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Fungal infections are ignored by social and political communities. However, they are estimated to affect more than a billion people, resulting in approximately 11·5 million life-threatening infections in the ‘at risk’ population and more than 1·5 million deaths annually. Though there have been huge advances in diagnostics and antifungal drug development over the past two decades, however, resource limited settings have not benefited from these advances. The aim of this research was to determine the burden of serious fungal infections in Nigerians with the appropriate underlying diseases. This epidemiological research was conducted across four study populations. Study 1; HIV-infected patients with CD4+ counts

SUMMARY Background. Disseminated histoplasmosis is common in AIDS patients with advanced immunosuppression in Ceará, Northeastern Brazil. The goal of this study was to determine the prevalence of Histoplasma infection in patients with HIV/AIDS living in Fortaleza, the capital of Ceará. Methods. Intradermal tests with histoplasmin (mycelial phase) were performed in 161 HIV patients with CD4 ≥ 350 cells/mm 3 . Evidence of recent illness was evaluated with immunodiffusion (ID) tests in 76 of these individuals. Results. A total of 11.8% of patients reacted to histoplasmin and 2.63% had ID test positive to Histoplasma. The presence of mango trees (Mangifera indica) in the patient neighborhood (OR = 2.870; 95% CI = 1.081-7.617; p = 0.040) and past activity involving soil (OR = 2.834; 95% CI = 1.045-7.687; p = 0.045) or visits to a farm (OR = 3.869; 95% CI = 1.189-12.591; p = 0.033) were significantly associated with Histoplasma infection. Conclusions. Patients with HIV living in Fortaleza have an expressive prevalence of infection with Histoplasma. RESUMO Introdução: Histoplasmose disseminada ocorre com grande frequência em pacientes com aids e imunossupressão avançada no Ceará, Brasil. O objetivo deste artigo é determinar a prevalência da infecção por Histoplasma em pacientes com HIV/aids residentes em Fortaleza capital. Métodos. Testes intradérmicos com histoplasmina (fase micelial), foram realizados em 161 pacientes com CD4 ≥ 350 células/mm 3 . Doença recente foi estudada por imunodifusão em 76 desses indivíduos. Resultados. Reagiram à histoplasmina, 11,8% dos pacientes e à imunodifusão para Histoplasma: 2,63%. A presença da árvore mangueira (Mangifera indica) na vizinhança (OR = 2,870; IC 95% = 1,081-7,617; p = 0,040), atividade com o solo no passado (OR = 2,834; IC 95% = 1,045-7,687, p = 0,045) e visitar sítio no passado (OR = 3,869; IC 95% = 1,189-12,591; p = 0,033); foram significativamente associados com positividade para o teste. Conclusões. Pacientes com HIV que vivem em Fortaleza apresentam uma prevalência expressiva de infecção por Histoplasma.

Objectives Disseminated histoplasmosis is an AIDS-defining illness. Histoplasmosis is commonly misdiagnosed as tuberculosis. Nigeria has the second highest number of people living with HIV/AIDS in Africa. The present study was carried out to investigate the prevalence of skin sensitivity amongst Nigerians to histoplasmin. Design A cross-sectional study was conducted in six centres across five geopolitical zones of Nigeria. Methods We recruited both healthy non-HIV and HIV-positive adults with CD4 count ≥ 350 cells/mm3 regardless of their ART status from March to May 2017. Skin tests were performed intradermally; induration ≥5 mm were considered to be histoplasmin positive. Results 750 participants were recruited from Lagos (n = 52), Yola (n = 156), Ilorin (n = 125), Calabar (n = 120), Ibadan (n = 202) and Benin (n = 95). 467 (62.3%) were HIV negative, 247 (32.9%) were HIV positive and 36 (4.8%) did not know their HIV status. A total of 32/735 (4.4%) participants had a positive skin test. Study centre (p

Histoplasma capsulatum is a dimorphic pathogenic fungus that causes a wide spectrum of disease when mycelial fragments are inhaled. Resistance to H. capsulatum is dependent on cellular immunity mediated by T cells and macrophages. Here we standardized the production of extracts containing cell-free antigens (CFAgs) and observed their efficacy in evaluating cellular immunity during murine histoplasmosis. CFAgs induced a more potent delayed-type hypersensitivity (DTH) response in H. capsulatum -infected mice than did histoplasmin—a classical antigen. This DTH response to CFAgs is able to determine the immune status of infected mice and to predict their death. Moreover, CFAgs stimulated spleen cells from immune mice to produce higher amounts of gamma interferon (IFN-γ) in vitro. Finally, immunization with CFAgs protected against a lethal inoculum of H. capsulatum . These results demonstrate that CFAgs may be useful for the evaluation of cellular immune response and as a potential source for the development of a vaccine against histoplasmosis.

