Cytomegalovirus-induced reactivation of Toxoplasma gondii pneumonia in mice: lung lymphocyte phenotypes and suppressor function.

Active cytomegalovirus (CMV) infection is associated with immunosuppression and predisposes to the development of life-threatening superinfections in immunocompromised patients. In a mouse model of virus-induced immunosuppression, acute murine CMV (MCMV) infection induced reactivation of dormant Toxoplasma gondii infection, producing Toxoplasma pneumonia. Changes in lung lymphocyte numbers and phenotypes appeared to be integral to the pathogenesis of MCMV-induced reactivation of T. gondii pneumonia. Numbers of lung CD4+ cells decreased during acute MCMV infection in mice with dormant T. gondii infection as well as in previously uninfected mice. Dually infected mice subsequently developed reactivation of Toxoplasma pneumonia. The pneumonia was characterized by a large influx of T lymphocytes, predominantly CD8+ cells, into the lungs. These lung lymphocytes markedly suppressed the ability of immune splenocytes to proliferate in response to T. gondii antigens and concanavalin A in vitro. These results suggested that the initial fall in the numbers of lung CD4+ cells observed after MCMV infection may have induced reactivation of T. gondii infection in the lungs. The subsequent pneumonia appeared to be a manifestation of a massive influx of T lymphocytes, especially CD8+ cells, into the lungs.     

An unusual cause of acute respiratory distress in a patient with AIDS: primary infection with Toxoplasma gondii

Hypoxemic pneumonia in AIDS patients is mainly caused by Pneumocystis carinii, Toxoplasma gondii and CMV, although the significance of CMV recovery in BALF is often unclear. Since lung involvement generally occurs during reactivation, T. gondii is not expected to be demonstrated in patients without evidence of past infection with this agent. We report a fatal case of pneumonia revealing a T. gondii primary infection diagnosed thanks to the PCR analysis of the BALF.     

Activation of latent murine cytomegalovirus in vivo and in vitro: a pathogenetic role for acute infection

Many cytomegalovirus (CMV) infections result from activation of virus previously latent in the host. Murine models of latent CMV infection have been developed in which latent virus can be activated in vivo by immunosuppression or by coculture of splenic lymphocytes in vitro. In the present study, latent murine CMV (MCMV) could be activated from lymphocytes of mice regardless of genetic strain, age at time of virus inoculation, or use of syngeneic or allogeneic fibroblasts for coculture. After intraperitoneal inoculation, virulent virus was activated from lymphocytes more often than attenuated MCMV (69% vs. 20% of lymphocyte cocultures were positive, respectively). Latent MCMV was not detected in lymphocytes after subcutaneous inoculation of weanling mice but could be activated from mice infected subcutaneously as newborns. The absence of latent infection in the lymphocytes of the mice that had been inoculated as weanlings was due to lack of virus replication in the spleen during acute infection.     

Acute cytomegalovirus pneumonia and hepatitis presenting during acute HIV retroviral syndrome

Cytomegalovirus (CMV) disease is a frequent opportunistic infection that usually occurs in the late stages of HIV infection as a result of reactivation of a latent infection. We report a case of a 23-year-old man with acute retroviral syndrome complicated by coexisting CMV pneumonia and CMV hepatitis, which were documented by histopathological examination. His CMV pneumonia and hepatitis were assumed to be primary CMV diseases owing to the absence of CMV IgG antibody. To the best of our knowledge, this is the first case of simultaneous CMV pneumonia and hepatitis occurring as primary CMV diseases during primary HIV infection. This case indicates that invasive CMV diseases such as pneumonia and hepatitis should be considered even in patients with primary HIV infection.     

Cytomegalovirus pneumonia

Cytomegalovirus (CMV) pneumonia is a major cause of morbidity and mortality in allogeneic bone marrow transplant and lung transplant recipients. However, its role as a cause of lung disease in patients with the human immunodeficiency virus (HIV) is controversial. Although CMV can be isolated from lung specimens in patients with HIV-associated respiratory illness, it is rarely the causative pathogen. Most adults with HIV infection have latent CMV infection of many tissues including the lung, and most cases of CMV pneumonia are believed to be caused by reactivation secondary to severe immunocompromise. The clinical presentation of pneumonia caused by CMV pneumonia is similar to that of Pneumocystis carinii, with fever, cough, hypoxemia, and diffuse radiographic opacities. Although the two infections can not be differentiated on clinical grounds alone, the presence of extrapulmonary CMV disease and the use of recent cytotoxic chemotherapy or corticosteroids suggests the diagnosis of CMV pneumonia. Although approximately 60% of cases respond initially to anti-CMV therapy, the disease is associated with progression and high early mortality, probably related to severe underlying immunosuppression.     

