Lipid Signatures and Inter-Cellular Heterogeneity of Naı̈ve and Lipopolysaccharide-Stimulated Human Microglia-like Cells

Microglia are non-neuronal cells, which reside in the central nervous system and are known to play an important role in health and disease. We investigated the lipidomic phenotypes of human naı̈ve and stimulated microglia-like cells by atmospheric-pressure scanning microprobe matrix-assisted laser desorption/ionization mass spectrometry imaging (AP-SMALDI MSI). With lateral resolutions between 5 and 1.5 μm pixel size, we were able to chart lipid compositions of individual cells, enabling differentiation of cell lines and stimulation conditions. This allowed us to reveal local lipid heterogeneities in naı̈ve and lipopolysaccharide (LPS)-stimulated cells. We were able to identify individual cells with elevated triglyceride (TG) levels and could show that the number of these TG-enriched cells increased with LPS stimulation as a hallmark for a proinflammatory phenotype. Additionally, the observed local abundance alterations of specific phosphatidylinositols (PIs) indicate a cell specific regulation of the PI metabolism.

Mn-induced Fermi-surface reconstruction in the SmFeAsO parent compound

The electronic ground state of iron-based materials is unusually sensitive to electronic correlations. Among others, its delicate balance is profoundly affected by the insertion of magnetic impurities in the FeAs layers. Here, we address the effects of Fe-to-Mn substitution in the non-superconducting Sm-1111 pnictide parent compound via a comparative study of SmFe[Formula: see text]Mn[Formula: see text]AsO samples with [Formula: see text] 0.05 and 0.10. Magnetization, Hall effect, and muon-spin spectroscopy data provide a coherent picture, indicating a weakening of the commensurate Fe spin-density-wave (SDW) order, as shown by the lowering of the SDW transition temperature [Formula: see text] with increasing Mn content, and the unexpected appearance of another magnetic order, occurring at [Formula: see text] and 20 K for [Formula: see text] and 0.10, respectively. We attribute the new magnetic transition at [Formula: see text], occurring well inside the SDW phase, to a reorganization of the Fermi surface due to Fe-to-Mn substitutions. These give rise to enhanced magnetic fluctuations along the incommensurate wavevector [Formula: see text], further increased by the RKKY interactions among Mn impurities.

Implementation of a High-Repetition-Rate Laser in an AP-SMALDI MSI System for Enhanced Measurement Performance

Matrix-assisted laser desorption/ionization mass spectrometry imaging is a promising tool in the life sciences for obtaining spatial and chemical information from complex biological samples. State-of-the-art setups combine high mass resolution and high mass accuracy with high lateral resolution, offering untargeted insights into biochemical processes on the single-cell length scale. Despite recent technological breakthroughs, the sensitivity and acquisition speed of many setups are often in competition with achievable pixel resolutions below 25 μm. New measurement modes were developed by implementing a high-repetition-rate laser into an AP-SMALDI10 ion source, coupled to an orbital trapping mass spectrometer. These new MSI modes allow for a modular use of the new setup. We demonstrate that the system allows single cell features to be visualized in mouse brain tissue sections at a pixel resolution of 5 μm and an imaging speed of 18 pixels/s. Furthermore, the analytical sensitivity was improved in another measurement mode by applying multiple pulses of a highly focused laser beam over larger square pixels ≥25 μm edge length, increasing ion signal intensities up to 20-fold on tissue and decreasing the limit of detection by 1 order of magnitude.

Atmospheric-Pressure MALDI Mass Spectrometry Imaging at 213 nm Laser Wavelength

First results for a new atmospheric-pressure matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging source operating at 213 nm laser wavelength are presented. The activation of analytes in the 213 nm MALDI process at atmospheric pressure was evaluated and compared to results for 337 nm MALDI and electrospray ionization using thermometer molecules. Different sample preparation techniques for nicotinic acid, the matrix with the highest ionization efficiency at 213 nm of all tested matrices, were evaluated and optimized to obtain small crystal sizes, homogenous matrix layer sample coverage, and high ion signal gains. Mass spectrometry imaging experiments of phospholipids in mouse tissue sections in positive- and negative-ion mode with different lateral resolutions and the corresponding pre-/post-mass spectrometry imaging workflows are presented. The use of custom-made objective lenses resulted in sample ablation spot diameters of on average 2.9 μm, allowing mass spectrometry imaging experiments to be performed with 3 μm pixel size without oversampling. The ion source was coupled to an orbital trapping mass spectrometer offering high mass resolution (>100.000), high mass accuracy (≤ ±2 ppm), and high sensitivity (single pixel on-tissue tandem MS from 6.6 μm² ablation area). The newly developed 213 nm atmospheric-pressure MALDI source combines the high mass resolution and high mass accuracy performance characteristics of orbital trapping mass spectrometers with high lateral resolution (pixel size ∼3 μm) mass spectrometry imaging.

