Reported Xylazine Use Among Adults Aged ≥18 Years Evaluated for Substance Use Treatment - United States, July 2022-September 2023.

Xylazine has been increasingly detected in illegally manufactured fentanyl (IMF) products and overdose deaths in the United States; most xylazine-involved overdose deaths involve IMF. A convenience sample of U.S. adults aged ≥18 years was identified from those evaluated for substance use treatment during July 2022-September 2023. Data were collected using the Addiction Severity Index-Multimedia Version clinical assessment tool. Among 43,947 adults, 6,415 (14.6%) reported IMF or heroin as their primary lifetime substance-use problem; 5,344 (12.2%) reported recent (i.e., past-30-day) IMF or heroin use. Among adults reporting IMF or heroin as their primary lifetime substance-use problem, 817 (12.7%) reported ever using xylazine. Among adults reporting recent IMF or heroin use, 443 (8.3%) reported recent xylazine use. Among adults reporting IMF or heroin use recently or as their primary lifetime substance-use problem, those reporting xylazine use reported a median of two past nonfatal overdoses from any drug compared with a median of one overdose among those who did not report xylazine use; as well, higher percentages of persons who reported xylazine use reported other recent substance use and polysubstance use. Provision of nonjudgmental care and services, including naloxone, wound care, and linkage to and retention of persons in effective substance use treatment, might reduce harms including overdose among persons reporting xylazine use.

Pattern of Buprenorphine Treatment Retention Among Youth Aged 10 to 18 Years-US, 2015 to 2021.

This cohort study investigates patterns of buprenorphine treatment retention among US youth aged 10 to 18 years from 2015 to 2021.

Human Macrophages Activate Bystander Neutrophils' Metabolism and Effector Functions When Challenged with Mycobacterium tuberculosis.

Neutrophils are dynamic cells, playing a critical role in pathogen clearance; however, neutrophil infiltration into the tissue can act as a double-edged sword. They are one of the primary sources of excessive inflammation during infection, which has been observed in many infectious diseases including pneumonia and active tuberculosis (TB). Neutrophil function is influenced by interactions with other immune cells within the inflammatory lung milieu; however, how these interactions affect neutrophil function is unclear. Our study examined the macrophage-neutrophil axis by assessing the effects of conditioned medium (MΦ-CM) from primary human monocyte-derived macrophages (hMDMs) stimulated with LPS or a whole bacterium (Mycobacterium tuberculosis) on neutrophil function. Stimulated hMDM-derived MΦ-CM boosts neutrophil activation, heightening oxidative and glycolytic metabolism, but diminishes migratory potential. These neutrophils exhibit increased ROS production, elevated NET formation, and heightened CXCL8, IL-13, and IL-6 compared to untreated or unstimulated hMDM-treated neutrophils. Collectively, these data show that MΦ-CM from stimulated hMDMs activates neutrophils, bolsters their energetic profile, increase effector and inflammatory functions, and sequester them at sites of infection by decreasing their migratory capacity. These data may aid in the design of novel immunotherapies for severe pneumonia, active tuberculosis and other diseases driven by pathological inflammation mediated by the macrophage-neutrophil axis.

Characteristics of Alcohol, Marijuana, and Other Drug Use Among Persons Aged 13-18 Years Being Assessed for Substance Use Disorder Treatment - United States, 2014-2022.

Substance use often begins during adolescence, placing youths at risk for fatal overdose and substance use disorders (SUD) in adulthood. Understanding the motivations reported by adolescents for using alcohol, marijuana, and other drugs and the persons with whom they use these substances could guide strategies to prevent or reduce substance use and its related consequences among adolescents. A cross-sectional study was conducted among adolescents being assessed for SUD treatment in the United States during 2014-2022, to examine self-reported motivations for using substances and the persons with whom substances were used. The most commonly reported motivation for substance use was "to feel mellow, calm, or relaxed" (73%), with other stress-related motivations among the top reasons, including "to stop worrying about a problem or to forget bad memories" (44%) and "to help with depression or anxiety" (40%); one half (50%) reported using substances "to have fun or experiment." The majority of adolescents reported using substances with friends (81%) or using alone (50%). These findings suggest that interventions related to reducing stress and addressing mental health concerns might reduce these leading motivations for substance use among adolescents. Education for adolescents about harm reduction strategies, including the danger of using drugs while alone and how to recognize and respond to an overdose, can reduce the risk for fatal overdose.

Sources of nonmedically used prescription psychotherapeutic drugs using real-world data from adolescents and adults assessed for substance use treatment--2014-2022.

