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PubMed1994

A factor in human plasma permits persistent expression of E-selectin by human endothelial cells.

E-selectin is an inducible endothelial cell adhesion protein that is a critical element in the binding of leukocytes to activated endothelial cells. It is induced by a variety of pro-inflammatory soluble substances including interleukin-1 (IL-1), tumor necrosis factor (TNF), or bacterial lipopolysaccharide (LPS). In vitro studies of a large vessel endothelial cells demonstrate that stimulation with TNF or IL-1 leads to a rapid, but transient, induction of E-selectin expression that disappears within 24 hours. However, in vivo studies have shown that microvascular endothelial cells persistently express E-selectin in chronic inflammatory states, particularly in the skin where it serves as a homing receptor for memory T cells. Stimulation of dermal-derived microvascular endothelial cells (HDMECs) with single doses of IL-1 alpha, TNF alpha, or LPS resulted in transient but slightly more persistent expression of E-selectin than seen after stimulation of large vessel derived umbilical vein endothelial cells (HUVECs). However, stimulation of either HDMECs or HUVECs with repetitive doses of IL-1 alpha, TNF alpha, or LPS in the presence of human serum or plasma resulted in persistent E-selectin expression in vitro. The persistent E-selectin cell surface expression was associated with persistent E-selectin mRNA expression and correlated with E-selectin-mediated HL-60 binding to endothelial cell monolayers. The effect of human plasma or serum was dose dependent, and fractionation of human plasma by gel filtration demonstrated that the E-selectin persistence activity resolved into high and low molecular peaks. These data demonstrate that human endothelial cells are capable of persistent E-selectin expression in vitro and that factors in human serum or plasma are critical in preventing cytokine refractoriness and loss of E-selectin expression. This study provides a basis to resolve the apparent discrepancies between previous in vivo and in vitro dynamics of E-selectin expression.

Blotting, Northern↗
PubMed2003

Personal persistence, identity development, and suicide: a study of Native and Non-native North American adolescents.

The cross-cultural program of research presented here is about matters of temporal persistence--personal persistence and cultural persistence--and about solution strategies for solving the paradox of "sameness-in-change." The crux of this paradox resides in the fact that, on threat of otherwise ceasing to be recognizable as a self, all of us must satisfy at least two constitutive conditions. The first of these is that selves are obliged to keep moving or die, and, so, must continually change. The second is that selves must also somehow remain the same, lest all notions of moral responsibility and any commitment to an as yet unrealized future become nonsensical. Although long understood as a problem demanding the attention of philosophers, we argue that this same paradox arises in the ordinary course of identity development and dictates the different developmental routes taken by culturally mainstream and Aboriginal youth in coming to the identity-preserving conclusion that they and others are somehow continuous through time. Findings from a set of five studies are presented. The first and second studies document the development and refinement of a method for parsing and coding what young people say on the topic of personal persistence or self-continuity. Both studies demonstrate that it is not only possible to seriously engage children as young as age 9 or 10 years in detailed and codable discussions about personal persistence, but that their reasoning concerning such matters typically proceeds in an orderly and increasingly sophisticated manner over the course of their early identity development. Our third study underscores the high personal costs of failing to sustain a workable sense of personal persistence by showing that failures to warrant self-continuity are strongly associated with increased suicide risk in adolescence. Study four documents this same relation between continuity and suicide, this time at the macrolevel of whole cultures, and shows that efforts by Aboriginal groups to preserve and promote their culture are associated with dramatic reductions in rates of youth suicide. In the final study we show that different default strategies for resolving the paradox of personal persistence and change--Narrative and Essentialist strategies--distinctly characterize Aboriginal and non-Aboriginal youth.

Adolescent↗
PubMed2006

On the causes of persistent apical periodontitis: a review.

