Common Dysregulation of Innate Immunity Pathways in Human Primary Astrocytes Infected With Chikungunya, Mayaro, Oropouche, and Zika Viruses

Oropouche virus - another antecedent event for Guillain-Barré syndrome?

In May 2024, the Pan American Health Organization issued alerts of increased numbers of cases of Oropouche fever in non-Amazonian regions in Latin America. Following this, an association between Oropouche fever and Guillain-Barré syndrome was reported in three patients in Santiago de Cuba, Cuba. Neurological manifestations have rarely been described in relation to Oropouche virus infection. Previously, encephalitis and meningoencephalitis have been associated with Oropouche virus infection, but now the virus seems also to be associated with Guillain-Barré syndrome. In this article we describe the main factors that could underlie the increased incidence of Oropouche fever and its neurological complications. Oropouche virus should be recognized as a potential pathogen in cases of fever associated with neurological symptoms (meningitis, meningoencephalitis, and Guillain-Barré syndrome). Medical professionals and health systems need to be aware of these complications and the importance of early diagnosis and preparedness, especially during large outbreaks or in patients living in or coming from endemic regions.

Human brain tissue cultures: a unique ex vivo model to unravel the pathogenesis of neurotropic arboviruses

Arboviruses are transmitted by arthropods, and their spread from endemic to nonendemic regions has been accelerated by deforestation, climate change, and global mobility. Arbovirus infection in human results in symptoms ranging from mild to life-threatening, with the impairment of central nervous system functions being reported in severe cases. Despite its clinical relevance, the mechanisms by which arboviruses led to neural dysfunction are still poorly understood. The lack of a widespread human central nervous system model to study the virus-host interaction challenges the advance of our knowledge on these mechanisms. In this context, human brain-derived ex vivo models have the advantage of preserving cellular diversity, cell connections, and tissue cytoarchitecture found in human brain, raising them as a powerful strategy to elucidate the cellular-molecular alterations underlying brain diseases. Here, we review recent advances in the field of neurotropic arboviruses obtained using ex vivo human brain tissue as the experimental model.

Heterogeneous Ribonucleoprotein K Is a Host Regulatory Factor of Chikungunya Virus Replication in Astrocytes

Chikungunya virus (CHIKV) is an emerging, mosquito-borne arthritic alphavirus increasingly associated with severe neurological sequelae and long-term morbidity. However, there is limited understanding of the crucial host components involved in CHIKV replicase assembly complex formation, and thus virus replication and virulence-determining factors, within the central nervous system (CNS). Furthermore, the majority of CHIKV CNS studies focus on neuronal infection, even though astrocytes represent the main cerebral target. Heterogeneous ribonucleoprotein K (hnRNP K), an RNA-binding protein involved in RNA splicing, trafficking, and translation, is a regulatory component of alphavirus replicase assembly complexes, but has yet to be thoroughly studied in the context of CHIKV infection. We identified the hnRNP K CHIKV viral RNA (vRNA) binding site via sequence alignment and performed site-directed mutagenesis to generate a mutant, ΔhnRNPK-BS1, with disrupted hnRNPK-vRNA binding, as verified through RNA coimmunoprecipitation and RT-qPCR. CHIKV ΔhnRNPK-BS1 demonstrated hampered replication in both NSC-34 neuronal and C8-D1A astrocytic cultures. In astrocytes, disruption of the hnRNPK-vRNA interaction curtailed viral RNA transcription and shut down subgenomic RNA translation. Our study demonstrates that hnRNP K serves as a crucial RNA-binding host factor that regulates CHIKV replication through the modulation of subgenomic RNA translation.

The Relationship between HERV, Interleukin, and Transcription Factor Expression in ZIKV Infected versus Uninfected Trophoblastic Cells

