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In 2014, enterovirus D68 (EV-D68) emerged causing outbreaks of severe respiratory disease in children worldwide. In a subset of patients, EV-D68 infection was associated with the development of central nervous system (CNS) complications, including acute flaccid myelitis (AFM). Since then, the number of reported outbreaks has risen biennially, which emphasizes the need to unravel the systemic pathogenesis in humans. We present here a comprehensive review on the different stages of the pathogenesis of EV-D68 infection – infection in the respiratory tract, systemic dissemination and infection of the CNS – based on observations in humans as well as experimental in vitro and in vivo studies. This review highlights the knowledge gaps on the mechanisms of systemic dissemination, routes of entry into the CNS and mechanisms to induce AFM or other CNS complications, as well as the role of virus and host factors in the pathogenesis of EV-D68. [ABSTRACT FROM AUTHOR]

• Intrathecal virus-specific antibody detection can help to diagnose viral CNS diseases • Intrathecal antibodies can be detected in EV-associated CNS disease, including EV-D68 • To improve diagnostics for EV-D68 a specific ELISA should be developed. Enterovirus-D68 (EV-D68) predominantly causes respiratory disease. However, EV-D68 infections also have been associated with central nervous system (CNS) complications, most specifically acute flaccid myelitis (AFM). Diagnosing EV-D68-associated CNS disease is challenging since viral RNA is rarely detected in cerebrospinal fluid (CSF). In order to determine an EV antibody index (AI), we evaluated the value of a commercially available quantitative ELISA to detect EV-specific antibodies in paired CSF and blood. Nine paired CSF and blood samples were obtained from patients with EV-D68-associated AFM or from patients with a confirmed EV-associated CNS disease. EV-specific antibodies were detected using a quantitative ELISA. A Reiber diagram analysis was performed, by which the AI was calculated. Subsequently, EV ELISA results were compared with an EV-D68 virus neutralization test. ELISA detected EV-specific antibodies in 1 out of the 3 patients with EV-D68-associated AFM and in 3 out of the 6 patients with confirmed EV-associated CNS disease. In these patients, the AI was indicative for intrathecal antibody production against enterovirus. Assay comparison showed that EV-D68 neutralizing antibody detection increased the sensitivity of EV-D68 antibody detection. A quantitative EV IgG ELISA in combination with Reiber diagram analysis and AI-calculation can be used as a diagnostic tool for EV-associated CNS disease, including EV-D68. An EV-D68 specific ELISA will improve the sensitivity of the tool. With the growing awareness that the detection of non-polio enteroviruses needs to be improved, diagnostic laboratories should consider implementation of EV serology. [ABSTRACT FROM AUTHOR]

Middle East respiratory syndrome coronavirus (MERS-CoV) is a zoonotic pathogen that causes respiratory infection in humans, ranging from asymptomatic to severe pneumonia. In dromedary camels, the virus only causes a mild infection but it spreads efficiently between animals. Differences in the behavior of the virus observed between individuals, as well as between humans and dromedary camels, highlight the role of host factors in MERS-CoV pathogenesis and transmission. One of these host factors, the MERS-CoV receptor dipeptidyl peptidase-4 (DPP4), may be a critical determinant because it is variably expressed in MERS-CoV-susceptible species as well as in humans. This could partially explain inter- and intraspecies differences in the tropism, pathogenesis, and transmissibility of MERS-CoV. In this review, we explore the role of DPP4 and other host factors in MERS-CoV transmission and pathogenesis—such as sialic acids, host proteases, and interferons. Further characterization of these host determinants may potentially offer novel insights to develop intervention strategies to tackle ongoing outbreaks. [ABSTRACT FROM AUTHOR]