Biology subjects

Lazear, H. M.

Publications and source records attributed to Lazear, H. M..

13 recordsLinked to original sources

bioRxiv2026

The La Crosse virus M segment determines virus isolate cell-to-cell spread and virulence

La Crosse virus (LACV) is an orthobunyavirus spread by mosquitoes in North America and can cause severe neurological disease. Despite this burden, there is a lack of LACV antiviral treatments as our fundamental understanding of how LACV spreads and causes disease remains incomplete. To investigate LACV biology, we took advantage of two genetically similar LACV lineage I isolates (LACV1960 and LACV1978) where we found that LACV1960 infects and replicates at a higher rate than LACV1978, while LACV1978 exhibits enhanced cell-cell spread and in vivo virulence and dissemination. To investigate the genomic determinants behind these phenotypes, we generated reassortants between each isolate. We found that each genomic segment contributed to LACV pathogenesis with the M segment as a dominant determinant for LACV pathogenesis in vivo and plaque size and replication in vitro. To address which M segment protein contributes to plaque size and infectivity, we generated M segment chimeric viruses using a LACV1978 background and swapping in regions of the LACV1960 M segment. We found that the Gc head domain determined plaque size and infectivity, with the LACV1960 Gc head chimera producing small plaques but having increased infectivity over the wild-type LACV1978. Finally, using natural LACV lineage isolates, we showed that plaque size is variable across and within lineages suggesting changes in the M segment may impact LACV in nature. In future studies, we will continue to investigate the mechanisms behind how cell-to-cell spread influences dissemination to better understand how LACV genome segments affect spread, infectivity, virulence, and viral fitness.

microbiology↗

bioRxiv2026

No-known-vector flaviviruses exhibit diverse replication and virulence phenotypes in mice

The Orthoflavivirus genus (flaviviruses) includes globally significant arboviruses, which cycle between arthropod vectors (mosquitoes and ticks) and vertebrate hosts. In contrast, no-known-vector flaviviruses (NKVFVs) have been isolated from rodents and bats, but not arthropods, so are thought to spread by vector-independent routes. However, little is known about the host range and pathogenic mechanisms of these viruses. To evaluate NKVFV pathogenesis, we infected wild-type, Ifnar1-/-, and Ifnar1-/- Ifngr1-/- mice by footpad inoculation with 12 NKVFVs: Entebbe bat virus (ENTV), Sokuluk virus (SOKV), Yokose virus (YOKV), Modoc virus (MODV), Apoi virus (APOIV), Jutiapa virus (JUTV), Sal Vieja virus (SVV), Dakar bat virus (DBV), Rio Bravo virus (RBV), Montana myotis leukoencephalitis virus (MMLV), Phnom Penh bat virus (PPBV), and Tamana bat virus (TABV). We compared these NKVFVs to the mosquito-borne Zika virus and Kedougou virus and to the tick-borne Langat virus and Kadam virus. We monitored disease signs and measured viremia. 7 NKVFVs (ENTV, SOKV, YOKV, MODV, APOIV, DBV, RBV) were virulent in Ifnar1-/- mice, causing 100% lethality within 9 dpi, accompanied by viremia. All viruses tested were virulent in Ifnar1-/- Ifngr1-/- mice and produced greater viremia compared to Ifnar1-/- mice. No viremia or disease signs were detected in wild-type mice. We further evaluated RBV, MMLV, and PPBV replication in mouse primary fibroblasts and bone marrow-derived macrophages, as well as in cell lines from three bat species. Altogether, our results provide new information about the virulence and replication phenotypes of NKVFVs, supporting future studies investigating NKVFV-specific and pan-flavivirus pathogenic mechanisms. IMPORTANCEFlaviviruses that cause human disease are transmitted by mosquitoes and ticks (e.g. West Nile virus, yellow fever virus, tick-borne encephalitis virus). But there are related flaviviruses that are not known to infect arthropods, so are thought to spread by vector-independent routes (no-known-vector flaviviruses, NKVFVs). Not much is known about NKVFVs, but they provide an opportunity to understand flavivirus replication, tropism, and pathogenesis more broadly. We evaluated a panel of 12 NKVFVs for their ability to cause disease in mice with and without antiviral interferon responses as well as their replication in mouse cells. Our findings provide new information about these under-studied viruses and demonstrate which mouse models may be appropriate to use for further studies with NKVFVs.

