Prediction of estimated risk for bipolar disorder using machine learning and structural MRI features

BACKGROUND

Individuals with bipolar disorder are commonly correctly diagnosed a decade after symptom onset. Machine learning techniques may aid in early recognition and reduce the disease burden. As both individuals at risk and those with a manifest disease display structural brain markers, structural magnetic resonance imaging may provide relevant classification features.

METHODS

Following a pre-registered protocol, we trained linear support vector machine (SVM) to classify individuals according to their estimated risk for bipolar disorder using regional cortical thickness of help-seeking individuals from seven study sites (N = 276). We estimated the risk using three state-of-the-art assessment instruments (BPSS-P, BARS, EPIbipolar).

RESULTS

For BPSS-P, SVM achieved a fair performance of Cohen's κ of 0.235 (95% CI 0.11-0.361) and a balanced accuracy of 63.1% (95% CI 55.9-70.3) in the 10-fold cross-validation. In the leave-one-site-out cross-validation, the model performed with a Cohen's κ of 0.128 (95% CI -0.069 to 0.325) and a balanced accuracy of 56.2% (95% CI 44.6-67.8). BARS and EPIbipolar could not be predicted. In post hoc analyses, regional surface area, subcortical volumes as well as hyperparameter optimization did not improve the performance.

CONCLUSIONS

Individuals at risk for bipolar disorder, as assessed by BPSS-P, display brain structural alterations that can be detected using machine learning. The achieved performance is comparable to previous studies which attempted to classify patients with manifest disease and healthy controls. Unlike previous studies of bipolar risk, our multicenter design permitted a leave-one-site-out cross-validation. Whole-brain cortical thickness seems to be superior to other structural brain features.

Remission with or without comorbid substance use disorders in early psychosis: long-term outcome in integrated care (ACCESS III study)

Introduction

Schizophrenia-Spectrum-Disorders are associated with poor long-term outcome as well as disability and often severely affect the lives of patients and their families often from symptom onset. Up to 70% of first episode psychosis (FEP) patients suffer from comorbid substance use disorders (SUD). We aimed at studying the course of illness in FEP patients within evidence-based care, with and without comorbid SUD, to examine how decreased, remitted or persistent substance use impacted rates of a combined symptomatic and functional long-term recovery compared with patients without SUD.

Methods

ACCESS III is an integrated care model for FEP or patients in the early phase of non-affective and affective psychotic disorders. Treatment trajectories of patients, who had been in ACCESS care for 1 year, with and without SUD were compared with regard to the course of illness and quality of life using Mixed Model Repeated Measures (MMRM) and recovery rates were compared using binary logistic regression. Change in substance use was coded as either persistent, decreased/remitted or no use.

Results

ACCESS III was a prospective 1-year study (N = 120) in patients aged 12-29 years. Of these, 74 (61.6%) had a comorbid SUD at admission. There were no group differences regarding the course of illness between patients with or without comorbid SUD or between patients with a substance abuse or substance dependence. The only outcome parameter that was affected by SUD was quality of life, with larger improvement found in the group without substance use (p = 0.05) compared to persistent and remitted users. Using LOCF, 44 patients (48.9%) fulfilled recovery criteria at the endpoint; recovery did not differ based on substance use status.

Discussion

SUD and especially substance dependence are common in psychotic disorders even in FEP patients. Evidence-based integrated care led to long-term improvement in patients with comorbid SUD and rate of recovery did not differ for patients with substance use.

Association of polygenic score and the involvement of cholinergic and glutamatergic pathways with lithium treatment response in patients with bipolar disorder

