Cytopathological Effect Research Articles

Study a natural co-infection case of Largemouth bass ranavirus, Aeromonas vickert, and Aeromonas hydrophila in Micropterus salmoides

The largemouth bass (LMB) is a significant aquaculture species widely cultivated in China. High-density culture has led to an increased susceptibility of LMB to infection by the opportunistic bacterium Aeromonas. This study investigates a case of natural co-infection with the Largemouth bass ranavirus (LMBV), Aeromonas veronii, and Aeromonas hydrophila in Sichuan Province, China. To identify the causative agents of the infection, two bacterial strains were isolated from diseased LMB specimens and identified through 16S rRNA sequencing as Aeromonas vickert and Aeromonas hydrophila, both of which are gram-negative bacteria. The infection of LMBV was confirmed through polymerase chain reaction (PCR) analysis of tissue samples from the infected fish. After two blind passes of the virus fluid, the typical cytopathological effect (CPE) can be observed. Phylogenetic analysis of the virus sequences showed the highest similarity with LMBV isolates (ON418985 and MW630113) from Guangdong Province, China. This study offers important insights into diagnosing mixed infections in LMB and provides a reference for future research.

Urogenital System Damaging Manifestations of 3 Human Infected Coronaviruses.

At present, there are no comparative studies on the damage of the 3 coronaviruses infections to the urinary system. Therefore, we reviewed the correlations and differences between invading mechanisms and resultant urogenital system damage by the 3 kinds of coronaviruses in an effort to help doctors in the prevention and treatment of these damages, which will be of significance in improving prognosis and quality of life after rehabilitation. We searched PubMed® for English language articles published since 2003 with the key words "Coronavirus disease 2019 (COVID-19)," "severe acute respiratory syndrome-2 (SARS-CoV-2)," "severe acute respiratory syndrome (SARS)-CoV" and "Middle East respiratory syndrome (MERS)-CoV "with "semen" and "kidney." We also used relevant data from websites including the World Health Organization and Centers for Disease Control and Prevention. Recent studies have revealed that both SARS-CoV and SARS-CoV-2 invade target cells through a membrane-bound angiotensin-converting enzyme 2, an important component of the renin-angiotensin system, which maintains human homeostasis, whereas MERS utilizes host cells' receptor dipeptidyl peptidase 4 for entry. While pneumonia is the most prominent symptom in patients infected by coronaviruses due to the transmission through respiratory droplets, the urogenital system can also suffer from infection with coronaviruses, resulting in renal failure, testicular atrophy etc. The impairments of the genitourinary system would be different with the 3 coronavirus infections but they still have a strong correlation. The pathogenesis and clinical symptoms of SARS-CoV, MERS-CoV and SARS-CoV-2 coronaviruses in the genitourinary system are comparable. All 3 coronaviruses have been found to affect kidney and testicular function. Therefore, both urologists and nephrologists should pay attention to the damage caused by coronavirus infection to the genitourinary system, especially monitoring renal and semen function.

Koilocytic changes are not elicited by human papillomavirus genotypes with higher oncogenic potential.

Koilocytes are considered a common cytopathological effect in patients with human papillomavirus (HPV) infection. Thus, we aimed to elucidate whether koilocytes are common to all HPV infections. Liquid-based cytology samples from 651 patients with abnormal Papanicolaou (Pap) test results were used to analyze the presence of koilocytes and HPV genotype. HPV genotype was determined in complete liquid cytology samples and microdissected cell samples from Pap smear slides using the uniplex E6/E7 polymerase chain reaction method, which can detect 39 mucosal HPV genotypes. Koilocytes were found in 29.3% (191) of all patients. Logistical regression analysis of diverse HPV genotypes revealed that infections with low-risk HPV types (HPV-6b, HPV-40, HPV-42, HPV-61, HPV-74, HPV-89, and HPV-90), probably high-risk HPV types (HPV-53 and HPV-66), and high-risk types (HPV-39 and HPV-56) were significantly associated with the presence of koilocytes. However, HPV-16, HPV-18, and HPV-52, which have higher oncogenic potential, were not found to be associated with koilocytes. These results were confirmed by HPV genotyping using microdissected koilocytes in 27 patients.Most common high-risk types belonging to α-9 and α-7 genotypes appear to rarely induce koilocytic changes. Therefore, koilocytes may provide additional useful information for predicting the risk of progression to high-grade lesions.

