CD4 receptor diversity represents an ancient protection mechanism against primate lentiviruses.

Infection with human and simian immunodeficiency viruses (HIV/SIV) requires binding of the viral envelope glycoprotein (Env) to the host protein CD4 on the surface of immune cells. Although invariant in humans, the Env binding domain of the chimpanzee CD4 is highly polymorphic, with nine coding variants circulating in wild populations. Here, we show that within-species CD4 diversity is not unique to chimpanzees but found in many African primate species. Characterizing the outermost (D1) domain of the CD4 protein in over 500 monkeys and apes, we found polymorphic residues in 24 of 29 primate species, with as many as 11 different coding variants identified within a single species. D1 domain amino acid replacements affected SIV Env-mediated cell entry in a single-round infection assay, restricting infection in a strain- and allele-specific fashion. Several identical CD4 polymorphisms, including the addition of N-linked glycosylation sites, were found in primate species from different genera, providing striking examples of parallel evolution. Moreover, seven different guenons (Cercopithecus spp.) shared multiple distinct D1 domain variants, pointing to long-term trans-specific polymorphism. These data indicate that the HIV/SIV Env binding region of the primate CD4 protein is highly variable, both within and between species, and suggest that this diversity has been maintained by balancing selection for millions of years, at least in part to confer protection against primate lentiviruses. Although long-term SIV-infected species have evolved specific mechanisms to avoid disease progression, primate lentiviruses are intrinsically pathogenic and have left their mark on the host genome.

Contribution of proteasome-catalyzed peptide cis-splicing to viral targeting by CD8+ T cells in HIV-1 infection.

Peptides generated by proteasome-catalyzed splicing of noncontiguous amino acid sequences have been shown to constitute a source of nontemplated human leukocyte antigen class I (HLA-I) epitopes, but their role in pathogen-specific immunity remains unknown. CD8+ T cells are key mediators of HIV type 1 (HIV-1) control, and identification of novel epitopes to enhance targeting of infected cells is a priority for prophylactic and therapeutic strategies. To explore the contribution of proteasome-catalyzed peptide splicing (PCPS) to HIV-1 epitope generation, we developed a broadly applicable mass spectrometry-based discovery workflow that we employed to identify spliced HLA-I-bound peptides on HIV-infected cells. We demonstrate that HIV-1-derived spliced peptides comprise a relatively minor component of the HLA-I-bound viral immunopeptidome. Although spliced HIV-1 peptides may elicit CD8+ T cell responses relatively infrequently during infection, CD8+ T cells primed by partially overlapping contiguous epitopes in HIV-infected individuals were able to cross-recognize spliced viral peptides, suggesting a potential role for PCPS in restricting HIV-1 escape pathways. Vaccine-mediated priming of responses to spliced HIV-1 epitopes could thus provide a novel means of exploiting epitope targets typically underutilized during natural infection.

CD4 receptor diversity in chimpanzees protects against SIV infection.

Human and simian immunodeficiency viruses (HIV/SIVs) use CD4 as the primary receptor to enter target cells. Here, we show that the chimpanzee CD4 is highly polymorphic, with nine coding variants present in wild populations, and that this diversity interferes with SIV envelope (Env)-CD4 interactions. Testing the replication fitness of SIVcpz strains in CD4+ T cells from captive chimpanzees, we found that certain viruses were unable to infect cells from certain hosts. These differences were recapitulated in CD4 transfection assays, which revealed a strong association between CD4 genotypes and SIVcpz infection phenotypes. The most striking differences were observed for three substitutions (Q25R, Q40R, and P68T), with P68T generating a second N-linked glycosylation site (N66) in addition to an invariant N32 encoded by all chimpanzee CD4 alleles. In silico modeling and site-directed mutagenesis identified charged residues at the CD4-Env interface and clashes between CD4- and Env-encoded glycans as mechanisms of inhibition. CD4 polymorphisms also reduced Env-mediated cell entry of monkey SIVs, which was dependent on at least one D1 domain glycan. CD4 allele frequencies varied among wild chimpanzees, with high diversity in all but the western subspecies, which appeared to have undergone a selective sweep. One allele was associated with lower SIVcpz prevalence rates in the wild. These results indicate that substitutions in the D1 domain of the chimpanzee CD4 can prevent SIV cell entry. Although some SIVcpz strains have adapted to utilize these variants, CD4 diversity is maintained, protecting chimpanzees against infection with SIVcpz and other SIVs to which they are exposed.