Lithium is regarded as the first-line treatment for bipolar disorder (BD), a severe and disabling mental health disorder that affects about 1% of the population worldwide. Nevertheless, lithium is not consistently effective, with only 30% of patients showing a favorable response to treatment. To provide personalized treatment options for bipolar patients, it is essential to identify prediction biomarkers such as polygenic scores. In this study, we developed a polygenic score for lithium treatment response (Li+PGS) in patients with BD. To gain further insights into lithium's possible molecular mechanism of action, we performed a genome-wide gene-based analysis. Using polygenic score modeling, via methods incorporating Bayesian regression and continuous shrinkage priors, Li+PGS was developed in the International Consortium of Lithium Genetics cohort (ConLi+Gen: N = 2367) and replicated in the combined PsyCourse (N = 89) and BipoLife (N = 102) studies. The associations of Li+PGS and lithium treatment response - defined in a continuous ALDA scale and a categorical outcome (good response vs. poor response) were tested using regression models, each adjusted for the covariates: age, sex, and the first four genetic principal components. Statistical significance was determined at P < 0.05. Li+PGS was positively associated with lithium treatment response in the ConLi+Gen cohort, in both the categorical (P = 9.8 × 10-12, R2 = 1.9%) and continuous (P = 6.4 × 10-9, R2 = 2.6%) outcomes. Compared to bipolar patients in the 1st decile of the risk distribution, individuals in the 10th decile had 3.47-fold (95%CI: 2.22-5.47) higher odds of responding favorably to lithium. The results were replicated in the independent cohorts for the categorical treatment outcome (P = 3.9 × 10-4, R2 = 0.9%), but not for the continuous outcome (P = 0.13). Gene-based analyses revealed 36 candidate genes that are enriched in biological pathways controlled by glutamate and acetylcholine. Li+PGS may be useful in the development of pharmacogenomic testing strategies by enabling a classification of bipolar patients according to their response to treatment.

Machine Learning Prediction of Estimated Risk for Bipolar Disorders Using Hippocampal Subfield and Amygdala Nuclei Volumes

The pathophysiology of bipolar disorder (BD) remains mostly unclear. Yet, a valid biomarker is necessary to improve upon the early detection of this serious disorder. Patients with manifest BD display reduced volumes of the hippocampal subfields and amygdala nuclei. In this pre-registered analysis, we used structural MRI (n = 271, 7 sites) to compare volumes of hippocampus, amygdala and their subfields/nuclei between help-seeking subjects divided into risk groups for BD as estimated by BPSS-P, BARS and EPIbipolar. We performed between-group comparisons using linear mixed effects models for all three risk assessment tools. Additionally, we aimed to differentiate the risk groups using a linear support vector machine. We found no significant volume differences between the risk groups for all limbic structures during the main analysis. However, the SVM could still classify subjects at risk according to BPSS-P criteria with a balanced accuracy of 66.90% (95% CI 59.2-74.6) for 10-fold cross-validation and 61.9% (95% CI 52.0-71.9) for leave-one-site-out. Structural alterations of the hippocampus and amygdala may not be as pronounced in young people at risk; nonetheless, machine learning can predict the estimated risk for BD above chance. This suggests that neural changes may not merely be a consequence of BD and may have prognostic clinical value.

Association of Polygenic Score and the involvement of Cholinergic and Glutamatergic Pathways with Lithium Treatment Response in Patients with Bipolar Disorder

Lithium is regarded as the first-line treatment for bipolar disorder (BD), a severe and disabling mental disorder that affects about 1% of the population worldwide. Nevertheless, lithium is not consistently effective, with only 30% of patients showing a favorable response to treatment. To provide personalized treatment options for bipolar patients, it is essential to identify prediction biomarkers such as polygenic scores. In this study, we developed a polygenic score for lithium treatment response (Li+PGS) in patients with BD. To gain further insights into lithium's possible molecular mechanism of action, we performed a genome-wide gene-based analysis. Using polygenic score modeling, via methods incorporating Bayesian regression and continuous shrinkage priors, Li+PGS was developed in the International Consortium of Lithium Genetics cohort (ConLi+Gen: N=2,367) and replicated in the combined PsyCourse (N=89) and BipoLife (N=102) studies. The associations of Li+PGS and lithium treatment response - defined in a continuous ALDA scale and a categorical outcome (good response vs. poor response) were tested using regression models, each adjusted for the covariates: age, sex, and the first four genetic principal components. Statistical significance was determined at P<����������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������.

Mediators of quality of life change in people with severe psychotic disorders treated in integrated care: ACCESS II study

BACKGROUND

Patients with severe psychotic disorders exhibit a severely reduced quality of life (QoL) at all stages of the disease. Integrated care often led to an improvement in QoL. However, the specific mediators of QoL change are not yet well understood.

