Cerebroplacental ratio in predicting adverse perinatal outcome: a meta-analysis of individual participant data.

OBJECTIVE: To investigate if cerebroplacental ratio (CPR) adds to the predictive value of umbilical artery pulsatility index (UA PI) alone - standard of practice - for adverse perinatal outcome in singleton pregnancies. DESIGN AND SETTING: Meta-analysis based on individual participant data (IPD). POPULATION OR SAMPLE: Ten centres provided 17 data sets for 21 661 participants, 18 731 of which could be included. Sample sizes per data set ranged from 207 to 9215 individuals. Patient populations varied from uncomplicated to complicated pregnancies. METHODS: In a collaborative, pooled analysis, we compared the prognostic value of combining CPR with UA PI, versus UA PI only and CPR only, with a one-stage IPD approach. After multiple imputation of missing values, we used multilevel multivariable logistic regression to develop prediction models. We evaluated the classification performance of all models with receiver operating characteristics analysis. We performed subgroup analyses according to gestational age, birthweight centile and estimated fetal weight centile. MAIN OUTCOME MEASURES: Composite adverse perinatal outcome, defined as perinatal death, caesarean section for fetal distress or neonatal unit admission. RESULTS: Adverse outcomes occurred in 3423 (18%) participants. The model with UA PI alone resulted in an area under the curve (AUC) of 0.775 (95% CI 0.709-0.828) and with CPR alone in an AUC of 0.778 (95% CI 0.715-0.831). Addition of CPR to the UA PI model resulted in an increase in the AUC of 0.003 points (0.778, 95% CI 0.714-0.831). These results were consistent across all subgroups. CONCLUSIONS: Cerebroplacental ratio added no predictive value for adverse perinatal outcome beyond UA PI, when assessing singleton pregnancies, irrespective of gestational age or fetal size. TWEETABLE ABSTRACT: Doppler measurement of cerebroplacental ratio in clinical practice has limited added predictive value to umbilical artery alone.

The prognostic accuracy of short term variation of fetal heart rate in early-onset fetal growth restriction: A systematic review.

OBJECTIVE: Cardiotocography (CTG) is an important tool for fetal surveillance in severe early-onset fetal growth restriction (FGR). Assessment of the CTG is usually performed visually (vCTG). However, it is suggested that computerized analysis of the CTG (cCTG) including short term variability (STV) could more accurately detect fetal compromise. The objective of this study was to systematically review the literature on the association between cCTG and perinatal outcome and the comparison of cCTG with vCTG. STUDY DESIGN: A systematic search was performed in MEDLINE, EMBASE and Google Scholar. Studies were included that assessed prognostic accuracy of STV or compared STV to vCTG in patients with FGR. Risk of bias and concerns about applicability were assessed with the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies-2) instrument. RESULTS: Of the 885 records identified in the search, five cohort studies (387 patients) were included. We found no randomized studies comparing STV with visual CTG in patients with FGR. The risk of bias of all studies was generally judged as 'low'. One small study found an association of low STV with neonatal acidosis. One study observed no association of STV with long-term outcome. Composite analysis of all five studies showed a non-significant relative risk for acidosis after a low STV of 1.4 (95% CI 0.6-3.2, N = 387). Further meta-analysis was hampered due to heterogeneity in outcome reporting and use of different thresholds. CONCLUSION: The evidence from the included studies did not support an association of STV and short or long term outcome. However, available data are limited and heterogeneous, and influenced by management based on STV. Solid evidence from a randomized controlled trial comparing STV with vCTG including long term infant outcome is needed before STV can be used clinically for timing of delivery in patients with FGR.

Prognostic accuracy of cerebroplacental ratio and middle cerebral artery Doppler for adverse perinatal outcome: systematic review and meta-analysis.