Development of an Undergraduate Medical Education Critical Care Content Outline Utilizing the Delphi Method.

OBJECTIVES: No consensus exists on a standardized critical care content outline for medical student education. The aim of this research is to develop a national undergraduate medical education critical care content outline. DESIGN: The authors used a Delphi process to reach expert consensus on a content outline that identified the core critical care knowledge topics and procedural skills that medical students should learn prior to entering residency. Over three iterative rounds, the expert panel reached consensus on a critical care content outline. SETTING: An electronic survey of critical care medical educators, residency program directors, and residents in the United States. SUBJECTS: The expert panel included three groups as follows: 1) undergraduate medical education critical care educators, 2) residency program directors representing all core specialties, and 3) residents representing their core specialties. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The expert panel included 28 members. Experts represented the following medical specialties: anesthesiology, emergency medicine, internal medicine, obstetrics and gynecology, pediatrics, and surgery. Seventeen experts had subspecialty training in critical care. The expert panel identified 19 highly recommended critical care knowledge topics and procedural skills. These topics and procedural skills were grouped into five broad categories as follows: 1) neurologic, 2) respiratory, 3) cardiovascular, 4) renal and electrolytes, and 5) supplemental ICU topics. Bag-mask ventilation was the only procedural skill identified as highly recommended. CONCLUSIONS: This study provides a national consensus undergraduate medical education critical care content outline. By including experts from multiple specialties, this content outline is meaningful for medical student education, independent of medical specialty. The content outline represents a first step in the development of a national undergraduate medical education critical care curriculum.

Resistance to type 1 interferons is a major determinant of HIV-1 transmission fitness.

Sexual transmission of HIV-1 is an inefficient process, with only one or few variants of the donor quasispecies establishing the new infection. A critical, and as yet unresolved, question is whether the mucosal bottleneck selects for viruses with increased transmission fitness. Here, we characterized 300 limiting dilution-derived virus isolates from the plasma, and in some instances genital secretions, of eight HIV-1 donor and recipient pairs. Although there were no differences in the amount of virion-associated envelope glycoprotein, recipient isolates were on average threefold more infectious (P = 0.0001), replicated to 1.4-fold higher titers (P = 0.004), were released from infected cells 4.2-fold more efficiently (P < 0.00001), and were significantly more resistant to type I IFNs than the corresponding donor isolates. Remarkably, transmitted viruses exhibited 7.8-fold higher IFNα2 (P < 0.00001) and 39-fold higher IFNß (P < 0.00001) half-maximal inhibitory concentrations (IC50) than did donor isolates, and their odds of replicating in CD4+ T cells at the highest IFNα2 and IFNß doses were 35-fold (P < 0.00001) and 250-fold (P < 0.00001) greater, respectively. Interestingly, pretreatment of CD4+ T cells with IFNß, but not IFNα2, selected donor plasma isolates that exhibited a transmitted virus-like phenotype, and such viruses were also detected in the donor genital tract. These data indicate that transmitted viruses are phenotypically distinct, and that increased IFN resistance represents their most distinguishing property. Thus, the mucosal bottleneck selects for viruses that are able to replicate and spread efficiently in the face of a potent innate immune response.

Bubble CPAP and oxygen for child pneumonia care in Malawi: a CPAP IMPACT time motion study.

