Cas9 to be applied as a viable therapy against HTLV-1.”

The study was conducted under the supervision of Professor Jorge Casseb. The research also has the collaboration of Professor Shirley Komninakis, from Federal University of São Paulo, from the Support Center for Research in Retroviruses, based, and Professor Simone Kashima, from the Cell Therapy Center at USP. The review article “Novel approaches for HTLV-1 therapy: innovative applications of CRISPR-Cas” was published in the Journal of the Institute of Tropical Medicine of São Paulo on August 24.

More information: emails wildomingues@alumni.usp.br, with Wilson Domingues, and jcasseb@usp.br, with Professor Jorge Casseb

*Intern under the supervision of Moisés Dorado 

English version: Nexus Traduções

Política de uso 
A reprodução de matérias e fotografias é livre mediante a citação do Jornal da USP e do autor. No caso dos arquivos de áudio, deverão constar dos créditos a Rádio USP e, em sendo explicitados, os autores. Para uso de arquivos de vídeo, esses créditos deverão mencionar a TV USP e, caso estejam explicitados, os autores. Fotos devem ser creditadas como USP Imagens e o nome do fotógrafo.