Comparison of guinea pig cytomegalovirus and guinea pig herpes-like virus: growth characteristics and antigentic relationship.

The growth characteristics of guinea pig cytomegalovirus (GPCMV) and guinea pig herpes-like virus (GPHLV) in cell cultures were compared. Guinea pig fibroblast cells were highly susceptible to infection with both viruses, whereas guinea pig kidney cells were sensitive only to GPHLV. No cytopathic effect was observed in the latter cell system after infection with GPCMV,nor was there an increase in virus titer, although the cirus persisted in the kidney cells for 2 to 3 weeks postinfection. Electron microscope studies showed nonvirion tubular structures in GPCMV -infected fibroblast cells, but not in GPHLV- infected cells. Large packages of enveloped nuclear virus particles were commonly seen in GPHLV -infected cells, especially kidney epithelial cells, but none were found in the GPCMV -infected fibroblasts. Complete enveloped extracellular virus particles were present in both virus-cell systems. Both viruses showed narrow host spectra and replicated well only in guinea pig cells although GPHLV multiplied to some degree in rabbit cells. No antigenic relationship could be demonstrated between the two viruses using antisera specific for each virus that was produced in rabbits and guinea pigs. Rabbits produced high neutralizing antibody titers to GPHLV, whereas guinea pigs were the animals of choice for GPCMV antiserum production.     

Comparison of guinea pig cytomegalovirus and guinea pig herpes-like virus: pathogenesis and persistence in experimentally infected animals.

The pathogenesis of guinea pig cytomegalovirus (GPCMV) and guinea pig herpes-like virus (GPHLV) in guinea pigs was compared. Animals were inoculated with the two viruses by different routes and sacrificed after varying periods of time. GPCMV was consistently isolated from salivary gland 2 weeks postinoculation and thereafter following intraperitoneal or subcutaneous incoulaton. Virus was less frequently found in other tissues including blood, spleen, and kidney. Intranuclear inclusions were seen in tissue sections of salivary gland after inoculation with GPCMV- infected tissue suspension, but were only rarely found after inoculation with tissue culture virus. In GPHLV-infected guinea pigs, consistent latent infection of leukocytes and other tissues was detected by cocultivation techniques. Intranuclear inclusions were not found in the spleen, salivary gland, or other infected tissues after GPHLV infection with either tissue culture virus or infected tissue suspension. Guinea pigs inoculated with GPCMV produced high titers of specific neutralizing antibody to the homologous virus; those inoculated with GPHLV developed long-term viremia accompanied by minimal neutralizing antibody levels to the virus.     

Pathogenesis of attenuated Junin virus in the guinea pig model

The purpose of this work was to elucidate the pathogenesis of attenuated Junin virus (JV) strains in the guinea pig model. Three groups of guinea pigs were infected by the IM route with 10(3) PFU of the XJC13 and XJO-attenuated strains or with the XJ pathogenic strain of JV, respectively. Viremia was studied at 3, 5, 7, 9, 12, and 14 days postinfection (pi) (a) in serum samples of all animals and in washed cells from XJC13-infected guinea pigs by conventional techniques and (b) in whole blood samples from XJC13 and XJO animals by coculture with Vero cells. Virus spread was studied at 14 days pi in brain, spleen, lymph nodes, and bone marrow by parallel suckling mouse inoculation or organ homogenates and coculture of cell suspensions with Vero cells. By coculture techniques of whole blood, an otherwise undetectable viremia was demonstrated for both attenuated strains throughout the observation period. In contrast, XJ viremia was easily detected by direct techniques, as has already been shown. Attenuated virus was also shown to reach brain and bone marrow when coculture methods were employed. But titers were always markedly lower than those of the pathogenic strain. The sustained viremia demonstrated in guinea pigs infected with either attenuated strain explains the mode of viral dissemination and accounts for viral rescue and antigen detection from some organs. These results suggest that attenuated strains do not differ greatly in their invasive capacity in guinea pigs, but later on viral replication is impaired. Therefore, these findings reveal potential risks and should be noted when developing human vaccines.     