BACKGROUND: Nonmedical use (NMU) of prescription psychotherapeutic drugs (PPD) may increase risk for significant morbidity and mortality in the overdose crisis. OBJECTIVE: This study examines sources of PPD using real-world data from adolescents and adults reporting past 30-day NMU of PPDs. METHODS: A convenience sample of individuals aged ≥10 years assessed for substance use disorders (SUD) treatment was analyzed using the 2014-2022 National Addictions Vigilance Intervention and Prevention Program datasets. PPD include prescription opioids, prescription tranquilizers/sedatives, and prescription stimulants. RESULTS: Overall, among assessments of adolescents aged 10-18 years (N = 1991) and young adults aged 19-24 years (N = 15,166), "family/friend" (46.08-47.41 %) and "dealer" (33.82-42.71 %) were the most common sources. Among assessments of adults aged ≥25 years (N = 89,225), "own prescription" was the most common source and increased in frequency as age increased. Across all age groups, "family/friend" was the most frequent source for all drug classes (41.96-48.76 %) except for nonmedically used buprenorphine/methadone, for which "own prescription" was the most common source (51.85 %) among adults. CONCLUSIONS: Our study demonstrates heterogeneity in sources of nonmedically used PPD across age groups. Tailored prevention strategies for different age groups and improving timely access to medical care to ensure proper treatment of chronic medical conditions including SUD are needed.

Structural Analysis of Membrane-associated Forms of Helicobacter pylori VacA Toxin.

Helicobacter pylori colonizes the stomach in about half of the human population, leading to an increased risk of peptic ulcer disease and gastric cancer. H. pylori secretes an 88 kDa VacA toxin that contributes to pathogenesis. VacA assembles into oligomeric complexes in solution and forms anion-selective channels in cell membranes. Cryo-electron microscopy (cryo-EM) analyses of VacA oligomers in solution provided insights into VacA oligomerization but failed to reveal the structure of the hydrophobic N-terminal region predicted to be a pore-forming domain. In this study, we incubated VacA with liposomes and used single particle cryo-EM to analyze detergent-extracted VacA oligomers. A 3D structure of detergent-solubilized VacA hexamers revealed the presence of six α-helices extending from the center of the oligomers, a feature not observed in previous studies of water-soluble VacA oligomers. Cryo-electron tomography analysis and 2D averages of VacA associated with liposomes confirmed that central regions of the membrane-associated VacA oligomers can insert into the lipid bilayer. However, insertion is heterogenous, with some membrane-associated oligomers appearing only partially inserted and others sitting on top of the bilayer. These studies indicate that VacA undergoes a conformational change when contacting the membrane and reveal an α-helical region positioned to extend into the membrane. Although the reported VacA 3D structure does not represent a selective anion channel, our combined single particle 3D analysis, cryo-electron tomography, and modeling allow us to propose a model for the structural organization of the VacA N-terminus in the context of a hexamer as it inserts into the membrane.

Structural analysis of the P132L disease mutation in caveolin-1 reveals its role in the assembly of oligomeric complexes.

Caveolin-1 (CAV1) is a membrane-sculpting protein that oligomerizes to generate flask-shaped invaginations of the plasma membrane known as caveolae. Mutations in CAV1 have been linked to multiple diseases in humans. Such mutations often interfere with oligomerization and the intracellular trafficking processes required for successful caveolae assembly, but the molecular mechanisms underlying these defects have not been structurally explained. Here, we investigate how a disease-associated mutation in one of the most highly conserved residues in CAV1, P132L, affects CAV1 structure and oligomerization. We show that P132 is positioned at a major site of protomer-protomer interactions within the CAV1 complex, providing a structural explanation for why the mutant protein fails to homo-oligomerize correctly. Using a combination of computational, structural, biochemical, and cell biological approaches, we find that despite its homo-oligomerization defects P132L is capable of forming mixed hetero-oligomeric complexes with WT CAV1 and that these complexes can be incorporated into caveolae. These findings provide insights into the fundamental mechanisms that control the formation of homo- and hetero-oligomers of caveolins that are essential for caveolae biogenesis, as well as how these processes are disrupted in human disease.

Multiple Sites on Glycoprotein H (gH) Functionally Interact with the gB Fusion Protein to Promote Fusion during Herpes Simplex Virus (HSV) Entry.

