The Objective Measurement of Mental Stability

The studies here reported are concerned with the application of some of the techniques of measurement to problems of mental health. They constitute the preliminary steps in a programme of research that envisages: (i) the possibility of assisting mental diagnosis by means of objective experimentation, the purpose of which is to isolate variables in personality that are significant in their relationships to degrees of mental stability; (ii) the functional interpretation of these variables; (iii) the employment of any quantitative criteria that can be thus established, in demonstrating the influence of therapeutic and positive mental hygiene programmes.

Lack of effect of chronic ketamine administration on depression-like behavior and frontal cortex autophagy in female and male ICR mice

The acute antidepressant effects of ketamine provide hope for the development of a fast acting approach to treat depression but the consequences of chronic treatment with ketamine are still unclear. One theory regarding the acute effect is that ketamine acts through activation of mTOR but chronic activation of mTOR may lead to reduced autophagy and reduced autophagy could have negative consequences on neuronal plasticity and survival and on affect. To study the interaction between chronic ketamine administration, autophagy and depression the present study tested the effects of 3 weeks daily administration of 5 or 10mg/kg ketamine in both female and male ICR mice on behavior in the open field and the forced swim test and on frontal cortex levels of beclin-1 and p62, two proteins that serve as markers of autophagy. The results show that acute administration of ketamine results in an antidepressant-like effect in the FST, chronic ketamine had no effects in the behavioral tests. There was no difference in the acute or chronic groups between female and male mice. Additionally, chronic ketamine did not alter frontal cortex levels of autophagy markers. The present study suggests that in ICR mice, chronic ketamine does not have the same clear effects that are seen after acute treatment. The lack of difference between females and males and the lack of effects on autophagy after chronic treatment is discussed.

Diagnosis of neuronal ceroid lipofuscinosis (Batten disease) by electron microscopy in peripheral blood specimens

Neuronal ceroid lipopofuscinosis (Batten disease, NCL) represents a group of common childhood neurodegenerative diseases with a shared feature of deposition of abnormal metabolic products in neurons and other tissues, including peripheral blood lymphocytes. In most forms of NCL no specific enzyme defect is known and the diagnosis relies primarily on ultrastructural identification of characteristic membrane-bound inclusions containing the abnormal metabolic product. All buffy-coat specimens examined during a 7-year period (1997-2004) for the exclusion or confirmation of the diagnosis NCL were reviewed. From a total of 265 samples, 9 were inadequate and NCL was diagnosed in 56. Five showed granular osmophilic deposits of infantile Batten disease (NCL1), 10 showed curvilinear profiles of classical late infantile Batten disease (NCL2), and 17 showed vacuolated lymphocytes with fingerprint profiles, indicating classical juvenile Batten disease (NCL3). 24 samples (43%) demonstrated compact electron-dense deposits with fingerprint profiles in the absence of vacuolated lymphocytes, indicative of variant forms NCL. Ultrastructual examination of peripheral blood allows reliable and specific diagnosis of subtypes of Batten disease, including variants, and is a useful, minimally invasive test for the diagnosis of NCL in childhood.

Spot 14 gene deletion increases hepatic de novo lipogenesis

Previous studies have investigated the relationship between the Spot 14 gene and hepatic lipogenesis. Those studies found that the Spot 14 protein was induced when lipogenesis was induced and suggested that induction of the Spot 14 protein was required for induction of hepatic lipogenesis by thyroid hormone and dietary carbohydrate. Analysis of those findings led us to hypothesize that the Spot 14 gene is required for induced hepatic de novo lipogenesis in vivo. To test this hypothesis, we created an in vivo deletion of the Spot 14 gene in mice using gene-targeting technology. Southern blot analysis showed that the Spot 14 gene was disrupted. Northern blot analysis showed that this disruption ablated expression of intact hepatic Spot 14 mRNA. In contrast to our hypothesis, acute thyroid hormone administration led to comparable induction of hepatic lipogenic enzyme mRNAs between the wild-type and knockout mice. Furthermore, long-term treatment with both thyroid hormone and a diet promoting lipogenesis led to enhanced lipogenic enzyme activity and a greater rate of hepatic de novo lipogenesis in the knockout, compared with the wild-type, mice. Although these data indicate that the Spot 14 protein is not required for induced hepatic de novo lipogenesis, they also suggest that Spot 14 plays some role in this process. It is possible that alternative pathways that complement the loss of the Spot 14 protein are present, and in the absence of Spot 14, these alternative pathways overcompensate to produce an enhanced rate of induced lipogenesis.