Suggested new breakpoints of anti-MERS-CoV antibody ELISA titers: performance analysis of serologic tests

To provide optimal cut-off values of anti-Middle East respiratory syndrome coronavirus (MERS-CoV) serologic tests, we evaluated performance of ELISA IgG, ELISA IgA, IFA IgM, and IFA IgG using 138 serum samples of 49 MERS-CoV-infected patients and 219 serum samples of 219 rRT-PCR-negative MERS-CoV-exposed healthcare personnel and patients. The performance analysis was conducted for two different purposes: (1) prediction of neutralization activity in MERS-CoV-infected patients, and (2) epidemiologic surveillance of MERS-CoV infections among MERS-CoV-exposed individuals. To evaluate performance according to serum collection time, we used ‘days post onset of illness (dpoi)’ and ‘days post exposure (dpex)’ assessing neutralization activity and infection diagnosis, respectively. Performance of serologic tests improved with delayed sampling time, being maximized after a seroconversion period. In predicting neutralization activity, ELISA IgG tests showed optimal performance using sera collected after 21 dpoi at cut-off values of OD ratio 0.4 (sensitivity 100% and specificity 100%), and ELISA IgA showed optimal performance using sera collected after 14 dpoi at cut-off value of OD ratio 0.2 (sensitivity 85.2% and specificity 100%). In diagnosis of MERS-CoV infection, ELISA IgG exhibited optimal performance using sera collected after 28 dpex, at a cut-off value of OD ratio 0.2 (sensitivity 97.3% and specificity 92.9%). These new breakpoints are markedly lower than previously suggested values (ELISA IgG OD ratio 1.1, sensitivity 34.8% and specificity 100% in the present data set), and the performance data help serologic tests to be practically used in the field of MERS management.

A patient with severe respiratory failure caused by novel human coronavirus

We report a case of a 45-year-old patient who developed severe acute respiratory distress syndrome accompanied by renal failure. An infection with a novel human coronavirus was confirmed and found to be the reason for rapidly progressive respiratory failure of our patient.

Specific serology for emerging human coronaviruses by protein microarray

We present a serological assay for the specific detection of IgM and IgG antibodies against the emerging human coronavirus hCoV-EMC and the SARS-CoV based on protein microarray technology. The assay uses the S1 receptor-binding subunit of the spike protein of hCoV-EMC and SARS-CoV as antigens. The assay has been validated extensively using putative cross-reacting sera of patient cohorts exposed to the four common hCoVs and sera from convalescent patients infected with hCoV-EMC or SARS-CoV.

Contact investigation of a case of human novel coronavirus infection treated in a German hospital, October-November 2012

On 24 October 2012, a patient with acute respiratory distress syndrome of unknown origin and symptom onset on 5 October was transferred from Qatar to a specialist lung clinic in Germany. Late diagnosis on 20 November of an infection with the novel Coronavirus (NCoV) resulted in potential exposure of a considerable number of healthcare workers. Using a questionnaire we asked 123 identified contacts (120 hospital and three out-of-hospital contacts) about exposure to the patient. Eighty-five contacts provided blood for a serological test using a two-stage approach with an initial immunofluorescence assay as screening test, followed by recombinant immunofluorescence assays and a NCoV-specific serum neutralisation test. Of 123 identified contacts nine had performed aerosol-generating procedures within the third or fourth week of illness, using personal protective equipment rarely or never, and two of these developed acute respiratory illness. Serology was negative for all nine. Further 76 hospital contacts also tested negative, including two sera initially reactive in the screening test. The contact investigation ruled out transmission to contacts after illness day 20. Our two-stage approach for serological testing may be used as a template for similar situations.