microbiology↗

bioRxiv2026

Interferon lambda signaling to maternal dendritic cells protects against congenital Zika virus infection

Interferon lambda (IFN-{lambda}, type III IFN) mediates antiviral immunity at anatomic barriers, including the maternal-fetal interface. To investigate the effects of IFN-{lambda} during congenital Zika virus (ZIKV) infection, we infected mice lacking the IFN-{beta} receptor (Ifnar1-/-) or both the IFN-{beta} and IFN-{lambda} receptors (Ifnar1-/-Ifnlr1-/-) at E9 and found that loss of maternal IFN-{lambda} signaling resulted in greater transplacental transmission. We used HiPlex RNAscope on entire gravid uteruses and found that IFN-{lambda} was expressed more proximal to the site of ZIKV infection in Ifnar1-/- dams compared to Ifnar1-/-Ifnlr1-/- dams. We performed immunophenotyping of the placenta and uterus by flow cytometry and found a decrease in dendritic cells and NK cells in the uterus of Ifnar1-/-Ifnlr1-/- dams compared to Ifnar1-/- dams, but NK cell depletion did not impact fetal infection. Using conditional knockout mice, we identified maternal dendritic cells as the key IFN-{lambda} responsive cell type mediating protection against ZIKV congenital infection.

immunology↗

bioRxiv2023

A fur plucking model to study herpes simplex virus reactivation and recurrent disease

Herpes simplex viruses (HSV-1 and HSV-2) most commonly cause ulcerative epithelial lesions (cold sores, genital herpes). Importantly, HSV establishes life-long persistent (latent) infection in sensory neurons. Reactivation from latency produces recurrent epithelial lesions, which constitute the greatest burden of HSV disease in people. The mechanisms that regulate latency and reactivation remain poorly understood, in part due to limitations in the animal models available for studying HSV reactivation. We have developed a simple and tractable model to induce HSV-1 and HSV-2 reactivation from latently infected sensory ganglia. We infected C57BL/6 mice with 1 x 106 FFU of HSV-1 (strain NS) or 500 FFU of HSV-2 (strain 333) on flank skin depilated by manual plucking. 35 days post-infection (dpi) we re-plucked the fur from the infected flank and observed recurrent lesions in the same dermatome as the primary infection. We detected HSV DNA in dermatome skin through 4 days post-re-plucking. We found that shaving the ipsilateral flank or plucking the contralateral flank did not induce recurrent skin lesions, suggesting that fur plucking is a specific stimulus that induces HSV reactivation. Further, we were able to induce multiple rounds of plucking induced recurrent disease, providing a model to investigate the lifelong nature of HSV infection. This new model provides a tractable system for studying pathogenic mechanisms of and therapeutic interventions against HSV reactivation and recurrent disease.

microbiology↗

bioRxiv2023

Interferon lambda restricts herpes simplex virus skin disease by suppressing neutrophil-mediated pathology

Type III interferons (IFN-{lambda}) are antiviral and immunomodulatory cytokines that have been best characterized in respiratory and gastrointestinal infections, but the effects of IFN-{lambda} against skin infections have not been extensively investigated. We sought to define the skin-specific effects of IFN-{lambda} against the highly prevalent human pathogen herpes simplex virus (HSV). We infected mice lacking the IFN-{lambda} receptor (Ifnlr1-/-), both the IFN-{lambda} and the IFN-{beta} receptor (Ifnar1-/- Ifnlr1-/-), or IFN-{lambda} cytokines (Ifnl2/3-/-) and found that IFN-{lambda} restricts the severity of HSV-1 and HSV-2 skin lesions, independent of a direct effect on viral load. Using conditional knockout mice, we found that IFN-{lambda} signaling in both keratinocytes and neutrophils was necessary to control HSV-1 skin lesion severity, and that IFN-{lambda} signaling in keratinocytes suppressed CXCL9-mediated neutrophil recruitment to the skin. Furthermore, depleting neutrophils or blocking CXCL9 protected against severe HSV-1 skin lesions in Ifnlr1-/- mice. Altogether, our results suggest that IFN-{lambda} plays an immunomodulatory role in the skin that restricts neutrophil-mediated pathology during HSV infection, and suggest potential applications for IFN-{lambda} in treating viral skin infections. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=137 SRC="FIGDIR/small/557277v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@110a7feorg.highwire.dtl.DTLVardef@853e46org.highwire.dtl.DTLVardef@1bb744aorg.highwire.dtl.DTLVardef@1cfdf94_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2022

