A live-attenuated chlamydial vaccine protects against trachoma in nonhuman primates

In cynomolgus macaques, ocular infection with a live trachoma strain lacking the conserved 7.5-kb plasmid induced no ocular pathology but facilitated solid or partial protection from subsequent infection with a virulent strain of trachoma

TRIM5alpha Restricts Flavivirus Replication by Targeting the Viral Protease for Proteasomal Degradation

Tripartite motif-containing protein 5alpha (TRIM5alpha) is a cellular antiviral restriction factor that prevents early events in retrovirus replication. The activity of TRIM5alpha is thought to be limited to retroviruses as a result of highly specific interactions with capsid lattices. In contrast to this current understanding, we show that both human and rhesus macaque TRIM5alpha suppress replication of specific flaviviruses. Multiple viruses in the tick-borne encephalitis complex are sensitive to TRIM5alpha-dependent restriction, but mosquito-borne flaviviruses, including yellow fever, dengue, and Zika viruses, are resistant. TRIM5alpha suppresses replication by binding to the viral protease NS2B/3 to promote its K48-linked ubiquitination and proteasomal degradation. Importantly, TRIM5alpha contributes to the antiviral function of IFN-I against sensitive flaviviruses in human cells. Thus, TRIM5alpha possesses remarkable plasticity in the recognition of diverse virus families, with the potential to influence human susceptibility to emerging flaviviruses of global concern

Preservation of scRNA-Seq Libraries Using Existing Inactivation Protocols

Single-cell RNA sequencing has soared in popularity in recent years. The ability to deeply profile the states of individual cells during the course of disease or infection has helped to expand our knowledge of coordinated responses. However, significant challenges arise when performing this analysis in high containment settings such as biosafety level 3 (BSL-3), BSL-3+ and BSL-4. Working in containment is necessary for many important pathogens, such as Ebola virus, Marburg virus, Lassa virus, Nipah and Hendra viruses. Since standard operating procedures (SOPs) for inactivation are extensive and may compromise sample integrity, we tested whether the removal of single-cell sequencing libraries from containment laboratories using existing inactivation protocols for nucleic acid extraction (Trizol, RLT buffer, or AVL buffer) was feasible. We have demonstrated that the inactivation does not affect sample quality and can work with existing methods for inactivation

Frameshift Mutations in a Single Novel Virulence Factor Alter the In Vivo Pathogenicity of Chlamydia trachomatis for the Female Murine Genital Tract▿ ¶ ‖

Chlamydia trachomatis is a human pathogen of global importance. An obstacle to studying the pathophysiology of human chlamydial disease is the lack of a suitable murine model of C. trachomatis infection. Mice are less susceptible to infection with human isolates due in part to innate mouse-specific host defense mechanisms to which human strains are sensitive. Another possible factor that influences the susceptibility of mice to infection is that human isolates are commonly cultivated in vitro prior to infection of mice; therefore, virulence genes could be lost as a consequence of negative selective pressure. We tested this hypothesis by infecting innate immunity-deficient C3H/HeJ female mice intravaginally with a human serovar D urogenital isolate that had undergone multiple in vitro passages. We observed early and late infection clearance phenotypes. Strains of each phenotype were isolated and then used to reinfect naïve mice. Following infection, the late-clearance strain was significantly more virulent. It caused unvarying infections of much longer durations with greater infectious burdens that naturally ascended to the upper genital tract, causing salpingitis. Despite contrasting in vivo virulence characteristics, the strains exhibited no differences in the results of in vitro infectivity assays or sensitivities to gamma interferon. Genome sequencing of the strains revealed mutations that localized to a single gene (CT135), implicating it as a critical virulence factor. Mutations in CT135 were not unique to serovar D but were also found in multiple oculogenital reference strains. Our findings provide new information about the pathogenomics of chlamydial infection and insights for improving murine models of infection using human strains

A Systems Approach Reveals MAVS Signaling in Myeloid Cells as Critical for Resistance to Ebola Virus in Murine Models of Infection

The unprecedented 2013–2016 outbreak of Ebola virus (EBOV) resulted in over 11,300 human deaths. Host resistance to RNA viruses requires RIG-I-like receptor (RLR) signaling through the adaptor protein, mitochondrial antiviral signaling protein (MAVS), but the role of RLR-MAVS in orchestrating anti-EBOV responses in vivo is not known. Here we apply a systems approach to MAVS−/− mice infected with either wild-type or mouse-adapted EBOV. MAVS controlled EBOV replication through the expression of IFNα, regulation of inflammatory responses in the spleen, and prevention of cell death in the liver, with macrophages implicated as a major cell type influencing host resistance. A dominant role for RLR signaling in macrophages was confirmed following conditional MAVS deletion in LysM+ myeloid cells. These findings reveal tissue-specific MAVS-dependent transcriptional pathways associated with resistance to EBOV, and they demonstrate that EBOV adaptation to cause disease in mice involves changes in two distinct events, RLR-MAVS antagonism and suppression of RLR-independent IFN-I responses

Murine Chlamydia trachomatis Genital Infection Is Unaltered by Depletion of CD4+ T cells and Diminished Adaptive Immunity

Chlamydia muridarum and Chlamydia trachomatis mouse models of genital infection have been used to study chlamydial immunity and vaccine development. To assess the protective role of CD4+ T cells in resolving C. trachomatis and C. muridarum genital tract infections, we used the female mouse model and evaluated infection in the presence and absence of CD4+ T cells. In contrast to C. muridarum infection, C. trachomatis infection was unaltered in the absence of CD4+ T cells. Mice infected with C. trachomatis developed protective immunity to re-challenge, but unlike C. muridarum infection, optimum resistance required multiple infectious challenges, despite the generation of adaptive serum and local chlamydial specific immune responses. Thus, understanding the chlamydial pathogenic and host immunologic factors that result in a diminished protective role for CD4+ T cells in C. trachomatis murine infection might lead to new insights important to human immunity and vaccine development

Genetically diverse mouse models of SARS-CoV-2 infection reproduce clinical variation in type I interferon and cytokine responses in COVID-19

Abstract Inflammation in response to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection drives severity of coronavirus disease 2019 (COVID-19) and is influenced by host genetics. To understand mechanisms of inflammation, animal models that reflect genetic diversity and clinical outcomes observed in humans are needed. We report a mouse panel comprising the genetically diverse Collaborative Cross (CC) founder strains crossed to human ACE2 transgenic mice (K18-hACE2) that confers susceptibility to SARS-CoV-2. Infection of CC x K18-hACE2 resulted in a spectrum of survival, viral replication kinetics, and immune profiles. Importantly, in contrast to the K18-hACE2 model, early type I interferon (IFN-I) and regulated proinflammatory responses were required for control of SARS-CoV-2 replication in PWK x K18-hACE2 mice that were highly resistant to disease. Thus, virus dynamics and inflammation observed in COVID-19 can be modeled in diverse mouse strains that provide a genetically tractable platform for understanding anti-coronavirus immunity