Contact investigation of a case of human novel coronavirus infection treated in a German hospital, October-November 2012

On 24 October 2012, a patient with acute respiratory distress syndrome of unknown origin and symptom onset on 5 October was transferred from Qatar to a specialist lung clinic in Germany. Late diagnosis on 20 November of an infection with the novel Coronavirus (NCoV) resulted in potential exposure of a considerable number of healthcare workers. Using a questionnaire we asked 123 identified contacts (120 hospital and three out-of-hospital contacts) about exposure to the patient. Eighty-five contacts provided blood for a serological test using a two-stage approach with an initial immunofluorescence assay as screening test, followed by recombinant immunofluorescence assays and a NCoV-specific serum neutralisation test. Of 123 identified contacts nine had performed aerosol-generating procedures within the third or fourth week of illness, using personal protective equipment rarely or never, and two of these developed acute respiratory illness. Serology was negative for all nine. Further 76 hospital contacts also tested negative, including two sera initially reactive in the screening test. The contact investigation ruled out transmission to contacts after illness day 20. Our two-stage approach for serological testing may be used as a template for similar situations.

Assays for laboratory confirmation of novel human coronavirus (hCoV-EMC) infections

We present a rigorously validated and highly sensitive confirmatory real-time RT-PCR assay (1A assay) that can be used in combination with the previously reported upE assay. Two additional RT-PCR assays for sequencing are described, targeting the RdRp gene (RdRpSeq assay) and N gene (NSeq assay), where an insertion/deletion polymorphism might exist among different hCoV-EMC strains. Finally, a simplified and biologically safe protocol for detection of antibody response by immunofluorescence microscopy was developed using convalescent patient serum.

Detection of a novel human coronavirus by real-time reverse-transcription polymerase chain reaction

We present two real-time reverse-transcription polymerase chain reaction assays for a novel human coronavirus (CoV), targeting regions upstream of the E gene (upE) or within open reading frame (ORF)1b, respectively. Sensitivity for upE is 3.4 copies per reaction (95% confidence interval (CI): 2.5–6.9 copies) or 291 copies/mL of sample. No cross-reactivity was observed with coronaviruses OC43, NL63, 229E, SARS-CoV, nor with 92 clinical specimens containing common human respiratory viruses. We recommend using upE for screening and ORF1b for confirmation.

[How to Read a Chest-X-ray?]

Only a standartized, systematic approach allows a complete review of a chest x-ray and the collection of all relevant informations. In detail, alterations of the following structures should be sought: soft tissue, bones, pleura, mediastinum, lung, heart, pulmonary circulation and hili. Technical factors and the position of the patient should also be considered.

Increased nuchal translucency thickness and normal karyotype: time for parental reassurance

OBJECTIVES

To study the outcome of pregnancy in chromosomally normal fetuses with increased nuchal translucency thickness (NT), with respect to fetal loss, structural defects and genetic syndromes with developmental delay, and to provide information that would be helpful for parental counseling on the residual risk of adverse outcome when ultrasound findings are normal.

METHODS

We reviewed the outcome of all pregnancies presenting at the Academic Medical Centre in Amsterdam with increased NT between January 1994 and March 2005. Fetal karyotyping and two-step ultrasound investigation at 13-18 and 20-24 weeks' gestation were offered in all cases. Particular attention was paid to the relationship between normal karyotype, ultrasound findings at the 20-24-week scan and subsequent pregnancy outcome. An adverse outcome was defined as miscarriage, intrauterine death, termination of pregnancy at parental request or the finding of one or more structural defects or genetic disorders.

RESULTS

A total of 675 fetuses with increased NT, known karyotype and known pregnancy outcome was analyzed. A chromosomal anomaly was detected in 224 (33%) fetuses. In 451 (67%) fetuses, the karyotype was normal. The overall incidence of an adverse pregnancy outcome in this group was 19% and, when analyzed according to the initial degree of increase in NT, the likelihood of an adverse outcome increased with increasing NT, ranging from 8% to 80%. 425 fetuses underwent a detailed second-trimester ultrasound scan. Anomalies were detected, at the time of ultrasound or after birth, in 54 (13%) of these fetuses (17 isolated cardiac defects, 14 other structural defects and 23 genetic disorders). An adverse pregnancy outcome was recorded in 4% of cases in which there were normal findings at the 20-week scan. Seven of these cases were classified as 'potentially amenable' to ultrasound detection. With exclusion of these cases, the chance of a healthy baby, if the 20-week scan was completely normal, was 98%. Genetic syndromes with dysmorphic features and neurodevelopmental delay occurred in seven (1.6%) of the fetuses with normal karyotype. In three of these pregnancies, non-specific suspicious ultrasound findings (nuchal edema, mild pyelectasis, pericardial effusion) were observed at the mid-trimester scan and in two others, subtle cardiac defects were detected after delivery. In the remaining two cases (0.5%) the mid-trimester scan was completely normal and no structural defects were observed after delivery.