Cytolysis of Junin infected target cells by immune guinea pig spleen cells

Spleen cells from guinea pigs infected with an attenuated strain of Junin virus (the causative agent of Argentine hemorrhagic fever) specifically lysed virus-infected syngeneic target cells in vitro. This activity was detected as early as 6 days after infection, reached a maximum on days 10-13, and persisted at lower levels, at least through day 30. Monoclonal antibody to guinea pig T cells had no effect on the activity. After B or T cell enrichment techniques, the cytolysis was found with the B cell fraction. Aggregated IgG blocked the cytolysis. These characteristics suggested lytic activity was mediated at least in part by an antibody-dependent cell-mediated cytotoxicity (ADCC) mechanism. Although some cytolysis could be detected by using exogenously added antiserum and normal spleen effector cells, such reconstruction showed less efficient killing than when spleen cells from Junin-infected guinea pigs were used. This apparent discrepancy was resolved when spleen cells from these infected animals exhibited enhanced activity in non-viral ADCC systems as well. The cytotoxic activity by spleen cells against Junin-infected targets was detected only with non-fatal Junin infections. Cytolysis could not be measured in spleen cell suspensions from guinea pigs lethally infected with Junin virus; i.e. adults infected with a virulent strain of Junin and baby guinea pigs or immunosuppressed adult animals infected with an attenuated strain. However, spleen cells from both the immunosuppressed, infected adults and the adult guinea pigs infected with a virulent strain of Junin were able to mediate cytotoxicity in a nonviral system (antibody-sensitized Vero cells). The development of spleen cell cytotoxicity by Junin-infected guinea pigs against Junin-infected target cells correlated with whether the infection was resolved or was lethal.     

A latent guinea pig herpes-like virus: isolation and envelopment.

A guinea pig herpes-like virus (GPHLV) has been isolated from randomly selected guinea pigs. This virus is serologically related, if not identical, to the guinea pig herpes-like virus isolated by Hsiung-Kaplow. The frequency of latent infection in guinea pigs was found to be highly variable among animals of the same commercial origin. Ultrastructural studies have shown that the morphological development of this virus was similar to that reported for other herpes viruses in the early stages, but frequently differed at the envelopment stage. In the cytoplasm, virus particles were associated with electron-dense zones from which they acquired a thick and rough envelope.     

Experimental infection and immune response of guinea pigs with varicella-zoster virus.

An immune response (fluorescent antibody to membrane antigen) was detected in guinea pigs inoculated with varicella-zoster virus (VZV) adapted to guinea pig embryonic cells, including the Oka vaccine strain, even when inoculation was by an external route, i.e., nasal or corneal. Live or UV-inactivated virus having the same virus titer before irradiation was administered to guinea pigs by the corneal route, and antibody induction was detected only with live virus. The transmission of VZV from infected guinea pigs to noninfected ones was suggested by the appearance of antibody in the serum of the latter, who were kept in the same cage. The time course of the appearance of humoral and cellular immune responses in guinea pigs was examined by the fluorescent antibody to membrane antigen test and the skin reaction, with varicella antigen representing delayed-type hypersensitivity. When VZV was injected subcutaneously, skin reaction appeared as early as 4 days after inoculation, which preceded the appearance of detectable antibody by 2 to 6 days. In in vitro studies, the Oka vaccine showed a higher adsorption rate and better growth in guinea pig embryonic cells than did other wild-type strains when assayed by the infectious center assay. These results suggest that a system of VZV adapted to guinea pig cells and guinea pigs provides a good animal experimental model for immunological study of VZV infection.     

