C3aR in the medial prefrontal cortex modulates the susceptibility to LPS-induced depressive-like behaviors through glutamatergic neuronal excitability

Complement activation and prefrontal cortical dysfunction both contribute to the pathogenesis of major depressive disorder (MDD), but their interplay in MDD is unclear. We here studied the role of complement C3a receptor (C3aR) in the medial prefrontal cortex (mPFC) and its influence on depressive-like behaviors induced by systematic lipopolysaccharides (LPS) administration. C3aR knockout (KO) or intra-mPFC C3aR antagonism confers resilience, whereas C3aR expression in mPFC neurons makes KO mice susceptible to LPS-induced depressive-like behaviors. Importantly, the excitation and inhibition of mPFC neurons have opposing effects on depressive-like behaviors, aligning with increased and decreased excitability by C3aR deletion and activation in cortical neurons. In particular, inhibiting mPFC glutamatergic (mPFCGlu) neurons, the main neuronal subpopulation expresses C3aR, induces depressive-like behaviors in saline-treated WT and KO mice, but not in LPS-treated KO mice. Compared to hypoexcitable mPFCGlu neurons in LPS-treated WT mice, C3aR-null mPFCGlu neurons display hyperexcitability upon LPS treatment, and enhanced excitation of mPFCGlu neurons is anti-depressant, suggesting a protective role of C3aR deficiency in these circumstances. In conclusion, C3aR modulates susceptibility to LPS-induced depressive-like behaviors through mPFCGlu neuronal excitability. This study identifies C3aR as a pivotal intersection of complement activation, mPFC dysfunction, and depression and a promising therapeutic target for MDD.

[Construction of natural population cohort on telephone follow-up management quality control system and discussion regarding critical issues by REDCap system]

With completing a baseline survey of a large natural population cohort, conducting regular follow-up has become a key factor in further improving the quality of cohort construction and ensuring its sustainable development. Typical cohort follow-up methods include repeat surveys, routine monitoring, and community-oriented surveillance. However, in practical applications, there are often issues such as high costs, difficulty, and high error rates. Telephone follow-up is an important supplementary method to the methods mentioned above, as it has the characteristics of low cost, fast response, and high quality. However, the with difficult organization, quality control is challenging, response rates are low, and management levels vary widely, which limits its widespread use in large-scale population cohort studies. Given the above problems, this study draws on customer relationship management based on the actual needs of the China Northwest Cohort follow-up. It relies on the REDCap electronic data collection platform to build a telephone follow-up management and quality control system. Targeted solutions are provided for key issues in telephone follow-up implementation, including organizational structure, project management, data collection, and process quality control, to improve the quality control level of telephone follow-up comprehensively and thereby enhance the quality and efficiency of follow-up. We hope to provide standardized follow-up programs and efficient quality control tools for newly established and existing cohort studies.

Distinct Circuits From the Central Lateral Amygdala to the Ventral Part of the Bed Nucleus of Stria Terminalis Regulate Different Fear Memory

BACKGROUND

The ability to differentiate stimuli that predict fear is critical for survival; however, the underlying molecular and circuit mechanisms remain poorly understood.

METHODS

We combined transgenic mice, in vivo transsynaptic circuit-dissecting anatomical approaches, optogenetics, pharmacological methods, and electrophysiological recording to investigate the involvement of specific extended amygdala circuits in different fear memory.

RESULTS

We identified the projections from central lateral amygdala (CeL) protein kinase C δ (PKCδ)-positive neurons and somatostatin (SST)-positive neurons to GABAergic (gamma-aminobutyric acidergic) and glutamatergic neurons in the ventral part of the bed nucleus of stria terminalis (vBNST). Prolonged optogenetic activation or inhibition of the PKCδCeL-vBNST pathway specifically reduced context fear memory, whereas the SSTCeL-vBNST pathway mainly reduced tone fear memory. Intriguingly, optogenetic manipulation of vBNST neurons that received the projection from PKCδCeL neurons exerted bidirectional regulation of context fear, whereas manipulation of vBNST neurons that received the projection from SSTCeL neurons could bidirectionally regulate both context and tone fear memory. We subsequently demonstrated the presence of δ and κ opioid receptor protein expression within the CeL-vBNST circuits, potentially accounting for the discrepancy between prolonged activation of GABAergic circuits and inhibition of downstream vBNST neurons. Finally, administration of an opioid receptor antagonist cocktail on the PKCδCeL-vBNST or SSTCeL-vBNST pathway successfully restored context or tone fear memory reduction induced by prolonged activation of the circuits.

CONCLUSIONS

Together, these findings establish a functional role for distinct CeL-vBNST circuits in the differential regulation and appropriate maintenance of fear.

[Application of isotemporal substitution model in epidemiological research]

Isotemporal substitution model is a powerful tool to explore the real association between physical behavior and health outcomes, which has the potential of the application in large-scale cohort study. This paper systematically introduces the principle of isotemporal substitution model and its implementation method in specific analysis to provide analytical ideas for the epidemiological research related to physical behavior in China. The baseline data of Regional Ethic Cohort Study in Northwest China conducted in Shaanxi province were used to analyze the relationship between physical behavior and cardiovascular disease with single-factor model, partition model and isotemporal substitution model. The advantages and disadvantages of different models were compared, and the advantages of isotemporal substitution model in quantifying physical activity health risk were introduced. Isotemporal substitution model could qualify physical behavior and health outcomes, which has wide application value in epidemiological research.