OBJECTIVE: Doppler ultrasonographic assessment of the cerebroplacental ratio (CPR) and middle cerebral artery (MCA) is widely used as an adjunct to umbilical artery (UA) Doppler to identify fetuses at risk of adverse perinatal outcome. However, reported estimates of its accuracy vary considerably. The aim of this study was to review systematically the prognostic accuracies of CPR and MCA Doppler in predicting adverse perinatal outcome, and to compare these with UA Doppler, in order to identify whether CPR and MCA Doppler evaluation are of added value to UA Doppler. METHODS: PubMed, EMBASE, the Cochrane Library and ClinicalTrials.gov were searched, from inception to June 2016, for studies on the prognostic accuracy of UA Doppler compared with CPR and/or MCA Doppler in the prediction of adverse perinatal outcome in women with a singleton pregnancy of any risk profile. Risk of bias and concerns about applicability were assessed using the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies-2) tool. Meta-analysis was performed for multiple adverse perinatal outcomes. Using hierarchal summary receiver-operating characteristics meta-regression models, the prognostic accuracy of CPR vs MCA Doppler was compared indirectly, and CPR and MCA Doppler vs UA Doppler compared directly. RESULTS: The search identified 4693 articles, of which 128 studies (involving 47 748 women) were included. Risk of bias or suboptimal reporting was detected in 120/128 studies (94%) and substantial heterogeneity was found, which limited subgroup analyses for fetal growth and gestational age. A large variation was observed in reported sensitivities and specificities, and in thresholds used. CPR outperformed UA Doppler in the prediction of composite adverse outcome (as defined in the included studies) (P < 0.001) and emergency delivery for fetal distress (P = 0.003), but was comparable to UA Doppler for the other outcomes. MCA Doppler performed significantly worse than did UA Doppler in the prediction of low Apgar score (P = 0.017) and emergency delivery for fetal distress (P = 0.034). CPR outperformed MCA Doppler in the prediction of composite adverse outcome (P < 0.001) and emergency delivery for fetal distress (P = 0.013). CONCLUSION: Calculating the CPR with MCA Doppler can add value to UA Doppler assessment in the prediction of adverse perinatal outcome in women with a singleton pregnancy. However, it is unclear to which subgroup of pregnant women this applies. The effectiveness of the CPR in guiding clinical management needs to be evaluated in clinical trials. © 2017 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

The relationship between physical and psychological complaints and quality of life in severely injured patients.

PURPOSE: The purpose of this study was two-fold. The first goal was to investigate which variables were associated with the remaining physical limitations of severely injured patients after the initial rehabilitation phase. Second, we investigated whether physical limitations were attributable to the association between psychological complaints and quality of life in this patient group. METHODS: Patients who were 18 years or older and who had an injury severity score (ISS)>15 completed a set of questionnaires at one time-point after their rehabilitation phase (15-53 months after their trauma). The Short Musculoskeletal Function Assessment (SMFA) questionnaire was used to determine physical limitations. The Hospital Anxiety and Depression Scale, the Dutch Impact of Event Scale and the Cognitive Failure Questionnaire were used to determine psychological complaints, and the World Health Organization Quality of Life assessment instrument-BREF was used to measure general Quality of Life (QOL). Differences in physical limitations were investigated for several trauma- and patient-related variables using non-parametric independent-sample Mann-Whitney U tests. Multiple linear regression was performed to investigate whether the decreased QOL of severely injured patients with psychological complaints could be explained by their physical limitations. RESULTS: Older patients, patients with physical complaints before the injury, patients with higher ISS scores, and patients who had an injury of the spine or of the lower extremities reported significantly more physical problems. Additionally, patients with a low education level, patients who were living alone, and those who were unemployed reported significantly more long-term physical problems. Severely injured patients without psychological complaints reported significantly less physical limitations than those with psychological complaints. The SMFA factor of Lower extremity dysfunction was a confounder of the association between psychological complaints and QOL in all QOL domains. CONCLUSIONS: Long-term physical limitations were mainly reported by patients with psychological complaints. The decreased QOL of severely injured patients with psychological complaints can partially be explained by physical limitations, particularly those involving lower extremity function. Experienced physical limitations were significantly different for some trauma and patient characteristics. These characteristics may be used to select patients for whom a rehabilitation programme would be useful.

