Effect of Ribavirin and Glucocorticoid Treatment in a Mouse Model of Human Metapneumovirus Infection

Abstract

Human metapneumovirus (hMPV)-infected BALB/c mice were treated with ribavirin (40 mg/kg of body weight twice a day intraperitoneally), corticosterone (0.2 mg/ml in water), or both modalities. Ribavirin significantly decreased both hMPV replication in lungs (by 5 log 10 ) and global pulmonary inflammation on day 5 postinfection, whereas glucocorticoids reduced only alveolar and interstitial inflammation, compared to controls.Human metapneumovirus (hMPV) is a newly described member of the Paramyxoviridae family associated with acute respiratory tract infections in all age groups, with more-severe diseases occurring in young children, elderly individuals, and immunocompromised hosts (3,7,8,15). Experimental animal models of hMPV infection have been reported for primates and rodents (9,12,17,19). Notably, the BALB/c mouse has been described as a good and convenient animal model for this virus due to efficient viral replication and significant lung inflammation associated with systemic and respiratory symptoms when a high intranasal inoculum is used (1, 9). Although ribavirin has been reported to decrease hMPV titers in vitro (18), this drug has not been evaluated with animal models. In this study, we assessed the effects of ribavirin with or without glucocorticoids on hMPV replication and pulmonary inflammation by using a previously described BALB/c mouse model (9).Animal studies. Forty-eight 4-to 6-week-old BALB/c mice (Charles Rivers Laboratories, Wilmington, MA) were randomized into six groups of eight mice each, based on weight. On day 0, four groups (32 mice) were infected intranasally with 1 ϫ 10 8 50% tissue culture infective doses (TCID 50 ) of hMPV strain C-85473 (type A) at passage 7 in 25 l of hMPV infection medium as previously reported (9). The other two groups (16 mice) were sham infected with infection medium, and all animals were housed in groups of four in microisolator cages. Groups of hMPV-infected mice were treated with phosphatebuffered saline (PBS), ribavirin (MP Biomedicals, Aurora, OH) at 40 mg/kg of body weight every 12 h, corticosterone (Sigma, St. Louis, MO) at 0.2 mg/ml, or ribavirin and corticosterone. Groups of sham-infected mice were treated with either PBS or ribavirin as described above. Ribavirin and PBS were given intraperitoneally from day 0 to day 5 postinfection, beginning 12 h postinfection, whereas corticosterone was given in water ad libitum from day 3 to day 5. Mice were weighted every day and then sacrificed on day 5 postinfection. The right lungs were homogenized in infection medium and used to determine viral titers in LLC-MK2 cells, whereas the left lungs were used for determination of histopathological scores based on a scale previously described (9,14).

Animal models for human Metapneumovirus (HMPV) infections

“…The results of both studies were promising as it appeared that peptide vaccination is sufficient to protect mice from infection with HMPV [9] and that it is worth to consider ribavirin -which is also active against HMPV -as an antiviral drug for treatment of severe HMPV infections [8]. Thereby the latter study [8] also investigated on the use of glucocorticoid treatment as a supplement to the ribavirin therapy.…”

“…Furthermore, two recent reports made use of the BALB/c mouse model for peptide vaccination studies [9] and for the study of antiviral treatment with ribavirin [8]. The results of both studies were promising as it appeared that peptide vaccination is sufficient to protect mice from infection with HMPV [9] and that it is worth to consider ribavirin -which is also active against HMPV -as an antiviral drug for treatment of severe HMPV infections [8].…”

“…The reasons for this discussion were two earlier reports from Macphail et al [12] and Williams et al [23] that demonstrated that mice are not permissive for HMPV, although the usefulness of the model was supported by the data of Hamelin et al [6][7][8] as well as the recent observations from Darniot et al [4] who investigated immunological response against the HMPV infection in infected BALB/c mice [4,[6][7][8] and cotton rats [6], respectively. It is noteworthy that Darniot et al [4] observed HMPV replication of 10 3 pfu/g in the lungs of BALB/c mice, similar to levels detected by Williams et al [23] and thus substantially lower than the levels of lung replication detected in BALB/c mice by Alvarez et al [1,2] and Hamelin et al [6][7][8]. A number of factors may account for these divergent findings.…”

“…a subtype specific illness severity, appears the most logical explanation. The resulting hypothesis that the clinical severity of the infection depends both on (hitherto unknown) viral factors and host factors is supported by the fact that Macphail et al [12] also found cotton rats to be poorly permissive for HMPV replication, in contrast to the findings of Wyde et al [27], Williams et al [23], and Hamelin et al [6][7][8]. Thereby, MacPhail et al [12], Williams et al [23], and Hamelin et al [6][7][8] used virus from strain A but different isolates as inoculum for cotton rats, whereas Alvarez et al [1,2] used an isolate from the HMPV lineage B that is supposed to be less pathogenic in children but replicates to high titers in mice.These discrepancies may thus indeed result from yet unknown differences in virus or rodent strains used, methods of inoculation and detection or the groups' varying experience with different animal models.…”

Immune modulatory activity of ribavirin for serious human metapneumovirus disease: early i.v. therapy may improve outcomes in immunosuppressed SCT recipients

“…It shows good in vivo activity against experimental hMPV infection. 7 Ribavirin through upregulation of CD4 and CD8 T-lymphocyte-derived IL-2, tumor necrosis factor-a, interferon-g and downregulation of T-helper 2 cytokines such as IL-10 enhances containment of viral infection. 8 This drug-induced restoration of T-cell hyporesponsiveness that follows prolonged viral replication is critical in resolution of infection.…”