Thyroid hormones and the brain

Significant progress has been made over the past 2 decades toward understanding the molecular basis of thyroid hormone action. It is now widely accepted that thyroid hormones play predominantly a nuclear role and function by regulating the transcription of specific target genes. Understanding thyroid hormone action at the tissue and organismic level requires assessment of the thyroid hormone response apparatus and identification of specific target genes. Progress toward uncovering the molecular basis of thyroid hormone action during mammalian brain development is advancing rapidly. This commentary provides a brief overview of the molecular basis of thyroid hormone action followed by three sections detailing thyroid hormone regulation of brain development at the functional, cellular, and molecular levels. Each section is followed by a discussion of unresolved issues and an analysis of our current level of understanding of each topic.

Nursing and genetics: a feminist critique moves us towards transdisciplinary teams

Genetic information and technologies are increasingly important in health care, not only in technologically advanced countries, but world-wide. Several global factors promise to increase future demand for morally conscious genetic health services and research. Although they are the largest professional group delivering health care world-wide, nurses have not taken the lead in meeting this challenge. Insights from feminist analysis help to illuminate some of the social institutions and cultural obstacles that have impeded the integration of genetics technology into the discipline of nursing. An alternative model is suggested--the transdisciplinary model--which was developed initially by a nurse and introduced in the 1970s into the delivery of health care and social services for children with developmental disabilities. This holistic model enables all health care professionals to have an equal voice in determining how genetic health care will be globalized.

Protective efficacy of recombinant Yersinia outer proteins against bubonic plague caused by encapsulated and nonencapsulated Yersinia pestis

To evaluate the role of Yersinia outer proteins (Yops) in conferring protective immunity against plague, six yop loci from Yersinia pestis were individually amplified by PCR, cloned, and expressed in Escherichia coli. The recombinant proteins were purified and injected into mice. Most Yop-vaccinated animals succumbed to infection with either wild-type encapsulated Y. pestis or a virulent, nonencapsulated isogenic variant. Vaccination with YpkA significantly prolonged mean survival time but did not increase overall survival of mice infected with the nonencapsulated strain. The only significant protection against death was observed in YopD-vaccinated mice challenged with the nonencapsulated strain.

Lactate dehydrogenase-elevating virus variants: cosegregation of neuropathogenicity and impaired capability for high viremic persistent infection

Neuropathogenic isolates of lactate dehydrogenase virus (LDV) differ from non-neuropathogenic isolates in their unique ability to cause a paralytic disease (age-dependent poliomyelitis, ADPM) in immunosuppressed C58 and AKR mice by cytocidally infecting their anterior horn neurons. We have recently reported that an original neuropathogenic LDV isolate, LDV-C-BR, contained a low level of a coexisting non-neuropathogenic LDV which, in a mixed infection of mice, rapidly outcompeted the former resulting in apparent loss of neuropathogenicity of the reisolated LDV. This correlated with an impaired ability of the neuropathogenic LDV to establish a viremic persistent infection. In the present study we identified the presence of three different quasispecies in another original neuropathogenic LDV by sequence analysis of cDNA clones of ORF 5 (encoding the primary envelope glycoprotein VP-3P) obtained from the isolate. Successful development of differential reverse transcription-polymerase chain reaction assays allowed us to biologically clone all three quasispecies through repeated end point dilutions. Only one of the quasispecies (LDV-v) was neuropathogenic. The other two, LDV-vP (probably the same as LDV-P) and LDV-vx (a novel LDV quasispecies that had not been previously identified), were non-neuropathogenic and found to be the common LDV quasispecies associated with almost all LDVs originally isolated from mice carrying various other transplantable tumors. The neuropathogenic LDV-v became selectively amplified in the spinal cords of paralyzed mice, but possessed an impaired ability to establish a persistent viremic infection and was rapidly out-competed by LDV-vP and LDV-vx in mixed infections, just as reported previously for LDV-C-BR. The results further support our hypothesis that neuropathogenicity and impaired capability for viremic persistence of LDV are determined by the same molecular feature. The only consistent and biologically relevant molecular difference we have observed between neuropathogenic and non-neuropathogenic LDVs is the number of polylactosaminoglycan chains associated with the ectodomain of VP-3P.

Protection against experimental bubonic and pneumonic plague by a recombinant capsular F1-V antigen fusion protein vaccine

The current human whole-cell vaccine is ineffective against pneumonic plague caused by typical F1 capsule positive (F1+) strains of Yersinia pestis. The authors found this vaccine to also be ineffective against F1-negative (F1-) Y. pestis strains, which have been isolated from a human case and from rodents. For these reasons, the authors developed a recombinant vaccine composed of a fusion protein of F1 with a second protective immunogen, V antigen. This vaccine protected experimental mice against pneumonic as well as bubonic plague produced by either an F1+ or F1- strain of Y. pestis, gave better protection than F1 or V alone against the F1+ strain, and may provide the basis for an improved human plague vaccine.