Use of temperature-sensitive mutants of mouse cytomegalovirus as vaccines

Three temperature-sensitive (ts) mutants of mouse cytomegalovirus (MCMV) were compared with parent virus for their ability to produce acute infection, to stimulate protection against a lethal challenge with salivary gland MCMV, and to become latent and then be reactivated. During the acute phase of infection, ts mutant virus demonstrated very limited replication. During the later phase of infection (seven to 14 days after challenge), titers of virus in the pancreas and salivary glands in mice infected with parent virus continued to rise, whereas no virus could be detected in mice infected with the ts mutants. Prior infection with parent virus or the ts mutants protected susceptible mice from a lethal dose of salivary gland MCMV. One year after infection, treatment of mice with an immunosuppressive regimen resulted in reactivation of parent and ts mutant virus. Reactivated virus recovered from mice infected with ts mutant virus remained temperature sensitive.     

Intra-abdominal bacterial infection reactivates latent pulmonary cytomegalovirus in immunocompetent mice

Critically ill surgery patients are susceptible to pulmonary reactivation of latent cytomegalovirus (CMV), but what triggers this reactivation is unknown. Immunosuppression and bacterial sepsis are thought to stimulate reactivation of CMV, and in this study it was hypothesized that immunosuppressive effects of surgery with or without concomitant bacterial infection may reactivate latent CMV. Mice infected with CMV were allowed to develop latent infections. Latently infected mice underwent a laparotomy with cecal ligation and puncture (CLP; n=30), a laparotomy alone (sham; n=10), or no surgery (control; n=5). Lung tissue homogenates were evaluated for viral activity, and, 2 and 3 weeks after CLP, lungs of 7 of 7 and 5 of 5 mice, respectively, showed reactivation of latent CMV. In contrast, lungs from all sham-operated animals and controls showed no viral reactivation. These findings demonstrate that surgery with subsequent intra-abdominal bacterial infection reactivated CMV in lungs of latently infected mice. The mechanism of this reactivation is unknown but likely involves cytokines induced by sepsis.     

The source of murine cytomegalovirus in mice receiving kidney allografts

The sources of cytomegalovirus (CMV) infection in kidney transplant recipients include reactivation of latent endogenous virus in the recipient or reactivation of latent virus in donated blood or kidney. In the present study, kidneys from mice latently infected with one strain of murine CMV were transplanted into either uninfected recipients or recipients latently infected with a different strain of murine CMV; the recipients were immunosuppressed, subsequently were cultured for murine CMV, and the infecting strain was characterized. The results show that reactivation of latent murine CMV from the donated kidney can be the source of active infection in previously uninfected recipients. When the recipient had been previously infected, however, reactivation of the endogenous recipient strain of murine CMV was the source of active infection in 10 of 12 instances. At no time were both exogenous and endogenous strains of virus reactivated simultaneously. These studies indicate that donor kidney may be the source of latent virus in the uninfected recipient but that endogenous virus predominates in previously infected recipients.     

Aging and reactivation of latent murine cytomegalovirus.

BALB/c mice were experimentally infected with murine cytomegalovirus (MCMV) to discover whether latent MCMV persisted in aging mice and to examine the effect of aging on MCMV reactivation. Latently infected mice received saline, cyclophosphamide, or allogeneic blood at 6 and 18 months of age. MCMV DNA was detected by polymerase chain reaction in submaxillary salivary gland biopsy specimens from saline-treated young and old mice. Evidence of MCMV reactivation was sought by culture of biopsy specimens and by MCMV IgG ELISA of pre- and posttreatment sera from all animals. Very few cyclophosphamide- or saline-treated mice reactivated MCMV at either age, but young transfused mice reactivated MCMV significantly more often than did old transfused mice. These experiments indicate that MCMV DNA persists in the salivary gland of aging mice but that the likelihood of MCMV reactivation does not increase with age.     

An unusual etiology of viral hepatitis in three renal transplant recipients with normal graft function

Liver impairment in renal transplant recipients is not a common complication and is associated, in most cases, with viral infections (HBV, HCV, HVD, HGV) or drug hepatotoxicity (Cyclosporin, Azathioprine, statins). Cytomegalovirus (CMV) infection is common, with 50 to 80% of the adult population being seropositive for CMV antibodies. In immunocompetent individuals, primary infection is usually asymptomatic or associated with minor illness. CMV remains latent after primary infection. In immunocompromised patients, as in renal transplant recipients or transplant recipients of other solid organ or bone marrow, the virus can cause serious disease. This could be the result of newly acquired infection or reactivation of the latent virus. One of the organs involved in CMV disease is the liver. The subjects of this report are renal transplant recipients with liver impairment due to CMV induced acute hepatitis.     

