Biology subjects

Hanley, K. A.

Publications and source records attributed to Hanley, K. A..

14 recordsLinked to original sources

bioRxiv2026

Burning down the mouse: Effects of wildfire and post-fire reseeding on Sin Nombre virus prevalence in its reservoir host

Worldwide, physical habitats and biological communities are being reshaped by wildfire. Such changes have obvious potential to alter pathogen ecology, yet few studies, outside of those focused on ectoparasites, have tested the effects of wildfire on pathogen prevalence in wildlife. Even fewer have focused on the impacts of strategies for post-fire remediation on pathogen circulation. Here, we investigated the effect of wildfire and wildfire mitigation on the prevalence and viral load of Sin Nombre virus (SNV) infection in its reservoir host, the western deer mouse, using a study design of matched burned, unburned, and post-burn reseeded sites in northern New Mexico. In total, we screened 411 individual deer mice for SNV via RT-qPCR and analyzed the effect of wildfire and wildfire mitigation on relative mouse abundance, individual infection probability, site-level prevalence and viral load. Relative abundance was highest at reseeded sites, and model selection indicated that habitat structure, particularly the gradient from closed canopy to open-herbaceous habitat, was consistently associated with increased relative abundance. Similarly, SNV prevalence was significantly higher in reseeded sites than either burned or unburned sites but did not differ in burned versus unburned sites. Viral load did not differ between burn history types, and zero-inflated gamma hurdle models did not identify any strong predictors of viral load. Serendipitously, we were also able to investigate the impacts of an El Nino Southern Oscillation (ENSO) cycle on patterns of infection in a subsample of sites that were studied during and one year after an ENSO year and found that SNV prevalence increased significantly post-ENSO. Both reseeding and ENSO deliver resource pulses that can support increases in mouse density and thereby enhance SNV transmission. The impacts of post-fire management practices on SNV prevalence in its reservoir host that were revealed in this study should be considered when implementing such strategies and when utilizing treated areas.

ecology↗

bioRxiv2025

Inside-Out: Modeling the link between Zika virus viral dynamics within hosts and transmission to vectors across host species and virus strains

Epidemiological models of mosquito-borne virus transmission often lack accurate estimates of host-to-vector transmission probability. Here, we estimated this probability for two strains of Zika virus (ZIKV)--one sylvatic and one human-endemic--from two monkey species to Aedes albopictus mosquitoes using experimental infection data. Viral dynamics did not differ between monkey species, although one (cynomolgus macaque) is a native ZIKV host and the other (squirrel monkey) a novel host, but differed between strains, with viremia for the human-endemic strain peaking later and lower than the sylvatic strain. Only the sylvatic strain was transmitted to mosquitoes. In mosquitoes, anatomical barriers influence viral progression to salivary glands, complicating host infectiousness estimation. We quantified the probability of viral dissemination to the legs in Ae. albopictus, which increased with host viral load and was higher after feeding on squirrel monkeys than on cynomolgus macaques. We also found a positive relationship between virus titer in mosquito legs and virus detection in saliva after a 14-day extrinsic incubation period. Combining these factors, we found that squirrel monkeys were on average 1.5 times more infectious to Ae. albopictus than cynomolgus macaques. These estimates will help assess ZIKVs potential to establish an enzootic, sylvatic cycle in the Americas.

systems biology↗

bioRxiv2025

Human herpesvirus 1 associated with epizootics in Belo Horizonte, Minas Gerais, Brazil