Respiratory Marburg virus infection in guinea pigs

Summary Marburg virus (MV) reproduction in organs, hematological and pathological changes were studied by virological and clinical methods, light and electron microscopy in guinea pigs respiratory challenged by the virus. Liver and spleen were most affected by MV, as in parenteral infection. The sequential involvement of cells in virus replication was also the same as in parenteral infection, with monocytoid-macrophagal cells infected first, followed by hepatocytes, spongiocytes, endotheliocytes and fibroblasts. Hemopoietic cells showed evidence of severe damage in respiratory infected guinea pigs. A distinguishing feature of the respiratory infection was close contact of leucocytes with MV infected cells. It is suggested that the entrapment and accumulation of MV in the lungs of respiratory infected guinea pigs makes possible the enfoldment leucocyte attack which does not, however, result in destruction of the infected cells.     

Persistence of Adenovirus 5 in Guinea Pigs

One intracardiac inoculation of adenovirus 5 in guinea pigs leads to virus persistence in different organs, viz., 5 days in lungs and liver, 14 days in blood and lymph nodes, and 56 days or more in the spleen. After cultivation of tissue cells for 1 week, virus was recovered from blood, lymph nodes, or spleen lymphocytes, but virus could be detected directly in cells only when organs were removed within 48 h of inoculation. To determine how the virus persisted in low concentrations and as a latent infection, spleens were primarily selected for study by three techniques: homogenization of spleens, suspended Maitland fragment cultures, and in vitro cultivation of spleen cells. The last procedure showed virus in fibroblast-like cells (probably macrophages or reticuloendothelial cells) for 56 days after infection of guinea pigs. With other methods, the virus was found only within the first 2 days after inoculation.     

Cyclophosphamide immunosuppression during lymphotropic herpesvirus infection in the guinea pig model. A histopathologic and virologic study.

Guinea pigs infected with lymphotropic herpesvirus (GPHLV) were given the immunosuppressive agent cyclophosphamide (Cy). All Cy-treated animals revealed the expected lymphoid depletion of spleen and lymph node B zones. Acute GPHLV infection of Cy-treated animals resulted in increased blood and spleen leukocyte viral infectivity titers and lymphoid tissue lesions containing cells positive for GPHLV antigen and intranuclear inclusions. During latent GPHLV infection, Cy treatment resulted in declining leukocyte viral infectivity titers without pathologic lesions. Morphologic data suggest that tissue histiocytic cells may be involved in the productive viral infection observed in Cy-immunosuppressed animals during acute GPHLV infection. During latency, however, infectious virus appears restricted to a Cy-sensitive, probably lymphoid, cell. This animal model appears useful for the study of lymphotropic viral infection during immunosuppression.     

Protection of guinea pigs against experimental Argentine hemorrhagic fever by purified human IgG: importance of elimination of infected cells

Antibody-containing plasma from patients recovered from Argentine hemorrhagic fever (AHF) is of proven value in treatment of the acute disease, but the possibility of transmitting blood-borne organisms such as HIV and hepatitis virus detracts from this approach. Purified human immune plasma fractions IgG1,2,4, IgG1,2,3,4 and F(ab')2 neutralized Junin virus in vitro. IgG1,2,3,4 and IgG1,2,4 lysed (in the presence of complement) cells infected with Junin virus, and protected infected guinea pigs from AHF. However, large quantities of the immune F(ab')2 fraction from the same plasma pool failed to protect guinea pigs from death, to increase the mean time to death, and to diminish virus load in target organs of infected guinea pigs. This suggests that elimination of infected cells rather than virus neutralization may play a critical role in protection against Junin virus.     

Evaluation ofprimary blood monocyte and bone marrow cell culture for the isolation of Rickettsia rickettsii.

