Ebola disease (EBOD) in humans is a severe disease caused by at least four related viruses in the genus Orthoebolavirus, most often by the eponymous Ebola virus. Due to human-to-human transmission and incomplete success in treating cases despite promising therapeutic development, EBOD is a high priority in public health research. Yet despite almost 50 years since EBOD was first described, the sources of these viruses remain undefined and much remains to be understood about the disease epidemiology and virus emergence and spread. One important approach to improve our understanding is detection of antibodies that can reveal past human infections. However, serosurveys routinely describe seroprevalences that imply infection rates much higher than those clinically observed. Proposed hypotheses to explain this difference include existence of common but less pathogenic strains or relatives of these viruses, misidentification of EBOD as something else, and a higher proportion of subclinical infections than currently appreciated. The work presented here maps B-cell epitopes in the spike protein of Ebola virus and describes a single epitope that is cross-reactive with an antigen seemingly unrelated to orthoebolaviruses. Antibodies against this epitope appear to explain most of the unexpected reactivity towards the spike, arguing against common but unidentified infections in the population. Importantly, antibodies of cross-reactive donors from within and outside the known EBOD geographic range bound the same epitope. In light of this finding, it is plausible that epitope mapping enables broadly applicable specificity improvements in the field of serology.

Immunizing mice with Crimean-Congo hemorrhagic fever virus (CCHFV) nucleoprotein (NP), glycoprotein precursor (GPC), or with the GP38 domain of GPC, can be protective when the proteins are delivered with viral vectors or as a DNA or RNA vaccine. Subunit vaccines are a safe and cost-effective alternative to some vaccine platforms, but Gc and Gn glycoprotein subunit vaccines for CCHFV fail to protect despite eliciting high levels of neutralizing antibodies. Here, we investigated humoral and cellular immune responses and the protective efficacy of recombinant NP, GP38, and GP38 forms (GP85 and GP160) associated with the highly glycosylated mucin-like (MLD) domain, as well as the NP + GP38 combination. Vaccination with GP160, GP85, or GP38 did not confer protection, and vaccination with the MLD-associated GP38 forms blunted the humoral immune responses to GP38, worsened clinical chemistry, and increased viral RNA in the blood compared to the GP38 vaccination. In contrast, NP vaccination conferred 100% protection from lethal outcome and was associated with mild clinical disease, while the NP + GP38 combination conferred even more robust protection by reducing morbidity compared to mice receiving NP alone. Thus, recombinant CCHFV NP alone is a promising vaccine candidate conferring 100% survival against heterologous challenge. Moreover, incorporation of GP38 should be considered as it further enhances subunit vaccine efficacy by reducing morbidity in surviving animals.

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne nairovirus with a wide geographic spread that can cause severe and lethal disease. No specific medical countermeasures are approved to combat this illness. The CCHFV L protein contains an ovarian tumor (OTU) domain with a cysteine protease thought to modulate cellular immune responses by removing ubiquitin and ISG15 post-translational modifications from host and viral proteins. Viral deubiquitinases like CCHFV OTU are attractive drug targets, as blocking their activity may enhance cellular immune responses to infection, and potentially inhibit viral replication itself. We previously demonstrated that the engineered ubiquitin variant CC4 is a potent inhibitor of CCHFV replication in vitro. A major challenge of the therapeutic use of small protein inhibitors such as CC4 is their requirement for intracellular delivery, e.g., by viral vectors. In this study, we examined the feasibility of in vivo CC4 delivery by a replication-deficient recombinant adenovirus (Ad-CC4) in a lethal CCHFV mouse model. Since the liver is a primary target of CCHFV infection, we aimed to optimize delivery to this organ by comparing intravenous (tail vein) and intraperitoneal injection of Ad-CC4. While tail vein injection is a traditional route for adenovirus delivery, in our hands intraperitoneal injection resulted in higher and more widespread levels of adenovirus genome in tissues, including, as intended, the liver. However, despite promising in vitro results, neither route of in vivo CC4 treatment resulted in protection from a lethal CCHFV infection.