METHODS

The ACCESS II study is a prospective, long-term study investigating the effectiveness of an integrated care program for people with severe psychotic disorders (IC-TACT) that includes Therapeutic Assertive Community Treatment within a care network of in- and outpatient services at the University Medical Center Hamburg-Eppendorf, Germany. We examined longitudinal associations between QoL and the hypothesized mediators of change (i.e., negative symptoms, depression, and anxiety), using cross-lagged panel models.

RESULTS

The sample includes 418 severely ill patients treated in IC-TACT for at least 1 year. QoL increased, whereas symptom severity decreased significantly from baseline to 6-month follow-up (p-values ≤ 0.001), and remained stable until 12-month follow-up. QoL and symptom severity demonstrated significant auto-correlated effects and significant cross-lagged effects from QoL at baseline to negative symptoms (6 months, β = -0.20, p < 0.001) to QoL (12 months, β = -0.19, p < 0.01) resulting in a significant indirect, mediated effect. Additionally, negative symptoms after 6 months had a significant effect on the severity of depression after 12 months (β = 0.13, p < 0.05).

CONCLUSIONS

Negative symptoms appear to represent an important mechanism of change in IC-TACT indicating that improvement of QoL could potentially be achieved through optimized intervention on negative symptoms. Moreover, this may lead to a reduction in the severity of depression after 12 months.

Health-related quality of life in severe psychotic disorders during integrated care: 5-year course, prediction and treatment implications (ACCESS II)

Purpose

Studies on outcomes mapping Quality of Life (QoL) as patient-reported outcome over a longer period in severe psychotic disorders are scarce. However, such data would be particularly important for structuring, implementing and operating effective and efficient care models and for promoting satisfaction with care, service engagement and adherence.

Methods

The ACCESS II study is a prospective long-term study of an integrated care model for people with severe psychotic disorders. The model includes Therapeutic Assertive Community Treatment within a cross-sectoral and interdisciplinary network. This publication analyses the course of QoL assessed with the Q-LES-Q-18 using a mixed model for repeated measures.

Results

Mapping the course of QoL in N = 329 participants, there is a significant increase in the first 6 weeks of treatment (early course). Comparison to a published norm show significant lower QoL for severe psychotic disorders. The variable having a traumatic event before the age of 18 was significantly negatively associated with QoL. A decrease in the severity of depressive as well as in positive symptomatology in the first six weeks after admission was associated with increase of QoL.

Conclusion

Results indicate that the overall symptom burden at time of inclusion is not decisive for the perceived QoL in the long-term course while the reduction in the severity of depressive and positive symptoms is important. This means focusing even more on the treatment of depressive symptoms and include traumatherapeutic aspects in the long-term treatment of severe psychotic disorders if needed.

Trail registration

ClinicalTrials.gov (identifier: NCT01888627).

Individuals at increased risk for development of bipolar disorder display structural alterations similar to people with manifest disease

In psychiatry, there has been a growing focus on identifying at-risk populations. For schizophrenia, these efforts have led to the development of early recognition and intervention measures. Despite a similar disease burden, the populations at risk of bipolar disorder have not been sufficiently characterized. Within the BipoLife consortium, we used magnetic resonance imaging (MRI) data from a multicenter study to assess structural gray matter alterations in N = 263 help-seeking individuals from seven study sites. We defined the risk using the EPIbipolar assessment tool as no-risk, low-risk, and high-risk and used a region-of-interest approach (ROI) based on the results of two large-scale multicenter studies of bipolar disorder by the ENIGMA working group. We detected significant differences in the thickness of the left pars opercularis (Cohen's d = 0.47, p = 0.024) between groups. The cortex was significantly thinner in high-risk individuals compared to those in the no-risk group (p = 0.011). We detected no differences in the hippocampal volume. Exploratory analyses revealed no significant differences in other cortical or subcortical regions. The thinner cortex in help-seeking individuals at risk of bipolar disorder is in line with previous findings in patients with the established disorder and corresponds to the region of the highest effect size in the ENIGMA study of cortical alterations. Structural alterations in prefrontal cortex might be a trait marker of bipolar risk. This is the largest structural MRI study of help-seeking individuals at increased risk of bipolar disorder.

