Persistent diarrhoea in Zairian AIDS patients: an endoscopic and histological study

Prevalence of enteric viruses among hospital patients with AIDS in Kinshasa, Zaire

Diarrhoea is the most common manifestation of acquired immunodeficiency syndrome (AIDS) in Africa. Numerous parasitic or bacterial agents have been implicated, but a pathogen-specific aetiology has not been found. Enteric viruses (i.e., rotavirus, small round structured viruses, coronavirus, and adenovirus) were detected by enzyme-linked immunosorbent assay or electron microscopy in faecal specimens of 17% of 198 consecutive adult admissions to a general medical ward of an urban hospital in Kinshasa, Zaire. Overall, 57% of patients were seropositive for infection with human immunodeficiency virus (HIV) 1; of these, 50% were classified as World Health Organization AIDS stage IV. The prevalence of enteric viruses in stool specimens did not differ significantly between patients with and without HIV infection, and was not associated with acute or chronic diarrhoea, or constitutional symptoms. However, a trend (P = 0.14) towards greater frequency of virus in stools from patients in the lower 3 quintiles of the CD4/CD8 T cell ratio was seen. This trend approached statistical significance (P = 0.07) with stratification by HIV infection. Although we found no evidence in this population to support a major pathogenic role for these viruses alone in the enteropathy of AIDS, increased viral shedding was weakly associated with immunodeficiency.

Dysregulation of strongyloidiasis: a new hypothesis

Few other human parasites are associated with such a diverse spectrum of clinical manifestations as Strongyloides stercoralis, yet the basic biological behavior of this unusually versatile worm, particularly with respect to its ability to cause severe disseminated disease in certain hosts, is poorly understood. The current uncritical acceptance of the theory that cell-mediated immunity controls autoinfection has stifled research in other directions. After reviewing what is and is not known about the parasite's behavior in its host, this article explores some of the mechanisms that could be involved in the regulation of the parasite population. Taking the provocative viewpoint that the parasite, not the host, is mainly responsible for the maintenance of a balanced relationship between the two, I propose a new theory that corticosteroids may act on the intraintestinal larvae as molting hormones and directly promote the development of disseminated disease.

Intestinal parasites in Zambian patients with AIDS

Previous studies have found a high prevalence of Isospora belli and Cryptosporidium parvum infections in African acquired immune deficiency syndrome (AIDS) patients with chronic diarrhoea. We aimed to determine the prevalence of gastrointestinal parasite in AIDS patients in hospital, not only those with diarrhoea, and to compare them with the general community. Clinically diagnosed AIDS patients in a Zambian teaching hospital were interviewed and examined, and stool specimens were studied for parasite infection. A control group was recruited from adults in a township near Lusaka. Of 90 AIDS patients (58% male), 50 (56%) had chronic diarrhoea and 9 (10%) had diarrhoea of shorter duration. In the control group (105 adults; 85% female), only one complained of diarrhoea. A variety of intestinal protozoa and helminths was found in 57% of AIDS patients and 88% of the community members. Isosporiasis was detected in 7, and cryptosporidiosis in 2, AIDS patients, all with diarrhoea, but not in any control. Strongyloides was found in 2 AIDS patients with diarrhoea and one community resident. Hospital patients with AIDS had fewer Entamoeba coli and E. histolytica infections, probably because of previous chemotherapy. We conclude that AIDS predisposes to isosporiasis and cryptosporidiosis, but not to infection with extracellular intestinal parasites, such as Entamoeba species, Blastocystis, Chilomastix, Endolimax, Ascaris and Necator.