Several filoviruses, including Marburg virus (MARV), cause severe disease in humans and nonhuman primates (NHPs). However, the Egyptian rousette bat (ERB, Rousettus aegyptiacus), the only known MARV reservoir, shows no overt illness upon natural or experimental infection, which, like other bat hosts of zoonoses, is due to well-adapted, likely species-specific immune features. Despite advances in understanding reservoir immune responses to filoviruses, ERB peripheral blood responses to MARV and how they compare to those of diseased filovirus-infected spillover hosts remain ill-defined. We thus conducted a longitudinal analysis of ERB blood gene responses during acute MARV infection. These data were then contrasted with a compilation of published primate blood response studies to elucidate gene correlates of filovirus protection versus disease. Our work expands on previous findings in MARV-infected ERBs by supporting both host resistance and disease tolerance mechanisms, offers insight into the peripheral immunocellular repertoire during infection, and provides the most direct known cross-examination between reservoir and spillover hosts of the most prevalently-regulated response genes, pathways and activities associated with differences in filovirus pathogenesis and pathogenicity.

Nipah virus (NiV) is a highly pathogenic paramyxovirus. The Syrian hamster model recapitulates key features of human NiV disease and is a critical tool for evaluating antivirals and vaccines. Here we describe longitudinal humoral immune responses in NiV-infected Syrian hamsters. Samples were obtained 1-28 days after infection and analyzed by ELISA, neutralization, and Fc-mediated effector function assays. NiV infection elicited robust antibody responses against the nucleoprotein and attachment glycoprotein. Levels of neutralizing antibodies were modest and only detectable in surviving animals. Fc-mediated effector functions were mostly observed in nucleoprotein-targeting antibodies. Antibody levels and activities positively correlated with challenge dose.

Ebola disease outbreaks are major public health events because of human-to-human transmission and high mortality. These outbreaks are most often caused by Ebola virus, but at least three related viruses can also cause the disease. In 2022, Sudan virus re-emerged causing more than 160 confirmed and probable cases. This report describes generation of a recombinant Sudan virus and demonstrates its utility by quantifying antibody cross-reactivity between Ebola and Sudan virus glycoproteins after human infection or vaccination with a licensed Ebola virus vaccine.

Nipah virus (NiV) causes a highly lethal disease in humans who present with acute respiratory or neurological signs. No vaccines against NiV have been approved to date. Here, we report on the clinical impact of a novel NiV-derived nonspreading replicon particle lacking the fusion (F) protein gene (NiVΔF) as a vaccine in three small animal models of disease. A broad antibody response was detected that included immunoglobulin G (IgG) and IgA subtypes with demonstrable Fc-mediated effector function targeting multiple viral antigens. Single-dose intranasal vaccination up to 3 days before challenge prevented clinical signs and reduced virus levels in hamsters and immunocompromised mice; decreases were seen in tissues and mucosal secretions, critically decreasing potential for virus transmission. This virus replicon particle system provides a vital tool to the field and demonstrates utility as a highly efficacious and safe vaccine candidate that can be administered parenterally or mucosally to protect against lethal Nipah disease.

Development of lethal models of Ebola virus disease has been achieved by the serial passage of virus isolates from human cases in mice and guinea pigs. Use of mice infected with non-adapted virus has been limited due to the absence of overt clinical disease. In recent years, newly recognized sequelae identified in human cases has highlighted the importance of continued investigations of non-lethal infection both in humans and animal models. Here, we revisit the use of rodent-adapted and non-adapted Ebola virus (EBOV) variants in mice to investigate infection tolerance and future utility of these models in pathogenesis and therapeutic intervention studies. We found that like non-adapted wild-type EBOV, guinea pig-adapted EBOV results in widespread tissue infection, variably associated with tissue pathology, and alterations in clinical and immunological analytes in the absence of overt disease. Notably, infection with either non-lethal variant does not greatly differ from lethal mouse-adapted EBOV until near the time end-point criteria are reached in these mice, supporting use of these models of virus tolerance for continued investigations of non-lethal infection and sequelae.