In June 1994, 18 people developed serologically confirmed histoplasmosis following cave exploration associated with the annual National Speleological Society Convention in Bracketville, Texas. Six others had an undiagnosed illness suspected to be histoplasmosis. Two persons were hospitalized. We conducted a survey of convention attendees and a nested case-control study of those entering caves. We also conducted a histoplasmin skin test survey of a subgroup of the society, the Texas Cavers Association, who were attending a reunion in October 1994. Among the national convention attendees, exposure to two caves was identified as responsible for 22 (92%) of the 24 cases; 12 (75%) of 16 people exploring one cave (Cave A) and 10 (77%) of 13 exploring a separate cave (Cave B) developed acute histoplasmosis. Additional risk-factors included fewer years of caving experience, longer time spent in the caves, and entering a confined crawl space in Cave A. Of 113 participants in the separate skin test survey, 68 (60%) were found to be skin test positive, indicating previous exposure to Histoplasma capsulatum. A positive skin test was significantly associated with male sex and more years of caving experience. Those less experienced in caving associations should be taught about histoplasmosis, and health care providers should pursue histories of cave exposure for patients with bronchitis or pneumonia that does not respond to initial antibiotic therapy.

A western blot (WB) test was evaluated for detection of antibodies against native glycosylated and chemically deglycosylated M and H antigens of Histoplasma capsulatum in serum obtained from patients during the acute phase of pulmonary histoplasmosis that occurred during an outbreak. Of 275 serum samples tested by immunodiffusion and complement fixation (CF) samples from 40 patients affected during this outbreak and from 37 negative controls were tested by WB test. A group of patients whose sera were negative for CF antibodies and precipitins early in the acute stage of histoplasmosis but who all seroconverted during convalescence 6 weeks later were tested with the WB test. Antibodies against untreated H and M antigens were detected at a 1:100 dilution by WB test in 45% of the 20 acute-phase serum samples and in all 20 of the convalescent-phase specimens. The WB test’s sensitivity for acute-phase specimens increased to 90% (18 of 20 specimens) when H and M antigens were treated by periodate oxidation to inactivate susceptible carbohydrate epitopes. When native glycosylated antigens were used in the WB test, positive reactions were observed in negative control serum specimens (3 of 37 specimens; 8%) and in serum specimens obtained from asymptomatic persons screened as part of the outbreak investigation (13 of 20 specimens; 65%). These positive reactions were also attributed to glycosidic epitopes since the specificity of the WB test increased from 78 to 100% when periodate-treated H and M antigens were used. WB test with deglycosylated H and M antigens of histoplasmin provides a rapid, sensitive, and specific test to diagnose acute pulmonary histoplasmosis before precipitins can be detected.

We report here the results obtained in epidemiologic surveys of histoplasmosis and paracoccidioidomycosis carried out in Brazil using the histoplasmin and paracoccidioidin delayed hypersensitivity skin tests. Most of these data have not been previously published in scientific journals and are now reported here in two tables respectively concerning histoplasmosis (88 surveys) and paracoccidioidomycosis (58 surveys). The guidelines to be followed in surveys of this nature are also commented upon. Inquéritos epidemiológicos com histoplasmina e paracoccidioidina no Brasil Esta publicação visa a tornar acessíveis os resultados obtidos em inquéritos epidemiológicos sobre histoplasmose e paracoccidioidomicose, realizados no Brazil, através das reações intradérmicas de histoplasmina e paracoccidioidina. Ela justifica-se porque os resultados aqui relacionados, em grande parte, não foram publicados em revistas científicas. Os resultados que conseguimos colecionar são apresentados nas tabelas: 1 _ sobre histoplasmose e 2 _ sobre paracoccidioidomicose. Ao todo são relacionados 88 inquéritos sobre histoplasmose e 58 sobre paracoccidioidomicose. No final da publicação são feitos comentários sobre os ítens a serem obedecidos em inquéritos desta natureza.

The aim of the study presented here was to assess the incidence of histoplasma infection in a cohort of 342 individuals in Spain who had traveled to Latin America for the first time. The histoplasmin skin test was positive in 20% of the travelers, and Central America posed a higher risk for infection than South America (p=0.013). Sleeping outdoors (p=0.031) and the duration of travel (p=0.016) were also identified as significant risk factors. Serological testing demonstrated poor overall sensitivity for detecting infection in the travelers, but for the symptomatic acute cases the results were improved. Histoplasmosis must be considered in patients presenting with fever (odds ratio=3.51 [1.52-8.12]) or cough (odds ratio=4.24 [1.32-13.58]) after visiting Latin America. The results of this study have public health implications and indicate the risks of acquiring histoplasmosis should be included in pre-travel counseling.

Histoplasmosis is a multifaceted condition caused by the dimorphic fungi Histoplasma capsulatum whose infective spores are inhaled and reach the lungs, the primary organ of infection. The meningeal form, considered one of the most serious manifestations of this mycosis, is usually seen in individuals with impaired cellular immunity such as patients with acquired immunodeficiency syndrome, systemic lupus erythematous or solid organ transplantation, and infants given their immunological immaturity. The most common presentation is self-limited and occurs in immunocompetent individuals who have been exposed to high concentrations of conidia and mycelia fragments of the fungi. In those people, the condition is manifested by pulmonary disorders and late dissemination to other organs and systems. We report a case of central nervous system histoplasmosis in an immunocompetent child.