Human activity in sylvatic environments and resulting contact with wildlife, such as non-human primates (NHP), can lead to pathogen spillover or spillback. Both NHPs and humans host a variety of herpesviruses. While these viruses typically cause asymptomatic infections in their natural hosts, they can lead to severe disease or even death when they move into novel hosts. In early 2024, deaths of Callithrix penicillata, the black-tufted marmoset, were reported in an urban park in Belo Horizonte, Minas Gerais, Brazil. The epizootic was investigated in collaboration with CETAS/IBAMA and the Zoonoses Department of Belo Horizonte. Nine marmoset carcasses, and 4 sick marmosets were found in the park; the latter exhibited severe neurological symptoms and systemic illness before succumbing within 48 hours. Carcasses were tested for rabies virus and were all negative, and necropsy findings revealed widespread organ damage. In addition, the samples were tested for yellow fever virus, with negative results. Finally, molecular testing, viral isolation and phylogenetic analysis demonstrated human herpesvirus 1 (HHV-1) as the causative agent. The likely source of infection was human-to-marmoset transmission, facilitated by close interactions such as feeding and handling. This study highlights the risks of pathogen spillover between humans and nonhuman primates, emphasizing the need for enhanced surveillance and public awareness to mitigate future epizootics.

microbiology↗

bioRxiv2024

Detection of neutralizing antibodies against arboviruses from liver homogenates

Yellow fever virus (YFV) circulates in a sylvatic cycle between non-human primates (NHPs) and arboreal mosquitoes in Brazil. Passive monitoring of ill or deceased NHPs is a key component of the Brazilian yellow fever (YF) surveillance program. Samples from NHPs carcasses are usually suitable for molecular tests but not for serological assays. As an alternative to the conventional plaque reduction neutralization test (PRNT) based on sera, we tested the utility of liver homogenates from experimentally infected (YFV, Mayaro virus [MAYV], chikungunya virus [CHIKV], or mock) mice to quantify PRNTs. Although homogenates from mock-infected mice showed a low level of nonspecific virus neutralization against YFV, MAYV or CHIKV, homogenates from YFV-, MAYV- and CHIKV-infected mice demonstrated significantly higher levels of virus neutralization compared to controls. Receiver operating characteristic (ROC) curves analyses were performed using the median neutralization values of three technical replicates for each infected group separately or collectively. Results showed scores [≥]0.97 (95% CI [≥] 0.89-1.0) for the area under the curve at dilutions 1:20 to 1:80, suggesting that median virus neutralization values effectively differentiated YFV-, MAYV-, or CHIKV-infected groups from controls. Liver homogenates obtained from 25 NHPs carcasses (collected during the 2017 YF outbreak in Brazil) were also tested using the adapted PRNT as well as rapid anti-YFV IgM immunochromatographic tests. Neutralization activity was detected in six NHPs samples that were also positive by PCR and anti-YFV IgM tests and one sample that tested negative by PCR and IgM test. Our results demonstrate the feasibility of using liver homogenates as an alternative approach for serological investigation in viral epidemiologic surveillance.

microbiology↗

bioRxiv2024

Forest edge landscape context affects mosquito community composition and risk of pathogen emergence

Forest edges, where humans, mosquitoes, and wildlife interact, may serve as a nexus for zoonotic arbovirus exchange. Although often treated as uniform interfaces, the landscape context of edge habitats can greatly impact ecological interactions. Here, we investigated how the landscape context of forest edges shapes mosquito community structure in an Amazon rainforest reserve near the city of Manaus, Brazil, using hand-nets to sample mosquitoes at three distinct forest edge types. Sampling sites were situated at edges bordering urban land cover, rural land cover, and natural treefall gaps, while sites in continuous forest served as controls. Community composition differed substantially among edge types, with rural edges supporting the highest species diversity. Rural edges also provided suitable habitat for forest specialists, including key sylvatic vectors, of which Haemagogus janthinomys was the most abundant species sampled overall. Our findings emphasize the importance of landscape context in assessing pathogen emergence risk at forest edges.

ecology↗

bioRxiv2024

Aedes albopictus is not an arbovirus aficionado - Impacts of sylvatic flavivirus infection in vectors and hosts on mosquito engorgement on non-human primates

