Studies on the decline of bovine virus diarrhoea virus (BVDV) maternal antibodies and detectability of BVDV in persistently infected calves.
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Animals↗
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[Recurrent canaliculitis and dacryocystitis as a sequela of persistent infection with Chlamydia trachomatis].
We report on 4 patients aged 39-62 years with follicular conjunctivitis, canaliculitis, canalicular obstruction, dacryocystitis and nasolacrimal duct obstruction caused by chronic oculogenital infection with Chlamydia trachomatis. Microbiological diagnosis was accomplished by means of the McCoy cell culture technique as a highly specific tool for detection of the chlamydial infection. In addition, serological tests (IgA-IPA and IgG-IPA techniques) were performed. Bacteriological examination of conjunctival smears showed coinfection in 3 patients (Proteus mirabilis in 1, Staphylococcus aureus coagulase-positive in 3). Despite successful operation techniques, the obstructive inflammation caused by oculogenital chlamydial infection could only be cured by systemic treatment with specific antibiotics, such as doxycycline or erythromycin. All cases of chronic follicular conjunctivitis with lacrimal inflammation that are resistant to topical antibiotics should suggest the possibility of infection with Chlamydia trachomatis.
Adult↗
[Study of the virus isolated from the brains of Syrian hamsters with persistent infection induced by an attenuated strain of the virus of the tick-borne encephalitis complex].
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Animals↗
A genetic approach to study the pathogenesis of Theiler's virus persistent infection.
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Animals↗
Accelerated inflammatory bowel disease of TCR-alpha-deficient mice persistently infected with Cryptosporidium parvum.
TCR-alpha-deficient mice spontaneously develop inflammatory bowel disease (IBD) at 8-9 mo old. This study characterizes an accelerated form of IBD induced by Cryptosporidium parvum infection. Cryptosporidium parvum-infected TCR-alpha-deficient mice developed IBD as early as 4 wk old when challenged at 1 wk old. The lesions of this accelerated IBD resembled the lesions of spontaneous IBD in TCR-alpha-deficient mice and consisted of a mononuclear cell infiltrate within the intestinal lamina propria and an increased proliferation of enterocytes. The mononuclear cells within the lamina propria consisted of B cells and gamma delta T cells. The distal ileum, cecum, and colon were grossly thickened due to a hyperplastic mucosa and edematous submucosa. The mechanism by which C. parvum infection accelerates development of IBD is presently unclear.
Animals↗
Hepatitis C virus genotypes in patients with persistent infection--a preliminary report.
Hepatitis C virus (HCV) has nucleotide sequence diversity distributed throughout the viral genome, with variants showing even less than 70% homology. There is some evidence that sequence variation of HCV genotypes partly determines the course of infection and response to treatment with interferon. We studied the sera of 29 Israeli HCV patients, all suffering from chronic liver disease, and 34 patients with renal failure necessitating hemodialysis. HCV genotypes were detected using a reverse hybridization assay (LiPA), after reverse transcription polymerase chain reaction, using primers spanning the 5' UTR of the HCV genome. In this preliminary report the predominant HCV type detected was type 1, found in 65% of the chronic hepatitis patients and in 88% of the hemodialysis patients. Subtype 1b was the most prevalent and was detected in >40% of the chronic hepatitis patients and in >70%of the dialysis patients. Other types detected were 2a and 3, and in only two patients was type 4 found. More than 50% of patients with type 1 (1a or 1b) among patients with chronic hepatitis had received blood transfusion in the past, but only 16.6% of patients bearing subtype 2a HCV had such a history. Our preliminary evaluation revealed that patients bearing subtype 1b seemed to have a better response to interferon treatment, as compared with patients infected with subtypes 1a, 2a, who displayed a low response rate.
Adult↗
Evidence for two small viruses persistently infecting established cell lines of Phthorimaea operculella, deriving from embryos of the potato tuber moth.
