Therapeutic strategies for the prevention and treatment of Congenital Cytomegalovirus Disease
BACKGROUND: Congenital cytomegalovirus (HCMV) is the leading non‐genetic cause of fetal malformation in developed countries. Congenital HCMV causes lifelong clinical sequelae in children including mental disability, sensorineural hearing loss, vision loss, intrauterine growth restriction, microcephaly, motor defects and in severe cases causes fetal and neonatal death. GAP: Fetal injury is caused by direct HCMV cytopathic damage to the fetus following maternofetal transmission via the placenta or indirectly by dysregulating normal placental development and function. Despite the clinical and social importance of congenital HCMV, there are currently no licensed therapeutics for use during pregnancy to prevent fetal injury primarily due to drug toxicity and limited evidence for therapeutic efficacy. HYPOTHESIS: Inhibiting HCMV replication in the placenta will reduce vertical transmission during pregnancy and prevent direct and indirect viral injury to the developing fetus. The in vitro correlates of new experimental in vivo anti‐HCMV therapeutics will be modeled in our established human placental models to provide urgently needed preclinical data for potential use during pregnancy. METHODS: Human ex vivo placental explant histocultures and placental cell culture models will be utilized to examine the efficacy and safety profiles of experimental antivirals in response to HCMV infection. A range of molecular biology techniques will be utilized including; qRT‐PCR, plaque assay, western blot, immunofluorescence, immunohistochemistry, ELISA, and cytotoxicity/functional assays. RESULTS: In this study aciclovir, and the HCMV‐specific antivirals letermovir, maribavir and cidofovir were compared with ganciclovir, for antiviral effects in model systems of pregnancy. HCMV‐infected placental trophoblast cultures at 7 days post infection (dpi) showed an EC50 of 21µM for aciclovir, 0.0007µM for letermovir, 0.11µM for maribavir, and 0.29µM for cidofovir, relative to 0.42µM for ganciclovir. Antivirals added at 10µM showed no cytotoxic effects and did not affect trophoblast cell proliferation (p>0.9999). Multiple‐round HCMV replication measured at 7dpi showed letermovir, maribavir, and cidofovir treatment inhibited immediateearly, early and true late viral protein expression on western blot. Antiviral treatment of HCMVinfected placental explants showed significant inhibition (p<0.05) of viral replication with letermovir (83.3%), maribavir (83.6%), cidofovir (89.3%), and ganciclovir (82.4%), but not aciclovir (p>0.9999). These data were recently published in Antimicrobial Agents and Chemotherapy (Hamilton ST, Marschall M, Rawlinson WD (2021). Investigational antiviral therapy models for the prevention and treatment of congenital cytomegalovirus infection during pregnancy. Antimicrobial Agents and Chemotherapy. 65(1):e01627‐20. PubMed ID: 33077661) IMPACT: This investigation provides invaluable preclinical data on the efficacy and safety profiles of experimental anti‐HCMV therapeutics to prevent and treat congenital HCMV disease. The findings of this study will immediately influence future directions in therapeutics for HCMV affected pregnancies and provide strong impact against one of the global leading causes of disability in the newborn. Website Link: http://www.virologyresearch.unsw.edu.au/people/scientists/dr‐stuart‐hamilton/Optional/Additional Comments This work is partly supported by the Australian National Health and Medical Research Council (Hamilton – APP1127717).