IL-10 plays a crucial role for the protection of experimental cerebral malaria by co-infection with non-lethal malaria parasites

Cerebral malaria is an infrequent but serious complication of Plasmodium falciparum infection in humans. Co-infection with different Plasmodium species is common in endemic areas and the existence of benign malaria parasites, such as Plasmodium vivax, during P. falciparum infection has been considered to reduce the risk of developing pathogenesis. However, it is still unknown how disease severity is reduced in the host during co-infection. In the present study, we investigated the influence of co-infection with non-lethal malaria parasites, Plasmodium berghei (Pb) XAT strain, on the outcome of Pb ANKA strain infection which causes experimental cerebral malaria (ECM) in mice. The co-infection with non-lethal Pb XAT suppressed ECM caused by Pb ANKA infection and prolonged survival of mice. The production of TNF-α and IFN-γ, which had been shown to be involved in development of ECM, was suppressed in co-infected mice early in infection. The suppression of ECM by co-infection with Pb XAT was abrogated in IL-10-deficient mice. IL-10 plays a crucial role in the suppression of ECM by co-infection with non-lethal malaria parasites, probably due to its suppressive effect on the induction of TNF-α and IFN-γ. Co-infection with Pb XAT and Pb ANKA is a useful model for understanding how ECM is suppressed.     

Case Report: No Response to Liposomal Daunorubicin in a Patient with Drug-Resistant HIV-Associated Visceral Leishmaniasis

Visceral leishmaniasis (VL) in patients with HIV co-infection presents a significant therapeutic challenge due to the lessened chance of achieving long-term cure. We report a case of VL in a 60-year-old man with HIV infection who became refractory to anti-leishmania treatment due to multi-drug resistance. In the face of a worsening clinical situation, and with no other options available, he was treated with an experimental regimen of liposomal daunorubicin, which has previously been shown to have in vitro activity against Leishmania donovani and to be effective treatment of VL in animal studies. To our knowledge, he was the first patient with VL and HIV co-infection to have this treatment evaluated. We report on the lack of response to this treatment and possible causes for its failure.     

Visceral leishmaniosis caused by Leishmania (L.) mexicana in a Mexican patient with human immunodeficiency virus infection

A 36 year old male was admitted in December 1997 to hospital with afternoon fever, malaise and hepatosplenomegaly. He also had a dry cough, dyspnoea and anaemia. Pneumonia caused by Pneumocystis carinii and human immunodeficiency virus (HIV) infection were documented. The HIV infection was confirmed in 1997 with 290,000 virus copies. The patient had been in the Mexican State of Chiapas which is known to be endemic for visceral leishmaniosis (VL) and localized cutaneous leishmaniosis (LCL). The visceral symptoms were diagnosed as VL and the causal agent was identified as Leishmania (L. ) mexicana. Identification of Leishmania was carried out by the analysis of amplified DNA with specific primers belonging to the Leishmania subgenus and by dot blot positive hybridisation of these polymerase chain reaction derived products with kDNA from the L. (L. ) mexicana MC strain used as probe. This is the first case in Mexico of VL caused by a species of Leishmania that typically produces a cutaneous disease form.     

An evaluation of the occurrence of pneumocystis infection through examination of pharyngeal and oral swabs using the nested PCR method

A method of collecting pharyngeal and oral swabs from humans and laboratory rats, to be examined later for Pneumocystis infection with simple and nested PCR, was developed. The swabs were obtained from 15 HIV-infected patients, including 5 suffering from PCP, and from 10 immunocompetent children aged 2 to 6 years. Furthermore, the swabs were taken from 30 healthy laboratory rats and 23 animals subjected to immunosuppressive treatment. DNA of Pneumocystis was detected in all the examined rats with nPCR method, but only in 47% of healthy animals when simple PCR was used. Nested PCR examination of swabs collected from human subjects revealed the infection with Pneumocystis in all HIV-infected patients with PCP, and in 8 out of 10 symptomless carriers of Pneumocystis; moreover, the examination was positive in 2 out of 10 immunocompetent children. It was concluded, that noninvasive method of collecting pharyngeal and oral swabs in conjunction with very sensitive method of amplification DNA by nPCR is suitable for measuring the prevalence of Pneumocystis infection in the populations of humans and laboratory animals. The developed method offers a possibility of safe diagnosis of pneumocystosis in patients whose clinical status precludes collection of BAL through bronchoscopy.     

