1st Place


Adele Peng

Thomas Jefferson High School for Science and Technology 
Teacher: Aubrie Holman


Since the discovery of DNA’s structure, scientists have been attempting to decrypt life’s code, employing ‘reverse genetics’ to analyze functions of genes located in DNA sequences. This approach involves knocking out certain genes or replacing sequences within the gene to determine how cells behave with a different expression of the gene of interest. As a result, specialized zinc finger nucleases (ZFNs) have been developed. Unlike viral vectors, which temporarily alter gene expression by integrating their DNA randomly into the genome, ZFNs allow for targeted gene correction to permanently modify the targeted sequence (Carroll, 2008; Carroll, 2011). ZFNs are being investigated as gene therapy agents for numerous gene-related diseases, including HIV/AIDS (human immunodeficiency virus, which causes acquired immunodeficiency syndrome), a disorder afflicting 36.7 million people worldwide as of 2016 ("Global Statistics," 2016)… 

…Zinc finger nucleases are hybrid enzyme pairs that simultaneously recognize and edit desired sites in an organism’s genome. ZFNs are produced based on the observation that the DNA recognition domains of the Fokl restriction enzyme act independently of its DNA cleavage domain and can be manipulated without affecting the ability of the enzyme to create a double stranded break in the target DNA sequence (Carroll, 2008; Carroll, 2011). By substituting separate ‘zinc fingers’ each recognizing a set of 3 DNA base pairs for the wild type Fokl recognition domain in different combinations, engineered ZFNs can modify desired genes with high specificity and frequency (Miller et al., 2007)...

…HIV attacks the immune system’s CD4+ T lymphocytes, entering cells using chemokine co-receptors CCR5 and CXC4. CCR5 is expressed on T cell surfaces and binds chemokine ligands (signals used to communicate inflammation and cause immune cell migration)…

…A 32-nucleotide deletion in the CCR5 gene creates a dysfunctional form of CCR5 that cannot be recognized by the virus, allowing individuals homozygous for the mutant allele to possess natural HIV-1 resistance (Lehner, 2002)… 

…Inspired by the CCR5∆32 mutation, Perez et al. (2008) engineered a set of four-finger ZFN dimers targeting the CCR5 co-receptor gene, mimicking the natural mutation by inducing NHEJ and effectively knocking out the CCR5 gene. This would prevent CCR5-tropic HIV-1 viruses from infecting healthy T cells. Results were promising: of the treated T cell populations in vitro, 28-30% of cells exhibited CCR5 disruption of at least one allele, and of these heterozygotes, 33% of the mutant clones were homozygous for the ZFN-disrupted allele. Upon HIV-1 infection, over 50% of CCR5 alleles in culture were found to be ZFN-disrupted, indicating that T cells with the mutation exhibited a survival advantage when challenged by infection…