Enteric coccidiosis among patients with the acquired immunodeficiency syndrome

Cystoisospora belli infections in humans: the past 100 years

Cystoisospora belli is a coccidian parasite of humans, with a direct fecal-oral transmission cycle. It is globally distributed, but mainly found in tropical and subtropical areas. Many cases of C. belli infections have been reported in patients with HIV, and in patients undergoing immunosuppressive therapy for organ transplants or those treated for tumours worldwide. Unsporulated or partially sporulated oocysts of C. belli are excreted in feces. When sporulated oocysts in contaminated water or food are ingested, asexual and sexual stages of C. belli are confined to the epithelium of intestines, bile ducts and gallbladder. Monozoic tissue cysts are present in extra-intestinal organs (lamina propria of the small and large intestine, lymph nodes, spleen, and liver) of immunosuppressed humans. However, a paratenic host has not been demonstrated. Cystoisospora belli infections can be persistent, lasting for months, and relapses are common; the mechanism of relapse is unknown. Recently, the endogenous stages of C. belli were re-examined and attention was drawn to cases of misidentification of non-protozoal structures in the gallbladder of patients as C. belli. Here, we review all aspects of the biology of C. belli, including morphology, endogenous stages, prevalence, epidemiology, symptoms, diagnosis and control.

The evolution of respiratory Cryptosporidiosis: evidence for transmission by inhalation

The protozoan parasite Cryptosporidium infects all major vertebrate groups and causes significant diarrhea in humans, with a spectrum of diseases ranging from asymptomatic to life-threatening. Children and immunodeficient individuals are disproportionately affected, especially in developing countries, where cryptosporidiosis contributes substantially to morbidity and mortality in preschool-age children. Despite the enormous disease burden from cryptosporidiosis, no antiprotozoal agent or vaccine exists for effective treatment or prevention. Cryptosporidiosis involving the respiratory tract has been described for avian species and mammals, including immunocompromised humans. Recent evidence indicates that respiratory cryptosporidiosis may occur commonly in immunocompetent children with cryptosporidial diarrhea and unexplained cough. Findings from animal models, human case reports, and a few epidemiological studies suggest that Cryptosporidium may be transmitted via respiratory secretions, in addition to the more recognized fecal-oral route. It is postulated that transmission of Cryptosporidium oocysts may occur by inhalation of aerosolized droplets or by contact with fomites contaminated by coughing. Delineating the role of the respiratory tract in disease transmission may provide necessary evidence to establish further guidelines for prevention of cryptosporidiosis.

Seasonal profile and level of CD4+ lymphocytes in the occurrence of cryptosporidiosis and cystoisosporidiosis in HIV/AIDS patients in the Triângulo Mineiro region, Brazil

Patients with AIDS are particularly susceptible to infection with intestinal coccidia. In this study the prevalence of infections with Cryptosporidium sp and Cystoisospora belli were evaluated among HIV/AIDS patients in the Triângulo Mineiro region, Brazil. Between July 1993 and June 2003 faecal samples from 359 patients were collected and stained by a modified Ziehl-Neelsen method, resulting in 19.7% of positivity for coccidian (8.6% with Cryptosporidium sp, 10.3% with Cystoisospora belli and 0.8% with both coccidian). Patients with diarrhoea and T CD4+ lymphocyte levels < 200 cells/mm3 presented higher frequency of these protozoans, demonstrating the opportunistic profile of these infections and its relationship with the immunological status of the individual. It was not possible to determine the influence of HAART, since only 8.5% of the patients positive for coccidian received this therapy regularly. Parasitism by Cryptosporidium sp was more frequent between December and February and thus was characterised by a seasonal pattern of infection, which was not observed with Cystoisospora belli.

Diarrheal diseases associated with HIV infection

Diarrhea is a major complication of HIV infection and adversely impacts health care costs, quality of life, and even survival of patients. There is a wide variety of potential causes of diarrhea in HIV-infected patients, and the number of pathogens found continues to increase with time. In addition, there is some controversy concerning the role of some organisms in the pathogenesis of diarrhea and the appropriate diagnostic evaluation of affected patients. This article reviews our current understanding of these pathogens and some of the diagnostic and therapeutic approaches for diarrhea associated with HIV infection.