Leishmania infection can hamper immune recovery in virologically suppressed HIV-infected patients

An HIV-infected patient started combination antiretroviral therapy with 13 CD4+ cells/microL. Despite sustained virological suppression over the following four years, the anemia did not resolve, and the CD4+ cell counts always remained below 200/microL until co-infection with Leishmania was diagnosed in October 2006 when the patient started complaining of persistent mild fever and asthenia. Once treatment for leishmaniasis was started with miltefosine, CD4+ cell count rose above 400/microL. A new drop in CD4+ cell count was observed when Leishmania DNA turned out again to be positive, but treatment with liposomal amphotericin-B restored immune recovery.     

Susceptibility of various animals to Pneumocystis carinii infection.

Pneumocystis carinii (Pc) is an important opportunistic pathogen of immune compromised hosts, and is known to infect various animals. The present study observed the infection status of 6 mammals and 3 strains of albino rats with Pc after suppression of their immunity. Methyl-prednisolone was injected once a week and tetracycline was supplied with water for 5 to 21 weeks. Hamsters, guinea pigs, rabbits, dogs, cats and pigs were negative by impression smear, and only the rats were found infected by Pc. All of the three strains of rats, Sprague-Dawley(SD), Wistar(W) and Fisher(F), were infected by Pc but W rats showed heavier degree of infection in earlier period than F or SD rats. The present findings suggest that W rat is the best among the animals used in the present study for production of Pc.     

Pneumocystis infection enhances antibody-mediated resistance to a subsequent influenza infection

In contrast to the detrimental outcomes most often associated with the resolution of coinfections, the model presented here involving a localized Pneumocystis infection of the lung, followed 2 wk later by an influenza virus infection, results in a significant beneficial outcome for the host. In the week following the influenza infection, immunocompetent coinfected animals exhibited an accelerated rate of virus clearance, an accelerated appearance of higher influenza-specific neutralizing Ab titers in their serum and bronchoalveolar lavage fluid (BALF), significantly reduced inflammatory cytokine levels in their BALF, and reduced levels of morbidity relative to animals infected only with influenza virus. The beneficial outcome observed in coinfected immunocompetent animals was dependent on the ongoing resolution of a viable Pneumocystis infection. No differences in viral clearance were detected between coinfected and influenza-only-infected muMT mice or likewise for SCID mice. The accelerated anti-influenza response did not appear to be associated with influenza-specific CD8 T cell-mediated responses or NK cell responses in the lung. Rather, the increased rate of viral clearance was due to the enhancement of the influenza-specific Ab response, which in turn was transiently dependent upon the resolution of the ongoing Pneumocystis infection.     

Type I interferon signaling and B cells maintain hemopoiesis during Pneumocystis infection of the lung