Evaluation of real-life dosing of oral medicines with respect to fluid and food intake in a Dutch-speaking population.

WHAT IS KNOWN AND OBJECTIVE: Oral drug administration is the most preferred route of drug administration. For some specific classes of drugs, recommendations regarding the intake of the drug product are provided by and approved in the summary of product characteristics (SmPC) after testing the oral drug product in clinical trials under strict and predefined conditions. The aim of this study was to investigate how certain classes of medicines are taken in a "real-life" setting in terms of concomitant fluid and food intake by a Dutch-speaking population in Flanders (Belgium). The outcome of this study was comprehensively discussed with literature data to evaluate the positive or negative consequences of their drug intake in daily life. METHODS: A retrospective and non-interventional study was set up by means of questionnaires completed by two different groups: children (ie 0-15 years) and (young) adults (ie 16 years and older). RESULTS AND DISCUSSION: In children, the co-administered volume increases with age because of a gradual switch from liquids to solid dosage forms. In adults, water was the most selected co-administered fluid and the preferred volume of intake was a half glass of liquid. WHAT IS NEW AND CONCLUSION: Results of the surveys clearly indicated that the majority of all participants took their medication with a sip or half glass of water. However, this was not the case for the youngest children, as their preferred formulations were liquids (eg solutions, suspensions) which do not require any extra intake of liquid. In the case of specific classes of drugs, real-life intake can still be improved, suggesting that the pharmacist's advice has an important influence on their administration of medicines.

Psychometric properties of the Dutch Short Musculoskeletal Function Assessment (SMFA) questionnaire in severely injured patients.

UNLABELLED: In this cross-sectional study the psychometric properties are examined of the adapted Dutch translation of the Short Musculoskeletal Function Assessment (SMFA) questionnaire in severely injured patients (ISS>15). PATIENTS AND METHODS: Patients (N=173) completed the SMFA, the World Health Organization Quality of Life assessment instrument-BREF (WHOQOL-BREF), the Dutch Impact of Event Scale (IES), the Hospital Anxiety and Depression Scale (HADS) and the Cognitive Failure Questionnaire (CFQ). The Abbreviated Injury Score and the Injury Severity Score were established to determine the injured body area and the severity of the injuries. Exploratory factor analysis (method: PAF) was performed. Correlations were calculated between our SMFA factors and scores on the WHOQOL-BREF, IES, HADS and CFQ. The SMFA scores of the factors Upper extremity dysfunction and Lower extremity dysfunction were compared between subgroups of patients with and without injuries in respectively the upper extremities and the lower extremities. For responsiveness analysis, data were compared with the baseline SMFA measurement of a reference group. RESULTS: A three-factor structure was found: Lower extremity dysfunction, Upper extremity dysfunction, and Emotion. Strong correlations between the SMFA and the other questionnaires were found. Patients with injury of the lower extremities had significantly higher scores on the factor Lower extremity dysfunction than patients without injury of the lower extremities (p=0.017). In none of the factors, a significant difference in mean scores was found between patients with and without injury of the upper extremities. Severely injured patients had significantly higher SMFA scores than the reference group (p<0.001). CONCLUSION: The adapted Dutch translation of the SMFA showed good psychometric properties in severely injured patients. It appeared to be useful to get a general overview of patients' Health Status as well as patients' Health Related Quality Of Life.

Improving performance and agreement in injury coding using the Abbreviated Injury Scale: a training course helps.

The aim of this study was to determine the influence of a dedicated training course on the ability of participants to assign correct codes and their inter-observer agreement using the Abbreviated Injury Scale (AIS98). Twelve participants followed a one-day training course in injury coding. Codes were recorded before, during and after the course. The number of correctly assigned codes and severity codes, as well as the Fleiss' kappas improved significantly during and after the course. This study emphasises the benefit of training in injury coding. Training improves the ability to assign correct codes and it reduces inter-observer variability. We advise all who are involved in injury coding to follow a dedicated training course.

Quality of life in severely injured patients depends on psychosocial factors rather than on severity or type of injury.