Biology of Isospora spp. from humans, nonhuman primates, and domestic animals

Coccidial parasites of the genus Isospora cause intestinal disease in several mammalian host species. These protozoal parasites have asexual and sexual stages within intestinal cells of their hosts and produce an environmentally resistant cyst stage, the oocyst. Infections are acquired by the ingestion of infective (sporulated) oocysts in contaminated food or water. Some species of mammalian Isospora have evolved the ability to use paratenic (transport) hosts. In these cases, infections can be acquired by ingestion of an infected paratenic host. Human intestinal isosporiasis is caused by Isospora belli. Symptoms of I. belli infection in immunocompetent patients include diarrhea, steatorrhea, headache, fever, malaise, abdominal pain, vomiting, dehydration, and weight loss, blood is not usually present in the feces. The disease is often chronic, with parasites present in the feces or biopsy specimens for several months to years. Recurrences are common, Symptoms are more severe in AIDS patients, with the diarrhea being more watery. Extraintestinal stages of I. belli have been observed in AIDS patients but not immunocompetent patients. Treatment of I. belli infection with trimethoprim-sulfamethoxazole usually results in a rapid clinical response. Maintenance treatment with trimethoprim-sulfamethoxazole is needed because relapses often occur once treatment is stopped.

Persistent diarrhea caused by Isospora belli: therapeutic response to pyrimethamine and sulfadiazine

A 54-year-old human immunodeficiency virus (HIV)-positive homosexual man developed overwhelming watery diarrhea and marked weight loss over a 3-week period. Although Entamoeba histolytica and other nonpathogenic enteric protozoa were observed along with Isospora belli in this patient's stool specimens, they were promptly eradicated after metronidazole (flagyl) treatment. The presence of I. belli oocysts in various stages of development in the stool and clinical symptoms related to Isospora infection persisted for 10 more months despite treatment with combined chemotherapeutic agents. Clinical and parasitiological resolution was ultimately achieved through an 8-week course of pyrimethamine and sulfadiazine.

Causes of chronic diarrhea in patients with AIDS in Thailand: a prospective clinical and microbiological study

A prospective study was designed to investigate the causes of chronic diarrhea in AIDS patients in Thailand. Forty-five patients from Bamrasnaradura Infectious Diseases Hospital were enrolled. Extensive investigations included multiple stool examinations for ova and parasites, using the stool formalin-ether concentration method, stool culture, stool acid-fast bacilli (AFB) stain, stool modified AFB stain, esophagogastroduoscopy with duodenal aspirate and biopsy, and colonoscopy with biopsy. Biopsied specimens were examined with H&E, Giemsa, Gram, Periodic acid Schiff, and AFB stains. Definitive causes were found in 29 patients (64.4%). Of these 29, 7 patients were found to habor more than 1 pathogen (15.5%). The most commonly found enteric pathogen was Cryptosporidium parvum (20.0%). Less frequently found pathogens were Mycobacterium tuberculosis (17.8%), Salmonella spp. (15.5%), Cytomegalovirus (11.1%), Mycobacterium avium intracellulare (6.6%), Strongyloides stercoralis (4.4%), Giardia lamblia (4.4%), Cryptococcus neoformans (2.2%), Histoplasma capsulatum (2.2%), Campylobacter jejun (2.2%), and Cyclospora cayetanensis (2.2%). Salmonella spp., Mycobacterium tuberculosis, and Mycobacterium avium intracellulare infections were shown to be more common in Thailand than in African countries.

