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PubMed2001

Different host-cell shutoff strategies related to the matrix protein lead to persistence of vesicular stomatitis virus mutants on fibroblast cells.

Acute infection of fibroblastic cell lines by the Indiana strain of vesicular stomatitis virus (VSV) usually induces dramatic cytopathic effects and shutoff of cellular gene expression. We have compared a series of independent mutants with differences in shutoff induction and found that M was mutated either in the N-terminus (M(51)R) or C-terminus (V(221)F and S(226)R). Furthermore, only double mutants (M mutation and a ts mutation related or not to M) were able to persist on fibroblast cell lines at 39 degrees C. A more detailed investigation of the infection was performed for the mutants T1026, TP3 and G31, differing in their host shutoff effects related to M protein. Viral activity in persistently infected mouse L-929 and monkey Vero cell lines was followed by viral proteins detection, RNA synthesis throughout infection and finally detection of infectious particles. All three mutants cause extensive CPE followed by emergence of persistently infected cells on Vero cells. The same thing is seen on L-929 cells except for T1026 which causes little CPE. Taken together, the results form a basis of further studies to clarify how various viral and cellular factors interact in the establishment of a persistent infection by VSV mutants.

Animals↗
PubMed2001

Tick-borne encephalitis virus NS1 glycoprotein during acute and persistent infection of cells.

Tick-borne encephalitis virus (TBEV) was propagated in porcine embryo kidney (PS) cells until 48 h whereas human kidney (RH) cells maintained the virus persistence during at least 2 months. One of possible reasons of flavivirus chronic infection might be abnormal NS1 gene expression. Immunoblotting with monoclonal antibodies (MAbs) revealed the similarity of the intracellular and secreted NS1 nonstructural glycoprotein size and linear antigenic determinants in both the infected cell lines. However, according to the competitive binding of MAbs with the TBEV NS1 extracellular glycoprotein, its contiguous epitopes differed for acute or persistent infection. To map the TBEV NS1 glycoprotein antigenic determinants its recombinant analogues were used. All the studied MAbs could bind with the full-length NS1 recombinant protein. Deletion of the TBEV NS1 gene internal region resulted in defective NS1d1 protein without the region between 269 and 333 a.a. Lack of NS1d1 binding with 20B4 MAb and diminished binding with 22H8 and 17C3 MAbs permitted to map their antigenic determinants within or nearby deleted region, respectively. Interaction of other MAbs with the NS1 and NS1d1 recombinant proteins did not differ, suggesting that their epitopes were located in the region of N-terminal 268 a.a. or C-terminal 19 a.a. of the TBEV NS1 protein. The second NS1d2 truncated protein contained the first N-terminal 33 a.a. of the TBEV NS1 protein and was able to bind with 29G9 MAb. Taken together the data stand for the differences in the N-terminal structure of the TBEV NS1 multimers secreted from the acute and persistent infected cells whereas the intracellular and secreted monomer processing was the same. The modified NS1 protein oligomers in the RH cellular line might slow virus replication and could result in the TBEV persistence.

Animals↗
PubMed1995

The persistent variant of influenza C virus carries one characteristic point mutation in RNA segment 1.

Influenza C/ Ann Arbor/1/50-pi(C/AA-pi) virus causes persistent infections in MDCK and Wi38 cells, but sets limited, wild-type like infections in other cells. Concluding that persistence itself it dependent on the host environment, we determined the nucleotide sequence of the C/AA-pi analogous gene to the basic polymerase 2 (PB2) of influenza A virus, which is known to be a determinant for the host range. C/AA-pi and the parental wild-type virus (C/AA-wt) have 16 nucleotides in common that are different to a previously published PB2 sequence (C/JJ/50). These variations, which are probably due to divergent passages histories, are scattered along the sequence and are partially found in another published isolate (C/Berlin/1/85). One single mutation, however, is unique to the persistent variant. Nucleotide 28 mutated from T to C which leads to a change of amino acid 3 from Leu to Phe. This substitution is stably associated with the persistent phenotype throughout multiple passages in different cells lines and eggs and cannot be found in any other influenza C viruses.

Base Sequence↗
PubMed1993

Hepatitis B virus occult infection in subjects with persistent isolated anti-HBc reactivity.