Loss of CD4 T cells is the hallmark of HIV infection. However, type I IFN-producing plasmacytoid dendritic cells may also be lost. This results in susceptibility to an opportunistic infection such as Pneumocystis pneumonia. In addition, regenerative bone marrow failure resulting in pancytopenia is another common problem in advanced stage AIDS. This may be linked to both the failing immune system and recurrent opportunistic infections. We generated lymphocyte-deficient type I IFN receptor-deficient mice (IFrag-/-) to study the effects on Pneumocystis infection of the lung. When IFrag-/- animals were infected with Pneumocystis they died between days 16 and 21 postinfection with minimal pneumonia but severe anemia due to complete bone marrow failure. This included the loss of uncommitted hemopoietic precursor cells. Bone marrow failure was prevented by the reconstitution of IFrag-/- mice with wild-type lymphocytes, especially B cells. T and B cells lacking type I IFN receptor signaling could only partially prevent bone marrow failure in response to Pneumocystis infection. However, the presence of T and B cells lacking type I IFN signaling resulted in compensatory extramedullary hemopoiesis in the liver and spleen. Lymphocyte support of the regenerative capacity of the bone marrow was provided by both type I IFN-dependent and -independent mechanisms that acted synergistically. Our findings point to the requirement of both type I IFNs and lymphocytes in the regenerative capabilities of the hemopoietic system under the pressure of Pneumocystis infection, but not during steady-state hemopoiesis. This may have implications in the management of pancytopenia in AIDS.     

Gastric Infection with Kazachstania heterogenica Influences the Outcome of a Helicobacter suis Infection in Mongolian Gerbils

Background:  The Mongolian gerbil model is often used to investigate the interactions between different gastric Helicobacter species and the gastric tissue. A preliminary screening of a gerbil population intended for use in Helicobacter suis infection studies revealed a natural yeast infection in the stomach of these animals. After identification, we have investigated the effect of the gastric yeast infection on the outcome of an experimental H. suis infection in Mongolian gerbils.
Materials and methods:  Yeast cells were isolated from the stomachs of Mongolian gerbils. Identification was done by Internally Transcribed rRNA Spacer 2 Region PCR fragment length analysis. To investigate a possible pathologic role of this yeast, Mongolian gerbils were infected experimentally with this yeast. Co-infection with the newly isolated H. suis was performed to investigate possible interactions between both micro-organisms.
Results:  Kazachstania heterogenica was found colonizing the stomach of Mongolian gerbils, mainly in the antrum. Few pathologic changes were seen in the stomachs of infected animals. Experimental co-infection of gerbils with this yeast and the newly isolated H. suis showed a significant increase in inflammation in animals infected with both micro-organisms compared to animals infected only with H. suis .
Conclusions:  K. heterogenica colonizes the stomach of Mongolian gerbils in exactly the same regions as gastric Helicobacter species. The uncontrolled presence of this yeast in the gerbil stomach can lead to an overestimation of the inflammation caused by Helicobacter in this animal model.     

Factors influencing Pneumocystis infection in the immunocompromised rat.

A compromised immune system is the primary predisposing condition for Pneumocystis infection. Factors that contribute to this underlying state of immunosuppression are poorly understood. The presence of common rodent viruses and the role of anti-Pneumocystis antibodies on the progression of natural infection in the corticosteroid-treated rat model of Pneumocystis pneumonia were evaluated. The development and intensity of infection were not affected by the presence or absence of antibodies to these viruses or to major Pneumocystis antigens. A significant increase in survival of Pneumocystis-infected viral antibody-positive rats was observed when these rats were housed under barrier conditions.     

Surfactant protein D enhances Pneumocystis infection in immune-suppressed mice

To further determine the role of surfactant protein (SP)-D in the pathogenesis of Pneumocystis pneumonia, a mouse model of transgenic overexpression (OE) of SP-D was studied. These animals produce roughly 30- to 50-fold greater SP-D than their wild-type (WT) counterparts but show no other differences in lung morphology and function. Animals in both the SP-D OE and WT groups were depleted of CD4 lymphocytes with weekly injections of GK1.5 antibody, before Pneumocystis inoculation, and throughout the subsequent infection period. At various time points, mice were killed and analyzed for inflammatory parameters and organism burden. Proinflammatory cytokines in bronchoalveolar lavage fluid were elevated throughout the period of infection, with OE animals exhibiting significantly higher levels of TNF-alpha and macrophage inflammatory protein-2 compared with WT controls. The total number of cells in the lavage fluid was also increased significantly only in the OE group, whereas the cell differential composition demonstrated lymphocyte and eosinophil infiltration in both groups of animals. Significantly, the organism burden was markedly higher in the SP-D OE animals, whereas the WT mice demonstrated little alteration in organism number over the course of infection. These results further indicate that SP-D facilitates the development of Pneumocystis infection and related lung inflammation in an immunosuppressed mouse model.     

