Journal of General Virology (2008), 89, 2709–2712 DOI 10.1099/vir.0.2008/003301-0 Effect of NMSO3 treatment in a murine model of human metapneumovirus infection Leanne Spetch,1 Terry L. Bowlin2 and Antonella Casola1,3,4 1Department of Pediatrics, University of Texas Medical Branch, Galveston, TX, USA 2Microbiotix Inc., Worcester, MA, USA 3Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, USA 4Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, TX, USA BALB/c mice infected with human metapneumovirus (hMPV) were treated with the sulfated sialyl lipid NMSO3 (one dose of 50 mg kg”1) given at the time of infection. NMSO3 significantly reduced viral replication in the lungs, as well as hMPV-induced body weight loss, pulmonary inflammation and cytokine production, suggesting that antiviral treatment initiated at the beginning of viral infection can modify hMPV-induced disease. Short Communication Correspondence Antonella Casola ancasola@utmb.edu Received 18 April 2008 Accepted 1 July 2008 Human metapneumovirus (hMPV) is a recently identified human respiratory viral pathogen belonging to the family Paramyxoviridae (van den Hoogen et al., 2001). hMPV is associated with upper and lower respiratory tract infections in children and adults, as reported in studies worldwide. According to various reports, between 5 and 12 % of all respiratory tract infections in younger infants are caused by hMPV, second only to respiratory syncytial virus (RSV), and it may account for 10 % of all hospitalizations of elderly patients with respiratory tract infections (reviewed by Hamelin & Boivin, 2005). No specific antivirals or other therapeutic agents are licensed to treat hMPV infection. Similarly, no vaccine is currently available. We and others have recently identified BALB/c mice as an effective murine model to investigate hMPV-induced airway disease (Alvarez et al., 2004; Guerrero-Plata et al., 2005; Hamelin et al., 2005). Ribavirin, a nucleoside analogue of guanosine used in the treatment of RSV infection, has recently been shown to affect hMPV replication in vitro and in vivo (Hamelin et al., 2006; Wyde et al., 2003). Similarly, NMSO3, a sulfated sialyl lipid with potent antiviral activity against RSV, has recently been shown to inhibit hMPV replication in vitro (Wyde et al., 2004). In this study, we assessed the effect of NMSO3 treatment on hMPV replication and pulmonary inflammation in vivo, using a BALB/c model of infection. Female BALB/c mice (Harlan Sprague Dawley), 6–7 weeks old, were housed under pathogen-free conditions. A total of four experimental groups consisting of two treatment groups (carrier and NMSO3) for each infection group (mock- and hMPV-infected) was used for all experiments. For each experiment, four to five mice were used per group. Experiments were repeated two to three times. There was no effect of the vehicle by itself; therefore, the 2008/003301 G 2008 SGM Printed in Great Britain groups of mock-infected+carrier and hMPV-infected+ carrier are identified in the text and figures as mock- and hMPV-infected. Under light anaesthesia, mice were inoculated intranasally (i.n.) with 16107 TCID50 hMPV in a total volume of 50 ml. This volume of inoculum has been shown to deliver the virus directly to the lungs. At 30– 60 min after viral inoculation, mice were administered NMSO3 i.n. at a concentration of 10, 50 or 100 mg kg21 in a total volume of 50 ml. NMSO3 was prepared in water at a stock concentration of 100 mg ml21 and then diluted in PBS to the final desired concentration immediately before administration. Mice were weighed daily from day 0 to 10 post-infection (p.i.). At days 1 and 4 p.i., mice were sacrificed to determine lung viral titres and cellular inflammation, and to measure cytokine and chemokine production, as described previously (Guerrero-Plata et al., 2005, 2006; Haeberle et al., 2001). To determine the effects of NMSO3 on hMPV infection, we initially examined whether NMSO3 altered hMPV replication in vivo. We tested three different concentrations of NMSO3, given on the first day of hMPV infection, based on a previous study that used NMSO3 in a rat model of RSV infection, showing amelioration of RSV-induced clinical illness (Kimura et al., 2000). In our mouse model of hMPV infection, increased viral titres could be detected as early as day 3 p.i., with peak viral titres occurring at day 5 p.i. and viral clearance by day 7 p.i. (data not shown). NMSO3 administration of 10 mg kg21 only marginally reduced hMPV replication from 4.5±0.1 to 4.1±0.05 log10, whilst treatment with 50 mg kg21 significantly decreased peak viral load by about 1 log, from 5.12±0.31 to 4.1±0.32 log10. Administration of 100 mg kg21 resulted in a further reduction in viral replication (5.2±0.1 to 3.9±0.2 log10), but was also 2709