Biology subjects
Publications and source records attributed to Munster, V..
We compared clinical disease, virus shedding and dissemination following genital MPXV clade Ia and Ib infections in Mastomys natalensis. MPXV clade Ib resulted in a milder clinical disease but a similar shedding profile to clade Ia. These findings indicate a prolonged pre-symptomatic or prodromal shedding period in clade Ib infections.
The transmission pattern of mpox has shifted from sporadic zoonotic outbreaks to sustained human-to-human spread. Epidemiological data indicate sexual contact as a crucial driver for efficient transmission and the associated devastating mpox outbreaks in recent years. However, our understanding of exact driving factors and transmission determinants is still limited. Here, we investigated MPXV clade Ia virus pathogenicity, shedding kinetics, and transmission potential in a prairie dog model (Cynomys ludovicianus). All tested mucosal inoculation routes (penile/preputial, vaginal, rectal, intranasal) resulted in a productive, systemic infection. Inoculation via urogenital routes generated the highest virus shedding and most severe clinical disease. A simulated sexual contact transmission resulted in 100% transmission efficiency with high virus shedding in sentinels on day 1, even before the onset of clinical signs. Our findings provide critical insights into mpox transmission, emphasizing the role of anogenital mucosal surfaces in facilitating rapid spread. These results advocate for a stronger focus on mucosal infection when evaluating countermeasures.
The ongoing outbreak of highly pathogenic avian influenza virus (HPAIV) subtype H5N1 in the U.S. poses a significant public health threat. To date, 70 human cases have been confirmed in the United States, including two severe cases and one fatality. While suitable animal models are crucial for predicting the potential pandemic risk of newly emerging pathogens in humans, studies investigating contemporary HPAIV H5N1 transmission dynamics remain limited. Here, we investigated the pathogenicity and transmission efficiency of three recent clade 2.3.4.4b H5N1 viruses isolated from a bovine, mountain lion, and a human case using Syrian hamsters. Intranasal inoculation with 104 TCID50 resulted in productive virus replication in the respiratory tract and shedding for all three isolates. Transmission studies showed limited efficiency via direct contact and airborne routes for all three isolates. Although overall transmission was inefficient, the human H5N1 isolate demonstrated relatively greater contact transmissibility than the bovine and mountain lion isolates. Taken together, our data demonstrate that the Syrian hamster model complements existing animal models for influenza A virus research and expands the resources available for investigating the pathogenicity, transmissibility, and efficacy of countermeasures against HPAIV H5N1. One sentence summaryHuman HPAIV H5N1 exhibits comparatively higher contact transmissibility than bovine and mountain lion isolates, despite limited overall transmission.
H5N1 influenza outbreaks in dairy cows necessitate studying potential transmission routes among livestock and to humans. We measured the stability of infectious H5N1 influenza virus in raw milk, wastewater, and on contaminated surfaces. We found relatively slow decay in milk, indicating that contaminated milk and fomites pose plausible transmission risks.
Ebola virus (EBOV) and Marburg virus (MARV) are zoonotic filoviruses that cause hemorrhagic fever in humans. Bat species in both Chiropteran suborders host filoviruses, suggesting that bats may have coevolved with this viral family. Correlative data implicate bats as natural EBOV hosts, but neither a full-length genome nor an EBOV isolate has been found in any bats sampled. Here, we modelled filovirus infection in the Jamaican fruit bat (JFB), Artibeus jamaicensis. Bats were inoculated with either EBOV or MARV through a combination of oral, intranasal, and subcutaneous routes. EBOV-infected bats supported systemic virus replication and shed infectious virus orally. In contrast, MARV replicated only transiently and was not shed. In vitro, JFB cells replicate EBOV more efficiently than MARV, and MARV infection induced innate antiviral responses that EBOV efficiently suppressed. Experiments using VSV pseudoparticles or replicating VSV expressing the EBOV or MARV glycoprotein demonstrated an advantage for EBOV entry and replication early, respectively, in JFB cells. Overall, this study describes filovirus species-specific phenotypes for both JFB and their cells.
The emergence of the Omicron lineage represented a major genetic drift in SARS-CoV-2 evolution. This was associated with phenotypic changes including evasion of pre-existing immunity and decreased disease severity. Continuous evolution within the Omicron lineage raised concerns of potential increased transmissibility and/or disease severity. To address this, we evaluated the fitness and pathogenesis of contemporary Omicron variants XBB.1.5, XBB.1.16, EG.5.1, and JN.1 in the upper (URT) and lower respiratory tract (LRT). We compared in vivo infection in Syrian hamsters with infection in primary human nasal and lung epithelium cells and assessed differences in transmissibility, antigenicity, and innate immune activation. Omicron variants replicated efficiently in the URT but displayed limited pathology in the lungs compared to previous variants and failed to replicate in human lung organoids. JN.1 was attenuated in both URT and LRT compared to other Omicron variants and failed to transmit in the hamster model. Our data demonstrate that Omicron lineage evolution has favored increased fitness in the URT.