Isolation, Characterization, Differentiation and Immunomodulatory Capacity of Mesenchymal Stromal/Stem Cells from Human Perirenal Adipose Tissue.

Mesenchymal stromal/stem cells (MSCs) are immature multipotent cells, which represent a rare population in the perivascular niche within nearly all tissues. The most abundant source to isolate MSCs is adipose tissue. Currently, perirenal adipose tissue is rarely described as the source of MSCs. MSCs were isolated from perirenal adipose tissue (prASCs) from patients undergoing tumor nephrectomies, cultured and characterized by flow cytometry and their differentiation potential into adipocytes, chondrocytes, osteoblasts and epithelial cells. Furthermore, prASCs were stimulated with lipopolysaccharide (LPS), lipoteichoic acid (LTA) or a mixture of cytokines (cytomix). In addition, prASC susceptibility to human cytomegalovirus (HCMV) was investigated. The expression of inflammatory readouts was estimated by qPCR and immunoassay. HCMV infection was analyzed by qPCR and immunostaining. Characterization of cultured prASCs shows the cells meet the criteria of MSCs and prASCs can undergo trilineage differentiation. Cultured prASCs can be induced to differentiate into epithelial cells, shown by cytokeratin 18 expression. Stimulation of prASCs with LPS or cytomix suggests the cells are capable of initiating an inflammation-like response upon stimulation with LPS or cytokines, whereas, LTA did not induce a significant effect on the readouts (ICAM-1, IL-6, TNFα, MCP-1 mRNA and IL-6 protein). HCMV broadly infects prASCs, showing a viral load dependent cytopathological effect (CPE). Our current study summarizes the isolation and culture of prASCs, clearly characterizes the cells, and demonstrates their immunomodulatory potential and high permissiveness for HCMV.

Investigation of the Possible Cytopathological Effect of Human Papillomavirus Infection on p-16INK4a Overexpressed Urothelial Carcinomas of the Bladder in the Urine

Background and objectives: Human papillomavirus (HPV) is well-known as the etiological agent for uterine cervical cancer or carcinoma of the oropharynx, anus and vulva. However, the cytopathologic effect of the HPV infection in urinary bladder tumors has rarely been reported. The present study has been carried out to search for cytopathologic differences between HPV positive and negative cases with urothelial carcinoma. Methods: We examined 91 specimens from 63 patients who underwent transurethral resection or biopsy for papillary urothelial carcinomas between May 2010 and September 2012. p-16INK4a expression was evaluated by immunohistochemistry. Detection of HPV DNA was carried out by in situ hybridization on formalin-fixed, paraffinembedded tissue sections. Urine smears were compared cytomorphologically between HPV-positive and HPVnegative cases. Results: p-16INK4a overexpression was detected in 29 cases (31.9%, 29/91). Of them, HPV DNA was detected in 11 cases. No significant cytopathologic differences were found in tumor cells when HPV-positive and HPV-negative cases were compared. Conclusion: HPV could be detected in urothelial carcinomas of the urinary bladder. There were no significant differences in cytopathologic features of urine smears between HPV-positive and HPV-negative cases with urothelial carcinomas. These results suggest that HPV infection in urinary tract does not add substantial clinically relevant importance to the carcinogenesis and cytomorphology of urothelial carcinomas.