Comparative efficacy of experimental anthrax vaccine candidates against inhalation anthrax in rhesus macaques

The authors examined the efficacy of Bacillus anthracis protective antigen (PA) combined with adjuvants as vaccines against an aerosol challenge of virulent anthrax spores in rhesus macaques. Adjuvants tested included i) aluminum hydroxide (Alhydrogel), ii) saponin QS-21 and iii) monophosphoryl lipid A (MPL) in squalene/lecithin/Tween 80 emulsion (SLT). Animals were immunized once with either 50 micrograms of recombinant PA plus adjuvant, or with Anthrax Vaccine Adsorbed (AVA), the licensed human anthrax vaccine. The serological response to PA was measured by enzyme linked immunosorbent assay. Lymphocyte proliferation and serum neutralization of in vitro lethal toxin cytotoxicity were also assayed. In all vaccine groups, anti-PA IgM and IgG titers peaked at 2 weeks and 4-5 weeks postimmunization, respectively. Five weeks postimmunization, animals in all vaccine groups demonstrated PA-specific lymphocyte proliferation and sera that neutralized in vitro cytotoxicity. Six weeks after immunization, the animals were challenged by aerosol with approximately 93 LD50 of virulent anthrax spores. Animals were bled daily for 1 week to monitor bacteremia, and deaths were recorded. Anti-PA ELISA titers in all groups of immunized animals were substantially increased 2 weeks after challenge. One dose of each vaccine provided significant protection (> 90%) against inhalation anthrax in the rhesus macaques.

Chicken ovalbumin upstream promoter-transcription factor (COUP-TF) modulates expression of the Purkinje cell protein-2 gene. A potential role for COUP-TF in repressing premature thyroid hormone action in the developing brain

The cerebellar Purkinje cell-specific PCP-2 gene is transcriptionally activated by thyroid hormone during the 2nd and 3rd weeks of postnatal life in the rat. In contrast, thyroid hormone has no detectable effects on PCP-2 expression in the fetal rat. We now present data that suggest that the orphan nuclear receptor chicken ovalbumin upstream promoter-transcription factor (COUP-TF) represses triiodothyronine (T3)-dependent transcriptional activation of PCP-2 in the immature Purkinje cell. Gel shift assays show that the PCP-2 A1TRE and adjoining sequences (-295/-199 region) bind to rat and mouse brain nucleoproteins in a developmentally regulated fashion and that one of these nucleoproteins could be the orphan nucleoprotein COUP-TF. In support of this hypothesis, in vitro translated COUP-TF binds to the -295/-199 region and COUP-TF represses T3-dependent activation of the PCP-2 promoter in transient transfection analyses. Finally, immunohistochemical studies reveal that COUP-TF is specifically expressed in the immature fetal and early neonatal Purkinje cell and that this expression diminishes coincident with thyroid hormone induction of PCP-2 expression. Our findings are consistent with the hypothesis that the presence or absence of inhibitory proteins bound to the thyroid hormone response element of T3-responsive genes governs the responsivity of these genes to thyroid hormone during brain development.

Short- and long-term efficacy of single-dose subunit vaccines against Yersinia pestis in mice

A single, subcutaneous, 30-microg dose of either a combination of the Yersinia pestis proteins F1+V or a F1-V fusion protein adsorbed to the adjuvant aluminum hydroxide, protected Hsd:ND4 mice for one year against pneumonic plague. The recombinant F1+V vaccine provided significant protection as early as day 14 postimmunization. The current Plague Vaccine USP in a single 0.2-ml dose did not provide significant protection in this mouse model. Antibody titers to F1 and V peaked at approximately 5-12 weeks postimmunization and were still detectable one year later. These F1 and V subunit vaccines may offer effective long-term immunity with a reduced dosage schedule when compared with the presently licensed, formalin-killed, whole-cell vaccine.

