Estimating Sepsis Incidence Using Administrative Data and Clinical Medical Record Review

Importance

Despite the large health burden, reliable data on sepsis epidemiology are lacking; studies using International Statistical Classification of Diseases and Related Health Problems (ICD)-coded hospital discharge diagnosis for sepsis identification suffer from limited sensitivity. Also, ICD data do not allow investigation of underlying pathogens and antimicrobial resistance.

Objectives

To generate reliable epidemiological estimates by linking data from a population-based database to a reference standard of clinical medical record review.

Design, Setting, and Participants

This was a retrospective, observational cohort study using a population-based administrative database including all acute care hospitals of the Scania region in Sweden in 2019 and 2020 to identify hospital-treated sepsis cases by ICD codes. From this database, clinical medical records were also selected for review within 6 strata defined by ICD discharge diagnosis (both with and without sepsis diagnosis). Data were analyzed from April to October 2022.

Main outcomes and measures

Hospital and population incidences of sepsis, case fatality, antimicrobial resistance, and temporal dynamics due to COVID-19 were assessed, as well as validity of ICD-10 case identification methods compared with the reference standard of clinical medical record review.

Results

Out of 295 531 hospitalizations in 2019 in the Scania region of Sweden, 997 patient medical records were reviewed, among which 457 had sepsis according to clinical criteria. Of the patients with clinical sepsis, 232 (51%) were female, and 357 (78%) had at least 1 comorbidity. The median (IQR) age of the cohort was 76 (67-85) years. The incidence of sepsis in hospitalized patients according to the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3) criteria in 2019 was 4.1% (95% CI, 3.6-4.5) by medical record review. This corresponds to an annual incidence rate of 747 (95% CI, 663-832) patients with sepsis per 100 000 population. No significant increase in sepsis during the COVID-19 pandemic nor a decrease in sepsis incidence when excluding COVID-19 sepsis was observed. Few sepsis cases caused by pathogens with antimicrobial resistance were found. The validity of ICD-10-based case identification in administrative data was low.

Conclusions and Relevance

In this cohort study of sepsis epidemiology, sepsis was a considerable burden to public health in Sweden. Supplying administrative data with information from clinical medical records can help to generate reliable data on sepsis epidemiology.

Use of healthcare before and after sepsis in Sweden: a case-control study

OBJECTIVES

The aim of this study was to compare readmissions and death between sepsis and non-sepsis hospitalisations the first year after discharge, and to investigate what diagnoses patients with sepsis present with at readmission. The aim was also to evaluate to what degree patients hospitalised for sepsis seek medical attention prior to hospitalisation.

DESIGN

Retrospective case-control study with data validated through clinical chart review. A disproportionate stratified sampling model was used to include a relatively larger number of sepsis hospitalisations.

SETTING

All eight public hospitals in region Scania, Sweden (1 January to 3 December 2019).

PARTICIPANTS

There were 447 patients hospitalised for sepsis (cases), and 541 hospitalised for other causes (control) identified through clinical chart review.

OUTCOME MEASURES

Cox regression was used to analyse readmission and death the year after discharge, and logistic regression was used to analyse healthcare the week prior to hospitalisation. Both analyses were made unadjusted, and adjusted for age, sex and comorbidities.

RESULTS

Out of patients who survived a sepsis hospitalisation, 48% were readmitted the year after discharge, compared with 39% for patients without sepsis (HR 1.50, 95% CI 1.03 to 2.19), p=0.04. The majority (52%) of readmissions occurred within 90 days and 75% within 180 days. The readmissions were most often caused by infection (32%), and 18% by cardiovascular disease. Finally, 34% of patients with sepsis had sought prehospital contact with a physician the week before hospitalisation, compared with 22% for patients without sepsis (OR 1.80, 95% CI 1.06 to 3.04), p=0.03.

