Real-World Effectiveness of BNT162b2 Against Infection and Severe Diseases in Children and Adolescents

BACKGROUND

The efficacy of the BNT162b2 vaccine in pediatrics was assessed by randomized trials before the Omicron variant's emergence. The long-term durability of vaccine protection in this population during the Omicron period remains limited.

OBJECTIVE

To assess the effectiveness of BNT162b2 in preventing infection and severe diseases with various strains of the SARS-CoV-2 virus in previously uninfected children and adolescents.

DESIGN

Comparative effectiveness research accounting for underreported vaccination in 3 study cohorts: adolescents (12 to 20 years) during the Delta phase and children (5 to 11 years) and adolescents (12 to 20 years) during the Omicron phase.

SETTING

A national collaboration of pediatric health systems (PEDSnet).

PARTICIPANTS

77 392 adolescents (45 007 vaccinated) during the Delta phase and 111 539 children (50 398 vaccinated) and 56 080 adolescents (21 180 vaccinated) during the Omicron phase.

INTERVENTION

First dose of the BNT162b2 vaccine versus no receipt of COVID-19 vaccine.

MEASUREMENTS

Outcomes of interest include documented infection, COVID-19 illness severity, admission to an intensive care unit (ICU), and cardiac complications. The effectiveness was reported as (1-relative risk)*100, with confounders balanced via propensity score stratification.

RESULTS

During the Delta period, the estimated effectiveness of the BNT162b2 vaccine was 98.4% (95% CI, 98.1% to 98.7%) against documented infection among adolescents, with no statistically significant waning after receipt of the first dose. An analysis of cardiac complications did not suggest a statistically significant difference between vaccinated and unvaccinated groups. During the Omicron period, the effectiveness against documented infection among children was estimated to be 74.3% (CI, 72.2% to 76.2%). Higher levels of effectiveness were seen against moderate or severe COVID-19 (75.5% [CI, 69.0% to 81.0%]) and ICU admission with COVID-19 (84.9% [CI, 64.8% to 93.5%]). Among adolescents, the effectiveness against documented Omicron infection was 85.5% (CI, 83.8% to 87.1%), with 84.8% (CI, 77.3% to 89.9%) against moderate or severe COVID-19, and 91.5% (CI, 69.5% to 97.6%) against ICU admission with COVID-19. The effectiveness of the BNT162b2 vaccine against the Omicron variant declined 4 months after the first dose and then stabilized. The analysis showed a lower risk for cardiac complications in the vaccinated group during the Omicron variant period.

LIMITATION

Observational study design and potentially undocumented infection.

CONCLUSION

This study suggests that BNT162b2 was effective for various COVID-19-related outcomes in children and adolescents during the Delta and Omicron periods, and there is some evidence of waning effectiveness over time.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Researching COVID to enhance recovery (RECOVER) tissue pathology study protocol: Rationale, objectives, and design

IMPORTANCE

SARS-CoV-2 infection can result in ongoing, relapsing, or new symptoms or organ dysfunction after the acute phase of infection, termed Post-Acute Sequelae of SARS-CoV-2 (PASC), or long COVID. The characteristics, prevalence, trajectory and mechanisms of PASC are poorly understood. The objectives of the Researching COVID to Enhance Recovery (RECOVER) tissue pathology study (RECOVER-Pathology) are to: (1) characterize prevalence and types of organ injury/disease and pathology occurring with PASC; (2) characterize the association of pathologic findings with clinical and other characteristics; (3) define the pathophysiology and mechanisms of PASC, and possible mediation via viral persistence; and (4) establish a post-mortem tissue biobank and post-mortem brain imaging biorepository.

METHODS

RECOVER-Pathology is a cross-sectional study of decedents dying at least 15 days following initial SARS-CoV-2 infection. Eligible decedents must meet WHO criteria for suspected, probable, or confirmed infection and must be aged 18 years or more at the time of death. Enrollment occurs at 7 sites in four U.S. states and Washington, DC. Comprehensive autopsies are conducted according to a standardized protocol within 24 hours of death; tissue samples are sent to the PASC Biorepository for later analyses. Data on clinical history are collected from the medical records and/or next of kin. The primary study outcomes include an array of pathologic features organized by organ system. Causal inference methods will be employed to investigate associations between risk factors and pathologic outcomes.

DISCUSSION

RECOVER-Pathology is the largest autopsy study addressing PASC among US adults. Results of this study are intended to elucidate mechanisms of organ injury and disease and enhance our understanding of the pathophysiology of PASC.

Researching COVID to enhance recovery (RECOVER) pregnancy study: Rationale, objectives and design

IMPORTANCE

Pregnancy induces unique physiologic changes to the immune response and hormonal changes leading to plausible differences in the risk of developing post-acute sequelae of SARS-CoV-2 (PASC), or Long COVID. Exposure to SARS-CoV-2 during pregnancy may also have long-term ramifications for exposed offspring, and it is critical to evaluate the health outcomes of exposed children. The National Institutes of Health (NIH) Researching COVID to Enhance Recovery (RECOVER) Multi-site Observational Study of PASC aims to evaluate the long-term sequelae of SARS-CoV-2 infection in various populations. RECOVER-Pregnancy was designed specifically to address long-term outcomes in maternal-child dyads.

METHODS

RECOVER-Pregnancy cohort is a combined prospective and retrospective cohort that proposes to enroll 2,300 individuals with a pregnancy during the COVID-19 pandemic and their offspring exposed and unexposed in utero, including single and multiple gestations. Enrollment will occur both in person at 27 sites through the Eunice Kennedy Shriver National Institutes of Health Maternal-Fetal Medicine Units Network and remotely through national recruitment by the study team at the University of California San Francisco (UCSF). Adults with and without SARS-CoV-2 infection during pregnancy are eligible for enrollment in the pregnancy cohort and will follow the protocol for RECOVER-Adult including validated screening tools, laboratory analyses and symptom questionnaires followed by more in-depth phenotyping of PASC on a subset of the overall cohort. Offspring exposed and unexposed in utero to SARS-CoV-2 maternal infection will undergo screening tests for neurodevelopment and other health outcomes at 12, 18, 24, 36 and 48 months of age. Blood specimens will be collected at 24 months of age for SARS-CoV-2 antibody testing, storage and anticipated later analyses proposed by RECOVER and other investigators.

DISCUSSION

RECOVER-Pregnancy will address whether having SARS-CoV-2 during pregnancy modifies the risk factors, prevalence, and phenotype of PASC. The pregnancy cohort will also establish whether there are increased risks of adverse long-term outcomes among children exposed in utero.

CLINICAL TRIALS.GOV IDENTIFIER

Clinical Trial Registration: http://www.clinicaltrials.gov. Unique identifier: NCT05172011.

Real-world Effectiveness of BNT162b2 Against Infection and Severe Diseases in Children and Adolescents

Background

The efficacy of the BNT162b2 vaccine in pediatrics was assessed by randomized trials before the Omicron variant's emergence. The long-term durability of vaccine protection in this population during the Omicron period remains limited.