The aim of this study was to investigate the presence of hepatitis B virus occult infection in asymptomatic subjects with persistent anti-HBc reactivity but no other hepatitis B virus serological markers, including HBsAg, anti-HBs, IgM anti-HBc and HBV-DNA. For this purpose we used both polymerase chain reaction assays in sera and immunohistochemistry for HBsAg and HBcAg in liver biopsy specimens. Twenty-four cases were studied: 15 were drug abusers or homosexuals (eight with normal alanine aminotransferase levels) and nine were heterosexuals with raised alanine aminotransferase levels (> 45 U/l) but with no history of blood transfusion or ethanol intake (< 80 g daily). In all but five cases, liver biopsy was performed in subjects with persistent elevated alanine aminotransferase levels. In 10 out of 24 cases (41.66%) hepatitis B virus infection was demonstrated by polymerase chain reaction or immunohistochemistry, and when results from both procedures were available (n = 11) hepatitis B virus infection was detected in 63.63% of the subjects. The only clinical feature associated with HBV infection was the presence of persistent elevated alanine aminotransferase levels (p < 0.05). In conclusion, persistent isolated anti-HBc reactivity may be a relatively common serologic pattern for hepatitis B virus occult infection, at least in patients with chronic liver disease.

Base Sequence↗
PubMed1997

Persistence of hepatitis B virus DNA in serum and liver from patients with chronic hepatitis B after loss of HBsAg.

BACKGROUND/AIMS: The persistence of serum and liver hepatitis B virus (HBV) sequences in patients with chronic hepatitis B after loss of HBsAg has already been described. We have attempted to elucidate the significance of these HBV sequences after loss of HBsAg. METHODS: Fifteen patients were studied. We looked for serum and liver HBV DNA, using polymerase chain reaction (PCR) with different sets of primers and in situ hybridization. The sedimentation velocity of serum HBV DNA was measured on a gradient of sucrose in two patients. RESULTS: Serum HBV DNA was detected by PCR in four of the 14 patients tested at 0 months after loss of HBsAg, two patients remained HBV DNA positive until 12 months, and none was positive at 24 months. The sedimentation velocity of serum HBV DNA in sucrose was relatively similar to that of a chronic HBV carrier with active viral replication. Liver HBV DNA was demonstrated by PCR in all 15 patients and by in situ hybridization in six patients. CONCLUSIONS: Our results show that: 1) HBV DNA may persist in the serum in a minority of patients and may be associated with circulating viral particles; 2) HBV DNA persists in the liver in all patients and its extrachromosomal localization was shown by in situ hybridization technique in some cases. These results suggest the persistence of low-level HBV replication after loss of HBsAg.

Adult↗
PubMed2001

Transient translocation of conventional protein kinase C isoforms and persistent downregulation of atypical protein kinase Mzeta in long-term depression.

Persistent dephosphorylation has been implicated in the molecular mechanisms of long-term depression (LTD). Dephosphorylation may be due to either a persistent increase in phosphatase activity or a persistent decrease in kinase activity. We have previously found that protein kinase Mzeta (PKMzeta), the autonomously active form of the atypical PKCzeta isozyme that increases in long-term potentiation (LTP), decreases in LTD. This is consistent with the hypothesis that decreased levels of phosphorylation by PKC are important in LTD. Recently, however, increased phosphorylation by PKC has also been implicated in LTD. These contradictory results might be explained, in part, by the multiple isoforms of PKC, which may be independently regulated during the different phases of LTD. We now find that 45 s after low-frequency (3 Hz) stimulation that induces LTD in the CA1 region of hippocampal slices, conventional Ca(2+)/lipid-dependent PKC isoforms translocate from the cytosol to the membrane. This translocation was transient, lasting less than 15 min. In contrast, PKMzeta was persistently decreased through 2 h of LTD maintenance. Therefore, the activation and downregulation of distinct PKC isoforms may participate in the induction and maintenance mechanisms of LTD.

Animals↗
PubMed2001

Ecology of sprouting in woody plants: the persistence niche.