CONCLUSION

Patients hospitalised for sepsis had a higher risk of readmission the year after discharge compared with patients without sepsis. The most common diagnoses at readmission were infection followed by cardiovascular disease. With better follow-up, some of these readmissions could potentially be prevented. Patients hospitalised for sepsis had sought prehospital contact the week prior to hospitalisation to a greater extent than patients without sepsis.

Incidence, detection and outcome of differentiated thyroid cancer in Western Sweden

Background

It is unclear whether the increasing incidence of thyroid cancer (TC) due to increased diagnosis of small and indolent tumours might mask a real increase of clinically significant cancers. The aim of this study was to correlate surgery, pathology and outcome data of individual patients to the mode of primary detection (palpation, by imaging or incidental) to assess if TC incidence has increased.

Methods

The Swedish Cancer Registry identified all patients with TC in Västra Götaland County representing approximately 1.6 million inhabitants. Clinical information was retrieved from medical records of patient cohorts from three study intervals (2001–2002, 2006–2007 and 2011–2014) comprising 60 per cent of all TC patients. Data were also obtained from the NORDCAN registry to compare of TC incidence with other Nordic countries.

Results

Between 2001 and 2014, the annualized standard incidence rate/100 000 population (ASR) of TC increased from 3.14 to 10.71 in women and from 1.12 to 3.77 in men. This was higher than the mean incidence for Sweden but similar to that in Norway and Finland. Differentiated TC (DTC) increased more than threefold. The majority of tumours (64 per cent) were detected by palpation. Larger tumours (10–20, 21–40 and greater than 40 mm) increased as much as microcarcinomas (less than 10 mm). Only 5 per cent of the tumours were detected by imaging. All disease-specific deaths (8.5 per cent of DTC in the first two cohorts) and most patients with recurrent or persistent disease (6.6 per cent of DTC cases) were diagnosed due to tumour-related symptoms.

Conclusion

DTC in Western Sweden gradually increased between 2001 and 2014. The majority of tumours were detected by palpation suggesting a real increase in the incidence of clinically significant thyroid malignancies.

Microbiota of bovine milk, teat skin, and teat canal: Similarity and variation due to sampling technique and milk fraction

The aim of this study was to evaluate the effect of sampling technique and milk fraction on bovine milk microbiota data and to compare the microbiota in milk to microbiota on the teat end and in the teat canal. Representative milk samples are highly important for assessment of bacteriological findings and microbiota in milk. Samples were obtained from 5 healthy lactating dairy cows at udder quarter level during 1 milking. Swab samples from the teat end and teat canal, and milk samples collected using different techniques and in different milk fractions were included. Milk was collected by hand stripping and through a teat canal cannula before and after machine milking, through a trans-teat wall needle aspirate after milking, and from udder quarter composite milk. The microbiota of the samples was analyzed with sequencing of the V1-V3 region of the 16S rRNA gene. In addition, somatic cell counts and bacterial cultivability were analyzed in the milk samples. Microbiota data were analyzed using multivariate methods, and differences between samples were tested using analysis of similarity (ANOSIM). Differences between samples were further explored via individual studies of the 10 most abundant genera. The microbiota on the teat end, in the teat canal, and in udder quarter composite milk, collected using a milking machine, differed in composition from the microbiota in milk collected directly from the udder quarter. No differences in milk microbiota composition were detected between hand-stripped milk samples, milk samples taken through a teat canal cannula, or milk samples taken as a trans-teat wall needle aspirate before or after milking. We conclude that for aseptic milk samples collected directly from the lactating udder quarter, sampling technique or milk fraction has minor effect on the microbiota composition.

Evaluating risk factors for re-exploration due to postoperative neck hematoma after thyroid surgery: a nested case-control study

Purpose

Postoperative bleeding after thyroid surgery remains a potentially lethal complication. Outpatient thyroidectomy is an increasing trend in the high volume centers. There is a need to identify risk factors for postoperative bleeding in order to select proper patients for outpatient thyroidectomy. This study aimed to investigate this issue using a national population-based register.