Since 2002, three novel coronavirus outbreaks have occurred: severe acute respiratory syndrome coronavirus (SARS-CoV-1), Middle East respiratory syndrome coronavirus (MERS-CoV), and SARS-CoV-2. A better understanding of the transmission potential of coronaviruses will result in adequate infection control precautions and an early halt of transmission within the human population. Experiments on the stability of coronaviruses in the environment, as well as transmission models, are thus pertinent. Here, we show that transgenic mice expressing human DPP4 can be infected with MERS-CoV via the aerosol route. Exposure to 5x106 TCID50 and 5x104 TCID50 MERS-CoV per cage via fomites resulted in transmission in 15 out of 20 and 11 out of 18 animals, respectively. Exposure of sentinel mice to donor mice one day post inoculation with 105 TCID50 MERS-CoV resulted in transmission in 1 out of 38 mice via direct contact and 4 out of 54 mice via airborne contact. Exposure to donor mice inoculated with 104 TCID50 MERS-CoV resulted in transmission in 0 out of 20 pairs via direct contact and 0 out of 5 pairs via the airborne route. Our model shows limited transmission of MERS-CoV via the fomite, direct contact, and airborne routes. The hDPP4 mouse model will allow assessment of the ongoing evolution of MERS-CoV in the context of acquiring enhanced human-to-human transmission kinetics and will inform the development of other transmission models.
Lassa Fever, caused by Lassa virus (LASV), is endemic to West Africa, where approximately 300,000 illnesses and 5,000 deaths occur annually. LASV is primarily spread by infected multimammate rats via urine and fomites, highlighting the importance of understanding the environmental fate of LASV. This study evaluated the persistence of LASV strains on surfaces in aqueous solutions and with sodium hypochlorite disinfection. LASV strains (Josiah and Sauerwald) were more stable in DI water (k = 0.23 and 0.34 days-1) than primary influent wastewater (k = 1.3 and 1.9 days-1). The decay rates of LASV on HDPE (k = 4.3 and 2.3 days-1) and Stainless Steel (k = 5.3 and 2.7 days-1) were not significantly different for either strain. Sodium hypochlorite was highly effective at inactivating both strains of LASV. This work presents data for the environmental persistence of LASV to inform future risk assessment and management efforts.
ImportanceSince May 2022, human monkeypox (mpox) infections have spread rapidly outside endemic countries. On July 23, 2023, WHO declared a Public Health Emergency of international Concern because of the unprecedented global spread of mpox. Whereas there is an incomplete understanding of transmission routes, the spread of monkeypox virus (MPXV) through sexual contact networks of men who have sex with men (MSM) highlights the potential of transmission during sexual activity, either via bodily fluids or via direct contact. This research assesses the potential for MPXV to remain infectious in the environment on surfaces and in fluids under different environmental conditions. ObjectiveTo investigate the stability of MPXV on various surfaces, at different environmental conditions and in different bodily fluids (human blood, semen, serum, saliva, urine, and feces), and to assess decontamination of MPXV-contaminated wastewater via chlorination. Design, Setting, and ExposuresAll experiments involving viable MPXV were performed at the Rocky Mountains Laboratory under high containment conditions using MPXV strain hMPXV/USA/MA001. Infectious MPXV was quantified via plaque assay. Environmental decay rates were estimated using a Bayesian statistical model, with a Poisson likelihood for plaque counts. ResultsMPXV showed surface dependent stability, with faster decay at higher temperatures. Decay rates varied considerably depending on the medium in which virus was suspended, both overall MPXV displayed considerable environmental stability in bodily fluids and in particular proteinaceous fluids, such as blood and semen, lead to greater persistence. Wastewater chlorination was an effective decontamination technique. Conclusions and RelevanceMPXV retains its infectivity in the environment when it is deposited in blood, semen, and serum; environmental decay is more rapid in less proteinaceous fluids, particularly once residual liquid has evaporated. The observed persistence of MPXV implies environmental contamination in healthcare setting, could serve as vehicles of transmission and dissemination in these environments. Chlorination was effective in decontamination of wastewater. Key findings and public health implications; these results suggest that MPXV can have prolonged stability in the environment and are therefore directly relevant for hospital hygiene practices to prevent nosocomial transmission.
SARS-CoV-2 is transmitted principally via air; contact and fomite transmission may also occur. Variants-of-concern (VOCs) are more transmissible than ancestral SARS-CoV-2. We find that early VOCs show greater aerosol and surface stability than the early WA1 strain, but Delta and Omicron do not. Stability changes do not explain increased transmissibility.
