All experiments were repeated 3 times. does not block RSV infection of immortalized cells, does inhibit infection of HAE cultures. This antibody was previously shown to block the interaction between the G protein and the chemokine receptor CX3CR1 and we have mapped the binding site for this antibody to the CX3C motif and its surrounding region in the G protein. We show that CX3CR1 is present on the apical surface of ciliated cells in HAE cultures Fidaxomicin and especially on the cilia. RSV infection of HAE cultures is reduced by an antibody against CX3CR1 and by mutations in the G protein CX3C motif. Additionally, mice lacking CX3CR1 are less susceptible to RSV infection. These findings demonstrate that RSV uses CX3CR1 as a cellular receptor on HAE cultures and highlight the importance of using a physiologically relevant model to study virus entry and antibody neutralization. Author Summary Respiratory syncytial virus (RSV) is the second most common infectious cause of infant death worldwide. Despite this great clinical impact, no effective antivirals or vaccines against RSV are available. Here we find that the RSV attachment (G) glycoprotein uses CX3CR1 as a receptor on primary human airway epithelial (HAE) cultures, an excellent model of RSV infection of the human lung. The G protein contains a CX3C motif and we find that this region is critical for its role in infection of HAE cultures, but not of immortalized CAGH1A cells. Furthermore, we find that antibodies against the G protein neutralize RSV infection of HAE cultures differently from immortalized cells. These insights suggest that HAE cultures should be used to quantify neutralizing antibodies, Fidaxomicin including during vaccine development, that the CX3CR1 interaction with the RSV G protein could be a target for antiviral drug development, and that the G protein should be considered Fidaxomicin for inclusion in vaccines. Introduction Respiratory syncytial virus (RSV) infects nearly every child by the age of 2 [1]. It causes severe lower respiratory disease in ~2% of these infants, making RSV infection the most frequent cause of hospitalization of infants and children in the developed world [2C4]. While supportive Fidaxomicin care successfully treats nearly all of these infants, in the developing world RSV infection causes the death of an estimated 66,000 to 199,000 children under five years of age annually [5,6]. The elderly are also susceptible to RSV disease and RSV is the second most frequent cause of excess deaths during the winter months in this population, behind influenza virus [7,8]. Despite this great Fidaxomicin clinical impact, there are currently no approved vaccines or therapeutic antiviral drugs against RSV. RSV infection has been studied mainly in immortalized cell lines, where the virion G glycoprotein uses cell-surface heparan sulfate as a receptor (HS) [9C11]. However, immortalized cell lines may not be the best model for the study of RSV entry as they differ in many aspects from the human airway epithelium model of viral interaction with the respiratory epithelium [13C18]. We previously found that RSV infects HAE cultures via the apical surface and nearly exclusively infects ciliated cells [19]. However, HAE cultures do not express detectable HS on their apical surface area [13], leading us to hypothesize a different viral receptor is in charge of RSV connection to these cells and more likely to human being airways. CX3CR1, surfactant proteins A, and annexin II are also proven to bind the G proteins and proposed to do something as mobile receptors for RSV [20C23]. Recombinant RSV missing its G gene can infect HAE ethnicities [24], albeit badly, recommending how the RSV F protein offers attachment activity also. ICAM-1, TLR4, and nucleolin have already been proposed to operate as F proteins receptors [25C27], but the majority of this ongoing function continues to be performed in immortalized cells and must be reexamined in major cultures. Here we likened the talents of soluble HS and two anti-G monoclonal antibodies (mAbs) to inhibit RSV disease, discovering that HS neutralized disease of HeLa cells however, not HAE ethnicities which the mAbs neutralized disease of HAE ethnicities superior to HeLa cells, indicating the usage of different receptors on these different cells. Among the mAbs, 131-2g, characterized as non-neutralizing in immortalized cells previously, do neutralize RSV on HAE cells. This mAb have been shown to stop G proteins binding to CX3CR1 [23]. Right here that CX3CR1 is available by us is detectable about ciliated cells.