Analysis of the Yersinia pestis V protein for the presence of linear antibody epitopes

The V protein expressed by pathogenic Yersinia pestis is an important virulence factor and protective immunogen. The presence of linear B-cell epitopes in the V protein was investigated by using a series of 17 overlapping linear peptides. Groups of 10 mice were immunized intraperitoneally with 30 microg of each peptide on days 0, 30, and 60. Although the V protein-specific antibody response to the peptides varied, most of the peptides elicited high antibody titers. The immunized mice were challenged subcutaneously with 60 50% lethal doses (LD50) (1 LD50 = 1.9 CFU) of a virulent Y. pestis strain, CO92. None of the peptide-immunized mice survived challenge. The animals immunized with the V protein were completely protected against challenge. The immunogenicity of some of the V peptides was increased by conjugating them to keyhole limpet hemocyanin. Only one peptide (encompassing amino acids 1 to 30) conjugate demonstrated some protection; the others were not protective. In additional experiments, V peptides that reacted well with sera from mice surviving Y. pestis infection were combined and used to immunize mice. Although the combined peptides appeared to be very immunogenic, they were not protective. Therefore, the protective B-lymphocyte epitope(s) in the V protein is most likely to be conformational.

Gallium arsenide metal-semiconductor-metal photodiodes as optoelectronic mixers for microwave single-sideband modulation

Gallium arsenide (GaAs) metal-semiconductor-metal (MSM) photodetectors have unique properties including high-bandwidth, linearity, and biphase response that make them suitable as mixers and programmable weights for microwave and communications applications. An optical technique for microwave single-sideband modulation that uses GaAs MSM photodiodes as mixers is reported. It uses MSM Schottky photodiodes formed in a GaAs/Al(0.3)Ga(0.7)As materials system to detect microwave in-phase and quadrature signals on optical carriers. Modulation of the photodetector bias voltages results in a single-sideband modulation of the microwave signal. Radio frequency and undesired-sideband suppression of 36 and 27 dB, respectively, were achieved. The optical wavelength was 850 nm, and the bandwidth of the photodetectors was > or = 29 GHz.

Purkinje cell protein-2 cis-elements mediate repression of T3-dependent transcriptional activation

Previous studies in our laboratory show that triiodothyronine upregulates expression of the cerebellar Purkinje cell-specific gene Pcp-2 during the first 2 weeks of rat neonatal life. A specific thyroid hormone response element, the A1 TRE, mediates this regulation. The finding that the contiguous 68 bases (-267/ -199) of the Pcp-2 promoter 3' to the A1 TRE repressed T3 response in transactivation studies suggested that this sequence could play a role in preventing premature T3-dependent activation of Pcp-2 in the fetus. We now show that deletion of this region resulted in enhanced T3-dependent activation of the native Pcp-2 promoter. The sequence is not a generalized silencer since it does not alter basal activity of mouse mammary tumor virus (MMTV) or thymidine kinase (TK) promoters. Deletion and linker scanning studies indicate that the 5' 30 bases of the -267/ -199 region mediate most of the response silencing activity. The -267/ -199 region also attenuates T3-induced transactivation mediated by other TREs. Gel shift analysis reveals that nuclear proteins from fetal but not adult brains complex with the -267/ -199 region, supporting the hypothesis that this region binds proteins that suppress Pcp-2 expression early in brain development.

Protection of mice from fatal bubonic and pneumonic plague by passive immunization with monoclonal antibodies against the F1 protein of Yersinia pestis

Monoclonal antibodies (MAbs) to the fraction 1 (F1) protein of Yersinia pestis protected mice against fatal pneumonic as well as bubonic plague from wild-type F1+ organisms. The rare isolation of a virulent F1- isolate from surviving animals supports earlier studies suggesting that improved vaccines should consist of immunogens to protect against F1- variants. The high degree of protection with IgG MAb suggests that secretory IgA is not required for protection from pneumonic plague.

Coexistence in lactate dehydrogenase-elevating virus pools of variants that differ in neuropathogenicity and ability to establish a persistent infection