530 WILDTYPE REOVIRUS AS NOVEL ONCOLYTIC THERAPEUTIC APPROACH IN TRANSITIONAL CELL CARCINOMA

You have accessJournal of UrologyUrothelial Cancer: Medical & Surgical Therapy1 Apr 2013530 WILDTYPE REOVIRUS AS NOVEL ONCOLYTIC THERAPEUTIC APPROACH IN TRANSITIONAL CELL CARCINOMA Saladin Helmut Alloussi, Banek Severine, Jörg Hennenlotter, Jens Mundhenk, Christian Schwentner, Ullrich Lauer, and Arnulf Stenzl Saladin Helmut AlloussiSaladin Helmut Alloussi Neunkirchen, Germany More articles by this author , Banek SeverineBanek Severine Regensburg, Germany More articles by this author , Jörg HennenlotterJörg Hennenlotter Tübingen, Germany More articles by this author , Jens MundhenkJens Mundhenk Tübingen, Germany More articles by this author , Christian SchwentnerChristian Schwentner Tübingen, Germany More articles by this author , Ullrich LauerUllrich Lauer Tübingen, Germany More articles by this author , and Arnulf StenzlArnulf Stenzl Tübingen, Germany More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2013.02.1924AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Reoviridae are non-human pathogenic viruses. The family of reoviridae consists of 4 different subtypes. Many studies have proven that the Dearing subtype 3 has oncolytic potential. This potential is apparently related to the RAS protein expression in tumour cells. The aim of this study was to investigate whether all reovirus subtypes have oncolytic potential and whether there are differences in their efficacy, in particular for transitional cell carcinoma. METHODS To evaluate the oncolytic potential, we performed an in vitro head-to-head study for all reovirus subtypes in 12 primary cell cultures of transitional cell carcinoma (TCC). We investigated whether all four wildtype reovirus strains would infect and lyse human TCC cell lines in vitro. 12 different TCC cell lines as well as primary fibroblast and primary urothelial cell lines were examined. Oncolytic effects were quantified as cytopathic effect after light microscopical inspection. Besides, a standardized SRB-Assay was performed to investigate the quantitative cell lyses kinetics. A positive oncolyses was determined as cytopathological effect of at least grade II as well as a death rate of at least 50% of the cells for the SRB-Assay. RESULTS Oncolytic activity was detected for all four reovirus strains in 11 (91.67%) of 12 established urothelial cancer cell lines in qualitative and quantitative analyses. This positive oncolytical effect was seen 72 to 96 h after infection. Interindividually there were statistically significant differences observed, however no virus subtype was superior to the others. As expected, there was no cell lyses in fibroblasts after 96 hours. Interestingly, primary urothelial cells stopped in growing; however a relevant cytopathological effect was not detected. The quantitative oncolytic potential differed in relation to the single observed cell culture and in relation to the chosen reovirus subtype. CONCLUSIONS To our knowledge, this is the first study showing oncolytic activity for all reovirus subtypes TCC cell lines. Efficacy of the different subtypes is interindividually different and cannot be forecast. However the different reovirus strains may be a potentially useful treatment for urothelial cancer. This was underlined by the fact, that all strains didn't infect fibroblasts and healthy urothelial cells significantly. This selectivity could help to develop new therapy option. However further studies are necessary to prove the efficacy in vivo. © 2013 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 189Issue 4SApril 2013Page: e217 Advertisement Copyright & Permissions© 2013 by American Urological Association Education and Research, Inc.MetricsAuthor Information Saladin Helmut Alloussi Neunkirchen, Germany More articles by this author Banek Severine Regensburg, Germany More articles by this author Jörg Hennenlotter Tübingen, Germany More articles by this author Jens Mundhenk Tübingen, Germany More articles by this author Christian Schwentner Tübingen, Germany More articles by this author Ullrich Lauer Tübingen, Germany More articles by this author Arnulf Stenzl Tübingen, Germany More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

An unusual presentation of pediatric acute lymphoblastic leukemia with parotid gland involvement and dactylitis

Mumps infection during the course of childhood acute lymphoblastic leukemia (ALL) treatment has been reported to have a mild course and this was related to the intrinsic low cytopathological effect of the virus, contrasting with the severe course of measles and Varicella zoster virus infections in immunocompromised patients. Herein, we present a three-year-old girl, who was previously vaccinated against mumps infection, admitted with bilateral parotid swelling, dactylitis and serum immunoglobulin M positivity for mumps infection and diagnosed to have ALL with bilateral persistent parotid involvement, inconsistent with mumps infection. Acute leukemia should be suspected during the atypical course of any disease during childhood. Besides, mumps infection at presentation of ALL, as similar to infection emerging during the period of the leukemia treatment, has a mild course.