Course, remission and recovery in patients with severe psychotic disorders with or without comorbid substance use disorders: Long-term outcome in evidence-based integrated care (ACCESS II study)

OBJECTIVES

People with psychotic disorders have a high prevalence of comorbid mental disorders, especially if severe mental illness (SMI) criteria are fulfilled. Substance Use Disorders (SUD) are the most common comorbidity. The aim of the study is to investigate whether SMI patients with and without comorbid SUD have a comparable course, remission and recovery rates within evidence-based care.

METHODS

ACCESS is an integrated care model for patients with severe nonaffective and affective psychotic disorders. Treatment trajectories of patients, who have been in ACCESS care for at least 4 years, with and without SUD were compared with regard to the course of illness using Mixed Model Repeated Measures (MMRM) as well as recovery rates and its predictors.

RESULTS

187 of 312 patients (60%) were at least 4 years in ACCESS. Of these, 126 (67.4%) had a comorbid SUD at admission. Patients had on average 2.96 SUD, 87 (69%) had a dependence. Both groups improved significantly over 4 years in all outcome parameters. However, patients with substance dependence showed significantly worse outcomes in psychopathology (p < 0.001), functioning (p = 0.006) and quality of life (p = 0.026). Using LOCF, 44 patients (23.5%) fulfilled recovery criteria at endpoint. Comorbid substance use dependence was the only significant predictor for non-recovery (OR = 0.462, p = 0.048).

CONCLUSION

SUD and especially substance dependence are common in psychotic disorders with SMI. Evidence-based integrated care also leads to long-term improvement in these patients, but to a lesser extent than in patients without SUD. In particular, the "optimal" outcome recovery is made more difficult by SUD dependence.

Study protocol for a randomised controlled trial evaluating an evidence-based, stepped and coordinated care service model for mental disorders (RECOVER)

INTRODUCTION

Healthcare systems around the world are looking for solutions to the growing problem of mental disorders. RECOVER is the synonym for an evidence-based, stepped and cross-sectoral coordinated care service model for mental disorders. RECOVER implements a cross-sectoral network with managed care, comprehensive psychological, somatic and social diagnostics, crisis resolution and a general structure of four severity levels, each with assigned evidence-based therapy models (eg, assertive community treatment) and therapies (eg, psychotherapy). The study rationale is the investigation of the effectiveness and efficiency of stepped and integrated care in comparison to standard care.

METHODS AND ANALYSIS

The trial is conducted in accordance to the Standard Protocol Items: Recommendations for Interventional Trials Statement. The study aims to compare the RECOVER model with treatment as usual (TAU). The following questions are examined: Does RECOVER reduce healthcare costs compared with TAU? Does RECOVER improve patient-relevant outcomes? Is RECOVER cost-effective compared with TAU? A total sample of 890 patients with mental disorders will be assessed at baseline and individually randomised into RECOVER or TAU. Follow-up assessments are conducted after 6 and 12 months. As primary outcomes, cost reduction, improvement in symptoms, daily functioning and quality of life as well as cost-effectiveness ratios will be measured. In addition, several secondary outcomes will be assessed. Primary and secondary outcomes are evaluated according to the intention-to-treat principle. Mixed linear or logistic regression models are used with the direct maximum likelihood estimation procedure which results in unbiassed estimators under the missing-at-random assumption. Costs due to healthcare utilisation and productivity losses are evaluated using difference-in-difference regressions.

ETHICS AND DISSEMINATION

Ethical approval from the ethics committee of the Hamburg Medical Association has been obtained (PV5672). The results will be disseminated to service users and their families via the media, to healthcare professionals via professional training and meetings and to researchers via conferences and publications.

TRIAL REGISTRATION NUMBER AND REGISTRY NAME

ClinicalTrials.gov (NCT03459664), RECOVER PROTOCOL VERSION: 19 March 2020 (V.3.0).

Better care for less money: cost-effectiveness of integrated care in multi-episode patients with severe psychosis

OBJECTIVE

To compare cost-effectiveness of integrated care with therapeutic assertive community treatment (IC-TACT) versus standard care (SC) in multiple-episode psychosis.

METHOD

Twelve-month IC-TACT in patients with schizophrenia-spectrum and bipolar I disorders were compared with a historical control group. Primary outcomes were entropy-balanced cost-effectiveness based on mental healthcare costs from a payers' perspective and quality-adjusted life years (QALYs) as a measure of health effects during 12-month follow-up.

