Biology subjects

O'Connor, S. L.

Publications and source records attributed to O'Connor, S. L..

At least 19 recordsLinked to original sources

bioRxiv2026

Putative Cyclospora cayetanensis detection in wastewater metagenomic datasets

Cyclosporiasis is a foodborne illness caused by the parasite Cyclospora cayetanensis. Clinical surveillance often lags infection by weeks because diagnosis depends on a clinician ordering a test that is not part of routine parasite panels. Wastewater metagenomic sequencing does not depend on care seeking, which may be useful for early detection and community monitoring. We designed 1,670 31-mers from C. cayetanensis mature ribosomal RNA and retained 1,464 without an exact non-target match in the 28 July 2025 NCBI core_nt release. By analyzing 293 public wastewater metagenomes, we selected a threshold of 24 distinct diagnostic 31-mers on one read. Applying that threshold to 2,333 public runs from BioProject PRJNA1247874 yielded putative C. cayetanensis reads in 81 runs, or 3.5%, and in 24 of the 30 longitudinally sampled sewersheds. Detections rose through the summer in two consecutive years, matching the known seasonality of cyclosporiasis. The most parsimonious explanation is that these reads come from parasites shed into wastewater, although undescribed Cyclospora species absent from reference databases cannot be excluded. The same approach can be applied to other pathogens in existing wastewater sequencing data.

bioinformatics↗

bioRxiv2025

CD8α+ cells suppress SIV replication without evidence of viral immune escape during post treatment control

Post-treatment control (PTC) is a rare phenomenon in which people living with HIV (PLWH) maintain viral control following ART interruption. Characterizing virus populations present in PTCs may help elucidate mechanisms of immunologic control, but this is challenging without detectable plasma viremia. To model PTC, eight Mauritian cynomolgus macaques (MCM) were infected with barcoded SIVmac239M and began an 8-month ART regimen two weeks post-infection (wpi). Six months following ART interruption, all MCM were rechallenged with non-barcoded SIVmac239 followed by CD8[a]+ cell depletion two months later. Animals were grouped as viremic (n=5) or aviremic (n=3) based on the detection of plasma viremia between ART interruption and CD8[a]+ cell depletion; all animals became viremic post-depletion. Barcode sequencing of plasma virus revealed that lineages with high pre-ART viral loads dominated the rebounding populations post-depletion and detectable rechallenge virus in two animals post-depletion. Additional sequencing of three CD8+ T cell epitopes within plasma viruses identified point mutations only in viruses isolated from the viremic group post-depletion. A second cohort of 5 MCM who initiated ART 8 wpi was examined to identify the impact of the timing of ART initiation on viral epitope diversity and showed increased diversity prior to ART initiation and following ART interruption. These results suggest that early ART initiation is associated with reduced diversity within cytotoxic T lymphocyte (CTL) epitopes and a longer time to rebound, as well as highlight an important role of restricting the emergence of CTL immune escape variants in increasing the likelihood of PTC. ImportanceWhile rare, a subset of PLWH, termed post-treatment controllers (PTCs), can maintain viral control following ART interruption. However, little is known about whether this control reflects a complete absence of viral replication or continual, subclinical replication. Here we address a key knowledge gap regarding how viral populations change during CD8[a]+ cell-mediated PTC of SIV. We utilized our Mauritian cynomolgus macaque model of HIV infection, in combination with the barcoded SIVmac239M and deep sequencing, to characterize viral lineages and MHC-I-restricted CD8+ T cell epitopes throughout the study. Our findings demonstrate that early ART initiation limits viral diversity, that pre-ART replication predicts post-ART reactivation, and that CD8[a]+ cells can suppress viral replication without evidence of immune escape. These insights establish MCMs as a valuable model for dissecting mechanisms of durable ART-free viral control and highlight the potential of CD8-mediated immune control as a therapeutic target for HIV cure strategies.

microbiology↗

bioRxiv2024

Transiently boosting Vγ9+Vδ2+ γδ T cells early in Mtb coinfection of SIV-infected juvenile macaques does not improve Mtb host resistance.