BACKGROUND: In some low-resource settings bubble continuous positive airway pressure (bCPAP) is increasingly used to treat children with pneumonia. However, the time required for healthcare workers (HCWs) to administer bCPAP is unknown and may have implementation implications. This study aims to compare HCW time spent administering bCPAP and low-flow nasal oxygen care at a district hospital in Malawi during CPAP IMPACT (Improving Mortality for Pneumonia in African Children Trial). METHODS: Eligible participants were 1-59 months old with WHO-defined severe pneumonia and HIV-infection, HIV-exposure, severe malnutrition, or hypoxemia and were randomized to either bCPAP or oxygen. We used time motion techniques to observe hospital care in four hour blocks during treatment initiation or follow up (maintenance). HCW mean time per patient at the bedside over the observation period was calculated by study arm. RESULTS: Overall, bCPAP required an average of 34.71 min per patient more than low-flow nasal oxygen to initiate (bCPAP, 118.18 min (standard deviation (SD) 42.73 min); oxygen, 83.47 min (SD, 20.18 min), p < 0.01). During initiation, HCWs spent, on average, 12.45 min longer per patient setting up bCPAP equipment (p < 0.01) and 11.13 min longer per patient setting up the bCPAP nasal interface (p < 0.01), compared to oxygen equipment and nasal cannula set-up. During maintenance care, HCWs spent longer on average per patient adjusting bCPAP, compared to oxygen equipment (bCPAP 4.57 min (SD, 4.78 min); oxygen, 1.52 min (SD, 2.50 min), p = 0.03). CONCLUSION: Effective bCPAP implementation in low-resource settings will likely create additional HCW burden relative to usual pneumonia care with oxygen. TRIAL REGISTRATION: Clinicaltrials.gov NCT02484183 , June 29, 2015.

Acute Presentation and Management of the Encephalopathic Child With an Undiagnosed Inborn Error of Metabolism.

BACKGROUND: Inborn errors of metabolism (IEM) commonly present in infancy and, less commonly, later in life. CASE REPORT: This case describes an IEM, specifically, ornithine transcarbamylase deficiency, in a previously healthy 7-year-old boy who presented to an emergency department with vomiting for approximately 24 h prior to admission. The child became progressively encephalopathic while in the emergency department, but an ammonia level was not obtained until several hours after admission. Irreversible brain damage with cerebral edema was already present at time of diagnosis, leading to death. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: This case emphasizes that acute hyperammonemia can rapidly cause irreversible neurological damage and, in the case of a newly encephalopathic pediatric patient, ammonia levels should be evaluated early to facilitate proper diagnostic tests and treatment.

Development of a Prioritized Anesthesiology Residency Critical Care Content Outline.

Background: Critical care education is an important, mandatory component of residency training in anesthesiology. Currently, there is no accepted national standardized curriculum, and a prioritized critical care content outline would be beneficial to the creation of a pragmatic standardized residency curriculum. The modified Delphi method is a recognized method for establishing consensus in medical education. Methods: We developed a prioritized critical care content outline using the modified Delphi method. Topics were selected from critical care topics included in the Program Requirements for Graduate Medical Education in Anesthesiology and the American Board of Anesthesiology Content Outline. Panel members rated critical care topics on a 9-point Likert scale (1 = not important, 9 = mandatory). Consensus was defined as ≥75% rating the topic as very important to mandatory for inclusion (Likert scale 7-9). Topics with >80% consensus were removed from subsequent surveys and included in the final list, and topics with <50% were removed. Members were asked to select the ideal timing of topic delivery during residency (Foundational-Early Residency, Intermediate-Mid Residency, Advanced-Late Residency). Results: A total of 158 panel members who were contacted using national anesthesiology organization email lists completed the initial round, 119 (75%) completed the second iteration, and 116 (73%) completed the third. Response rate on the first survey was (22/55) 40% for anesthesiology critical care program directors, (18/132) 14% for core anesthesiology residency program directors, and (77/1150) 7% for the remaining respondents. Trainees (n = 41) were not included in response rate calculations. Most participants (103/158, 65%) had completed both core anesthesiology and subspecialty critical care medicine training and most (87/158, 55%) had formal roles in medical education. Forty-one (26%) responders were currently in training. All panelists worked in institutions with graduate medical education (GME) learners. Fifty-eight of 136 (43%) topics met consensus for inclusion. Most consensus topics (50/58, 86%) were recommended to be delivered early during residency with the other 8 topics to be delivered in the middle of residency. Conclusions: We developed a prioritized critical care content outline for anesthesiology residents that includes highly recommended critical care topics with ideal timing for inclusion in residency. This outline provides the first step in developing a pragmatic standardized curriculum to guide faculty and programs in critical care education.