Enveloped virus entry requires fusion of the viral envelope with a host cell membrane. Herpes simplex virus 1 (HSV-1) entry is mediated by a set of glycoproteins that interact to trigger the viral fusion protein glycoprotein B (gB). In the current model, receptor-binding by gD signals a gH/gL heterodimer to trigger a refolding event in gB that fuses the membranes. To explore functional interactions between gB and gH/gL, we used a bacterial artificial chromosome (BAC) to generate two HSV-1 mutants that show a small plaque phenotype due to changes in gB. We passaged the viruses to select for restoration of plaque size and analyzed second-site mutations that arose in gH. HSV-1 gB was replaced either by gB from saimiriine herpesvirus 1 (SaHV-1) or by a mutant form of HSV-1 gB with three alanine substitutions in domain V (gB3A). To shift the selective pressure away from gB, the gB3A virus was passaged in cells expressing gB3A. Sequencing of passaged viruses identified two interesting mutations in gH, including gH-H789Y in domain IV and gH-S830N in the cytoplasmic tail (CT). Characterization of these gH mutations indicated they are responsible for the enhanced plaque size. Rather than being globally hyperfusogenic, both gH mutations partially rescued function of the specific gB version present during their selection. These sites may represent functional interaction sites on gH/gL for gB. gH-H789 may alter the positioning of a membrane-proximal flap in the gH ectodomain, whereas gH-S830 may contribute to an interaction between the gB and gH CTs. IMPORTANCE Enveloped viruses enter cells by fusing their envelope with the host cell membrane. Herpes simplex virus 1 (HSV-1) entry requires the coordinated interaction of several viral glycoproteins, including gH/gL and gB. gH/gL and gB are essential for virus replication and both proteins are targets of neutralizing antibodies. gB fuses the membranes after being activated by gH/gL, but the details of how gH/gL activates gB are not known. This study examined the gH/gL-gB interaction using HSV-1 mutants that displayed reduced virus entry due to changes in gB. The mutant viruses were grown over time to select for additional mutations that could partially restore entry. Two mutations in gH (H789Y and S830N) were identified. The positions of the mutations in gH/gL may represent sites that contribute to gB activation during virus entry.

Trained immunity is induced in humans after immunization with an adenoviral vector COVID-19 vaccine.

BackgroundHeterologous effects of vaccines are mediated by "trained immunity," whereby myeloid cells are metabolically and epigenetically reprogrammed, resulting in heightened responses to subsequent insults. Adenovirus vaccine vector has been reported to induce trained immunity in mice. Therefore, we sought to determine whether the ChAdOx1 nCoV-19 vaccine (AZD1222), which uses an adenoviral vector, could induce trained immunity in vivo in humans.MethodsTen healthy volunteers donated blood on the day before receiving the ChAdOx1 nCoV-19 vaccine and on days 14, 56, and 83 after vaccination. Monocytes were purified from PBMCs, cell phenotype was determined by flow cytometry, expression of metabolic enzymes was quantified by RT-qPCR, and production of cytokines and chemokines in response to stimulation ex vivo was analyzed by multiplex ELISA.ResultsMonocyte frequency and count were increased in peripheral blood up to 3 months after vaccination compared with their own prevaccine controls. Expression of HLA-DR, CD40, and CD80 was enhanced on monocytes for up to 3 months following vaccination. Moreover, monocytes had increased expression of glycolysis-associated enzymes 2 months after vaccination. Upon stimulation ex vivo with unrelated antigens, monocytes produced increased IL-1ß, IL-6, IL-10, CXCL1, and MIP-1α and decreased TNF, compared with prevaccine controls. Resting monocytes produced more IFN-γ, IL-18, and MCP-1 up to 3 months after vaccination compared with prevaccine controls.ConclusionThese data provide evidence for the induction of trained immunity following a single dose of the ChAdOx1 nCoV-19 vaccine.FundingThis work was funded by the Health Research Board (EIA-2019-010) and Science Foundation Ireland Strategic Partnership Programme (proposal ID 20/SPP/3685).

Quantifying the impact of immune history and variant on SARS-CoV-2 viral kinetics and infection rebound: A retrospective cohort study.