Human infection with Sosuga virus (SOSV), a recently discovered pathogenic paramyxovirus, has been reported in one individual to date. No animal models of disease are currently available for SOSV. Here, we describe initial characterization of experimental infection in Syrian hamsters, including kinetics of virus dissemination and replication, and the corresponding clinical parameters, immunological responses, and histopathology. We demonstrate susceptibility of hamsters to infection in the absence of clinical signs or significant histopathologic findings in tissues.

Crimean-Congo Hemorrhagic Fever Virus (CCHFV) causes a life-threatening disease with up to a 40% mortality rate. With no approved medical countermeasures, CCHFV is considered a public health priority agent. The non-neutralizing mouse monoclonal antibody (mAb) 13G8 targets CCHFV glycoprotein GP38 and protects mice from lethal CCHFV challenge when administered prophylactically or therapeutically. Here, we reveal the structures of GP38 bound with a human chimeric 13G8 mAb and a newly isolated CC5-17 mAb from a human survivor. These mAbs bind overlapping epitopes with a shifted angle. The broad-spectrum potential of c13G8 and CC5-17 and the practicality of using them against Aigai virus, a closely related nairovirus were examined. Binding studies demonstrate that the presence of non-conserved amino acids in Aigai virus corresponding region prevent CCHFV mAbs from binding Aigai virus GP38. This information, coupled with in vivo efficacy, paves the way for future mAb therapeutics effective against a wide swath of CCHFV strains.

ABSTRACTLassa fever (LF) is endemic to broad regions of West Africa. Infection with Lassa virus (LASV), the etiologic agent of LF, results in a spectrum of clinical signs in humans, including severe and lethal hemorrhagic disease. Person-to-person transmission occurs through direct contact with body fluids or contaminated bedding and clothing. To investigate transmission risk in acute LASV infection, we evaluated viral RNA and infectious virus obtained from conjunctival, nasal, oral, genital, and rectal swab specimens from guinea pigs modeling lethal and non-lethal LF. Viral RNA and infectious virus were detected in all specimen types beginning 8 days post infection, prior to onset of fever. In the pre-clinical and clinical period, virus was isolated from a subset of nasal, oral, genital, and rectal swabs, and from all conjunctival swabs. Overall, conjunctival and nasal specimens most frequently yielded infectious virus. These findings indicate mucosal transmission risk based on virus isolation from various sites early in infection and support potential utility of minimally invasive specimen evaluation by RT-qPCR for LASV diagnostics.

Defective interfering particles (DIs) contain a considerably smaller genome than the parental virus but retain replication competency. As DIs can directly or indirectly alter propagation kinetics of the parental virus, they offer a novel approach to antiviral therapy, capitalizing on knowledge from natural infection. However, efforts to translate in vitro inhibition to in vivo screening models remain limited. We investigated the efficacy of virus-like particles containing DI genomes (therapeutic infectious particles [TIPs]) in the Syrian hamster model of lethal Nipah virus (NiV) disease. We found that coadministering a high dose of TIPs intraperitoneally with virus challenge improved clinical course and reduced lethality. To mimic natural exposure, we also evaluated lower-dose TIP delivery and virus challenge intranasally, finding equally efficacious reduction in disease severity and overall lethality. Eliminating TIP replicative capacity decreased efficacy, suggesting protection via direct inhibition. These data provide evidence that TIP-mediated treatment can confer protection against disease and lethal outcome in a robust animal NiV model, supporting further development of TIP treatment for NiV and other high-consequence pathogens. IMPORTANCE Here, we demonstrate that treatment with defective interfering particles (DIs), a natural by-product of viral infection, can significantly improve the clinical course and outcome of viral disease. When present with their parental virus, DIs can directly or indirectly alter viral propagation kinetics and exert potent inhibitory properties in cell culture. We evaluated the efficacy of a selection of virus-like particles containing DI genomes (TIPs) delivered intranasally in a lethal hamster model of Nipah virus disease. We demonstrate significantly improved clinical outcomes, including reduction in both lethality and the appearance of clinical signs. This work provides key efficacy data in a robust model of Nipah virus disease to support further development of TIP-mediated treatment against high-consequence viral pathogens.