Apical periodontitis is a chronic inflammatory disorder of periradicular tissues caused by aetiological agents of endodontic origin. Persistent apical periodontitis occurs when root canal treatment of apical periodontitis has not adequately eliminated intraradicular infection. Problems that lead to persistent apical periodontitis include: inadequate aseptic control, poor access cavity design, missed canals, inadequate instrumentation, debridement and leaking temporary or permanent restorations. Even when the most stringent procedures are followed, apical periodontitis may still persist as asymptomatic radiolucencies, because of the complexity of the root canal system formed by the main and accessory canals, their ramifications and anastomoses where residual infection can persist. Further, there are extraradicular factors -- located within the inflamed periapical tissue -- that can interfere with post-treatment healing of apical periodontitis. The causes of apical periodontitis persisting after root canal treatment have not been well characterized. During the 1990s, a series of investigations have shown that there are six biological factors that lead to asymptomatic radiolucencies persisting after root canal treatment. These are: (i) intraradicular infection persisting in the complex apical root canal system; (ii) extraradicular infection, generally in the form of periapical actinomycosis; (iii) extruded root canal filling or other exogenous materials that cause a foreign body reaction; (iv) accumulation of endogenous cholesterol crystals that irritate periapical tissues; (v) true cystic lesions, and (vi) scar tissue healing of the lesion. This article provides a comprehensive overview of the causative factors of non-resolving periapical lesions that are seen as asymptomatic radiolucencies post-treatment.

Actinomycosis↗
PubMed2004

Persistent dipstick haematuria following renal transplantation.

Despite widespread testing for dipstick haematuria following renal transplantation, there are no published series describing the prevalence and possible causes of this complication in an adult population. A cross-sectional study of 640 renal transplant recipients under review at our follow-up clinic was performed. Persistent haematuria was defined as a minimum of 1+ of blood on urinalysis stick testing detected at not fewer than 75% of clinic visits since its onset, or since the start of routine testing, present over a period of at least 4 weeks. The prevalence of persistent dipstick haematuria was 13.3%. Median serum creatinine was higher in patients with persistent haematuria but age, gender and length of time since transplantation were not significantly different. Potential explanations for persistent haematuria in 21 of 85 affected patients were chronic infection, ureteric stent without chronic infection, regular or intermittent self-catheterization, persistent menstrual bleeding, anticoagulant therapy, graft calculus, and allograft renal cell carcinoma. Recurrent or de novo glomerular disease was confirmed by graft biopsy in 10 of 85 patients. Among the 41 recipients whose original cause of renal failure was IgA nephropathy (IgAN), the prevalence of persistent haematuria was 31.7% compared with 12% in the remaining patients (relative risk 2.6, 95% CI: 1.6-4.3). Persistent haematuria in IgAN patients was not associated with gender, age or time since transplantation. After 29 months of follow-up, 20% of patients with haematuria had progressed to graft failure or death compared with 11.6% of the unaffected group (p = 0.029). However, despite the association with earlier graft failure, haematuria did not predict this endpoint independently of renal function.

Adolescent↗
PubMed2006

Persistent cytomegalovirus infection in kidney allografts is associated with inferior graft function and survival.

The long-term effects of cytomegalovirus (CMV) infections on kidney allografts are unknown. We examined the impact of persistent intragraft CMV infection on long-term kidney allograft function and survival. CMV was diagnosed in 82/172 renal transplant recipients by antigenemia test and viral cultures. Biopsies from 48 of 82 patients taken after CMV infection and from 15 patients with no previous CMV infection detected were available for the immunohistochemical demonstration of CMV antigens and DNA hybridization in situ. Five-year follow-up data from these 63 patients were analysed. In 17 patients, CMV antigens and/or DNA persisted in the biopsy >2 months after the last positive finding in blood or urine. Patients with persistent intragraft CMV had reduced graft survival (P = 0.041) and Cox regression analysis showed persistent CMV as a risk factor for reduced graft survival (RR: 3.5). Recipients with persistent intragraft CMV had reduced creatinine clearance 1 and 2 years after transplantation (P = 0.007) and in multivariate logistic regression analyses including several potential pre- and posttransplant risk factors, persistent CMV was an independent risk factor for lower clearance at 1 and 2 years (OR: 4.4 and 4.9). Our novel findings show that persistent intragraft CMV infection was associated with reduced kidney allograft function and survival.

Adult↗
PubMed2005

Silencing or permanent activation: host-cell responses in models of persistent Chlamydia pneumoniae infection.