A survey of Pneumocystis carinii infection in research mouse colonies in Japan.

To determine the frequency of Pneumocystis carinii infection in mouse colonies maintained for biomedical research in medical colleges or medical faculties in universities in Japan, 409 nu/nu mice were sent to 43 animal facilities from a P. carinii-free colony. The animals were housed for 6 months in groups of 3 to 10 animals per room, and examined for the presence of parasites and infection. Colonies in 10 (24.4%) of 41 facilities were positive for the infection. Of 383 animals in 69 rooms, the organism was detected in 66 (17.2%) animals in 13 (18.8%) rooms. The difference in the proportion of rooms where mice were positive for P. carinii is clearly seen among these three groups; SPF mouse rooms (4 of 38 rooms, 10.5%), SPF mouse rooms with breeding units (5 of 25 rooms, 20.0%) and conventional mouse rooms (4 of 6 rooms, 66.7%). The survey indicates that strict housing arrangements and husbandry techniques are necessary to keep SPF mice free from P. carinii infection.     

The suppression of mitogen responses associated with resistance to experimental autoimmune encephalomyelitis requires adherent and T cells

Resistance to experimental autoimmune encephalomyelitis (EAE) in Hartley guinea pigs has previously been reported to be associated with disease-specific antigen-induced suppression of mitogen responses in vitro. The present studies were initiated to investigate the requirement for different cell populations in this suppression. Intact and adherent-cell-depleted cultures of spleen cells from experimental and control animals were incubated with myelin basic protein (MBP), the major antigen of EAE, with the T-cell mitogen concanavalin A (Con A) alone or with Con A in the presence of MBP. In agreement with previous studies, MBP-induced suppression of the Con A response was observed only in cultures derived from resistant animals. In addition, it was observed that this suppression was abrogated by depletion of adherent cells. When cells from resistant and susceptible animals were mixed, suppression occurred only in the presence of nonadherent cells from resistant guinea pigs. Adherent cells from either resistant or susceptible animals functioned equally well. Cultures of purified E-rosette-forming cells (E+) from resistant animals (i.e., T cells) showed no suppression. Similarly, cells from these same animals which were depleted of E+ cells (i.e., non-T cells) did not demonstrate suppression in vitro. Upon reconstitution of spleen cell populations from resistant guinea pigs by mixing E+ and E- cells, suppression was restored. These experiments show that this model of suppression in vitro requires adherent cells as well as T cells and suggests that antigen-induced suppression of mitogen responses is dependent upon a cell-mediated immunologic mechanism.     

Leishmania (Leishmania) major-infected rhesus macaques (Macaca mulatta) develop varying levels of resistance against homologous re-infections

Seven rhesus macaques were infected intradermally with 10(7) promastigotes of Leishmania (Leishmania) major. All monkeys developed a localized, ulcerative, self-healing nodular skin lesion at the site of inoculation of the parasite. Non-specific chronic inflammation and/or tuberculoid-type granulomatous reaction were the main histopathological manifestations of the disease. Serum Leishmania-specific antibodies (IgG and IgG1) were detected by ELISA in all infected animals; immunoblot analyses indicated that numerous antigens were recognized. A very high degree of variability was observed in the parasite-specific cell-mediated immune responses [as detected by measuring delayed-type hypersensitivity (DTH) reaction, in vitro lymphocyte proliferation, and gamma interferon (IFN-gamma) production] for individuals over time post challenge. From all the recovered monkeys (which showed resolution of the lesions after 11 weeks of infection), 57.2% (4/7) and 28.6% (2/7) animals remained susceptible to secondary and tertiary infections, respectively, but the disease severity was altered (i.e. lesion size was smaller and healed faster than in the primary infection). The remaining monkeys exhibited complete resistance (i.e. no lesion) to each rechallenge. Despite the inability to consistently detect correlates of cell-mediated immunity to Leishmania or correlation between resistance to challenge and DTH, lymphocyte transformation or IFN-gamma production, partial or complete acquired resistance was conferred by experimental infection. This primate model should be useful for measuring vaccine effectiveness against the human disease.     