A microsporidian previously undescribed in humans, infecting enterocytes and macrophages, and associated with diarrhea in an acquired immunodeficiency syndrome patient

To date, the only microsporidian that has been associated with diarrhea and weight loss in acquired immunodeficiency syndrome patients is the newly identified Enterocytozoon bieneusi. A second species is now described that was associated with intestinal symptoms in a 32-year-old, human immunodeficiency virus- seropositive, Native American male homosexual. Stool studies and routine light microscopy of multiple small intestinal biopsies that showed atrophy with acute and chronic inflammation were without apparent pathogens. Light microscopy of semi-thin plastic sections, cytochemical stains of paraffin sections, and ultrastructural studies revealed extensive microsporidial infection of enterocytes and submucosal macrophages. No other pathogens were identified. Unlike E bieneusi, this microsporidian appeared to develop within septated parasitophorous vacuoles, and lacked polar disks and clear clefts. It most closely resembled, but was distinguishable from, members of the genus Encephalitozoon. Awareness of the microsporidia as potential opportunists in acquired immunodeficiency syndrome patients is increasing the incidence of identification of these organisms.

Cryptosporidiosis in the acquired immunodeficiency syndrome: a study of 15 autopsy cases

The pathologic changes associated with human cryptosporidiosis have not been well characterized. In this report, 15 cases of cryptosporidiosis in acquired immunodeficiency syndrome patients are described. Organisms were found in autopsy tissue specimens in 13 cases, and only in antemortem stool samples in two. Gastrointestinal/hepatobiliary distribution of organisms was as follows: small intestine (13 cases), extrahepatic bile ducts (eight), intrahepatic bile ducts (seven), large intestine (six), pancreas (five), stomach (three), and esophagus (one). At all sites, infection was usually associated with nonspecific reactive epithelial changes, architectural abnormalities such as villous flattening in the small intestine, and interstitial edema with mixed inflammatory cell infiltrates. Presence of organisms and associated mucosal injury were patchy and of variable severity in the intestine. In the biliary tract, injury was commonly diffuse and severe. Pancreatic duct injury was generally mild and often limited to hyperplastic squamous metaplasia. In late-stage acquired immunodeficiency syndrome patients with cryptosporidiosis, widespread infection in the gastrointestinal and biliary systems by this coccidian was more common and severe than previously suggested. Although the mechanisms have yet to be determined, infection usually is accompanied by pathologic changes that may be causally related to pathophysiologic abnormalities, such as diarrhea and malabsorption, and may account for other clinical manifestations of pancreatitis, cholangitis, and obstructive cholestasis.

Cryptosporidiosis

Before 1982, only eight case reports of human cryptosporidiosis and fewer than 30 papers on Cryptosporidium spp. appeared in the biomedical literature. At that time, cryptosporidiosis was thought to be an infrequent infection in animals and rarely an opportunistic infection in humans. The concept of Cryptosporidium spp. as pathogens has changed dramatically within the past 8 years because of improved diagnostic techniques, increased awareness within the biomedical community, and the development of basic research programs in numerous laboratories. Presently, greater than 1,000 publications including over 400 case reports in the biomedical literature address Cryptosporidium spp. and cryptosporidiosis. Cryptosporidium parvum is now thought to be one of the three most common enteropathogens causing diarrheal illness in humans worldwide, especially in developing countries. It is likely that cryptosporidiosis was previously included in the 25 to 35% of diarrheal illness with unknown etiology. Because of the severity and length of diarrheal illness and because no effective therapy has been identified, cryptosporidiosis is one of the most ominous infections associated with AIDS. The role of C. parvum as an enteropathogen is well established; documentation of its role as a cause of hepatobiliary and respiratory diseases is now appearing in the literature. Our present understanding of the natural history, epidemiology, biology, and immunology of Cryptosporidium spp. as well as the clinical features, pathogenicity, and treatment of cryptosporidiosis are reviewed here.

Characterization of 20 Entamoeba histolytica strains isolated from patients with HIV infection

Twenty Entamoeba histolytica strains from patients with HIV-1 infection were isolated and compared with E. histolytica strains from patients without HIV infection. The isoenzyme pattern of the hexokinase as well as the hybridization with known DNA-probes were used as markers for pathogenicity. According to these markers, all 20 strains could be regarded as being nonpathogenic. Direct measurements of the virulence were carried out: destruction of monolayer tissue culture cells, capacity of phagocytosis and the ability to induce liver abscesses in the hamster. The virulence of strains from HIV patients was comparable to that of E. histolytica strains which had been isolated from HIV-negative asymptomatic carriers. In agreement with this, none of the HIV-positive patients showed symptoms of an invasive amebiasis. By PRC, no HIV-1 proviral DNA could be evidenced in the E. histolytica strains which had been isolated from HIV patients.