"I really liked the chance to talk about it": Students' Reflections on the Process of Completing Paper Puzzles, a Novel Active Learning Activity.

Introduction: Research shows active learning is an effective teaching method. However, few qualitative studies explore medical student perceptions of the active learning process. The present study explored what students thought about while completing paper puzzles, an active learning tool used at the University of Utah School of Medicine, to understand what and how medical students think while engaged in active learning. Materials and Methods: To investigate second-year medical students' attitudes toward these active learning exercises, three Zoom-based focused groups were held and recorded throughout the course. Recordings were transcribed and coded using thematic analysis. Results: Students reported that peer interactions were of high value, and that while some interactions and thought processes were action-oriented, others were more metacognitive. Other benefits of the activity included promotion of learning, provision of structure, and designation of high-yield concepts. Challenges included feelings of confusion, problems with timing or difficulty of the tasks, and low utility without adequate preparation. Discussion: These findings reflect student-acknowledged pros and cons of active learning described in education literature and add further insight into the thoughts and conversations students have during active learning activities. These include practicing metacognitive skills, triaging information, and learning from peers. Conclusions: These data further elucidate student perceptions of active learning activities in medical education. Though focused on a specific activity, the data can help medical educators understand what students appreciate about active learning and what they think about while engaged in such activities. Supplementary Information: The online version contains supplementary material available at 10.1007/s40670-022-01682-y.

Facile Synthesis of Functionalised Hyperbranched Polymers for Application as Novel, Low Viscosity Lubricant Formulation Components.

A novel, previously unreported, method for synthesising hyperbranched (HB) materials is detailed. Their use as additives to produce lubricant formulations that exhibit enhanced levels of wear protection and improved low-temperature oil viscosity and flow is also reported. The lubricant formulations containing HB additives were found to exhibit both significantly lower viscosities and improved in-use film-forming properties than the current industry standard formulations. To achieve this, alkyl methacrylate oligomers (predominantly dimers and trimers) were synthesised using catalytic chain transfer polymerisation. These were then used as functional chain transfer agents (CTA) to control the polymerisation of divinyl benzene (DVB) monomers to generate highly soluble, high polydispersity HB polymers. The level of dimer/trimer purification applied was varied to define its influence on both these HB resultant structures and the resultant HB additives' performance as a lubricant additive. It was shown that, while the DVB acted as the backbone of the HB, the base oil solubility of the additive was imparted by the presence of the alkyl chains included in the structure via the use of the oligomeric CTAs.

Identifying modifiable risk factors for mortality in children aged 1-59 months admitted with WHO-defined severe pneumonia: a single-centre observational cohort study from rural Malawi.

OBJECTIVE: Although HIV infection, severe malnutrition and hypoxaemia are associated with high mortality in children with WHO-defined severe pneumonia in sub-Saharan Africa, many do not have these conditions and yet mortality remains elevated compared with high-resource settings. Further stratifying mortality risk for children without these conditions could permit more strategic resource utilisation and improved outcomes. We therefore evaluated associations between mortality and clinical characteristics not currently recognised by the WHO as high risk among children in Malawi with severe pneumonia but without HIV (including exposure), severe malnutrition and hypoxaemia. METHODS: Between May 2016 and March 2018, we conducted a prospective observational study alongside a randomised controlled trial (CPAP IMPACT) at Salima District Hospital in Malawi. Children aged 1-59 months hospitalised with WHO-defined severe pneumonia without severe malnutrition, HIV and hypoxaemia were enrolled. Study staff assessed children at admission and ascertained hospital outcomes. We compared group characteristics using Student's t-test, rank-sum test, χ2 test or Fisher's exact test as appropriate. RESULTS: Among 884 participants, grunting (10/112 (8.9%) vs 11/771 (1.4%)), stridor (2/14 (14.2%) vs 19/870 (2.1%)), haemoglobin <50 g/L (3/27 (11.1%) vs 18/857 (2.1%)) and malaria (11/204 (5.3%) vs 10/673 (1.4%)) were associated with mortality compared with children without these characteristics. Children who survived had a 22 g/L higher mean haemoglobin and 0.7 cm higher mean mid-upper arm circumference (MUAC) than those who died. CONCLUSION: In this single-centre study, our analysis identifies potentially modifiable risk factors for mortality among hospitalised Malawian children with severe pneumonia: specific signs of respiratory distress (grunting, stridor), haemoglobin <50 g/L and malaria infection. Significant differences in mean haemoglobin and MUAC were observed between those who survived and those who died. These factors could further stratify mortality risk among hospitalised Malawian children with severe pneumonia lacking recognised high-risk conditions.