Neuroinvasive flavivirus pathogenesis is restricted by host genetic factors in Collaborative Cross mice, independently of Oas1b

Powassan virus (POWV) is an emerging tick-borne flavivirus that causes neuroinvasive disease, including encephalitis, meningitis, and paralysis. Similar to other neuroinvasive flaviviruses, such as West Nile virus (WNV) and Japanese encephalitis virus (JEV), POWV disease presentation is heterogeneous, and the factors influencing disease outcome are not fully understood. We used Collaborative Cross (CC) mice to assess the impact of host genetic factors on POWV pathogenesis. We infected a panel of Oas1b-null CC lines with POWV and observed a range of susceptibility phenotypes, indicating that host factors other than the well-characterized flavivirus restriction factor Oas1b modulate POWV pathogenesis in CC mice. Among Oas1b-null CC lines, we identified multiple highly susceptible lines (0% survival), including CC071, and a single resistant line (78% survival), CC045. Susceptibility phenotypes generally were concordant among neuroinvasive flaviviruses, although we identified one line, CC006, that was resistant specifically to JEV, suggesting that both pan-flavivirus and virus-specific mechanisms contribute to susceptibility phenotypes in CC mice. We found that POWV replicated to higher titers in bone marrow-derived macrophages from CC071 mice compared to CC045 mice, suggesting that resistance could result from cell-intrinsic restriction of viral replication. Although serum viral loads at 2 days post-infection were equivalent between CC071 and CC045 mice, clearance of POWV from the serum was significantly slower in CC071 mice. Furthermore, CC045 mice had significantly lower viral loads in the brain at 7 days post-infection compared to CC071 mice, suggesting that reduced CNS infection contributes to the resistant phenotype of CC045 mice. IMPORTANCENeuroinvasive flaviviruses, such as WNV, JEV, and POWV, are transmitted to humans by mosquitoes or ticks, can cause neurologic disease, such as encephalitis, meningitis, and paralysis, and can result in death or long-term sequelae. Although potentially severe, neuroinvasive disease is a rare outcome of flavivirus infection. The factors that determine whether someone develops severe disease after flavivirus infection are not fully understood, but host genetic differences in polymorphic antiviral response genes likely contribute to disease outcome. We evaluated a panel of genetically diverse mice and identified lines with distinct outcomes following infection with POWV. We found that resistance to POWV pathogenesis corresponded to reduced viral replication in macrophages, more rapid clearance of virus in peripheral tissues, and reduced viral infection in the brain. These susceptible and resistant mouse lines will provide a system for investigating the pathogenic mechanisms of POWV and identifying polymorphic host genes that contribute to resistance.