The contact structure between vertebrate hosts and arthropod vectors plays a key role in the spread of arthropod-borne viruses (arboviruses); thus, it is important to determine whether arbovirus infection of either host or vector alters vector feeding behavior. Here we leveraged a study of the replication dynamics of two arboviruses isolated from their ancestral cycles in paleotropical forests, sylvatic dengue-2 (DENV-2) and Zika (ZIKV), in one non-human primate (NHP) species from the paleotropics (cynomolgus macaques, Macaca fascicularis) and one from the neotropics (squirrel monkeys, Saimiri boliviensis) to test the effect of both vector and host infection with each virus on completion of blood feeding (engorgement) of the mosquito Aedes albopictus. Although mosquitoes were starved and given no choice of hosts, engorgement rates varied dramatically, from 0% to 100%. While neither vector nor host infection systematically affected engorgement, NHP species and body temperature at the time of feeding did. We also interrogated the effect of repeated mosquito bites on cytokine expression and found that epidermal growth factor (EGF) and macrophage migration inhibitory factor (MIF) concentrations were dynamically associated with exposure to mosquito bites. This study highlights the importance of incorporating individual-level heterogeneity of vector biting in arbovirus transmission models.

systems biology↗

bioRxiv2023

Immunologically mediated trade-offs shaping transmission of sylvatic dengue and Zika viruses in native and novel non-human primate hosts

Mosquito-borne dengue (DENV) and Zika (ZIKV) viruses originated in Old World sylvatic cycles involving monkey hosts, spilled over into human transmission, and were translocated to the Americas, creating potential for spillback into neotropical sylvatic cycles. Studies of the trade-offs that shape within-host dynamics and transmission of these viruses are lacking, hampering efforts to predict spillover and spillback. We exposed native (cynomolgus macaque) or novel (squirrel monkey) hosts to mosquitoes infected with either sylvatic DENV or ZIKV and monitored viremia, natural killer cells, transmission to mosquitoes, cytokines, and neutralizing antibody titers. Unexpectedly, DENV transmission from both host species occurred only when serum viremia was undetectable or near the limit of detection. ZIKV replicated in squirrel monkeys to much higher titers than DENV and was transmitted more efficiently but stimulated lower neutralizing antibody titers. Increasing ZIKV viremia led to greater instantaneous transmission and shorter duration of infection, consistent with a replication-clearance trade-off.

microbiology↗

bioRxiv2022

Ecological drivers of sustained enzootic yellow fever virus transmission in Brazil, 2017-2021

Beginning December 2016, sylvatic yellow fever (YF) outbreaks spread into southeastern Brazil, and Minas Gerais state experienced two sylvatic YF waves (2017 and 2018). Following these massive YF waves, we screened 187 free-living non-human primate (NHPs) carcasses collected throughout the state between January 2019 and June 2021 for YF virus (YFV) using qPCR. One sample belonging to a Callithrix, collected in June 2020, was positive for YFV. The viral strain belonged to the same lineage associated with 2017-2018 outbreaks, showing the continued enzootic circulation of YFV in the state. Next, using data from 781 NHPs carcasses collected in 2017-18, we used generalized additive mixed models (GAMMs) to identify the spatiotemporal and host-level drivers of YFV infection and intensity (an estimation of genomic viral load in the liver of infected NHP). Our GAMMs explained 65% and 68% of variation in virus infection and intensity, respectively, and uncovered strong temporal and spatial patterns for YFV infection and intensity. NHP infection was higher in the eastern part of Minas Gerais state, where 2017-2018 outbreaks affecting humans and NHPs were concentrated. The odds of YFV infection were significantly lower in NHPs from urban areas than from urban-rural or rural areas, while infection intensity was significantly lower in NHPs from urban areas or the urban-rural interface relative to rural areas. Both YFV infection and intensity were higher during the warm/rainy season compared to the cold/dry season. The higher YFV intensity in NHPs in warm/rainy periods could be a result of higher exposure to vectors and/or higher virus titers in vectors during this time resulting in the delivery of a higher virus dose and higher viral replication levels within NHPs. Further studies are needed to better test this hypothesis and further compare the dynamics of YFV enzootic cycles between different seasons. Author SummaryIn 2017 and 2018 massive sylvatic yellow fever (YF) outbreaks took place in Minas Gerais Brazil. To investigate yellow fever virus (YFV) circulation following these massive outbreaks, we investigated samples from 187 free-living non-human primate (NHPs) collected between January 2019 and June 2021. One sample belonging to a Callithrix, collected in June 2020 was positive for YFV. This virus was closely related to YFV from previous outbreaks (2017-2018) showing the continued enzootic circulation of YFV in the state. Next, we investigated the drivers of YFV infection and intensity (an estimation of viral load in each infected NHP) during the 2017-18 outbreaks. The odds of YFV infection in NHPs were lower in urban areas compared to rural ones as expected in sylvatic cycles. There were strong temporal and spatial patterns were observed for YFV infection and intensity, especially in the eastern part of Minas Gerais state. The higher YFV infection and intensity observed during the warm/rainy season (as opposed to the cold/dry one) could be related to higher exposure to vectors and/or higher virus titers in vectors during this time. The possible delivery of a higher virus dose in NHPs could lead to higher viral replication levels within NHPs explaining the higher intensity of infection during warm/rainy season. Further studies are needed to better test this hypothesis and further compare the dynamics of YFV enzootic cycles between different seasons.