The relevance of laboratory diagnosis of human cryptosporidiosis and other coccidia

Human infection by Cryptosporidium spp and other coccidia are due to opportunist non-host specific microorganisms. In HIV seropositive patients, the gastrointestinal symptoms accompanying such infections may be serious and prolonged and may include nausea, low-grade fever, abdominal cramps, anorexia and watery diarrhoea. We studied 188 stool samples from 111 patients (84 men and 27 women) with diarrhoea. A modified Ziehl-Nielsen technique for the detection of Cryptosporidium spp and Isospora belli was employed. The mean age of the patients was 31 years. Cryptosporidium spp was seen in 18% (n = 20) of the patients, 90% (n = 18) of whom were HIV seropositive. Isospora belli was recorded only from HIV seropositive patients (5.4% of all the patients studied and 6.5% of those who were HIV seropositive). These data confirm the good results obtained with this technique for the identification of Cryptosporidium spp and other coccidia and also reaffirm the clinical importance of correctly diagnosing the cause of diarrhoea, particularly in HIV seropositive patients.

Update on the management of intestinal cryptosporidiosis in AIDS

OBJECTIVE

To update readers on the pharmacotherapeutic management of cryptosporidiosis in patients with AIDS.

DATA SOURCES

A MEDLINE search was used to identify pertinent literature. Additionally, programs and abstracts from the 33rd Interscience Conference on Antimicrobial Agents and Chemotherapy; the 1st International Conference on Macrolides, Azalides, and Streptogramins; the 93rd American Society for Microbiology Meeting; and the 6th and 7th International Conferences on AIDS were used.

DATA EXTRACTION

Available data from in vitro, animal, and human experiments were reviewed.

DATA SYNTHESIS

Intestinal cryptosporidiosis in patients with AIDS can be a life-threatening opportunistic infection. However, there can be significant variability in disease expression, including spontaneous remission. Supportive care with hydration and nutritional supplementation remains a hallmark of therapy. Unfortunately, there is no proven specific pharmacotherapy of cryptosporidiosis in patients with AIDS. Numerous agents have been analyzed for in vitro activity and efficacy in experimental animal models and actual human cases of the infection, including paromomycin, azithromycin, clarithromycin, octreotide, hyperimmune bovine colostrum, bovine transfer factor, and many others. Because limited numbers of controlled trials have been conducted with potential therapeutic agents, the majority of the information to date is preliminary in nature.

CONCLUSIONS

Despite the availability of some evolving and potentially promising treatment modalities, further controlled clinical trials are necessary to evaluate the role of pharmacotherapy for intestinal cryptosporidiosis in patients with AIDS.

Dose response of Cryptosporidium parvum in outbred neonatal CD-1 mice

Cryptosporidium parvum infectivity in a neonatal CD-1 mouse model was used to determine the dose needed to infect 50% of the population. The 50% infective dose was estimated to be 79 oocysts. It was observed that a mean oral inoculum of 23 oocysts produced infection in 2 of 25 neonatal mice 7 days postinoculation. All animals became infected when the mean oral dose exceeded 310 oocysts per animal. The dose response of C. parvum was modeled with a logit dose-response model suitable for use in water disinfection studies.

Cryptosporidium: different behaviour in calves of isolates of human origin

The behaviour in calves of 3 Cryptosporidium human isolates was analysed in comparison with a bovine isolate. Twenty-four neonatal calves were infected. An isolate from a patient infected with human immunodeficiency virus (HIV) and showing mild cryptosporidiosis caused severe diarrhoea with a high production of oocysts in neonatal calves, as did a bovine isolate (group 1). Two human isolates, obtained from HIV patients with severe cryptosporidiosis, caused mild diarrhoea with low oocyst production in neonatal calves (group 2). The difference between the 2 groups in numbers of oocysts shed in calves was statistically significant (P = 0.005), as was the duration of oocyst shedding (P = 0.0004). Oocysts of group 2 isolates were less resistant to storage in 2% potassium dichromate at 4 degrees C than were oocysts of group 1. The biological and epidemiological implications are discussed.

Sexually transmitted causes of gastrointestinal symptoms in homosexual men

The possible etiologic agents that may cause gastrointestinal complaints in homosexually active men are multiple, and their diagnosis is complex. This article presents a logical approach to the work-up and diagnosis of gastrointestinal complaints in homosexually active men and to discuss their treatment and disease intervention.