RESULTS

At baseline, patients in IC-TACT (n = 214) had significantly higher illness severity and lower functioning than SC (n = 56). Over 12 months, IC-TACT had significantly lower days in inpatient (10.3 ± 20.5 vs. 28.2 ± 44.9; P = 0.005) and day-clinic care (2.6 ± 16.7 vs. 16.4 ± 33.7; P = 0.004) and correspondingly lower costs (€-55 084). Within outpatient care, IC-TACT displayed a higher number of treatment contacts (116.3 ± 45.3 vs. 15.6 ± 6.3) and higher related costs (€+1417). Both resulted in lower total costs in IC-TACT (mean difference = €-13 248 ± 2975, P < 0.001). Adjusted incremental QALYs were significantly higher for IC-TACT versus SC (+0.10 ± 0.37, P = 0.05). The probability of cost-effectiveness of IC-TACT was constantly higher than 99%.

CONCLUSION

IC-TACT was cost-effective compared with SC. The use of prima facies 'costly' TACT teams is highly recommended to improve outcomes and save total cost for patients with severe psychotic disorders.

Efficiency of air filter sets for the prevention of airborne infections in laboratory animal houses

Air filter sets (classes EU6 and EU9, or EU6 and S) were tested for their efficiency in protecting laboratory animals against potential airborne infections. Flexible-film isolators were used as a smaller scale model. In the first experiment, lasting 7 months, it was tested whether minute virus of mice (MVM) was able to penetrate the air filters between one isolator containing experimentally infected mice and another with MVM negative mice. In the second experiment we tested whether microorganisms in the incoming air were able to penetrate air filter sets. To assess this gnotobiotic mice in an isolator were monitored for 9 months for changes of their microbial flora. In both experiments a combination of EU6 and EU9 air filters proved to be sufficient to maintain the microbiological status of the animals. The same combination of medium efficiency filters (EU6 and EU9) is used on the air supply to 4 SPF-barrier units in which infections with MVM occurred repeatedly soon after the initial stocking. After a thorough disinfection no reinfection has been detected to date. This demonstrates that the relatively low efficiency of the air filters was not the cause of the repeated infection. The procedure for disinfection is described.

Contamination of transplantable tumors, cell lines, and monoclonal antibodies with rodent viruses

Different biological materials were tested for murine viral contamination by using the mouse/rat antibody production test. Of 297 tumors examined, 75 (25.3%) were contaminated. Considerable differences in the contamination rate became evident when transplantable tumors from in vitro and from in vivo passages were compared. Of 186 tumors that had been propagated in animals, 36.6% were positive, whereas only 7 of 111 (6.3%) tumors propagated in vitro were contaminated. The highest rate of contamination was detected in mouse tumors. Testing of 135 specimens of mouse origin revealed 46.7% were contaminated, and 57 (70.4%) of 81 samples propagated in mice were positive for murine viruses. Moreover, 6.7% of 90 human tumors that had been passaged in athymic nude mice and 3.5% of 57 rat tumors were positive. Lymphocytic choriomeningitis virus was detected in 4 of 14 hamster tumors. The most frequent contaminant was lactic dehydrogenase elevating virus followed by reovirus 3, lymphocytic choriomeningitis virus, minute virus of mice, mouse hepatitis virus, rat coronaviruses, Kilham rat virus, and Mycoplasma pulmonis. Contamination with reovirus 3 and minute virus of mice was found in 4 (3.7%) of 109 cell lines tested, and 2 of 60 monoclonal antibody preparations or hybridoma cells contained lactic dehydrogenase virus. Contamination with two pathogens was detected in four mouse tumors and in one cell line.