Many woody plants can resprout and many ecosystems are dominated by resprouters. They persist in situ through disturbance events such as fire, flooding or wind storms. However, the importance of 'persistence' in plant demography has been neglected in favour of 'recruitment'. Thus much research on plant regeneration, conservation and evolution has focused on the importance of safe sites, seed and seedling banks, dispersal and germination with the implied importance of de novo replacement rather than persistence. Recent research shows a growing appreciation for the role of sprouting as a form of persistence in a diversity of ecosystems and tradeoffs between the two regeneration modes.

Journal Article↗
PubMed2004

[Persistent hyperplastic primary vitreous and Aicardi syndrome].

INTRODUCTION: Aicardi syndrome is characterized by infantile spasms, agenesis of the corpus callosum and chorioretinal lacunae. This disorder affects mostly females, with early embryonic lethality in males. Numerous general and ocular disorders may be associated with this affection. We present here a case of persistent hyperplastic primary vitreous (PHPV) in association with Aicardi syndrome in a 30-year-old woman. CASE REPORT: The authors report a case of a 30-year-old woman with Aicardi syndrome associated with persistent hyperplastic primary vitreous. DISCUSSION: Aicardi syndrome is a polymalformative disease occurring at an early period of embryogenesis. It can affect many ocular structures. This syndrome is essentially described in female children, who rarely reach an adult age. The observation we report is particular because of the patient's age (30-years-old) and the association with a persistent hyperplastic primary vitreous, exceptional in this context. CONCLUSION: With a review of the literature, the Authors discuss the clinical neuroradiological and prognostic aspects of this polymalformative syndrome and different associated general and ocular abnormalities, emphasizing particularly those of persistent hyperplastic primary vitreous in this affection.

Adult↗
PubMedDate not supplied

PCR-based detection of bacterial DNA after antimicrobial treatment is indicative of persistent, viable bacteria in the chinchilla model of otitis media.

PURPOSE: Bacterial deoxyribonucleic acid (DNA) has been previously detected by polymerase chain reactions (PCR) in a significant percentage of culturally-sterile pediatric middle-ear effusions. The current study was designed to determine whether this represents the existence of viable bacteria or the persistence of residual DNA in the middle-ear cleft. MATERIALS AND METHODS: The middle-ear cavities of two sets of chinchillas were inoculated with either: 1) 100 colony-forming units (CFU) of live Haemophilus influenzae, 2.2 x 10(6) CFU of pasteurized Moraxella catarrhalis, and 1000 ng of DNA (>10(8) genomic equivalents) from Streptococcus pneumoniae; or 2) 100 CFU of live S pneumoniae, 2.2 x 10(6) CFU of pasteurized M catarrhalis and 1000 ng of purified DNA from H influenzae. Animals were treated with ampicillin for 5 days beginning on day 3. A single-point longitudinal study design was used for sampling to eliminate the possibility of contamination. RESULTS: No DNA was detectable from the heat-killed bacteria or the purified DNA after day 3. However, DNA from the live bacteria persisted through day 21, even though all specimens were culture-negative following the initiation of antimicrobial therapy. CONCLUSION: These findings indicate that purified DNA and DNA from intact but nonviable bacteria do not persist in the middle-ear cleft in the presence of an effusion, even following high copy inoculation. In contrast, antibiotic-treated bacteria persist in some viable state for weeks as evidenced by the differential ability of the PCR-based assay systems to detect the live bacteria, but not detect the heat-killed organisms.

Ampicillin↗
PubMed1998

Development and evaluation of a new alcohol-based surgical hand scrub formulation with persistent antimicrobial characteristics and brushless application.

