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PubMed1990

AZT demonstrates anti-HIV-1 activity in persistently infected cell lines: implications for combination chemotherapy and immunotherapy.

A sensitive and quantitative focal immunoassay has been used to measure the effects of three different therapeutic agents on tissue culture cells infected with human immunodeficiency virus (HIV). The effects of the drugs were studied on both acutely and persistently infected CD4+ cell lines. The three agents, azidothymidine (AZT), interferon-alpha (IFN-alpha), and an anti-HIV envelope antibody coupled to ricin A chain, were tested alone and in combination. AZT was found to have its greatest effect during early stages of the infection, but also had an action on persistently infected T cell lines. The effect of AZT on persistently infected cells was seen within 24 h, increased with extended exposure to the drug, and persisted after its removal. IFN-alpha had variable effects on acutely infected cells but suppressed chronic infection. Combinations of the therapeutic agents were studied. Using a model that allowed for treatment during both acute and persistent stages of infection, the most effective combination in suppressing HIV infection was the continual use of both AZT and IFN-alpha at the highest tolerable doses. Knowledge of the efficacy of AZT on persistently infected cells will allow for the most effective design of clinical protocols.

Cell Line↗
PubMed1994

Persistence of type-specific human papillomavirus infection among cytologically normal women.

Determinants of genital human papillomavirus (HPV) persistence in 393 women initially cytologically normal were investigated by testing them for HPV DNA twice over a median interval of 14.9 months. At each visit, interview information was obtained and a cervicovaginal lavage sample was collected for polymerase chain reaction-based HPV testing. Twenty-six percent of the women were HPV-positive at the first sampling. Data on HPV type was available for 86 HPV-positive women (84%); 35 of these women (41%) had persistent type-specific HPV detection. Persistence decreased with time between samplings. Women aged > or = 30 years had a higher percentage of persistence (65%) than those < or = 24 years (32%, P = .02). The percentage of persistence was higher among women infected with HPV types known to be cancer-associated (45%) than among those infected with other types (24%, P = .11). These findings were independent of each other and of timing between samplings. Although based on a prevalent cohort, these results are concordant with previous suggestions that HPV infection is usually transient and that cervical cancer may arise from within the subset of women with persistent HPV infection.

Adolescent↗
PubMed1991

Epidemiologic, clinical, and laboratory characteristics of acute vs. persistent diarrhea in periurban Lima, Peru.

Longitudinal studies of acute and persistent diarrhea in 677 children less than 3 years old were conducted for 27 months in an underprivileged, periurban community near Lima, Peru. Incidence rates and accurate durations of diarrhea were obtained by twice-weekly community-based surveillance and clinical and laboratory features of diarrheal episodes were documented. Study children had an overall incidence of diarrhea of 8.1 episodes per child-year and an incidence of persistent (greater than 14 days) diarrhea of 0.25 episodes per child-year. Episodes of longer duration were associated with young age (0-5 months) and more severe illness (greater than or equal to 6 diarrheal stools per day) in the first week. None of the laboratory tests performed in the first week of illness (fecal leukocytes, blood, reducing substances, pH, or fat) proved of value to identify episodes that would become persistent. Although steatorrhea was commonly present in the acute phase of the illness, it became less frequent by the third or subsequent week of illness in the persistent diarrheas. These results suggest that there are no clinical or laboratory features of acute diarrhea that are strongly predictive of the subset of diarrheas that persist. Thus, it is important that all diarrheal episodes should have appropriate fluid and dietary management and follow-up to detect the persistent diarrheas that may need special intervention.

Acute Disease↗
PubMed1976

Persistent herpes simplex virus infections established in two Burkitt lymphoma derived cell lines.