Cytopathology of Apple stem pitting virus in Nicotiana occidentalis L.

Apple stem pitting virus (ASPV) is a causal agent of stem pitting associated disease in pomes fruit trees. The present report focuses on a cytopathological effect of ASPV infection in a herbaceous host Nicotiana occidentalis ‘37B’. A leaf dip preparation shows predominantly basic virus particles and aggregated particles 800 nm and 3200 nm long respectively. The main cytopathological effect observed in ASPV infected N. occidentalis includes fibrous aggregates of virus particles (massive/or few), formation of membranous vesicles and proliferation of the endoplasmic reticulum.

Mesenchymal stem cells are susceptible to human herpesviruses, but viral DNA cannot be detected in the healthy seropositive individual

Allogeneic stem cell transplantation is often complicated by reactivation of herpesviruses. Mesenchymal stem cells (MSC) are immunomodulatory and may be used to treat graft-versus-host disease. We investigated if herpesviruses infect and can be transmitted by MSC, and if MSC suppress immune responses to various infectious agents. Mesenchymal stem cells from healthy seropositive donors were evaluated with polymerase chain reaction for the most common herpesviruses: cytomegalovirus (CMV), herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2, Epstein-Barr virus (EBV) and varicella zoster virus. The cytopathological effect (CPE) was investigated and viral antigens analyzed by immunofluorescence after in vitro exposure to CMV, HSV-1 and EBV. We also studied MSC effect on lymphocyte stimulation induced by various infectious agents. No viral DNA could be detected in MSC isolated from healthy seropositive individuals. However, a CPE was noted and intracellular viral antigens detected after infection in vitro by CMV and HSV-1, but not by EBV. The CMV and HSV-1 infections were productive. Lymphocyte proliferation by herpesviruses, candida mannan and protein A from Staphylococcus aureus was suppressed by MSC. The data indicate that the risk of herpesvirus transmission by transplantation of MSC from healthy seropositive donors is low. However, MSC may be susceptible to infection if infused in a patient with CMV or HSV-1 viremia. MSC transplantation may compromise the host's defense against infectious agents.

Involvement of PKR and RNase L in translational control and induction of apoptosis after Hepatitis C polyprotein expression from a Vaccinia virus recombinant

BackgroundHepatitis C virus (HCV) infection is of growing concern in public health with around 350 million chronically infected individuals worldwide. Although the IFN-α/rivabirin is the only approved therapy with 10–30% clinical efficacy, the protective molecular mechanism involved during the treatment is still unknown. To analyze the effect of HCV polyprotein expression on the antiviral response of the host, we developed a novel vaccinia virus (VV)-based delivery system (VT7-HCV7.9) where structural and nonstructural (except part of NS5B) proteins of HCV ORF from genotype 1b are efficiently expressed and produced, and timely regulated in mammalian cell lines.ResultsRegulated transcript production and viral polypeptide processing was demonstrated in various cell lines infected with the recombinant VT7-HCV7.9, indicating that the cellular and viral proteolytic machineries are functional within these cells. The inducible expression of the HCV polyprotein by VV inhibits the synthesis of both host and viral proteins over the time and also induces apoptosis in HeLa and HepG2-infected cells. These effects occur accompanying with the phosphorylation of the translation initiation factor eIF-2α. In cells co-infected with VT7-HCV7.9 and a recombinant VV expressing the dominant negative eIF-2α-S51A mutant in the presence of the inductor isopropyl-thiogalactoside (IPTG), protein synthesis is rescued. The IFN-inducible protein kinase PKR is responsible for the translational block, as demonstrated with PKR-/- and PKR+/+ cell lines. However, apoptosis induced by VT7-HCV7.9 is mediated by the RNase L pathway, in a PKR-independent manner.ConclusionThese findings demonstrate the antiviral relevance of the proteins induced by interferon, PKR and RNase L during expression from a VV recombinant of the HCV polyprotein in human cell lines. HCV polyprotein expression caused a severe cytopathological effect in human cells as a result of inhibition of protein synthesis and apoptosis induction, triggered by the activation of the IFN-induced enzymes PKR and RNase L systems. Thus, the virus-cell system described here highlights the relevance of the IFN system as a protective mechanism against HCV infection.