Ileal and jejunal absorptive function in patients with AIDS and enterococcidial infection

Small intestinal absorptive function was investigated in six patients with the acquired immunodeficiency syndrome (AIDS) who had diarrhoea and weight loss. Proximal function was assessed by [14C]Triolein test of fat absorption. Distal function was determined by a test of bile acid absorption in which the loss of radio-labelled synthetic bile acid, 75seleno-23-homocholic acid-taurine ([75Se]HCAT), from the enterohepatic circulation was quantified by abdominal gamma-scanning and by a vitamin B12-intrinsic factor absorption test. Concurrently indirect tests of small intestinal bacterial overgrowth ([14C]glycocholate and breath hydrogen) were carried out. In addition, jejunal histological examination and stool microscopy and culture for enteropathogens were performed. Fat absorption was reduced in all six patients, four of whom had jejunal villous atrophy. Bile acid and vitamin B12 absorption were normal in four subjects. Enteropathogens were not detected in any of the four subjects with normal terminal ileal absorptive function. In contrast, reduced bile acid and vitamin B12 absorption were detected in two of six subjects. Both patients had an enteropathogen (Cryptosporidium spp. and Isospora belli) present on stool and jejunal histological examination. Neither subject had evidence of small-intestinal bacterial overgrowth. AIDS patients therefore may have normal ileal absorptive function in the presence of jejunal disease. Infection with Cryptosporidium spp. or I. belli may however, be associated with severe ileal dysfunction.

Protracted enteric cryptosporidial infection in selective immunoglobulin A and saccharomyces opsonin deficiencies

Chronic cryptosporidial infection in man usually occurs in those who are immunocompromised. We report a patient with a one year history of bowel symptoms resulting from persistent cryptosporidial infection of the colon. Investigations showed underlying selective IgA and saccharomyces opsonin deficiencies but no evidence of cell mediated immune dysfunction. Both selective immunoglobulin A and opsonin deficiencies are relatively common in the general population and may be a cause of susceptibility to persistent cryptosporidial infection.

Cryptosporidiosis and AIDS

Cryptosporidiosis in patients with AIDS presents as a chronic enteritis, with biliary complications in about 10% of sufferers. The disease is persistent and progressively fatal. Due to the widespread prevalence of the parasite in the community and amongst domesticated animals, persons with AIDS are constantly at risk. Treatment is extremely difficult in view of the apparent lack of a specific anticryptosporidial drug. Methods of immunomodulation are worth considering, but the main recourse may have to be a prolonged regimen of rehydration and parenteral nutrition. However, if T helper cell function improves, the disease may go into remission or the parasite could be eliminated. Vaccination of those at risk is not feasible at present.

Alimentary tract cytopathology in human immunodeficiency virus infection: a review of experience in Los Angeles

In the past decade, over 100,000 cases of the acquired immunodeficiency syndrome (AIDS) have been reported in the United States. Conservative estimates suggest that 1.5 million people are infected with the human immunodeficiency virus (HIV), the etiologic agent of AIDS. Major metropolitan areas, such as Los Angeles, have experienced a rapid increase in the number of AIDS cases. At the Los Angeles County-University of Southern California Medical Center, we have gained significant insight into the cytologic findings associated with HIV infection. Based on our experience, we herein review the technical and morphologic evaluation of alimentary tract cytology specimens from this patient population.

Parasite infections in AIDS

'Illnesses no one's got' was the epidemiological clue that led to the identification of AIDS as a new disease in 1981 when a rare infectious organism Pneumocystis carinii was seen in previously healthy homosexuals. Since then a wide range of parasite infections has been recognized in AIDS patients. However, these patients are not susceptible to just any passing parasite. The human immunodeficiency virus (HIV) produces a specific immune defect and only parasites that can exploit that defect will be able to flourish. In this review Diana Lockwood and Jonathan Weber explore the spectrum of parasite diseases recognized in AIDS and also consider those parasites that occur infrequently in AIDS. Analysis of parasitic infections that AIDS patients do not suffer from will yield valuable information about immune recognition and handling of these parasites.