Two small viruses were isolated from established cell lines of P. operculella deriving from embryos. The first one probably related to the Nodaviridae family, is a 30 nm in diameter icosahedral virus, with a bisegmented RNA genome and a single polypeptide of 39 kilodaltons. The second one related to the Parvoviridae family, is a 25 nm in diameter icosahedral virus with a DNA genome and a capsid constituted of 4 polypeptides of respectively, 90,000; 64,000; 56,000 and 43,500 daltons. The two viruses probably chronically infect the cell lines and may be consider latent viruses.
Animals↗
Prevalence of antibodies to human parvovirus B19 nonstructural protein in persons with various clinical outcomes following B19 infection.
Persistent infections with human parvovirus B19 (B19) associated with debilitating chronic disease have been described, although evidence linking B19 to these more unusual clinical outcomes has been inconclusive. Recent reports have suggested that the development of antibodies to the B19 nonstructural protein (NS1) following B19 infection might be linked to development of severe arthropathy and chronic infection. To confirm these findings, the C-terminal region of the NS1 protein was expressed for use in Western blot assays for detection of anti-NS1 IgG antibodies in human serum. Among 91 persons tested, 0 of 20 not previously infected with B19, 9(36%) of 25 with past B19 infection, and 5 (12.5%) of 40 with recent B19 infection, had detectable anti-NS1 antibodies. Of 6 persons with chronic B19 infection, 2 had detectable antibodies to NS1. The presence of anti-NS1 antibodies did not appear to correlate with unusual clinical outcomes or chronic B19 infection.
Animals↗
[Immunohistology as a reliable and efficient method for the diagnosis of BVDV infections].
Persistent infection with the Bovine Viral Diarrhea/ Mucosal Disease Virus (BVDV) can be detected using immunohistological methods. The experiments show that the LSAB (Labeled Streptavidin Biotin) peroxidase method is suitable to detect the BVDV in cryostat sections of unfixed tissue. For the diagnostic work up in living animals, skin biopsies give reliable results. In dead animals, organs such as thyroid gland, skin, mucosa of the mouth, esophagus and abomasum are well suitable for immunohistological BVDV detection.
Animals↗
Successful bone marrow transplantation for severe aplastic anemia in a patient with persistent human parvovirus B19 infection.
Persistent infection with human parvovirus B19 (B19) is primarily associated with chronic bone marrow failure in immunocompromised patients, but occasionally this organism may also affect immunocompetent hosts. B19 is also suggested as a causative agent of organ failure during bone marrow transplantation (BMT). We herein report the case of a 9-year-old girl with no previous history of immunodeficiency who developed severe aplastic anemia concurrent with B19 persistent infection. Both immunoglobulin (Ig)M antibody to B19 and B19 DNA identified by real-time polymerase chain reaction were found in the patient's serum at time of diagnosis of aplastic anemia. No giant proerythroblasts were found in her bone marrow at diagnosis. Although intravenous administration of Ig (IVIg) reduced serum B19 DNA, the aplastic status of her bone marrow did not improve. Both aplastic anemia and persistent B19 viremia were successfully treated by BMT from an HLA-identical sibling donor. Serum B19 DNA increased temporarily after BMT; however, neither organ nor marrow failure was observed. B19 DNA disappeared from the serum 2 months after BMT, suggesting that a normal immune response was restored by BMT and terminated the B19 viremia. During BMT, use of high-titer IVIg for B19 might prevent B19-associated organ failure.
Anemia, Aplastic↗
Production of extracellular virulence factors by Pseudomonas aeruginosa isolates obtained from tracheal, urinary tract, and wound infections.