Background: The combined impact of immunity and SARS-CoV-2 variants on viral kinetics during infections has been unclear. Methods: We characterized 1,280 infections from the National Basketball Association occupational health cohort identified between June 2020 and January 2022 using serial RT-qPCR testing. Logistic regression and semi-mechanistic viral RNA kinetics models were used to quantify the effect of age, variant, symptom status, infection history, vaccination status and antibody titer to the founder SARS-CoV-2 strain on the duration of potential infectiousness and overall viral kinetics. The frequency of viral rebounds was quantified under multiple cycle threshold (Ct) value-based definitions. Results: Among individuals detected partway through their infection, 51.0% (95% credible interval [CrI]: 48.3-53.6%) remained potentially infectious (Ct <30) 5 days post detection, with small differences across variants and vaccination status. Only seven viral rebounds (0.7%; N=999) were observed, with rebound defined as 3+days with Ct <30 following an initial clearance of 3+days with Ct ≥30. High antibody titers against the founder SARS-CoV-2 strain predicted lower peak viral loads and shorter durations of infection. Among Omicron BA.1 infections, boosted individuals had lower pre-booster antibody titers and longer clearance times than non-boosted individuals. Conclusions: SARS-CoV-2 viral kinetics are partly determined by immunity and variant but dominated by individual-level variation. Since booster vaccination protects against infection, longer clearance times for BA.1-infected, boosted individuals may reflect a less effective immune response, more common in older individuals, that increases infection risk and reduces viral RNA clearance rate. The shifting landscape of viral kinetics underscores the need for continued monitoring to optimize isolation policies and to contextualize the health impacts of therapeutics and vaccines. Funding: Supported in part by CDC contract #200-2016-91779, a sponsored research agreement to Yale University from the National Basketball Association contract #21-003529, and the National Basketball Players Association.

Feasibility of single question mental health surveillance in chronic disease.

OBJECTIVE: To determine the (1) feasibility and acceptability of administering single question mental health surveillance to carers of children with chronic disease in the inpatient setting and (2) sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of this question to detect 'at risk' children compared with the Strengths and Difficulties Questionnaire (SDQ). DESIGN: Cross-sectional pilot SETTING: Day Medical Unit of a tertiary paediatric hospital, 1 April 2021-31 July 2021. PATIENTS: Carers of children aged 2-17 years with chronic medical conditions. INTERVENTIONS: Caregivers were asked to respond to 'Thinking about your child's mental health over the past 4 weeks, are they thriving/coping/struggling/always overwhelmed?' during the admission process. All carers and children 11-17 years were invited to complete the SDQ. MAIN OUTCOME MEASURES: Feasibility and acceptability were determined by nursing feedback. Sensitivity, specificity, PPV and NPV were determined by comparing question responses with clinical cut-points on the SDQ. RESULTS: 213 carers responded to the question. Nurses reported that the question was easy (12/14) or moderately easy (2/14) to use and was 'easily understood' (6/14) or 'understood after some explanation' (8/14) for most carers. The question demonstrated a high specificity (0.98)/PPV (0.87) but low sensitivity (0.2) when thriving/coping were considered together whereas when thriving was compared with all other responses the sensitivity increased to 0.7. CONCLUSIONS: Single question mental health surveillance appears acceptable to carers and nursing staff and has a high level of specificity for children who are 'struggling' or 'always overwhelmed' versus the SDQ screening measure.

Molecular architecture of the human caveolin-1 complex.

Membrane-sculpting proteins shape the morphology of cell membranes and facilitate remodeling in response to physiological and environmental cues. Complexes of the monotopic membrane protein caveolin function as essential curvature-generating components of caveolae, flask-shaped invaginations that sense and respond to plasma membrane tension. However, the structural basis for caveolin's membrane remodeling activity is currently unknown. Here, we show that, using cryo-electron microscopy, the human caveolin-1 complex is composed of 11 protomers organized into a tightly packed disc with a flat membrane-embedded surface. The structural insights suggest a previously unrecognized mechanism for how membrane-sculpting proteins interact with membranes and reveal how key regions of caveolin-1, including its scaffolding, oligomerization, and intramembrane domains, contribute to its function.

Herpes Simplex Virus Glycoprotein B Mutations Define Structural Sites in Domain I, the Membrane Proximal Region, and the Cytodomain That Regulate Entry.