Chlamydia pneumoniae causes respiratory infections. In chronic diseases associated with Chlamydia, such as arteriosclerosis, C. pneumoniae is present in a persistent form, which might participate in pathogenesis of chronic inflammatory disease. To elucidate how these intracellular bacteria modulate host-cells during persistence, we compared the expression pattern of a range of host genes after short (24 h) and long (up to 7 days) times of chlamydia infection in HeLa-cells. One day post infection, in three cell-culture models of persistence, namely treatment with penicillin or IFN-gamma, or iron-depletion, infection induced the genes of CTGF, IL-6, IL-8, IL-11, LIF, EGR-1 and ETV4 in a similar fashion. However, after a longer time, two modes of host-cell reaction emerged that were dependent on the persistence model used. After IFN-gamma and penicillin treatment chlamydia-induced host-cell gene expression was inhibited, while it stayed upregulated in iron-depletion. Human monocytes/macrophages, in which persistence naturally occurs, were additionally investigated: for several genes, UV-inactivated and viable chlamydia caused long-lasting upregulation. Thus, this study reveals (i) the ability of C. pneumoniae to participate in two putative pathomechanisms of persistence, silencing and permanent activation, which might represent different in vivo situations and (ii) a strong dependence on the mode of persistence induction.

Adenovirus E1A Proteins↗
PubMed2004

Obstetric risk factors and persistent increases in brain parenchymal echogenicity in preterm infants.

OBJECTIVE: To assess the risk of persistent (>7 days) increases in brain parenchymal echogenicity in preterm infants and their association with known obstetric risk factors. DESIGN: Case-control study of prospectively collected data. SETTING: A University hospital in Northern Italy. POPULATION: Eighty-five singleton infants between 24 and 34 weeks of gestation with a cranial ultrasonographic diagnosis of persistently increased parenchymal echogenicity without development of cystic degeneration, and 170 control infants with negative cranial ultrasonographic findings. METHODS: A comparison of the prevalence of selected obstetric risk factors between infants with persistent echo-dense lesions and negative controls. MAIN OUTCOME MEASURES: Odds ratios of persistent echo-dense lesions including first-degree interactions between variables. RESULTS: After adjusting for birthweight, logistic regression analysis showed that the only factor associated with an increased risk of persistent brain echo-dense lesions in infants was multiple courses of antenatal steroids (OR = 2.14, 95% CI = 1.11-4.15, P= 0.024). In this group, the risk of persistent echo-dense lesions was particularly high in: (i) mothers receiving dexamethasone rather than betamethasone (P value for interaction = 0.015) and (ii) after expectant management of pre-eclampsia or intrauterine growth retardation (P value for interaction = 0.03). CONCLUSIONS: Multiple doses of antenatal steroids, especially dexamethasone, could influence the prevalence of persistent increases in brain parenchymal echogenicity in preterm infants.

Brain Diseases↗
PubMedDate not supplied

Persistence and adherence of medications for chronic overactive bladder/urinary incontinence in the california medicaid program.

OBJECTIVES: To investigate persistence and adherence of medication treatment in chronic overactive bladder/urinary incontinence (OAB/UI) patients, and to evaluate OAB/UI-related comorbidity events associated with persistence. METHODS: Pharmaceutical outcomes research with a health-care provider perspective was conducted on a California Medicaid (Medi-Cal) chronic OAB/UI population. The primary end point was medication possession ratio (MPR), which was used to measure refill adherence. Secondary end points measuring persistence patterns included discontinuation of OAB drug therapy (medication-uncovered interval > 30 days) and time to discontinuation (period from the index date until the first discontinuation date). Significant factors on nonpersistence were found by using a Cox Proportional Hazards model. Factors contributing to nonadherence (MPR < 0.8) and the relationship between OAB/UI comorbidity events and persistence were examined by logistic regressions. RESULTS: Of 2496 eligible patients, 36.9% had only one OAB/UI prescription. The mean MPR was 0.34 (SD 0.21) and the median was 0.3, indicating that on average only about one-third of period of time since medication initiation was covered by the therapy. Only 122 patients exhibited > 80% adherence during the 6-month follow-up-period. Significant predictors of higher persistence included: white ethnicity, previous hospitalization length, starting with tolterodine or oxybutynin extended-release, and previous use of topical drugs or antipsychotics. Nevertheless, previous depression or urinary tract infection (UTI) diagnosis, polypharmacy, significantly increased the odds of early discontinuation. Treatment discontinuation increased the risk of UTI diagnosis by 37% in the post-treatment period (P = 0.03; OR 1.37; 95% CI 1.03-1.84), but had no significant effect on other OAB/UI-related comorbidities. CONCLUSIONS: For chronic OAB/UI patients identified in this study, both persistence and adherence with medication treatment were suboptimal. These results suggest that persistence and treatment discontinuation remains problematic for the OAB/UI population.

Benzhydryl Compounds↗
PubMed2006

Persistent depression affects adherence to secondary prevention behaviors after acute coronary syndromes.