Examination of P3HR-I cells (Epstein-Barr virus [EBV] producer) persistently infected with the MAL strain of herpes simplex virus type I (HSV-I) suggested that only a few cells were actively producing a virus indistinguishable from HSV-I (MAL) despite the presence of immunofluorescent HSV-I antigens associated with the majority of cells. EBV-specific immunofluorescence was not altered in HSV-I persistently infected P3HR-I cells. HSV-I persistently infected cells, labelled for 72 h with 14C-thymidine, incorporated approx. 8% of the label into cell associated HSV-I DNA as resolved by caesium chloride gradients. Values greater than 8% of the total were suggested by hybridization of gradient fractions with 3H-HSV-I DNA. To determine whether the establishment of HSV persistent infections in Burkitt lymphoma derived cells was a general phenomenon, six strains of HSV-I (MAL, KOS, Patton, Syn R, BF and SYN V) and two strains of type 2 (333 and MS) were used to infect the P3HR-I and Raji (EBV non-producer) cell lines derived from Burkitt lymphomas. In P3HR-I cells, persistent infections were established with all strains of HSV-I but not with HSV-2. In Raji cells, persistent infections were established with all strains of HSV-I, except Syn V, and with both strains of HSV-2. No external support was required to maintain these infections.

Adsorption↗
PubMed1980

Persistent Theiler's murine encephalomyelitis virus infection in mice depends on plaque size.

Theiler's murine encephalomyelitis virus (TMEV) is an enteric pathogen of mice which causes acute and chronic neurological disorders in the natural host. When brain-derived stocks of TMEV isolates are adapted to cell culture they predominantly form either large or small plaques. In this study the type of central nervous system (CNS) infection (acute versus chronic) and the associated disease occurring in mice inoculated intracerebrally with large and small plaque strains of TMEV was investigated. Large and small plaque strains of TMEV were found to vary in virulence, type of neurological disease produced and ability to establish persistent CNS infection in mice. Two large plaque strains, GDVII and FA viruses, were highly virulent, produced acute encephalitis, but were cleared from the nervous systems of surviving animals. Therefore, it appears that these large plaque variants do not cause persistent CNS infection in mice. In contrast, five small plaque strains, DA, WW, TO4, Yale and BeAn8386 viruses, were relatively avirulent, usually produced no illness during the first month after inoculation, but readily established persistent CNS infection in mice. Persistently infected mice later developed demyelinating disease. Having identified strains of TMEV that differ regarding their ability to persist, we now hope to be able to exploit this difference in elucidating the basic mechanism(s) of TMEV persistence.

Animals↗
PubMed1981

Establishment of persistent infection in mouse cells by Sindbis virus and its temperature-sensitive mutants.

The ability of wild-type (wt) Sindbis virus and six temperature-sensitive (ts) mutants to establish persistent infection in mouse L cells and a line of mouse embryo (ME) cells was determined. The wt established persistent infection in both ME cells and L cells at 39 degrees C. At 30 degrees C the wt established persistent infection in L cells but not ME cells, which did not recover from the initial infection. For the ts mutants, both cell lines survived the initial infection at 39 degrees C (the restrictive temperature) but the virus was eventually eliminated. At 30 degrees C (the permissive temperature) in L cells all mutants established persistent infection. In ME cells at 30 degrees C, RNA- mutants (unable to synthesize virus-specified RNA at 39 degrees C) established persistent infection whereas the cells did not recover from infection with RNA+ mutants (able to synthesize virus-specified RNA at 39 degrees C). The wt virus was less cytopathic in L cells than in BHK or ME cells. Interferon was produced by both L and ME cells at 30 degrees C and 39 degrees C, but its activity could not be detected in either cell line at 30 degrees C. It is proposed that establishment of persistent infection is dependent on reduced cytopathogenicity in the early stage of infection, and that further evolution of the virus then occurs to a less cytopathic form. Elimination of the virus at 39 degrees C is probably due to the action of interferon.

Animals↗
PubMed1981

Persistent infection of Vero cells with Tacaribe virus.