Anisotropic long-range spin transport in canted antiferromagnetic orthoferrite YFeO3

In antiferromagnets, the efficient transport of spin-waves has until now only been observed in the insulating antiferromagnet hematite, where circularly (or a superposition of pairs of linearly) polarized spin-waves diffuse over long distances. Here, we report long-distance spin-transport in the antiferromagnetic orthoferrite YFeO₃, where a different transport mechanism is enabled by the combined presence of the Dzyaloshinskii-Moriya interaction and externally applied fields. The magnon decay length is shown to exceed hundreds of nanometers, in line with resonance measurements that highlight the low magnetic damping. We observe a strong anisotropy in the magnon decay lengths that we can attribute to the role of the magnon group velocity in the transport of spin-waves in antiferromagnets. This unique mode of transport identified in YFeO₃ opens up the possibility of a large and technologically relevant class of materials, i.e., canted antiferromagnets, for long-distance spin transport.

ErbB4 regulate extracellular dopamine through the p38 MAPK signaling pathway

ErbB4 loss-of-function in catecholaminergic neurons induces catecholamine dyshomeostasis. Despite ErbB4's significant role in neuropathology, the signaling pathways that regulate these changes are still widely unknown. In this study, we attempt to identify the downstream pathway of ErbB4 that regulates catecholamine homeostasis. The SH-SY5Y human neuroblastoma cell line was used as the in vitro model for catecholaminergic neurons. Western blotting, enzyme-linked immunosorbent assay, and pharmacological and genetic manipulations by agonist/antagonist or small interference RNA were used to investigate the relationship between ErbB4 and extracellular catecholamines. We confirmed that ErbB4 is abundantly expressed in undifferentiated and retinoic acid-differentiated catecholaminergic cells from the SH-SY5Y cell line. ErbB4 inhibition increase the ratio of phosphorylated p38 to total p38 in SH-SY5Y human neuroblastoma cells. Consistent with previous in vivo observations in mice, ErbB4 deficiency led to increases in extracellular dopamine and norepinephrine levels. However, the resulting increase in extracellular dopamine, but not norepinephrine, could be suppressed by p38 inhibitor SB202190. Our results suggest that both extracellular dopamine and norepinephrine homeostasis could be regulated by ErbB4 in human catecholaminergic cells, and ErbB4 may regulate extracellular dopamine, but not norepinephrine, through the p38 MAPK signaling pathway, thus indicating different regulatory pathways of dopamine and norepinephrine by ErbB4 in catecholaminergic neurons.

MeCP2 in cholinergic interneurons of nucleus accumbens regulates fear learning

Methyl-CpG-binding protein 2 (MeCP2) encoded by the MECP2 gene is a transcriptional regulator whose mutations cause Rett syndrome (RTT). Mecp2-deficient mice show fear regulation impairment; however, the cellular and molecular mechanisms underlying this abnormal behavior are largely uncharacterized. Here, we showed that Mecp2 gene deficiency in cholinergic interneurons of the nucleus accumbens (NAc) dramatically impaired fear learning. We further found that spontaneous activity of cholinergic interneurons in Mecp2-deficient mice decreased, mediated by enhanced inhibitory transmission via α2-containing GABA_A receptors. With MeCP2 restoration, opto- and chemo-genetic activation, and RNA interference in ChAT-expressing interneurons of the NAc, impaired fear retrieval was rescued. Taken together, these results reveal a previously unknown role of MeCP2 in NAc cholinergic interneurons in fear regulation, suggesting that modulation of neurons in the NAc may ameliorate fear-related disorders.

Transcriptome analysis reveals corresponding genes and key pathways involved in heat stress in Hu sheep

Heat stress (HS) seriously affects animal performance. In view of global warming, it is essential to understand the regulatory mechanisms by which animals adapt to heat stress. In this study, our aim was to explore the genes and pathways involved in heat stress in sheep. To this end, we used transcriptome analysis to understand the molecular responses to heat stress and thereby identify means to protect sheep from heat shock. To obtain an overview of the effects of heat stress on sheep, we used the hypothalamus for transcriptome sequencing and identified differentially expressed genes (DEGs; false discovery rate (FDR) < 0.01; fold change > 2) during heat stress. A total of 1423 DEGs (1122 upregulated and 301 downregulated) were identified and classified into Gene Ontology (GO) categories and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Heat stress triggered dramatic and complex alterations in gene expression in the hypothalamus. We hypothesized that heat stress induced apoptosis and dysfunction in cells and vital organs and affected growth, development, reproduction, and circadian entrainment via the calcium signaling pathway, which influences ribosome assembly and function. Real-time PCR was used to evaluate the expression of the genes regulating important biological functions or whose expression profiles were significantly changed after acute heat stress (FDR < 0.01; fold change > 4), and the results showed that the expression patterns of these genes were consistent with the results of transcriptome sequencing, indicating that the credibility of the sequencing results. Our data indicated that heat stress induced calcium dyshomeostasis, blocked biogenesis, caused ROS accumulation, impaired the antioxidant system and innate defense, and induced apoptosis through the P53 signaling pathway activated by PEG3, decreased growth and development, and enhanced organ damage. These data is very important and helpful to elucidate the molecular mechanism of heat stress and finally to find ways to deal with heat stress damage in sheep.