Children living with HIV have a higher risk of developing tuberculosis (TB), a disease caused by the bacterium Mycobacterium tuberculosis (Mtb). Gamma delta ({gamma}{delta}) T cells in the context of HIV/Mtb coinfection have been understudied in children, despite in vitro evidence suggesting {gamma}{delta} T cells assist with Mtb control. We investigated whether boosting a specific subset of {gamma}{delta} T cells, phosphoantigen-reactive V{gamma}9+V{delta}2+ cells, could improve TB outcome using a nonhuman primate model of pediatric HIV/Mtb coinfection. Juvenile Mauritian cynomolgus macaques (MCM), equivalent to 4-8-year-old children, were infected intravenously (i.v.) with SIV. After 6 months, MCM were coinfected with a low dose of Mtb and then randomized to receive zoledronate (ZOL), a drug that increases phosphoantigen levels, (n=5; i.v.) at 3- and 17-days after Mtb accompanied by recombinant human IL-2 (s.c.) for 5 days following each ZOL injection. A similarly coinfected MCM group (n=5) was injected with saline as a control. V{gamma}9+V{delta}2+ {gamma}{delta} T cell frequencies spiked in the blood, but not airways, of ZOL+IL-2-treated MCM following the first dose, however, were refractory to the second dose. At necropsy eight weeks after Mtb, ZOL+IL-2 treatment did not reduce pathology or bacterial burden. {gamma}{delta} T cell subset frequencies in granulomas did not differ between treatment groups. These data show that transiently boosting peripheral {gamma}{delta} T cells with ZOL+IL-2 soon after Mtb coinfection of SIV-infected MCM did not improve Mtb host defense.

immunology↗

bioRxiv2023

Potent antibody-dependent cellular cytotoxicity of a V2-specific antibody is not sufficient for protection of macaques against SIV challenge

Fc-mediated antibody effector functions, such as antibody-dependent cellular cytotoxicity (ADCC), can contribute to the containment HIV-1 replication but whether such activities are sufficient for protection is unclear. We previously identified an antibody to the variable 2 (V2) apex of the HIV-1 Env trimer (PGT145) that potently directs the lysis of SIV-infected cells by NK cells but poorly neutralizes SIV infectivity. To determine if ADCC is sufficient for protection, separate groups of six rhesus macaques were treated with PGT145 or a control antibody (DEN3) by intravenous infusion followed five days later by intrarectal challenge with SIVmac239. Despite high concentrations of PGT145 and potent ADCC activity in plasma on the day of challenge, all animals became infected and viral loads did not differ between the PGT145- and DEN3-treated animals. To determine if PGT145 can protect against a neutralization-sensitive virus, two additional groups of six macaques were treated with PGT145 and DEN3 and challenged with an SIVmac239 variant with a single amino acid change in Env (K180S) that increases PGT145 binding and renders the virus susceptible to neutralization by this antibody. Although there was no difference in virus acquisition, peak and chronic phase viral loads were significantly lower and time to peak viremia was significantly delayed in the PGT145-treated animals compared to the DEN3-treated control animals. Env changes were also selected in the PGT145-treated animals that confer resistance to both neutralization and ADCC. These results show that ADCC is not sufficient for protection by this V2-specific antibody. However, protection may be achieved by increasing the affinity of antibody binding to Env above the threshold required for detectable viral neutralization. Author SummaryAntibodies that bind to the human immunodeficiency virus (HIV-1) envelope glycoprotein (Env) on virions can neutralize viral infectivity. Antibodies may also bind to Env on the surface of virus-infected cells and recruit immune cells to eliminate the productively infected cells through a process known as antibody dependent cellular cytotoxicity (ADCC). In rare instances, certain antibodies are capable of mediating ADCC despite negligible neutralizing activity. Such antibodies are thought to have contributed to the modest protection observed in the RV144 HIV-1 vaccine trial and in some nonhuman primate studies. One antibody, PGT145, was found to cross-react with simian immunodeficiency virus (SIV) and to mediate potent ADCC against SIV-infected cells despite weak neutralization of viral infectivity. We therefore tested if the potent ADCC activity of PGT145 could protect rhesus macaques against mucosal challenge with pathogenic SIV. PGT145 did not protect against wild-type SIVmac239, but did protect against an SIVmac239 variant with a single amino acid substitution in Env (K180S) that increases antibody binding to Env and makes the virus susceptible to neutralization. Thus, while ADCC may contribute to protection against immunodeficiency viruses through the elimination of productively infected cells, the higher affinity of Env binding necessary for potent neutralization is a critical determinant of antibody-mediated protection.