R-Mix cells are faster, at least as sensitive and marginally more costly than conventional cell lines for the detection of respiratory viruses.

To evaluate shell vials of R-Mix, a combination of mink lung cells and human adenocarcinoma cells (strains Mv1Lu and A549, respectively, Diagnostic Hybrids, Athens, OH) to detect respiratory viruses from prospective clinical respiratory specimens and frozen stocks. We compared the performance of R-Mix to conventional culture (CC) using tubes of PMK, Hep-2, and MRC5 to detect respiratory viruses from fresh clinical specimens. For each respiratory specimen submitted to virology, two shell vials of R-Mix were inoculated and examined twice (generally after 24 and 48 h) by an indirect test with a pool of immunofluorescent antisera to influenza A and B, adenovirus, parainfluenza 1-3 and RSV (DAKO, Carpinteria, CA). If positive, testing with monoclonal antisera was done. CCs were incubated for 10 days, examined daily for cytopathological effect, hemadsorbed twice and stained if positive. Cost comparison was done. Lastly, respiratory viruses frozen from previous years were inoculated onto R-Mix. R-Mix was positive for all 29 frozen virus stocks. In the clinical trial, 396 prospective specimens were inoculated into R-Mix and CC. R-Mix identified 21 specimens as respiratory virus positive; CC identified 19. Turn-around time of R-Mix for positive specimens was 1.4 days; for CC it was 5.2 days. Turn-around time of R-Mix for all specimens (positive and negative) was 2.0 days; for CC it was 9.8 days. The overall cost of R-Mix was approximately 11% more than that of CC. R-Mix enabled rapid identification of all the frozen virus stocks representing the seven major respiratory viral groups. When compared to CC, R-Mix was slightly more sensitive than three cell lines (four tubes) used in CC but it was several days faster.

Occurrence ofAeromonas salmonicida, Renibacterium salmoninarum, and Infectious Pancreatic Necrosis Virus in Ontario Salmonid Populations

Abstract The results of samples collected from private and government fish farms and wild and feral fish populations in Ontario from 1981 to 1995 were synthesized to obtain prevalence estimates in salmonids at both the fish and site levels for three pathogens. Renibacterium salmoninarum and Aeromonas salmonicida were both detected on at least one site for every year investigated. Ontario Ministry of Natural Resources (OMNR) culture stations had the highest percentages of sites with infected fish for R. salmoninarum. Natural water bodies had the highest percentages of sites with infected fish for A. salmonicida. Infectious pancreatic necrosis virus (IPNV) was only detected sporadically on some commercial farms and never in OMNR hatcheries or in wild or feral fish. Although screening for any virus that would yield cytopathological effect was carried out during all the years surveyed, no virus other than IPNV was isolated. The low prevalence and “source-specific” presence of IPNV in Ontario demonstrates the ...

