Antibody-Mediated Virus Neutralization Is Not a Universal Mechanism of Marburg, Ebola, or Sosuga Virus Clearance in Egyptian Rousette Bats.

Although bats are increasingly being recognized as natural reservoir hosts of emerging zoonotic viruses, little is known about how they control and clear virus infection in the absence of clinical disease. Here, we test >50 convalescent sera from Egyptian rousette bats (ERBs) experimentally primed or prime-boosted with Marburg virus, Ebola virus, or Sosuga virus for the presence of virus-specific neutralizing antibodies, using infectious reporter viruses. After serum neutralization testing, we conclude that antibody-mediated virus neutralization does not contribute significantly to the control and clearance of Marburg virus, Ebola virus, or Sosuga virus infection in ERBs.

Identification and characterization of novel mosquito-borne (Kammavanpettai virus) and tick-borne (Wad Medani) reoviruses isolated in India.

In 1954, a virus named Wad Medani virus (WMV) was isolated from Hyalomma marginatum ticks from Maharashtra State, India. In 1963, another virus was isolated from Sturnia pagodarum birds in Tamil Nadu, India, and named Kammavanpettai virus (KVPTV) based on the site of its isolation. Originally these virus isolates could not be identified with conventional methods. Here we describe next-generation sequencing studies leading to the determination of their complete genome sequences, and identification of both virus isolates as orbiviruses (family Reoviridae). Sequencing data showed that KVPTV has an AT-rich genome, whereas the genome of WMV is GC-rich. The size of the KVPTV genome is 18 234 nucleotides encoding proteins ranging 238-1290 amino acids (aa) in length. Similarly, the size of the WMV genome is 16 941 nucleotides encoding proteins ranging 214-1305 amino acids in length. Phylogenetic analysis of the VP1 gene, along with the capsid genes VP5 and VP7, revealed that KVPTV is likely a novel mosquito-borne virus and WMV is a tick-borne orbivirus. This study focuses on the phylogenetic comparison of these newly identified orbiviruses with mosquito-, tick- and Culicoides-borne orbiviruses isolated in India and other countries.

Ebola Virus Diagnostics: The US Centers for Disease Control and Prevention Laboratory in Sierra Leone, August 2014 to March 2015.

In August 2014, the Viral Special Pathogens Branch of the US Centers for Disease Control and Prevention established a field laboratory in Sierra Leone in response to the ongoing Ebola virus outbreak. Through March 2015, this laboratory tested >12 000 specimens from throughout Sierra Leone. We describe the organization and procedures of the laboratory located in Bo, Sierra Leone.

Isolation and phylogenomic analysis of buffalopox virus from human and buffaloes in India.

Three genome sequences of Buffalopox virus (BPVX) were retrieved from a human and two buffaloes scab samples. Phylogenomic analysis of the BPXV indicates that it shares a most recent common ancestor with Lister and closely related vaccine strains when compared to potential wild-type VACV strains (like Horsepox virus).

Rousette Bat Dendritic Cells Overcome Marburg Virus-Mediated Antiviral Responses by Upregulation of Interferon-Related Genes While Downregulating Proinflammatory Disease Mediators.

Dysregulated and maladaptive immune responses are at the forefront of human diseases caused by infection with zoonotic viral hemorrhagic fever viruses. Elucidating mechanisms of how the natural animal reservoirs of these viruses coexist with these agents without overt disease, while permitting sufficient replication to allow for transmission and maintenance in a population, is important for understanding the viral ecology and spillover to humans. The Egyptian rousette bat (ERB) has been identified as a reservoir for Marburg virus (MARV), a filovirus and the etiological agent of the highly lethal Marburg virus disease. Little is known regarding how these bats immunologically respond to MARV infection. In humans, macrophages and dendritic cells (DCs) are primary targets of infection, and their dysregulation is thought to play a central role in filovirus diseases, by disturbing their normal functions as innate sensors and adaptive immune response facilitators while serving as amplification and dissemination agents for the virus. The infection status and responses to MARV in bat myeloid-lineage cells are uncharacterized and likely represent an important modulator of the bat's immune response to MARV infection. Here, we generate DCs from the bone marrow of rousette bats. Infection with a bat isolate of MARV resulted in a low level of transcription in these cells and significantly downregulated DC maturation and adaptive immune-stimulatory pathways while simultaneously upregulating interferon-related pathogen-sensing pathways. This study provides a first insight into how the bat immune response is directed toward preventing aberrant inflammatory responses while mounting an antiviral response to defend against MARV infection.IMPORTANCE Marburg viruses (MARVs) cause severe human disease resulting from aberrant immune responses. Dendritic cells (DCs) are primary targets of infection and are dysregulated by MARV. Dysregulation of DCs facilitates MARV replication and virus dissemination and influences downstream immune responses that result in immunopathology. Egyptian rousette bats (ERBs) are natural reservoirs of MARV, and infection results in virus replication and shedding, with asymptomatic control of the virus within weeks. The mechanisms that bats employ to appropriately respond to infection while avoiding disease are unknown. Because DC infection and modulation are important early events in human disease, we measured the transcriptional responses of ERB DCs to MARV. The significance of this work is in identifying cell type-specific coevolved responses between ERBs and MARV, which gives insight into how bat reservoirs are able to harbor MARV and permit viral replication, allowing transmission and maintenance in the population while simultaneously preventing immunopathogenesis.

Assessment of Inhibitors of Pathogenic Crimean-Congo Hemorrhagic Fever Virus Strains Using Virus-Like Particles.

Crimean-Congo hemorrhagic fever (CCHF) is an often lethal, acute inflammatory illness that affects a large geographic area. The disease is caused by infection with CCHF virus (CCHFV), a nairovirus from the Bunyaviridae family. Basic research on CCHFV has been severely hampered by biosafety requirements and lack of available strains and molecular tools. We report the development of a CCHF transcription- and entry-competent virus-like particle (tecVLP) system that can be used to study cell entry and viral transcription/replication over a broad dynamic range (~4 orders of magnitude). The tecVLPs are morphologically similar to authentic CCHFV. Incubation of immortalized and primary human cells with tecVLPs results in a strong reporter signal that is sensitive to treatment with neutralizing monoclonal antibodies and by small molecule inhibitors of CCHFV. We used glycoproteins and minigenomes from divergent CCHFV strains to generate tecVLPs, and in doing so, we identified a monoclonal antibody that can prevent cell entry of tecVLPs containing glycoproteins from 3 pathogenic CCHFV strains. In addition, our data suggest that different glycoprotein moieties confer different cellular entry efficiencies, and that glycoproteins from the commonly used strain IbAr10200 have up to 100-fold lower ability to enter primary human cells compared to glycoproteins from pathogenic CCHFV strains.