microbiology↗

bioRxiv2023

Wolbachia-mediated resistance to Zika virus infection in Aedes aegypti is dominated by diverse transcriptional regulation and weak evolutionary pressures

A promising candidate for arbovirus control and prevention relies on replacing arbovirus-susceptible Aedes aegypti populations with mosquitoes that have been colonized by the intracellular bacterium Wolbachia and thus have a reduced capacity to transmit arboviruses. This reduced capacity to transmit arboviruses is mediated through a phenomenon referred to as pathogen blocking. Pathogen blocking has primarily been proposed as a tool to control dengue virus (DENV) transmission, however it works against a range of viruses, including Zika virus (ZIKV). Despite years of research, the molecular mechanisms underlying pathogen blocking still need to be better understood. Here, we used RNA-seq to characterize mosquito gene transcription dynamics in Ae. aegypti infected with the wMel strain of Wolbachia that are being released by the World Mosquito Program in Medellin, Colombia. Comparative analyses using ZIKV-infected, uninfected tissues, and mosquitoes without Wolbachia revealed that the influence of wMel on mosquito gene transcription is multifactorial. Importantly, because Wolbachia limits, but does not completely prevent, replication of ZIKV and other viruses in coinfected mosquitoes, there is a possibility that these viruses could evolve resistance to pathogen blocking. Therefore, to understand the influence of Wolbachia on within-host ZIKV evolution, we characterized the genetic diversity of molecularly barcoded ZIKV virus populations replicating in Wolbachia-infected mosquitoes and found that within-host ZIKV evolution was subject to weak purifying selection and, unexpectedly, loose anatomical bottlenecks in the presence and absence of Wolbachia. Together, these findings suggest that there is no clear transcriptional profile associated with Wolbachia-mediated ZIKV restriction, and that there is no evidence for ZIKV escape from this restriction in our system. Author SummaryWhen Wolbachia bacteria infect Aedes aegypti mosquitoes, they dramatically reduce the mosquitoes susceptibility to infection with a range of arthropod-borne viruses, including Zika virus (ZIKV). Although this pathogen-blocking effect has been widely recognized, its mechanisms remain unclear. Furthermore, because Wolbachia limits, but does not completely prevent, replication of ZIKV and other viruses in coinfected mosquitoes, there is a possibility that these viruses could evolve resistance to Wolbachia-mediated blocking. Here, we use host transcriptomics and viral genome sequencing to examine the mechanisms of ZIKV pathogen blocking by Wolbachia and viral evolutionary dynamics in Ae. aegypti mosquitoes. We find complex transcriptome patterns that do not suggest a single clear mechanism for pathogen blocking. We also find no evidence that Wolbachia exerts detectable selective pressures on ZIKV in coinfected mosquitoes. Together our data suggest that it may be difficult for ZIKV to evolve Wolbachia resistance, perhaps due to the complexity of the pathogen blockade mechanism.

molecular biology↗

bioRxiv2023

Gain without pain: Adaptation and increased virulence of Zika virus in vertebrate host without fitness cost in mosquito vector

Zika virus (ZIKV) is now in a post-pandemic period, for which the potential for re-emergence and future spread is unknown. Adding to this uncertainty is the unique capacity of ZIKV to directly transmit between humans via sexual transmission. Recently, we demonstrated that direct transmission of ZIKV between vertebrate hosts leads to rapid adaptation resulting in enhanced virulence in mice and the emergence of three amino acid substitutions (NS2A-A117V, NS2A- A117T, and NS4A-E19G) shared among all vertebrate-passaged lineages. Here, we further characterized these host-adapted viruses and found that vertebrate-passaged viruses also have enhanced transmission potential in mosquitoes. To understand the contribution of genetic changes to the enhanced virulence and transmission phenotype, we engineered these amino acid substitutions, singly and in combination, into a ZIKV infectious clone. We found that NS4A- E19G contributed to the enhanced virulence and mortality phenotype in mice. Further analyses revealed that NS4A-E19G results in increased neurotropism and distinct innate immune signaling patterns in the brain. None of the substitutions contributed to changes in transmission potential in mosquitoes. Together, these findings suggest that direct transmission chains could enable the emergence of more virulent ZIKV strains without compromising mosquito transmission capacity, although the underlying genetics of these adaptations are complex.