Material and method

A nested case-control study on patients registered in the Swedish national register for endocrine surgery (SQRTPA) was performed. Patients with postoperative bleeding were matched 1:1 by age and gender to controls. Additional information on cases and controls was obtained from attending surgeons using a questionnaire. Risk factors for postoperative bleeding were evaluated with logistic regression and are presented as odds ratios (ORs) with 95% confidence intervals (CIs). The time of bleeding in relation to surgery was also investigated.

Results

There were 9494 operations, and 174 (1.8%) of them involved postoperative bleeding. In the whole cohort, patients with postoperative bleeding were older, 58 (46–69) vs. 49 (37–62) years, than patients without, p < 0.01. Male patients had a higher risk of bleeding, OR 2.18 (95% CI 1.58–2.99). In the case-control cohort, drain was an independent risk factor for bleeding, OR 1.64 (1.05–2.57). Two-thirds of patients bled within 6 h after surgery. The incidence of bleeding after 24 h was 10%.

Conclusion

High age, male gender, and drain are independent risk factors for bleeding after thyroid surgery. Even with careful patient selection, prolonged observation might be necessary in thyroid surgery.

A Nested Case-Control Study on the Risk of Surgical Site Infection After Thyroid Surgery

Introduction

It is unclear if antibiotic prophylaxis reduces the risk of surgical site infection (SSI) in thyroid surgery. This study assessed risk factors for SSI and antibiotic prophylaxis in subgroups of patients.

Method and design

A nested case–control study on patients registered in the Swedish National Register for Endocrine Surgery was performed. Patients with SSI were matched 1:1 by age and gender to controls. Additional information on patients with SSI and controls was queried from attending surgeons using a questionnaire. Risk factors for SSI were evaluated by logistic regression analysis and presented as odds ratio (OR) with 95% confidence interval (CI).

Results

There were 9494 operations; 109 (1.2%) patients had SSI. Patients with SSI were older (median 53 vs. 49 years) than patients without SSI p = 0.01 and more often had a cancer diagnosis 23 (21.1%) versus 1137 (12.1%) p = 0.01. In the analysis of patients with SSI versus controls, patients with SSI more often had post-operative drainage 68 (62.4%) versus 46 (42.2%) p = 0.01 and lymph node surgery 40 (36.7%) versus 14 (13.0%) p < 0.01, and both were independent risk factors for SSI, drain OR 1.82 (CI 1.04–3.18) and lymph node dissection, OR 3.22 (95% CI 1.32–7.82). A higher number of 26(62%) patients with independent risk factors for SSI and diagnosed with SSI did not receive antibiotic prophylaxis. Data were missing for 8 (31%) patients.

Conclusion

Lymph node dissection and drain are independent risk factors for SSI after thyroidectomy. Antibiotic prophylaxis might be considered in patients with these risk factors.

Changing seasonal variation in births by sociodemographic factors: a population-based register study

STUDY QUESTION

Have seasonal variations in births by factors related to maternal education, age, parity and re-partnering changed over a 72-year period?

SUMMARY ANSWER

Seasonal variation in births has been reduced overall but also changed its pattern over the last seven decades.

WHAT IS KNOWN ALREADY

The number of births varies markedly by season, but the causes of this variation are not fully understood. Seasonality of births is, in some populations, strongly influenced by sociodemographic factors.

STUDY DESIGN SIZE DURATION

A longitudinal study design was used by analysing the seasonal variation in live births between 1940 and 2012, and relating it to mothers' sociodemographic characteristics at the time of childbirth (maternal education, age, parity and re-partnering).

PARTICIPANTS/MATERIALS SETTING METHODS

Register data on 6 768 810 live births in Sweden between 1940 and 2012 were used. Information on biological parents are available for more than 95% of all births. Multinomial logistic regressions were used to calculate predicted probabilities of giving birth for each calendar month.