Opportunistic protozoan infections in human immunodeficiency virus disease: review highlighting diagnostic and therapeutic aspects

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Male homosexuality, HIV infection and colorectal surgery

The sexual practices of male homosexuals may lead to the development of a wide variety of colorectal and perianal diseases. This review describes the pathogenesis of these conditions, their management, and the influence of HIV infection on these conditions.

Intestinal microsporidiosis as a cause of diarrhea in human immunodeficiency virus-infected patients: a report of 20 cases

Chronic diarrhea accompanied by weight loss is a common and often debilitating problem associated with human immunodeficiency virus (HIV) infection. Enterocytozoon bieneusi, a newly identified species of the phylum of protozoa, Microspora, has been reported associated with chronic diarrhea and wasting in 11 acquired immunodeficiency syndrome (AIDS) patients in the United States, Europe, and Africa. Diagnosis has been based solely on the ultrastructural identification of this small, intracellular parasite in bowel biopsies. Seventy-one small bowel biopsies from 67 homosexual AIDS and AIDS-related complex patients with chronic diarrhea and with no pathogens identified by light microscopy on paraffin sections, were embedded in plastic and studied by light and transmission electron microscopy. Enterocytozoon bieneusi microsporidiosis was diagnosed by electron microscopy in 20 (22 biopsies) of the patients. More jejunal biopsies (16 of 36) were positive than duodenal biopsies (six of 35). Parasites and spores were clearly visible at the light microscopic level in the semi-thin plastic sections from 17 and 21 of the biopsies, respectively. In retrospect, parasites could be identified by light microscopy in standard hematoxylin and eosin-stained paraffin sections. Infection was confined to enterocytes covering the villi, especially the tips, and was associated with villous atrophy and cell degeneration, necrosis, and sloughing. Release of spores into the bowel lumen was evident. Colorectal biopsies from two of the patients with small bowel microsporidiosis were negative for microsporidia. Enterocytozoon bieneusi infection of the small bowel may be an important cause of diarrhea in HIV-infected persons.

Quantitative histological study of enteropathy associated with HIV infection

A quantitative histological study was performed on small intestinal biopsies from eight ambulatory patients with HIV infection (AIDS/AIDS-related complex, ARC) and compared with those from 16 normal subjects. Enteropathy was assessed by measurement of villus area, crypt length and mitotic count, as well as duodenal counts of intraepithelial lymphocytes, mucosal mast cells and goblet cells. Enteropathy in subjects with AIDS/ARC was shown by reduced mean villus area of 0.363 (SD 0.081) compared with 0.500 (SD 0.064) mm2 in control subjects (p less than 0.0001), while intestinal crypts were of similar length with 239 (SD 36) compared with 225 (SD 28 microns, but mitotic count was increased to 3.8 (SD 1.2) compared with 2.4 (SD 0.8) (p = 0.01) in the same control subjects. These results indicate villous atrophy with impaired crypt hyperplasia. Duodenal cell counts showed similar numbers of mucosal mast cells, intraepithelial lymphocytes and goblet cells in AIDS/ARC patients and fifteen control subjects.