microbiology↗

bioRxiv2022

Zika virus replicates in the vagina of mice with intact interferon signaling

Zika virus (ZIKV) is unusual among flaviviruses in its ability to spread between humans through sexual contact, as well as by mosquitoes. Sexual transmission has the potential to change the epidemiology and geographic range of ZIKV compared to mosquito-borne transmission and potentially could produce distinct clinical manifestations, so it is important to understand the host mechanisms that control susceptibility to sexually transmitted ZIKV. ZIKV replicates poorly in wild-type mice following subcutaneous inoculation, so most ZIKV pathogenesis studies use mice lacking IFN-{beta} signaling (e.g. Ifnar1-/-). However, we found that wild-type mice support ZIKV replication following intravaginal infection, although the infection remained localized to the lower female reproductive tract. Vaginal replication was not a unique property of ZIKV, as other flaviviruses that generally are restricted in wild-type mice also were able to replicate in the vagina. Vaginal ZIKV infection required a high-progesterone state (pregnancy or pre-treatment with depot medroxyprogesterone acetate (DMPA)), identifying a key role for hormonal status in susceptibility to vaginal infection. Progesterone-mediated susceptibility did not appear to result from a compromised epithelial barrier, blunted antiviral gene induction, or changes in vaginal leukocyte populations, leaving open the mechanism by which progesterone confers susceptibility to vaginal ZIKV infection. Progesterone treatment is a key component of mouse vaginal infection models for herpes simplex virus and Chlamydia, but the mechanisms by which DMPA increases susceptibility to those pathogens also remain poorly defined. Understanding how progesterone mediates susceptibility to ZIKV vaginal infection may provide insights into host mechanisms influencing susceptibility to diverse sexually transmitted pathogens. IMPORTANCEZika virus (ZIKV) is transmitted by mosquitoes, similarly to other flaviviruses. However, ZIKV is unusual in its ability also to spread through sexual transmission. We found that ZIKV was able to replicate in the vaginas of wild-type mice, even though these mice do not support ZIKV replication by other routes, suggesting that the vagina is particularly susceptible to ZIKV infection. Vaginal susceptibility was dependent on a high progesterone state, which is a common feature of mouse vaginal infection models for other pathogens, through mechanisms that have remained poorly defined. Understanding how progesterone mediates susceptibility to ZIKV vaginal infection may provide insights into host mechanisms that influence susceptibility to diverse sexually transmitted pathogens.

microbiology↗

bioRxiv2022

Interferon lambda signals in maternal tissues to exert protective and pathologic effects in a gestational-stage dependent manner

Interferon lambda (IFN-{lambda}, type III IFN) is constitutively secreted from human placental cells in culture and reduces Zika virus (ZIKV) transplacental transmission in mice. However, the roles of IFN-{lambda} during healthy pregnancy and in restricting congenital infection remain unclear. Here we used mice lacking the IFN-{lambda} receptor (Ifnlr1-/-) to generate pregnancies lacking either maternal or fetal IFN-{lambda} responsiveness and found that the antiviral effect of IFN-{lambda} resulted from signaling exclusively in maternal tissues. This protective effect depended on gestational stage, as infection earlier in pregnancy (E7 rather than E9) resulted in enhanced transplacental transmission of ZIKV. In Ifnar1-/- dams, which sustain robust ZIKV infection, maternal IFN-{lambda} signaling caused fetal resorption and intrauterine growth restriction. Pregnancy pathology elicited by poly(I:C) treatment also was mediated by maternal IFN-{lambda} signaling, specifically in maternal leukocytes, and also occurred in a gestational stage-dependent manner. These findings identify an unexpected effect of IFN-{lambda} signaling specifically in maternal (rather than placental or fetal) tissues, which is distinct from the pathogenic effects of IFN-{beta} (type I IFN) during pregnancy. These results highlight the complexity of immune signaling at the maternal-fetal interface, where disparate outcomes can result from signaling at different gestational stages. IMPORTANCEPregnancy is an immunologically complex situation, which must balance protecting the fetus from maternal pathogens with preventing maternal immune rejection of non-self fetal and placental tissue. Cytokines, such as interferon lambda (IFN-{lambda}), contribute to antiviral immunity at the maternal-fetal interface. We found in a mouse model of congenital Zika virus infection that IFN-{lambda} can have either a protective antiviral effect or cause immune-mediated pathology, depending on the stage of gestation when IFN-{lambda} signaling occurs. Remarkably, both the protective and pathologic effects of IFN-{lambda} occurred through signaling exclusively in maternal immune cells, rather than in fetal or placental tissues, or in other maternal cell types, identifying a new role for IFN-{lambda} at the maternal-fetal interface.

immunology↗

bioRxiv2021

Zika virus-specific IgM elicited during pregnancy exhibits ultrapotent neutralization