Protozoal infections in the acquired immunodeficiency syndrome

Several protozoa have emerged as the major opportunistic infections and cause of death in patients with acquired immunodeficiency syndrome (AIDS). Pneumocystis carinii pneumonia is the leading cause of death in AIDS patients. Electron microscopy (EM) usually shows numerous trophozoites and cysts of Pneumocystis filling up the entire alveolar space, while only cysts are seen under the light microscope. The focal thickening of cyst wall of Pneumocystis, as demonstrated by EM and manifested as a "parentheses" shaped structure with silver stain, serves as a diagnostic marker for Pneumocystis. Freeze-fracture EM has demonstrated the intimate contact between Pneumocystis trophozoites and the type I pneumocytes, which may contribute to the alveolar-capillary block, leading to severe respiratory distress. However, EM is seldom needed for the diagnosis of this infection. Toxoplasma encephalitis, which is an unusual clinical manifestation in cases of toxoplasmosis reported previously, has become a common complication and one of the major causes of death in patients with AIDS. Because subclinical infection by Toxoplasma is common, serologic tests usually offer no definite answers as to whether the infection is acute or chronic, active or past. The small size and its non-specificity in both morphology and tissue affinity make light microscopic diagnosis of toxoplasmosis difficult. Only immunologic staining, such as immunoperoxidase and immunofluorescence, can help to achieve a definite positive identification of the organism. When special antibodies or facility for such staining is not available, EM is the final resort for identifying Toxoplasma by showing the apical complex with the characteristic sausage-shaped rhoptries. Cryptosporidiosis, practically unknown before the AIDS outbreak, has become one of the most common intestinal protozoa in both immunocompromised and immunocompetent patients. The protracted and sometimes fatal course of cryptosporidiosis in immunocompromised patients can be explained by the presence of autoinfective oocysts (thin-walled oocysts), as detected by EM, and by recycling of first-generation schizonts observed experimentally. While diagnosis of cryptosporidiosis can be made by detection of oocysts in stools in most cases, EM is still the last resort for a definitive identification of Cryptosporidium species. While the incidence of isosporiasis is still low, it has been found more frequently in patients with AIDS than in the general population. The parasite, Isospora belli, being a coccidian as is the Cryptosporidium species, is similar to the latter in its life cycle and clinical manifestations.(ABSTRACT TRUNCATED AT 400 WORDS)

Cryptosporidiosis in perspective

In this review I have examined the vast literature which has accumulated on Cryptosporidium, particularly in the past 3 years, in an attempt to highlight areas in which progress has been made in relation to the organism and the disease, and to indicate areas in which knowledge is still lacking. Since 1982, a global effort by scientists and clinicians has been directed towards determining the nature of the disease in humans and the relative contribution of cryptosporidiosis to gastroenteritis. From published data, the incidence of diarrhoea is 1-5% in most developed countries, and 4-7% in less developed countries, when measured throughout the year and in all age groups. The frequency of cryptosporidiosis is highest in children aged between 6 months and 3 years, and in particular locations (e.g., day-care centres) and at particular times of the year. Although susceptibility to infection is life-long, one suspects that the lower prevalence among older children and adults is due to immunity acquired from frequent exposure. Other important factors contributing to higher prevalence are the season--it is more frequent in a wet, warm climate--association with travel to particular destinations, poor hygiene, intimate contact with certain animals, and congregation of large numbers of young previously unexposed children in day-care centres. The association between cryptosporidiosis and giardiasis presumably results from the existence of a common source of infection. The immune status of the host appears to be a major determinant of whether the infection is self-limiting or persistent. It is clear that both branches of the immune system are required for complete recovery, since T-lymphocyte dysfunction or hypogammaglobulinaemia can both lead to persistent illness. Chronic diarrhoea and malabsorption attributed to cryptosporidiosis also occur in the absence of evidence of immune defect. The importance of respiratory tract infection in humans, other than in the terminal stages of chronic illness, requires investigation. The infection has now been identified in all classes of vertebrates; it has been observed in all domestic animals including pets, and a wide range of wildlife including birds. Cryptosporidiosis seems to cause diarrhoea in young ruminants, less frequently in pets. In birds the parasite has been observed in the gastrointestinal tract, without ill effect, and in the respiratory tract, in which clinical symptoms of variable severity have been described. The mucosal response of the gastrointestinal tract to infection appears to vary among mammals and may be the key to the variable clinical manifestations observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Spiramycin in the treatment of cryptosporidiosis