microbiology↗

bioRxiv2023

CD8+ cells and small viral reservoirs facilitate post-ART control of SIV in Mauritian cynomolgus macaques

Sustainable HIV remission after antiretroviral therapy (ART) withdrawal, or post-treatment control (PTC), remains a top priority for HIV treatment. We observed surprising PTC in an MHC-haplomatched cohort of MHC-M3+ SIVmac239+ Mauritian cynomolgus macaques (MCMs) initiated on ART at two weeks post-infection (wpi). For six months after ART withdrawal, we observed undetectable or transient viremia in seven of eight MCMs. In vivo depletion of CD8+ cells induced rebound in all animals, indicating the PTC was mediated, at least in part, by CD8+ cells. We found that MCMs had smaller acute viral reservoirs than a cohort of identically infected rhesus macaques, a population that rarely develops PTC. The mechanisms by which unusually small viral reservoirs and CD8+ cell-mediated virus suppression enable PTC can be investigated using this MHC-haplomatched MCM model. Further, defining the immunologic mechanisms that engender PTC in this model may identify therapeutic targets for inducing durable HIV remission in humans.

immunology↗

bioRxiv2022

Host Immunity to Mycobacterium tuberculosis Infection is Similar in Simian Immunodeficiency Virus (SIV)-infected, Antiretroviral Therapy-treated and SIV-naïve Juvenile Macaques

Pre-existing HIV infection increases tuberculosis (TB) risk in children. Antiretroviral therapy (ART) reduces, but does not abolish, this risk in children with HIV. The immunologic mechanisms involved in TB progression in both HIV-naive and HIV-infected children have not been explored. Much of our current understanding is based on human studies in adults and adult animal models. In this study, we sought to model childhood HIV/Mycobacterium tuberculosis (Mtb) coinfection in the setting of ART and characterize T cells during TB progression. Macaques equivalent to 4-8 year-old children were intravenously infected with SIVmac239M, treated with ART three months later, and coinfected with Mtb three months after initiating ART. SIV-naive macaques were similarly infected with Mtb alone. TB pathology and total Mtb burden did not differ between SIV-infected, ART-treated and SIV-naive macaques, although lung Mtb burden was lower in SIV-infected, ART-treated macaques. No major differences in frequencies of CD4+ and CD8+ T cells and unconventional T cell subsets (V{gamma}9+ {gamma}{delta} T cells, MAIT cells, and NKT cells) in airways were observed between SIV-infected, ART-treated and SIV-naive macaques over the course of Mtb infection, with the exception of CCR5+ CD4+ and CD8+ T cells which were slightly lower. CD4+ and CD8+ T cell frequencies did not differ in the lung granulomas obtained at necropsy, nor did they differ in the frequency of immune checkpoint and proliferative markers. Thus, ART treatment of juvenile macaques, three months after SIV infection, resulted in similar progression of Mtb and T cell responses compared to Mtb in SIV-naive macaques.

immunology↗

bioRxiv2022

Mycobacterium tuberculosis-specific CD4 T cells expressing transcription factors associate with bacterial control in granulomas

Despite the extensive research on CD4 T cells within the context of Mycobacterium tuberculosis (Mtb) infection, few studies have focused on identifying and investigating the profile of Mtb-specific T cells within lung granulomas. To facilitate identification of Mtb-specific CD4 T cells, we identified immunodominant epitopes for two Mtb proteins, Rv1196 and Rv0125, using a Mauritian cynomolgus macaque model of Mtb infection, providing data for the synthesis of MHC Class II tetramers. Using tetramers, we identified Mtb-specific cells within different immune compartments post-infection. We found that granulomas were enriched sites for Mtb-specific cells and that tetramer+ cells had increased frequencies of the activation marker CD69, and transcription factors T-bet and ROR{gamma}T, compared to tetramer negative cells within the same sample. Our data revealed that while the frequency of Rv1196 tetramer+ cells was positively correlated with granuloma bacterial burden, the frequency of ROR{gamma}T or T-bet within tetramer+ cells was inversely correlated with granuloma bacterial burden highlighting the importance of having activated, functional Mtb-specific cells for control of Mtb in lung granulomas.