Pneumocystis: from a doubtful unique entity to a group of highly diversified fungal species

At the end of the 20th century the unique taxonomically enigmatic entity called Pneumocystis carinii was identified as a heterogeneous group of microscopic Fungi, constituted of multiple stenoxenic biological entities largely spread across ecosystems, closely adapted to, and coevolving in parallel with, mammal species. The discoveries and reasoning that led to the current conceptions about the taxonomy of Pneumocystis at the species level are examined here. The present review also focuses on the biological, morphological and phylogenetical features of Pneumocystis jirovecii, Pneumocystis oryctolagi, Pneumocystis murina, P. carinii and Pneumocystis wakefieldiae, the five Pneumocystis species described until now, mainly on the basis of the phylogenetic species concept. Interestingly, Pneumocystis organisms exhibit a successful adaptation enabling them to dwell and replicate in the lungs of both immunocompromised and healthy mammals, which can act as infection reservoirs. The role of healthy carriers in aerial disease transmission is nowadays recognized as a major contribution to Pneumocystis circulation, and Pneumocystis infection of nonimmunosuppressed hosts has emerged as a public health issue. More studies need to be undertaken both on the clinical consequences of the presence of Pneumocystis in healthy carriers and on the intricate Pneumocystis life cycle to better define its epidemiology, to adapt existing therapies to each clinical context and to discover new drug targets.     

Immune response to Leishmania (Leishmania) chagasi infection is reduced in malnourished BALB/c mice

Protein-energy malnutrition and micronutrient deficiencies may down-regulate immune response and increase morbidity and mortality due to infection. In this study, a murine model was used to study the effects of protein, iron and zinc deficiencies on the immune response to Leishmania (Leishmania) chagasi infection. Mice were initially fed a standard diet or with a diet containing 3% casein but deficient in zinc and iron. After malnutrition was established, mice were inoculated with L. chagasi and sacrificed four weeks later in order to evaluate liver and spleen parasite loads and serum biochemical parameters. Significant decreases in liver and spleen weight, an increase in the parasite loads in these organs and decreases in serum protein and glucose concentrations in malnourished animals were observed. Furthermore, the production of interferon-gamma by spleen cells from infected malnourished mice stimulated by Leishmania antigen was significantly lower compared with that in control diet mice. These data suggest that malnutrition alters the immune response to L. chagasi infection in the BALB/c model and, in association with the effects on biochemical and anatomical parameters of the host, favored increases in the parasite loads in the spleens and livers of these animals.     

Dissociation between vasodilation and Leishmania infection-enhancing effects of sand fly saliva and maxadilan.

In this study, the ability of maxadilan and Lutzomyia longipalpis salivary gland lysate to enhance the infection of CBA mice by Leishmania major and of BALB/c mice by L. braziliensis was tested. No difference was observed between sizes of lesion in CBA mice infected with L. major and treated or not with salivary gland lysate or maxadilan, although they were injected in concentrations that induced cutaneous vasodilation. Although parasites were more frequently observed in foot pads and spleens of animals treated with maxadilan than in the animals treated with salivary gland lysate or saline, the differences were small and not statistically significant. The lesions in BALB/c mice infected with L. braziliensis and treated with maxadilan were slightly larger than in animals that received Leishmania alone. Such differences disappeared 14 weeks after infection, and were statistically significant only in one of two experiments.