microbiology↗

bioRxiv2020

Evolution of resistance to fluoroquinolones by dengue virus serotype 4 provides insight into mechanism of action and consequences for viral fitness

Drugs against flaviviruses such as dengue (DENV) and Zika (ZIKV) virus are urgently needed. We previously demonstrated that three fluoroquinolones, ciprofloxacin, enoxacin, and difloxacin, suppress replication of six flaviviruses. To investigate the barrier to resistance and mechanism(s) of action of these drugs, DENV-4 was passaged in triplicate in HEK-293 cells in the presence or absence of each drug. Resistance to ciprofloxacin was detected by the seventh passage and to difloxacin by the tenth, whereas resistance to enoxacin did not occur within ten passages. Two putative resistance-conferring mutations were detected in the envelope gene of ciprofloxacin and difloxacin-resistant DENV-4. In the absence of ciprofloxacin, ciprofloxacin-resistant viruses sustained a significantly higher viral titer than control viruses in HEK-293 and HuH-7 cells and resistant viruses were more stable than control viruses at 37{degrees}C. These results suggest that the mechanism of action of ciprofloxacin and difloxacin involves interference with virus binding or entry.

evolutionary biology↗

bioRxiv2020

Ecological processes underlying the emergence of novel enzootic cycles--arboviruses in the neotropics as a case study

Pathogens originating from wildlife (zoonoses) pose a significant public health burden, comprising the majority of emerging infectious diseases. Efforts to control and prevent zoonotic disease have traditionally focused on animal-to-human transmission, or "spillover". However, in the modern era, increasing international mobility and commerce facilitate the spread of infected humans, non-human animals (hereafter animals), and their products worldwide, thereby increasing the risk that zoonoses will be introduced to new geographic areas. Imported zoonoses can potentially spill back to infect local wildlife--a danger magnified by urbanization and other anthropogenic pressures that increase contacts between human and wildlife populations. In this way, humans can function as vectors, dispersing zoonoses from their ancestral enzootic systems to establish reservoirs elsewhere in novel animal host populations. Once established, these enzootic cycles are largely unassailable by standard control measures and have the potential to feed human epidemics. Understanding when and why translocated zoonoses establish novel enzootic cycles requires disentangling ecologically complex and stochastic interactions between the zoonosis, the human population, and the natural ecosystem. We address this challenge by delineating potential ecological mechanisms affecting each stage of enzootic establishment--wildlife exposure, enzootic infection, and persistence--applying existing ecological concepts from epidemiology, invasion biology, and population ecology. We ground our study in the neotropics, where four arthropod-borne viruses (arboviruses) of zoonotic origin--yellow fever, dengue, chikungunya, and Zika viruses--have separately been introduced into the human population. This paper is a step towards developing a framework for predicting and preventing novel enzootic cycles in the face of zoonotic translocations.

ecology↗

bioRxiv2020

Old drugs with new tricks: Efficacy of fluoroquinolones to suppress replication of flaviviruses