Lassa virus (LASV) causes mild to severe hemorrhagic fever disease in humans. Strain 13/N guinea pigs are highly susceptible to infection with LASV strain Josiah (clade IV), providing a critical model system for therapeutics and vaccine development. To develop additional models of disease, we detail the clinical course in guinea pigs infected with 5 geographically and genetically diverse LASV strains. Two of the developed models (LASV clades II and III) were then used to evaluate efficacy of a virus replicon particle (VRP) vaccine against heterologous LASV challenge, demonstrating complete protection against clinical disease after a single vaccination dose.

Rift Valley fever virus (RVFV) is an arbovirus found throughout Africa. It causes disease that is typically mild and self-limiting; however, some infected individuals experience severe manifestations, including hepatitis, encephalitis, or even death. Reports of RVFV encephalitis are notable amongst immunosuppressed individuals, suggesting a role for adaptive immunity in preventing this severe complication. This phenomenon has been modeled in C57BL/6 mice depleted of CD4 T cells prior to infection with DelNSs RVFV (RVFV containing a deletion of NSs), resulting in late-onset encephalitis accompanied by high levels of viral RNA in the brain in 30% of animals. In this study, we sought to define the specific type(s) of CD4 T cells that mediate protection from RVFV encephalitis. The viral epitopes targeted by CD4 and CD8 T cells were defined in C57BL/6 mice, and tetramers for both CD4 and CD8 T cells were generated. RVFV-specific CD8 T cells were expanded and of a cytotoxic and proliferating phenotype in the liver following infection. RVFV-specific CD4 T cells were identified in the liver and spleen following infection and phenotyped as largely Th1 or Tfh subtypes. Knock-out mice lacking various aspects of pathways important in Th1 and Tfh development and function were used to demonstrate that T-bet, CD40, CD40L, and MHCII mediated protection from RVFV encephalitis, while IFN-γ and IL-12 were dispensable. Virus-specific antibody responses correlated with protection from encephalitis in all mouse strains, suggesting that Tfh-B cell interactions modulate clinical outcome in this model. Importance: The prevention of RVFV encephalitis requires intact adaptive immunity. In this study we develop reagents to detect RVFV-specific T cells and provide evidence for Tfh cells and CD40/CD40L interactions as critical mediators of this protection.

Crimean-Congo hemorrhagic fever virus (CCHFV) causes mild to severe and fatal disease in humans. Person-to-person transmission is common, necessitating the availability of rapidly deliverable therapeutic and prophylactic interventions to mitigate CCHFV spread. Previously, we showed complete protection using one dose of a viral replicon particle (VRP) vaccine administered 28 days before CCHFV challenge. In order to determine the utility of the VRP vaccine for rapid vaccination protocols, we assessed the efficacy of such vaccination administered at various intervals relative to challenge in IFNAR(-/-) mice. Unvaccinated mice uniformly succumbed to disease by 8 days post infection (dpi). All mice vaccinated 14, 7, or 3 days prior to CCHFV challenge survived infection. Mice vaccinated -14 or -7 dpi were fully protected from clinical disease, whereas mice inoculated -3 dpi developed signs of disease prior to recovering to baseline values 5-9 dpi. These data support the utility of the VRP vaccine for modified short course vaccination protocols to protect against disease and severe outcomes.

