Abstract
AbstractThe severity of host tissue injury and pathology during viral disease is a major determinant of disease outcomes for most human viral infections. It’s now been shown that viral disease phenotypes are determined by both viral activity and host responses to infection. In most respiratory viral infections including Influenza A Virus (IAV, PR8), the disease pathology is defined by both the cytotoxic effects of prolonged viral replication and virion production and the host’s immune response towards the respiratory tract. Next, beta-herpesvirus human cytomegalovirus (HCMV) is the leading cause of congenital viral-induced birth defects in humans. These birth defects include microcephaly, sensorineural hearing loss, and cognitive impairment. The process through which the developing fetus incurs these neurological defects is still poorly understood but thought to occur through the combination of host inflammatory response and pathologic regulation of host cell functions by the virus. Previously my lab had established a murine model for studying the differences in disease outcome of pre-infection with a mild respiratory pathogen Rhinovirus (RV) on subsequent infection with a more lethal virus PR8 (RV/PR8) when compared to naïve mice infected with PR8 alone (Mock/PR8). In our mouse model, we observed that coinfection of RV with PR8 reduced disease severity when compared to mice infected with PR8 alone. To study the neurological changes incurred by a developing brain as a result of congenital HCMV infection we also established a 3D in vitro brain organoid model utilizing HCMV-infected induced pluripotent stem cells. Utilizing this model, we previously showed that HCMV-infected brain organoids recapitulated multiple developmental and structural pathologies associated with congenital HCMV-infected fetuses. In this dissertation, we strove to uncover a possible mechanism through which RV protects PR8-infected mice from severe disease and explore the role of HCMV targeted downregulation of key basement membrane (BM) protein nidogen-1(NID1) in our 3D brain organoid model. To uncover a mechanism of RV-mediated protection in our model, we blocked a key antiviral pathway, type I interferon (IFN) response, early during the time course of infection in RV/PR8-coinfected mice. We analyzed the lung samples and observed that blocking type I IFN response in coinfected mice, reduced RV-mediated protection and induced excessive neutrophil recruitment, and delayed clearance of PR8. These results concluded that RV-mediated protection of PR8 coinfected mice is in part conducted through the type I IFN signaling pathway. Finally, in our 3D brain organoid model, to uncover the paths through which infected organoids develop aberrant cortical structures we analyzed the neural tube in vitro model, neural rosettes. We observed that infected rosettes incurred multiple structural defects and histopathologies. HCMV-infected rosettes also expressed diminished levels of BM protein NID1. CRISPR Cas9 mediated knockdown of NID1 in our organoid model reproduced many of the pathological features associated with HCMV-infected organoids and rosettes. In conclusion, we have been able to show that the targeted downregulation of NID1 could contribute to the disease outcome of congenital HCMV disease.