Spiramycin, a macrolide antibiotic, has been advocated for the treatment of cryptosporidiosis. The disease most commonly occurs in patients with AIDS and can be debilitating, as diarrhea and malnutrition may be contributing factors in the death of these patients. Until recently, treatment for cryptosporidiosis has been largely symptomatic. Response rates with drug therapy such as metronidazole, quinidine-clindamycin, and pentamidine have been extremely poor. Although response to spiramycin has appeared promising, there have been several reported cases of treatment failure. Further investigation with the agent is advocated to determine its role in the treatment of cryptosporidiosis.

Cryptosporidium species, a protean protozoan

Images

Parasitic diseases of the small intestinal tract

The epidemiology, clinical aspects, and treatment of human intestinal infections with Giardia, Cryptosporidium, coccidia and Strongyloides in industrialized countries are reviewed. In well-nourished and immunocompetent persons, inapparent infections or mild, transitory gastrointestinal upsets caused by these parasites are quite common. Some patients develop severe symptoms, such as profuse diarrhoea, dehydration, stool irregularities for weeks or months followed by weight loss and malabsorption of fat, vitamins and iron. In patients receiving immunosuppressive treatment or with lymphotropic viral infections, Cryptosporidium and Strongyloides can cause life-threatening or debilitating disease. By autoinfection or external reinfection these parasites can persist in the intestine for years. Clinicians should consider such infections in immigrants, travellers and former servicemen, even long after their stay in endemic areas, and also in the handicapped and children in day-care centres.

Cryptosporidium spp. and cryptosporidiosis

Images

Gastrointestinal manifestations of the acquired immunodeficiency syndrome

The increasing frequency of acquired immunodeficiency syndrome (AIDS) mandates that all physicians be aware of the diverse nature of problems that affect this group of patients. The gastrointestinal tract is involved in approximately 50% of patients with AIDS, although not all are symptomatic. Common problems include diarrhea, malabsorption, and weight loss. These can be due to enteric infection, neoplasia, or an ill-defined enteropathy. Gastrointestinal bleeding can also become problematic either as a presenting manifestation of the illness or during the prolonged periods of debilitation that many of these individuals experience. An aggressive diagnostic approach is necessary to recognize treatable abnormalities in the digestive tract of AIDS patients.

Immunofluorescence detection of Cryptosporidium oocysts in fecal smears

An indirect fluorescent antibody (IFA) procedure was developed for the detection of Cryptosporidium sp. oocysts in human, nonhuman primate, and bovine fecal smears. The procedure, which takes about 90 min to perform, involves the use of a rabbit antiserum against Cryptosporidium oocysts isolated from dairy cattle. Cross-specificity testing of the IFA method revealed no reactivity with yeasts, various amoebae, Giardia lamblia, Chilomastix sp., or Blastocystis sp. and only very weak cross-reactivity with coccidian oocysts of other genera. IFA detection of oocysts in human and nonhuman primate fecal smears was far more sensitive than was dimethyl sulfoxide-carbolfuchsin staining. Moreover, IFA detection was comparable in sensitivity to auramine O staining with samples of high oocyst concentration and somewhat more sensitive than auramine O with samples containing relatively few oocysts. The IFA procedure may be useful in the clinical diagnosis of human and animal cryptosporidiosis and also in the detection of oocysts in environmental samples.