BACKGROUND: The persistence of depressive symptoms after hospitalization is a strong risk factor for mortality after acute coronary syndromes (ACS). Poor adherence to secondary prevention behaviors may be a mediator of the relationship between depression and increased mortality. OBJECTIVE: To determine whether rates of adherence to risk reducing behaviors were affected by depressive status during hospitalization and 3 months later. DESIGN: Prospective observational cohort study. SETTING: Three university hospitals. PARTICIPANTS: Five hundred and sixty patients were enrolled within 7 days after ACS. Of these, 492 (88%) patients completed 3-month follow-up. MEASUREMENTS: We used the Beck Depression Inventory (BDI) to assess depressive symptoms in the hospital and 3 months after discharge. We assessed adherence to 5 risk-reducing behaviors by patient self-report at 3 months. We used chi2 analysis to compare differences in adherence among 3 groups: persistently nondepressed (BDI < 10 at hospitalization and 3 months); remittent depressed (BDI > or = 10 at hospitalization; < 10 at 3 months); and persistently depressed patients (BDI > or = 10 at hospitalization and 3 months). RESULTS: Compared with persistently nondepressed, persistently depressed patients reported lower rates of adherence to quitting smoking (adjusted odds ratio [OR] 0.23, 95% confidence interval [95% CI] 0.05 to 0.97), taking medications (adjusted OR 0.50, 95% CI 0.27 to 0.95), exercising (adjusted OR 0.57, 95% CI 0.34 to 0.95), and attending cardiac rehabilitation (adjusted OR 0.5, 95% CI 0.27 to 0.91). There were no significant differences between remittent depressed and persistently nondepressed patients. CONCLUSIONS: Persistently depressed patients were less likely to adhere to behaviors that reduce the risk of recurrent ACS. Differences in adherence to these behaviors may explain in part why depression predicts mortality after ACS.

Acute Disease↗
PubMed2004

Persistent nonmalignant pain and analgesic prescribing patterns in elderly nursing home residents.

OBJECTIVES: To determine the prevalence of analgesics used, their prescribing patterns, and associations with particular diagnoses and medications in patients with persistent pain. DESIGN: Cross-sectional study. SETTING: Nursing homes from 10 U.S. states. PARTICIPANTS: A total of 21,380 nursing home residents aged 65 and older with persistent pain. MEASUREMENTS: Minimum Data Set (MDS) assessments on pain, analgesics, cognitive, functional, and emotional status were summarized. Logistic regression models identified diagnoses associated with different analgesic classes. RESULTS: Persistent pain as determined using the MDS was identified in 49% of residents with an average age of 83; 83% were female. Persistent pain was prevalent in patients with a history of fractures (62.9%) or surgery (63.6%) in the past 6 months. One-quarter received no analgesics. The most common analgesics were acetaminophen (37.2%), propoxyphene (18.2%), hydrocodone (6.8%), and tramadol (5.4%). Only 46.9% of all analgesics were given as standing doses. Acetaminophen was usually prescribed as needed (65.6%), at doses less than 1,300 mg per day. Nonsteroidal antiinflammatory drugs (NSAIDs) were prescribed as a standing dose more than 70% of the time, and one-third of NSAIDs were prescribed at high doses. CONCLUSION: In nursing home residents, persistent pain is highly prevalent, there is suboptimal compliance with geriatric prescribing recommendations, and acute pain may be an important contributing source of persistent pain. More effective provider education and research is needed to determine whether treatment of acute pain could prevent persistent pain.

Activities of Daily Living↗
PubMed2006

Acute success and persistence of bidirectional conduction block in the cavotricuspid isthmus one month post cryocatheter ablation of common atrial flutter.