MAIN RESULTS AND THE ROLE OF CHANCE

Between 1940 and 1999, Swedish birth rates showed the typical seasonal variation with high numbers of births during the spring, and low numbers of births during the last quarter of the year. However, during the 21st century, the seasonal variation in fertility declined so that only minor variation in birth rates between February and September now remains. Still, the pattern of low birth rates at the end of the year remains and has even become more pronounced from the 1980s onwards. The characteristic 'Christmas effect' that used to be visible in September has vanished over the last 30 years. The roles in seasonal variation of maternal education, the mother's age, parity and instances where the mother has re-partnered between subsequent births changed during the second half of the 20th century. From 1980s onwards, the decline in birth rates during the last quarter of the year became particularly pronounced among highly educated mothers. Over the 72 years studied, the seasonal variation among first-time mothers declined steadily and has almost disappeared at the end of the study period. Using data that cover ~180 000 births in each month, all meaningful results are statistically significant.

LIMITATIONS REASONS FOR CAUTION

The study uses data from one Nordic country only, making it difficult to draw conclusions that may hold for other countries.

WIDER IMPLICATIONS OF THE FINDINGS

The typical seasonal variation reported for Sweden between 1940 and 1999, with high numbers of births during the spring and low numbers of births during the last quarter of the year, is in line with results from most other European countries during the same time period. However, the significant decline in seasonal variation in the early 21st century is a novel development. The study underlines that in a society with low fertility and efficient birth control, active choices and behaviours associated with an individual's sociodemographic characteristics tend to matter more for the seasonal timing of childbearing than environmental factors related to the physiological ability to reproduce and cultural-behavioural factors related to the frequency of intercourse.

STUDY FUNDING/COMPETING INTERESTS

The study was funded by the Swedish Research Council (Vetenskapsrådet) via the Swedish Initiative for Research on Microdata in the Social and Medical Sciences (SIMSAM): Stockholm University SIMSAM Node for Demographic Research (grant registration number 340-2013-5164). The authors declare no conflicts of interest.

TRIAL REGISTRATION NUMBER

Not applicable.

The evaluation of extracorporeal shockwave therapy in naturally occurring osteoarthritis of the stifle joint in dogs

Extracorporeal shockwave therapy (ESWT) has expanded from the original uses of human urinary calculi treatment to veterinary orthopaedic applications. This paper investigates the feasibility and efficacy of treating dogs with osteoarthritis of the stifle joint with ESWT. In this study, dogs with persistent stifle lameness despite previous surgical or medical treatment were either treated with ESWT or served as untreated controls. The more lame rear limb of each dog was determined by force platform analysis. The range of motion (ROM) of the stifle joints was assessed by goniometry. Force platform gait analysis and goniometry were performed on both groups for four visits at threeweek intervals and a final examination four weeks later. Shock wave therapy was performed three times on the treated dogs, once at each of the first three examinations. A placebo treatment consisting of clipping and wetting the hair was performed on the control dogs. The vertical forces were evaluated for objective analysis of treatment response. For peak vertical force (PVF), four of seven treated dogs improved, while only one of five of control dogs improved. The PVF for the within group analysis did not show any significant change for the treated group, however, the control group has a significant decrease (p=0.05) in PVF consistent with an increase in lameness. The range of motion (ROM) of the stifle joint improved in five of seven treated dogs and three of five controls. Dogs in the treated group had a trend toward increased ROM (p=0.07) and a ‘positive slope’ when compared to dogs in the control group which did not have a significant change (p=0.78) and had a negative slope indicating the dogs were developing a decrease in ROM. The subjective data provided by client questionnaire did not show significant difference between groups.

Mode of delivery and the probability of subsequent childbearing: a population-based register study

OBJECTIVE

To investigate the relationship between mode of first delivery and probability of subsequent childbearing.

DESIGN

Population-based study.

SETTING

Nationwide study in Sweden.

POPULATION

A cohort of 771 690 women who delivered their first singleton infant in Sweden between 1992 and 2010.