Neuropathogenic isolates of lactate dehydrogenase-elevating virus (LDV) differ from nonneuropathogenic isolates in their unique ability to infect anterior horn neurons of immunosuppressed C58 and AKR mice and cause paralytic disease (age-dependent poliomyelitis [ADPM]). However, we and others have found that neuropathogenic LDVs fail to retain their neuropathogenicity during persistent infections of both ADPM-susceptible and nonsusceptible mice. On the basis of a segment in open reading frame 2 that differs about 60% between the neuropathogenic LDV-C and the nonneuropathogenic LDV-P, we have developed a reverse transcription-PCR assay that distinguishes between the genomes of the two LDVs and detects as little as 10 50% infectious doses (ID50) of LDV. With this assay, we found that LDV-P and LDV-C coexist in most available pools of LDV-C and LDV-P. For example, various plasma pools of 10(9.5) ID50 of LDV-C/ml contained about 10(5) ID50 of LDV-P/ml. Injection of such an LDV-C pool into mice of various strains resulted in the rapid displacement in the circulation of LDV-C by LDV-P as the predominant LDV, but LDV-C also persisted in the mice at a low level along with LDV-P. We have freed LDV-C of LDV-P by endpoint dilution (LDV-C-EPD). LDV-C-EPD infected mice as efficiently as did LDV-P, but its level of viremia during the persistent phase was only 1/10,000 that observed for LDV-P. LDV-permissive macrophages accumulated and supported the efficient replication of superinfecting LDV-P. Therefore, although neuropathogenic LDVs possess the unique ability to infect anterior horn neurons of ADPM-susceptible mice, they exhibit a reduced ability to establish a persistent infection in peripheral tissues of mice regardless of the strain. The specific suppression of LDV-C replication in persistently infected mice is probably due in part to a more efficient neutralization of LDV-C than LDV-P by antibodies to the primary envelope glycoprotein, VP-3P. Both neuropathogenicity and the higher sensitivity to antibody neutralization correlated with the absence of two of three N-linked polylactosaminoglycan chains on the ca. 30-amino-acid ectodomain of VP-3P, which seems to carry the neutralization epitope(s) and forms part of the virus receptor attachment site.

Planar, Al0.3Ga0.7As-passivated-base, heterojunction bipolar phototransistors

New planar GaAs heterojunction bipolar phototransistors have been designed and demonstrated. The devices use a GaAs/Al(0.3)Ga(0.7) As molecular-beam-epitaxy materials system with an Al(0.3)Ga(0.7) As passivated, 10-nm-thick base; a depleted, high-low emitter; and a low emitter-base capacitance. Electrical contact to the emitter is made by a set of parallel, ohmic fingers and to the collector by an ohmic contact formed in a large, approximately 1.48-microm deep via. Rise times in response to impulse optical excitation at 810 nm were 747-891 ps except at the two lowest optical excitation powers measured. Photocurrent gains measured at 810 and 850 nm were 0.67-19, depending on experimental conditions. These devices are promising for use in heterodyne photodetector arrays for coherent optical processing channelizers requiring a 100-MHz bandwidth.

Effects of dietary crude protein, breed, parity, and health status on the fertility of dairy cows

A study was conducted to determine the impact of dietary CP (13% vs. 20%), parity (first vs. second lactation or later), and breed (Holstein vs. Jersey) on the reproductive efficiency of dairy cows. Sixty-four cows were blocked by parity and breed and assigned to one of two treatments. Cows were removed from treatments on d 100 or 120 depending on pregnancy status. Cows were categorized by health status based on the occurrence of postparturient disorders. Plasma urea N concentrations were influenced by diet (8.6 vs. 21 mg/dl, 13 and 20% CP, respectively), parity, and breed. Reproductive indices were not influenced by diet except that days to first estimated ovulation increased for cows fed the 20% CP diet when health status was added to the model. Days to first observed estrus, first AI service, and cumulative pregnancy rate were affected by health status. Regression analysis for survival showed an interaction of diet and health status for days open. High CP diets tended to increase days open when cows had major health problems; otherwise, a high CP diet decreased days open. The implementation of a strict reproductive management program allowed high reproductive efficiency goals to be achieved regardless of plasma urea N concentrations.

Recombinant V antigen protects mice against pneumonic and bubonic plague caused by F1-capsule-positive and -negative strains of Yersinia pestis

The purified recombinant V antigen from Yersinia pestis, expressed in Escherichia coli and adsorbed to aluminum hydroxide, an adjuvant approved for human use, was used to immunize outbred Hsd:ND4 mice subcutaneously. Immunization protected mice from lethal bubonic and pneumonic plague caused by CO92, a wild-type F1+ strain, or by the isogenic F1- strain C12. This work demonstrates that a subunit plague vaccine formulated for human use provides significant protection against bubonic plague caused by an F1- strain (C12) or against substantial aerosol challenges from either F1+ (CO92) or F1-(C12) Y. pestis.

The evolution and status of genetics education in nursing in the United States 1983-1995

Despite rapid advances in genetic diagnosis and gene therapy, only a few nurses are addressing the need for widespread dissemination of genetic information. A critical question is: How long will nurses be able to maintain high-quality care and contend with the conundrums of genopathic medicine? The purpose of this state-of-the-science paper is to trace progress in nursing education in genetics and to recommend curriculum change. A recurrent theme-the need for knowledge-is found in nursing studies and national forums in genetics. Genetic knowledge for nurses should be a priority.