Congenital Zika virus (ZIKV) infection results in neurodevelopmental deficits in up to 14% of infants born to ZIKV-infected mothers. Neutralizing antibodies are a critical component of protective immunity. Here, we demonstrate that plasma IgM responses contribute to ZIKV immunity in pregnancy, mediating neutralization up to three months post symptoms. From a ZIKV-infected pregnant woman, we established a B cell line secreting a pentameric ZIKV-specific IgM (DH1017.IgM) that exhibited ultrapotent ZIKV neutralization dependent on the IgM isotype. DH1017.IgM targets a novel envelope dimer epitope within Domain II. The arrangement of this epitope on the virion is compatible with concurrent engagement of all ten antigen-binding sites of DH1017.IgM, a solution not achievable by IgG antibodies. DH1017.IgM protected against lethal ZIKV challenge in mice. Our findings identify a unique role of antibodies of the IgM isotype in protection against ZIKV and posit DH1017.IgM as a safe and effective candidate immunoprophylactic, particularly during pregnancy. Key pointsO_LIPlasma IgM contributes to early ZIKV neutralization during pregnancy C_LIO_LIUltrapotent neutralization by pentameric DH1017.IgM mAb depends on isotype C_LIO_LIDH1017.IgM can engage all binding sites concurrently through different angles of approach C_LIO_LIDH1017.IgM protects mice against lethal ZIKV challenge C_LI

immunology↗

bioRxiv2021

Structurally conserved domains between flavivirus and alphavirus fusion glycoproteins contribute to replication in mammals and infectious virion production.

Alphaviruses and flaviviruses have class II fusion glycoproteins that are essential for virion assembly and infectivity. Importantly, the tip of domain II is structurally conserved between the alphavirus and flavivirus fusion proteins, yet whether these structural similarities between virus families translate to functional similarities is unclear. Using in vivo evolution of Zika virus (ZIKV), we identified several novel emerging variants including an envelope glycoprotein variant in {beta}-strand c (V114M) of domain II. We have previously shown that the analogous {beta}-strand c and the ij loop, located in the tip of domain II of the alphavirus E1 glycoprotein, are important for infectivity. This led us to hypothesize that flavivirus E {beta}-strand c also contributes to flavivirus infection. We generated this ZIKV glycoprotein variant and found that while it had little impact on infection in mosquitoes, it reduced replication in human cells and mice, and increased virus sensitivity to ammonium chloride, as seen for alphaviruses. In light of these results and given our alphavirus ij loop studies, we mutated a conserved alanine at the tip of the flavivirus ij loop to valine to test its effect on ZIKV infectivity. Interestingly, this mutation inhibited infectious virion production of ZIKV and yellow fever virus, but not West Nile virus. Together, these studies show that structurally analogous residues in the alphavirus and flavivirus class II fusion proteins contribute to virus infection in vivo and highlight these shared domains as targets for broad-spectrum arbovirus therapies. Author SummaryArboviruses are a significant global public health threat, yet there are no antivirals targeting these viruses. This problem is in part due to our lack of knowledge on the molecular mechanisms involved in the arbovirus life cycle. In particular, virus entry and assembly are essential processes in the virus life cycle and steps that can be targeted for the development of antiviral therapies. Therefore, understanding common, fundamental mechanisms used by different arboviruses for entry and assembly is essential. In this study, we show that flavivirus and alphavirus residues located in structurally conserved and analogous regions of the class II fusion proteins contribute to common mechanisms of entry, dissemination, and infectious virion production. These studies highlight how class II fusion proteins function and provide novel targets for development of antivirals.