Persistently infected cultures have been established from Vero cells surviving primary infection with Tacaribe virus (Vero-T). The growth rate and morphological characteristics of the persistently infected cells were indistinguishable from normal Vero cells. Virus release declined during the first 6 passages, a cyclical pattern was observed between passages 6 and 16, and subsequently no virus infectivity could be detected. Co-cultivation with normal RK-13 or Vero cells enhanced virus yield from virus-producing cultures of Vero-T cells (passage 15), but the addition of susceptible cells had no effect on non-producer Vero-T cultures (passage 19). Only a small proportion (less than 1%) of the persistently infected cells tested during the first 16 passages produced infectious virus. The virus released during the early stages of persistence was temperature-sensitive if grown at 40 degree C, more thermolabile at 50 degree C than parental virus, and unable to initiate a persistent infection in Vero cells. Vero-T cells consistently showed refractoriness to homotypic Tacaribe virus superinfection and a selective graded resistance to other arenavirus replication. The possible use of viral susceptibility of persistently infected cultures as marker of antigenic relationship among Tacaribe complex viruses if considered.

Animals↗
PubMed1988

Deleted viral RNAs and lymphocytic choriomeningitis virus persistence in vitro.

Lymphocytic choriomeningitis virus (LCMV) infection of most tissue culture cell lines results in a non-cytopathic persistent infection. Persistent infections in vitro share many characteristics with persistent LCMV infection of mice; both are associated with decreased titres of infectious virus, restricted accumulation of viral glycoproteins at the surface of infected cells and the generation of interfering particles. We have used gel electrophoresis and hybridization techniques to analyse LCMV gene expression during persistent infection of a number of tissue culture cell lines. Our study has demonstrated that, although deleted viral RNAs can be detected during persistent LCMV infection in vitro, there may not be an obligatory association between deleted RNAs and persistence. In addition, we have found that LCMV interfering activity can be produced in the apparent absence of deleted intracellular viral RNAs.

Animals↗
PubMed1988

Establishment and characterization of St Louis encephalitis virus persistent infections in Aedes and Culex mosquito cell lines.

Persistent infections with St Louis encephalitis (SLE) virus were established in three mosquito cell lines (Aedes albopictus, A. dorsalis and Culex tarsalis) and were maintained for over 2 years. All three persistently infected cell cultures shared two features: (i) no overt cytopathic effect and (ii) a relatively high proportion of cells infected (41 to 85%). The Aedes persistently infected cultures were resistant to superinfection with the homologous virus but not heterologous viruses. Two significant differences were observed between the Aedes and C. tarsalis persistently infected cell cultures: (i) viral titres in the A. albopictus and A. dorsalis cell cultures decreased slowly over time (the decrease was particularly marked in the A. albopictus cell cultures), whereas titres in the C. tarsalis cell cultures remained relatively constant and (ii) the addition of anti-SLE virus antibody led to decreased virus production in the C. tarsalis cell cultures (one of two cultures was cured of infection), whereas antibody had no effect on the persistently infected Aedes cell cultures. These results suggest that there may be significant differences in the regulation of viral replication and the maintenance of flavivirus persistent infections in mosquito cell lines of different origins.

Aedes↗
PubMed1995

Theiler's murine encephalomyelitis virus 3D RNA polymerase: its expression in the CNS and the specific immune response generated in persistently infected mice.

Intracerebral inoculation of the neurotropic murine picornavirus, Theiler's murine encephalomyelitis virus (TMEV), results either in an acute encephalitis (GDVII strain) or in the establishment of a persistent infection with the development of demyelinating lesions (BeAn strain). In this article, the expression of the viral RNA polymerase was studied in the central nervous system of both acutely and persistently infected mice and in infected cells in tissue culture. Similar numbers of acutely infected glial cells (80-85%) expressed both viral polymerase and structural proteins in vitro while a much smaller proportion of persistently infected glial cells (0.6-0.9%) expressed these proteins. Following infection of mice with GDVII, many cells in the brain were found to express polymerase. However, in the spinal cord of mice persistently infected with BeAn, very few cells were found to express the polymerase while many more cells showed the presence of viral structural proteins. This suggests that a restriction in viral replication, possibly at the level of polymerase expression, may be a feature of the persistent infection. However, enough polymerase was expressed to maintain a polymerase-specific antibody response in a number of infected animals as late as 21 months post-infection. Mechanisms that may be involved in the establishment and maintenance of TMEV persistence are discussed with reference to these findings.