ErbB4 deletion in noradrenergic neurons in the locus coeruleus induces mania-like behavior via elevated catecholamines

Dysfunction of the noradrenergic (NE) neurons is implicated in the pathogenesis of bipolar disorder (BPD). ErbB4 is highly expressed in NE neurons, and its genetic variation has been linked to BPD; however, how ErbB4 regulates NE neuronal function and contributes to BPD pathogenesis is unclear. Here we find that conditional deletion of ErbB4 in locus coeruleus (LC) NE neurons increases neuronal spontaneous firing through NMDA receptor hyperfunction, and elevates catecholamines in the cerebrospinal fluid (CSF). Furthermore, Erbb4-deficient mice present mania-like behaviors, including hyperactivity, reduced anxiety and depression, and increased sucrose preference. These behaviors are completely rescued by the anti-manic drug lithium or antagonists of catecholaminergic receptors. Our study demonstrates the critical role of ErbB4 signaling in regulating LC-NE neuronal function, reinforcing the view that dysfunction of the NE system may contribute to the pathogenesis of mania-associated disorder.

Bipolar disorder is a mental illness that affects roughly 1 in 100 people worldwide. It features periods of depression interspersed with episodes of mania – a state of delusion, heightened excitation and increased activity. Evidence suggests that changes in a brain region called the locus coeruleus contribute to bipolar disorder. Cells within this area produce a chemical called norepinephrine, whose levels increase during mania and decrease during depression. But it is unclear exactly how norepinephrine-producing cells, also known as noradrenergic cells, contribute to bipolar disorder.

The answer may lie in a protein called ErbB4, which is found within the outer membrane of many noradrenergic neurons. ErbB4 is active in both the developing and adult brain, and certain people with bipolar disorder have mutations in the gene that codes for the protein. Might changes in ErbB4 disrupt the activity of noradrenergic neurons? And could these changes increase the risk of bipolar disorder?

To find out, Cao, Zhang et al. deleted the gene for ErbB4 from noradrenergic neurons in the locus coeruleus of mice. The mutant mice showed mania-like behaviors: compared to normal animals, they were hyperactive, less anxious, and consumed more of a sugary solution. Treating the mice with lithium, a medication used in bipolar disorder, reversed these changes and made the rodents behave more like non-mutant animals. Further experiments revealed that noradrenergic neurons in the mutant mice showed increased spontaneous activity. These animals also had more of the chemicals noradrenaline and dopamine in the fluid circulating around their brains and spinal cords.

The results thus suggest that losing ErbB4 enhances the spontaneous firing of noradrenergic neurons in the locus coeruleus. This increases release of noradrenaline and dopamine, which in turn leads to mania-like behaviors. Future research should examine whether drugs that target ErbB4 could treat mania and improve the lives of people with bipolar disorder and related conditions.

Loss of MeCP2 in cholinergic neurons causes part of RTT-like phenotypes via α7 receptor in hippocampus

Mutations in the X-linked MECP2 gene cause Rett syndrome (RTT), an autism spectrum disorder characterized by impaired social interactions, motor abnormalities, cognitive defects and a high risk of epilepsy. Here, we showed that conditional deletion of Mecp2 in cholinergic neurons caused part of RTT-like phenotypes, which could be rescued by re-expressing Mecp2 in the basal forebrain (BF) cholinergic neurons rather than in the caudate putamen of conditional knockout (Chat-Mecp2(-/y)) mice. We found that choline acetyltransferase expression was decreased in the BF and that α7 nicotine acetylcholine receptor signaling was strongly impaired in the hippocampus of Chat-Mecp2(-/y) mice, which is sufficient to produce neuronal hyperexcitation and increase seizure susceptibility. Application of PNU282987 or nicotine in the hippocampus rescued these phenotypes in Chat-Mecp2(-/y) mice. Taken together, our findings suggest that MeCP2 is critical for normal function of cholinergic neurons and dysfunction of cholinergic neurons can contribute to numerous neuropsychiatric phenotypes.

Levels and distribution of synthetic musks and polycyclic aromatic hydrocarbons in sludge collected from Guangdong Province

The levels and distribution of six polycyclic musks, three nitromusks and 15 polycyclic aromatic hydrocarbons (PAHs) were investigated in sludge collected from 19 municipal wastewater treatment plants (WWTPs) in six cities in Guangdong Province, China. PAHs were detected in all of the sludge samples, and the levels of the total 15 PAHs ranged from 177.2-4421.8 μg/kg dry weight (dw). Four polycyclic musks, 4-acetyl-1,1-dimethyl-6-tert-butylindan (ADBI), 6-acetyl-1,1,2,3,3,5-hexamethylindan (AHMI), 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta (g) -2-benzopyran (HHCB) and 7-acetyl -1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydro naphthalene (AHTN), were found in these samples. The total concentrations of polycyclic musks varied from 794.4-12960.3 μg/kg dw, with HHCB and AHTN being the main components. Of the three nitromusks, 2,6-dinitro-3-methoxy-4-tert- butyl - toluene (MA) was only found in one sludge sample at the limit of detection (LOD) level, while 1-tert-butyl-3,5-dimethyl-2,4,6-trinitrobenzene (Musk xylene, MX) and 4-acetyl-1-tert-butyl-3,5-dimethyl-2,6-dinitrobenzene (Musk ketone, MK) were found at levels ranging from the LOD to 65.8 μg/kg dw and LOD to 172.7 μg/kg dw, respectively, in most of the sludge samples. The PAHs, polycyclic musks and nitro musks were also shown to have various distribution patterns, possibly due to their different wastewater sources and wastewater treatment technology.