Objective

To assess the effectiveness of BNT162b2 in preventing infection and severe diseases with various strains of the SARS-CoV-2 virus in previously uninfected children and adolescents.

Design

Comparative effectiveness research accounting for underreported vaccination in three study cohorts: adolescents (12 to 20 years) during the Delta phase, children (5 to 11 years) and adolescents (12 to 20 years) during the Omicron phase.

Setting

A national collaboration of pediatric health systems (PEDSnet).

Participants

77,392 adolescents (45,007 vaccinated) in the Delta phase, 111,539 children (50,398 vaccinated) and 56,080 adolescents (21,180 vaccinated) in the Omicron period.

Exposures

First dose of the BNT162b2 vaccine vs. no receipt of COVID-19 vaccine.

Measurements

Outcomes of interest include documented infection, COVID-19 illness severity, admission to an intensive care unit (ICU), and cardiac complications. The effectiveness was reported as (1-relative risk)*100% with confounders balanced via propensity score stratification.

Results

During the Delta period, the estimated effectiveness of BNT162b2 vaccine was 98.4% (95% CI, 98.1 to 98.7) against documented infection among adolescents, with no significant waning after receipt of the first dose. An analysis of cardiac complications did not find an increased risk after vaccination. During the Omicron period, the effectiveness against documented infection among children was estimated to be 74.3% (95% CI, 72.2 to 76.2). Higher levels of effectiveness were observed against moderate or severe COVID-19 (75.5%, 95% CI, 69.0 to 81.0) and ICU admission with COVID-19 (84.9%, 95% CI, 64.8 to 93.5). Among adolescents, the effectiveness against documented Omicron infection was 85.5% (95% CI, 83.8 to 87.1), with 84.8% (95% CI, 77.3 to 89.9) against moderate or severe COVID-19, and 91.5% (95% CI, 69.5 to 97.6)) against ICU admission with COVID-19. The effectiveness of the BNT162b2 vaccine against the Omicron variant declined after 4 months following the first dose and then stabilized. The analysis revealed a lower risk of cardiac complications in the vaccinated group during the Omicron variant period.

Limitations

Observational study design and potentially undocumented infection.

Conclusions

Our study suggests that BNT162b2 was effective for various COVID-19-related outcomes in children and adolescents during the Delta and Omicron periods, and there is some evidence of waning effectiveness over time.

Primary Funding Source

National Institutes of Health.

Researching COVID to Enhance Recovery (RECOVER) adult study protocol: Rationale, objectives, and design

IMPORTANCE

SARS-CoV-2 infection can result in ongoing, relapsing, or new symptoms or other health effects after the acute phase of infection; termed post-acute sequelae of SARS-CoV-2 infection (PASC), or long COVID. The characteristics, prevalence, trajectory and mechanisms of PASC are ill-defined. The objectives of the Researching COVID to Enhance Recovery (RECOVER) Multi-site Observational Study of PASC in Adults (RECOVER-Adult) are to: (1) characterize PASC prevalence; (2) characterize the symptoms, organ dysfunction, natural history, and distinct phenotypes of PASC; (3) identify demographic, social and clinical risk factors for PASC onset and recovery; and (4) define the biological mechanisms underlying PASC pathogenesis.

METHODS

RECOVER-Adult is a combined prospective/retrospective cohort currently planned to enroll 14,880 adults aged ≥18 years. Eligible participants either must meet WHO criteria for suspected, probable, or confirmed infection; or must have evidence of no prior infection. Recruitment occurs at 86 sites in 33 U.S. states, Washington, DC and Puerto Rico, via facility- and community-based outreach. Participants complete quarterly questionnaires about symptoms, social determinants, vaccination status, and interim SARS-CoV-2 infections. In addition, participants contribute biospecimens and undergo physical and laboratory examinations at approximately 0, 90 and 180 days from infection or negative test date, and yearly thereafter. Some participants undergo additional testing based on specific criteria or random sampling. Patient representatives provide input on all study processes. The primary study outcome is onset of PASC, measured by signs and symptoms. A paradigm for identifying PASC cases will be defined and updated using supervised and unsupervised learning approaches with cross-validation. Logistic regression and proportional hazards regression will be conducted to investigate associations between risk factors, onset, and resolution of PASC symptoms.

DISCUSSION

RECOVER-Adult is the first national, prospective, longitudinal cohort of PASC among US adults. Results of this study are intended to inform public health, spur clinical trials, and expand treatment options.

REGISTRATION

NCT05172024.

Researching COVID to enhance recovery (RECOVER) pregnancy study: Rationale, objectives and design

Importance

Pregnancy induces unique physiologic changes to the immune response and hormonal changes leading to plausible differences in the risk of developing post-acute sequelae of SARS-CoV-2 (PASC), or Long COVID. Exposure to SARS-CoV-2 during pregnancy may also have long-term ramifications for exposed offspring, and it is critical to evaluate the health outcomes of exposed children. The National Institutes of Health (NIH) Researching COVID to Enhance Recovery (RECOVER) Multi-site Observational Study of PASC aims to evaluate the long-term sequelae of SARS-CoV-2 infection in various populations. RECOVER- Pregnancy was designed specifically to address long-term outcomes in maternal-child dyads.

Methods

RECOVER-Pregnancy cohort is a combined prospective and retrospective cohort that proposes to enroll 2,300 individuals with a pregnancy during the COVID-19 pandemic and their offspring exposed and unexposed in utero, including single and multiple gestations. Enrollment will occur both in person at 27 sites through the Eunice Kennedy Shriver National Institutes of Health Maternal-Fetal Medicine Units Network and remotely through national recruitment by the study team at the University of California San Francisco (UCSF). Adults with and without SARS-CoV-2 infection during pregnancy are eligible for enrollment in the pregnancy cohort and will follow the protocol for RECOVER-Adult including validated screening tools, laboratory analyses and symptom questionnaires followed by more in-depth phenotyping of PASC on a subset of the overall cohort. Offspring exposed and unexposed in utero to SARS-CoV-2 maternal infection will undergo screening tests for neurodevelopment and other health outcomes at 12, 18, 24, 36 and 48 months of age. Blood specimens will be collected at 24 months of age for SARS-CoV-2 antibody testing, storage and anticipated later analyses proposed by RECOVER and other investigators.

Discussion

RECOVER-Pregnancy will address whether having SARS-CoV-2 during pregnancy modifies the risk factors, prevalence, and phenotype of PASC. The pregnancy cohort will also establish whether there are increased risks of adverse long-term outcomes among children exposed in utero.

Registration

NCT05172024.

