Robin C Orozco

Genetic influences on anti-viral immunity

Allelic variation in genes associated with regulating immune responses potentially impact an individual’s response to foreign and self-antigens. With the increase in genome wide association (GWAS) studies, more mutations in immune-related genes are being associated with protective or pathologic consequences during disease. Importantly, it is being appreciated that allelic variations in the coding region, which may alter a protein’s function, can have a large impact on disease. However, many of the cellular and molecular mechanisms by which these mutations influence disease remain largely unknown. To address this, we use a variety of transgenic murine models to dissect the molecular and cellular mechanisms a particular mutation is impacting viral replication, immune cell function, and viral associated pathologies. Currently, the lab studies the contribution of the common pro-autoimmune allele of PTPN22 (rs2476601) in regulating the balance between protection and pathology during virus infection.

Mice expressing the Ptpn22 pro-autoimmune allele clear chronic virus infection.

In humans, PTPN22, encodes the encodes the phosphatase Lymphoid Protein (Lyp). Often, researchers, including our lab, uses Ptpn22 knock out mice, which lack expression of the murine Lyp ortholog PEP. We also have mice, which were generated using CRISPR/Cas9, that express the pro-autoimmune allele version of Ptpn22 instead of the wildtype allele of the gene. We have observed that mice lacking Ptpn22 or express the pro-autoimmune allele variant of Ptpn22, are able to clear the chronic virus Lymphocytic choriomeningitis virus clone 13 (LCMV-cl13), unlike the mice with the wildtype Ptpn22. This is associated with enhanced T cell and myeloid cell function during virus infection. Projects in the lab aim to better define the molecular and cellular mechanisms the pro-autoimmune allele of Ptpn22 alters CD4 T cell, CD8 T cell, dendritic cell, and macrophage responses during virus infection. Further, we aim to determine which of these immune cell differences are necessary and/or sufficient for LCMV-cl13 clearance.

Establish new systems to better test the effects of the Ptpn22 pro-autoimmune allele during disease.

Ptpn22 is expressed in all immune cells and has differing biological effects in each immune cell subset. In T cells, Ptpn22 tempers TCR activation. In contrast, Ptpn22 promotes Type I interferon production in myeloid cells. As such, studying the cell specific intrinsic effects of the Ptpn22 pro-autoimmune allele in the presence of other immune cells provides a unique challenge. Currently, in vivo, we are limited to studying the cell specific effect of the Ptpn22 pro-autoimmune allele using cell transfer methods. While still powerful, these methods have their limitations. Another approach, which we do employ, is to use a cell specific Ptpn22 conditional knock out model. However, this approach studies the knockout, not the alternative allele, which can have differing consequences. My lab aims to develop new tools to study the cellular and molecular effects of Ptpn22 alternative allele both in vivo and in vitro.

The anti-viral role of the Ptpn22 alternative allele in other viral infections and viral associated pathologies.

To date little research has been done studying Ptpn22 and its pro-autoimmune allele in non-LCMV viral infections. My lab aims to elucidate how the Ptpn22 pro-autoimmune allele may influence viral tropism, replication, anti-viral immunity, and viral associated pathologies outside of LCMV infection using in vivo and in vitro systems. A viral associated pathology of interest in our lab is the neuroinflammatory effects during CNS virus infection. Left uncontrolled CNS viral infection can lead to neuronal death and brain pathologies. However, if the immune response is too active during the process of clearing virus, this can lead to immune mediated brain pathologies. Given the wide range of immune functions PTPN22 regulates, this gene may be pivotal in the delicate balance between the anti-viral immune response being strong enough to control virus infection or too strong, resulting in immunopathology, in the brain.

Keywords: Immunology, Anti-viral Immunity, Virus Infection, Allelic Variation, Neuroinflammation, PTPN22

Some technologies used in the lab: Flow Cytometry, Single Cell RNA Sequencing, Transgenic Murine Models, Cell Culture, Microscopy