Nipah virus (NiV) is a highly pathogenic paramyxovirus capable of causing severe respiratory and neurologic disease in humans. Currently, there are no licensed vaccines or therapeutics against NiV, underscoring the urgent need for the development of countermeasures. The NiV surface-displayed glycoproteins, NiV-G and NiV-F, mediate host cell attachment and fusion, respectively, and are heavily targeted by host antibodies. Here, we describe a vaccination-derived neutralizing monoclonal antibody, mAb92, that targets NiV-F. Structural characterization of the fab region bound to NiV-F (NiV-F-Fab92) by cryo-electron microscopy analysis reveals an epitope in the DIII domain at the membrane distal apex of NiV-F, an established site of vulnerability on the NiV surface. Further, prophylactic treatment of hamsters with mAb92 offered complete protection from NiV disease, demonstrating beneficial activity of mAb92 in vivo. This work provides support for targeting NiV-F in the development of vaccines and therapeutics against NiV.
Since the emergence of SARS-CoV-2, five different variants of concern (VOCs) have been identified: Alpha, Beta, Gamma, Delta, and Omicron. Due to confounding factors in the human population, such as pre-existing immunity, comparing severity of disease caused by different VOCs is challenging. Here, we investigate disease progression in the rhesus macaque model upon inoculation with the Delta, Omicron BA.1, and Omicron BA.2 VOCs. Disease severity in rhesus macaques inoculated with Omicron BA.1 or BA.2 was lower than those inoculated with Delta and resulted in significantly lower viral loads in nasal swabs, bronchial cytology brush samples, and lung tissue in rhesus macaques. Cytokines and chemokines were upregulated in nasosorption samples of Delta animals compared to Omicron BA.1 and BA.2 animals. Overall, these data suggests that in rhesus macaques, Omicron replicates to lower levels than the Delta VOC, resulting in reduced clinical disease.
Behavioral and medical control measures are not effective in containing the spread of SARS-CoV-2. Here we report on the effectiveness of a preemptive environmental strategy using UV-C light to prevent airborne transmission of the virus in a hamster model and show that UV-C exposure completely prevents airborne transmission between individuals
Advanced age is a key predictor of severe COVID-19. To gain insight into this relationship, particularly with respect to immune responses, we utilized the rhesus macaque model of SARS-CoV-2 infection. Two cohorts of eight older (16-23 years) and eight younger (3-5 years) rhesus macaques were inoculated with SARS-CoV-2. Animals were evaluated using viral RNA quantification, clinical observations, thoracic radiographs, single-cell transcriptomics, multiparameter flow cytometry, multiplex immunohistochemistry, cytokine detection, and lipidomics analysis at pre-defined timepoints in various tissues. Differences in clinical signs, pulmonary infiltrates, and virus replication dynamics were limited between age cohorts. Transcriptional signatures of inflammation-associated genes in cells isolated from bronchoalveolar lavage fluid at 3 dpi revealed efficient mounting of innate immune defenses in both younger and older animals. These findings suggested that age did not substantially skew major facets of acute disease in this model. However, age-specific divergence of immune responses emerged during the post-acute phase of infection (7-21 dpi). Older animals exhibited sustained local inflammatory innate responses while local effector T-cell responses were induced earlier in the younger animals. Circulating lipid mediator and cytokine levels highlighted increased repair-associated signals in the younger animals, in contrast to persistent pro-inflammatory responses in the older animals. In summary, despite similar disease outcomes, multi-omics profiling in SARS-CoV-2-infected rhesus macaques suggests that age may delay or impair the induction of anti-viral cellular immune responses and delay efficient return to immune homeostasis following acute infection.