METHODS

Using Cox's proportional-hazards regression models, risks of subsequent childbearing were compared across four modes of delivery. Hazard ratios (HRs) were calculated, using 95% confidence intervals (95% CIs).

MAIN OUTCOME MEASURES

Probability of having a second and third child; interpregnancy interval.

RESULTS

Compared with women who had a spontaneous vaginal first delivery, women who delivered by vacuum extraction were less likely to have a second pregnancy (HR 0.96, 95% CI 0.95-0.97), and the probabilities of a second childbirth were substantially lower among women with a previous emergency caesarean section (HR 0.85, 95% CI 0.84-0.86) or an elective caesarean section (HR 0.82, 95% CI 0.80-0.83). There were no clinically important differences in the median time between first and second pregnancy by mode of first delivery. Compared with women younger than 30 years of age, older women were more negatively affected by a vacuum extraction with respect to the probability of having a second child. A primary vacuum extraction decreased the probability of having a third child by 4%, but having two consecutive vacuum extraction deliveries did not further alter the probability.

CONCLUSIONS

A first delivery by vacuum extraction does not reduce the probability of subsequent childbearing to the same extent as a first delivery by emergency or elective caesarean section.

The evaluation of extracorporeal shockwave therapy in naturally occurring osteoarthritis of the stifle joint in dogs

Extracorporeal shockwave therapy (ESWT) has expanded from the original uses of human urinary calculi treatment to veterinary orthopaedic applications. This paper investigates the feasibility and efficacy of treating dogs with osteoarthritis of the stifle joint with ESWT. In this study, dogs with persistent stifle lameness despite previous surgical or medical treatment were either treated with ESWT or served as untreated controls. The more lame rear limb of each dog was determined by force platform analysis. The range of motion (ROM) of the stifle joints was assessed by goniometry. Force platform gait analysis and goniometry were performed on both groups for four visits at three-week intervals and a final examination four weeks later. Shock wave therapy was performed three times on the treated dogs, once at each of the first three examinations. A placebo treatment consisting of clipping and wetting the hair was performed on the control dogs. The vertical forces were evaluated for objective analysis of treatment response. For peak vertical force (PVF), four of seven treated dogs improved, while only one of five of control dogs improved. The PVF for the within group analysis did not show any significant change for the treated group, however, the control group has a significant decrease (p = 0.05) in PVF consistent with an increase in lameness. The range of motion (ROM) of the stifle joint improved in five of seven treated dogs and three of five controls. Dogs in the treated group had a trend toward increased ROM (p = 0.07) and a 'positive slope' when compared to dogs in the control group which did not have a significant change (p = 0.78) and had a negative slope indicating the dogs were developing a decrease in ROM. The subjective data provided by client questionnaire did not show significant difference between groups.

A placebo-controlled study of high dose buprenorphine in opiate dependents waiting for medication-assisted rehabilitation in Oslo, Norway

AIMS

To evaluate whether buprenorphine. even without additional control and psychosocial treatment and support, alleviates the problems faced by patients waiting for medication assisted rehabilitation (MAR).

DESIGN

A randomized, double-blind, 12-week study of Subutex versus placebo without additional support as an interim therapy.

PARTICIPANTS

One hundred and six patients, 70 males and 36 females, waiting for MAR in Oslo. The average age was 38 years with an average history of heroin use of 20 years. Fifty-five patients were assigned to buprenorphine and 51 to a placebo.

INTERVENTION

Subutex or placebo sublingual tablets were given under supervision in a daily dose of 16 mg with the exception of a double dose on Saturday and no dose on Sunday.

MEASUREMENT

Retention, compliance, self-reported drug-abuse, wellbeing and mental health.