Ultrastructural localization of cannabinoid CB1 and mGluR5 receptors in the prefrontal cortex and amygdala

Stimulation of the postsynaptic metabotropic glutamate receptor mGluR5 triggers retrograde signaling of endocannabinoids that activate presynaptic cannabinoid CB1 receptors on juxtaposing axon terminals. To better understand the synaptic structure that supports mGluR5 mediation of CB1 activation in the prefrontal cortex (PFC) and basolateral amygdala (BLA), we examined electron microscopic dual immunolabeling of these receptors in the prelimbic PFC (prPFC) and BLA of adult male rats. CB1 immunoreactivity was detected in axon terminals that were typically large, complex, and contained dense-core and clear synaptic vesicles. Of terminals forming discernible synaptic specializations, 95% were symmetric inhibitory-type in the prPFC and 90% were inhibitory in the BLA. CB1-immunoreactive terminals frequently contacted dendrites containing mGluR5 adjacent to unlabeled terminals forming excitatory-type synapses. Because most CB1-containing terminals form inhibitory-type synapses, the unlabeled axon terminals forming asymmetric synapses are the likely source of the mGluR5 ligand glutamate. In the prPFC, serial section analysis revealed that GABAergic CB1-containing axon terminals targeted dendrites adjacent to glutamatergic axon terminals, often near dendritic bifurcations. These observations provide ultrastructural evidence that cortical CB1 receptors are strategically positioned for integration of synaptic signaling in response to stimulation of postsynaptic mGluR5 receptors and facilitation of heterosynaptic communication between multiple neurons.

Adolescent isolation rearing produces a prepulse inhibition deficit correlated with expression of the NMDA GluN1 subunit in the nucleus accumbens

Adolescence is a transition period during which social interaction is necessary for normal brain and behavior development. Severely abnormal social interactions during adolescence can increase the incidence of lifelong psychiatric disease. Decreased prepulse inhibition (PPI) is a quantifiable hallmark of some psychiatric illnesses in humans and can be elicited in rodents by isolation rearing throughout the adolescent transition period. PPI is a measure of sensorimotor gating in which the nucleus accumbens (Acb) is crucially involved. The Acb is comprised of core and shell subregions, which receive convergent dopaminergic and glutamatergic inputs. To gain insight into the neurobiological correlates of adolescent adversity, we conducted electron microscopic immunolabeling of dopamine D1 receptors (D1Rs) and the GluN1 subunit of glutamate NMDA receptors in the Acb of isolation-reared (IR) adult male rats. In all animals, GluN1 was primarily located in dendritic profiles, many of which also contained D1Rs. GluN1 was also observed in perisynaptic glia and axon terminals. In IR rats compared with group-reared controls, GluN1 density was selectively decreased in D1R-containing dendrites of the Acb core. Across all animals, dendritic GluN1 density correlated with average percent PPI, implicating endogenous expression of NMDA receptors of the Acb as a possible substrate of the PPI response. These results suggest that adolescent isolation dampens NMDA-mediated excitation in direct (D1R-containing) output neurons of the Acb, and that these changes influence the operational measure of PPI.

Altered dendritic distribution of dopamine D2 receptors and reduction in mitochondrial number in parvalbumin-containing interneurons in the medial prefrontal cortex of cannabinoid-1 (CB1) receptor knockout mice

The prelimbic prefrontal cortex (PL) is a brain region integral to complex behaviors that are highly influenced by cannabinoids and by dopamine D2 receptor (D2R)-mediated regulation of fast-firing parvalbumin-containing interneurons. We have recently shown that constitutive deletion of the cannabinoid-1 receptor (CB1R) greatly reduces parvalbumin levels in these neurons. The effects of CB1R deletion on PL parvalbumin interneurons may be ascribed to loss of CB1R-mediated retrograde signaling on mesocortical dopamine transmission, and, in turn, altered expression and/or subcellular distribution of D2R in the PL. Furthermore, diminished parvalbumin expression could indicate metabolic changes in fast-firing interneurons that may be reflected in changes in mitochondrial density in this population. We therefore comparatively examined electron microscopic dual labeling of D2R and parvalbumin in CB1 (-/-) and CB1 (+/+) mice to test the hypothesis that absence of CB1R produces changes in D2R localization and mitochondrial distribution in parvalbumin-containing interneurons of the PL. CB1 (-/-) mice had a significantly lower density of cytoplasmic D2R-immunogold particles in medium parvalbumin-labeled dendrites and a concomitant increase in the density of these particles in small dendrites. These dendrites received both excitatory and inhibitory-type synapses from unlabeled terminals and contained many mitochondria, whose numbers were significantly reduced in CB1 (-/-) mice. Non-parvalbumin dendrites showed no between-group differences in either D2R distribution or mitochondrial number. These results suggest that cannabinoid signaling provides an important determinant of dendritic D2 receptor distribution and mitochondrial availability in fast-spiking interneurons.

The impact of adolescent social isolation on dopamine D2 and cannabinoid CB1 receptors in the adult rat prefrontal cortex

Adolescent experiences of social deprivation result in profound and enduring perturbations in adult behavior, including impaired sensorimotor gating. The behavioral deficits induced by adolescent social isolation in rats can be ameliorated by antipsychotic drugs blocking dopamine D2 receptors in the prefrontal cortex (PFC) or by chronic administration of a cannabinoid CB1 receptor antagonist. The patterning and abundance of D2 receptors in the PFC evolves concurrently with CB1 receptors through the period of adolescence. This evidence suggests that mature expression and/or surface distribution of D2 and CB1 receptors may be influenced by the adolescent social environment. We tested this hypothesis using electron microscopic immunolabeling to compare the distribution of CB1 and D2 receptors in the PFC of adult male Sprague-Dawley rats that were isolated or socially reared throughout the adolescent transition period. Prepulse inhibition (PPI) of acoustic startle was assessed as a measure of sensorimotor gating. Social isolation reduced PPI and selectively decreased dendritic D2 immunogold labeling in the PFC. However, the decrease was only evident in dendrites that were not contacted by axon terminals containing CB1. There was no apparent change in the expression of CB1 or D2 receptors in presynaptic terminals. The D2 deficit therefore may be tempered by local CB1-mediated retrograde signaling. This suggests a biological mechanism whereby the adolescent social environment can persistently influence cortical dopaminergic activity and resultant behavior.

Cannabinoid modulation of the dopaminergic circuitry: implications for limbic and striatal output

Cannabinoid modulation of dopaminergic transmission is suggested by the ability of delta9-tetrahydrocanabinoid to affect motor and motivated behaviors in a manner similar to that produced by pharmacological manipulation of the nigrostriatal and mesocorticolimbic dopamine systems. These behavioral effects as well as analogous effects of endocannabinoids are largely mediated through the cannabinoid type 1 receptor (CB1R). This receptor is located within the substantia nigra and ventral tegmental area, which respectively house the somata of nigrostriatal and mesocorticolimbic dopaminergic neurons. The CB1R is also abundantly expressed in brain regions targeted by the efferent terminals of these dopaminergic neurons. In this review we present the accumulating anatomical and electrophysiological evidence indicating that in each of these systems cannabinoids modulate dopamine transmission largely if not exclusively through indirect mechanisms. The summarized mechanisms include presynaptic release of amino acid transmitters onto midbrain dopamine neurons and onto both cortical and striatal neurons that express dopamine D1-like or D2-like receptors functionally affiliated with the CB1 receptor. The review concludes with a consideration of the psychiatric and neurological implications of cannabinoid modulation of dopamine transmission within these networks.