Nonvolatile taste compounds in cooked Chinese Nanjing duck meat following postproduction heat treatment

Taste-active compounds, including free amino acids, succinic acid and 5'-nucleotides, and chemical components including moisture, pH, protein, crude fat, and sodium chloride were evaluated in cooked and packaged Chinese Nanjing ducks following heat treatments including control, 99 °C for 40 min, 108 °C for 20 min, 92 °C microwave followed by water heating, 95 °C for 30 min, 121 °C for 25 min. Heat treatment decreased (P < 0.05) the content of Alamine and moisture and reduced the pH value in muscle, but increased (P < 0.05) the protein and 5'-nucleotides content. The 99 °C group had a significantly lower crude fat content compared with other groups (P < 0.05). The succinic acid content in the control group was significantly higher than in the 121 °C group (P < 0.05). Groups treated at higher temperatures (108 °C, 121 °C, and microwave) had similar equivalent umami concentrations and 5'-nucleotides, free amino acids content, as well as the derived bitter and sweet taste components compared with the groups treated at lower temperatures. It can be speculated that these differences account for the enhanced flavor of the meat in the 99 °C, 108 °C, 121 °C, and microwave groups compared with the untreated control. Therefore, heat treatment at lower temperature after packaging may prolong product shelf life without any detrimental effects on taste. The results of this study indicate that it is important to use lower temperatures in this type of food processing. However, it may be possible to modify the primary processing steps to improve the content of umami-like taste compounds such as 5'-nucleotides.

PRACTICAL APPLICATION

Heat treatment of packaged products is an effective method for eradication of microbes, therefore increasing the shelf-life. However, such treatment can result in major changes in the sensory perception of meat products, particularly the formation of off-flavors. This study investigated changes in taste-active compounds in duck meat following a number of types of heat treatment.

Structural characterization of a series of 10-carbon sugar derivatives by electrospray-ionization MSn mass spectrometry

Electrospray-ionization MSn mass spectrometry (ESI-MSn) with low-energy, collision-induced dissociation (CID) was used to establish the fragmentation behavior of sodium ion adducts of higher-carbon amino spiro-sugar derivatives. Their fragmentation pathways are proposed on the basis of the MSn studies and deuteration experiments. Some of the rings of these derivatives opened under the conditions of electrospray ionization. Novel fragmentations were observed and their mechanisms are proposed. This study demonstrates the power of modern mass spectrometry for rapid elucidation of the structure of higher-carbon sugar derivatives.

Electrospray ionization mass spectrometric studies of phosphorus oxychloride directed synthesis of homo-oligopeptide ester libraries

With the assistance of phosphorus oxychloride, alpha-amino acids were assembled into homo-peptides, which were analyzed by electrospray ionization mass spectrometry (ESI-MS) and multistage electrospray ionization mass spectrometry (ESI-MS/MS). On quenching with water or various alcohols, the reaction mixtures yielded the corresponding peptides or peptide esters, respectively. This paper reports a simple method to synthesize the homo-oligo-peptide-ester conjugated library by phosphorus oxychloride activation.

Genomic profiling of short- and long-term caloric restriction effects in the liver of aging mice

We present genome-wide microarray expression analysis of 11,000 genes in an aging potentially mitotic tissue, the liver. This organ has a major impact on health and homeostasis during aging. The effects of life- and health-span-extending caloric restriction (CR) on gene expression among young and old mice and between long-term CR (LT-CR) and short-term CR (ST-CR) were examined. This experimental design allowed us to accurately distinguish the effects of aging from those of CR on gene expression. Aging was accompanied by changes in gene expression associated with increased inflammation, cellular stress, and fibrosis, and reduced capacity for apoptosis, xenobiotic metabolism, normal cell-cycling, and DNA replication. LT-CR and just 4 weeks of ST-CR reversed the majority of these changes. LT-CR produced in young mice a pattern of gene expression that is a subset of the changes found in old LT-CR mice. It is possible that the early changes in gene expression, which extend into old age, are key to the life- and health-span-extending effects of CR. Further, ST-CR substantially shifted the "normo-aging" genomic profile of old control mice toward the "slow-aging" profile associated with LT-CR. Therefore, many of the genomic effects of CR are established rapidly. Thus, expression profiling should prove useful in quickly identifying CR- mimetic drugs and treatments.