Characterization of a virus isolated from the cerebrospinal fluid of patients with epidemic neuropathy

A previously unknown disease, termed epidemic neuropathy (EN), occurred in Cuba between 1991 and 1993. When samples of cerebrospinal fluid (CSF) from 45 patients with EN and 11 controls were inoculated into cultures of VERO cells, almost all (93%) of the samples from the cases of EN but only one (9%) of the control samples produced a slowly progressing cytopathological effect (CPE). Although the results of other studies indicated the presence of a picornavirus-like virus in CSF samples from EN cases, the CPE and other physico-chemical characteristics observed were not those expected of picorn-viruses. Several aetiological factors may have contributed to EN but at least one virus could have played a major role.

Evidence for cytokine regulation of cholesterol metabolism in herpesvirus-infected arterial cells by the lipoxygenase pathway.

Cytokines such as tumor necrosis factor (TNF), interleukin-1 (IL-1), and gamma-interferon (IF) are produced by activated hematopoietic cells. They possess antiviral activity and have other biological activities such as induction of cell proliferation and hemorrhagic necrosis of tumors. Since herpes simplex virus (HSV) infection of human vascular cells is known to produce a biochemical and cytopathological effect virtually indistinguishable from atherosclerosis, we hypothesized that these cytokines many prevent cholesteryl ester (CE) accumulation in arterial smooth muscle cells (SMC) that is seen with herpesvirus infection. We now report that TNF and IL-1 but not gamma-IF prevent CE accumulation in HSV-infected arterial SMC by induction of cyclic AMP-dependent CE hydrolysis. This effect is mediated through the arachidonate 12-lipoxygenase pathway via 12-HETE since pretreatment of cells with several lipoxygenase inhibitors abolishes the antiviral effect and 12-HETE is the major (greater than 99%) lipoxygenase metabolite produced by these cells. This conclusion is further based on our observations that TNF and IL-1 enhance 12-HETE production in SMC and that 12-HETE significantly increases both intracellular cyclic AMP and lysosomal CE hydrolysis. Moreover, dibutyryl cyclic AMP restored a normal phenotype in these virally infected cells. Collectively, these findings identify for the first time a biochemical mechanism involved in the reduction of lipid accumulation in virally infected arterial SMC by these potent cytokines.

Mild course of mumps in patients with acute lymphoblastic leukaemia.

Few details exist on the course of mumps during cytostatic treatment. We therefore describe our observations on the course of mumps seen between 1974 and 1988 in eight children suffering from acute lymphocytic leukaemia (ALL). Our data suggest that in malignant disease the course is rarely severe and that the infection often remains subclinical, as in healthy children. Mumps was accidentally diagnosed by routine lumbar puncture in four of the eight patients. Literature data suggest that the intrinsic low cytopathological effect of the virus, together with a parallelism between T cell response and clinical severity, may explain the usual mild course in immunodepressed patients, contrasting with the severe course of measles and Varicella zoster.

Immunofluorescence detection of herpes simplex virus type 1 antigen in cerebrospinal fluid cells of experimentally infected mice

Experimentally infected mice were used to assess the value of immunofluorescence (IF) procedures in cerebrospinal fluid (CSF) cells in comparison with routine viral culture of CSF for diagnosis of herpes simplex type-1 (HSV-1) encephalitis. Virus specific antigen was detected by immunofluorescence in the majority of CSF cells in 75% of infected animals. In contrast, only 20% of infected mice had positive viral cultures, which sometimes took as long as a week to show a cytopathological effect (CPE). It is concluded that antigen detection by immunofluorescence is a rapid, specific and sensitive technique for demonstrating HSV-1 antigen in CSF cells of experimentally infected mice. Our results put forward a plea for further studies using these techniques on CSF samples from patients with suspected HSV-1 encephalitis. The prerequisites for reliable interpretation of results have been defined in this study.

Non-radioactive in situ hybridization for the detection of cytomegalovirus infections.