This study was conducted to determine the effect of the local environment within the host on the ability of P. aeruginosa to produce different extracellular virulence factors (elastase, phospholipase C, toxin A, and exoenzyme S). A total of 105 P. aeruginosa isolates was obtained from patients with tracheal, urinary tract, and wound infections. Quantitative analysis of the virulence factors was done by growing the isolates in vitro in different defined media. Single colonies of each isolate were inoculated from the primary isolation plates into the defined medium. All four virulence factors were produced by most isolates. However, depending on the location of their isolation, the isolates varied in the level of virulence factors they produced. High levels of elastase and phospholipase C were produced by most isolates obtained from trachea, urinary tract, and wounds. A significantly higher level of toxin A was produced by wound isolates, while a significantly higher level of exoenzyme S was produced by wound and urinary tract isolates. Some P. aeruginosa strains were frequently isolated from the same site of infection (persistent infection isolates). Comparative analysis of virulence factors produced by these isolates showed that, regardless of the isolation site, subsequent isolates produced higher levels of exoenzyme S. These results suggest that: (1) elastase, phospholipase C, toxin A, and exoenzyme S are produced by P. aeruginosa isolates from different sites of infection; (2) the production of higher levels of elastase and phospholipase C is important in all types of infections, while the production of toxin A and exoenzyme S is important in wound infection; (3) persistent infection with P.aeruginosa may enhance exoenzyme S production.
ADP Ribose Transferases↗
Genetic variation during persistent reovirus infection: isolation of cold-sensitive and temperature-sensitive mutants from persistently infected L cells.
We have examined the evolution of reovirus in two independently established persistently infected (p.i.) cell lines. We found that reovirus undergoes extensive mutation during persistent infection in L cells. However, there was no consistent pattern of virus evolution; in one p.i. cell line temperature-sensitive (ts) mutants were selected, whereas cold-sensitive (cs) mutants were isolated from the second p.i. culture. Neither the cs nor the ts mutants isolated from the carrier cultures expressed their defect at 37 degrees, the temperature at which the p.i. cells were maintained, indicating that the cs and ts phenotypes were nonselected markers. These results emphasize the point that emergence of the ts or cs mutants during persistent infection only signifies that the virus has changed; it does not necessarily imply that the particular mutant is essential for the maintenance of the persistent infection. Given the high mutation rate of viruses, and the wide spectrum of viral mutants present in carrier cultures, it is essential to distinguish the relevant changes from those which may simply represent an epiphenomenon. In the accompanying paper (R. S. Kauffman, R. Ahmed, and B. N. Fields Virology, 130, 79-87, 1983), we show that by using a genetic approach, it is possible to identify the viral gene(s) which are critical for the maintenance of persistent reovirus infection.
Animals↗
Chronic ethanol effects on cellular immune responses to hepatitis B virus envelope protein: an immunologic mechanism for induction of persistent viral infection in alcoholics.
Hepatitis B virus (HBV) is common in alcoholics and may result in chronic infection. Persistence of HBV infection could be partially caused by the effects of ethanol on the cellular and humoral immune response to viral structural proteins. The DNA-based immunization approach was used to experimentally assess the effects of chronic ethanol feeding on immune responses directed against the middle envelope protein (MHBs) of HBV. Mice were fed an ethanol or isocaloric, pair-fed control liquid diet for 8 weeks, followed by immunization with a plasmid construct containing the pre-S2/S gene that encodes for MHBs. Chronic ethanol consumption marginally reduced the levels of the antibody to hepatitis B surface proteins (anti-HBs) generated by the DNA-based immunization approach. Initially, cytotoxic lymphocyte (CTL) activity was higher in ethanol-fed mice but progressively declined following the second and third immunizations as compared with control mice. In addition, CTL and CD4+ T helper (TH) cells responded poorly to increasing concentrations of envelope protein and peptides in vitro with respect to generation of CTL activity and proliferative responses. Finally, proliferating CD4+ T cells derived from ethanol-fed animals had substantial changes in the levels of cytokines secreted into the culture supernatants as compared with control mice. These studies show that chronic ethanol consumption substantially alters the cellular immune responses to a human viral structural protein, and that these effects may contribute to the persistence of viral infection.
Alcoholism↗
Vaccines against persistent DNA virus infections.