CONCLUSION

After exclusion of chromosomal anomalies, one out of five fetuses with increased NT has an adverse pregnancy outcome. The chance of an uneventful pregnancy outcome depends on the initial degree of increase in NT. However, if the detailed ultrasound examination at around 20 weeks is normal, a favorable outcome can be expected with confidence, irrespective of initially increased NT.

Nuchal translucency measurement and congenital heart defects: modest association in low-risk pregnancies

OBJECTIVE

To assess the performance of nuchal translucency (NT) measurement in the first trimester of pregnancy as a marker for congenital heart defects (CHD) in the fetus in a low-risk obstetric population.

METHODS

Nuchal translucency screening was offered over a 3-year period to consecutive pregnant women without known a priori risk factors and attending midwife practices in three different areas in the Netherlands. In chromosomally normal fetuses and infants from the study population the NT measurements were matched with CHD detected either prenatally or postnatally.

RESULTS

NT screening was offered to 6132 women with an uptake of 83%. A total of 4876 NT measurements was performed. Pregnancy outcome data were available in 4181 cases (86%). Defects of the heart and great arteries (CHD) were diagnosed in 24 cases (prevalence 5.8/1000). Thirteen of these were classified as major (prevalence 3.1/1000). Two major CHD occurred in fetuses showing an increased NT at the first-trimester scan. The sensitivity of NT measurement > 95th and > 99th percentile for all CHD and for major CHD, was 8% and 15%, respectively. The positive likelihood ratios of NT > 95(th) and > 99th percentile for major CHD were 6, 5 and 33, respectively.

CONCLUSION

In pregnancies without known risk factors also, an increased NT is associated with major cardiac defects in the fetus and therefore represents an indication for specialized fetal echocardiography. However, this association is too weak to envisage a role for NT measurement as single screening strategy for the prenatal detection of cardiac defects.

Nuchal translucency screening and anxiety levels in pregnancy and puerperium

OBJECTIVES

To compare levels of anxiety and depression during pregnancy and puerperium between women who are offered nuchal translucency (NT) screening routinely and those who are not, and to compare levels between women accepting and those declining screening.

METHODS

In 12 midwife practices in three different health districts an experimental NT screening program was offered to pregnant women between 1 June 1999 and 1 January 2001. As part of this implementation study, questionnaires including the Hospital Anxiety and Depression Scale (HADS) were completed: after the patient was informed but before screening (T1), at 20 weeks of gestation (T2), and 6 weeks after delivery (T3). A control group of women receiving routine prenatal care (i.e. no screening offered) also completed the HADS questionnaire at 12 and 20 weeks and after delivery.

RESULTS

Five hundred and twenty-seven questionnaires were analyzed. There was a screening uptake of 87% in the intervention group (i.e. those offered screening). Women in this group differed significantly in the percentage of previous miscarriages and religious background compared with the control group. We adjusted for these differences in the analysis. There were no significant differences in HADS scores between the intervention and the control groups at T1, suggesting that women receiving information on screening were not more anxious compared with women who were not informed. Women who were offered screening (acceptors as well as decliners) had significantly lower HADS levels at 20 weeks and after delivery. There were no demographic differences between women accepting and those declining screening.

CONCLUSION

Informing women and offering them NT screening for Down syndrome does not increase anxiety or depression levels in pregnancy. In fact, women undergoing or declining screening seem less anxious compared with those who are not offered screening. It is possible that informing women and offering them the chance to decide autonomously whether to participate in screening reduces anxiety levels.

Susceptibility of different eukaryotic cell lines to SARS-coronavirus

In order to define and characterize target cells of SARS-coronavirus (SARS-CoV) we studied the susceptibility of 23 different permanent and primary eukaryotic cell lines to SARS-coronavirus. Beneath Vero E6 cells SARS- Coronavirus infection could also be demonstrated in two pig cell lines (POEK, PS) and one human cell line (Huh-7) using the indirect immunofluorescence assay and a newly established quantitative real-time PCR. In all susceptible cell lines mRNA of the Angiotensin-converting enzyme 2 (ACE2), the functional receptor for SARS-CoV infection, could be detected by RT-PCR. Our results show that there is a correlation between the abundance of ACE2 mRNA and SARS-CoV susceptibility.

Disappearance of enlarged nuchal translucency before 14 weeks' gestation: relationship with chromosomal abnormalities and pregnancy outcome

OBJECTIVE

The aim of this study was to investigate the natural course of enlarged nuchal translucency (NT) and to determine if its disappearance before 14 weeks' gestation is a favorable prognostic sign in relation to fetal karyotype and pregnancy outcome.

