Pathogenesis, Humoral Immune Responses, and Transmission between Cohoused Animals in a Ferret Model of Human Respiratory Syncytial Virus Infection

Abstract

Small animal models have been used to obtain many insights regarding the pathogenesis and immune responses induced following infection with human respiratory syncytial virus (hRSV). Amongst those described to date, infections in cotton rats, mice, guinea pigs, chinchillas and Syrian hamsters with hRSV strains Long and/or A2 have been well characterised, although clinical isolates have also been examined. Ferrets are also susceptible to hRSV infection but the pathogenesis and immune responses elicited following infection have not been well characterised. Herein, we describe the infection of adult ferrets with hRSV Long or A2 via the intranasal route and characterised virus replication, as well as cytokine induction, in the upper and lower airways. Virus replication and cytokine induction during the acute phase of infection (days 0-15 post-infection) were similar between the two strains and both elicited high levels of F glycoprotein-specific binding and neutralising antibodies following virus clearance (days 16-22 post-infection). Importantly, we demonstrate transmission from experimentally infected donor ferrets to co-housed naïve recipients and have characterised virus replication and cytokine induction in the upper airways of infected contact animals. Together, these studies provide a direct comparison of the pathogenesis of hRSV Long and A2 in ferrets and highlight the potential of this animal model to study serological responses and examine interventions that limit transmission of hRSV. Ferrets have been widely used to study pathogenesis, immunity and transmission following human influenza virus infections, however far less is known regarding the utility of the ferret model to study hRSV infections. Following intranasal (IN) infection of adult ferrets with the well characterised Long or A2 strains of hRSV, we report virus replication and cytokine induction in the upper and lower airways, as well as the development of virus-specific humoral responses. Importantly, we demonstrate transmission of hRSV from experimentally infected donor ferrets to co-housed naïve recipients. Together, these findings significantly enhance our understanding of the utility of the ferret as a small animal model to investigate aspects of hRSV pathogenesis and immunity.

Improving immunological insights into the ferret model of human viral infectious disease

“…Nevertheless, ferrets have proven to be a useful model to study RSV. Several groups have successfully infected ferrets with a wild‐type strain of human RSV and demonstrated efficient replication in both the upper and lower respiratory tracts of adult ferrets, consistent with humans where infection is often limited to the upper respiratory tract . Immunocompromised ferrets, induced by oral administration of immunosuppressive drug mycophenolate mofetil (MMF), demonstrate prolonged RSV shedding and effective contact transmission to both immunocompetent and immunocompromised ferrets, confirming antiviral immunity in the ferret can curtail viral replication.…”

“…RSV and HMPV cause severe respiratory disease in young children, the elderly and immunocompromised patients. Both RSV and HMPV readily infect ferrets but in general do not exhibit signs of disease . Nevertheless, ferrets have proven to be a useful model to study RSV.…”

“…Immunocompromised ferrets, induced by oral administration of immunosuppressive drug mycophenolate mofetil (MMF), demonstrate prolonged RSV shedding and effective contact transmission to both immunocompetent and immunocompromised ferrets, confirming antiviral immunity in the ferret can curtail viral replication. An assessment of lung immune gene expression in ferrets infected with RSV demonstrated an upregulation of proinflammatory cytokines such as interleukin‐1 alpha (IL‐1α) and interleukin‐1 beta (IL‐1β) by 5 d.p.i which coincided with maximum levels of RSV mRNA, while levels of other cytokines such as interferon alpha (IFN‐α) and IFN‐ γ remained unchanged . In terms of humoral responses, increased serum titres of fusion (F) glycoprotein antibodies were seen by 15 d.p.i that were protective against re‐infection.…”

“…An assessment of lung immune gene expression in ferrets infected with RSV demonstrated an upregulation of proinflammatory cytokines such as interleukin‐1 alpha (IL‐1α) and interleukin‐1 beta (IL‐1β) by 5 d.p.i which coincided with maximum levels of RSV mRNA, while levels of other cytokines such as interferon alpha (IFN‐α) and IFN‐ γ remained unchanged . In terms of humoral responses, increased serum titres of fusion (F) glycoprotein antibodies were seen by 15 d.p.i that were protective against re‐infection.…”

“…However, for many viruses, alternative animal models better recapitulate human physiology and disease. Ferrets ( Mustela putorius furo ) have been employed to study the pathogenesis of a variety of human pathogens, including human and avian influenzas, coronaviruses including severe acute respiratory syndrome (SARS‐CoV), human respiratory syncytial virus (HRSV), human metapneumovirus (HMPV), Ebola virus and henipavirus (Nipah virus and Hendra virus) . While ferrets can be productively infected with many of these viruses, a lack of some tools to interrogate ferret immunological responses to infection limits insights that might impact the development of vaccines and/or therapeutics.…”