[Quantitative analysis of sparfloxacin injection by high performance liquid chromatography]

Analytical method of the quantitative determination of sparfloxacin injection by HPLC is described. The analytical conditions were as follows. A Waters Symmetry C18(5 microns, 150 mm x 3.9 mm i.d.) column was used as the analytical column. The detection wavelength was UV-298.8 nm. The column temperature was 30 degrees C. The mobile phase was 0.2% KH2PO4 buffer (pH 3.2)-CH3CN-CH3OH (80:15:5, volume ratio) and the flow-rate was 1.0 mL/min. The injection volume was 10 microL. The linear range (the peak area vs. the mass concentration of sparfloxacin) was from 39.94 mg/L to 199.68 mg/L, and the correlation coefficient was 0.9999. The average recovery of sparfloxacin was 100.1% (n = 5), and its RSD was 0.72%. The RSDs of continuous injections, within day injections per 2 hours and between day injections in three days were 0.19%, 0.14% and 0.13% respectively. The above analytical results show that this method has good precision and stability. It is a rapid, sensitive and accurate method for the analysis of sparfloxacin.

Caloric restriction alters the feeding response of key metabolic enzyme genes

Differential 'fuel usage' has been proposed as a mechanism for life-span extension by caloric restriction (CR). Here, we report the effects of CR, initiated after weaning, on metabolic enzyme gene expression 0, 1.5, 5, and 12 h after feeding of 24-month-old mice. Plasma glucose and insulin were reduced by approximately 20 and 80%. Therefore, apparent insulin sensitivity, as judged by the glucose to insulin ratio, increased 3.3-fold in CR mice. Phosphoenolpyruvate carboxykinase mRNA and activity were transiently reduced 1.5 h after feeding, but were 20-100% higher in CR mice at other times. Glucose-6-phosphatase mRNA was induced in CR mice and repressed in control mice before, and for 5 h following feeding. Feeding transiently induced glucokinase mRNA fourfold in control mice, but only slightly in CR mice. Pyruvate kinase and pyruvate dehydrogenase activities were reduced approximately 50% in CR mice at most times. Feeding induced glutaminase mRNA, and carbamyl phosphate synthetase I and glutamine synthase activity (and mRNA). They were each approximately twofold or higher in CR mice. These results indicate that in mice, CR maintains higher rates of gluconeogenesis and protein catabolism, even in the hours after feeding. The data are consistent with the idea that CR continuously promotes the turnover and replacement of extrahepatic proteins.

Chaperone-mediated regulation of hepatic protein secretion by caloric restriction

Calorie restriction (CR) delays age-related physiological changes, reduces cancer incidence, and increases maximum life span in mammals. Here we show that CR decreased the expression of many hepatic molecular chaperones and concomitantly increased the rate and efficiency of serum protein secretion. Hepatocytes from calorie-restricted mice secreted twice as much albumin, 63% more alpha1-antitrypsin, and 250% more of the 31.5-kDa protein 2 h after their synthesis. A number of trivial explanations for these results, such as differential rates of protein synthesis and cell leakage during the assay, were eliminated. These novel results suggest that CR may promote the secretion of serum proteins, thereby promoting serum protein turnover. This may reduce the circulating level of damaging, glycoxidated serum proteins.

Engineering of noninfectious HIV-1-like particles containing mutant gp41 glycoproteins as vaccine candidates that allow vaccinees to be distinguished from HIV-1 infectees

Many AIDS vaccine candidates under development may elicit immune responses similar to those observed in and used to screen human immunodeficiency virus type 1 (HIV-1)-infected individuals. Therefore, it is important to develop vaccine candidates that incorporate antigenic markers and allow vaccinees to be distinguished from HIV-1 infectees. To this end, we introduced a series of mutations into and in the vicinity of the major immunodominant region (MIR) of gp41 (residues 598-609), a domain recognized by almost all HIV-1 infectees, and evaluated whether HIV-1-like particles incorporating such mutant glycoproteins could be expressed in mammalian cells. Results indicated that although up to three consecutive amino acids could be replaced within MIR without significantly affecting particle formation or gp160 processing, deletions within MIR impaired envelope processing. Replacement of HIV-1 MIR by part or most of the corresponding domain from other lentiviruses markedly decreased or abolished gp160 processing. Synthetic peptides corresponding to a mutated MIR incorporating three amino acid replacements were not recognized by a panel of sera from HIV-1 infectees, suggesting that HIV-1-like particles with this type of mutation represent potential candidate vaccines that could allow vaccinees to be distinguished from HIV-1 infectees.

Identification of retroviral late domains as determinants of particle size

Retroviral Gag proteins, in the absence of any other viral products, induce budding and release of spherical, virus-like particles from the plasma membrane. Gag-produced particles, like those of authentic retrovirions, are not uniform in diameter but nevertheless fall within a fairly narrow distribution of sizes. For the human immunodeficiency virus type 1 (HIV-1) Gag protein, we recently reported that elements important for controlling particle size are contained within the C-terminal region of Gag, especially within the p6 sequence (L. Garnier, L. Ratner, B. Rovinski, S.-X. Cao, and J. W. Wills, J. Virol. 72:4667-4677, 1998). Deletions and substitutions throughout this sequence result in the release of very large particles. Because the size determinant could not be mapped to any one of the previously defined functions within p6, it seemed likely that its activity requires the overall proper folding of this region of Gag. This left open the possibility of the size determinant residing in a subdomain of p6, and in this study, we examined whether the late domain (the region of Gag that is critical for the virus-cell separation step) is involved in controlling particle size. We found that particles of normal size are produced when p6 is replaced with the totally unrelated late domain sequences from Rous sarcoma virus (contained in its p2b sequence) or equine infectious anemia virus (contained in p9). In addition, we found that the large particles released in the absence of p6 require the entire CA and adjacent spacer peptide sequences, whereas these internal sequences of HIV-1 Gag are not needed for budding (or proper size) when a late domain is present. Thus, it appears the requirements for budding are very different in the presence and absence of p6.