immunology↗

bioRxiv2022

A NEW VARIANT OF HEPATITIS A VIRUS CAUSING TRANSIENT LIVER ENZYME ELEVATIONS IN MAURITIUS-ORIGIN LABORATORY-HOUSED CYNOMOLGUS MACAQUES

Hepatitis A virus (HAV) infects humans and non-human primates causing an acute self-limited illness. Three HAV genotypes have been described for humans and three genotypes have been described for non-human primates. We observed transiently elevated liver enzymes in Mauritius-origin laboratory-housed macaques in Germany and were not able to demonstrate HAV by serology and PCR. Using deep sequencing, we have identified a new HAV genotype with 86% nucleotide sequence homology to HAV genotype IV capsid proteins and approximately 80% nucleotide homology to other HAV genotypes. In situ hybridization indicates persistence in the biliary epithelium up to 3 months after liver enzymes were elevated. Vaccination using a commercial vaccine against human HAV prevented reoccurrence of liver enzyme elevations. Since available assays for HAV did not detect this new variant, knowledge of its existence may ameliorate potential significant epidemiological and research implications in laboratories globally. Article Summary LineA new genotype of hepatitis A virus, that was not identifiable by available diagnostic assays, caused liver enzyme elevations in laboratory-housed Mauritius-origin Cynomolgus macaques.

microbiology↗

bioRxiv2022

The cognitive basis of intracranial self-stimulation of midbrain dopamine neurons

Recently there has been a reckoning in the dopamine field. This has suggested that the dopamine prediction error may function as a teaching signal, without endowing preceding events with value. We studied the cognitive basis of intracranial self-stimulation (ICSS), a setting where dopamine appears to be valuable. Physiological frequencies seen during reinforcement learning did not support robust ICSS or promote behavior that would indicate the stimulation was represented as a meaningful reward in a specific or general sense. This was despite demonstrating that this same physiologically-relevant signal could function as a teaching signal. However, supraphysiological frequencies supported robust ICSS where the stimulation was represented as a specific sensory event, which acted as a goal to motivate behavior. This demonstrates that dopamine neurons only support ICSS at supraphysiological frequencies, and in a manner that does not reflect our subjective experience with endogenous firing of dopamine neurons during reinforcement learning. One sentence summaryDopamine neurons only support ICSS at supraphysiological frequencies and in a manner not reflecting dopamines role in learning.

neuroscience↗

bioRxiv2022

Transient T cell expansion, activation, and proliferation in therapeutically vaccinated SIV+ macaques treated with N-803

Vaccine strategies aimed at eliciting HIV-specific CD8+ T cells are one major target of interest in HIV functional cure strategies. We hypothesized that CD8+ T cells elicited by therapeutic vaccination during antiretroviral therapy (ART) would be recalled and boosted by treatment with the IL-15 superagonist N-803 after ART discontinuation. We intravenously immunized four SIV+ Mauritian cynomolgus macaques (MCM) receiving ART with vesicular stomatitis virus (VSV), modified vaccinia virus Ankara strain (MVA), and recombinant adenovirus serotype 5 (rAd-5) vectors all expressing SIVmac239 Gag. Immediately after ART cessation, these animals received three doses of N-803. Four control animals received no vaccines or N-803. The vaccine regimen generated a high magnitude of Gag-specific CD8+ T cells that were proliferative and biased toward an effector memory phenotype. We then compared cells elicited by vaccination (Gag-specific) to cells elicited by SIV infection and unaffected by vaccination (Nef-specific). We found that N-803 treatment enhanced both the frequencies of bulk and proliferating antigen-specific CD8+ T cells elicited by vaccination and the antigen-specific CD8+ T cells elicited by SIV infection. In sum, we demonstrate that a therapeutic heterologous prime-boost-boost (HPBB) vaccine can elicit antigen-specific effector memory CD8+ T cells that are boosted by N-803.