High-Frequency Percussive Ventilation in Viral Bronchiolitis.

BACKGROUND: High-frequency percussive ventilation (HFPV) is an alternative mode of mechanical ventilation that has been shown to improve gas exchange in subjects with severe respiratory failure. We hypothesized that HFPV use would improve ventilation and oxygenation in intubated children with acute bronchiolitis. METHODS: In this single-center prospective cohort study we included mechanically ventilated children in the pediatric ICU with bronchiolitis 1-24 months old who were transitioned to HFPV from conventional invasive mechanical ventilation from November 2018-April 2020. Patients with congenital heart disease, on extracorporeal membrane oxygenation (ECMO), and with HFPV duration < 12 h were excluded. Subject gas exchange metrics and ventilator parameters were compared before and after HFPV initiation. RESULTS: Forty-one of 192 (21%) patients intubated with bronchiolitis underwent HFPV, and 35 met inclusion criteria. Median age of cohort was 4 months, and 60% were previously healthy. All subjects with available oxygenation saturation index (OSI) measurements pre-HFPV met pediatric ARDS criteria (31/35, 89%). Mean CO2 decreased from 65.4 in the 24 h pre-HFPV to 51 (P < .001) in the 24 h post initiation. SpO2 /FIO2 was significantly improved at 24 h post-HFPV (153.3 to 209.7, P = .001), whereas the decrease in mean OSI at 24 h did not meet statistical significance (11.9 to 10.2, P = .15). The mean peak inspiratory pressure (PIP) decreased post-HFPV from 29.7 to 25.0 at 24 h (P < .001). No subjects developed an air leak or hemodynamic instability secondary to HFPV. Two subjects required ECMO, and of these, one subject died. CONCLUSIONS: HFPV was associated with significant improvement in ventilation and decreased exposure to high PIPs for mechanically ventilated children with bronchiolitis in our cohort and had a potential association with improved oxygenation. Our study shows that HFPV may be an effective alternative mode of ventilation in patients with bronchiolitis who have poor gas exchange on conventional invasive mechanical ventilation.

Continuous positive airway pressure for children in resource-limited settings, effect on mortality and adverse events: systematic review and meta-analysis.

OBJECTIVE: Determine non-invasive ventilation with continuous positive airway pressure (CPAP) outcomes for paediatric respiratory distress in low-income and middle-income countries (LMICs). DESIGN: Systematic review and meta-analysis. SETTING: LMIC hospitals. PATIENTS: One month to 15 year olds with respiratory distress. INTERVENTIONS: We searched Medline, Embase, LILACS, Web of Science and Scopus on 7 April 2020. Included studies assessed CPAP safety, efficacy or effectiveness. All study types were included; neonatal only studies were excluded. Data were extracted by two reviewers and bias was assessed. Certainty of evidence was evaluated, and risk ratios (RR) were produced for meta-analyses. (PROSPERO protocol CRD42018084278). RESULTS: 2174 papers were screened, 20 were included in the systematic review and 3 were included in two separate meta-analyses of mortality and adverse events. Studies suitable for meta-analysis were randomised controlled trials (RCTs) from Bangladesh, Ghana and Malawi. For meta-analyses comparing death or adverse events between CPAP and low-flow oxygen recipients, we found no clear CPAP effect on mortality (RR 0.75, 95% CI 0.33 to 1.72) or adverse events (RR 1.52, CI 0.71 to 3.26). We downgraded the certainty of evidence for both death and adverse events outcomes to 'low' due to design issues and results discrepancies across RCTs. CONCLUSIONS: Evidence for CPAP efficacy against mortality and adverse events has low certainty and is context dependent. Hospitals introducing CPAP need to have mechanisms in place to optimise safety in the context it is being used; this includes the location (a high dependency or intensive care area), adequate numbers of staff trained in CPAP use, close monitoring and mechanisms for escalation, daily direct physician supervision, equipment that is age appropriate and user-friendly and continuous monitoring of outcomes and quality of care.