Animals↗
PubMed1988

Persistent infection with herpes simplex virus type 1 in an Ia antigen-positive murine macrophage cell line.

The interaction of herpes simplex virus type 1 (HSV-1) with murine macrophage cell lines was examined. The cell lines appeared to be moderately permissive for HSV-1 replication, though the yield of the virus was limited compared with that in Vero cells. Furthermore, the murine macrophage cell line SL-1, bearing Ia antigen, was persistently infected with HSV-1 for over one year, and was designated SL-1/KOS. Persistent infection could not be established in an Ia antigen-negative macrophage cell line, SL-4. In the SL-1/KOS culture, there was a small number of infected cells as revealed by infectious center assay. Treatment with monoclonal antibody against HSV-1 cured the persistent infection. Therefore maintenance of the persistent infection is considered to be due to a carrier culture consisting of a minority of infected cells and a majority of uninfected cells. In the SL-1/KOS cultures a low level of interferon (IFN) was found. When a large amount of exogenous recombinant murine IFN-beta (10(5)-10(6) international units/ml) was added to the culture, virus production diminished to undetectable levels. These results suggest that IFN plays an important role in the maintenance of persistent infection. In long-term persistently infected cultures, syncytium formation appeared and the virus from such cultures had a different DNA structure from that of the virus originally used for infection as revealed by restriction endonuclease analysis.

Animals↗
PubMed1993

Transient and persistent expansions of large granular lymphocytes (LGL) and NK-associated (NKa) cells: the Yorkshire Leukaemia Group Study.

A survey of 870 different adult blood samples (primarily from patients with non-haematological disorders) found that 269 (31%) had increased proportions (> 25%) and/or absolute numbers (> 1.0 x 10(9)/l) of morphologically-defined large granular lymphocytes (LGL), and/or phenotypically-defined NK-associated (NKa) cells. Of these, 112 were re-analysed at least 6 months after initial presentation and were classified as 'persistent' (92/112) or 'transient' (20/112) according to whether or not the original abnormality was still present. Lymphocyte counts in most patients with persistent abnormalities were within normal limits (18/92) or slightly increased (68/92), with only six having a lymphocytosis exceeding 10.0 x 10(9)/l. With the exception of five persistent LGL expansions in which the granular lymphocytes did not express NKa determinants (designated LGL+NKa-), the remaining 87 cases could be phenotypically grouped according to their primary abnormality as CD8+NKa+ (n = 33), CD4+ NKa+ (n = 14), CD8dim+NKa+ (n = 7) or CD8-NKa+ (n = 33). TCR genotypic studies in 58 patients showed that the 16 patients with rearranged TCR components were restricted to the CD8+NKa+ group and that, in most of these, the CD8+ fraction showed abnormal relative CD16/CD56 expression. Persistent neutropenia (n = 15) also appeared to be associated with primary abnormalities of CD8+NKa+ cells (12/15), with 10 of these additionally showing rearranged TCR genes. In contrast, persistently increased CD8dim+NKa+ and CD8-NKa+ components did not appear to phenotypically differ from their corresponding 'counterparts' in normal bloods or in patients with transient LGL/NKa+ abnormalities. This survey has therefore established that persistent LGL/NKa+ abnormalities are considerably more common than suggested in published work, that a high proportion of patients with expanded CD8+NKa+ components, with quite diverse clinical histories, show evidence of clonal lymphoid populations, and that the clonal nature of such disorders appears to be associated with abnormal NKa phenotypic patterns.

Adult↗
PubMed1992

Epidemiological and clinical characteristics of acute and persistent diarrhoea in rural Bangladeshi children.