BACKGROUND: Since the introduction in the 1970s of surgical hand scrub formulations that contain 4% chlorhexidine gluconate (CHG), new surgical scrub formulations that have improved efficacy, persistence, or significantly improved use characteristics have not been forthcoming. In addition, the manufacturer's labeling for popular hand scrub products generally requires scrub times in excess of 6 minutes, whereas current practical needs call for products with substantially shorter scrub times. A new alcohol-based surgical scrub formulation, which has ingredients that provide emollient, surfactant, and antimicrobial persistence characteristics to complement the rapid and broad-spectrum antiseptic qualities of alcohol, has been developed in an effort to address these current practical needs. METHODS: The relative efficacy of a new alcohol-based surgical scrub formulation that contains ingredients that provide surfactant and antimicrobial persistence characteristics was compared with that of commercial 4% CHG and 7.5% povidone iodine (PVPI) formulations with use of human subjects. Hand antimicrobial count sampling was performed by using standardized "glove juice" methodology. RESULTS: The efficacy and persistence results of the new formulation showed statistically significant improvement over both CHG and PVPI at a substantially lessened scrub time (3 minutes). In addition, use of the new formulation without a scrub brush produced results statistically similar to 3-minute applications with either a brush or a sponge. CONCLUSIONS: The new alcohol-based formulation demonstrates promise as a new surgical hand scrub formulation with antimicrobial and use characteristics that are significantly improved over current CHG and PVPI formulations. These studies demonstrate the suitability of this formulation for use as a surgical hand scrub and for brushless application.

Administration, Topical↗
PubMed2000

ACE inhibition improves glomerular size selectivity in patients with idiopathic membranous nephropathy and persistent nephrotic syndrome.

Patients with idiopathic membranous nephropathy (IMN) and persistent nephrotic-range proteinuria are at risk for progression to end-stage renal failure. Whether angiotensin-converting enzyme (ACE) inhibitors are also renoprotective in these patients remains elusive. In 14 patients with IMN (patients) and persistent proteinuria (protein > 3 g/24 h for >6 months), we studied mean arterial pressure (MAP), urinary protein excretion, glomerular filtration rate (GFR), renal plasma flow (RPF), and albumin and neutral dextran fractional clearance after 2 months washout from previous antihypertensive treatment (basal), after 2 months of enalapril (2.5 to 20 mg/d) therapy (posttreatment), and 2 months after enalapril withdrawal (recovery). MAP, proteinuria, and GFR were also measured at the same time points in 6 patients with IMN and persistent overt proteinuria maintained on conventional treatment throughout the study period (controls). Basal MAP, proteinuria, and GFR were similar in the two study groups. However, in patients at the end of the treatment period, MAP (posttreatment, 99.6 +/- 11.2 versus basal, 103.3 +/- 12.1 mm Hg; P < 0.05), proteinuria (posttreatment protein, 5.0 +/- 2.9 versus basal, 7.1 +/- 4.9 g/24 h; P < 0.05), albumin fractional clearance (posttreatment median, 1.7 x 10(-3); range, 0.2 to 22.7 x 10(-3) versus basal median, 4.1 x 10(-3); range, 0.4 to 22. 1 x 10(-3); P < 0.05), and fractional clearance of largest neutral dextrans (radii from 62 to 66 A) were significantly less than basal values. At recovery, MAP significantly increased to 106.6 +/- 11.7 mm Hg (P < 0.001 versus enalapril), but all other parameters remained less than basal values. GFR and RPF were similar at each evaluation. Changes in proteinuria after treatment withdrawal positively correlated (r = 0.72; P < 0.01) with baseline GFR. Theoretical analysis of dextran-sieving data indicated that ACE inhibitor treatment significantly improved glomerular membrane size-selective dysfunction. This effect persisted more than 2 months after treatment withdrawal. No patient had symptomatic hypotension, acute renal function deterioration, or hyperkalemia during enalapril treatment. Thus, in patients with IMN and long-term nephrotic syndrome, ACE inhibitor treatment, but not conventional therapy, improves glomerular barrier size selectivity. The antiproteinuric effect of ACE inhibition is long lasting, especially in patients with more severe renal insufficiency. This is the premise of a long-term renoprotective effect that may limit the need for treatment with more toxic drugs.

Adult↗
PubMed2002

[Prognostic value of persistent ST-segment elevation after successful primary angioplasty].