microbiology↗

bioRxiv2019

Zika virus infection in Collaborative Cross mice

The 2015-2016 emergence of Zika virus (ZIKV) in the Americas, and recognition that ZIKV infection during pregnancy can result in birth defects, revealed a need for small animal models to study ZIKV pathogenic mechanisms and evaluate candidate vaccines and antivirals. Mice would be an attractive system for such studies, but ZIKV replicates poorly in laboratory mice because it fails to antagonize murine STAT2 and STING. To address this, most ZIKV pathogenesis studies have used mice with impaired interferon signaling (e.g. Ifnar1-/- or treatment with IFNAR1-blocking antibodies). However, using mice with severe defects in innate antiviral signaling confounds studies of viral pathogenic mechanisms. Collaborative Cross (CC) mice have proven to be a valuable system for developing new mouse pathogenesis models for viral infections that are not well modeled in conventional laboratory mouse lines. To test whether CC mice could provide an immune-competent model for ZIKV pathogenesis, we infected CC lines with ZIKV and assessed weight loss, viremia, and production of neutralizing antibodies. We tested 21 CC lines (CC001, CC002, CC003, CC004, CC005, CC006, CC011, CC012, CC013, CC019, CC024, CC028, CC040, CC041, CC042, CC046, CC051, CC059, CC061, CC068, and CC072, 13 of which have non-functional alleles of the flavivirus restriction factor Oas1b) and 3 ZIKV strains (MR766, H/PF/2013, and a mouse-adapted variant of Dakar 41525). ZIKV infection did not induce weight loss compared to mock-infected controls and accordingly only low levels of viral RNA were detected in serum. Only a subset of mice developed neutralizing antibodies to ZIKV, likely due to overall low levels of infection and viremia. Our results are consistent with other studies demonstrating poor ZIKV infection in interferon-intact mice and suggest that the tested CC lines do not include polymorphic host genes that greatly increase susceptibility to ZIKV infection.

microbiology↗

bioRxiv2019

Oligomeric state of the ZIKV E protein defines protective immune responses.

The current leading Zika vaccine candidates in clinical testing are based on live or killed virus platforms, which have safety issues, especially in pregnant women. Zika subunit vaccines, however, have shown poor performance in preclinical studies. We hypothesized that Zika Envelope (E) protein subunit vaccines have performed poorly because the antigens tested have been recombinant E monomers that do not display critical quaternary structure epitopes present on Zika E protein homodimers that cover the surface of the virus. To test this hypothesis, we engineered and produced stable recombinant E protein homodimers. Unlike the E monomer, the dimer was recognized by strongly neutralizing monoclonal antibodies isolated from Zika-immune individuals. In a mouse model of vaccination, the dimeric antigen stimulated strongly neutralizing antibodies that targeted epitopes that were similar to epitopes recognized by human antibodies following natural Zika virus infection. In contrast, the monomer antigen stimulated lower levels of neutralizing antibodies directed to simple epitopes on domain III of E protein. In a mouse model of ZIKV challenge, only E dimer antigen stimulated protective antibodies, not the monomer. These results highlight the importance of mimicking the highly structured flavivirus surface when designing subunit vaccines. The flavivirus field has a long history of using E monomers as vaccine antigens with limited success. These results are applicable to developing second generation subunit vaccines against Zika as well as other medically important flaviviruses such as dengue and yellow fever viruses.

microbiology↗

bioRxiv2019

Altered m6A modification of specific cellular transcripts affects Flaviviridae infection

The RNA modification N6-methyladenosine (m6A) can modulate mRNA fate and thus affect many biological processes. We analyzed m6A modification across the transcriptome following infection by dengue virus (DENV), Zika virus (ZIKV), West Nile virus (WNV), and hepatitis C virus (HCV). We found that infection by these viruses in the Flaviviridae family alters m6A modification of specific cellular transcripts, including RIOK3 and CIRBP. During viral infection, the addition of m6A to RIOK3 promotes its translation, while loss of m6A in CIRBP promotes alternative splicing. Importantly, we found that activation of innate immune sensing or the endoplasmic reticulum (ER) stress response by viral infection contributes to the changes in m6A modification in RIOK3 and CIRBP, respectively. Further, several transcripts with infection-altered m6A profiles, including RIOK3 and CIRBP, encode proteins that influence DENV, ZIKV, and HCV infection. Overall, this work reveals that cellular signaling pathways activated during viral infection lead to alterations in m6A modification of host mRNAs to regulate infection.

molecular biology↗