Assessment for Learning with Ungraded and Graded Assessments.

Introduction: Assessment for learning has many benefits, but learners will still encounter high-stakes decisions about their performance throughout training. It is unknown if assessment for learning can be promoted with a combination model where scores from some assessments are factored into course grades and scores from other assessments are not used for course grading. Methods: At the University of Utah School of Medicine, year 1-2 medical students (MS) completed multiple-choice question quiz assessments and final examinations in six systems-based science courses. Quiz and final examination performance counted toward course grades for MS2017-MS2018. Starting with the MS2020 cohort, quizzes no longer counted toward course grades. Quiz, final examination, and Step 1 scores were compared between ungraded quiz and graded quiz cohorts with independent samples t-tests. Student and faculty feedback was collected. Results: Quiz performance was not different for the ungraded and graded cohorts (p = 0.173). Ungraded cohorts scored 4% higher on final examinations than graded cohorts (p ≤ 0.001, d = 0.88). Ungraded cohorts scored above the national average and 11 points higher on Step 1 compared to graded cohorts, who had scored below the national average (p ≤ 0.001, d = 0.64). During the study period, Step 1 scores increased by 2 points nationally. Student feedback was positive, and faculty felt it improved their relationship with students. Discussion: The change to ungraded quizzes did not negatively affect final examination or Step 1 performance, suggesting a combination of ungraded and graded assessments can effectively promote assessment for learning.

Antibiotic treatment failure in children aged 1 to 59 months with World Health Organization-defined severe pneumonia in Malawi: A CPAP IMPACT trial secondary analysis.

BACKGROUND: Pneumonia is a leading cause of mortality in children <5 years globally. Early identification of hospitalized children with pneumonia who may fail antibiotics could improve outcomes. We conducted a secondary analysis from the Malawi CPAP IMPACT trial evaluating risk factors for antibiotic failure among children hospitalized with pneumonia. METHODS: Participants were 1-59 months old with World Health Organization-defined severe pneumonia and hypoxemia, severe malnutrition, and/or HIV exposure/infection. All participants received intravenous antibiotics per standard care. First-line antibiotics were benzylpenicillin and gentamicin for five days. Study staff assessed patients for first-line antibiotic failure daily between days 3-6. When identified, patients failing antibiotics were switched to second-line ceftriaxone. Analyses excluded children receiving ceftriaxone and/or deceased by hospital day two. We compared characteristics between patients with and without treatment failure and fit multivariable logistic regression models to evaluate associations between treatment failure and admission characteristics. RESULTS: From June 2015-March 2018, 644 children were enrolled and 538 analyzed. Antibiotic failure was identified in 251 (46.7%) participants, and 19/251 (7.6%) died. Treatment failure occurred more frequently with severe malnutrition (50.2% (126/251) vs 28.2% (81/287), p<0.001) and amongst those dwelling ≥10km from a health facility (22.3% (56/251) vs 15.3% (44/287), p = 0.026). Severe malnutrition occurred more frequently among children living ≥10km from a health facility than those living <10km (49.0% (49/100) vs 35.7% (275/428), p = 0.014). Children with severe malnutrition (adjusted odds ratio (aOR) 2.2 (95% CI 1.52, 3.24), p<0.001) and pre-hospital antibiotics ((aOR 1.47, 95% CI 1.01, 2.14), p = 0.043) had an elevated aOR for antibiotic treatment failure. CONCLUSION: Severe malnutrition and pre-hospital antibiotic use predicted antibiotic treatment failure in this high-risk severe pneumonia pediatric population in Malawi. Our findings suggest addressing complex sociomedical conditions like severe malnutrition and improving pneumonia etiology diagnostics will be key for better targeting interventions to improve childhood pneumonia outcomes.

