Biology subjects

Racaniello, V. R.

Publications and source records attributed to Racaniello, V. R..

4 recordsLinked to original sources

bioRxiv2018

Role of RIG-I-like receptors in innate immune sensing of Coxsackievirus B3 and encephalomyocarditis virus in murine macrophages and fibroblasts

Viral infections are sensed by pattern recognition receptors that trigger an innate immune response through the expression of interferons (IFNs) and other cytokines. Most RNA viruses are sensed by the RIG-I like receptors (RLR)s. The contributions of these receptors to sensing viruses of the Picornaviridae family were investigated. Encephalomyocarditis virus (EMCV) and Coxsackievirus B3 (CVB3), picornaviruses of the Cardiovirus and Enterovirus genera, are detected by both MDA5 and RIG-I in bone marrow derived macrophages. In macrophages from wild type mice, type I IFN is produced early after infection; IFN{beta} synthesis is reduced in the absence of each sensor, while IFN production is reduced in the absence of MDA5. EMCV and CVB3 do not replicate in murine macrophages, and their detection is different in murine embryonic fibroblasts (MEFs), in which the viruses replicate to high titers. In MEFs RIG-I was essential for the expression of type I IFNs but contributes to increased yields of CVB3, while MDA5 inhibited CVB3 replication but in an IFN independent manner. These observations demonstrate that innate sensing of similar viruses by RLRs depends upon the cell type.\n\nImportanceEnteroviruses such as Coxsackieviruses are the most common human respiratory pathogens. The hosts innate immune response, in particular that modulated by the production of type I and III interferons, is thought to restrict picornavirus infection. Two cytoplasmic proteins, MDA5 and RIG-I, are critical for initiating the early innate immune response against these viruses. Mutations within MDA5 encoding gene have been associated with the development of severe enterovirus associated respiratory illnesses in healthy children. To further understand how the innate immune response dependent upon MDA5 and Rig-I is initiated during picornavirus infection, macrophages from mice lacking MDA5 or RIG-I were infected with Coxsackievirus B3 (CVB3) and a related animal virus. RIG-I is essential for type I IFN production during CVB3 infection; when MDA5 is present, viral titers are reduced by an IFN-independent pathway. These observations demonstrate that innate sensing of viruses by MDA5 and RIG-I depends upon the cell type.

microbiology↗

bioRxiv2017

Replication of early and recent Zika virus isolates throughout mouse brain development

Fetal infection with Zika virus (ZIKV) can lead to congenital Zika virus syndrome (cZVS), which includes cortical malformations and microcephaly. The aspects of cortical development that are affected during virus infection are unknown. Using organotypic brain slice cultures generated from embryonic mice of various ages, sites of ZIKV replication including the neocortical proliferative zone and radial columns, as well as the developing midbrain, were identified. The infected radial units are surrounded by uninfected cells undergoing apoptosis, suggesting that programmed cell death may limit viral dissemination in the brain and may constrain virus associated injury. Therefore, a critical aspect of ZIKV induced neuropathology may be defined by death of uninfected cells. All ZIKV isolates assayed replicated efficiently in early and mid-gestation cultures, and two isolates examined replicated in late-gestation tissue. Alteration of neocortical cytoarchitecture, such as disruption of the highly-elongated basal processes of the radial glial progenitor cells, and impairment of postmitotic neuronal migration were also observed. These data suggest that all lineages of ZIKV tested are neurotropic, and that ZIKV infection interferes with multiple aspects of neurodevelopment that contribute to the complexity of cZVS.\n\nSignificanceZika virus infection has been associated with multiple pathologies of the central nervous system (CNS) including microcephaly, Guillain-Barre syndrome, lissencephaly, the loss of white and grey matter volume and acute myelitis. Using organotypic brain slice cultures, we determined that ZIKV replicates across different embryonic developmental stages, and viral infection can disrupt proper brain development leading to congenital CNS complications. These data illustrate that all lineages of ZIKV tested are neurotropic, and that infection may disrupt neuronal migration during brain development. The results expand our understanding of neuropathologies associated with congenital Zika virus syndrome.

microbiology↗

bioRxiv2017

Polioviruses that bind a chimeric Pvr-nectin-2 protein identify capsid residues involved in receptor interaction

Amino acid changes in the CC\"D region in poliovirus receptor domain 1 disrupt poliovirus binding. To examine further the role of the CC\"D region in poliovirus infection, we substituted this region of Pvr into the corresponding region of a murine homolog, nectin-2. The chimeric receptor, nectin-2Pvr(c'c\"d), rendered transformed L cells susceptible to infection with poliovirus P1/Mahoney, but not with polioviruses P2/Lansing and P3/Leon, due to lack of binding. Twenty-four variants of P2/Lansing were selected that replicate in nectin-2Pvr(c'c\"d) producing cell lines. Sequence analysis revealed 30 amino acid changes at 28 capsid residues. One change, K1103R, is found in nearly all isolates and is located at one end of the VP1 BC loop. Other alterations are located on the canyon surface, at the protomer interface, and along the perimeter of the canyon south wall. Unlike poliovirus-Pvr binding, the VP1 BC loop is required for infection of cells producing nectin-2Pvr(c'c\"d).

microbiology↗

bioRxiv2017

Neurotropism of enterovirus D68 isolates is independent of sialic acid and is not a recently acquired phenotype

Acute flaccid myelitis /acute flaccid paralysis (AFM/AFP) is a rare but serious illness of the nervous system, specifically affecting the grey matter of the spinal cord, motor controlling regions of the brain and the cranial nerve. Most cases of AFM/AFP are pathogen associated, typically with poliovirus and enterovirus infections, and occur in children under the age of 6 years old. Enterovirus D68 (EV-D68) was first isolated from children with pneumonia in 1962, but an association with AFM/AFP was not observed until the 2014 outbreak. Organotypic mouse brain slice cultures generated from postnatal day 1 to 10 mice were used to determine if neurotropism of EV-D68 is shared among virus isolates. Six of the seven EV-D68 isolates examined, including two from 1962 and four from the 2014 outbreak, replicated in neurons, and all replicated in astrocytes. Furthermore, a putative viral receptor, sialic acid, is not required for neurotropism of EV-D68, as both sialic acid dependent and independent viruses replicated within neurons. These observations demonstrate that EV-D68 is neurotropic independent of its genetic lineage, can infect both neurons and astrocytes, and that neurotropism is not a recently acquired characteristic as has been suggested.\n\nSignificanceRecently there has been an increase in the number of children infected with enterovirus D68 (EV-D68). Most infections are associated with mild flu-like symptoms, but neurological dysfunction may develop in a small number of children. How the biochemical and genetic differences among EV-D68 isolates relates to development of neurological disease remains an unanswered question. Assessing infection of multiple viral isolates in organotypic brain slice cultures from postnatal day 1 to 10 mice revealed that multiple isolates are neurotropic. Both neuraminidase sensitive and resistant viruses infected neurons, indicating that sialic acid binding does not play a role in EV-D68 neuropathogenesis. Establishment of a genetically and pharmacologically amenable system using organotypic brain slice cultures will provide insight into how EV-D68 neuropathologies develop.

microbiology↗