Prevention and treatment of cytomegalovirus infection after marrow transplantation

Based on the known epidemiology of cytomegalovirus (CMV) infection, primary infection among seronegative patients is preventable by use of seronegative blood products including marrow. A potential alternative is use of leukocyte-depleted blood products. Efficacy of passive immunoprophylaxis remains uncertain, and this modality cannot be recommended until additional studies are available. Antiviral agents can be used to suppress or delay CMV infection among seropositive patients who develop active infection from reactivation of latent virus. Intravenous acyclovir significantly reduced the probability of CMV infection and disease among seropositive patients in a controlled trial. The new antiviral agents ganciclovir and foscarnet may provide better results, although the marrow toxicity of ganciclovir may limit its utility. For treatment of CMV pneumonia the combination of ganciclovir and CMV immunoglobulin has shown promise in initial trials.     

A fatal case of cytomegalovirus ventriculoencephalitis in a mycosis fungoides patient who received multiple umbilical cord blood cell transplantations

Cytomegalovirus (CMV) infection is latent in the majority of adult humans. The reactivation of CMV causes pneumonia and gastrointestinal disease in severely immunosuppressed patients, who consequently suffer very high mortality due to CMV central nervous system disease. We report here a case involving a 28-year-old female patient with mycosis fungoides who underwent umbilical cord blood transplantation three times and developed CMV ventriculoencephalitis. The patient's CMV viremia was successfully preempted with ganciclovir (GCV) as indicated by undetectable CMV antigenemia; despite this successful treatment, the patient developed CMV ventriculoencephalitis. Foscarnet (FCV) therapy led to a temporary recovery, after which CMV ventriculoencephalitis recurred, and the patient died after receiving combination GCV and FCV therapy. Autopsy samples revealed CMV ventriculoencephalitis, as indicated by numerous inclusion-bearing cells (Owl's eye). It is likely that this patient harbored a GCV-resistant CMV strain; however, it was not possible to obtain nucleic acids suitable for use in assessing this possibility.     

Phenotypes, proliferative responses, and suppressor function of lung lymphocytes during Toxoplasma gondii pneumonia in mice.

Toxoplasma gondii pneumonia has emerged as an important problem in immunocompromised patients, especially those with AIDS. The characteristics of lung lymphocytes, including their phenotypes, proliferative responses, and suppressor function during T. gondii pneumonia were studied. During primary acute T. gondii infection, the numbers of T lymphocytes in the lungs increased even though mice lacked histologic evidence of pneumonia. As mice recovered from acute toxoplasmosis, numbers of lung CD4+ cells and the ratio of CD4+ to CD8+ cells decreased. Subsequently, T. gondii infection reactivated, manifested as pneumonia. During pneumonia, lung T lymphocytes, especially CD8+ cells, increased even more. Lung lymphocytes from mice with T. gondii pneumonia decreased the proliferative responses of splenocytes from T. gondii-immune mice to both concanavalin A and T. gondii lysate antigens in vitro. The striking increase in lung CD8+ cells and suppressor activity appear to be integral to the pathogenesis of T. gondii pneumonia.     

An autopsy case of dermatomyositis associated with interstitial pneumonia probably due to cytomegalovirus infection]

An autopsy case of dermatomyositis (DM) associated with interstitial pneumonia probably due to cytomegalovirus infection is reported. After corticosteroid therapy for 1 month, a 79-year-old man with DM developed acute respiratory failure due to interstitial pneumonia and died in spite of intensive respiratory care. By polymerase chain reaction method (PCR), DNA of cytomegalovirus (CMV) was detected in the bronchoalveolar lavage fluid (BALF). CMV was also detected by the method of conventional virus culture from BALF. These findings suggested that initial infection or reactivation of CMV had occurred in the lungs. The autopsy specimen revealed the findings of interstitial pneumonia compatible with CMV pneumonitis, but without the presence of intranuclear inclusion bodies. Although the present case of interstitial pneumonia should not strictly be diagnosed as definite CMV pneumonitis without the presence of intranuclear inclusion bodies in the lung tissue, initial infection or reactivation of CMV in the lungs may have contributed to the pathogenesis of interstitial pneumonia. In other cases of collagen vascular disease associated with interstitial pneumonia, CMV or other viruses may contribute to the pathogenesis of interstitial pneumonia.     

Atherosclerosis in apoE knockout mice infected with multiple pathogens

Cytomegalovirus (CMV) and Chlamydia pneumoniae (CP) possibly contribute to atherosclerosis. Murine CMV (MCMV) and CP increase lesion size in apoE knockout mice. In this study, apoE knockout mice were infected with MCMV and CP to determine whether infection with multiple pathogens increases lesion size to a greater extent than either pathogen alone and whether infection with MCMV changes serum cytokine levels in a manner that could increase lesion development. One group of mice received MCMV at 2 weeks of age, followed by 2 doses of CP at 6 and 8 weeks of age. Additional groups received only MCMV or CP. Animals were killed at 16 weeks of age to determine lesion area. Infection with MCMV alone, CP alone, and both MCMV and CP increased lesion size 84% (P<.001), 70% (P<.0001), and 45% (P<.01), respectively. The MCMV-induced increase in circulating levels of interferon-gamma may have contributed to this increase.     