Acetylaminofluorene (AAF) modified cytomegalovirus (CMV) DNA probes have been applied for the rapid detection of CMV genomes by non-radioactive in situ hybridization in routinely obtained pathological material. To establish proper protocols, AAF modified mouse satellite DNA and mouse liver were used to investigate the procedural variables. Among these were type and time of fixation, glass slide coating for improved tissue adherence, protease permeabilization of sections, type and time of denaturation and hybridization, probe concentration, post-hybridization washing conditions and immunocytochemical detection. This research has led to a user-friendly procedure which, in addition to cells displaying a cytopathological effect typical for CMV infection, detects with high sensitivity CMV carrying cells that show no histo-pathological alterations. It can be readily applied in routine clinical-diagnostic laboratories.

Beet western yellows virus in phloem of pennycress

The effects of beet western yellows virus on pennycress phloem were investigated using electron microscopy and collecting at intervals after aphid inoculation. Particles were seen in mature sieve elements from the earliest collection date, but they became less numerous in sieve elements of older leaves as the infection progressed. The first cytopathological effect in phloem parenchyma cells was the appearance of virus vesicles that became enclosed in ER membranes and attached to the outer layer of the nuclear envelope. At the time of vesicle attachment and thereafter, virions appeared in phloem parenchyma cell nuclei. In some instances virions appeared in the cytoplasm, but in many cases they remained in nuclei, often occupying a perinucleolar position. Aspects of the virus invasion and distribution in pennycress phloem are compared to effects of other luteo-viruses.

Effect of hepatitis A virus infection on cell metabolism in vitro.

Hepatitis A virus (HAV), when inoculated into cultures of the PLC/PRF/5 cell line which produces the surface antigen of hepatitis B virus (HBsAg), showed growth characteristics different from those of other picornaviruses. Antigen of HAV (HAAg) is expressed only about 10 days after infection. No major impact on the overall macromolecular biosynthesis of the host cells is observed. The growth rate of HAV-infected and uninfected cells was comparable, although the plating efficiency of infected cells was lower. Different hormonal factors were tested for their ability to stimulate viral antigen expression. Dexamethasone or prostaglandin E1 added to the culture medium increased HAAg expression; insulin reduced expression. Persistent infection of hepatoma cells by HAV never led to a cytolytic infection. In temperature-shift experiments, an adverse effect on the expression of HAAg and HBsAg was observed. In all experiments, the amounts of HBsAg in HAV-infected cells were reduced. On the whole, no major influence on host-cell metabolism is observed in cells persistently infected with HAV. Cell-mediated immunological response as a mechanism of pathological changes in HAV-infected liver is, therefore, more likely than a cytopathological effect.

Rickettsia Mooseri Infection in the Fleas Leptopsylla Segnis and Xenopsylla Cheopis

Detailed observations on the acquisition and propagation of experimental Rickettsia mooseri infection in two species of fleas are presented. Rickettsia mooseri infection became detectable by means of the direct fluorescent antibody test about 2 days earlier in Leptopsylla segnis than in the putative vector, Xenopsylla cheopis. By the 6th day after the infective feeding, the entire lining and the lumen of the midgut in L. segnis contained masses of rickettsiae and the agent was being passed in the feces of the flea, whereas in X. cheopis these events did not occur until the 8th day. Basic behavioral differences in the two species of flea may explain these discrepancies and also influence their ability to serve as vectors of murine typhus. As a semisessile flea and sustained feeder, L. segnis only rarely attaches to a second individual and thus has an opportunity to acquire a heavy dose of rickettsiae, if feeding on a rickettsemic host. X. cheopis, in contrast, feeds rapidly and intermittently, even on man, and generally leaves its host soon thereafter, later returning to the same or another host to feed again. While L. segnis may not be as efficient a vector as X. cheopis regarding the intramurine cycle or transmission to man of murine typhus, the dense accumulation of infective feces on certain sites on the fur of the host raises the possibility of air-borne infection to man or rodent. Infection with R. mooseri had no effect on the survival of X. cheopis and L. segnis. Furthermore, no visible cytopathological effect was found in the paraffin-embedded sections of infected fleas.(ABSTRACT TRUNCATED AT 250 WORDS)