Unraveling the Mysteries of Acute Flaccid Myelitis: Scientific Opportunities and Priorities for Future Research

Cellular glycan modification by B3GAT1 broadly restricts influenza virus infection

Communicable respiratory viral infections pose both epidemic and pandemic threats and broad-spectrum antiviral strategies could improve preparedness for these events. To discover host antiviral restriction factors that may act as suitable targets for the development of host-directed antiviral therapies, we here conduct a whole-genome CRISPR activation screen with influenza B virus (IBV). A top hit from our screen, beta-1,3-glucuronyltransferase 1 (B3GAT1), effectively blocks IBV infection. Subsequent studies reveal that B3GAT1 activity prevents cell surface sialic acid expression. Due to this mechanism of action, B3GAT1 expression broadly restricts infection with viruses that require sialic acid for entry, including Victoria and Yamagata lineage IBVs, H1N1/H3N2 influenza A viruses (IAVs), and the unrelated enterovirus D68. To understand the potential utility of B3GAT1 induction as an antiviral strategy in vivo, we specifically express B3GAT1 in the murine respiratory epithelium and find that overexpression is not only well-tolerated, but also protects female mice from a lethal viral challenge with multiple influenza viruses, including a pandemic-like H1N1 IAV. Thus, B3GAT1 may represent a host-directed broad-spectrum antiviral target with utility against clinically relevant respiratory viruses.

Neutralizing Antibody Given after Paralysis Onset Reduces the Severity of Paralysis Compared to Nonspecific Antibody-Treated Controls in a Mouse Model of EV-D68-Associated Acute Flaccid Myelitis

Enterovirus D68 (EV-D68) can cause mild to severe respiratory illness and is associated with a poliomyelitis-like paralytic syndrome called acute flaccid myelitis (AFM). Most cases of EV-D68-associated AFM occur in young children who are brought to the clinic after the onset of neurologic symptoms. There are currently no known antiviral therapies for AFM, and it is unknown whether antiviral treatments will be effective if initiated after the onset of neurologic symptoms (when patients are likely to present for medical care). We developed a "clinical treatment model" for AFM, in which individual EV-D68-infected mice are tracked and treated with an EV-D68-specific human-mouse chimeric monoclonal antibody after the onset of moderate paralysis. Mice treated with antibody had significantly better paralysis outcomes compared to nonspecific antibody-treated controls. Treatment did not reverse paralysis that was present at the time of treatment initiation but did slow the further loss of function, including progression of weakness to other limbs, as well as reducing viral titer in the muscle and spinal cords of treated animals. We observed the greatest therapeutic effect in EV-D68 isolates which were neutralized by low concentrations of antibody, and diminishing therapeutic effect in EV-D68 isolates which required higher doses of antibody for neutralization. This work supports the use of virus-specific immunotherapy for the treatment of AFM. It also suggests that patients who present with AFM should be treated as soon as possible if recent infection with EV-D68 is suspected.

Neurologic complications of coronavirus and other respiratory viral infections

In humans, several respiratory viruses can have neurologic implications affecting both central and peripheral nervous system. Neurologic manifestations can be linked to viral neurotropism and/or indirect effects of the infection due to endothelitis with vascular damage and ischemia, hypercoagulation state with thrombosis and hemorrhages, systemic inflammatory response, autoimmune reactions, and other damages. Among these respiratory viruses, recent and huge attention has been given to the coronaviruses, especially the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic started in 2020. Besides the common respiratory symptoms and the lung tropism of SARS-CoV-2 (COVID-19), neurologic manifestations are not rare and often present in the severe forms of the infection. The most common acute and subacute symptoms and signs include headache, fatigue, myalgia, anosmia, ageusia, sleep disturbances, whereas clinical syndromes include mainly encephalopathy, ischemic stroke, seizures, and autoimmune peripheral neuropathies. Although the pathogenetic mechanisms of COVID-19 in the various acute neurologic manifestations are partially understood, little is known about long-term consequences of the infection. These consequences concern both the so-called long-COVID (characterized by the persistence of neurological manifestations after the resolution of the acute viral phase), and the onset of new neurological symptoms that may be linked to the previous infection.