As novel SARS-CoV-2 variants continue to emerge, it is critical that their potential to cause severe disease and evade vaccine-induced immunity is rapidly assessed in humans and studied in animal models. In early January 2021, a novel variant of concern (VOC) designated B.1.429 comprising 2 lineages, B.1.427 and B.1.429, was originally detected in California (CA) and shown to enhance infectivity in vitro and decrease antibody neutralization by plasma from convalescent patients and vaccine recipients. Here we examine the virulence, transmissibility, and susceptibility to pre-existing immunity for B 1.427 and B 1.429 in the Syrian hamster model. We find that both strains exhibit enhanced virulence as measured by increased body weight loss compared to hamsters infected with ancestral B.1 (614G), with B.1.429 causing the most body weight loss among all 3 lineages. Faster dissemination from airways to parenchyma and more severe lung pathology at both early and late stages were also observed with B.1.429 infections relative to B.1. (614G) and B.1.427 infections. In addition, subgenomic viral RNA (sgRNA) levels were highest in oral swabs of hamsters infected with B.1.429, however sgRNA levels in lungs were similar in all three strains. This demonstrates that B.1.429 replicates to higher levels than ancestral B.1 (614G) or B.1.427 in the upper respiratory tract (URT) but not in the lungs. In multi-virus in-vivo competition experiments, we found that epsilon (B.1.427/B.1.429) and gamma (P.1) dramatically outcompete alpha (B.1.1.7), beta (B.1.351) and zeta (P.2) in the lungs. In the URT gamma, and epsilon dominate, but the highly infectious alpha variant also maintains a moderate size niche. We did not observe significant differences in airborne transmission efficiency among the B.1.427, B.1.429 and ancestral B.1 (614G) variants in hamsters. These results demonstrate enhanced virulence and high relative fitness of the epsilon (B.1.427/B.1.429) variant in Syrian hamsters compared to an ancestral B.1 (614G) strain. Author SummaryIn the last 12 months new variants of SARS-CoV-2 have arisen in the UK, South Africa, Brazil, India, and California. New SARS-CoV-2 variants will continue to emerge for the foreseeable future in the human population and the potential for these new variants to produce severe disease and evade vaccines needs to be understood. In this study, we used the hamster model to determine the epsilon (B.1.427/429) SARS-CoV-2 strains that emerged in California in late 2020 cause more severe disease and infected hamsters have higher viral loads in the upper respiratory tract compared to the prior B.1 (614G) strain. These findings are consistent with human clinical data and help explain the emergence and rapid spread of this strain in early 2021.
Airborne transmission, a term combining both large droplet and aerosol transmission, is thought to be the main transmission route of SARS-CoV-2. Here we investigated the relative efficiency of aerosol transmission of two variants of SARS-CoV-2, B.1.1.7 (alpha) and lineage A, in the Syrian hamster. A novel transmission caging setup was designed and validated, which allowed the assessment of transmission efficiency at various distances. At 2 meters distance, only particles <5 {micro}m traversed between cages. In this setup, aerosol transmission was confirmed in 8 out of 8 (N = 4 for each variant) sentinels after 24 hours of exposure as demonstrated by respiratory shedding and seroconversion. Successful transmission occurred even when exposure time was limited to one hour, highlighting the efficiency of this transmission route. Interestingly, the B.1.1.7 variant outcompeted the lineage A variant in an airborne transmission chain after mixed infection of donors. Combined, this data indicates that the infectious dose of B.1.1.7 required for successful transmission may be lower than that of lineage A virus. The experimental proof for true aerosol transmission and the increase in the aerosol transmission potential of B.1.1.7 underscore the continuous need for assessment of novel variants and the development or preemptive transmission mitigation strategies.
Nipah virus (NiV) is a highly pathogenic and re-emerging virus which causes sporadic but severe infections in humans. Currently, no vaccines against NiV have been approved. We previously showed that ChAdOx1 NiV provides full protection against a lethal challenge with NiV Bangladesh (NiV-B) in hamsters. Here, we investigated the efficacy of ChAdOx1 NiV in the lethal African green monkeys (AGMs) NiV challenge model. AGMs were vaccinated either 4 weeks before challenge (prime vaccination), or 8 and 4 weeks before challenge with ChAdOx1 NiV (prime-boost vaccination). A robust humoral and cellular response was detected starting 14 days post initial vaccination. Upon challenge, control animals displayed a variety of signs and had to be euthanized between 5- and 7-days post inoculation. In contrast, vaccinated animals showed no signs of disease, and we were unable to detect infectious virus in all but one swab and all tissues. Importantly, no to limited antibodies against fusion protein or nucleoprotein IgG could be detected 42 days post challenge, suggesting that vaccination induced a very robust protective immune response preventing extensive virus replication. One Sentence SummaryA single vaccination with ChAdOx1 NiV protects African green monkeys against lethal disease induced by Nipah virus inoculation.
Many different vaccine candidates against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the etiological agent of COVID-19, are currently approved and under development. Vaccine platforms vary from mRNA vaccines to viral-vectored vaccines, and several candidates have been shown to produce humoral and cellular responses in small animal models, non-human primates and human volunteers. In this study, six non-human primates received a prime-boost intramuscular vaccination with 4 {micro}g of mRNA vaccine candidate CV07050101, which encodes a pre-fusion stabilized spike (S) protein of SARS-CoV-2. Boost vaccination was performed 28 days post prime vaccination. As a control, six animals were similarly injected with PBS. Humoral and cellular immune responses were investigated at time of vaccination, and two weeks afterwards. No antibodies could be detected two and four weeks after prime vaccination. Two weeks after boost vaccination, binding but no neutralizing antibodies were detected in 4 out of 6 non-human primates. SARS-CoV-2 S protein specific T cell responses were detected in these 4 animals. In conclusion, prime-boost vaccination with 4 {micro}g of vaccine candidate CV07050101 resulted in limited immune responses in 4 out of 6 non-human primates.