Rickettsia rickettsii was isolated from experimentally infected guinea pigs by culture of blood monocytes and bone marrow cells, and from experimentally infected rhesus monkeys by blood monocyte culture. Rickettsiae were identified in monocyte-macrophage monolayers stained by Giménez or flourescent antibody techniques. A total of 78 culture attempts were made from 20 guinea pigs and 16 monkeys. The success of isolation of R. rickettsii in culture was positively correlated with the numbers of rickettsiae present in the blood and bone marrow. in cultures derived from infected guinea pigs, rickettsiae were usually observed after 5 to 7 days of culture, and in monkeys monocyte cultures they were usually observed within 3 to 5 days. Positive cultures were derived from guinea pigs and monkeys as early as the first day of fever and 1 to 3 days before the appearance of other clinical signs. Monocyte cultures became negative with the resolution of rickettsemia and concomitantly with the appearance of serum antibody. Monocyte culture isolation of R. rickettsii may be as sensitive for the detection of rickettsiae in blood and marrow as the intraperitoneal inoculation of guinea pigs or the plaque assay technique. Because of the simplicity of the method and because rickettsiae were often identified within 3 to 5 days after initiation, the monocyte culture technique may be useful in the early diagnois of human rickettsial disease.     

Estimation of the mutagenic potential of the trematode Opisthorchis felineus in experimentally infected guinea pigs

We studied the mutagenic potential of the trematode Opisthorchis felineus in experimentally infected guinea pigs by chromosome analysis. The investigation was conducted on 30 treated (experimentally infected) and 20 normal (uninfected) guinea pigs (Cavia porcellus). A sample of living metacercariae of O. felineus was obtained from the muscle of naturally infected crucian carp captured in the Tom River, and 1 ml suspension containing approximatelly 50 metacercariae in 0.9% NaCl solution was individually given p.o. to guinea pigs that were used as treated specimens, whereas normal guinea pigs from the same stock were given 1 ml 0.9% NaCl solution per individual to serve as controls. The treated and control animals were killed by CO₂ asphyxiation and decapitation at 7, 15, 30, 45, and 120 days after contamination. The smears of bone marrow cells for chromosome analysis were prepared by a standard method. Statistical analysis of the data was done using Student's t-test. We found that experimental infection of guinea pigs with O. felineus induced significantly high frequencies of hypoploid cells and, at the 120th day p.i., led to a considerable incidence of chromatid breaks and polyploidy in bone marrow cells. Received: 16 October 1997 / Accepted: 15 January 1998     

Quantitative problems in bone marrow transplantation by peripheral blood stem cells

Investigation into radiation bone marrow aplasia in mice, guinea pigs, dogs and clinical trials in man presented clear evidence of successful engraftment of autologous or allogeneic peripheral blood stem cells. The quantitative donation problems are discussed arising with the use of continuous cytopheresis to obtain a sufficient quantity of peripheral blood mononuclears (stem cells) for repopulation of aplastic bone marrow. Although bone marrow repopulation is possible by using peripheral blood mononuclears (stem cells) in individual cases, the method can only be used in practice after discovering an appropriate stimulator able to augment several times the number of bone marrow stem cells in the peripheral blood, or a new method for stem cell multiplication in vitro.     

Analysis of the B and T cell response in guinea pigs induced with recombinant vaccinia expressing foot-and-mouth disease virus structural proteins

Summary.  Recombinant vaccinia viruses expressing foot-and-mouth disease virus (FMDV) P1 and VP1 genes have been used to study the immune response induced by these viral polypeptides in guinea pigs. Anti-FMDV antibodies, but not neutralizing activity, were detected in the sera from immunized animals. The results indicate that both CD4+ and CD8+ FMDV-specific T cells were induced by the vaccinia recombinants. Consistently with the activation of CD4+ T cells, lymphocytes from immunized animals specifically proliferated in vitro in response to whole virus. The induction of virus-specific CD8+ T cells was determined by CTL assay of immune splenocytes restimulated in vitro with FMDV infected cells. Altogether, the results obtained indicate that both B and T cell immune responses to FMDV are elicited upon immunization of guinea pigs with vaccinia recombinants expressing FMDV structural polypeptides. Accepted September 18, 1997 Received June 19, 1997     

In vitro guinea pig leukocyte reactions to Rickettsia rickettsii.