BACKGROUND: Former studies have demonstrated that health-related quality of life is decreased in severely injured patients. However, in those studies patients were asked about their functioning and not about their (dis)contentment concerning their functioning. Little is known about how severely injured patients experience their quality of life (QOL). The objective of this cross-sectional study was to measure this subjective QOL of severely injured patients after their rehabilitation phase and to examine which accident- and patient-related factors affect the QOL of these patients. METHODS: Patients of 18 years or older with an injury severity score (ISS) above 15 were included 15-53 months after their accident. Comorbidity before the accident, accident and sociodemographic characteristics, and QOL were obtained from the trauma registry and questionnaires. The WHOQOL-BREF was used to measure QOL. A reference group of the Dutch general population was used for comparison. RESULTS: The participation rate was 61% (n=173). Compared with the reference data, severely injured patients experienced a significantly worse QOL in all domains except social relations. The QOL scores were significantly decreased in all domains for patients with intracranial injury in combination with other injuries. Patients with a severe intracranial injury (AIS>3) only reported significantly impaired QOL in the general and physical domains. Patients who resumed working or lived with others had significantly higher scores in all domains of QOL than patients who did not work anymore or were living alone. Significantly lower QOL scores were obtained from patients with comorbidity before the accident and from patients with longer durations of intensive care unit (ICU) treatment or hospitalisation. Gender, accident characteristics and time since the accident did not appear to be important for experienced QOL. CONCLUSIONS: The experience of impaired QOL appears to depend on living alone, inability to return to work and pre-accidental comorbidity rather than on the injured body area or the severity of the injury. Duration of hospital or ICU stay is important to subsequent QOL, even if ISS or body region is not.

A cross-sectional study of psychological complaints and quality of life in severely injured patients.

PURPOSE: The purpose of this study was to examine the incidence of psychological complaints and the relationship of these complaints with the quality of life (QOL) and accident- and patient-related factors among severely injured patients after the rehabilitation phase. METHODS: Patients of 18 years or older with an injury severity score above 15 were included 15-53 months after their accident. Accident and patient characteristics were obtained from questionnaires and the trauma registry. Several questionnaires (Hospital Anxiety and Depression Scale, Impact of Events Scale, and Cognitive Failure Questionnaire) were used to determine the symptoms of psychological problems (anxiety or depression, post-traumatic stress disorder, or subjective cognitive complaints, respectively). The World Health Organization Quality of Life-Bref was used to determine QOL. A reference group of the Dutch general population was used for comparison of QOL scores. RESULTS: The participation rate was 62 % (n = 173). At the time of the study, 30.1 % (n = 52) of the investigated patients had psychological complaints. No relation between psychological complaints and somatic severity or type of injury was found. Patients who were employed before the accident or resumed working reported less psychological complaints. Use of any medication before the accident and treatment for pre-accidental psychological problems were positively related to psychological complaints afterwards. QOL of severely injured patients was impaired in comparison with the general Dutch population, but only for those with psychological complaints. CONCLUSIONS: Psychological complaints seem to be an important and underestimated factor for a decreased QOL among severely injured patients.

Extracellular matrix formation after transplantation of human embryonic stem cell-derived cardiomyocytes.

Transplantation of human embryonic stem cell-derived cardiomyocytes (hESC-CM) for cardiac regeneration is hampered by the formation of fibrotic tissue around the grafts, preventing electrophysiological coupling. Investigating this process, we found that: (1) beating hESC-CM in vitro are embedded in collagens, laminin and fibronectin, which they bind via appropriate integrins; (2) after transplantation into the mouse heart, hESC-CM continue to secrete collagen IV, XVIII and fibronectin; (3) integrin expression on hESC-CM largely matches the matrix type they encounter or secrete in vivo; (4) co-transplantation of hESC-derived endothelial cells and/or cardiac progenitors with hESC-CM results in the formation of functional capillaries; and (5) transplanted hESC-CM survive and mature in vivo for at least 24 weeks. These results form the basis of future developments aiming to reduce the adverse fibrotic reaction that currently complicates cell-based therapies for cardiac disease, and to provide an additional clue towards successful engraftment of cardiomyocytes by co-transplanting endothelial cells.