Clinical manifestations and therapy of Isospora belli infection in patients with the acquired immunodeficiency syndrome

Isospora belli has recently been recognized as an opportunistic protozoan pathogen in patients with the acquired immunodeficiency syndrome (AIDS). Although I. belli rarely causes diarrhea in patients with AIDS in the United States, we have documented isosporiasis in 15 percent (20 of 131) of such patients in Haiti. The infection was associated with chronic watery diarrhea and weight loss that was clinically indistinguishable from disease caused by the related coccidia cryptosporidium. No demographic or laboratory data distinguished the patients with AIDS and isosporiasis from those with either cryptosporidiosis or other opportunistic infections. Neither I. belli nor cryptosporidium was detected in stool samples from 170 healthy siblings, friends, and spouses of the patients with AIDS. In all patients with isosporiasis, diarrhea stopped within two days of the beginning of treatment with oral trimethoprim-sulfamethoxazole. Recurrent symptomatic isosporiasis developed in 47 percent of the patients, but it also responded promptly to therapy with trimethoprim-sulfamethoxazole. We conclude that isosporiasis is common in Haitian patients with AIDS, and that it responds to therapy with trimethoprim-sulfamethoxazole but is associated with a high rate of recurrence.

Quantification of specific antibody response to Cryptosporidium antigens by laser densitometry

Cryptosporidium spp. is a protozoan parasite with worldwide distribution associated with diarrhea in immunocompromised patients (particularly those with acquired immunodeficiency syndrome [AIDS]) and in immunocompetent humans. Immunoglobulin M (IgM) and IgG antibody responses are readily detected by an enzyme-linked immunosorbent assay. To determine which Cryptosporidium antigens invoke antibody responses in humans, we performed polyacrylamide gel electrophoresis using purified oocysts, followed by Western blots with human sera from various populations. Of 40 sera from persons with cryptosporidiosis (24 AIDS and 16 non-AIDS patients), in 37 (93%) a 23,000-dalton antigen measured quantitatively by laser densitometry was recognized. Of 63 sera from IgM- or IgG-positive individuals, as determined by enzyme-linked immunosorbent assay, in 58 (92%) this same antigen was recognized. Up to three additional bands between 125,000 and 175,000 daltons were identified by some of these sera. These results suggest that most persons infected with Cryptosporidium spp. produce antibodies which recognize at least one common low-molecular-weight antigen. Isolation of this antigen will be useful in development of diagnostic tests and may be important in the study of immunity.

Abnormalities in intestinal mucosal T cells in homosexual populations including those with the lymphadenopathy syndrome and acquired immunodeficiency syndrome

Enteric infections are common in homosexual men. We have characterized the phenotypic distribution of small intestinal mononuclear cells among healthy homosexual men, homosexual men with lymphadenopathy syndrome, homosexual men with acquired immunodeficiency syndrome (AIDS), and a group of healthy heterosexual men. Total numbers of T lymphocytes in the small intestinal mucosa were significantly decreased in homosexual men with lymphadenopathy syndrome and AIDS. This decrease was most striking among the Leu-3a T-cell subset usually associated with helper/inducer function. The proportion of mucosal T cells reacting with Leu-2a (cytotoxic/suppressor phenotype) and lymphoid cells having the T305 antigen was significantly increased only in AIDS subjects. Both lymphadenopathy syndrome and AIDS subjects had a significant reversal of the normal mucosal helper/suppressor T-cell ratio. Mucosal helper/suppressor T-cell ratios and the distribution of mucosal mononuclear cells were normal in healthy homosexual men, although the same individuals had reversed helper/suppressor ratios among circulating T cells. Enteric infections in healthy homosexual men likely reflect sexual practices, and not a primary abnormality in intestinal mucosal immunity. In contrast, specific abnormalities in intestinal mucosal immunity may contribute to the persistent and opportunistic enteric infections that occur in AIDS.

An update on the acquired immunodeficiency syndrome (AIDS). Associated disorders of the alimentary tract

The pandemic, acquired immunodeficiency syndrome (AIDS) has been described in 40 nations throughout the world. This paper describes the wide spectrum of gastrointestinal tract manifestations seen in this syndrome, with particular attention to the epidemiology, etiology, and measurement of these problems. Discussion of candidiasis, herpes simplex, "hairy" leukoplakia, Kaposi's sarcoma, cytomegalovirus, anal warts and carcinoma, chlamydial proctitis (LGV), coccidiosis, and mycobacterial diarrhea, as well as "gay bowel syndrome," demonstrates the complex management problems associated with this condition.