The viral fusion protein glycoprotein B (gB) is conserved in all herpesviruses and is essential for virus entry. During entry, gB fuses viral and host cell membranes by refolding from a prefusion to a postfusion form. We previously introduced three structure-based mutations (gB-I671A/H681A/F683A) into the domain V arm of the gB ectodomain that resulted in reduced cell-cell fusion. A virus carrying these three mutations (called gB3A) displayed a small-plaque phenotype and remarkably delayed entry into cells. To identify mutations that could counteract this phenotype, we serially passaged the gB3A virus and selected for revertant viruses with increased plaque sizes. Genomic sequencing revealed that the revertant viruses had second-site mutations in gB, including E187A, M742T, and S383F/G645R/V705I/V880G. Using expression constructs encoding these mutations, only gB-V880G was shown to enhance cell-cell fusion. In contrast, all of the revertant viruses showed enhanced entry kinetics, underscoring the fact that cell-cell fusion and virus-cell fusion are different. The results indicate that mutations in three different regions of gB (domain I, the membrane proximal region, and the cytoplasmic tail domain) can counteract the slow-entry phenotype of gB3A virus. Mapping these compensatory mutations to prefusion and postfusion structural models suggests sites of intramolecular functional interactions with the gB domain V arm that may contribute to the gB fusion function. IMPORTANCE The nine human herpesviruses are ubiquitous and cause a range of diseases in humans. Glycoprotein B (gB) is an essential viral fusion protein that is conserved in all herpesviruses. During host cell entry, gB mediates virus-cell membrane fusion by undergoing a conformational change. Structural models for the prefusion and postfusion forms of gB exist, but the details of how the protein converts from one to the other are unclear. We previously introduced structure-based mutations into gB that inhibited virus entry and fusion. By passaging this entry-deficient virus over time, we selected second-site mutations that partially restore virus entry. The locations of these mutations suggest regulatory sites that contribute to fusion and gB refolding during entry. gB is a target of neutralizing antibodies, and defining how gB refolds during entry could provide a basis for the development of fusion inhibitors for future research or clinical use.

The Role of Mcl-1 in Embryonic Neural Precursor Cell Apoptosis.

Myeloid cell leukemia-1 (Mcl-1), an anti-apoptotic Bcl-2 protein, regulates neural precursor cell (NPC) survival in both the developing and adult mammalian nervous system. It is unclear when during the neurogenic period Mcl-1 becomes necessary for NPC survival and whether Bax is the sole pro-apoptotic target of Mcl-1. To address these questions, we used the nervous system-specific Nestin-Cre Mcl-1 conditional knockout mouse line (Mcl-1 CKO) to assess the anti-apoptotic role of Mcl-1 in developmental neurogenesis. Loss of Mcl-1 resulted in a wave of apoptosis beginning in the brainstem and cervical spinal cord at embryonic day 9.5 (E9.5) and in the forebrain at E10.5. Apoptosis was first observed ventrally in each region and spread dorsally over time. Within the spinal cord, apoptosis also spread in a rostral to caudal direction following the path of differentiation. Breeding the Mcl-1 CKO mouse with the Bax null mouse rescued the majority of NPC from apoptosis except in the dorsomedial brainstem and ventral thoracic spinal cord where only 50% were rescued. This demonstrates that Mcl-1 promotes NPC survival primarily by inhibiting the activation of Bax, but that Bax is not the sole pro-apoptotic target of Mcl-1 during embryonic neurogenesis. Interestingly, although co-deletion of Bax rescued the majority of NPC apoptosis, it resulted in embryonic lethality at E13, whereas conditional deletion of both Mcl-1 and Bax rescued embryonic lethality. In summary, this study demonstrates the widespread dependency on Mcl-1 during nervous system development.

HLA-associated preadaptation in HIV Vif is associated with higher set point viral load and faster CD4+ decline in Zambian transmission pairs.

OBJECTIVE S: We investigated the relationship between human leukocyte antigen (HLA)-associated preadaptation for the entire subtype C HIV-1 proteome of the transmitted founder virus and subsequent HIV-1 disease progression in a cohort of heterosexual linked transmission pairs in Zambia. DESIGN: An adaptation model was used to calculate an adaptation score for each virus-HLA combination in order to quantify the degree of preadaptation of the transmitted virus to the linked recipient's HLA alleles. These scores were then assessed for their relationship to viral load and longitudinal CD4+ decline in the recipient. METHODS: Viral RNA was extracted from the plasma of the donor partner and the linked recipient near the time of transmission, as well as longitudinally from the linked recipient. Viral adaptation scores were calculated for each individual and each protein in the subtype C HIV-1 proteome. RESULTS: The majority of HLA-associated sites were located in Gag, Pol and Nef; however, proportional to protein length, the accessory and regulatory proteins contained a relatively high proportion of HLA-associated sites. Over the course of infection, HLA-mediated immune adaptation increased for all proteins except Vpu and gp120. Preadaptation was positively associated with higher early set point viral load and faster CD4+ decline. When examined by protein, preadaptation in Pol and Vif were statistically significantly associated with these markers of disease progression. CONCLUSION: Adaptation in Pol had the greatest impact on viral control. Despite containing a large proportion of HLA-associated sites, Vif was the only regulatory or accessory protein for which preadaptation significantly correlated with disease progression.