immunology↗

bioRxiv2022

IL-15 superagonist N-803 enhances IFNγ production and alters the trafficking of MAIT cells in SIV+ macaques

Mucosal Associated Invariant T cells (MAIT cells) are innate T cells that recognize bacterial metabolites and secrete cytokines and cytolytic enzymes to destroy infected target cells. This makes MAIT cells promising targets for immunotherapy to combat bacterial infections. Here, we analyzed the effects of an immunotherapeutic agent, the IL-15 superagonist N-803, on MAIT cell activation, trafficking, and cytolytic function in macaques. We found that N-803 could activate MAIT cells in vitro and increase their ability to produce IFN{gamma} in response to bacterial stimulation. To expand upon this, we examined the phenotypes and function of MAIT cells present in samples collected from PBMC, airways (BAL), and lymph nodes (LN) from rhesus macaques that were treated in vivo with N-803. N-803 treatment led to a transient 6-7 fold decrease in the total number of MAIT cells in the peripheral blood relative to pre N-803 timepoints. Concurrent with the decrease in cells in the peripheral blood, we observed a rapid decline in the frequency of CXCR3+CCR6+ MAITs. This corresponded with an increase in the frequency of CCR6+ MAITs in BAL, and higher frequencies of ki-67+ and granzyme B+ MAITs in blood, LN, and BAL. Finally, N-803 improved the ability of MAIT cells collected from PBMC and airways to produce IFN{gamma} in response to bacterial stimulation. Overall, N-803 shows the potential to transiently alter the trafficking and enhance the antibacterial activity of MAIT cells which could be combined with other strategies to combat bacterial infections.

immunology↗

bioRxiv2022

Control of SIV infection in prophylactically vaccinated, ART-naïve macaques is required for the most efficacious CD8 T cell response during treatment with the IL-15 superagonist N-803

The IL-15 superagonist N-803 has been shown to enhance the function of CD8 T cells and NK cells. We previously found that in a subset of vaccinated, ART-naive, SIV+ rhesus macaques, N-803 treatment led to a rapid but transient decline in plasma viremia that positively correlated with an increase in the frequency of CD8 T cells. Here we tested the hypothesis that prophylactic vaccination was required for N-803 mediated suppression of SIV plasma viremia. We vaccinated rhesus macaques with a DNA prime/Ad5 boost regimen using vectors expressing SIVmac239 gag, with or without a plasmid expressing IL-12, or left them unvaccinated. Animals were then intravenously infected with SIVmac239M. Six months after infection, animals were treated with N-803. We found no differences in control of plasma viremia during N-803 treatment between vaccinated and unvaccinated macaques. Furthermore, the SIV-specific CD8 T cells displayed no differences in frequency or ability to traffic to the lymph nodes. Interestingly, when we divided the SIV+ animals based on plasma viral load set-point prior to N-803 treatment, N-803 increased the frequency of SIV-specific T cells expressing ki-67+ and granzyme B+ in animals with low plasma viremia (<104 copies/mL; SIV controllers) compared to animals with high plasma viremia (>104 copies/mL;SIV non-controllers). In addition, Gag-specific CD8 T cells from the SIV+ controllers had a greater increase in CD107a+CD8+ T cells when compared to SIV+ non-controllers. Overall, our results indicate that N-803 is most effective in SIV+ animals with a pre-existing immunological ability to control SIV replication.

immunology↗

bioRxiv2021

Zika virus infection of pregnant Ifnar1-/- mice triggers strain-specific differences in fetal outcomes

