Biology subjects

Virtaneva, K.

Publications and source records attributed to Virtaneva, K..

3 recordsLinked to original sources

bioRxiv2022

A toxin-antitoxin system ensures plasmid stability in Coxiella burnetii

Coxiella burnetii is the causative agent of Q fever. All C. burnetii isolates encode either an autonomous replicating plasmid (QpH1, QpDG, QpRS, or QpDV) or QpRS-like chromosomally integrated plasmid sequences. The role of the ORFs present on these sequences is unknown. Here, the role of the ORFs encoded on QpH1 was investigated. Using a new C. burnetii shuttle vector (pB-TyrB-QpH1ori) we cured Nine Mile Phase II of QpH1. The {Delta}QpH1 strain grew normally in axenic media but had a significant growth defect in Vero cells, indicating QpH1 was important for C. burnetii virulence. We developed an inducible CRISPR interference system to examine the role of individual QpH1 plasmid genes. CRISPRi of cbuA0027 resulted in significant growth defects in axenic media and THP-1 cells. The cbuA0028/cbuA0027 operon encodes CBUA0028 and CBUA0027, which are homologous to the HigB2 toxin and HigA2 anti-toxin, respectively, from Vibrio cholerae. Consistent with toxin-antitoxin systems, overexpression of cbuA0028 resulted in a severe intracellular growth defect that was rescued by co-expression of cbuA0027. CBUA0028 inhibited protein translation. CBUA0027 bound the cbuA0028 promoter (PcbuA0028) and CBUA0028, with the resulting complex binding also PcbuA0028. In summary, our data indicates C. burnetii maintains an autonomously replicating plasmid because of a plasmid-based toxin-antitoxin system.

microbiology↗

bioRxiv2022

Imbalanced immune response and dysregulation of neural functions underline fatal opportunistic encephalitis caused by astrovirus

The incidence of infections of the central nervous system (CNS) in humans is increasing due to emergence and reemergence of pathogens and an increase in the number of immunocompromised patients. Many viruses are opportunists and can invade the CNS if the immune response of the host is impaired. Here we investigate neuropathogenesis of a rare CNS infection in immunocompromised patients caused by astrovirus and show that it shares many features with another opportunistic infection of the CNS caused by human immunodeficiency virus. We show that astrovirus infects CNS neurons with a major impact on the brainstem. In the setting of impaired peripheral adaptive immunity, host responses in the astrovirus infected brain are skewed to the innate immune response with exuberant activation of microglia and macrophages. Astrovirus infection of neurons and responses by phagocytic cells lead to disrupted synaptic integrity, loss of afferent innervation related to infected neurons, and global impairment of both excitatory and inhibitory neurotransmission. The response employed in the CNS against opportunistic viruses, such as astrovirus and HIV, may be a common compensatory defense mechanism which inadvertently leads to loss of neural functions due to the hosts exuberant innate immune response to pathogens when adaptive immunity is impaired.

microbiology↗

bioRxiv2018

Clinical Characterization of Host Response to Simian Hemorrhagic Fever Virus Infection in Permissive and Refractory Hosts: A Model for Determining Mechanisms of VHF Pathogenesis

Simian hemorrhagic fever virus (SHFV) causes a fulminant and typically lethal viral hemorrhagic fever (VHF) in macaques (Cercopithecinae: Macaca spp.) but causes subclinical infections in patas monkeys (Cercopithecinae: Erythrocebus patas). This difference in disease course offers a unique opportunity to compare host-responses to infection by a VHF-causing virus in biologically similar susceptible and refractory animals. Patas and rhesus monkeys were inoculated side-by-side with SHFV. In contrast to the severe disease observed in rhesus monkeys, patas monkeys developed a limited clinical disease characterized by changes in complete blood counts, serum chemistries, and development of lymphadenopathy. Viremia was measurable 2 days after exposure and its duration varied by species. Infectious virus was detected in terminal tissues of both patas and rhesus monkeys. Varying degrees of overlap in changes in serum concentrations of IFN-{gamma}, MCP-1, and IL-6 were observed between patas and rhesus monkeys, suggesting the presence of common and species-specific cytokine responses to infection. Similarly, quantitative immunohistochemistry of terminal livers and whole blood flow cytometry revealed varying degrees of overlap in changes in macrophages, natural killer cells, and T-cells. The unexpected degree of overlap in host-response suggests that relatively small subsets of a hosts response to infection may be responsible for driving pathogenesis that results in a hemorrhagic fever. Furthermore, comparative SHFV infection in patas and rhesus monkeys offers an experimental model to characterize host-response mechanisms associated with viral hemorrhagic fever and evaluate pan-viral hemorrhagic fever countermeasures.\n\nIMPORTANCEHost-response mechanisms involved in pathogenesis of VHFs remain poorly understood. An underlying challenge is separating beneficial, inconsequential, and detrimental host-responses during infection. The comparison of host-responses to infection with the same virus in biologically similar animals that have drastically different disease manifestations allows for the identification of pathogenic mechanisms. SHFV, a surrogate virus for human VHF-causing viruses likely causes subclinical infection in African monkeys such as patas monkeys but can cause severe disease in Asian macaque monkeys. Data from the accompanying article by Buechler et al. support that infection of macaques and baboons with non-SHFV simarteviruses can establish persistent or long-term subclinical infections. Baboons, macaques, and patas monkeys are relatively closely taxonomically related (Cercopithecidae: Cercopithecinae) and therefore offer a unique opportunity to dissect how host-response differences determine disease outcome in VHFs.

immunology↗