Outcomes after successful fallopian tube recanalization: A single institution experience: Observational Retrospective study.

PURPOSE: To determine outcomes after successful fallopian tube recanalization (FTR) in women who suffer infertility with documented tubal occlusion on hysterosalpingogram. METHODS: A retrospective review of consecutive successful FTR procedures from January 2010 to December 2016 was performed. 53 women who had hysterosalpingogram confirmed unilateral or bilateral tubal occlusion from a single tertiary academic medical center and successful FTR were eligible for inclusion. 35 (66.0%) patients had follow up at 12 months after FTR, with 13 conceiving within 1 year of the procedure. Data was collected from the medical record. Complication, conception, and take-home-baby (THB) rates were recorded. The average age of patients was 32.3 years (range 26-42 years). All patients received peri- and post-procedure antibiotics. The study was conducted with institutional IRB approval. RESULTS: Average follow-up after FTR was 1335 days. All patients tolerated the procedure well with no immediate complications. One patient had a urinary tract infection a week after FTR. 13 (37.1%) became pregnant after FTR. Of these women, 2 had ectopic pregnancies and 2 patients had spontaneous abortions. The THB rate after FTR for all patients was 25.7%. The THB rate in women who became pregnant after FTR was 69.2%. Of those women who did not become pregnant after FTR, 19 (84.6%) went to assisted reproductive techniques, and of those, 8 (42.1%) became pregnant. CONCLUSION: Infertility affects 8.4% of U.S. women, with tubal disease a major causative factor. In our study, successful FTR led to pregnancy in over a third of the patients with the majority giving birth to healthy babies. Given the success of obtaining pregnancy in combination with a low complication rate, FTR is a viable option in women who suffer from tubal infertility.

Entry of Alphaherpesviruses.

Alphaherpesviruses are enveloped viruses that enter cells by fusing the viral membrane with a host cell membrane, either within an endocytic vesicle or at the plasma membrane. This entry event is mediated by a set of essential entry glycoproteins, including glycoprotein D (gD), gHgL, and gB. gHgL and gB are conserved among herpesviruses, but gD is unique to the alphaherpesviruses and is not encoded by all alphaherpesviruses. gD is a receptor-binding protein, the heterodimer gHgL serves as a fusion regulator, and gB is a class III viral fusion protein. Sequential interactions among these glycoproteins are thought to trigger the virus to fuse at the right place and time. Structural studies of these glycoproteins from multiple alphaherpesviruses has enabled the design and interpretation of functional studies. The structures of gD in a receptor- bound and in an unliganded form reveal a conformational change in the C terminus of the gD ectodomain upon receptor binding that may serve as a signal for fusion. By mapping neutralizing antibodies to the gHgL structures and constructing interspecies chimeric forms of gHgL, interaction sites for both gD and gB on gHgL have been proposed. A comparison of the post fusion structure of gB and an alternative conformation of gB visualized using cryo- electron tomography suggests that gB undergoes substantial refolding to execute membrane fusion. Although these structures have provided excellent insights into the entry mechanism, many questions remain about how these viruses coordinate the interactions and conformational changes required for entry.

The structural basis of herpesvirus entry.

Herpesviruses are ubiquitous, double-stranded DNA, enveloped viruses that establish lifelong infections and cause a range of diseases. Entry into host cells requires binding of the virus to specific receptors, followed by the coordinated action of multiple viral entry glycoproteins to trigger membrane fusion. Although the core fusion machinery is conserved for all herpesviruses, each species uses distinct receptors and receptor-binding glycoproteins. Structural studies of the prototypical herpesviruses herpes simplex virus 1 (HSV-1), HSV-2, human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV) entry glycoproteins have defined the interaction sites for glycoprotein complexes and receptors, and have revealed conformational changes that occur on receptor binding. Recent crystallography and electron microscopy studies have refined our model of herpesvirus entry into cells, clarifying both the conserved features and the unique features. In this Review, we discuss recent insights into herpesvirus entry by analysing the structures of entry glycoproteins, including the diverse receptor-binding glycoproteins (HSV-1 glycoprotein D (gD), EBV glycoprotein 42 (gp42) and HCMV gH-gL-gO trimer and gH-gL-UL128-UL130-UL131A pentamer), as well gH-gL and the fusion protein gB, which are conserved in all herpesviruses.