Quinpirole elicits differential in vivo changes in the pre- and postsynaptic distributions of dopamine D₂ receptors in mouse striatum: relation to cannabinoid-1 (CB₁) receptor targeting

RATIONALE

The nucleus accumbens (Acb) shell and caudate-putamen nucleus (CPu) are respectively implicated in the motivational and motor effects of dopamine, which are mediated in part through dopamine D₂-like receptors (D₂Rs) and modulated by activation of the cannabinoid-1 receptor (CB₁R). The dopamine D(₂/D3) receptor agonist, quinpirole elicits internalization of D₂Rs in isolated cells; however, dendritic and axonal targeting of D₂Rs may be highly influenced by circuit-dependent changes in vivo and potentially influenced by endogenous CB₁R activation.

OBJECTIVE

We sought to determine whether quinpirole alters the surface/cytoplasmic partitioning of D₂Rs in striatal neurons in vivo.

METHODS

To address this question, we examined the electron microscopic immunolabeling of D₂ and CB₁ receptors in the Acb shell and CPu of male mice at 1 h following a single subcutaneous injection of quinpirole (0.5 mg/kg) or saline, a time point when quinpirole reduced locomotor activity.

RESULTS

Many neuronal profiles throughout the striatum of both treatment groups expressed the D₂R and/or CB₁R. As compared with saline, quinpirole-injected mice showed a significant region-specific decrease in the plasmalemmal and increase in the cytoplasmic density of D₂R-immunogold particles in postsynaptic dendrites without CB₁R-immunolabeling in the Acb shell. However, quinpirole produced a significant increase in the plasmalemmal density of D₂R immunogold in CB₁R negative axons in both the Acb shell and CPu.

CONCLUSIONS

Our results provide in vivo evidence for agonist-induced D₂R trafficking that is inversely related to CB₁R distribution in postsynaptic neurons of Acb shell and in presynaptic axons in this region and in the CPu.

Acetylcholine α7 nicotinic and dopamine D2 receptors are targeted to many of the same postsynaptic dendrites and astrocytes in the rodent prefrontal cortex

The alpha-7 nicotinic acetylcholine receptor (α7nAChR) and the dopamine D(2) receptor (D(2) R) are both implicated in attentional processes and cognition, mediated in part through the prefrontal cortex (PFC). We examined the dual electron microscopic immunolabeling of α7nAChR and either D(2) R or the vesicular acetylcholine transporter (VAChT) in rodent PFC to assess convergent functional activation sites. Immunoreactivity (ir) for α7nAChR and/or D(2) R was seen in the same as well as separate neuronal and glial profiles. At least half of the dually labeled profiles were somata and dendrites, while most labeled axon terminals expressed only D(2) R-ir. The D(2) R-labeled terminals were without synaptic specializations or formed inhibitory or excitatory-type synapses with somatodendritic profiles, some of which expressed the α7nAChR and/or D(2) R. Astrocytic glial processes comprised the majority of nonsomatodendritic α7nAChR or α7nAChR and D(2) R-labeled profiles. Glial processes containing α7nAChR-ir were frequently located near VAChT-labeled terminals and also showed perisynaptic and perivascular associations. We conclude that in rodent PFC α7nACh and D(2) R activation can dually modulate (1) postsynaptic dendritic responses within the same or separate but synaptically linked neurons in which the D(2) R has the predominately presynaptic distribution, and (2) astrocytic signaling that may be crucial for synaptic transmission and functional hyperemia.

Decreased parvalbumin immunoreactivity in the cortex and striatum of mice lacking the CB1 receptor

Cortical and striatal regions of the brain contain high levels of the cannabinoid-1 (CB1) receptor, the central neuronal mediator of activity-dependent synaptic plasticity evoked by endocannabinoids. The expression levels of parvalbumin, a calcium-binding protein found in fast-spiking interneurons of both regions, may be controlled in part by synaptic activity during critical periods of development. However, there is currently no evidence that CB1 receptor expression affects parvalbumin levels in either cortical or striatal interneurons. To assess this possibility, we examined parvalbumin immunoreactivity in the dorsolateral striatum, primary motor cortex (M1), and prefrontal cortex (PFC) of CB1 knockout and wild-type C57/BL6 mice. Quantitative densitometry showed a significant decrease in parvalbumin immunoreactivity within individual neurons in each of these regions of CB1 knockout mice relative to controls. A significantly lower density (number of cells per unit area) of parvalbumin-labeled neurons was observed in the striatum, but not the cortical regions of CB1 knockout mice. These findings suggest that CB1 receptor deletion may elicit a compensatory mechanism for network homeostasis affecting parvalbumin-containing cortical and striatal interneurons.

ABCA1 and amphipathic apolipoproteins form high-affinity molecular complexes required for cholesterol efflux

Apolipoproteins, such as apolipoprotein A-I (apoA-I), can stimulate cholesterol efflux from cells expressing the ATP binding cassette transporter A1 (ABCA1). The nature of the molecular interaction between these cholesterol acceptors and ABCA1 is controversial, and models suggesting a direct protein-protein interaction or indirect association have been proposed. To explore this issue, we performed competition binding and chemical cross-linking assays using six amphipathic plasma proteins and an 18 amino acid amphipathic helical peptide. All seven proteins stimulated lipid efflux and inhibited the cross-linking of apoA-I to ABCA1. Cross-linking of apoA-I to ABCA1 was saturable and occurred at high affinity (Kd of 7.0 +/- 1.9 nM), as was cross-linking of apoA-II. After binding to ABCA1, apoA-I rapidly dissociated (half-life of 25 min) from the complex and was released back into the medium. A mutant form of ABCA1 (W590S) that avidly binds apoA-I but fails to promote cholesterol efflux released apoA-I with similar kinetics but without transfer of cholesterol to apoA-I. Thus, a high-affinity, saturable, protein-protein interaction occurs between ABCA1 and all of its amphipathic protein ligands. Dissociation of the complex leads to the cellular release of cholesterol and the apolipoprotein. However, dissociation is not dependent on cholesterol transfer, which is a clearly separable event, distinguishable by ABCA1 mutants.

Peroxisome proliferator-activated receptors in macrophage biology: friend or foe?

Peroxisome proliferator-activated receptor (PPAR)-gamma is a nuclear hormone receptor, with a well-established role in adipogenesis and glucose metabolism. Over the past 3 years several laboratories have reported that this protein can influence macrophage responses to a variety of inflammatory stimuli. The effect of PPAR-gamma activation on macrophage lipid uptake, cholesterol efflux, and cytokine production have all recently been examined in several in-vitro culture systems. In addition, PPAR-gamma ligands have been shown to influence atherosclerotic lesion formation in murine models of that disease. This review attempts to summarize and critically evaluate that work and its implications for the use of PPAR-gamma activators in understanding and treating the pathogenetic processes that contribute to atherosclerotic plaque formation.