A community-based longitudinal study of acute and persistent diarrhoea in 705 children less than five years old was carried out for a year in a rural area of Bangladesh. Diarrhoea morbidity data were collected from each study child every fourth day by home visit. Clinical features of diarrhoeal episodes and diarrhoeal management information were documented. The overall diarrhoeal incidence rate in the study children was 4.6 episodes per child per year. The incidence of persistent diarrhoea was 34/100 child-years. Persistent diarrhoea was positively associated with young age and more severe illness, characterized by the presence of clinical dehydration or blood in the stool in the first week. Use of ORT in the first week was positively associated and use of an antibiotic was negatively associated with the occurrence of persistent diarrhoea. Reduced breast-feeding and consumption of cow's milk at some time during the episode were also positively associated with persistence. This would suggest that appropriate fluid and dietary management for all episodes should be the goal. Children with more severe initial illness characterized by the presence of blood in the stool or clinical dehydration should have more careful follow-up to identify persistent episodes and adverse nutritional effects. Breastfeeding should be continued during acute diarrhoea, but the role of ORT, antibiotics and cow's milk deserves further investigation.

Acute Disease↗
PubMed1992

Epidemiology of persistent diarrhea and etiologic agents in Mirzapur, Bangladesh.

To determine the epidemiology and etiologic agents of persistent diarrhea we carried out an intensive diarrhea surveillance on children less than six years old in rural Bangladesh. From March 1987 to February 1989 we examined 363 children through diarrhea recall interviews and analyzed stool samples of all diarrhea cases for potential pathogens. Results showed that children had an average of two episodes per year and the incidence rate of diarrheal episodes defined as acute (< 14 d) and persistent (> or = 14 d) varied similarly with age. The peak incidence (episodes/child/year) of acute diarrhea (2.8) and persistent diarrhea (0.8) occurred in the 6-11 months age group. The data showed that an episode tended to be prolonged if the stool was loose/mucoid or bloody at onset. Aggregative adherent Escherichia coli was found significantly more often at onset in persistent than in acute episodes, whereas Shigella, Aeromonas, Giardia and toxigenic E. coli were isolated with less frequency in persistent than acute episodes. This suggests that other factors might be more important in the development of persistent diarrhea than specific pathogens.

Animals↗
PubMed1992

Persistent diarrhea in northeast Brazil: etiologies and interactions with malnutrition.

With the improved control of acute diarrheal illness mortality with oral rehydration therapy, persistent diarrhea is now emerging as a major cause of childhood mortality in tropical developing areas like the impoverished populations in Brazil's Northeast. "Graveyard surveillance" in the rural community of Guaiuba in northeastern Brazil revealed fully half of the 70% diarrhea mortality was due to persistent diarrheal illnesses. Furthermore, 11% of 14 or more diarrheal illnesses per child per year in an urban slum in Fortaleza persisted beyond 14 days, a definition that clearly identified the high risk children for heavy diarrhea burdens. Not only did heavy diarrhea burdens ablate the key "catch-up" growth seen in severely malnourished children and in children following previous diarrheal illnesses, but malnutrition significantly predisposed children to a greater incidence and duration of diarrhea as well as a greater incidence of persistent diarrhea. Etiologic studies of 37 children presenting with persistent diarrhea to Hospital das Clinicas in Fortaleza revealed that Cryptosporidium (in 13%) and enteroadherent E. coli (36% with aggregative, 29% with diffuse and 13% with localized adherence to HEp-2 cells) were the predominant potential pathogens found in the stool or upper small bowel. These findings suggest that persistent diarrhea is emerging as an important health problem in Brazil's Northeast, that it identifies a high risk child for heavy diarrhea burdens, that important interactions occur with malnutrition and that Cryptosporidium and enteroadherent E. coli warrant further study as potential etiologies of this major cause of morbidity and mortality.

Animals↗
PubMed1992

A persistent sodium current in rat ventricular myocytes.