INTRODUCTION: Cryoablation is successful in the treatment of common atrial flutter. Long-term clinical success is mainly dependent on persistence of bidirectional conduction block (BCB) in the inferior cavotricuspid isthmus (CTI). Only few data on persistence of BCB post cryoablation with the reported technique are available. This prospective study aimed to test efficacy of cryo energy and persistence of BCB in the CTI 1 month post cryoablation. METHODS: Cryoablation of the CTI was performed in 50 consecutive patients (64 +/- 12 years, 40 males) with symptomatic common atrial flutter using a novel 9 Fr 8-mm-tip catheter. BCB in the CTI 30 minutes following the final cryoapplication was the ablation endpoint. Thirty days post ablation, persistence of BCB was controlled by repeat electrophysiological study (EPS). RESULTS: In all patients BCB was achieved with a mean of 9 (IQR 7-17.5) cryo applications and a mean cryo time of 2,378 seconds (IQR 1,680-3,474 seconds). In 5 of 50 patients, common atrial flutter recurred within 1 month post cryoablation. In 30 of 32 recurrence-free patients, persistence of BCB was verified. In 2 patients, resumption of isthmus conduction was detectable. Including relapses, 81.1% of patients (30/37) showed persistence of BCB. No patients reported pain during cryoapplication. No procedural complications were observed. CONCLUSIONS: Cryoablation of the CTI using a large-tip catheter is feasible and safe in the treatment of common atrial flutter. Acute and short-term success rates are comparable to those reported for radiofrequency (RF) ablation. Besides short-term clinical success, the persistence of BCB demonstrates efficacy of the cryoablation technique.

Adult↗
PubMed2005

Persistence and differential survival of fecal indicator bacteria in subtropical waters and sediments.

Fecal coliforms and enterococci are indicator organisms used worldwide to monitor water quality. These bacteria are used in microbial source tracking (MST) studies, which attempt to assess the contribution of various host species to fecal pollution in water. Ideally, all strains of a given indicator organism (IO) would experience equal persistence (maintenance of culturable populations) in water; however, some strains may have comparatively extended persistence outside the host, while others may persist very poorly in environmental waters. Assessment of the relative contribution of host species to fecal pollution would be confounded by differential persistence of strains. Here, freshwater and saltwater mesocosms, including sediments, were inoculated with dog feces, sewage, or contaminated soil and were incubated under conditions that included natural stressors such as microbial predators, radiation, and temperature fluctuations. Persistence of IOs was measured by decay rates (change in culturable counts over time). Decay rates were influenced by IO, inoculum, water type, sediment versus water column location, and Escherichia coli strain. Fecal coliform decay rates were significantly lower than those of enterococci in freshwater but were not significantly different in saltwater. IO persistence according to mesocosm treatment followed the trend: contaminated soil > wastewater > dog feces. E. coli ribotyping demonstrated that certain strains were more persistent than others in freshwater mesocosms, and the distribution of ribotypes sampled from mesocosm waters was dissimilar from the distribution in fecal material. These results have implications for the accuracy of MST methods, modeling of microbial populations in water, and efficacy of regulatory standards for protection of water quality.

Animals↗
PubMed1995

Reactivation of persistent Chlamydia trachomatis infection in cell culture.

Gamma interferon induces persistent chlamydial infections in cell culture. These infections are characterized by altered morphologic and biochemical features of the pathogen. These persistent forms are abnormally large and noninfectious and undergo unusual structural and functional changes, including production of a paucity of outer envelope constituents and normal levels of the chlamydial hsp60, an immunopathological antigen. The current investigation evaluates the events that occur during reactivation of infectious Chlamydia trachomatis from persistently infected cell cultures. Transfer of persistent chlamydial organisms to gamma interferon-free medium resulted in recovery of infectivity accompanied by an increase in levels of structural membrane proteins and reorganization of aberrant organisms to morphologically typical elementary bodies. In addition, reactivation of infectious organisms from persistent chlamydiae that were maintained in culture for several weeks was demonstrated. These studies show that persistent C. trachomatis maintains viability for extended periods, illustrate the reversibility of immunologically mediated persistent infections, and characterize reactivation at the ultrastructural and biochemical levels.

Bacterial Proteins↗
PubMed2000

Detection of mRNA transcripts and active transcription in persistent Mycobacterium tuberculosis induced by exposure to rifampin or pyrazinamide.

Mycobacterium tuberculosis can persist in an altered physiological state for many years after initial infection, and it may reactivate to cause active disease. An analogous persistent state, possibly consisting of several different subpopulations of bacteria, may arise during chemotherapy; this state is thought to be responsible for the prolonged period required for effective chemotherapy. Using two models of drug-induced persistence, we show that both microaerophilic stationary-phase M. tuberculosis treated with a high dose of rifampin in vitro and pyrazinamide-induced persistent bacteria in mice are nonculturable yet still contain 16S rRNA and mRNA transcripts. Also, the in vitro persistent, plate culture-negative bacteria incorporate radioactive uridine into their RNA in the presence of rifampin and can rapidly up-regulate gene transcription after the replacement of the drug with fresh medium and in response to heat shock. Our results show that persistent M. tuberculosis has transcriptional activity. This finding provides a molecular basis for the rational design of drugs targeted at persistent bacteria.