Marburg virus (MARV) is among the most virulent pathogens of primates, including humans. Contributors to severe MARV disease include immune response suppression and inflammatory gene dysregulation ("cytokine storm"), leading to systemic damage and often death. Conversely, MARV causes little to no clinical disease in its reservoir host, the Egyptian rousette bat (ERB). Previous genomic and in vitro data suggest that a tolerant ERB immune response may underlie MARV avirulence, but no significant examination of this response in vivo yet exists. Here, using colony-bred ERBs inoculated with a bat isolate of MARV, we use species-specific antibodies and an immune gene probe array (NanoString) to temporally characterize the transcriptional host response at sites of MARV replication relevant to primate pathogenesis and immunity, including CD14(+) monocytes/macrophages, critical immune response mediators, primary MARV targets, and skin at the inoculation site, where highest viral loads and initial engagement of antiviral defenses are expected. Our analysis shows that ERBs upregulate canonical antiviral genes typical of mammalian systems, such as ISG15, IFIT1, and OAS3, yet demonstrate a remarkable lack of significant induction of proinflammatory genes classically implicated in primate filoviral pathogenesis, including CCL8, FAS, and IL6. Together, these findings offer the first in vivo functional evidence for disease tolerance as an immunological mechanism by which the bat reservoir asymptomatically hosts MARV. More broadly, these data highlight factors determining disparate outcomes between reservoir and spillover hosts and defensive strategies likely utilized by bat hosts of other emerging pathogens, knowledge that may guide development of effective antiviral therapies.

Sudden sensorineuronal hearing loss (SNHL) is reported in approximately one-third of survivors of Lassa fever (LF) and remains the most prominent cause of Lassa virus- (LASV) associated morbidity in convalescence. Using a guinea pig model of LF, and incorporating animals from LASV vaccine trials, we investigated viral antigen distribution and histopathology in the ear of infected animals to elucidate the pathogenesis of hearing loss associated with LASV infection. Antigen was detected only in animals that succumbed to disease and was found within structures of the inner ear that are intimately associated with neural detection and/or translation of auditory stimuli and in adjacent vasculature. No inflammation or viral cytopathic changes were observed in the inner ear or surrounding structures in these animals. In contrast, no viral antigen was detected in the ear of surviving animals. However, all survivors that exhibited clinical signs of disease during the course of infection developed perivascular mononuclear inflammation within and adjacent to the ear, indicating an ongoing inflammatory response in these animals that may contribute to hearing loss. These data contribute to the knowledge of LASV pathogenesis in the auditory system, support an immune-mediated process resulting in LASV-associated hearing loss, and demonstrate that vaccination protecting animals from clinical disease can also prevent infection-associated auditory pathology.

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tri-segmented, tick-borne nairovirus that causes disease of ranging severity in humans. The CCHFV M segment encodes a complex glycoprotein precursor (GPC) that undergoes extensive endoproteolytic cleavage, giving rise to two structural proteins (Gn and Gc) required for virus attachment and entry, and to multiple non-structural proteins (NSm, GP160, GP85, and GP38). The functions of these non-structural proteins remain largely unclear. Here, we investigate the role of NSm during infection by generating a recombinant CCHFV lacking the complete NSm domain (10200NSm) and observing CCHFV NSm replication in cell lines and pathogenicity in Ifnar(-/-) mice. Our data demonstrate that the NSm domain is dispensable for viral replication in vitro, and, despite the delayed onset of clinical signs, CCHFV lacking this domain caused severe or lethal disease in infected mice.

Rift Valley fever virus (RVFV) is a zoonotic arbovirus of clinical significance in both livestock and humans. A formalin-inactivated virus preparation was initially developed for human use and tested in laboratory workers in the 1960s. Vaccination resulted in generation of neutralizing antibody titers in most recipients, but neutralization titers waned over time, necessitating frequent booster doses. In this study, T cell-based immune responses to the formalin-inactivated vaccine were examined in a cohort of seven individuals who received between 1 and 6 doses of the vaccine. RVFV-specific T cell responses were detectable up to 24 years post vaccination. Peripheral blood mononuclear cells from this cohort of individuals were used to map out the viral epitopes targeted by T cells in humans. These data provide tools for assessing human RVFV-specific T cell responses and are thus a valuable resource for future human RVFV vaccine efforts.