Sexual abuse, alcohol and other drug use, and suicidal behaviors in homeless adolescents

Previous research has shown that homeless youth have high rates of suicidal ideation, sexual abuse, and abuse of alcohol and other drugs. However, little is known about how these rates differ by gender and ethnicity. Our objective was to describe patterns of sexual abuse, alcohol and other drug use, and indicators of suicidal behaviors in homeless adolescents and to determine gender and ethnic differences in these factors. We used secondary data analysis of data from surveys completed by 96 homeless youth whose average age was 17.9 years. Over 60% of the sample reported a history of sexual abuse; the majority were under the age of 12 years when they first tried alcohol, marijuana, and cocaine; 56.3% had injected drugs, and 46.9% had tried inhalants. During the past 12 months, 35.1% had seriously considered suicide and 12.3% had actually attempted suicide at least once. Significantly more Hispanics than Whites had considered suicide (chi 2 = 4.31, p = .038). A disproportionate number of Hispanics (95% of the sample) reported a history of sexual abuse. Participants with a history of sexual abuse were significantly more likely than those who did not have a history of sexual abuse to have used alcohol and/or marijuana (chi 2 = 9.93, p < .01) and to have considered suicide in the past 12 months (F = 14.93, p < .001). We found that sexual abuse history is greater in this sample than in the general population and is particularly prevalent among Hispanic/Latino subjects. As in other studies, sexual abuse was more common among females than among males. High prevalence of sexual abuse, alcohol and other drug use, and suicidal behaviors in this sample of homeless youth underscores the need to develop and test community-based interventions to improve their health status.

Grandparent parents. Intergenerational surrogate parenting

There is an increasing prevalence in the United States of intergenerational surrogate parenting. In fact, grandmother-headed households that include grandchildren without their parents are the fastest growing intergenerational surrogate family combination. This article reviews the intergenerational surrogate family phenomenon relative to its impact on the grandmothers' health and offers resources and implications for nursing.

Nurses in managed care roles

TNA and the Texas Department of Insurance collaborated on an integrated, education program that has provided benefits for all--graduate nursing students get an opportunity to learn about managed care issues and policies; TDI has gained the clinical expertise of the nursing profession in order to best evaluate quality of care.

ATP-binding cassette transporter A1 contains an NH2-terminal signal anchor sequence that translocates the protein's first hydrophilic domain to the exoplasmic space

Mutations in the ATP-binding cassette transporter A1 (ABCA1) transporter are associated with Tangier disease and a defect in cellular cholesterol efflux. The amino terminus of the ABCA1 transporter has two putative in-frame translation initiation sites, 60 amino acids apart. A cluster of hydrophobic amino acids form a potentially cleavable signal sequence in this 60-residue extension. We investigated the functional role of this extension and found that it was required for stable protein expression of transporter constructs containing any downstream transmembrane domains. The extension directed transporter translocation across the ER membrane with an orientation that resulted in glycosylation of amino acids immediately distal to the signal sequence. Neither the native signal sequence nor a green fluorescent protein tag, fused at the amino terminus, was cleaved from ABCA1. The green fluorescent protein fusion protein had efflux activity comparable with wild type ABCA1 and demonstrated a predominantly plasma membrane distribution in transfected cells. These data establish a requirement for the upstream 60 amino acids of ABCA1. This region contains an uncleaved signal anchor sequence that positions the amino terminus in a type II orientation leading to the extracellular presentation of an approximately 600-amino acid loop in which loss-of-function mutations cluster in Tangier disease patients.

The role of PPAR-gamma in macrophage differentiation and cholesterol uptake

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma), the transcription factor target of the anti-diabetic thiazolidinedione (TZD) drugs, is reported to mediate macrophage differentiation and inflammatory responses. Using PPAR-gamma-deficient stem cells, we demonstrate that PPAR-gamma is neither essential for myeloid development, nor for such mature macrophage functions as phagocytosis and inflammatory cytokine production. PPAR-gamma is required for basal expression of CD36, but not for expression of the other major scavenger receptor responsible for uptake of modified lipoproteins, SR-A. In wild-type macrophages, TZD treatment divergently regulated CD36 and class A macrophage-scavenger receptor expression and failed to induce significant cellular cholesterol accumulation, indicating that TZDs may not exacerbate macrophage foam-cell formation.

Functions of cell surface heparan sulfate proteoglycans

The heparan sulfate on the surface of all adherent cells modulates the actions of a large number of extracellular ligands. Members of both cell surface heparan sulfate proteoglycan families, the transmembrane syndecans and the glycosylphosphoinositide-linked glypicans, bind these ligands and enhance formation of their receptor-signaling complexes. These heparan sulfate proteoglycans also immobilize and regulate the turnover of ligands that act at the cell surface. The extracellular domains of these proteoglycans can be shed from the cell surface, generating soluble heparan sulfate proteoglycans that can inhibit interactions at the cell surface. Recent analyses of genetic defects in Drosophila melanogaster, mice, and humans confirm most of these activities in vivo and identify additional processes that involve cell surface heparan sulfate proteoglycans. This chapter focuses on the mechanisms underlying these activities and on the cellular functions that they regulate.

Lipopolysaccharide induces scavenger receptor A expression in mouse macrophages: a divergent response relative to human THP-1 monocyte/macrophages

Gene deletion studies indicate that the macrophage scavenger receptor A (SR-A) protects mice from LPS-induced endotoxemia. Paradoxically, cultured human monocyte-derived macrophages down-regulate SR-A expression when exposed to LPS. We found that human THP-1 monocyte/macrophages decrease SR-A expression in response to LPS independent of their differentiation status. In contrast, primary and elicited mouse peritoneal macrophages as well as the J774A.1 and RAW264.7 mouse macrophage lines increase SR-A expression in response to LPS. Exposure to LPS caused J774A.1 and RAW264.7 cells to increase SR-A transcripts by 3- and 5-fold, respectively. LPS caused a concomitant 3-fold increase in SR-A protein levels and increased cell membrane expression of the receptor. RAW264.7 cells increased SR-A transcript levels in response to LPS at concentrations as low as 1 ng/ml, and the response was saturated at 10 ng/ml. The LPS induction of SR-A transcripts required continual protein synthesis and began at 8 h, peaked by 16 h, and persisted for at least 48 h. LPS induction did not increase SR-A gene transcription or affect alternative transcript splicing, but mildly increased mature transcript stability and proceeded in the presence of actinomycin D. Finally, treatment of RAW264.7 cells with TNF-alpha did not induce SR-A transcript levels, indicating that a TNF-alpha autocrine/paracrine signaling mechanism alone is not sufficient to recapitulate the LPS induction of SR-A transcripts. The induction of SR-A expression by LPS-stimulated mouse macrophages is the opposite of the down-regulation of SR-A reported in human monocyte-derived macrophages and may have implications for the observed resistance mice show toward endotoxemia.