Modifications of HIV-1 retrovirus-like particles to enhance safety and immunogenicity

HIV-1 retrovirus-like particles can be produced in VERO cells that have been transfected with an expression construct encoding HIV-1 structural proteins. The particles are entirely non-infectious although structurally they resemble infectious virus particles. This makes them a promising candidate for use as an HIV-1 vaccine. In order to ensure their safety and enhance their immunogenicity, the retrovirus-like particles were modified in a number of ways. A large deletion in the HIV-1 pol gene has eliminated reverse transcriptase and integrase activities. Deletion of RNA packaging signals in the RNA untranslated leader sequence and in Gag reduced packaged RNA to 5% of that in HIV-1 virus. Replacement of the existing HIV-1LAI envelope protein with that of HIV-1MN has ensured that immune responses to the particles are relevant to those against the majority of HIV-1 clade B isolates. In addition to these changes in particle composition, yields of the modified particles were increased using a superior method of inducing the expression construct promoter, and an effective scheme for particle purification was developed. Immunization of non-human primates demonstrated that the particles were capable of generating anti-HIV-1 neutralizing antibodies. The technological refinements reported here will permit retrovirus-like particles to be tested safely in humans, and the change in envelope proteins should allow a more realistic evaluation of the immunogenicity of these particles. Experience gained in engineering these refinements will greatly facilitate other modifications that may be required to achieve maximum efficacy as a vaccine against HIV-1.

Particle size determinants in the human immunodeficiency virus type 1 Gag protein

The retroviral Gag protein plays the central role in the assembly process and can form membrane-enclosed, virus-like particles in the absence of any other viral products. These particles are similar to authentic virions in density and size. Three small domains of the human immunodeficiency virus type 1 (HIV-1) Gag protein have been previously identified as being important for budding. Regions that lie outside these domains can be deleted without any effect on particle release or density. However, the regions of Gag that control the size of HIV-1 particles are less well understood. In the case of Rous sarcoma virus (RSV), the size determinant maps to the CA (capsid) and adjacent spacer sequences within Gag, but systematic mapping of the HIV Gag protein has not been reported. To locate the size determinants of HIV-1, we analyzed a large collection of Gag mutants. To our surprise, all mutants with defects in the MA (matrix), CA, and the N-terminal part of NC (nucleocapsid) sequences produced dense particles of normal size, suggesting that oncoviruses (RSV) and lentiviruses (HIV-1) have different size-controlling elements. The most important region found to be critical for determining HIV-1 particle size is the p6 sequence. Particles lacking all or small parts of p6 were uniform in size distribution but very large as measured by rate zonal gradients. Further evidence for this novel function of p6 was obtained by placing this sequence at the C terminus of RSV CA mutants that produce heterogeneously sized particles. We found that the RSV-p6 chimeras produced normally sized particles. Thus, we present evidence that the entire p6 sequence plays a role in determining the size of a retroviral particle.

Induction of HIV type 1 neutralizing and env-CD4 blocking antibodies by immunization with genetically engineered HIV type 1-like particles containing unprocessed gp160 glycoproteins

Genetically engineered, noninfectious HIV-1-like particles containing processed envelope glycoproteins represent potential candidate immunogens for a vaccine against HIV-1. However, since the gp120 glycoprotein is known to be rapidly lost from the surface of infected cells and purified virions as a result of its low-affinity interaction with gp41, shedding of this extracellular subunit could compromise the immunogenic potential of particle-based HIV-1 vaccine candidates. In this study, we demonstrate for the first time the feasibility of producing fully assembled HIV-1-like particles containing only unprocessed gp160 glycoproteins. Monkey kidney Vero cells were transfected with an inducible, human metallothionein-based expression vector containing most of the HIV-1LAI coding sequences that were genetically modified to introduce safety mutations and destroy the major cleavage site of the HIV-1 envelope glycoprotein. A stably-transfected cell line was isolated and shown to secrete HIV-1-like particles containing unprocessed gp160. Immunization with these particles induced HIV-1 cross-neutralizing, syncytium-inhibiting and env-CD4 blocking antibodies. Thus, these novel HIV-1-like particles represent alternative candidate immunogens for the development of a particle-based AIDS vaccine.