Fraction 1 capsular antigen (F1) purification from Yersinia pestis CO92 and from an Escherichia coli recombinant strain and efficacy against lethal plague challenge

As a first step in formulating an improved plague vaccine, we developed a simple purification strategy that produced high yields of pure cell-associated and culture supernatant-derived fraction 1 capsular antigen (F1) from both avirulent Yersinia pestis C092 (Pgm- Lcr-) and an Escherichia coli F1-producing recombinant strain. Cell-associated F1 was partially purified by sequential ammonium sulfate precipitations of a sodium chloride extract of acetone-dried bacteria harvested from broth cultures. Cell-free F1 was precipitated directly from culture supernatants with a single application of 30% ammonium sulfate. By exploiting the aggregative property of F1, large quantities of purified high-molecular-weight F1 species from both cell extracts and supernatants were isolated in the void volume of a preparative gel filtration column. Highly purified, endotoxin-free F1, combined with two different adjuvants, induced very high F1 titers in mice and protected them against either subcutaneous (70 to 100% survival) or aerosol (65 to 84% survival) challenge with virulent organisms. This protection was independent of the source of the antigen and the adjuvant used. F1-induced protection against both subcutaneous and aerosol challenge was also significantly better than that conferred by immunization with the licensed killed whole-cell vaccine. Our results indicate that F1 antigen represents a major protective component of previously studied crude capsule preparations, and immunity to F1 antigen provides a primary means for the host to overcome plague infection by either the subcutaneous or respiratory route.

Differential glycosylation of the ectodomain of the primary envelope glycoprotein of two strains of lactate dehydrogenase-elevating virus that differ in neuropathogenicity

ORF 5 encoding the primary envelope glycoprotein, VP-3P, of a highly neuropathogenic isolate of lactate dehydrogenase-elevating virus (LDV-v) has been sequenced. It exhibits 92% nucleotide identity with the ORF 5 of an LDV isolate that lacks neuropathogenicity, LDV-P, and the amino acid identities of the predicted VP-3Ps of the two strains is 90%. Most striking, however, is the absence in the ectodomain of LDV-v VP-3P of two out of three potential N-glycosylation sites present in the ectodomain of VP-3P of LDV-P. The ectodomain of VP-3P has been implicated to play an important role in host receptor interaction. VP-3P of another neuropathogenic LDV strain, LDV-C, lacks the same two N-glycosylation sites (Godeny et al., 1993). In vitro transcription/translation of the ORFs 5 of LDV-P and LDV-v indicated that all three N-glycosylation sites in the ectodomain of LDV-P VP-3P became glycosylated when synthesized in the presence of microsomal membranes, whereas the glycosylation of the ORF 5 proteins of LDV-v and LDV-C was consistent with glycosylation at a single site. No other biological differences between the neuropathogenic and non-neuropathogenic strains have been detected. They replicate with equal efficiency in mice and in primary macrophage cultures.

Expression of ecotropic murine leukemia virus in the brains of C58/M, DBA2/J, and in utero-infected CE/J mice

In C58 and AKR mice, endogenous N-tropic, ecotropic murine leukemia virus (MuLV) proviruses become activated in rare cells during embryogenesis. Resultant replication-competent progeny viruses then actively infect a large number of cells throughout the fetus, including cells in the developing central nervous system. By in situ hybridization analyses, we have assessed the presence of ecotropic MuLV RNA in the brains of C58 mice as a function of age. Only a few ecotropic MuLV-positive cells were observed in weanling mice, but the number of positive cells in the brain increased progressively with increasing age of the mice. Throughout the lives of the mice, the ecotropic MuLV RNA-positive cells were primarily located in well-defined white-matter tracts of the brain (commissura anterior, corpus callosum, fimbria hippocampi, optical tract, and striatum) and of the spinal cord. Cells of the subventricular zone also expressed ecotropic MuLV RNA, and in older mice a small number of positive cells were present in the grey matter. Infection of endogenous ecotropic MuLV provirus-less CE/J mice in utero with ecotropic MuLV clone AKR-623 resulted in the extensive infection of brain cells. The regional distribution of ecotropic MuLV RNA-containing cells was the same as observed in the brains of C58 mice, in which cells became infected by endogenously activated virus, but the number of positive cells was higher.

Relationship between virulence and immunity as revealed in recent studies of the F1 capsule of Yersinia pestis

Yersinia pestis, the causative agent of plague, possesses multiple virulence determinants encoded on its three plasmids and on its chromosome. We evaluated the role of the protein capsule F1 in virulence an immunity against plague. Strains lacking F1, either those that are naturally occurring or those with genetically defined nonpolar mutations in the structural gene, retained their virulence for mice and nonhuman primates. However, both active immunization with F1, from either a recombinant vector or Y. pestis, and passive immunization with F1 monoclonal antibody protected mice from experimental infection with wild-type F1-positive organisms. These results suggest that protective immunogens like F1 need not be essential for virulence. The rare isolation of virulent F1-negative organisms from F1-immunized animals infected with F1-positive strains supports this conclusion and also suggests that, in addition to F1, an optimal vaccine against plague should include essential virulence factors as immunogens.