Early failure of N-methyl-D-aspartate receptors and deficient spine formation induced by reduction of regulatory heme in neurons.

An initial stage of many neurodegenerative processes is associated with compromised synaptic function and precedes synapse loss, neurite fragmentation, and neuronal death. We showed previously that deficiency of heme, regulating many proteins of pharmacological importance, causes neurodegeneration of primary cortical neurons via N-methyl-d-aspartate receptor (NMDAR)-dependent suppression of the extracellular signal-regulated kinase 1/2 pathway. Here, we asked whether the reduction of heme causes synaptic perturbation before neurite fragmentation in neuronal cultures and investigated molecular mechanisms of synaptic dysfunction in these cells. We showed the change in the NR2B subunit phosphorylation that correlates with compromised NMDAR function after the reduction of regulatory heme and a rapid rescue of NR2B phosphorylation and NMDAR function by exogenous heme. Electrophysiological recordings demonstrated diminished NMDAR currents and NMDAR-mediated calcium influx after 24 h of inhibition of heme synthesis. These effects were reversed by treatment with heme; however, inhibition of the Src family kinases abolished the rescue effect of heme on NMDA-evoked currents. Diminished NMDAR current and Ca(2+) influx resulted in suppressed cGMP production and impairment of spine formation. Exogenous heme exerted rescue effects on NR2B tyrosine phosphorylation and NMDA-evoked currents within minutes, suggesting direct interactions within the NMDAR complex. These synaptic changes after inhibition of heme synthesis occurred at this stage without apparent dysfunction of major hemoproteins. We conclude that regulatory heme is necessary in maintaining NR2B phosphorylation and NMDAR function. NMDAR failure occurs before neurite fragmentation and may be a causal factor in neurodegeneration; this could suggest a route for an early pharmacological intervention.

Complex response to physiological and drug-induced hepatic heme demand in monoallelic ALAS1 mice.

Regulation of 5-aminolevulinate synthase 1 (ALAS1) for nonerythroid heme is critical for respiration, cell signaling mechanisms and steroid/drug metabolism. ALAS1 is induced in some genetic disorders but unlike other genes in the heme pathway, a gene variant of ALAS1 associated with inherited disease has not been reported. BALB/c mice carrying a null ALAS1 allele caused by a ßGEO insert were developed and used to determine the consequences of heme demand of a semi gene copy number. Homozygous disruption of ALAS1 (-/-) was lethal for embryo development post day 6.5 but expression in heterozygotes (+/-) was sufficient for the number of offspring and survival. In both wild type (WT +/+) and +/- mice expression of ALAS1 RNA was greatest in liver and harderian gland and much lower in kidney, lung, heart, brain and spleen. The effects of one WT ALAS1 allele in +/- mice on mRNA levels in liver and harderian gland were less marked compared to brain and other organs that were examined. Many other genes were up-regulated by heterozygosity in liver and brain but to a minimal extent. Hepatic heme oxygenase 1 (HMOX1) mRNA expression was significantly lower in +/- mice but not in brain. No elevated translation of WT allele ALAS1 mRNA was detected in +/- liver as a compensatory mechanism for the disabled allele. Fasting induced ALAS1 mRNA in both WT and +/- mice but only in +/- was this manifest as increased ALAS1 protein. The hepatic protoporphyria-inducing drug 4-ethyl-DDC caused induction of hepatic ALAS1 mRNA and protein levels in both WT and +/- mice but markedly less in the mice with only one intact allele. The findings illustrate the complex response of ALAS1 expression for heme demand but limited evidence that upregulation of a wild type allele can compensate for a null allele.

Heightened resistance to host type 1 interferons characterizes HIV-1 at transmission and after antiretroviral therapy interruption.