A coculture model mimicking the intestinal mucosa reveals a regulatory role for myofibroblasts in immune-mediated barrier disruption.

The pathogenesis of Crohn's disease involves a mucosal inflammatory response affecting the barrier function of the gut. Myofibroblasts directly underlining the intestinal epithelium may have a regulatory role in immune-mediated barrier disruption. A coculture system of T84 epithelial and CCD-18Co myofibroblasts was established in order to mimic the in situ spatial interactions between these cell types and to evaluate their role in barrier: integrity. Lamina propria mononuclear cells (LPMC) were introduced in co- and monocultures. Effects of immune cells on barrier integrity was determined by measuring resistance and permeability for macromolecules. Introduction of LPMC in both culture systems caused a time-dependent decrease in barrier integrity. This was found to be less pronounced in cocultures indicating a regulatory role for mesenchymal cells. The effects were also found to depend on the route of LPMC stimulation. Additional analyses suggested that the regulatory role of myofibroblasts in barrier integrity involves production of growth factors.

Protection of chickens from Newcastle and Marek's diseases with a recombinant herpesvirus of turkeys vaccine expressing the Newcastle disease virus fusion protein.

Recombinant strains of herpesvirus of turkeys (HVT) were constructed that contain either the fusion protein gene or the hemagglutinin-neuraminidase gene of Newcastle disease virus (NDV) inserted into a nonessential gene of HVT. Expression of the NDV antigens was regulated from a strong promoter element derived from the Rous sarcoma virus long terminal repeat. Recombinant HVT strains were stable and fully infectious in cell culture and in chickens. Chickens receiving a single intra-abdominal inoculation at 1 day of age with recombinant HVT expressing the NDV fusion protein had an immunological response and were protected (> 90%) against lethal intramuscular challenge at 28 days of age with the neurotropic velogenic NDV strain Texas GB. Recombinant HVT expressing the NDV hemagglutinin-neuraminidase provided partial protection (47%) against the same challenge. Chickens vaccinated with recombinant HVT vaccines had low levels of protection against NDV replication in the trachea when challenged ocularly. Recombinant HVT vaccines and the parent HVT strain provided similar levels of protection to chickens challenged with the very virulent RB1B strain of Marek's disease virus, indicating that insertion of foreign sequences into the HVT genome did not compromise the ability of HVT to protect against Marek's disease.

Demonstration of the genetic stability of a Mycoplasma gallisepticum strain following in vivo passage.

A Mycoplasma gallisepticum strain designated 6/85 (MGI) exhibiting reduced virulence for both chickens and turkeys was sequentially passaged 10 times in each species. DNA extracted from organisms before passage and those isolated after the third, sixth, and 10th passages was studied by restriction endonuclease DNA analysis using BamHI, BglII, EcoRI, HindIII, and PstI endonucleases. The virulent-type strain designated S6 was used as a comparison. Comparison of DNA fragment patterns of MGI and S6 strains showed distinct differences, although some similarities were evident. Passage of the strain in vivo did not affect DNA fragment patterns of the MGI strain. Electrophoretic protein patterns produced by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed very similar band patterns in both the MGI and S6 strains. The most notable differences were seen in bands located in the molecular-mass regions of approximately 46.5, 50-54, 58-64, and 105-140 kilodaltons. Alteration of band pattern profiles following in vivo passage of the MGI strain was apparent in a single band at approximately 86 kilodaltons that appeared to stain more intensely following passage.

Pseudorabies virus glycoprotein gI: in vitro and in vivo analysis of immunorelevant epitopes.