1. The tight seal, whole-cell, voltage-clamp technique was used to record currents from single ventricular myocytes acutely dissociated from adult rat hearts. Subtraction of currents recorded in the presence and absence of tetrodotoxin (TTX, 50 microM) revealed a small, persistent, inward current following a much larger, transient, inward current. 2. Both currents were sodium currents because they reversed close to the sodium equilibrium potential and were depressed when choline was substituted for extracellular sodium. 3. The persistent sodium current could be recorded when the transient current had been inactivated with conditioning depolarization. Only slight inactivation of the persistent current occurred during depolarizing pulses lasting up to 900 ms. 4. A lower concentration of TTX (0.1 microM) blocked the persistent sodium current while having little effect on the transient sodium current. 5. The persistent sodium current was activated at more negative potentials than the transient sodium current. It cannot have been a window current because it was recorded at positive potentials when the transient current was completely inactivated. 6. Because the persistent and transient sodium currents had a different voltage dependence and sensitivity to TTX, it was concluded that different channels are responsible for the two currents.

Animals↗
PubMed1971

Persistent cultural systems.

I have indicated here some features of a kind of entity which I have called a cultural identity system, and I have focused on a variety of this general type-the persistent system. In general terms it is best described as a system of beliefs and sentiments concerning historical events. I suggest using the term "a people" for the human beings who, at any given time, hold beliefs of this kind. These are phenomena with which we have been long familiar, but they have not been systematically studied by any but a few investigators. I have emphasized that a persistent system is a cumulative cultural phenomenon, an open-ended system that defines a course of action for the people believing in it. Such peoples are able to maintain continuity in their experience and their conception of themselves in a wide variety of sociocultural environments. I hold that certain kinds of identifiable conditions give rise to this type of cultural system. These may best be summarized as an oppositional process involving the interactions of individuals in the environment of a state or a similar large-scale organization. The oppositional process frequently produces intense collective consciousness and a high degree of internal solidarity. This is accompanied by a motivation for individuals to continue the kind of experience that is "stored" in the identity system in symbolic form. The persistent identity system is more stable as a cultural structure than are large-scale political organizations. When large-scale states disintegrate, they often appear to decompose into cultural systems of the persistent type. Large-scale organizations also give rise to the kind of environment that can result in the formation of new persistent systems. It is possible that, while being formed, states depend for their impetus on the accumulated energy of persistent peoples. A proposition for consideration is that states tend to dissipate the energy of peoples after transforming that energy into state-level integrations, and then regularly break down in the absence of mechanisms for maintaining human motivations in the large-scale organizations that they generate.

Anthropology, Cultural↗
PubMed1975

Distribution and persistence of Staphylococcus and Micrococcus species and other aerobic bacteria on human skin.

The districution of Staphylococcus and Micrococcus species and associated coryneform bacteria, Acinetobacter, Klebsiella, Enterobacter, Bacillus, and Streptomyces on skin was determined during October 1971 from samples collected on persons living in North Carolina and New Jersey. Persistence of these organisms on skin was estimated in temporal studies conducted during the period from June 1971 to June 1972 on persons living in North Carolina. Staphylococci and coryneforms were the most predominant and persistent bacteria isolated from the nares and axillae. Staphylococci, coryneforms, micrococci, and Bacillus were the most predominant and persistent bacteria isolated from the head, legs, and arms. Acinetobacters were most frequently isolated during the warmer months of the years. Staphylococcus aureus and S. epidermidis were the most predominant and persistent staphylococci isolated from the nares, whereas S. epidermidis and S. hominis were the most predominant and persistent staphylocicci isolated from the axillae, head, legs, and arms. S. capitis was often isolated from the head and arms and S. haemolyticus was often isolated from the head, legs, and arms. S. simulans, S. xylosus, S. cohnii, S. saprophyticus, S. warneri, and an unclassified coagulase-positive species were only occasionally isolated from skin. Micrococcus luteus was the most predominant and persistent Micrococcus isolated from skin and preferred regions of the head, legs, and arms. M. varians was the second most frequent Micrococcus isolated. M. lylae, M. sedentarius, M. roseus, M. kristinae, and M. nishinomiyaensis were only occasionally isolated from skin. M. lylae was most frequently isolated during the colder months of the years.

Acinetobacter↗