Zika virus (ZIKV) is a flavivirus that causes a constellation of adverse fetal outcomes collectively termed Congenital Zika Syndrome (CZS). However, not all pregnancies exposed to ZIKV result in an infant with apparent defects. During the 2015-2016 American outbreak of ZIKV, CZS rates varied by geographic location. The underlying mechanisms responsible for this heterogeneity in outcomes have not been well defined. Therefore, we sought to characterize and compare the pathogenic potential of multiple Asian/American-lineage ZIKV strains in an established Ifnar1-/- pregnant mouse model. Here, we show significant differences in the rate of fetal demise following maternal inoculation with ZIKV strains from Puerto Rico, Panama, Mexico, Brazil, and Cambodia. Rates of fetal demise broadly correlated with maternal viremia but were independent of fetus and placenta virus titer, indicating that additional underlying factors contribute to fetus outcome. Our results, in concert with those from other studies, suggest that subtle differences in ZIKV strains may have important phenotypic impacts. With ZIKV now endemic in the Americas, greater emphasis needs to be placed on elucidating and understanding the underlying mechanisms that contribute to fetal outcome. IMPORTANCEZika virus (ZIKV) actively circulates in 89 countries and territories around the globe. ZIKV infection during pregnancy is associated with adverse fetal outcomes including birth defects, microcephaly, neurological complications, and even spontaneous abortion. Rates of adverse fetal outcomes vary between regions, and not every pregnancy exposed to ZIKV results in birth defects. Not much is known about how or if the infecting ZIKV strain is linked to fetal outcomes. Our research provides evidence of phenotypic heterogeneity between Asian/American-lineage ZIKV strains and provides insight into the underlying causes of adverse fetal outcomes. Understanding ZIKV strain-dependent pathogenic potential during pregnancy and elucidating underlying causes of diverse clinical sequelae observed during human infections is critical to understanding ZIKV on a global scale.

microbiology↗

bioRxiv2021

Spontaneous control of SIV replication does not prevent immune dysregulation and bacterial dissemination in animals co-infected with M. tuberculosis

Individuals infected with both HIV and Mycobacterium tuberculosis (Mtb) are more likely to develop severe Tuberculosis (TB) disease than HIV-naive individuals. To understand how a chronic pre-existing Simian immunodeficiency virus (SIV) infection impairs the early immune response to Mtb, we used the Mauritian cynomolgus macaque (MCM) model of SIV/Mtb co-infection. We examined the relationship between peripheral viral control and Mtb burden, Mtb dissemination, and immunological function between SIV+ spontaneous controllers, SIV+ non-controllers, and SIV-naive MCM who were challenged with a barcoded Mtb Erdman strain and necropsied six weeks post infection. Mycobacterial burden was highest in the SIV+ non-controllers in all assessed tissues. In lung granulomas, we found the frequency of CD4+ T cells producing TNF was reduced in all SIV+ MCM, but CD4+ T cells producing IFN{gamma} were only lower in the SIV+ non-controllers. Further, while all SIV+ MCM had more PD1+ and TIGIT+ T cells in the lung granulomas relative to SIV-naive MCM, SIV+ controllers exhibited the highest frequency of cells expressing these markers. To measure the effect of SIV infection on within-host bacterial dissemination, we sequenced the molecular barcodes of Mtb present in each tissue and characterized the complexity of the Mtb populations. While Mtb population complexity was not associated with infection group, lymph nodes had increased complexity when compared to lung granulomas across all groups. These results provide evidence SIV+ animals, independent of viral control, exhibit dysregulated immune responses and enhanced dissemination of Mtb, likely contributing to the poor TB disease course across all SIV/Mtb co-infected animals. ImportanceHIV and TB remain significant global health issues, despite the availability of treatments. Individuals with HIV, including those who are virally suppressed, are at an increased risk to develop and succumb to severe TB disease when compared to HIV-naive individuals. Our study aims to understand the relationship between SIV replication, mycobacterial growth, and immunological function in the tissues of co-infected Mauritian cynomolgus macaques during the early phase of Mtb infection. Here we demonstrate that increased viral replication is associated with increased bacterial burden in the tissues and impaired immunologic responses, and that the damage attributed to virus infection is not fully eliminated when animals spontaneously control virus replication.