Type 1 interferons (IFN-I) are potent innate antiviral effectors that constrain HIV-1 transmission. However, harnessing these cytokines for HIV-1 cure strategies has been hampered by an incomplete understanding of their antiviral activities at later stages of infection. Here, we characterized the IFN-I sensitivity of 500 clonally derived HIV-1 isolates from the plasma and CD4+ T cells of 26 individuals sampled longitudinally after transmission or after antiretroviral therapy (ART) and analytical treatment interruption. We determined the concentration of IFNα2 and IFNß that reduced viral replication in vitro by 50% (IC50) and found consistent changes in the sensitivity of HIV-1 to IFN-I inhibition both across individuals and over time. Resistance of HIV-1 isolates to IFN-I was uniformly high during acute infection, decreased in all individuals in the first year after infection, was reacquired concomitant with CD4+ T cell loss, and remained elevated in individuals with accelerated disease. HIV-1 isolates obtained by viral outgrowth during suppressive ART were relatively IFN-I sensitive, resembling viruses circulating just before ART initiation. However, viruses that rebounded after treatment interruption displayed the highest degree of IFNα2 and IFNß resistance observed at any time during the infection course. These findings indicate a dynamic interplay between host innate responses and the evolving HIV-1 quasispecies, with the relative contribution of IFN-I to HIV-1 control affected by both ART and analytical treatment interruption. Although elevated at transmission, host innate pressures are the highest during viral rebound, limiting the viruses that successfully become reactivated from latency to those that are IFN-I resistant.

Recapitulation of HIV-1 Env-antibody coevolution in macaques leading to neutralization breadth.

Neutralizing antibodies elicited by HIV-1 coevolve with viral envelope proteins (Env) in distinctive patterns, in some cases acquiring substantial breadth. We report that primary HIV-1 envelope proteins-when expressed by simian-human immunodeficiency viruses in rhesus macaques-elicited patterns of Env-antibody coevolution very similar to those in humans, including conserved immunogenetic, structural, and chemical solutions to epitope recognition and precise Env-amino acid substitutions, insertions, and deletions leading to virus persistence. The structure of one rhesus antibody, capable of neutralizing 49% of a 208-strain panel, revealed a V2 apex mode of recognition like that of human broadly neutralizing antibodies (bNAbs) PGT145 and PCT64-35S. Another rhesus antibody bound the CD4 binding site by CD4 mimicry, mirroring human bNAbs 8ANC131, CH235, and VRC01. Virus-antibody coevolution in macaques can thus recapitulate developmental features of human bNAbs, thereby guiding HIV-1 immunogen design.

Complex gene-chemical interactions: hepatic uroporphyria as a paradigm.

Many toxicological disorders, in common with numerous human diseases, are probably the consequence of multigene interactions with a variety of chemical and physiological factors. The importance of genetic factors may not be obvious initially from association studies because of their complexity and variable penetrance. The human disease, porphyria cutanea tarda (PCT), is a skin disease caused by the photosensitizing action of porphyrins arising secondary to the decreased activity of an enzyme of heme biosynthesis, uroporphyrinogen decarboxylase (UROD), in the liver. It is triggered by idiosyncratic hepatic interaction between genetic factors and chemicals such as alcohol, estrogenic drugs, and polyhalogenated aromatics. PCT and its animal models are known collectively as the hepatic uroporphyrias. There is strong evidence for the participation of iron in the pathogenesis of these conditions. Mouse models have been used to explore the relative importance of a variety of agents such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), alcohol, and iron in the development of uroporphyria and to elucidate the mechanism of the depression of hepatic UROD activity. Mutations of the UROD and hemochromatosis (HFE) genes are genetic factors in some PCT patients which can be mimicked in mice heterozygous for the Hfe and Urod null genes. Association studies of uroporphyria induced by TCDD or hexachlorobenzene with DNA markers in mouse intercrosses have shown the participation of other, unknown, genetic factors in addition to the strong influence of the Ahr gene. The pathogenesis of hepatic uroporphyrias exemplifies the complexity of the interactions between chemical and genetic factors that can contribute to the hepatotoxicity of chemicals.