Antiviral therapies are urgently needed to treat infections with flaviviruses such as Zika (ZIKV) and dengue (DENV) virus. Repurposing FDA-approved compounds could provide the fastest route to alleviate the burden of flaviviral diseases. In this study, three fluoroquinolones, enoxacin, difloxacin and ciprofloxacin, curtailed replication of flaviviruses ZIKV, DENV, Langat (LGTV) and Modoc (MODV) in HEK-293 cells at low micromolar concentrations. Time-of-addition assays revealed that enoxacin suppressed ZIKV replication when added at 6 hours post-infection, suggesting inhibition of an intermediate step in the virus life cycle, whereas ciprofloxacin and difloxacin had a wider window of efficacy of 2, 6, and 8 hours post-infection for difloxacin and 2 to 8 hours post-infection for ciprofloxacin. The efficacy of enoxacin to suppress ZIKV replication in 5-week-old A129 mice was evaluated in two experiments. First, mice were infected with 1x105 plaque-forming units (pfu) ZIKV FSS13025 (n=20) or PBS (n=11) on day 0 and subsets were treated with enoxacin at 10mg/kg or 15mg/kg or diluent orally twice daily on days 1-5. Treated and control mice did not differ in weight change or virus titer in serum or brain. Mice treated with enoxacin showed a significant, 5-fold decrease in ZIKV titer in testes relative to controls. Second, mice were infected with 1x102 pfu ZIKV (n=13) or PBS (n=13) on day 0 and subsets were treated with 15mg/kg oral enoxacin or diluent twice daily on days 0 (pre-treatment) and 1-5. Mice treated with enoxacin showed a significant, 2.5-fold decrease in ZIKV titer in testes relative to controls, while weight and viral load in the serum, brain, and liver did not differ between treated and control mice. Enoxacin efficacy in cultured murine Sertoli cells was not enhanced compared to efficacy in HEK-293 cells. ZIKV can be sexually transmitted, so reduction of titer in the testes by enoxacin should be further investigated. Author SummaryFlaviviruses such as Zika and dengue virus pose a significant threat to public health worldwide, and there are currently no antiviral therapies to treat any flaviviral infection. Repurposing FDA-approved drugs as anti-flaviviral therapies can accelerate clinical use. We demonstrated that fluoroquinolone antibiotics exhibit anti-flaviviral efficacy, suppressing flavivirus replication in cultured human cells. Additionally, we found that the fluoroquinolone enoxacin suppressed Zika virus replication in mouse testes. While Zika virus is primarily transmitted via mosquitoes, the virus also undergoes sexual transmission. The importance of sexual transmission for the overall epidemiology of the virus remains unclear; nonetheless all routes of potential transmission to pregnant women are of concern as fetal infection in utero can have devastating effects. Thus, our data indicate that fluoroquinolones hold promise for treatment of flaviviral infections, particularly infection of the testes by Zika virus, and that this class of drugs warrants further study.

microbiology↗

bioRxiv2019

Programmable CRISPR interference for gene silencing using Cas13a in mosquitoes

In the CRISPR-Cas systems, Cas13a is an RNA-guided RNA nuclease specifically targeting single strand RNA. We developed a Cas13a mediated CRISPR interference tool to target mRNA for gene silencing in mosquitoes. The machinery was tested in two mosquito species. A Cas13a expressing plasmid was delivered to mosquitoes by intrathoracic injection, and Cas13a transcripts were detectable at least10 days post-delivery. In Anopheles gambiae, vitellogenin gene was silenced by Vg-crRNA injection two hours post-blood meal, which was accompanied by a significant reduction in egg production. In Aedes aegypti, the - and {delta}-subunits of COPI genes were silenced by a post-blood meal crRNA injection, which resulted in mortality and fragile midguts, reproducing a phenotype reported previously. Co-silencing genes simultaneously is achievable when a cocktail of target crRNAs is given. No detectable collateral cleavages of non-target transcripts were observed in the study. This study adds a programmable CRISPR tool to manipulate RNA in mosquitoes.

molecular biology↗

bioRxiv2018

Wolbachia pipientis occurs in Aedes aegypti populations in New Mexico and Florida, USA