C58 and AKR mice of all ages develop motor neuron disease after lactate dehydrogenase-elevating virus infection but only if antiviral immune responses are blocked by chemical or genetic means or as a result of old age

Age-dependent poliomyelitis is a paralytic disease of C58 and AKR mice caused by cytocidal infection of anterior horn neurons with neuropathogenic strains of lactate dehydrogenase-elevating virus (LDV). The motor neurons are rendered LDV-permissive via an unknown mechanism through the expression of ecotropic murine leukemia virus (MuLV) in central nervous system (CNS) glial cells. Only old mice develop paralytic disease after LDV infection, but mice 5-6 months old or older can be rendered susceptible by suppression of anti-LDV immune responses by a single treatment with cyclophosphamide or X-irradiation before LDV infection. Younger mice appeared to be resistant in spite of this immunosuppresive treatment. The present results confirm that mice as young as 1 month of age possess CNS cells expressing ecotropic MuLV and show that these mice are susceptible to paralytic LDV infection provided their anti-LDV immune responses are blocked for an extended period of time by repeated cyclophosphamide treatments or by a genetic defect. Furthermore, old mice become naturally susceptible to paralytic LDV infection because of an impaired ability to mount a motor neuron protective anti-LDV immune response.

Lactate dehydrogenase-elevating virus replication persists in liver, spleen, lymph node, and testis tissues and results in accumulation of viral RNA in germinal centers, concomitant with polyclonal activation of B cells

Lactate dehydrogenase-elevating virus (LDV) replicates primarily and most likely solely in a subpopulation of macrophages in extraneuronal tissues. Infection of mice, regardless of age, with LDV leads to the rapid cytocidal replication of the virus in these cells, resulting in the release of large amounts of LDV into the circulation. The infection then progresses into life-long, asymptomatic, low-level viremic persistence, which is maintained by LDV replication in newly generated LDV-permissive cells which escapes all antiviral immune responses. In situ hybridization studies of tissue sections of adult FVB mice revealed that by 1 day postinfection (p.i.), LDV-infected cells were present in practically all tissues but were present in the highest numbers in the lymph nodes, spleen, and skin. In the central nervous system, LDV-infected cells were restricted to the leptomeninges. Most of the infected cells had disappeared at 3 days p.i., consistent with the cytocidal nature of the LDV infection, except for small numbers in lymph node, spleen, liver, and testis tissues. These tissues harbored infected cells until at least 90 days p.i. The results suggest that the generation of LDV-permissive cells during the persistent phase is restricted to these tissues. The continued presence of LDV-infected cells in testis tissue suggests the possibility of LDV release in semen and sexual transmission. Most striking was the accumulation of large amounts of LDV RNA in newly generated germinal centers of lymph nodes and the spleen. The LDV RNA was not associated with infected cells but was probably associated with virions or debris of infected, lysed cells. The appearance of LDV RNA in germinal centers in these mice coincided in time with the polyclonal activation of B cells, which leads to the accumulation of polyclonal immunoglobulin G2a and low-molecular-weight immune complexes in the circulation.

Lactate dehydrogenase-elevating virus entry into the central nervous system and replication in anterior horn neurons

The initial replication of lactate dehydrogenase-elevating virus (LDV) in mice, its invasion of the central nervous system (CNS) and infection of anterior horn neurons in C58 and AKXD-16 mice were investigated by Northern and in situ hybridization analyses. Upon intraperitoneal injection, LDV replication in cells in the peritoneum was maximal at 8 h post-infection (p.i.). Next, LDV infection was detected in bone marrow cells and then in macrophage-rich regions of all tissues investigated (12 to 24 h p.i.). By 2 to 3 days p.i., LDV RNA-containing cells had largely disappeared from all non-neuronal tissues due to the cytocidal nature of the LDV infection of macrophages. In the CNS at 24 h p.i. LDV replication was very limited and confined to cells in the leptomeninges. LDV replication in the cells of the leptomeninges should result in the release of progeny LDV into the cerebrospinal fluid and thus its dissemination throughout the CNS. However, in C58 and AKXD-16 mice, which are susceptible to paralytic LDV infection, only little LDV RNA and few LDV-infected cells were detectable in the spinal cord until at least 10 days p.i. Extensive cytocidal infection of anterior horn neurons occurred only shortly before the development of paralytic symptoms between 2 and 3 weeks p.i. The reason for the relatively long delay in LDV infection of anterior horn neurons is not known. No LDV RNA or LDV RNA-containing cells were detected in the brain, except in the leptomeninges at early times after infection.