FINDINGS

The average number of days of participation was significantly higher in the buprenorphine group, 42 (median: 29) compared to 14 (median: 11) for the placebo group (P < 0.001). The retention of patients after 12 weeks was 16 patients in the buprenorphine group and one patient in the placebo group. The buprenorphine group had a larger decrease in reported opioid use (p < 0.001) and in reported use of other drugs, tablets and alcohol abuse (p < 0.01). The group also showed a stronger increase in wellbeing (p < 0.01) and life satisfaction (p < 0.05). None of the participants died.

CONCLUSION

The patients waiting for MAR benefited significantly from the buprenorphine as an interim therapy according to retention, self-reported use of drugs and wellbeing. However, the patients had difficulties in remaining in treatment over time without psychosocial support.

Occurrence of Ergot (Sugary Disease) Incited by a Sphacelia sp. on Sorghum in Mississippi in 1997

Ergot (sugary disease) incited by a Sphacelia sp. was observed on Sorghum bicolor (L.) Moench var. Sweet Leaf II at Leland and Pop-larville, MS, in October 1997. The disease was characterized by droplets of a thick, sticky, semi-transparent secretion similar to aphid honeydew. The caryopsis of infected florets was converted to relatively soft, chalky pink, tumescent, immature sclerotia (1.5 to 1.7 × 4 mm) with blunt ends. Abundant conidia (11 to 17 × 5 to 7 μm) were produced on stromatic tissue and in large numbers in the sugary secretion. This fungus is similar to that described by Zummo in West Africa (2). Velazquez-Valle et al. (1) recently reported the distribution of Claviceps africana Frederiksen, Mantle & de Milliano in the United States in 1997. The Sphacelia stage of the fungus found in Mississippi is similar to that reported from other areas of the U.S. Our report extends the range for this fungus, which is contiguous to those areas reported by Velazquez-Valle et al. (1). References: (1) R. Velazquez-Valle et al. 37th Annu. Mtg. Carib. Div., Am. Phytopa-thol. Soc., San Jose, Costa Rica, No. 77, 1997. (2) N. Zummo. 1984. Sorghum Diseases in West Africa. An Illustrated Text. USDA/USAID, Zaria, Nigeria.

SV40 T-antigen-binding sites within the 5'-flanking regions of human U1 and U2 genes

The 5' flanking regions of the genes (U1 and U2) encoding the human U1 and U2 small nuclear RNAs (snRNAs) each contain sequences that bind specifically to the simian virus (SV40) large tumor antigen (T.Ag). Substitution of these sites with sequences that lack T.Ag-binding sites did not block accumulation of U1 or U2 snRNA in a variety of cell types, but deletion of these regions resulted in the total loss of expression. Thus, these sequences may serve only a spacing function, and the T.Ag-binding sites appear not to be necessary for expression. However, coexpression of T.Ag markedly reduced expression of a U1 gene containing a high-affinity T.Ag-binding site (from the SV40 genome) in place of the U1 T.Ag-binding site. In contrast, coexpression of T.Ag enhanced synthesis of U2, but not U1, snRNA, independent of the presence of the T.Ag-binding sites. Thus, while the consensus T.Ag-binding sites within the U1 and U2 promoter regions do not appear to influence expression, the binding of SV40 T.Ag to a high-affinity site can lead to significant repression of a strong snRNA promoter, and T.Ag can enhance expression of another in the absence of a known binding site.

Equine infectious anemia virus derived from a molecular clone persistently infects horses

A full-length molecular clone of equine infectious anemia virus (EIAV) was isolated from a persistently infected canine fetal thymus cell line (Cf2Th). Upon transfection of equine dermis cells, the clone, designated CL22, yielded infectious EIAV particles (CL22-V) that replicated in vitro in both Cf2Th cells and an equine dermis cell strain. Horses infected with CL22-V developed an antibody response to viral proteins and possessed viral DNA in peripheral blood mononuclear cells, as determined by polymerase chain reaction assays. In addition, horses infected with CL22-V became persistently infected and were capable of transmitting the infection by transfer of whole blood to uninfected horses. However, CL22-V, like the parental canine cell-adapted virus, did not cause clinical signs in infected horses. Reverse transcriptase assays of CL22-V- and virulent EIAV-infected equine mononuclear cell cultures indicated that the lack of virulence of CL22-V was not due to an inability to infect and replicate in equine mononuclear cells in vitro.