Overlapping fragments of the gene encoding glycoprotein gI of pseudorabies virus (PRV; herpesvirus suis 1) were expressed in bacteria. Using the fusion proteins and a panel of monoclonal antibodies (MAbs) against gI as well as swine sera we found that the N-terminal part of gI (residues 33 to approximately 100) contains a highly antigenic and immunogenic domain. Transfer of antibodies binding to this region as well as vaccination with fusion proteins containing the N terminus of gI are able to confer protection to mice against a lethal challenge of virus. The results show that gI, which is non-essential for virus replication in tissue culture, can induce neutralizing and protective antibodies. The potential suitability of fusion proteins encompassing N-terminal parts of gI as diagnostic tools is demonstrated.

Complex between glycoproteins gI and gp63 of pseudorabies virus: its effect on virus replication.

To ascertain the biological functions of different glycoproteins that are nonessential for pseudorabies virus growth in vitro, we have constructed mutants defective in one (or a combination) of these glycoproteins and have examined various aspects of their role in the infective process. We made the following two observations. (i) Glycoproteins gI and gp63 are noncovalently complexed to each other. They are coprecipitated by antisera against either one of these glycoproteins but do not share antigenic determinants: monoclonal antibodies against gp63 do not immunoprecipitate gI from extracts of gp63- mutant-infected cells, and monoclonal antibodies against gI do not immunoprecipitate gp63 from extracts of gI- mutant-infected cells. (ii) Mutants unable to synthesize either gI or gp63 have some common biological characteristics; they have a growth advantage in primary chicken embryo fibroblasts. Furthermore, we have shown previously that in conjunction with glycoprotein gIII, gI and gp63 are necessary for the expression of virulence (T. C. Mettenleiter, C. Schreurs, F. Zuckermann, T. Ben-Porat, and A. S. Kaplan, J. Virol. 62, 2712-2717, 1988). These results show that the functional entity affecting virus replication in chicken embryo fibroblasts, as well as affecting virulence, is the complex between gI and gp63. The gI-gp63 complex of pseudorabies virus does not appear to have Fc receptor activity as does its homolog, the gI-gE complex of herpes simplex virus.

Role of glycoprotein gIII of pseudorabies virus in virulence.

Deletion mutants of pseudorabies virus unable to express glycoprotein gIII, gI, or gp63 or double and triple mutants defective in these glycoproteins were constructed, and their virulence for day-old chickens inoculated intracerebrally was determined. Mutants of wild-type pseudorabies virus defective in glycoprotein gIII, gI, or gp63 were only slightly less virulent (at most, fivefold) for chickens than was the wild-type virus. However, mutants defective in both gIII and gI or gIII and gp63 were avirulent for chickens, despite their ability to grow in cell culture in vitro to about the same extent as mutants defective in gIII alone (which were virulent). These results show that gIII plays a role in virulence and does so in conjunction with gI or gp63. The effect of gIII on virulence was also shown when the resident gIII gene of variants of the Bartha vaccine strain (which codes for gIIIB) was replaced with a gIII gene derived from a virulent wild-type strain (which codes for gIIIKa); gIIIKa significantly enhanced the virulence of a variant of the Bartha strain to which partial virulence had been previously restored by marker rescue. Our results show that viral functions that play a role in the virulence of the virus (as measured by intracerebral inoculation of chickens) may act synergistically to affect the expression of virulence and that the ability of the virus to grow in cell culture is not necessarily correlated with virulence.

Glycoprotein gIII of pseudorabies virus is multifunctional.