The error-prone nature of ribonucleic acid (RNA)-dependent RNA polymerases drives the diversity of RNA virus populations. Arising within this diversity is a subset of defective viral genomes that retain replication competency, termed defective interfering (DI) genomes. These defects are caused by aberrant viral polymerase reinitiation on the same viral RNA template (deletion DI species) or the nascent RNA strand (copyback DI species). Defective interfering genomes have previously been shown to alter the dynamics of a viral population by interfering with normal virus replication and/or by stimulating the innate immune response. In this study, we investigated the ability of artificially produced DI genomes to inhibit Nipah virus (NiV), a highly pathogenic biosafety level 4 paramyxovirus. High multiplicity of infection passaging of both NiV clinical isolates and recombinant NiV in Vero cells generated an extensive DI population from which individual DIs were identified using next-generation sequencing techniques. Assays were established to generate and purify both naturally occurring and in silico-designed DIs as fully encapsidated, infectious virus-like particles termed defective interfering particles (DIPs). We demonstrate that several of these NiV DIP candidates reduced NiV titers by up to 4 logs in vitro. These data represent a proof-of-principle that a therapeutic application of DIPs to combat NiV infections may be an alternative source of antiviral control for this disease.

Nipah virus (NiV) is a highly pathogenic zoonotic paramyxovirus that causes fatal encephalitis and respiratory disease in humans. There is currently no approved therapeutic for human use against NiV infection. Griffithsin (GRFT) is high-mannose oligosaccharide binding lectin that has shown in vivo broad-spectrum activity against viruses including severe acute respiratory syndrome coronavirus, human immunodeficiency virus 1, hepatitis C virus, and Japanese encephalitis virus. In this study, we evaluated the in vitro antiviral activities of GRFT and its synthetic trimeric tandemer (3mG) against NiV and other viruses from across 4 virus families. The 3mG had comparatively greater potency than GRFT against NiV due to its enhanced ability to block NiV glycoprotein-induced syncytia formation. Our initial in vivo prophylactic evaluation of an oxidation-resistant GRFT (Q-GRFT) showed significant protection against lethal NiV challenge in Syrian golden hamsters. Our results warrant further development of Q-GRFT and 3mG as potential NiV therapeutics.

Crimean-Congo hemorrhagic fever virus (CCHFV, order Bunyavirales, family Nairoviridae, genus Orthonairovirus) is the tick-borne etiological agent of Crimean-Congo hemorrhagic fever (CCHF) in humans. Animals are generally susceptible to CCHFV infection but refractory to disease. Small animal models are limited to interferon-deficient mice, that develop acute fatal disease following infection. Here, using a ZsGreen1- (ZsG) expressing reporter virus (CCHFV/ZsG), we examine tissue tropism and dissemination of virus in interferon-alpha/beta receptor knock-out (Ifnar-/-) mice. We demonstrate that CCHFV/ZsG retains in vivo pathogenicity comparable to wild-type virus. Interestingly, despite high levels of viral RNA in all organs assessed, 2 distribution patterns of infection were observed by both fluorescence and immunohistochemistry (IHC), corresponding to the permissiveness of organ tissues. To further investigate viral dissemination and to temporally define cellular targets of CCHFV in vivo, mice were serially euthanized at different stages of disease. Flow cytometry was used to characterize CCHFV-associated alterations in hematopoietic cell populations and to classify infected cells in the blood, lymph node, spleen, and liver. ZsG signal indicated that mononuclear phagocytic cells in the lymphatic tissues were early targets of infection; in late-stage infection, overall, the highest levels of signal were detected in the liver, and ZsG was found in both antigen-presenting and lymphocyte cell populations.

Nipah virus ([NiV] family Paramyxoviridae, genus Henipavirus) infection can cause severe respiratory and neurological disease in humans. The pathophysiology of disease is not fully understood, and it may vary by presentation and clinical course. In this study, we investigate changes in blood chemistry in NiV-infected Syrian hamsters that survived or succumbed to disease. Increased sodium and magnesium and decreased albumin and lactate levels were detected in animals euthanized with severe clinical disease compared with mock-infected controls. When subjects were grouped by clinical syndrome, additional trends were discernable, highlighting changes associated with either respiratory or neurological disease.