The presence of cell-mediated immunity in Rocky Mountain spotted fever-infected guinea pigs was determined by two in vitro assays: whole blood lymphocyte transformation (LT) and macrophage migration inhibition. Increased LT was detected as early as 1 week in guinea pigs infected with Rickettsia rickettsii and treated with oxytetracycline and was detected by two weeks in infected but untreated guinea pigs. Elevated LT was still detectable at 10 weeks postinfection. Guinea pigs vaccinated with killed rickettsiae failed to develop lymphocyte responsiveness; however, there was a rapid lymphocyte response after challenge with live organisms, suggesting potentiation by the vaccine. Vaccinated guinea pigs that were challenged and then treated with antibiotic failed to develop LT, suggesting that infection is necessary for the observed response. Macrophage migration inhibition was detected in both infected and vaccinated guinea pigs by 1 week after infection, but this response was no longer detected 4 to 5 weeks later. Antibody appeared at 2 to 3 weeks postinfection and was present at low levels through week 10. Antibody-treated rickettsiae were phagocytized and destroyed by guinea pig peritoneal macrophages, whereas normal serum-treated rickettsiae replicated and eventually destroyed the phagocytes.     

骨髓间充质干细胞增殖分化能力可随鼠龄增长而下降

背景：骨髓间充质干细胞是理想的组织工程种子细胞来源,但是不同年龄的骨髓间充质干细胞体外增殖、分化特点有很大差异,有关年龄与骨髓间充质干细数量的关系目前尚缺少系统研究。 目的：观察不同鼠龄大鼠骨髓间充质干细胞诱导分化活性的差异。 方法：通过全骨髓贴壁培养法,体外分离、纯化、扩增SD大鼠骨髓间充质干细胞,倒置相差显微镜观察形态学特点,流式细胞仪检测细胞表面标记,体外诱导骨髓间充质干细胞向成骨细胞、成软骨细胞分化并鉴定。取第3代2,4,6,8,12周龄和10,12月龄大鼠骨髓间充质干细胞成骨诱导1,2,3周,采用酶联免疫法检测骨钙素含量。 结果与结论：体外培养的骨髓间充质干细胞为贴壁生长,长梭形成纤维细胞样细胞,可增殖形成克隆;流式细胞仪分析骨髓间充质干细胞CD29、CD90表达阳性,CD45表达阴性,CD44部分表达;经成骨分化诱导,细胞碱性磷酸酶染色阳性,茜素红染色阳性;经成软骨分化诱导,阿利辛蓝染色阳性,可见通过全骨髓贴壁法可成功地从大鼠骨髓中分离出骨髓间充质干细胞。通过不同鼠龄骨髓间充质干细胞诱导成骨分化后骨钙素含量测定得出骨髓间充质干细胞增殖分化能力随鼠龄的增长而下降。中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程全文链接：     

Cytomegalovirus-induced mononucleosis in guinea pigs.

The effects of cytomegalovirus (CMV) infection on hematopoietic and lymphoid tissues were studied in guinea pigs. Blood parameters, histopathology, and virus distribution in the bone marrow, spleen, lymph nodes, and thymus were assessed during primary nonlethal acute and chronic guinea pig CMV infection. Transient hematological changes comparable to those seen in human CMV mononucleosis were observed during acute infection. These included anemia and leukocytosis with atypical lymphocytes. Splenomegaly and stimulation of spleen and lymph node T- and B-cell areas were also noted. These changes occurred at the peak of virus recovery from all tissues tested, as well as from macrophages and B- and T- cell-enriched spleen subpopulations. Virus was cleared rapidly from blood and bone marrow; blood counts, spleen size, and histology returned to normal within 1 month after virus inoculation. However, guinea pigs failed to eliminate the virus completely from lymphoid tissues, since virus persisted in splenic macrophage and B-lymphocyte-enriched populations during chronic infection. The data suggest that CMV-infected mononuclear cells play a role in the establishment of generalized acute infection and virus persistence.     

