Abnormalities of ILC1 in children with hand, foot and mouth disease during enterovirus 71 infection

Current status of hand-foot-and-mouth disease

Hand-foot-and-mouth disease (HFMD) is a viral illness commonly seen in young children under 5 years of age, characterized by typical manifestations such as oral herpes and rashes on the hands and feet. These symptoms typically resolve spontaneously within a few days without complications. Over the past two decades, our understanding of HFMD has greatly improved and it has received significant attention. A variety of research studies, including epidemiological, animal, and in vitro studies, suggest that the disease may be associated with potentially fatal neurological complications. These findings reveal clinical, epidemiological, pathological, and etiological characteristics that are quite different from initial understandings of the illness. It is important to note that HFMD has been linked to severe cardiopulmonary complications, as well as severe neurological sequelae that can be observed during follow-up. At present, there is no specific pharmaceutical intervention for HFMD. An inactivated Enterovirus A71 (EV-A71) vaccine that has been approved by the China Food and Drug Administration (CFDA) has been shown to provide a high level of protection against EV-A71-related HFMD. However, the simultaneous circulation of multiple pathogens and the evolution of the molecular epidemiology of infectious agents make interventions based solely on a single agent comparatively inadequate. Enteroviruses are highly contagious and have a predilection for the nervous system, particularly in child populations, which contributes to the ongoing outbreak. Given the substantial impact of HFMD around the world, this Review synthesizes the current knowledge of the virology, epidemiology, pathogenesis, therapy, sequelae, and vaccine development of HFMD to improve clinical practices and public health efforts.

Antiviral Activities of Group I Innate Lymphoid Cells

Even before the adaptive immune response initiates, a potent group of innate antiviral cells responds to a wide range of viruses to limit replication and virus-induced pathology. Belonging to a broader family of recently discovered innate lymphoid cells (ILCs), antiviral group I ILCs are composed of conventional natural killer cells (cNK) and tissue-resident ILCs (ILC1s) that can be distinguished based on their location as well as by the expression of key cell surface markers and transcription factors. Functionally, blood-borne cNK cells recirculate throughout the body and are recruited into the tissue at sites of viral infection where they can recognize and lyse virus-infected cells. In contrast, ILC1s are poised in uninfected barrier tissues and respond not through lysis but with the production of antiviral cytokines. From their frontline tissue locations, ILC1s can even induce an antiviral state in uninfected tissue to preempt viral replication. Mounting evidence also suggests that ILC1s may have enhanced secondary responses to viral infection. In this review, we discuss recent findings demonstrating that ILC1s provide several critical layers of innate antiviral immunity and the mechanisms (when known) underlying protection.