Syndecan-1 shedding is enhanced by LasA, a secreted virulence factor of Pseudomonas aeruginosa

Microbial pathogens frequently take advantage of host systems for their pathogenesis. Shedding of cell surface molecules as soluble extracellular domains (ectodomains) is one of the host responses activated during tissue injury. In this study, we examined whether pathogenic bacteria can modulate shedding of syndecan-1, the predominant syndecan of host epithelia. Our studies found that overnight culture supernatants of Pseudomonas aeruginosa and Staphylococcus aureus enhanced the shedding of syndecan-1 ectodomains, whereas culture supernatants of several other Gram-negative and Gram-positive bacteria had only low levels of activity. Because supernatants from all tested strains of P. aeruginosa (n = 9) enhanced syndecan-1 shedding by more than 4-fold above control levels, we focused our attention on this Gram-negative bacterium. Culture supernatants of P. aeruginosa increased shedding of syndecan-1 in both a concentration- and time-dependent manner, and augmented shedding by various host cells. A 20-kDa shedding enhancer was partially purified from the supernatant through ammonium sulfate precipitation and gel chromatography, and identified by N-terminal sequencing as LasA, a known P. aeruginosa virulence factor. LasA was subsequently determined to be a syndecan-1 shedding enhancer from the findings that (i) immunodepletion of LasA from the partially purified sample resulted in abrogation of its activity to enhance shedding and (ii) purified LasA increased shedding in a concentration-dependent manner. Our results also indicated that LasA enhances syndecan-1 shedding by activation of the host cell's shedding mechanism and not by direct interaction with syndecan-1 ectodomains. Enhanced syndecan-1 shedding may be a means by which pathogenic bacteria take advantage of a host mechanism to promote their pathogenesis.

Rab6 is phosphorylated in thrombin-activated platelets by a protein kinase C-dependent mechanism: effects on GTP/GDP binding and cellular distribution

In platelets and other secretory cells, protein kinase C (PKC) plays a role in exocytosis stimulated by physiological extracellular signals, although its linkage to the secretory machinery is poorly understood. We investigated whether Rab6, a GTP-binding protein that fractionates with platelet alpha-granules, may be involved in linking these processes. We found that Rab6 contains two PKC consensus phosphorylation sites that are evolutionarily conserved. In platelets metabolically labelled with [(32)P]P(i), Rab6 phosphorylation was induced by phorbol esters or by thrombin. This phosphorylation was blocked by a specific PKC inhibitor (Ro-31-8220), but not by a p38 mitogen-activated protein kinase inhibitor (PD-169316). Physiological stimulation of platelets caused a PKC-dependent translocation of Rab6 from platelet particulate fractions, nearly doubling the fraction of Rab6 in the cytosol. A human Rab6 isoform (Rab6C) that is preferentially expressed in human platelet RNA was cloned and its phosphorylation by PKC was characterized. Rab6C incorporated up to 2 mol of [(32)P]P(i) per mol of active protein. Rab6C bound GDP and GTP with K(d) values of 113+/-12 and 119+/-27 nM respectively, and hydrolysed GTP at a rate of 100+/-15 micromol of GTP/mol of Rab6C per min. PKC phosphorylation of Rab6C increased the affinity for GTP by 3-fold, although it had lesser effects on GDP (1.6-fold). Phosphorylation did not alter the GTPase activity. In summary, thrombin activation of platelets leads to PKC-dependent phosphorylation of Rab6 and a translocation of Rab6 to the cytosol. We suggest that PKC phosphorylation may be an important mechanism through which Rab functional interactions in vesicle trafficking and secretion can be altered in response to an external stimulus.

Human platelets contain SNARE proteins and a Sec1p homologue that interacts with syntaxin 4 and is phosphorylated after thrombin activation: implications for platelet secretion

In response to thrombin and other extracellular activators, platelets secrete molecules from large intracellular vesicles (granules) to initiate thrombosis. Little is known about the molecular machinery responsible for vesicle docking and secretion in platelets and the linkage of that machinery to cell activation. We found that platelet membranes contain a full complement of interacting proteins-VAMP, SNAP-25, and syntaxin 4-that are necessary for vesicle docking and fusion with the plasma membrane. Platelets also contain an uncharacterized homologue of the Sec1p family that appears to regulate vesicle docking through its binding with a cognate syntaxin. This platelet Sec1 protein (PSP) bound to syntaxin 4 and thereby excluded the binding of SNAP-25 with syntaxin 4, an interaction critical to vesicle docking. As predicted by its sequence, PSP was detected predominantly in the platelet cytosol and was phosphorylated in vitro by protein kinase C (PKC), a secretion-linked kinase, incorporating 0.87 +/- 0.11 mol of PO4 per mole of protein. PSP was also specifically phosphorylated in permeabilized platelets after cellular stimulation by phorbol esters or thrombin and this phosphorylation was blocked by the PKC inhibitor Ro-31-8220. Phosphorylation by PKC in vitro inhibited PSP from binding to syntaxin 4. Taken together, these studies indicate that platelets, like neurons and other cells capable of regulated secretion, contain a unique complement of interacting vesicle docking proteins and PSP, a putative regulator of vesicle docking. The PKC-dependent phosphorylation of PSP in activated platelets and its inhibitory effects on syntaxin 4 binding provide a novel functional link that may be important in coupling the processes of cell activation, intracellular signaling, and secretion.

Physiological degradation converts the soluble syndecan-1 ectodomain from an inhibitor to a potent activator of FGF-2

The activity of fibroblast growth factor 2 (FGF-2) is stringently controlled. Inactive in undisturbed tissues, it is activated during injury and is critical for tissue repair. We find that this control can be imposed by the soluble syndecan-1 ectodomain, a heparan sulfate proteoglycan shed from cell surfaces into wound fluids. The ectodomain potently inhibits heparin-mediated FGF-2 mitogenicity because of the poorly sulfated domains in its heparin sulfate chains. Degradation of these regions by platelet heparanase produces heparin-like heparin sulfate fragments that markedly activate FGF-2 mitogenicity and are found in wound fluids. These results establish a novel physiological control for FGF-2 and suggest new ways to modulate FGF activity.

Regulated shedding of syndecan-1 and -4 ectodomains by thrombin and growth factor receptor activation

The syndecan family of transmembrane heparan sulfate proteoglycans is abundant on the surface of all adherent mammalian cells. Syndecans bind and modify the action of various growth factors/cytokines, proteases/antiproteases, cell adhesion molecules, and extracellular matrix components. Syndecan expression is highly regulated during wound repair, a process orchestrated by many of these effectors. Each syndecan ectodomain is shed constitutively by cultured cells, but the mechanism and significance of this shedding are not understood. Therefore, we examined (i) whether physiological agents active during wound repair influence syndecan shedding, and (ii) whether wound fluids contain shed syndecan ectodomains. Using SVEC4-10 endothelial cells we find that certain proteases and growth factors accelerate shedding of the syndecan-1 and -4 ectodomains. Protease-accelerated shedding is completely inhibited by serum-containing media. Thrombin activity is duplicated by the 14-amino acid thrombin receptor agonist peptide that directly activates the thrombin receptor and is not inhibited by serum. Epidermal growth factor family members accelerate shedding but FGF-2, platelet-derived growth factor-AB, transforming growth factor-beta, tumor necrosis factor-alpha, and vascular endothelial cell growth factor 165 do not. Shed ectodomains are soluble, stable in the conditioned medium, have the same size core proteins regardless whether shed at a basal rate, or accelerated by thrombin or epidermal growth factor-family members and are found in acute human dermal wound fluids. Thus, shedding is accelerated by activation of at least two distinct receptor classes, G protein-coupled (thrombin) and protein tyrosine kinase (epidermal growth factor). Proteases and growth factors active during wound repair can accelerate syndecan shedding from cell surfaces. Regulated shedding of syndecans suggests physiological roles for the soluble proteoglycan ectodomains.