The viral hypothesis of Alzheimer's disease. Absence of antibodies to lentiviruses

To evaluate the possible role of lentiviruses in Alzheimer's disease we searched for cross-reactive antibodies to human immunodeficiency virus type 1, caprine arthritis encephalitis virus, and equine infectious anemia virus in Alzheimer's disease, Down's syndrome, and related dementing illnesses in serum samples and cerebrospinal fluid samples and in healthy age-matched control subjects. No cross-reactive antibodies were detected.

Human B-lymphotropic virus (human herpesvirus-6)

Human B-lymphotropic virus (HBLV), also known as human herpesvirus-6 (HHV-6) was first isolated in 1986 from AIDS patients and patients with other lymphoproliferative disorders. HBLV is distinct from known human herpesviruses, biologically, immunologically and by molecular analysis. HBLV can infect and replicate in fresh and established lines of hemopoietic cells and cells of neural origin, suggesting wide tropism. The prevalence of HBLV antibody in the normal population was 26% though clear differences between different populations were observed. The prevalence of HBLV antibody an elevated antibody titer was higher in sera from certain malignancies, Sjögren's syndrome and sarcoidosis. Antibody to HBLV was also elevated in AIDS patients and patients with chronic fatigue syndrome. HBLV-DNA was detected in some B-cell lymphomas. The broad in vitro tropism, combined with immunological and molecular evidence of HBLV infection in individuals raise the question of the pathogenicity of this virus in some diseases. Because in vitro co-infection of CD4 cells by HBLV and HIV leads to enhanced degeneration, this raises the possibility that infection in AIDS patients by both viruses can aggravate the HIV-induced immunodeficiency. Specific reagents and immunological and molecular assays are currently being investigated, which will aid in virus detection in cells from patients, and in elucidating the possible pathogenesis of HBLV.

Nucleotide sequence analysis of equine infectious anemia virus proviral DNA

The nucleotide sequence of the integrated form of the genome of the equine infectious anemia virus was determined. By comparison with LTR sequences of other retroviruses, signals for the control of viral gene transcription and translation could be identified in the EIAV LTR. Open reading frames for gag and pol genes were identified and their sequences matched very closely to those determined previously by others. However, in the present study, the pol gene reading frame was open throughout its entire length. The open reading frame for the env gene product was constructed from the sequences of two independent EIAV clones. Thus, a noninfectious genomic-length clone was shown to contain a frameshift mutation approximately in the middle of the presumed env gene coding sequence, whereas the sequence of another clone was open in this region. The deduced amino acid sequences of the EIAV gag and pol products showed closer evolutionary relationships to those of known lentiviruses than to other retroviruses. There was also partial sequence homology between predicted env gene products of EIAV, visna virus, and HTLV-III/LAV. Sequences analogous to the sor region of other lentiviruses could not be identified in our EIAV clone. A short open reading frame at the 3' end of the genome that overlapped env but not the 3' LTR was present but lacked significant sequence similarity to the 3' open reading frames of other lentiviruses. Thus, the sequence and general structure of EIAV most closely resemble those of known lentiviruses.

Molecular cloning and physical characterization of integrated equine infectious anemia virus: molecular and immunologic evidence of its close relationship to ovine and caprine lentiviruses

Molecular clones of the integrated form of the genome of equine infectious anemia virus (EIAV), the etiologic agent of a naturally occurring, worldwide disease of horses, were obtained. The restriction map of a full-length genome was determined. Additional evidence for the close evolutionary relationship between EIAV and a prototype lentivirus (caprine arthritis encephalitis virus) was acquired by Southern blotting and immunological analyses. An interspecies radioimmunoassay was developed in which EIAV and ovine and caprine lentiviruses could be detected equally well. These studies make available precisely defined reagents to pursue the study of the mechanisms of pathogenesis of lentiviral induced diseases.

