The salivary glands represent a major site of cytomegalovirus replication and transmission to other hosts. Despite control of viral infection by strong T cell responses in visceral organs cytomegalovirus replication continues in the salivary glands of mice, suggesting that the virus exploits the mucosal microenvironment. Here, we show that T cell immunity in the salivary glands is limited by the induction of CD4 T cells expressing the regulatory cytokine interleukin (IL)-10. Blockade of IL-10 receptor (IL-10R) with an antagonist antibody dramatically reduced viral load in the salivary glands, but not in the spleen. The mucosa-specific protection afforded by IL-10R blockade was associated with an increased accumulation of CD4 T cells expressing interferon γ, suggesting that IL-10R signaling limits effector T cell differentiation. Consistent with this, an agonist antibody targeting the tumor necrosis factor receptor superfamily member OX40 (TNFRSF4) enhanced effector T cell differentiation and increased the number of interferon γ–producing T cells, thus limiting virus replication in the salivary glands. Collectively, the results indicate that modulating effector T cell differentiation can counteract pathogen exploitation of the mucosa, thus limiting persistent virus replication and transmission.

GS-5806 is a novel, orally bioavailable RSV fusion inhibitor discovered following a lead optimization campaign on a screening hit. The oral absorption properties were optimized by converting to the pyrazolo[1,5-a]-pyrimidine heterocycle, while potency, metabolic, and physicochemical properties were optimized by introducing the para-chloro and aminopyrrolidine groups. A mean EC50 = 0.43 nM was found toward a panel of 75 RSV A and B clinical isolates and dose-dependent antiviral efficacy in the cotton rat model of RSV infection. Oral bioavailability in preclinical species ranged from 46 to 100%, with evidence of efficient penetration into lung tissue. In healthy human volunteers experimentally infected with RSV, a potent antiviral effect was observed with a mean 4.2 log10 reduction in peak viral load and a significant reduction in disease severity compared to placebo. In conclusion, a potent, once daily, oral RSV fusion inhibitor with the potential to treat RSV infection in infants and adults is reported.

BackgroundThe SCID-hu Thy/Liv mouse model of HIV-1 infection is a useful platform for the preclinical evaluation of antiviral efficacy in vivo. We performed this study to validate the model with representatives of all four classes of licensed antiretrovirals.Methodology/Principal FindingsEndpoint analyses for quantification of Thy/Liv implant viral load included ELISA for cell-associated p24, branched DNA assay for HIV-1 RNA, and detection of infected thymocytes by intracellular staining for Gag-p24. Antiviral protection from HIV-1-mediated thymocyte depletion was assessed by multicolor flow cytometric analysis of thymocyte subpopulations based on surface expression of CD3, CD4, and CD8. These mice can be productively infected with molecular clones of HIV-1 (e.g., the X4 clone NL4-3) as well as with primary R5 and R5X4 isolates. To determine whether results in this model are concordant with those found in humans, we performed direct comparisons of two drugs in the same class, each of which has known potency and dosing levels in humans. Here we show that second-generation antiretrovirals were, as expected, more potent than their first-generation predecessors: emtricitabine was more potent than lamivudine, efavirenz was more potent than nevirapine, and atazanavir was more potent than indinavir. After interspecies pharmacodynamic scaling, the dose ranges found to inhibit viral replication in the SCID-hu Thy/Liv mouse were similar to those used in humans. Moreover, HIV-1 replication in these mice was genetically stable; treatment of the mice with lamivudine did not result in the M184V substitution in reverse transcriptase, and the multidrug-resistant NY index case HIV-1 retained its drug-resistance substitutions.ConclusionGiven the fidelity of such comparisons, we conclude that this highly reproducible mouse model is likely to predict clinical antiviral efficacy in humans.

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections in infants and young children. In addition, RSV causes significant morbidity and mortality in hospitalized elderly and immunocompromised patients. Currently, only palivizumab, a monoclonal antibody against the RSV fusion (F) protein, and inhaled ribavirin are approved for the prophylactic and therapeutic treatment of RSV, respectively. Therefore, there is a clinical need for safe and effective therapeutic agents for RSV infections. H uman respiratory syncytial virus (RSV) is the predominant cause of bronchiolitis and pneumonia in infants and young children (1). Those most at risk for severe RSV disease are infants born prematurely (Ͻ34 weeks gestation) or less than 6 weeks of age and children with underlying medical conditions, such as bronchopulmonary dysplasia, congenital heart disease, or immunodeficiency (1-3). Severe RSV infection in children less than 1 year old is associated with recurrent wheezing and asthma later in life (4). RSV is also an important cause of lower respiratory tract infections in immunocompromised individuals and the elderly, often resulting in significant morbidity and mortality (5-7).Currently, there is no effective vaccine available for the prevention of RSV infection. Current approved therapeutic options for RSV include palivizumab (Synagis), a neutralizing monoclonal antibody against the RSV F protein, and inhaled ribavirin (Virazole), a broad-spectrum nucleoside analog targeting RNA transcription/replication. Palivizumab is approved for the prophylactic treatment of pediatric patients at high risk of developing severe RSV infection, whereas ribavirin is the only antiviral approved for RSV treatment (8). However, contradictory observations regarding the efficacy, concerns about tolerability, and challenging routes of administration have significantly limited the use of inhaled ribavirin (9). Therefore, there is a clinical need for a safe and effective therapeutic for pediatric and adult RSV infections. Recently, a number of small-molecule RSV inhibitors have been identified. These inhibitors partition into three categories based upon their different mechanisms of action: (i) nucleocapsid protein inhibitors (RSV604) (10), (ii) RNA-dependent RNA polymerase inhibitors (YM-53403, BI-D, and ALS-8176) (11-13), and (iii) fusion inhibitors (VP-14637, TMC-353121, BMS-433771, and GS-5806) (14-17). Among these, RSV fusion inhibitors are the most potent class in vitro and exhibit efficacy in animal models of RSV infection (14-17). Currently, only ALS-8176 and GS-5806 are being clinically developed for the treatment of RSV infection.RSV is an enveloped virus with a negative-sense, single-stranded RNA genome. RSV infection is initiated by attachment of the viral glycoprotein (G) to the cell surface. Following attachment, the RSV fusion protein (F) mediates fusion of the viral and cellular membranes, allowing the viral replication complex to enter the cell. Spread of RSV infection occurs either through cel...

Influenza viruses are responsible for seasonal epidemics and occasional pandemics which cause significant morbidity and mortality. Despite available vaccines, only partial protection is achieved. Currently, there are two classes of widely approved anti-influenza drugs: M2 ion channel blockers and neuraminidase inhibitors. However, the worldwide spread of drug-resistant influenza strains poses an urgent need for novel antiviral drugs, particularly with a different mechanism of action. Favipiravir (T-705), a broad-spectrum antiviral agent, has shown potent anti-influenza activity in cell-based assays, and its riboside (2) triphosphate inhibited influenza polymerase. In one of our approaches to treat influenza infection, we designed, prepared, and tested a series of C-nucleoside analogues, which have an analogy to 2 and were expected to act by a similar antiviral mechanism as favipiravir. Compound 3c of this report exhibited potent inhibition of influenza virus replication in MDCK cells, and its triphosphate was a substrate of and demonstrated inhibitory activity against influenza A polymerase. Metabolites of 3c are also presented.