Animals↗
PubMed2006

Increased persistence in Escherichia coli caused by controlled expression of toxins or other unrelated proteins.

Bacterial populations contain persisters, cells which survive exposure to bactericidal antibiotics and other lethal factors. Persisters do not have a genetic resistance mechanism, and their means to tolerate killing remain unknown. In exponentially growing populations of Escherichia coli the frequency of persister formation usually is 10(-7) to 10(-5). It has been shown that cells overexpressing either of the toxic proteins HipA and RelE, both members of the bacterial toxin-antitoxin (TA) modules, have the ability to form more persisters, suggesting a specific role for these toxins in the mechanism of persistence. However, here we show that cells expressing proteins that are unrelated to TA modules but which become toxic when ectopically expressed, chaperone DnaJ and protein PmrC of Salmonella enterica, also form 100- to 1,000-fold more persisters. Thus, persistence is linked not only to toxicity caused by expression of HipA or dedicated toxins but also to expression of other unrelated proteins.

Bacterial Proteins↗
PubMed1977

Persistent infection of cultured mammalian cells by Japanese encephalitis virus.

Persistent infections were established by serial undiluted passage of flavivirus Japanese encephalitis virus in a line of rabbit kidney cells (MA-111). The persistently infected cells resembled uninfected cells in most respects. Low levels of infectious virions were released from a small percentage of cells, and a larger and more variable percentage was shown to possess viral antigen by fluorescent-antibody staining. Released viruses were shown to interfere with replication of wild-type Japanese encephalitis virus. Persistently infected MA-111 cells could not be superinfected with homologous wild-type Japanese encephalitis virus but could be superinfected with two heterologous viruses. Transfer of cell culture medium from persistently infected MA-111 cells to a line of African green monkey kidney cells (Vero) resulted in similar persistent infections in the latter cells. Temperature sensitivity and host-cell interferon production were not involved in establishment or maintenance of persistence. Determination of ratios of physical particles to infectious particles revealed that many defective, noninfectious viruses were present, suggesting that defective interfering particles may be responsible for persistency.

Cell Division↗
PubMed1978

Persistent infection of L cells with vesicular stomatitis virus: evolution of virus populations.

A previous report (Youngner et al., J. Virol. 19:90-101, 1976) documented that noncytocidal persistent infection can be established with wild-type vesicular stomatitis virus (VSV) in mouse L cells at 37 degrees C and that a rapid selection of RNA(-), group I temperature-sensitive (ts) mutants consistently occurs in this system. To assess the selective advantage of the RNA(-)ts phenotype, evolution of the virus population was studied in persistent infections initiated in L cells by use of VSV ts 0 23 and ts 0 45, RNA(+) mutants belonging to complementation groups III and V. In L cells persistently infected with ts 0 23, the ts RNA(+) virus population was replaced gradually by viruses which had a ts RNA(-) phenotype. VSV ts 0 45 (V) has another marker in addition to reduced virus yield at 39.5 degrees C: a defective protein (G) which renders virion infectivity heat labile at 50 degrees C. Persistent infections initiated with this virus (ts, heat labile, RNA(+)) evolved into a virus population which was ts, heat resistant, and RNA(-). These findings suggest that the ts phenotype itself is not sufficient to stabilize the VSV population in persistently infected L cells and also indicate that the ts RNA(-) phenotype may have a unique selective advantage in this system. In addition to the selection of ts RNA(-) mutants, other mechanisms which also might operate in the maintenance of persistent VSV infections of L cells were explored. Whereas defective-interfering particles did not seem to mediate the carrier state, evidence was obtained that interferon may play a role in the regulation of persistent infections of L cells with VSV.

L Cells↗
PubMed1981

Comparative study of rabies virus persistence in human and hamster cell lines.

Persistent infections by rabies virus in BHK-21/13S and HEp-2 cells were studied comparatively. No evidence of interferon production, selection of virus-resistant cells, or integration of the viral genome could be found. Persisting viruses replicated efficiently at 34, 36, and 40 degrees C. Both persistently infected cultures released defective interfering virus particles. A cyclical pattern of infection, which was not characteristic of the persistently infected HEp-2 system, was observed in persistently infected BHK cultures. The virus from persistently infected BHK cultures lost its virulence for mice, whereas the virus from persistently infected HEp-2 cultures retained mouse-killing capacity for more than 3 years.

Animals↗