INTRODUCTION AND OBJECTIVES: A variable percentage of patients with myocardial infarction treated with successful primary angioplasty and restoration of coronary flow show persistent ST-segment elevation, probably due to inadequate cellular reperfusion. We studied if persistent ST-segment elevation was a predictor of worse prognosis. PATIENTS AND METHODS: We comparatively studied the clinical and angiographic results of 116 acute myocardial infarction patients after successful primary angioplasty, which were classified into two groups depending on the persistence (> 50%) or reduction (</= 50%) of ST-segment elevation between the electrocardiograms recorded before and after coronary angioplasty. RESULTS: In 96 patients (Group I) the ST-segment elevation improved after angioplasty and in 20 patients (Group II) there was no improvement. Baseline characteristics were similar in both groups except for Killip class 4, which was more prevalent in group II (7.2 vs. 25%; p = 0.01). There were no differences in the characteristics or results of the procedure. There was more myocardial damage in group II (CK 3,149 1,636 vs. 2,185 2,010 U/l; p = 0.02), associated with a more impaired left ventricular ejection fraction in the late angiographic control (47 16 vs 55 16%; p = 0.05). At a one-year follow-up the mortality was 8.3% in group I and 30% in group II (p = 0.01). CONCLUSIONS: The persistence of ST-segment elevation after successful primary angioplasty identifies a group of patients that may suffer an increased risk of adverse events in spite of good epicardial flow.

Aged↗
PubMed2000

Modulatory roles of the adenosine triphosphate P2x-purinoceptor in generation of the persistent nociception induced by subcutaneous bee venom injection in the conscious rat.

To study the role of adenosine triphosphate (ATP) P2x-purinoceptor in the persistent nociceptive response induced by subcutaneous (s.c.) bee venom injection, we used a selective P2x receptor antagonist, pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), to evaluate whether spinal P2x receptor play a role in development of spontaneous persistent pain. Injection s.c. of bee venom into the plantar surface of one hindpaw in the conscious rat produces a monophasic, prolonged persistent nociception characterized by continuously flinching reflex of the injected paw for 1-2 h. Intrathecal (i.t.) pretreatment with PPADS at two lower doses of 5 and 10 microg resulted in suppression of the flinching reflex in a dose dependent manner with the inhibitory rate 37 and 44%, respectively, when compared with the control group; whereas i.t. PPADS at a higher dose of 30 microg failed to produce any inhibitory effect. This result suggests that activation of P2x-purinoceptor in the spinal cord contributes to the induction of bee venom-induced prolonged persistent pain. However, the antinociceptive effect of ATP P2x-purinoceptor antagonist such as PPADS on clinical pathological pain seems to be limited due to its lack of effectiveness at higher dose.

Adenosine Triphosphate↗
PubMed2001

Molecular approaches to elucidating innate and acquired immune responses to Babesia bovis, a protozoan parasite that causes persistent infection.

For many vector-transmitted protozoal parasites, immunological control of acute infection leads to a state of persistent infection during which parasitemias may cycle unnoticed in infected but otherwise clinically healthy animals. Achieving persistent infection is a strategy that favors parasitism, since both host and, therefore, parasite survive, and endemically infected animal populations provide a reservoir of parasites continually available for subsequent transmission. Examples of the major economically important protozoan pathogens that cause persistent infection in mammals include the related Theileria and Babesia parasites as well as Trypanosoma species. Control of acute infection and maintenance of clinical immunity against subsequent infection are determined by the interplay of innate and acquired immune responses. This review will focus on approaches taken to gain an understanding of the molecular basis for innate and acquired immunity against the hemoprotozoan parasite of cattle, Babesia bovis. Knowledge of mechanisms used by the parasite to survive within infected cattle from acute to persistent infection combined with definition of the correlates of protective immunity in cattle should be applicable to designing effective vaccines.

Animals↗
PubMed2000

Persistence of cellulitis-associated Escherichia coli DNA fingerprints in successive broiler chicken flocks.

Avian cellulitis in broiler chickens is primarily caused by Escherichia coli. Previous research found that the E. coli isolates of cellulitis origin were unique to each ranch, suggesting that these E. coli were endemic within the ranch environment. To test the hypothesis that the E. coli associated with cellulitis are endemic in the litter of the broiler house, we designed a study to determine whether E. coli DNA fingerprints associated with cellulitis persist over successive flocks that are grown in the same house. In addition, we assessed the impact of different cleaning and disinfection strategies on this persistence. Two broiler houses were followed on each of five farms over 3-4 flocks. A total of 353 E. coli isolates from cellulitis lesions were analyzed in this study, and 314 of these isolates (89%) were DNA fingerprinted by PFGE. In each ranch, there were several DNA fingerprint patterns that were present over successive flocks, regardless of the cleaning and disinfection strategy utilized. Isolates persisted as long as 191 days, implying that these E. coli are capable of persisting in the broiler house environment for long periods of time. In addition, these E. coli isolates were associated with cellulitis lesions in successive flocks. Thus, the isolates of E. coli that are associated with cellulitis in broiler chickens appear to be endemic in the litter environment of the broiler house.