Interaction of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) with owl monkey kidney cells in enhancing the yields of Herpesvirus saimiri (HVS) and its antigens

Pre- and posttreatment with N-methyl-N'-nitro-nitrosoguanidine (MNNG) of owl monkey kidney (OMK) cells infected with Herpesvirus saimiri (HVS) resulted in one to three logs higher yields of virus, depending upon the dose of MNNG. A higher percentage of cells also showed HVS early antigen (EA) and late antigen (LA) by immunofluorescence when OMK cells infected with HVS were fed with medium containing MNNG. The high yields of HVS were also observed by electron microscopy. MNNG did not induce HVS-EA in HVS nonproducer lymphoblastoid T cells, nor did it enhance TPA-induced EA to LA. The data suggest that MNNG could be useful in obtaining high yields of virus and/or antigen-producing cells for immunofluorescence or other biochemical experiments, especially from those strains of HVS which grow poorly in vitro. The interaction of MNNG and HVS could also be useful for in vitro transformation or in vivo enhancement of the malignant process.

Characterization of the oncornavirus particles in the plasma of guinea pigs with L2C leukemia

The inoculation of L2C guinea pig leukemia cells into strain 2 guinea pigs results in the death of the animals within 12 to 15 days. Death is preceded by the simultaneous appearance in the plasma of (i) elevated leukocyte levels, (ii) extracellular virus particles, and (iii) a particle-associated RNA-directed DNA polymerase. This enzyme activity has a cation preference identical to that of the type B bromodeoxyuridine-induced guinea pig virus, i.e., an Mg2+ optimum at 20 mM and no activity using Mn2+. Competitive molecular hybridization studies also revealed that the plasma of leukemic guinea pigs contained approximately 2 X 10(9) genome equivalents per ml of an RNA that is homologous to the RNA of the bromodeoxyuridine-induced guinea pig virus. Morphological observations indicate that most, but not all, of the extracellular particles observed in leukemia plasma are derived from the intracisternal particles seen in the L2C tumor cells. The possibilities that either two viral populations are present or that the in vivo morphogenesis of the type B bromodexoyuridine-inducible guinea pig virus is markedly different from its in vitro morphogenesis are discussed.

Biochemical properties of the bromodeoxyuridine-induced guinea pig virus

The biophysical and biochemical properties of the virus particles released by guinea pig embryo cells treated with 5-bromo-2'-deoxyuridine (BUdR) have been compared to those of the B-type mouse mammary tumor virus (MMTV) and the C-type Rauscher murine leukemia virus. The high-molecular-weight (60 to 70S) RNA of the BUdR-induced guinea pig virus (GPV) has a molecular weight of 8 X 106 when measred by mixed agarose polyacylamide gel electrophoresis. The virus particles isolated from the tissue culture medium of BUdR-induced guniea pig cells have the following properties in common with MMTV: (i) a buoyant density of 1.18 g/ml in sucrose and 1.21 g/ml in CsCl, and (ii) a DNA polymerase that prefers Mg2+ over Mn2+ in an assay using the synthetic template poly(rC):oligo(dG). No nucleic acid sequence homology between GPV RNA and the viral RNAs of the MMTV, murine leukemia virus, hamster sarcoma virus, or Mason-Pfizer monkey virus could be observed in a competition hybridization assay using the radioactive-labeled GPV 60 to 70S RNA. By this same competition by hybridization assay the frequency of GPV proviral sequences was estimated to be at least 83 per haploid cellular genome of guniea pig cells. No nucleic acid sequences related to be GPV RNA were detected in the DNA of normal tissues of mice, rats, cats, dogs, baboons, or humans by direct RNA-DNA hybridization using radioactive GPV60 to 70S RNA.