Ebolavirus (EBOV) is a negative sense, single stranded RNA virus that causes Ebola hemorrhagic fever. This disease causes substantial morbidity and mortality in humans, with death occurring in 50-90% of cases. Despite years of intensive research, much of the molecular mechanism underlying the entry of EBOV remains unknown. We performed a bioinformatics screen to identify novel entry cofactors by correlating mRNA expression in a panel of human cancer cell lines with permissivity to the EBOV entry glycoprotein. This assay identified several known EBOV entry cofactors such as actin and the tyrosine kinase Axl. In addition, several genes involved in macropinocytosis and endosomal maturation were also correlated with EBOV permissivity. Subsequent evaluation of plasma membrane proteins correlated by this screen showed T-cell immunoglobulin and mucin domain-1 (TIM-1) mRNA expression correlated extremely well with EBOV pseudovirion transduction. Depletion of TIM-1 from highly-permissive cells inhibits EBOV pseudovirion transduction. Conversely, expression of TIM-1 in poorly-permissive cells significantly and specifically enhances EBOV pseudovirion transduction and infection. TIM-1 binds to EBOV GP and this binding is important in the initial interaction between the virus and the host cell. ARD5, a TIM-1 mAb, significantly inhibits EBOV GP-mediated entry into several cell lines and primary human airway epithelia in a dose and time-dependent manner. Therefore, TIM-1 is the first receptor identified for EBOV. Additionally, AMP-activated protein kinase (AMPK) mRNA correlated strongly with EBOV pseudovirion transduction. Compound C, a specific AMPK inhibitor, inhibited EBOV pseudovirion transduction and infection in a time and dose-dependent manner into several cell lines and primary human monocyte derived macrophages. Mouse embryonic fibroblasts (MEFs) lacking functional AMPK were significantly less permissive to EBOV GP-mediated infection that WT MEFs. Visualization of virus entry into these cells revealed that EBOV causes actin polymerization independently of AMPK, but AMPK-/- cells do not form lamellipodia in the presence of EBOV and, consequently, cannot internalize virus into cells by macropinocytosis.

Human metapneumovirus (HMPV) is a worldwide respiratory pathogen that belongs to the paramyxovirus family of enveloped viruses and affects primarily the pediatric, geriatric, and immunocompromised populations. Despite its prevalence and importance to human health, no therapies are available against this pathogen. For paramyxoviruses, it is believed that infection starts by attachment of the virus to the surface of the cell through the viral attachment protein followed by fusion between the viral and cellular membranes, a process mediated by the fusion (F) protein at the plasma membrane and at neutral pH. Previous work showed that HMPV infection can occur in the absence of the attachment protein and membrane fusion triggered by the F protein can be promoted by low pH. The work presented here are significant advances in our understanding of the entry process of HMPV. We confirmed that the F protein has receptorbinding functions and identified the cellular binding partner to be heparan sulfate proteoglycans (HSPGs). Additionally, we provide evidence that electrostatic interactions at two different regions play important roles for the proper folding, stability, and low pH triggering of the HMPV F protein. We confirmed the hypothesis that protonation of H435 is important for HMPV F triggering and provide additional evidence that the entry of HMPV may be occurring through endocytosis. Therefore, we hypothesize that HMPV entry occurs through endocytosis after viral binding to HSPGs through the F protein and membrane fusion occurs in an acidified compartment.