Renal Encephalitozoon (Septata) intestinalis infection in a patient with AIDS. Post-mortem identification by means of transmission electron microscopy and PCR

Encephalitozoon spp. as a potential human pathogen

Encephalitzoon spp. are microsporidia, and intracellular opportunistic pathogens. The hosts of these pathogens include vertebrates, invertebrates, and certain protozoa. In people microsporidia may be opportunistic pathogens for immunocompromised patients (with AIDS or after organ transplantation). Infection with these microorganisms was also described in persons with diarrhea and corneal diseases.

The species causing rare infections in humans, Encephalitozooncuniculi, had previously been described from animal hosts. However, several new microsporidial species, including E. intestinalis and E. hellem, have been discovered in humans, raising the question of their natural origin. Vertebrate animals are now identified as hosts for all three microsporidial species infecting humans, implying a zoonotic nature of these microorganisms. Molecular studies have identified phenotypic and/or genetic variability within these species, indicating that they are not uniform, and have allowed the question of their zoonotic potential to be addressed. The focus of this review is to present the zoonotic potential of E. intestinalis, E. cuniculi, and E. hellem.

Chronic Infections in Mammals Due to Microsporidia

Microsporidia are pathogenic organism related to fungi. They cause infections in a wide variety of mammals as well as in avian, amphibian, and reptilian hosts. Many microsporidia species play an important role in the development of serious diseases that have significant implications in human and veterinary medicine. While microsporidia were originally considered to be opportunistic pathogens in humans, it is now understood that infections also occur in immune competent humans. Encephalitozoon cuniculi, Encephalitozoon intestinalis, and Enterocytozoon bieneusi are primarily mammalian pathogens. However, many other species of microsporidia that have some other primary host that is not a mammal have been reported to cause sporadic mammalian infections. Experimental models and observations in natural infections have demonstrated that microsporidia can cause a latent infection in mammalian hosts. This chapter reviews the published studies on mammalian microsporidiosis and the data on chronic infections due to these enigmatic pathogens.

Incidence Rate and Time to Occurrence of Renal Impairment and Chronic Kidney Disease among Thai HIV-infected Adults with Tenofovir Disoproxil Fumarate Use

Background:

Tenofovir disoproxil fumarate (TDF) is a major antiretroviral therapy for Thai human immunodeficiency virus (HIV) infected adults. TDF is associated with a decrease in renal function. There is limited data about the use of TDF with the incidence and time to renal impairment and chronic kidney disease (CKD) in Thai HIV-infected adults.

Objectives:

To study the association of TDF with the incidence rate and duration of renal impairment and CKD in Thai patients.

Methods:

A retrospective cohort study in Thai naïve HIV-infected adults was conducted to compare the incidence rate and time to renal impairment and CKD in TDF and non-TDF groups. The incidence rate was analyzed by person-time. Time to renal impairment and CKD were analyzed by Kaplan-Meier curves and log-rank tests.

Results:

A total of 1,400 patients were enrolled. The incidence rates of renal impairment in TDF and non-TDF groups were 27.66/1,000 and 5.54/1,000 person-years. The rate ratio was 4.99 (95% confidence interval [CI] 2.66–9.35). The incidence rates of CKD in both groups were not significantly different. Themean difference of eGFR between the TDF and non-TDF groups was 1.92 ml/min/1.73 m2 (p = 0.022). Time to onset of renal impairment between the TDF and non-TDF groups was found to differ by approximately 20 months.

Conclusion:

The incidence rate of renal impairment was about five times higher in the TDF group. A rapid decline of eGFR occurred in the first 2–3 years of treatment. Therefore, the renal function of HIV-infected patients should be monitored so that the severity of renal impairment could be evaluated and CKD could be prevented.

Microsporidia as emerging pathogens and the implication for public health: a 10-year study on HIV-positive and -negative patients

Despite recent advances in the understanding and diagnosis of emerging microsporidian pathogens, more research is necessary to elucidate their complex epidemiology. In fact, studies that reflect true human-infecting microsporidian prevalence are still inadequate. The present 10-year study was undertaken to examine the occurrence of Microsporidia in 1989 stools, 69 urine and 200 pulmonary specimens from HIV-positive and HIV-negative patients using PCR and DNA sequencing. In stools, 12.0% were Microsporidia-positive. Prevalences of 13.9% and 8.5% were observed for HIV+ and HIV- samples, respectively. The percentage of children that were Microsporidia-positive (18.8%) was significantly higher than that of adults (10.2%). In stools, Enterocytozoon bieneusi (6.3%) and Vittaforma-like parasites (6.8%) were identified. Based on the internal transcribed spacer (ITS) region of E. bieneusi, Type IV (37.5%), Peru 6 (29.2%), D (12.5%), A (8.3%), C (6.3%) and PtEb II (6.3%) genotypes were identified. Microsporidia were detected in 1.5% and 1.0% of urine and pulmonary specimens, respectively. Encephalitozoonintestinalis was detected in urine. In pulmonary specimens, Encephalitozoon cuniculi and Vittaforma-like parasites were identified. An immunosuppressive condition and youth (children) appear to be risk factors for microsporidian infection. Microsporidia seems to have an important impact on public health in Portugal, highlighting the need to implement routine diagnosis.