Functions of estrogens and anti-estrogens in the rat endometrial adenocarcinoma cell lines RUCA-I and RUCA-II

Inbred rats of the DA/Han and BDII/Han strains have been proposed as suitable model systems for studying hormonal carcinogenesis, because they die mainly from hormone-dependent endometrial adenocarcinoma. Here we characterize the RUCA-I cell line derived from an endometrial adenocarcinoma of an inbred DA/Han rat and the RUCA-II cell line derived from an endometrial adenocarcinoma of an inbred BDII/Han rat. The RUCA-I cell line, if transplanted to the neck of female DA/Han rats, gives rise to endometrial adenocarcinomas at the ectopic site. The morphology of these ectopically grown tumors is predominantly of the moderately differentiated sub-class. In contrast, ectopic tumor growth of the RUCA-II cell line can be observed only if cells are transplanted to athymic nude mice. Biochemically, both cell lines are characterized by the stable expression of estrogen receptors. However, no statistically significant mitotic response of RUCA-I and RUCA-II cells to estradiol was measurable, and no induction of expression of the progesterone receptor by estradiol was detectable, although estradiol transformed the estrogen receptor into its stable DNA-binding state. In contrast, the rate of proliferation of RUCA-I but not of RUCA-II cells was reduced in the presence of 10(-6) M tamoxifen. From these results we conclude that (i) both cell lines, RUCA-I and RUCA-II, represent a new and promising endometrial tumor model; (ii) the mechanism of the hormone-dependent growth regulation of RUCA-I and RUCA-II cells is obviously impaired; (iii) the RUCA-I cell line appears to be a suitable model system for the study of molecular aspects of estrogen- and tamoxifen-dependent gene expression.

Rederivation of inbred strains of mice by means of embryo transfer

Embryo transfers were performed to rederive six inbred strains of mice, A/He, BALB/cByJ, BALB/c Lac, B10.BR/SgSnJ, C57BL/6J and DBA/2J. The aim was to determine whether it is possible to eliminate pathogens like mouse hepatitis virus (MHV) and Pasteurella pneumotropica (P.p.). The embryos were collected, handled and transferred into the oviduct of day one pseudopregnant SPF surrogate mothers under aseptic conditions. In 40.5% of the transfers, embryos developed to term. With respect to surrogate mothers delivering viable litters, 47.9% of the transferred embryos were born alive. Out of these 93.5% were reared. Virological and bacteriological examination of embryo donors verified the presence of P.p. and of antibodies against MHV in all strains. In some embryo donors P.p. could be isolated even from the uterine mucosa. However, neither in the surrogate mothers nor in the offspring could P.p. and antibodies against MHV be detected. Further bacteriological examination revealed that the offspring carried only the microbial flora received from the surrogate mother. The results indicate that embryo transfer is an appropriate tool to rederive mouse strains. In contrast to hysterectomy rederivation, embryo transfer has the advantage of avoiding postimplantational vertical transmissions of infections.

An enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to Pasteurella pneumotropica in murine colonies

An ELISA for the detection of class specific IgG antibodies to Pasteurella pneumotropica was developed for the serological diagnosis of infections in mouse colonies. Heat inactivated whole cell preparations of an isolate of P. pneumotropica biotype Heyl (strain P 166) served as antigen for the ELISA procedure and for immune serum production in germ-free Han:NMRI mice. Cross reactions with the autochthonous flora of Han:NMRI SPF-mice were not observed, but were evident when a P. pneumotropica antiserum was tested against other antigens of the Pasteurella-Actinobacillus group. According to the reclassification of this bacterial group proposed by Mutters et al. (1), strains of the following species were tested: P. anatis, P. canis, P. dagmatis, P. langaa, Pl multocida sub. multocida, P. pneumotropica biotype Jawetz, P. stomatis, Actinobacillus equuli and A. lignieresii. Clear cross reactions could be shown with P. pneumotropica biotype Jawetz and A. equuli and to a lesser extent with P. anatis. Antibody formation profiles after nasal infection of Han:NMRI mice exhibited a primary rise of IgG-type antibody titer between 17 to 21 days post infection. Investigations of different mouse colonies free and infected with P. pneumotropica revealed good correlations between serological and bacteriological findings.