The mosquitoes Aedes aegypti (L.) and Ae. albopictus Skuse are the major vectors of dengue, Zika, yellow fever and chikungunya viruses worldwide. Wolbachia, an endosymbiotic bacterium present in many insects, is being utilized in novel vector control strategies to manipulate mosquito life history and vector competence to curb virus transmission. Earlier studies have found that Wolbachia is commonly detected in Ae. albopictus but sporadically detected in Ae. aegypti. In this study, we used a two-step PCR assay to detect Wolbachia in wild-collected samples of Ae. aegypti. The PCR products were sequenced to validate amplicons and identify Wolbachia strains. A Loop-mediated isothermal amplification (LAMP) assay was developed and used for detecting Wolbachia in selected mosquito specimens as well. We found Wolbachia in 85/148 (57.4%) wild specimens of Ae. aegypti from various cities in New Mexico and in 2/46 (4.3%) wild specimens of Ae. aegypti from St. Augustine, Florida. We did not detect Wolbachia in 94 samples of Ae. aegypti from Deer Park, Harris County, Texas. Wolbachia detected in Ae. aegypti from both New Mexico and Florida was the wAlbB strain of Wolbachia pipientis. A Wolbachia positive colony of Ae. aegypti was established from pupae collected in Las Cruces, New Mexico in 2018.

ecology↗

bioRxiv2018

Schlafen 11 Restricts Flavivirus Replication

Schlafen 11 (Slfn11) is a ubiquitously expressed interferon stimulating gene (ISG) that controls synthesis of proteins by regulating tRNA abundance. Likely through this mechanism, Slfn11 has previously been shown to impair human immunodeficiency virus 1 (HIV-1) infection and the expression of codon-biased open reading frames. Because replication of positive-sense single-stranded RNA [(+)ssRNA viruses] requires the immediate translation of the incoming viral genome whereas negative sense, single stranded [(-)ssRNA] viruses carry at infection an RNA replicase that makes multiple translation competent copies of the incoming viral genome, we reasoned that (+)ssRNA viruses will be more sensitive to the effect of Slfn11 on protein synthesis than (-)ssRNA viruses. To evaluate this hypothesis, we tested the effects of Slfn11 on the replication of a panel of ssRNA viruses in the human glioblastoma cell line A172, which naturally expresses Slfn11. Depletion of Slfn11 in this cell line significantly increased the replication of (+)ssRNA viruses from the Flavivirus family, including West Nile (WNV), dengue (DENV), and Zika virus (ZIKV) but had no significant effect on the replication of the (-)ssRNA viruses vesicular stomatitis (VSV, Rhabdoviridae family) and Rift Valley fever (RVFV, Phenuiviridae family). Despite that WNV titers in Slfn11-deficient cells were almost 100-fold higher than in cells expressing this protein; they produced approximately two-fold less viral particles, as determined by PCR-based quantification of virion-associated WNV RNA in the cell culture supernatant. These data indicated that Slfn11 impairs WNV fitness but does not affect other steps of the viral life cycle including entry, viral RNA replication and translation, and budding. Similarly to the proposed anti-HIV-1 mechanism of Slfn11, this protein prevented WNV-induced down-regulation of a subset of tRNAs implicated in the translation of 19% of the viral polyprotein. Importantly, we provided evidence suggesting that the broad anti-viral activity of Slfn11 requires other cellular proteins, since overexpression of Slfn11 in cells that naturally lack the expression of this protein, did not impair WNV or HIV-1 infection. In summary, this study demonstrates that Slfn11 restricts flaviviruses replication by impairing viral fitness.\n\nAUTHOR SUMMARYThe host targets mechanisms that viruses have evolved to optimize replication. We provide evidence that the cellular protein Schlafen 11 (Slf11) impairs replication of flaviviruses, including West Nile (WNV), dengue (DENV), and Zika virus (ZIKV). However, replication of single-stranded, negative RNA viruses was not affected. Specifically, Slf11 decreases the fitness of WNV potentially by preventing virus-induced modifications of the host tRNA repertoire that could lead to enhanced viral protein folding. Furthermore, we demonstrated that Slf11 is not the limiting factor of this novel broad anti-viral pathway.

microbiology↗