Integrin switching regulates normal trophoblast invasion

Cells invade extracellular matrices in a regulated manner at specific times and places during normal development. A dramatic example is trophoblast invasion of the uterine wall. Previous studies have shown that differentiation of trophoblasts to an invasive phenotype is accompanied by temporally and spatially regulated switching of their integrin repertoire. In the first trimester human placenta, alpha 6 integrins are restricted to cytotrophoblast (CTB) stem cells and downregulated in invasive CTBs, whereas alpha 5 beta 1 and alpha 1 beta 1 integrins are upregulated in differentiating and invasive CTBs. The goal of the present study was to determine whether these changes have functional consequences for CTB invasiveness. Using an in vitro invasion model, we determined first that aggregates of invading first trimester CTBs in vitro undergo the same pattern of integrin switching as was observed in situ, thereby validating the utility of the model. We then showed that antibody perturbation of interactions involving laminin or collagen type IV and their integrin alpha 1/beta 1 receptor inhibited invasion by CTBs, whereas perturbing interactions between fibronectin and the alpha 5/beta 1 fibronectin receptor accelerated invasion. Finally, we report that later gestation CTBs, which display greatly decreased invasive capacity, are also unable to upregulate alpha 1 beta 1 complexes, providing further evidence that this integrin is critical for CTB invasion. This gestational regulation is transcriptional. These data indicate that integrin switching observed during differentiation in situ has significant functional consequences for CTB invasion. The data suggest further that differentiating CTBs upregulate counterbalancing invasion-accelerating and invasion-restraining adhesion mechanisms. We propose that this contributes to regulating the depth of CTB invasion during normal implantation.

Efficient concerted integration of retrovirus-like DNA in vitro by avian myeloblastosis virus integrase

We report the efficient concerted integration of a linear virus-like DNA donor into a 2.8 kbp circular DNA target by integrase (IN) purified from avian myeloblastosis virus. The donor was 528 bp, contained recessed 3' OH ends, was 5' end labeled, and had a unique restriction site not found in the target. Analysis of concerted (full-site) and half-site integration events was accomplished by restriction enzyme analysis and agarose gel electrophoresis. The donor also contained the SupF gene that was used for genetic selection of individual full-site recombinants to determine the host duplication size. Two different pathways, involving either one donor or two donor molecules, were used to produce full-site recombinants. About 90% of the full-site recombinants were the result of using two donor molecules per target. These results imply that juxtapositioning an end from each of two donors by IN was more efficient than the juxtapositioning of two ends of a single donor for the full-site reaction. The formation of preintegration complexes containing integrase and donor on ice prior to the addition of target enhanced the full-site reaction. After a 30 min reaction at 37 degrees C, approximately 20-25% of all donor/target recombinants were the result of concerted integration events. The efficient production of full-site recombinants required Mg2+; Mn2+ was only efficient for the production of half-site recombinants. We suggest that these preintegration complexes can be used to investigate the relationships between the 3' OH trimming and strand transfer reactions.

Retroviral integration: in vitro host site selection by avian integrase

Viral integrase catalyzes the integration of the linear viral DNA genome into the chromatin of the infected host cell, an essential step in the life cycle of retroviruses. The reaction produces a characteristic small duplication of host sequences at the site of integration, implying that there is a close juxtaposition of the viral DNA ends during a concerted integration event. We have used an in vitro assay to measure the concerted integration of virus-like plasmid DNA into naked lambda DNA catalyzed by virion purified avian integrase. In contrast to in vivo avian integration, which has strong fidelity for a 6-bp duplication, purified avian integrase in the context of this assay produced a distribution of duplication sizes, with the 6-bp size dominating. The metal cofactor Mg2+ induced increased fidelity for the 6-bp duplication relative to that with Mn2+. The immediate sequence of the host site may also influence duplication size in that we found sites that sustained multiple independent integration events producing the same duplication size. Additionally, for each set of cloned integration sites (5, 6, and 7 bp), a unique but similar symmetrical pattern of G/C and A/T sequence biases was found. Using duplex oligonucleotides as target substrates, we tested the significance of the 6-bp G/C and A/T pattern for site selection. In the context of this assay, which is likely dominated by the integration of only one viral end, the 6-bp pattern was not preferred. Instead, integration was predominantly into the 3' ends of the oligonucleotides. The combined results of the lambda and oligonucleotide assays indicated that although host site selection has properties in common with recognition of the viral DNA termini, the nonrandom sequence preferences seen for host site selection were not identical to the sequence requirements for long terminal repeat recognition.

Targeted deletion of beta 1 integrins in F9 embryonal carcinoma cells affects morphological differentiation but not tissue-specific gene expression

The integrin superfamily of heterodimeric transmembrane adhesion receptors mediates many cell-cell and cell-matrix interactions whose functions are believed to be critical for normal morphogenesis and differentiation. By eliminating the beta 1 integrin gene through homologous recombination, we have assessed the role of the beta 1 integrin family in the F9 embryonal carcinoma model for endodermal differentiation. F9 cells were unexpectedly found to maintain three copies of the beta 1 gene and complete elimination required three sequential rounds of targeting to generate triple knockout lines (beta 1 TKO). Elimination of the beta 1 integrin family of adhesion receptors from F9 cells resulted in reduced adhesion to fibronectin, laminin and collagen, but strongly enhanced adhesion to vitronectin. The absence of beta 1 integrins did not promote significant compensatory upregulation of either beta 3 or beta 5 subunits, both of which are known to act as vitronectin receptors when associated with alpha v. The loss of beta 1 integrins severely affected morphological differentiation when the beta 1-deficient cells were induced to differentiate to either parietal or visceral endoderm. Parietal endoderm derived from beta 1-deficient cells retained a rounded morphology and migrated poorly on both fibronectin and vitronectin. Visceral endoderm derived from beta 1-deficient cells were also unable to form a normal, confluent epithelial monolayer; instead, a non-contiguous layer containing clumps of disorganized cells was observed. However, loss of beta 1 integrins did not interfere with induction by differentiating agents of tissue-specific gene products for either visceral or parietal endoderm. These results suggest that beta 1 integrins mediate morphological differentiation (migration and epithelial formation) but not tissue-specific gene expression in induced F9 cells, and that these two processes are not necessarily linked in this system.