Infected cells and immune cells in the gastrointestinal tract of AIDS patients. An immunohistochemical study of 127 cases

Human immunodeficiency virus (HIV) proteins were detected by immunohistochemistry in the duodenal and rectal mucosa of 30% of 127 AIDS patients studied. HIV-infected cells were present in the lamina propria in 95% of the positive biopsies. They were immune cells, either isolated lymphocytes and macrophages (1-4 per positive biopsy) or dendritic reticulum cells forming a network in the germinal centres of mucosal lymphoid follicles. HIV proteins were not found in the duodenal epithelium or in the superficial rectal epithelium. In two cases (5% of the positive biopsies), they were found in rectal glands: the HIV-infected cells could be either epithelial cells or immune cells. This study confirms that the gut can be a target organ for HIV and that HIV is mainly carried by gut immune cells. The phenotypic study of lymphoid populations and macrophages in the gut mucosa of AIDS patients showed an inverse CD4/CD8 ratio in the lamina propria, compared with normal controls. This was independent of the presence of HIV proteins and is probably responsible for the appearance of opportunistic infections in the mucosa. An increase in activated macrophages was also noted in the mucosa of AIDS patients.

Opportunistic infections in AIDS in developed and developing countries

The acquired immune deficiency syndrome (AIDS) is fundamentally the same disease in all parts of the world, but the prevalence of microorganisms in an environment governs the patterns of disease arising from reactivated latent infections, invading pathogens and opportunistic infections. AIDS in Africa has certain characteristic presentations. Enteropathic AIDS is most common: Cryptosporidium and Isospora belli are identified in up to 60% of patients, but it is uncertain whether they are the causes of diarrhoea. Pneumocystis carinii pneumonia is rare. Tuberculosis, both pulmonary and extrapulmonary, is the supreme complicating infection. Herpes zoster is frequently the first clinical presentation, and has a 95% positive predictive value for HIV positivity. Measles may be more frequent in infants born to HIV-infected mothers, and appears to be worse in HIV-infected children. There is accelerated progress of both diseases in patients infected by HIV and Mycobacterium leprae. Salmonellosis is frequent. There is no direct interaction between malaria and HIV, but, by being a potent cause of anaemia, malaria enhances transmission of HIV to children through blood transfusion. HIV-positive subjects are liable to new or reactivated visceral leishmaniasis with dissemination to unusual sites. Cerebral toxoplasmosis is common. There are no apparent interactions between HIV and helminths, although there is one report of hyperinfection with Strongyloides stercoralis. Cryptococcal meningitis has high frequency. Infections with Histoplasma encapsulatum are common in tropical America, but there has been no increase of frequency of H. duboisii in Africa since the advent of AIDS.

Missing infections in AIDS

In north America and Europe, the opportunistic infections from which patients with acquired immune deficiency syndrome (AIDS) frequently suffer are Pneumocystis carinii pneumonia and Mycobacterium avium-intracellulare: in central Africa these infections are uncommon or non-existent. Serious infections with Entamoeba histolytica and Strongyloides stercoralis would be expected to occur in AIDS patients: they do not. Falciparum malaria might be expected to interact with HIV infection: it does not. The epidemiology and pathophysiology of these infections are discussed with respect to HIV co-infection.

Cytomegalovirus infection in gastrointestinal tracts of patients infected with HIV-1 or AIDS

All gastrointestinal tract biopsy specimens from 190 patients positive for HIV-1 or with AIDS were reviewed to assess the prevalence of cytomegalovirus (CMV) infection, morphology of infected cells, and the associated histopathological features. Eighteen patients (10 (7.7%) of 129 HIV antibody positive and eight (13.1%) of 61 with AIDS) had CMV identified in 35 biopsy specimens from the following sites: oesophagus (n = 3); stomach (n = 6); small intestine (n = 4); colorectum (n = 18) and perianal area (n = 4). Eleven patients had CMV alone as the potential cause of symptoms and in seven there were coexistent pathogens or Kaposi's sarcoma. The appearance and type of infected cells at different sites was highly variable. Immunocytochemical techniques and electron microscopic examination were performed to confirm the presence of CMV antigen and CMV virus particles and to exclude the possibility of an adenovirus producing similar cytopathic changes. It is important to recognise the different morphological forms of infected cells, and the use of immunocytochemical techniques is recommended in patients at risk for CMV or in whom CMV infection is suspected.