Protection from CMV infection in immunodeficient hosts by adoptive transfer of memory B cells

Severe disease associated with cytomegalovirus (CMV) infection is still a major problem in patients who undergo transplantation. Support of the patients' immune defense against the virus is a major goal in transplantation medicine. We have used the murine model of CMV (MCMV) to investigate the potential of a cell-based strategy to support the humoral antiviral immune response. Immunocompetent C57BL/6 mice were infected with MCMV, and memory B cells from the immune animals were adoptively transferred into T-cell- and B-cell-deficient RAG-1(-/-) mice. Following MCMV infection, a virus-specific IgG response developed within 4 to 7 days in the recipient animals. Concomitantly, a significant reduction in viral titers and DNA copies in several organs was observed. In addition, the memory B-cell transfer provided long-term protection from the lethal course of the infection that is invariably seen in immunodeficient animals. Transfer of memory B cells was also effective in protecting from an already ongoing viral infection, indicating a therapeutic potential of virus-specific memory B cells. T cells were not involved in this process. Our data provide evidence that a cell-based strategy to support the humoral immune response can be effective to combat infectious pathogens in severely immunodeficient hosts.     

Acute infection of Toxoplasma gondii and cytomegalovirus reactivation in a pediatric patient receiving liver transplant

A 7-year-old Mexican boy with end-stage cirrhosis underwent liver transplantation and was maintained with cyclosporine and prednisolone. No specific data about Toxoplasma gondii or cytomegalovirus (CMV) infections in the cadaver donor were available. The recipient was seronegative for Toxoplasma, but CMV-IgG positive before transplantation. Ganciclovir was administered for prophylaxis during 3 months, but 5 months later he presented with icterus and increased transaminases. Acute transplant rejection was ruled out by biopsy. A seroconversion for T. gondii IgM and IgG and a small increase in CMV-IgM antibodies were observed, although the CMV-polymerase chain reaction (PCR) was negative. Ganciclovir was re-started, and the patient improved, but 6 months later he relapsed, and chorioretinitis lesions compatible both with T. gondii and CMV infections appeared. Pyrimethamine, sulfadiazine, folinic acid, and ganciclovir were administered. The boy showed favorable clinical improvement and remained stable for 12 months. Then, new retinal CMV lesions appeared in both eyes and the PCR for CMV became positive; therefore, the patient received a new regimen of ganciclovir, and clinically improved. From these data we concluded that the child presented a reactivation of CMV and a primary infection with T. gondii after transplantation.     

Latent infection and the elusive cytomegalovirus

Herpesviruses characteristically establish latent infections in their hosts. In some instances, the tissue sites or even the specific cells that harbor dormant virus have been identified experimentally. However, the sites of cytomegalovirus (CMV) latency have been difficult to define experimentally in humans, even though epidemiologic evidence indicates that undetectable virus can be transferred from donor to recipient in transfused blood or a transplanted organ. Recently, DNA of human CMV has been found in peripheral blood leukocytes and in normal or malignant colonic tissue by hybridization methods. Studies in mice strongly implicate splenic B lymphocytes as cellular reservoirs of latent CMV; however, the virus may also persist in the salivary glands, the prostate, the testes, peripheral blood, and possibly macrophages. Whether latent CMV infection in these tissues is maintained in a single ubiquitous cell type (e.g., lymphocytes or macrophages) or in various cell types is not known. Definition of the sites and mechanisms involved in the maintenance of latent CMV is essential for a thorough understanding of the pathogenesis of CMV infection. Now that trials with live CMV vaccine have begun, further investigations of latent CMV infection in humans and in animal models are clearly needed.     

Characterization of virus-induced interferon-gamma responses in mice previously infected with murine cytomegalovirus

These studies demonstrate that in vitro stimulation of spleen cells from murine cytomegalovirus (MCMV) immune mice with MCMV-infected fibroblasts induces production of interferon (IFN)-gamma. This response is specific to MCMV, is not generalized to heterologous viruses, and also is not H-2 restricted. Both early and late CMV antigens induce IFN-gamma. In in vitro cell depletion and direct cell selection experiments, T lymphocytes were responsible for IFN-gamma production. Although both CD4 and CD8 cells appear to be required to induce the response, the cell subset that releases the IFN-gamma is not yet undefined. In vivo, this IFN-gamma response appears early after acute infection and persists > or =1 year. The response is not seen in T cell-deficient mice. Thus, previous MCMV infection results in a virus-specific IFN-gamma response in spleen cells exposed to MCMV antigens. The pathophysiologic significance of these observations is now under study.