Expression and characterization of genetically engineered human immunodeficiency virus-like particles containing modified envelope glycoproteins: implications for development of a cross-protective AIDS vaccine

Noninfectious human immunodeficiency virus type 1 (HIV-1) viruslike particles containing chimeric envelope glycoproteins were expressed in mammalian cells by using inducible promoters. We engineered four expression vectors in which a synthetic oligomer encoding gp120 residues 306 to 328 (amino acids YNKRKRIHIGP GRAFYTTKNIIG) from the V3 loop of the MN viral isolate was inserted at various positions within the endogenous HIV-1LAI env gene. Expression studies revealed that insertion of the heterologous V3(MN) loop segment at two different locations within the conserved region 2 (C2) of gp120, either 173 or 242 residues away from the N terminus of the mature subunit, resulted in the secretion of fully assembled HIV-like particles containing chimeric LAI/MN envelope glycoproteins. Both V3 loop epitopes were recognized by loop-specific neutralizing antibodies. However, insertion of the V3(MN) loop segment into other regions of gp120 led to the production of envelope-deficient viruslike particles. Immunization with HIV-like particles containing chimeric envelope proteins induced specific antibody responses against both the autologous and heterologous V3 loop epitopes, including cross-neutralizing antibodies against the HIV-1LAI and HIV-1MN isolates. This study, therefore, demonstrates the feasibility of genetically engineering optimized HIV-like particles capable of eliciting cross-neutralizing antibodies.

Binding of erythroid and non-erythroid nuclear proteins to the silencer of the human epsilon-globin-encoding gene

To clarify the molecular mechanisms involved in the developmental control of hemoglobin-encoding genes we have been studying the expression of these genes in human cells in continuous culture. We have previously reported the presence of a transcriptional control element with the properties of a silencer extending from -392 to -177 bp relative to the cap site of the human epsilon-globin-encoding gene [Cao et al., Proc. Natl. Acad. Sci. USA 86 (1989) 5306-5309]. We also showed that this silencer has stronger inhibitory activity in HeLa cells, as compared to K562 human erythroleukemia cells. Using deletion mutants and cis-cloned synthetic oligodeoxyribonucleotides in transient expression assays, nucleotide sequences responsible for this effect have now been further delimited to 44 bp located from -294 to -251 bp. Gel electrophoresis mobility shift assays and DNaseI footprinting assays demonstrate that these negative regulatory sequences are recognized differently by proteins present in nuclear extracts obtained from HeLa and K562 cells. Two binding proteins are detected in K562 nuclear extracts, while only one is found in extracts from HeLa cells. Possible mechanisms by which these proteins may regulate transcription of the epsilon-globin-encoding gene in erythroid and non-erythroid cells are discussed.

Strategy for developing a genetically-engineered whole-virus vaccine against HIV

The production of genetically-engineered, noninfectious virions of human immunodeficiency virus (HIV) represents a novel approach to the development of a safe and effective vaccine for the acquired immune deficiency syndromes (AIDS). Insofar as preparations of inactivated simian immunodeficiency virus (SIV) are now demonstrating protection in immunization-challenge studies in rhesus monkeys, a safe preparation of noninfectious HIV virions produced in a genetically-engineered cell line becomes a logical candidate vaccine for studies in humans. These particles, or pseudovirions, offer distinct advantages over the use of inactivated HIV for human AIDS vaccines. Guarantees of safety without the requirement for inactivation and their potential for structural modification for the modulation of immunogenicity are compelling reasons for the acceptance of HIV pseudovirions as a candidate vaccine in humans.

Production of immunogenic HIV-1 viruslike particles in stably engineered monkey cell lines

A proviral fragment from human immunodeficiency virus type 1 (HIV-1) (LAV-1BRU) containing only protein-coding information, was expressed in COS cells using constitutive promoters in transient and stable transfection experiments. The presence of viruslike particles in cell supernatants was verified by Western blot analysis, density gradient centrifugation, and electron microscopy. Transfection of Vero cells with a similar construct employing the human metallothionein promoter led to the isolation of stable cell lines exhibiting inducible viruslike particle expression in response to cadmium chloride treatment. Induction ratios for viruslike particle expression were in excess of 1000-fold with production levels of p24 core antigen as high as 0.6 mg/L per 24 h. HIV-1 viruslike particles were immunogenic in mice, leading to strong envelope and core-specific humoral responses after two immunizations. The development of stable cell lines expressing significant quantities of HIV-1 viruslike particles offers an alternative to the use of live virus vectors for the production and evaluation of particle-based AIDS vaccines.

Trans-activation of human globin genes by HTLV-I tax1

We studied the effects of a known retroviral trans-activating factor, HTLV-I tax1, on transcription of human globin genes. Transfection of HeLa cells by the cloned tax1 gene stimulated activity of both the beta- and epsilon-globin promoters approximately 20-fold, as measured by chloramphenicol acetyl transferase (CAT) assays. Studies of promoter 5'-deletion mutants revealed that the trans-activation response required only 185 base pairs (bp) of beta-globin 5'-flanking sequence or 177 bp of epsilon-globin 5' flanking sequence. These promoter regions contain either two (for beta) or three (for epsilon) copies of the pentanucleotide sequence CTGAC, which is characteristic of previously described tax1-responsive promoters. We also stably transfected tax1 into the erythroid cell line K562. Transfectants expressing tax1 showed increased transcription of epsilon-, gamma-, zeta-, and alpha-globins. This indicates that tax1 can stimulate transcription of globin genes in their native chromosomal location. This was confirmed by measurements of increases in intracellular hemoglobin as determined by an increased percentage of cells staining with benzidine and by spectrophotometric measurements of hemoglobin. The observed trans-activation of globin genes by tax1 may provide insight into normal regulation of globin genes by clarifying cis regulatory sequences. Furthermore, it suggests that the trans-acting effects of tax1 on heterologous genes are more widespread than was previously appreciated.

