CRISPR/Cas9-Mediated Genetic Engineering: Is CD163 an Entry Mediator for PRRSv Infection?

Porcine reproductive and respiratory syndrome virus (PRRSv) costs swine producers in North America some $800M annually. The primary target of the virus is alveolar macrophages. One model of viral entry suggests an initial association of PRRSv with heparin sulfate, followed by attachment to SIGLEC1. The SIGLEC1 bound virus is then endocytosed. Within the endosome CD163 then facilitates unpackaging of the viral genome for infection of the cell. CD163 is a member of the scavenger receptor cysteine-rich (SRCR) superfamily. Based on in vitro studies SRCR domain 5 of the protein is the domain responsible for unpackaging and release of the viral genome.

Previously we created pigs that are deficient in SIGLEC1. However, after viral challenge there was no difference in development and progression of disease between SIGLEC1-/- and Wildtype pigs. To determine if CD163 is an entry mediator we created mutations in CD163 on a Wildtype background and on the SIGLEC1-/- background. These mutations should permit us to determine if CD163 alone, or in combination with SIGLEC1 mediate PRRSv entry and infectivity. Additionally, if CD163 mediates infectivity, we created mutations in CD163 that delete domain 5, delete domains 5&6, delete part of domain 5, or create a partial domain 5 swap between ssCD163 and hCD163L. A PRRS viral challenge of the offspring of these founder pigs should definitively determine if the above model for infection is accurate. Characterization of the molecular interactions between PRRSv and the host may lead to treatments and therapies to prevent or alleviate the effects of infection.