Importance of nonenteric protozoan infections in immunocompromised people

There are many neglected nonenteric protozoa able to cause serious morbidity and mortality in humans, particularly in the developing world. Diseases caused by certain protozoa are often more severe in the presence of HIV. While information regarding neglected tropical diseases caused by trypanosomatids and Plasmodium is abundant, these protozoa are often not a first consideration in Western countries where they are not endemic. As such, diagnostics may not be available in these regions. Due to global travel and immigration, this has become an increasing problem. Inversely, in certain parts of the world (particularly sub-Saharan Africa), the HIV problem is so severe that diseases like microsporidiosis and toxoplasmosis are common. In Western countries, due to the availability of highly active antiretroviral therapy (HAART), these diseases are infrequently encountered. While free-living amoebae are rarely encountered in a clinical setting, when infections do occur, they are often fatal. Rapid diagnosis and treatment are essential to the survival of patients infected with these organisms. This paper reviews information on the diagnosis and treatment of nonenteric protozoal diseases in immunocompromised people, with a focus on patients infected with HIV. The nonenteric microsporidia, some trypanosomatids, Toxoplasma spp., Neospora spp., some free-living amoebae, Plasmodium spp., and Babesia spp. are discussed.

HIV-1 infection and the kidney: an evolving challenge in HIV medicine

With the advent of highly active antiretroviral therapy (HAART), the incidence of opportunistic infections has declined substantially, and cardiovascular, liver, and renal diseases have emerged as major causes of morbidity and mortality in individuals with human immunodeficiency virus (HIV). Acute renal failure is common in HIV-infected patients and is associated with acute infection and medication-related nephrotoxicity. HIV-associated nephropathy is the most common cause of chronic kidney disease in HIV-positive African American populations and may respond to HAART. Other important HIV-associated renal diseases include HIV immune complex kidney diseases and thrombotic microangiopathy. The increasing importance of non-HIV-associated diseases, such as diabetes mellitus, hypertension, and vascular disease, to the burden of chronic kidney disease has been recognized, focusing attention on prevention and control of these diseases in HIV-positive individuals. HIV-positive individuals who experience progression to end-stage renal disease and who have undetectable HIV-1 viral loads while receiving HAART should be evaluated for renal transplant. Emerging evidence suggests that HIV-positive individuals may have graft and patient survival comparable to HIV-negative individuals. Several studies suggest that HIV-1 can potentially infect renal cells, and HIV transgenic mice have clarified the roles of a number of HIV proteins in the pathogenesis of HIV-associated renal disease. Host factors may modify disease expression at the level of cytokine networks and the renal microvasculature and contribute to the pathogenic effects of HIV-1 infection on the kidney.

Induction of host chemotactic response by Encephalitozoon spp

Microsporidians are a group of emerging pathogens typically associated with chronic diarrhea in immunocompromised individuals. The number of reports of infections with these organisms and the disseminated pathology is growing as diagnostic tools become more readily available. However, little is known about the innate immune response induced by and generated against these parasites. Using a coculture chemotaxis system, primary human macrophages were infected with Encephalitozoon cuniculi or Encephalitozoon intestinalis, and the recruitment of naïve monocytes was monitored. Encephalitozoon spp. induced an average threefold increase in migration of naïve cells 48 h postinfection, which corresponded to optimal infection of monocyte-derived-macrophages. A limited microarray analysis of infected macrophages revealed several chemokines involved in the inflammatory responses whose expression was upregulated, including CCL1, CCL2, CCL3, CCL4, CCL7, CCL15, CCL20, CXCL1, CXCL2, CXCL3, CXCL5, and CXCL8. The levels of 6 of 11 chemokines also present in the microarray were confirmed to be elevated by protein profiling. Kinetic studies confirmed that secreted CCL2, CCL3, and CCL4 were expressed as early as 6 h postinfection, with peak expression at 12 to 24 h and expression remaining until 48 h postinfection. Neutralization of these chemokines, specifically CCL4, significantly reduced the number of migrating cells in vitro, indicating their role in the induction of monocyte migration. This mechanism of recruitment not only supports the evidence that in vivo cellular infiltration occurs but also provides new hosts for the parasites, which escape macrophages by rupturing the host cell. To our knowledge, this is the first documentation that chemokine production is induced by microsporidian infections in human macrophages.

Zoonotic potential of the microsporidia

Microsporidia are long-known parasitic organisms of almost every animal group, including invertebrates and vertebrates. Microsporidia emerged as important opportunistic pathogens in humans when AIDS became pandemic and, more recently, have also increasingly been detected in otherwise immunocompromised patients, including organ transplant recipients, and in immunocompetent persons with corneal infection or diarrhea. Two species causing rare infections in humans, Encephalitozoon cuniculi and Brachiola vesicularum, had previously been described from animal hosts (vertebrates and insects, respectively). However, several new microsporidial species, including Enterocytozoon bieneusi, the most prevalent human microsporidian causing human immunodeficiency virus-associated diarrhea, have been discovered in humans, raising the question of their natural origin. Vertebrate hosts are now identified for all four major microsporidial species infecting humans (E. bieneusi and the three Encephalitozoon spp.), implying a zoonotic nature of these parasites. Molecular studies have identified phenotypic and/or genetic variability within these species, indicating that they are not uniform, and have allowed the question of their zoonotic potential to be addressed. The focus of this review is the zoonotic potential of the various microsporidia and a brief update on other microsporidia which have no known host or an invertebrate host and which cause rare infections in humans.

Disseminated microsporidiosis caused by Encephalitozoon cuniculi III (dog type) in an Italian AIDS patient: a retrospective study

We report a case of disseminated microsporidiosis in an Italian woman with AIDS. This study was done retrospectively using formalin-fixed, paraffin-embedded tissue specimens obtained at autopsy. Microsporidia spores were found in the necrotic lesions of the liver, kidney, and adrenal gland and in ovary, brain, heart, spleen, lung, and lymph nodes. The infecting agent was identified as belonging to the genus Encephalitozoon based on transmission electron microscopy and indirect immunofluorescence. Additional molecular studies, including sequence of the rDNA internal transcribed spacer region, identified the agent as E. cuniculi, Genotype III. We believe that this is the first report of a human case of disseminated microsporidial infection involving the ovary.