Diagnosis of murine infections in relation to test methods employed

Comparative investigations of Sendai virus, pneumonia virus of mice (PVM), mouse encephalomyelitis virus (mouse polio), minute virus of mice (MVM), and reovirus type 3 (Reo 3) infected murine colonies revealed a 30% higher incidence of positive sera when enzyme-linked immunosorbent assay (ELISA) was employed instead of hemagglutination inhibition (HI) tests. Equivalent sensitivity as in the ELISA was obtained when the same sera were investigated by indirect immunofluorescence (IF) tests. The virus purification techniques described resulted in highly suitable antigens for all indirect ELISA established. Since IIF requires no purified antigens, this test is recommended as an alternative to ELISA as well as to HI and complement fixation (CF) tests for laboratories lacking the necessary equipment for high speed centrifugation. A high incidence of false positive HI reactions was found particularly in Reo 3 routine serology. An updated survey of seromonitoring showed that European murine colonies appeared to be infected far less with Reo 3 if ELISA or IIF tests were employed. During 1982-1984, only 13% of the mouse colonies screened possessed Reo 3 positive sera whereas no natural Reo 3 infection was found in rat colonies. Mouse hepatitis virus (MHV) and the coronaviruses of rats exhibited the highest incidence in murine colonies. A total of 60% of mouse and 41% of rat colonies were found to be infected by these viruses. In comparison with earlier serological surveys, the relative incidence of other murine infections was similar. Antibodies against Bacillus piliformis (Tyzzer's disease) were detected by the IIF test in 41% of the rat colonies screened.

Adenovirus pneumonia in guineapigs: an experimental reproduction of the disease

The recently described virus-induced pneumonia in guineapigs (Naumann et al., 1981) was experimentally reproducible in newborn animals, though not in preadult animals. Baby hamsters and newborn rats were also not susceptible to infection. 10 of 11 infected newborn guineapigs developed pathological changes identical with those found in spontaneous cases. The incubation period was from 5 to 10 days. The agent could not be cultivated in vitro, and therefore no applicable serological tests could be established. The morphology of the virus, its intranuclear location, the course of the disease and the histopathological and ultrastructural changes strongly suggest that the virus is an adenovirus specific for guineapigs. The virus did not cross-react with human or fowl adenoviruses. It was ether resistant and non-oncogenic in baby rats and hamsters. During a 5-year period we registered a total of 51 spontaneous death cases diagnosed as adenovirus pneumonia in our experimental guineapigs, 4 from own breeding colony.

Diagnosis of Mycoplasma pulmonis infection of rats by an indirect immunofluorescence test compared with 4 other diagnostic methods

Efficiency of indirect immunofluorescence microscopy (IFM) for detection of M. pulmonis antibody (IgG) in rats was compared with results of enzyme-linked immunosorbent assay (ELISA), complement fixation (CF), cultural isolation and histopathology. IFM was carried out on M. pulmonis infected BHK-21 cells grown on cover slips or multitest slides. After acetone fixation these antigen carriers could be stored at -20 degrees C for several months so that serological tests could be done at any time and completed within 2 h. The IFM was strain specific and the sensitivity of the test was comparable with that of the ELISA, whereas the CF-test proved to be very insensitive. For routine monitoring, only in cases of fresh infections should time consuming cultural procedures be preferred to serological tests. Chronic disease stages were readily detected by histological examination.

Cell cycle-dependent multiplication of avian adenoviruses in chicken embryo fibroblasts

Propagation of CELO virus employing confluent monolayers of chicken enbryo fibroblasts (CEF) yielded virus titers one to two logs lower than those from confluent chicken kidney (CK) cells. An enhancement of virus production in CEF as measured by plaque formation was obtainedby infectng cultures in the growing non confluent state. Measurements of 3H-thymidine incorporation revealed a positive correlation between the DNA synthesis of CEF cultures at the time of inoculation and the amount of progeny virus, whereas in the CK-CELO-system no such relation was observed. Requirement of replicative fibroblasts for CELO multiplication was also demonstrated by comparison of virus replication in synchronized stationary and serum stimulated CEF cells. In stationary CEF cells arrested in the G1 phase of the cell replication cycle by serum deprivation and infected withe CELO virs, no cytopathic effect could be observed, and only very low amounts of virus were produced. But 24 hours after release of these cells for growth by serum stimulation a logarithmic rate of virus multiplication and a complete CPE occurred. Infection of synchronized CEF cultures at different stages of the cell cycle revealed that CELO multiplication was correlated with the S phase of the infected cell. In synchronized CELO infected CEF cultures viral DNA synthesis started 12 to 14 hours after growth stimulation when cells were near the end of the S phase. In contrast, no viral DNA synthesis could be measured in growth arrested CELO infected CEF cells, when cellular DNA synthesis was low. Therefore not only production of infectious virus but also viral DNA synthesis is correlated with events during the S phase of the infected CEF cell.