One of the major glycoproteins of pseudorabies virus, gIII, is nonessential for growth in cell culture. Mutants defective in gIII, however, consistently yield lower titers of infectious virus (3- to 20-fold) than does wild-type virus. The interactions of gIII- mutants with their host cells were compared with those of wild-type virus in an attempt to uncover the functions of gIII. We show that gIII plays a major role in the stable adsorption of the virus to its host cell; in the absence of gIII, the rate of adsorption is reduced and adsorption is easily reversed by washing. Thus, adsorption of pseudorabies virus can be said to occur in at least the following two ways: (i) a gIII-mediated rapid adsorption or (ii) a slower and more labile adsorption that is independent of gIII. After virions have been complexed with monoclonal antibodies against gIII (but not some monoclonal antibodies against other glycoproteins), both modes of adsorption were inhibited. Glycoprotein gIII affects virus stability and virus release, as well as adsorption. The effect on virus release is marked when the virus is defective in additional functions. Thus, although we found no obvious difference in the release of virus from gIII- or wild-type virus-infected rabbit kidney cells, release of a gIII-/gI- double mutant from the cells occurred less readily than did release of a gI- mutant. The gIII-/gI- and gIII- mutants, however, adsorbed to cells at a similar rate, indicating that the effects of gIII on adsorption and virus release constitute separate functions. The Bartha vaccine strain of pseudorabies virus has a defective gIII gene and is released poorly from rabbit kidney cells. After the resident Bartha gIII gene was replaced by the gIII gene of wild-type virus, virus release was enhanced considerably. Since inactivation of gIII in wild-type pseudorabies virus did not significantly affect virus release, the Bartha strain must be defective in another function which, in conjunction with gIII, significantly affects virus release. These results indicate again that gIII affects virus release in conjunction with other functions. Also, although the Bartha strain was functionally defective in virus release, it adsorbed to cells as well as wild-type virus did, showing that the effects of gIII on virus adsorption and release constitute separate functions. We conclude that gIII is a multifunctional glycoprotein.

Host cell-specific growth advantage of pseudorabies virus with a deletion in the genome sequences encoding a structural glycoprotein.

Several attenuated strains of pseudorabies virus contain genomes that carry a deletion in their short unique (Us) component. The sizes of the deletions are different in the various attenuated strains; the deletions may include part of one of the inverted repeats as well as part of the Us region of the genome. In most cases, the deletion includes the gene encoding the glycoprotein gI. The attenuated strains with a deletion in their S component have a common history of having been cultivated in chicken embryo fibroblasts (CEF). We show here that passage of wild-type virus in CEF promotes the emergence of populations of virions with a deletion in their S component. The emergence of these mutants is the result of their growth advantage over the wild type and is related to the lack of expression of gI, as shown by the following. (i) The Norden strain (which has a deletion in the Us) was marker rescued to restore an intact Us. The nonrescued Norden strain had a growth advantage over the rescued Norden strain in CEF. (ii) Passage of wild-type (gI+) virus in CEF but not in rabbit kidney or pig kidney cells resulted invariably in the emergence of virions whose genomes had a deletion in the S component. (iii) Passage of a gI- mutant in CEF did not result in the emergence of such virions. The emergence of virions with a deletion in their S component thus appears to be linked to gI expression. We conclude that gI is deleterious to the growth of pseudorabies virus in CEF and that this effect is cell type specific.

Role of pseudorabies virus glycoprotein gI in virus release from infected cells.

The Bartha vaccine strain of pseudorabies virus has a deletion in the short unique (Us) region of its genome which includes the genes that code for glycoproteins gI and gp63 (E. Petrovskis, J. G. Timmins, T. M. Gierman, and L. E. Post, J. Virol. 60:1166-1169, 1986). Restoration of an intact Us to the Bartha strain enhances its ability to be released from infected rabbit kidney cells and increases the size of the plaques formed on these cells (T. Ben-Porat, J. M. DeMarchi, J. Pendrys, R. A. Veach, and A. S. Kaplan, J. Virol. 57:191-196, 1986). To determine which gene function plays a role in virus release from rabbit kidney cells, deletions were introduced into the genomes of both wild-type virus and the "rescued" Bartha strain (Bartha strain to which an intact Us had been restored) that abolish the expression of either the gI gene alone or both gI and gp63 genes. The effect of these deletions on the phenotype of the viruses was studied. Deletion mutants of wild-type virus defective in either gI or gI and gp63 behave like wild-type virus with respect to virus release and plaque size on rabbit kidney cells. Deletion of gI from the rescued Bartha strain, however, strongly affects virus release and causes a decrease in plaque size. We conclude that gI affects virus release but that at least one other viral function also affects this process. This function is defective in the Bartha strain but not in wild-type virus; in its absence gI is essential to efficient release of the virus from rabbit kidney cells.