Persistent viruses present some particular problems for vaccine design. As for acute non-persistent viruses, the prime goal of a vaccine should be to prevent primary infection. Vaccines might also be used to modify the course of established persistent virus infections - so-called postinfective immunisation. This chapter deals with selected persistent DNA viruses, in particular the human herpes viruses.
Chickenpox↗
Understanding the phenomenon of persistence in mycobacterial infections.
Persistence of live organisms despite chemotherapy for long periods is a significant problem in both leprosy and tuberculosis. The consequence of this persistence is varying rates of relapses which undermine the success of treatment. The mechanisms of the dormancy are ill-understood, and as explanation a switch over to alternate modes of metabolism such as glyoxylate bypass and other shunts has been suggested. This presentation reviews the information available on this aspect. In-depth studies by designing and investigating model system(s) using molecular genetic approaches may help in gaining better understanding of the mechanisms of dormancy and persistence in mycobacterial infections and devising appropriate strategies and tools for the better management of these complications.
Animals↗
Genetic variation during persistent reovirus infection: presence of extragenically suppressed temperature-sensitive lesions in wild-type virus isolated from persistently infected L cells.
Persistent reovirus infection of L cells was established with a serially passaged stock of temperature-sensitive (ts) mutant C(447) containing greater than 90% defective interfering particles. Within a month after establishment of the carrier culture, the ts mutant was replaced by virus that expressed the wild-type (ts(+)) temperature phenotype (R. Ahmed and A. F. Graham, J. Virol. 23:250-262, 1977). To determine whether the ts(+) phenotype of the virus was due to intragenic reversion or to the presence of an extragenic mutation suppressing the original ts defect, several clones were backcrossed to wild-type reovirus, and the progeny of each cross were screened for temperature sensitivity. The results indicated that the original tsC lesion had reverted. However, in two of the seven clones examined, new ts lesions were found. These new ts lesions appeared phenotypically as ts(+) due to the presence of extragenic suppressor mutations. Temperature-sensitive mutants representing three different groups were rescued from one suppressed clone, indicating that this ts(+) clone contained multiple ts lesions. Among the ts mutants rescued were the initial isolates of a new recombination group which we have designated H. Some of the ts mutants rescued from the suppressed clones are capable of interfering with the growth of wild-type reovirus and may play a role in maintaining the carrier state. The results of this study show that persistently infected L cells contain a genetically heterogeneous population of reovirus even though all virus clones express the ts(+) phenotype. It is thus critical to distinguish between genotype and phenotype when analyzing viruses that emerge during persistent infection.
Animals↗
T cells and viral persistence: lessons from diverse infections.
Persistent virus infections create specific problems for their hosts. Although the dynamics of immune responses after acute infection are well studied and very consistent, especially in mouse models, the patterns of responses noted during persistent infection are more complex and differ depending on the infection. In particular, CD8(+) T cell responses differ widely in quantity and quality. In this review we examine these diverse responses and ask how they may arise; in particular, we discuss the function of antigen re-encounter and the CD4(+) T cell responses to and the escape strategies of specific viruses. We focus on studies of four main human pathogens, cytomegalovirus, Epstein-Barr virus, human immunodeficiency virus and hepatitis C virus, and their animal models.
Animals↗
Molecular diagnosis of persistent human papilloma virus infections.
Persistent infections with human papilloma viruses (HPV) can lead to a wide range of benign and malignant epithelial tumors as cutaneous warts or anogenital cancers. Methods principally available for the laboratory diagnosis of HPV infections are cytology and histology, immunocytochemistry, electron microscopy, serology and methods for the detection of HPV-specific DNA. Among the latter are polymerase chain reaction (PCR), Southern blot, dot blot, filter in situ hybridization, in situ hybridization and direct hybridization assays as Hybrid Capture. The advantages and disadvantages of the different assays are reviewed in this article. HPV DNA testing (and typing) by PCR and Hybrid Capture is clinically useful when combined with cytology in screening programs and for managing patients with equivocal cytology or cervical disease.
Humans↗