TT virus replicates in stimulated but not in nonstimulated peripheral blood mononuclear cells

TT virus (TTV) is an unenveloped, single-stranded, circular-DNA virus which resembles members of the Circoviridae, that is commonly found in humans and which lacks pathological consequences for the infected host. TTV replication has been demonstrated in bone marrow cells but not in peripheral blood mononuclear cells (PBMC), suggesting that hematopoietic cells must be activated to support TTV replication. To test this hypothesis, PBMC from two naturally TTV-infected individuals and from two healthy TTV-DNA negative donors infected in vitro with a TTV-DNA-positive serum were cultured in the presence (stimulated) or absence (unstimulated) of phytohemagglutinin, lipopolysaccharide, and interleukin-2. TTV-DNA was detected in both stimulated and unstimulated PBMC. However, TTV-DNA replicative intermediates and mRNA were detected only in stimulated PBMC. Furthermore, TTV-DNA and mRNA were detected in PBMC from two TTV negative donors reinfected with supernatants from TTV-infected stimulated cells but not when using culture supernatants from unstimulated cells. These results demonstrate that TTV replicates in PBMC only when stimulated.     

Ebola virus glycoprotein demonstrates differential cellular localization in infected cell types of nonhuman primates and guinea pigs

BACKGROUND: In vitro studies have previously shown that Ebola virus glycoprotein (GP) is rapidly processed and largely released from infected cells, whereas other viral proteins, such as VP40, accumulate within cells. OBJECTIVE: To determine infected cell types in which Ebola virus GP and VP40, individually, localize in vivo. METHODS: Immunohistochemistry and in situ hybridization using GP- and VP40-specific antibodies and genetic probes were used to analyze archived tissues of experimentally infected nonhuman primates and guinea pigs and Vero E6 and 293 cells infected in vitro. RESULTS: The GP antigen was consistently present in hepatocytes, adrenal cortical cells, fibroblasts, fibroblastic reticular cells, ovarian thecal cells, and several types of epithelial cells, but was not detected in macrophages and blood monocytes of animals, nor in Vero cells and 293 cells. All GP-positive and GP-negative cell types analyzed contained VP40 antigen and both GP and VP40 RNAs. CONCLUSIONS: Ebola virus GP appears to selectively accumulate in many cell types infected in vivo, but not in macrophages and monocytes. This finding suggests that many cell types may have a GP-processing pathway that differs from the pathway described by previous in vitro studies. Differential cellular localization of GP could be relevant to the pathogenesis of Ebola hemorrhagic fever.     

Pathogenesis of Lassa virus infection in guinea pigs.

A rodent model for human Lassa fever was developed which uses inbred (strain 13) and outbred (Hartley) guinea pigs. Strain 13 guinea pigs were uniformly susceptible to lethal infection by 2 or more PFU of Lassa virus strain Josiah. In contrast, no more than 30% of the Hartley guinea pigs died regardless of the virus dose. In lethally infected strain 13 guinea pigs, peak titers of virus (10(7) to 10(8) PFU) occurred in the spleen and lymph nodes at 8 to 9 days, in the salivary glands at 11 days, and in the lung at 14 to 16 days. Virus reached low titers (10(4) PFU) in the plasma and brain and intermediate titers in the liver, adrenal glands, kidney, pancreas, and heart. In moribund animals, the most consistent and severe histological lesion as an interstitial pneumonia. In contrast, the brain was only minimally involved. The immune response of lethally infected strain 13 guinea pigs, as measured by the indirect fluorescent antibody test, was detectable within 10 days of infection and was similar in timing and intensity to the fluorescent antibody test response of both lethally infected and surviving outbred animals. In contrast to the fluorescent antibody response, neutralizing antibody developed late in convalescence and was thus detected only in surviving outbred guinea pigs. The availability of a rodent model for human Lassa fever in uniformly susceptible strain 13 guinea pigs should facilitate detailed pathophysiological studies and efficacy testing of antiviral drugs, candidate vaccines, and immunotherapy regimens to develop control methods for this life-threatening disease in humans.