A common protein binds to two silencers 5' to the human beta-globin gene

The temporal sequence of expression of human globin genes during development suggests precise regulation of these genes. Recent studies have characterized a number of DNA sequences within or flanking the human beta-globin gene which are important in its regulation and several proteins which bind to these sequences have been identified. We have found two proteins which bind 5' to the human beta-globin gene. One of these proteins, which we designate BP1, binds to two sequences, one between -550 and -527 bp relative to the cap site, the other between -302 and -294 bp. A second protein, BP2, binds to sequences between -275 and -263 bp. The binding sites for both BP1 and BP2 are in two regions which function as silencers in a transient expression assay using the human erythroleukemia cell line K562. These results and others presented here suggest that BP1 may act as a repressor protein. Negative regulation seems to be an important component of tissue and developmental specific globin gene regulation.

Identification of a transcriptional silencer in the 5'-flanking region of the human epsilon-globin gene

We have studied the 5'-flanking sequences required for the transcriptional regulation of human epsilon-globin gene expression. A series of deletion mutants of the human epsilon-globin gene 5'-flanking sequences were constructed and linked to the bacterial chloramphenicol acetyltransferase gene. Expression of these constructs was tested in HeLa cells and the human erythroleukemia K-562 cells. By measuring chloramphenicol acetyltransferase activities and mRNA levels we found that the sequence between -177 and -392 base pairs (bp) relative to the mRNA initiation site exerts a negative effect on epsilon-globin promoter activity. This effect is more pronounced in HeLa cells compared with K-562 cells. To further characterize the negative control region we cloned the DNA sequence between -177 and -392 bp either 5' or 3' of the epsilon-globin promoter and in either orientation. Our data indicate that this negative control region inhibits the epsilon-globin promoter activity in a position- and orientation-independent manner, thus suggesting that it is a silencer. In addition, the silencer also inhibits the expression from the Herpesvirus thymidine kinase promoter. Sequence comparison reveals that there are three short regions within the silencer that share extensive homology with those found in other negative control DNA elements. Our results therefore indicate that an upstream silencer element is present in the epsilon-globin gene and that it may play an important role in the control of epsilon-globin gene expression during development.

Activation of the human epsilon- and beta-globin promoters by SV40 T antigen

We have studied the effect of the SV40 T antigen on expression from human globin promoters fused to the bacterial chloramphenicol acetyltransferase (CAT) gene and compared its effect with the SV40 enhancer and the adenovirus E1A protein. We have observed that expression of p epsilon GLCAT and p beta GLCAT (the epsilon-globin or beta-globin promoter linked to the CAT gene) was significantly stimulated when cotransfected with a cloned T antigen plasmid into CV-1 cells, indicating that trans-activation of the globin promoters was mediated by SV40 T antigen. Transfection of the p beta GLCAT-SV (p beta GLCAT containing the SV40 enhancer element) into CV-1 cells resulted in a 50-60-fold increase in CAT activity as compared to p beta GLCAT (no enhancer). However, cotransfection of the p beta GLCAT-SV with the cloned T antigen resulted in an additional increase of CAT expression, which suggests that T antigen and the SV40 enhancer activate globin gene expression independently. We found that T antigen but not E1A could further stimulate the expression of an enhancer-containing plasmid in CV-1 cells; whereas E1A but not T antigen could further stimulate p epsilon GLCAT expression in COS-1 cells which constitutively express the SV40 T antigen. These results suggest that T antigen and E1A also act independently. Deletion analysis showed that the minimum sequence required for a detectable level of stimulation of the epsilon-globin promoter by T antigen is 177 bp 5' to the cap site, suggesting that the target sequences for response to T antigen do not reside in the canonical 100 bp promoter region, but rather reside in sequences further upstream, and therefore the cellular factors interacting with T antigen are not the TATA or CAT box binding proteins, but the proteins interacting with upstream regulatory sequences.

Nuclease hypersensitivity in the beta-globin gene region of K562 cells

We have investigated chromatin structure in the beta-globin gene region of the K562 human erythroleukemic cell line by using S1 and DNase I nuclease sensitivity assays. Despite the lack of beta-globin gene expression in these cells, we find nuclease-hypersensitive sites to these enzymes in its 5' and 3' flanking regions in K562 chromatin. This result is in contrast to previous reports in which no hypersensitive sites were found in the immediate vicinity of this gene. In the 3' region, one major hypersensitive site at 0.9 kpb 3' and three minor hypersensitive sites at 0.7 kbp, 0.5 kbp 3' and 0.2 kbp 5' of the polyadenylation site were observed; these sites are very similar to those found in fetal liver and adult bone marrow cells in which the beta-globin gene is expressed. We find hypersensitive sites to both enzymes in the 5' region of the beta-globin gene: a major site 0.8 kbp 5' to the cap site, and two minor sites 1.2 and 1.5 kbp 5' to the cap site. The -0.8 kbp site is also present in plasmids containing the beta-globin gene. Our results suggest that the lack of beta-globin gene expression may be related to the lack of hypersensitivity sites in the immediate (150 bp) 5' flanking region of the beta-globin gene, as occurs in other active globin genes.