Animal Husbandry↗
PubMed2002

Persistence of Escherichia coli O157:H7 in experimentally infected swine.

These experiments determined the ability of Escherichia coli O157:H7 to colonize and persist in pigs simultaneously inoculated with other pathogenic E. coli strains. Three-months-old pigs were inoculated with a mixture of five E. coli strains. The mixture included two Shiga toxigenic E. coli (STEC) O157:H7 strains, two enterotoxigenic E. coli (ETEC) strains and one enteropathogenic E. coli (EPEC) strain. A high dose mixture with all five strains at 10(10)CFU/animal (CFU: colony forming units) and a low dose mixture with the STEC strains at 10(7)CFU and the EPEC and ETEC strains remaining at 10(10)CFU were used. The STEC strains persisted in the alimentary tracts of some pigs at 2 months post-inoculation, following inoculation with both the high and low dose mixtures. When all strains were given at 10(10)CFU (high dose) the STEC strains persisted in greater numbers and in more pigs than did the other E. coli strains. The results demonstrated that persistent colonization (> or =2 months) by E. coli O157:H7 can occur in pigs. These findings were similar to those reported from sheep inoculated with the same mixture of E. coli strains. The results are consistent with reports suggesting that pigs have the potential to be reservoir hosts for STEC O157:H7.

Animals↗
PubMed2003

Intracellular survival of Brucella: defining the link with persistence.

Brucellosis is caused by a facultative intracellular pathogen that invades both professional and non-professional phagocytic cells. Resistance to killing in professional phagocytic cells controls survival and chronic infection. Resistance of the organism to killing appears to derive from altered intracellular trafficking of Brucella containing vacuoles to the endoplasmic reticulum via the autophagic pathway. Acute infection is observed in pregnant ruminants in which invasion of the chorionic trophoblasts results in abortion. Following abortion persistence of the organism is observed in the mammary gland and lymph nodes of ruminants. The risk of multiple abortions and subsequent shedding of the organism in the milk has resulted in the culling of infected animals. Persistence of the organism in the reticuloendothelial system is a primary symptom in human infection and may persist over several decades. We have employed the mouse model of brucellosis to characterize genes responsible for persistent infection in an effort to identify potential drug targets for elimination of infection or to attenuate potential vaccine candidates. The results suggest that Brucella utilizes a battery of metabolic functions to sustain itself in intracellular environments in conjunction with altering the intracellular course of infection.

Abortion, Veterinary↗
PubMed1998

Study of the persistence of Aujeszky's disease (pseudorabies) virus in peripheral blood mononuclear cells and tissues of experimentally infected pigs.

The presence of Aujeszky's disease virus (ADV) in peripheral blood mononuclear cells (PBMC) and tissues of experimentally infected pigs was studied. Vaccinated and unvaccinated pigs were inoculated with different doses of Aujeszky's disease NIA-3 strain. Pigs were periodically bled and PBMC were used for virus isolation and PCR detection of virus. Tissues were obtained at the time of death (8 weeks post-inoculation) and used for ADV genome detection by PCR. ADV genome was amplified from PBMC during the acute phase of infection and, in some experimental groups, up to 38 days post-inoculation (PI). The virus was sporadically detected by virus isolation performed from PBMC. In neural tissues, ADV was constantly amplified from the trigeminal ganglia and the olfactory bulb of persistently infected pigs (euthanized 8 weeks PI). In other tissues, the viral genome was rarely detected in lymph nodes and tonsils, and occasionally, in the bone marrow. Our results indicated that PBMC are not an appropriate source for detecting ADV persistence, since inconsistent results were obtained throughout the experiments. In neural tissues, the olfactory bulb turned out to be as important a target for ADV persistence as the trigeminal ganglia. Viral genome detection in the bone marrow indicated that this tissue may play a role in the establishment of a persistent infection.

Animals↗