METHODS

A total of 147 women with increased NT (> 95th centile) at first measurement were included in this study. A second measurement was performed in all cases, at an interval of at least 2 days. Both measurements were taken between 10 + 3 and 14 + 0 weeks. All women underwent chorionic villus sampling or amniocentesis for subsequent karyotyping. In those women with a normal karyotype, a fetal anomaly scan was performed at 20 weeks' gestation. Pregnancy outcome was recorded in all cases. The finding of persistent or disappearing NT enlargement was analyzed in relation to fetal karyotype and pregnancy outcome.

RESULTS

Of the 147 paired measurements, NT remained enlarged at the second measurement in 121 (82%) cases. An abnormal karyotype was found in 35% of these cases. In 26 (18%) fetuses the NT measurement was found to be below the 95th percentile at the second measurement and in only two of them an abnormal karyotype was found (8%). In the 103 chromosomally normal fetuses an adverse outcome (i.e. fetal loss or structural defects) was recorded in 22 fetuses with persistent enlargement (28%) and in four fetuses with disappearing enlargement (17%).

CONCLUSIONS

Disappearance of an enlarged NT before 14 weeks' gestation is not a rare phenomenon and seems to be a favorable prognostic sign with respect to fetal karyotype. Overall, no significant difference in pregnancy outcome was found between chromosomally normal fetuses with persisting or disappearing NT enlargement.

[Ultrasound screening for Down's syndrome early in pregnancy: nuchal translucency thickness]

Screening for Down's syndrome (DS) in the Netherlands is based on maternal age. Women aged 36 years or above are offered amniocentesis or chorionic villus sampling to determine if the foetus has Down's syndrome or other chromosomal abnormalities. Disadvantages of this method are a low detection rate of affected pregnancies (no more than 15%) and iatrogenic miscarriages (0.5-1%). Pregnant women under the age of 36 are not eligible for screening, even though 70% of the children with Down's syndrome are born in this age group. Screening by measuring nuchal translucency thickness, an early ultrasound marker for Down's syndrome carried out in the first trimester of pregnancy, has a higher detection rate with a less invasive method and therefore fewer iatrogenic miscarriages. However, Dutch law prohibits the offer of screening to women with a low individual risk of DS (Population Screening Act), because of the anxiety this may provoke in these women. The Dutch Health Council's Prenatal Screening Committee has advised the minister of Public Health, Welfare and Sport that risk-assessment screening, in particular the triple test, should no longer be postponed and that research into (other) screening options should be stimulated.

Ductus venosus studies in fetuses at high risk for chromosomal or heart abnormalities: relationship with nuchal translucency measurement and fetal outcome

OBJECTIVE

To investigate, in a high-risk group of fetuses, the role of ductus venosus Doppler velocimetry as a prognostic factor, in addition to nuchal translucency measurement, for predicting chromosomal anomalies and, where the karyotype was normal, for predicting fetal outcome.

METHODS

Nuchal translucency was measured and ductus venosus pulsatility index and late diastolic flow (a-wave) were recorded in 186 fetuses at a median gestational age of 12.6 weeks (range, 10-17). Fetal karyotype, the presence of structural anomalies, pregnancy outcome, neonatal examination at birth and postnatal follow up were the outcome values.

RESULTS

Nuchal translucency measurement was increased in 112 fetuses. The outcome of pregnancy was normal in 130 fetuses. Fifty-six fetuses had an adverse outcome (46 chromosomal anomalies, three intrauterine deaths, six structural anomalies and one developmental disorder). The sensitivity of an abnormal ductus venosus pulsatility index or of absent or reversed flow during the a-wave was 65% for chromosomal anomalies and 68% for an adverse outcome. The specificity was 79%. There was a significant correlation between nuchal translucency and ductus venosus pulsatility index. In chromosomally normal fetuses with an enlarged nuchal translucency an abnormal ductus venosus flow was associated with a nearly nine-fold increase in adverse outcome (odds ratio 11.7).

CONCLUSION

Ductus venosus Doppler velocimetry can be used in addition to nuchal translucency measurement as a predictor of chromosomal anomalies. However, as the ductus venosus blood flow pattern is correlated with nuchal translucency measurement it cannot be used as an independent variable to reduce the indication for fetal karyotyping. Ductus venosus Doppler velocimetry may have a role in the counseling of parents in the case of an enlarged nuchal translucency and normal karyotype by identifying those fetuses in need of an intensive follow up due to an increased risk of adverse outcome.