Infection of central nervous system cells by ecotropic murine leukemia virus in C58 and AKR mice and in in utero-infected CE/J mice predisposes mice to paralytic infection by lactate dehydrogenase-elevating virus

Certain mouse strains, such as AKR and C58, which possess N-tropic, ecotropic murine leukemia virus (MuLV) proviruses and are homozygous at the Fv-1n locus are specifically susceptible to paralytic infection (age-dependent poliomyelitis [ADPM]) by lactate dehydrogenase-elevating virus (LDV). Our results provide an explanation for this genetic linkage and directly prove that ecotropic MuLV infection of spinal cord cells is responsible for rendering anterior horn neurons susceptible to cytocidal LDV infection, which is the cause of the paralytic disease. Northern (RNA) blot hybridization of total tissue RNA and in situ hybridization of tissue sections demonstrated that only mice harboring central nervous system (CNS) cells that expressed ecotropic MuLV were susceptible to ADPM. Our evidence indicates that the ecotropic MuLV RNA is transcribed in CNS cells from ecotropic MuLV proviruses that have been acquired by infection with exogenous ecotropic MuLV, probably during embryogenesis, the time when germ line proviruses in AKR and C58 mice first become activated. In young mice, MuLV RNA-containing cells were found exclusively in white-matter tracts and therefore were glial cells. An increase in the ADPM susceptibility of the mice with advancing age correlated with the presence of an increased number of ecotropic MuLV RNA-containing cells in the spinal cords which, in turn, correlated with an increase in the number of unmethylated proviruses in the DNA extracted from spinal cords. Studies with AKXD recombinant inbred strains showed that possession of a single replication-competent ecotropic MuLV provirus (emv-11) by Fv-1n/n mice was sufficient to result in ecotropic MuLV infection of CNS cells and ADPM susceptibility. In contrast, no ecotropic MuLV RNA-positive cells were present in the CNSs of mice carrying defective ecotropic MuLV proviruses (emv-3 or emv-13) or in which ecotropic MuLV replication was blocked by the Fv-1n/b or Fv-1b/b phenotype. Such mice were resistant to paralytic LDV infection. In utero infection of CE/J mice, which are devoid of any endogenous ecotropic MuLVs, with the infectious clone of emv-11 (AKR-623) resulted in the infection of CNS cells, and the mice became ADPM susceptible, whereas littermates that had not become infected with ecotropic MuLV remained ADPM resistant.

Neonatal infection of mice with lactate dehydrogenase-elevating virus results in suppression of humoral antiviral immune response but does not alter the course of viraemia or the polyclonal activation of B cells and immune complex formation

Neonatal infection of FVB mice with lactate dehydrogenase-elevating virus (LDV) prevented the normal formation of anti-LDV antibodies observed in mice infected at 5 days of age or older. Even 22 weeks post-infection, the concentration of circulating anti-LDV antibodies in neonatally infected mice was insignificant. However, the time course and level of persistent viraemia were the same in neonatally infected mice lacking anti-LDV antibodies as in mice infected at 5 or 15 days of age which developed normal antiviral immune responses. The results support the view that LDV replication in mice is unaffected by antiviral immune responses and instead is primarily dependent on the rate of regeneration of LDV-permissive macrophages. This view is further supported by the following findings. Treatment of mice with cyclophosphamide or dexamethasone, which are known to increase plasma LDV levels, increased the proportion of LDV-permissive macrophages in the peritoneum. Injection of mice with interleukin-3, which is known to stimulate macrophage development, increased plasma LDV levels in persistently infected mice 10- to 100-fold. During the first month of age when mice possess a higher proportion of LDV-permissive macrophages than older mice and peritoneal macrophages exhibit self-sustained growth, the persistent plasma LDV titres were also 10- to 100-fold higher than in older mice. The polyclonal activation of B cells induced by LDV that results in a permanent elevation of IgG2a or IgG2b in the circulation, and the formation of 180K to 300K immune complexes containing IgG2a or IgG2b were also the same in neonatally infected mice and mice infected 5 or 15 days after birth. Thus, the polyclonal activation of B cells occurs in the absence of an antiviral humoral immune response and the immune complexes do not contain anti-LDV antibodies. The immune complexes probably consist of autoantibodies formed in the course of the polyclonal activation of B cells and their cellular antigens.