A medium-throughput screen for inhibitors of human metapneumovirus

Viral Cytopathic Changes in Sputum Cytology in a Patient with Known Human Metapneumovirus

INTRODUCTION

Viral cytopathic changes seen in sputum cytology have been described in association with infection by viruses such as cytomegalovirus (CMV), herpes simplex virus (HSV), adenovirus, and even measles. However, viral cytopathic changes due to human metapneumovirus (hMPV) have not yet been well described in cytology. hMPV is a relatively new entity, discovered in 2001. It is known to cause upper and lower respiratory tract infections in children, the elderly, and immunocompromised patients.

CASE PRESENTATION

We describe the viral cytopathic changes seen in sputum in a 63-year-old male patient with known hMPV. These changes include multinucleation, nuclear enlargement, homogenised nuclei, basophilic nuclear inclusions with perinuclear halos, and small eosinophilic cytoplasmic inclusions.

CONCLUSION

We aim to raise awareness that hMPV can cause viral cytopathic changes and to describe these cytological features, which have been elucidated in only 1 case report thus far. Distinction from other viruses with similar changes, such as HSV and CMV, is important due to their differing clinical implications.

Drug Repurposing for Therapeutic Discovery against Human Metapneumovirus Infection

Human metapneumovirus (HMPV) is recognized as an important cause of pneumonia in infants, in the elderly, and in immunocompromised individuals worldwide. The absence of an antiviral treatment or vaccine strategy against HMPV infection creates a high burden on the global health care system. Drug repurposing has become increasingly attractive for the treatment of emerging and endemic diseases as it requires less research and development costs than traditional drug discovery. In this study, we developed an in vitro medium-throughput screening assay that allows for the identification of novel anti-HMPV drugs candidates. Out of ~2,400 compounds, we identified 11 candidates with a dose-dependent inhibitory activity against HMPV infection. Additionally, we further described the mode of action of five anti-HMPV candidates with low in vitro cytotoxicity. Two entry inhibitors, Evans Blue and aurintricarboxylic acid, and three post-entry inhibitors, mycophenolic acid, mycophenolate mofetil, and 2,3,4-trihydroxybenzaldehyde, were identified. Among them, the mycophenolic acid series displayed the highest levels of inhibition, due to the blockade of intracellular guanosine synthesis. Importantly, MPA has significant potential for drug repurposing as inhibitory levels are achieved below the approved human oral dose. Our drug-repurposing strategy proved to be useful for the rapid discovery of novel hit candidates to treat HMPV infection and provide promising novel templates for drug design.

Antiviral strategies against human metapneumovirus: Targeting the fusion protein

Human metapneumoviruses have emerged in the past decades as an important global pathogen that causes severe upper and lower respiratory tract infections. Children under the age of 2, the elderly and immunocompromised individuals are more susceptible to HMPV infection than the general population due to their suboptimal immune system. Despite the recent discovery of HMPV as a novel important respiratory virus, reports have rapidly described its epidemiology, biology, and pathogenesis. However, progress is still to be made in the development of vaccines and drugs against HMPV infection as none are currently available. Herein, we discuss the importance of HMPV and review the reported strategies for anti-HMPV drug candidates. We also present the fusion protein as a promising antiviral drug target due to its multiple roles in the HMPV lifecycle. This key viral protein has previously been targeted by a range of inhibitors, which will be discussed as they represent opportunities for future drug design.

Human Metapneumovirus: A Largely Unrecognized Threat to Human Health

Human metapneumovirus (HMPV) infects most children by five years of age. The virus can cause both upper and lower respiratory tract disease and can be life threatening. High-risk populations include young children who are exposed to virus for the first time and the elderly. Currently, there is no standard treatment nor licensed vaccine for HMPV, although several attractive vaccine candidates have been developed for pre-clinical studies. A raised awareness of the impact of HMPV on public health is needed to drive research, complete vaccine development, and thereby prevent significant virus-associated morbidities and mortalities worldwide.