Outcome of fetuses with increased nuchal translucency

Recent reports on nuchal translucency screening in unselected patient populations show results that are comparable with those reported by the thus far largest series on screening for Down's syndrome based on maternal age and nuchal translucency measurement. Much interest is focused on the prognostic value of increased nuchal translucency in fetuses with normal chromosomes. Increased nuchal translucency is regarded as a clear sign of declining fetal health, which can be associated with fetal demise, structural anomalies, rare genetic syndromes, and in particular congenital heart defects. A clear association is demonstrated between nuchal translucency above the 99th centile and congenital cardiac defects. Such a finding should prompt specialized echocardiography. However, on the whole the sensitivity of nuchal translucency screening is too low to consider this as the sole criterion to screen for critical heart defects.

The influence of fetal position on nuchal translucency thickness

OBJECTIVE

To determine whether nuchal translucency thickness is influenced by the fetal position at ultrasound examination.

SUBJECTS

Transabdominal ultrasound examination for pregnancy dating and measurement of nuchal translucency thickness was performed at 10-14 weeks' gestation in all women attending the antenatal clinic of our hospital. During the examination special attention was paid to a change in fetal position from prone to supine or vice versa.

METHODS

For each fetus the nuchal translucency measurement was repeated when a positional change from prone to supine or vice versa was recorded. All measurements were recorded on hard copy. An image-scoring method was used and evaluated by three independent reviewers.

RESULTS

Eighty-five fetuses were included in this study. The mean nuchal translucency for supine fetuses was 1.91 mm compared with 1.93 mm for prone fetuses. The mean quality-score was 6.54 for supine fetuses and 6.55 for prone fetuses. This difference was not statistically significant.

CONCLUSION

Fetal position has no influence on the measurement of nuchal translucency.

[Outcome after hospital rehabilitation of patients with myocardial infarct]

A series of follow-ups were carried out in 947 patients who had 12 to 28 months previously (average 16.6 months) undergone a period of rehabilitation at this clinic in Gais . 17 patients were not traced, but from the remaining 930 patients, 35 (3.8%) had died of cardiac disorders, 21 had had nonfatal infarctions, and 51 patients had undergone aortocoronary bypass operation by the follow-up period. The prevalence and grade of angina pectoris (NYHA functional classification) in 816 patients from whom data was obtained remained unchanged. Even after exclusion of all patients with reinfarction or bypass surgery, there was no increase in the severity of angina pectoris in the remaining 752 patients. 705 patients had returned to work, 555 of whom were still in full employment and 118 part-time , while 32 remained active housewives. From the remaining 112 patients who were not working, 55 had retired. In conclusion, a stable course and high grade of employment were observed during the first year after infarction in patients who had undergone a course of rehabilitation at this clinic.

Analysis of age-dependent resistance to murine coronavirus JHM infection in mice

Resistance to intraperitoneal murine coronavirus JHM infection in mice develops with age. C3H mice were found to be fully susceptible up to the age of 20 days and resistant after 23 days of age. Protection of susceptible animals from death due to infection could be achieved by maternal antibodies or by transfer of spleen cells from immunized, but not from nonimmunized, donor mice. Lack of protection by transfer of unprimed adult spleen cells was not related to immunosuppression by the host. Moreover, resistance of adult mice could not be abrogated by application of lymphocytes from suckling mice, although immune suppression by other means did affect the resistance of adult animals. On the other hand, spleen cells from nonimmunized mice could be primed with inactivated JHM virus in suckling mice and protected these mice from death due to a subsequent virus infection. Thus, the outcome of infection with JHM virus in suckling and adult mice can be influenced by immunological events, but is not exclusively due to the different stages of immune competence.

Influence of the immune system on the course of infection with murine coronavirus JHM in suckling mice

The course of infection with murine corona virus JHM in C3H mice depends on the age of the animals. Mice up to 20 days of age are fully susceptible while mice older than 23 days resist the infection. Protection of suckling mice from death of infection can be provided by intraperitoneal administration of immune spleen cells but not by non-immune spleen cells from adult mice. The immune spleen cells can be generated by priming adult mice, or by priming non-immune spleen cells from adult mice in baby mice with inactivated JHM virus. Thus the immune system might well be involved in the different outcome of infection with JHM-virus in suckling and adult mice, but it does not seem to be the exclusive factor responsible for the achievement of natural resistance.