Comparison of DNA binding and integration half-site selection by avian myeloblastosis virus integrase

Insertion of the linear retrovirus DNA genome into the host DNA by the virus-encoded integrase (IN) is essential for efficient replication. We devised an efficient virus-like DNA plasmid integration assay which mimics the standard oligonucleotide assay for integration. It permitted us to study, by electron microscopy and sequence analysis, insertion of a single long terminal repeat terminus (LTR half-site) of one plasmid into another linearized plasmid. The reaction was catalyzed by purified avian myeloblastosis virus IN in the presence of Mg2+. The recombinant molecules were easily visualized and quantitated by agarose gel electrophoresis. Agarose gel-purified recombinants could be genetically selected by transformation of ligated recombinants into Escherichia coli HB101 cells. Electron microscopy also permitted the identification and localization of IN-DNA complexes on the virus-like substrate in the absence of the joining reaction. Intramolecular and intermolecular DNA looping by IN was visualized. Although IN preferentially bound to AT-rich regions in the absence of the joining reaction, there was a bias towards GC-rich regions for the joining reaction. Alignment of 70 target site sequences 5' of the LTR half-site insertions with 68 target sites previously identified for the concerted insertion of both LTR termini (LTR full-site reaction) indicated similar GC inflection patterns with both insertional events. Comparison of the data suggested that IN recognized only half of the target sequences necessary for integration with the LTR half-site reaction.

FROM MILITARY ORIGIN TO THERAPEUTIC APPLICATION

1. The objective of the debriefing process is the prevention of post-traumatic stress disorder (PTSD). Risk factors for PTSD can be classified into three categories: premorbid personality, the environment, and the trauma itself. 2. Nurses are in a position to intervene using debriefing at primary, secondary, and tertiary levels of prevention. 3. Debriefing, individually and in groups, is an effective intervention in preventing the adverse reactions incurred by a traumatic stressor. The use of a debriefing model counteracts the tendency to suppress the powerfully affective component of the traumatic experience.

Concerted integration of viral DNA termini by purified avian myeloblastosis virus integrase

Concerted integration of retroviral DNA termini, which produces a characteristic duplication of sequences at the integration site and formation of the proviral state, is a necessary step of the retroviral life cycle. We investigated the pairwise integration reaction catalyzed by purified avian retrovirus integrase by measuring the response to solution parameters and how the sequences of the viral termini, which comprise the avian imperfect inverted repeat, affect the reaction. When we optimized the reaction, an efficiency was achieved which approached that measured in systems using cytoplasmic extracts from virus-infected cells. The response of purified avian integrase to solution parameters was similar to that of the integration activity derived from cellular extracts. For strand transfer, the U3 viral terminal sequences were preferred to those of the U5 termini, a result we previously showed for the trimming reaction. That the sequence preference was the same for trimming and strand transfer may be further evidence that only one catalytic site is used for both reactions. A significant number of integration sites were sequenced. Interesting trends were found for the fidelity of the host duplications to the avian 6-bp duplication size, the clustering of the integration sites in the nonessential region of the lambda host DNA, and the sequence characteristics of the duplication sites.

Distribution patterns of extracellular matrix components and adhesion receptors are intricately modulated during first trimester cytotrophoblast differentiation along the invasive pathway, in vivo

Development of the human embryo depends on the ability of first trimester cytotrophoblastic stem cells to differentiate and invade the uterus. In this process, transient expression of an invasive phenotype is part of normal cytotrophoblast differentiation. Morphologically, this process begins when polarized chorionic villus cytotrophoblasts form multilayered columns of nonpolarized cells, and invade the uterus. Using immunocytochemistry, we compared the presence of adhesion receptors and extracellular matrix ligands on cytotrophoblasts in villi, cell columns, and the uterine wall. Villus cytotrophoblasts, anchored to basement membrane, stained for alpha 6 and beta 4 integrin subunits and both merosin and A-chain-containing laminin. Nonpolarized cytotrophoblasts in columns expressed primarily alpha 5 and beta 1 integrin subunits and a fibronectin-rich matrix. Cytotrophoblast clusters in the uterine wall stained for alpha 1, alpha 5, and beta 1 integrins, but not for most extracellular matrix antigens, suggesting that they interact primarily with maternal cells and matrices. Tenascin staining was restricted to stroma at sites of transition in cytotrophoblast morphology, suggesting that tenascin influences cytotrophoblast differentiation. Our results suggest that regulation of adhesion molecule expression contributes to acquisition of an invasive phenotype by cytotrophoblasts and provide a foundation for studying pathological conditions in which insufficient or excessive trophoblast invasion occurs, such as preeclampsia or choriocarcinoma.

Development of an acid-soluble assay for measuring retrovirus integrase 3'-OH terminal nuclease activity

A quantitative and efficient assay was developed to measure the 3'-OH terminal DNA endonuclease activity of the avian myeloblastosis virus (AMV) integrase protein. A retroviral-like linearized plasmid containing long terminal repeat (LTR) sequences at its recessed 3'-OH termini was filled in and labeled with the Escherichia coli Klenow DNA polymerase fragment. The 32P-labeled nucleotide was located at the penultimate position. The labeled linearized plasmid or restriction fragments derived from it were incubated with AMV IN and release of the label was quantitated by conversion to acid-soluble counts. The structure of the released product was characterized on 23% sequencing gels. Results indicate that AMV integration protein is functioning as an endonuclease releasing a dinucleotide and that the activity is stoichiometric with a preference for the cleavage of the U3 LTR terminus over that of the U5 LTR terminus.

92-kD type IV collagenase mediates invasion of human cytotrophoblasts

The specialized interaction between embryonic and maternal tissues is unique to mammalian development. This interaction begins with invasion of the uterus by the first differentiated embryonic cells, the trophoblasts, and culminates in formation of the placenta. The transient tumor-like behavior of cytotrophoblasts, which peaks early in pregnancy, is developmentally regulated. Likewise, in culture only early-gestation human cytotrophoblasts invade a basement membrane-like substrate. These invasive cells synthesize both metalloproteinases and urokinase-type plasminogen activator. Metalloproteinase inhibitors and a function-perturbing antibody specific for the 92-kD type IV collagen-degrading metalloproteinase completely inhibited cytotrophoblast invasion, whereas inhibitors of the plasminogen activator system had only a partial (20-40%) inhibitory effect. We conclude that the 92-kD type IV collagenase is critical for cytotrophoblast invasion.

Removal of 3'-OH-terminal nucleotides from blunt-ended long terminal repeat termini by the avian retrovirus integration protein

The avian myeloblastosis virus integration protein (IN) was capable of removing a specific set of 3'-OH-terminal nucleotides from blunt-ended long terminal repeat (LTR) substrates which resembled linear viral DNA in vivo. The 3'-OH-recessed ends map to the in vivo site of integration on linear viral DNA. The linear DNA plasmid substrate was formed by the generation of a unique DraI restriction enzyme site (TTT/AAA) at the circle junction of a 330-bp tandem LTR-LTR insert. IN preferentially released the three T nucleotides from the minus strand of the U3 LTR substrate compared with its ability to remove the three T nucleotides from the plus strand of the U5 LTR substrate. It was also observed that IN was capable of cleaving a non-LTR DNA substrate containing sequence homology to the U5 LTR terminus.