In the absence of approved vaccines and therapeutics for use in humans, Nipah virus continues to cause fatal outbreaks of encephalitis and respiratory disease in Bangladesh and India on a near-annual basis. We determined that a single dose of a lipid nanoparticle nucleoside-modified messenger RNA vaccine encoding the soluble Hendra virus glycoprotein protected up to 70% of Syrian hamsters from lethal NiV challenge, despite animals having suboptimally primed immune responses before challenge. These data provide a foundation from which to optimize future messenger RNA vaccination studies against NiV and other highly pathogenic viruses.

Using a recombinant Nipah virus expressing a fluorescent protein (ZsG), we visualized virus tropism in the Syrian hamster model. We found that anatomical localization of fluorescence correlated to clinical signs; signal was primarily visualized in the respiratory tract in animals with acute-onset terminal disease, whereas central nervous system localization was seen in animals that succumbed with delayed disease onset. While polymerase chain reaction (PCR) detection corresponded well to ZsG signal, virus was only isolated from some lung, brain, liver, and kidney samples that were ZsG and/or PCR positive, and only from animals euthanized on or before 15 days post infection.

Since its recent discovery, Bourbon virus has been isolated from a human and ticks. To assess exposure of potential vertebrate reservoirs, we assayed banked serum and plasma samples from wildlife and domestic animals in Missouri, USA, for Bourbon virus-neutralizing antibodies. We detected high seroprevalence in raccoons (50%) and white-tailed deer (86%).

No vaccines are currently licensed to prevent Crimean-Congo hemorrhagic fever virus (CCHFV) infection, which can cause mild self-limiting clinical signs or severe, often fatal hemorrhagic fever disease. Here we continued investigations into the utility of a single-dose virus replicon particle (VRP) vaccine regimen by assessing protection against Turkey or Oman strains of CCHFV. We found that all mice were completely protected from disease, supporting broad applicability of this platform for CCHFV prevention.

Operating clinical analyzers within recommended parameters can be challenging during outbreak response. Using the Piccolo Xpress point-of-care blood chemistry analyzer on guinea pig blood, we found that values of many analytes are still readily comparable when samples and reagent discs are handled at various conditions outside of manufacturer recommendations.

Inbred Strain 13/N Guinea Pigs are Frequently Used As Animal Models in Studies of Emerging and High-pathogenicity Viruses. To Date, Clinical Reference Intervals Have Not Been Established for Hematology and Clinical Chemistry Parameters in This Strain. We Obtained Whole-blood Samples from the Cranial Vena Cava of Healthy Strain 13/N Colony Animals for Inhouse Cbc and Clinical Chemistry Analyses. Analyte Values Were Investigated to Determine Subpopulation Differences According to Age and Sex. Glucose, Albumin, Alp, Lymphocyte Percentage, Hgb, and Mchc Decreased with Age, Whereas Neutrophil and Monocyte Percentages, Bun, Creatinine, Calcium, and Amylase Increased with Age. Total Protein and Wbc Counts Increased Over the First 300 D of Life Before Stabilizing. Across All Age Categories, Female Guinea Pigs Consistently Had Lower Rbc, Hct, Hgb, Alt, Alp, and Amylase Levels and Higher Mcv Values Than Males. These Trends Were Strongest in Adults (age, 151 Through 900 D). Most Parameters Stabilized by 300 D; Previous Studies Used 60 D or 120 D As Adult Age and 90 to 120 D As Sexual Maturity. We Recommend Age Group Definitions of 0 Through 150 D for Juveniles, 151 Through 900 D for Adults, and Older Than 900 D for Geriatric Adult Strain 13/N Guinea Pigs.

Lassa fever is a frequently severe human disease that is endemic to several countries in West Africa. To date, no licensed vaccines are available to prevent Lassa virus (LASV) infection, even though Lassa fever is thought to be an important disease contributing to mortality and both acute and chronic morbidity. We have previously described a vaccine candidate composed of single-cycle LASV replicon particles (VRPs) and a stable cell line for their production. Here, we refine the genetic composition of the VRPs and demonstrate the ability to reproducibly purify them with high yields. Studies in the guinea pig model confirm efficacy of the vaccine candidate, demonstrate that single-cycle replication is necessary for complete protection by the VRP vaccine, and show that post-exposure vaccination can confer protection from lethal outcome.