microbiology↗

bioRxiv2020

Mathematical modeling of N-803 treatment in SIV-infected non-human primates

Immunomodulatory drugs could contribute to a functional cure for Human Immunodeficiency Virus (HIV). Interleukin-15 (IL-15) promotes expansion and activation of CD8+ T cell and natural killer (NK) cell populations. In one study, an IL-15 superagonist, N-803, suppressed Simian Immunodeficiency Virus (SIV) in non-human primates (NHPs) who had received prior SIV vaccination. However, viral suppression attenuated with continued N-803 treatment, partially returning after long treatment interruption. While there is evidence of concurrent drug tolerance, immune regulation, and viral escape, the relative contributions of these mechanisms to the observed viral dynamics have not been quantified. Here, we utilize mathematical models of N-803 treatment in SIV-infected macaques to estimate contributions of these three key mechanisms to treatment outcomes: 1) drug tolerance, 2) immune regulation, and 3) viral escape. We calibrated our model to viral and lymphocyte responses from the above-mentioned NHP study. Our models track CD8+ T cell and NK cell populations with N-803-dependent proliferation and activation, as well as viral dynamics in response to these immune cell populations. We compared mathematical models with different combinations of the three key mechanisms based on Akaike Information Criterion and important qualitative features of the NHP data. Two minimal models were capable of reproducing the observed SIV response to N-803. In both models, immune regulation strongly reduced cytotoxic cell activation to enable viral rebound. Either long-term drug tolerance or viral escape (or some combination thereof) could account for changes to viral dynamics across long breaks in N-803 treatment. Theoretical explorations with the models showed that less-frequent N-803 dosing and concurrent immune regulation blockade (e.g. PD-L1 inhibition) may improve N-803 efficacy. However, N-803 may need to be combined with other immune therapies to countermand viral escape from the CD8+ T cell response. Our mechanistic model will inform such therapy design and guide future studies. Author summaryImmune therapy may be a critical component in the functional cure for Human Immunodeficiency Virus (HIV). N-803 is an immunotherapeutic drug that activates antigen-specific CD8+ T cells of the immune system. These CD8+ T cells eliminate HIV-infected cells in order to limit the spread of infection in the body. In one study, N-803 reduced plasma viremia in macaques that were infected with Simian Immunodeficiency Virus, an analog of HIV. Here, we used mathematical models to analyze the data from this study to better understand the effects of N-803 therapy on the immune system. Our models indicated that inhibitory signals may be reversing the stimulatory effect of N-803. Results also suggested the possibilities that tolerance to N-803 could build up within the CD8+ T cells themselves and that the treatment may be selecting for virus strains that are not targeted by CD8+ T cells. Our models predict that N-803 therapy may be made more effective if the time between doses is increased or if inhibitory signals are blocked by an additional drug. Also, N-803 may need to be combined with other immune therapies to target virus that would otherwise evade CD8+ T cells.

systems biology↗

bioRxiv2020

The dual orexin/hypocretin receptor antagonist suvorexant reduces addiction-like behaviors for the opioid fentanyl

The orexin (hypocretin) system is critical for motivated seeking of all drugs of abuse, including opioids. In 2019, the National Institute on Drug Addiction (NIDA) identified the orexin system as a high priority target mechanism for novel pharmacological therapies to treat opioid use disorder (OUD). Suvorexant (Belsomra) is a dual orexin receptor 1/orexin receptor 2 (OxR1/OxR2) antagonist that is FDA-approved for the treatment of insomnia, and thus has the potential to be readily repurposed for the treatment of OUD. However, studies have yet to test the therapeutic potential of suvorexant with respect to reducing opioid-related behaviors. Accordingly, here we investigated the efficacy of suvorexant in reducing several addiction-relevant behaviors in fentanyl self-administrating rats. In rats with limited drug experience, suvorexant decreased motivation for fentanyl on a behavioral economics (BE) task. This effect was greatest in rats with the highest motivation for fentanyl. Suvorexant was even more effective at decreasing motivation for fentanyl following induction of a more robust addiction phenotype by intermittent access (IntA) self-administration of the opioid. Suvorexant also attenuated punished responding for fentanyl and reduced cued reinstatement in IntA rats. Suvorexant did not affect general locomotor activity or natural reward seeking, indicating that at the doses used here, suvorexant can be used to reduce drug seeking with limited sedative or off-target effects. Together, these results highlight the therapeutic potential of suvorexant, particularly in individuals with the severe OUD.

neuroscience↗