Zika virus (ZIKV) is an arbovirus with maternal, sexual, and TORCH-related transmission capabilities. After 2015, Brazil had the highest number of ZIVK-infected pregnant women who lost their babies or delivered them with Congenital ZIKV Syndrome (CZS). ZIKV triggers an immune defense in the placenta. This immune response counts with the participation of interleukins and transcription factors. Additionally, it has the potential involvement of human endogenous retroviruses (HERVS). Interleukins are immune response regulators that aid immune tolerance and support syncytial structure development in the placenta, where syncytin receptors facilitate vital cell-to-cell fusion events. HERVs are remnants of ancient viral infections that integrate into the genome and produce syncytin proteins crucial for placental development. Since ZIKV can infect trophoblast cells, we analyzed the relationship between ZIKV infection, HERV, interleukin, and transcription factor modulations in the placenta. To investigate the impact of ZIKV on trophoblast cells, we examined two cell types (BeWo and HTR8) infected with ZIKV-MR766 (African) and ZIKV-IEC-Paraíba (Asian-Brazilian) using Taqman and RT2 Profiler PCR Array assays. Our results indicate that early ZIKV infection (24-72 h) does not induce differential interleukins, transcription factors, and HERV expression. However, we show that the expression of a few of these host defense genes appears to be linked independently of ZIKV infection. Future studies involving additional trophoblastic cell lineages and extended infection timelines will illuminate the dynamic interplay between ZIKV, HERVs, interleukins, and transcription factors in the placenta.

Emergence of Oropouche fever in Latin America: a narrative review

Since its discovery in 1955, the incidence and geographical spread of reported Oropouche virus (OROV) infections have increased. Oropouche fever has been suggested to be one of the most important vector-borne diseases in Latin America. However, both literature on OROV and genomic sequence availability are scarce, with few contributing laboratories worldwide. Three reassortant OROV glycoprotein gene variants termed Iquitos, Madre de Dios, and Perdões virus have been described from humans and non-human primates. OROV predominantly causes acute febrile illness, but severe neurological disease such as meningoencephalitis can occur. Due to unspecific symptoms, laboratory diagnostics are crucial. Several laboratory tests have been developed but robust commercial tests are hardly available. Although OROV is mainly transmitted by biting midges, it has also been detected in several mosquito species and a wide range of vertebrate hosts, which likely facilitates its widespread emergence. However, potential non-human vertebrate reservoirs have not been systematically studied. Robust animal models to investigate pathogenesis and immune responses are not available. Epidemiology, pathogenesis, transmission cycle, cross-protection from infections with OROV reassortants, and the natural history of infection remain unclear. This Review identifies Oropouche fever as a neglected disease and offers recommendations to address existing knowledge gaps, enable risk assessments, and ensure effective public health responses.

Modulation of HERV Expression by Four Different Encephalitic Arboviruses during Infection of Human Primary Astrocytes

Human retroelements (HERVs) are retroviral origin sequences fixed in the human genome. HERVs induction is associated with neurogenesis, cellular development, immune activation, and neurological disorders. Arboviruses are often associated with the development of encephalitis. The interplay between these viruses and HERVs has not been fully elucidated. In this work, we analyzed RNAseq data derived from infected human primary astrocytes by Zika (ZikV), Mayaro (MayV), Oropouche (OroV) and Chikungunya (ChikV) viruses, and evaluated the modulation of HERVs and their nearby genes. Our data show common HERVs expression modulation by both alphaviruses, suggesting conserved evolutionary routes of transcription regulation. A total of 15 HERVs were co-modulated by the four arboviruses, including the highly upregulated HERV4_4q22. Data on the upregulation of genes nearby to these elements in ChikV, MayV and OroV infections were also obtained, and interaction networks were built. The upregulation of 14 genes common among all viruses was observed in the networks, and 93 genes between MayV and ChikV. These genes are related to cellular processes such as cellular replication, cytoskeleton, cell vesicle traffic and antiviral response. Together, our results support the role of HERVs induction in the transcription regulation process of genes during arboviral infections.

A Review of Omics Studies on Arboviruses: Alphavirus, Orthobunyavirus and Phlebovirus

Since the intricate and complex steps in pathogenesis and host-viral interactions of arthropod-borne viruses or arboviruses are not completely understood, the multi-omics approaches, which encompass proteomics, transcriptomics, genomics and metabolomics network analysis, are of great importance. We have reviewed the omics studies on mosquito-borne viruses of the Togaviridae, Peribuyaviridae and Phenuiviridae families, specifically for Chikungunya, Mayaro, Oropouche and Rift Valley Fever viruses. Omics studies can potentially provide a new perspective on the pathophysiology of arboviruses, contributing to a better comprehension of these diseases and their effects and, hence, provide novel insights for the development of new antiviral drugs or therapies.