Skin tests with paracoccidioidin, histoplasmin and sporotrichin were applied to 417 workers of Morro Velho Mining in the State of Minas Gerais, Brazil, with the main purpose of detecting the prevalence of paracoccidioidomycosis-infection, histoplasmosis capsulate-infection and sporotrichosis-infection. The rates of positivity to the skin tests were 13.43% for paracoccidioidin, 17.50% for histoplasmin and 13.67% for sporotrichin. Several epidemiological factors were investigated for a better interpretation of the results. Paracoccidioides brasiliensis, Histoplasma capsulatum var. capsulatum and Sporothrix schenkii were not isolated from the soil samples from the mines investigated.

A pair-matched, case-control design was used to study exposure to Histoplasma capsulatum and other environmental factors, and to determine various host characteristics including human leukocyte antigen (HLA) typings in 94 young patients with macular choroidal neovascularization (CNV) and in 94 controls with other eye diseases. Patients with two types of retinal patterns were studied: Type I, or those with CNV with one or no chorioretinal atrophic spots in the posterior pole or periphery (n = 51), and Type II, or those with CNV and 2 or more chorioretinal atrophic spots (n = 43). Our purpose was to explore whether these two variants of idiopathic CNV have different and distinguishable epidemiologies which may or may not be related to prior exposure to Histoplasma. We found that histoplasmin skin tests were negative in all but two Type I cases. The combination of the HLA-B7 and HLA-DR2 markers (but not either marker alone) was significantly increased in Type I cases. Among Type II cases, HLA-B7, HLA-DR2, HLA-DQ1, a positive histoplasmin skin test, myopic refractive error, prior residence in a histoplasmosis endemic area, occupations involving exposure to animals, and hypertension were all significantly increased. Histoplasmin skin test responses were positive in 18 Type II cases (45%). In the multivariate analysis, only DR2 and the combined presence of DQ1 and a positive histoplasmin skin test remained predictive of Type II disease. Our findings suggest that histoplasmin sensitivity is associated with some, but not all, cases of Type II disease. However, histoplasmin sensitivity appears to have no relationship to Type I disease. HLA factors may play a role in both disease types, possibly by producing a modified immune response to Histoplasma and/or other unidentified agents.

The enzyme-linked immunoelectrotransfer blot (EITB) method was evaluated as a suitable method for detecting antibodies against M antigen of Histoplasma capsulatum by use of both glycosylated and deglycosylated M protein of histoplasmin (HMIN). Sera from patients with histoplasmosis, paracoccidioidomycosis, blastomycosis, coccidioidomycosis, and aspergillosis were tested by the EITB with glycosylated M protein of HMIN. This assay demonstrated 100% sensitivity with histoplasmosis serum samples, all of which reacted with the 94-kDa glycoprotein (M antigen). Although the EITB is highly sensitive, it is not specific for histoplasmosis when glycosylated M protein is used as an antigen. A total of 81% of paracoccidioidomycosis, 25% of blastomycosis, 33% of coccidioidomycosis, 73% of aspergillosis, and 16% of tuberculosis serum samples cross-reacted with M protein of HMIN and yielded patterns indistinguishable from those obtained with histoplasmosis serum samples. The EITB reactions with both untreated M antigen and M antigen altered by periodate oxidation or by deglycosylation with endoglycosidases were compared. Cross-reactions with heterologous sera in the EITB could be attributed to periodate-sensitive carbohydrate epitopes, as reflected by the increase in the test specificity from 46.1 to 91.2% after periodate treatment of M protein. The EITB for the detection of antibodies to M antigen is a potential diagnostic test for histoplasmosis, provided that periodate-treated M protein is used as an antigen.

SummaryThe natural habitat ofParacoccidioides brasiliensis, the aetiologic agent of paracoccidioidomycosis, has not been determined. Consequently, the events leading to the acquisition of infection remain controversial. To identify factors associated with infection in endemic areas we conducted a survey in three rural communities in Colombia where we had previously diagnosed paracoccidioidomycosis in children. Permanent residents were surveyed taking into consideration environmental and occupational variables. Skin tests were used to classify subjects as infected or non-infected. Variables found associated with infection were: (i) community A: previous residence around Porce river and agriculture in vegetable gardens; (ii) community C: frequent use of specific water sources; (iii) community V: housekeeping activities, and (iv) total group: age > 25 years and contact with bats. Residents in communities with higher prevalence of infection were older, had more complex residence history, and referred more contact with armadillos than residents of communities with lower infection.

In a recent paper we1reviewed the problem of calcification occurring in the chests of persons who are insensitive to tuberculin. At that time we outlined the clinical and epidemiologic evidence for suspecting a benign form of histoplasmosis or some other biologically related infection to be the cause of this phenomenon. These studies have been undertaken in order to throw light on certain clinical observations that there exists in many sections of the United States a prevalence of pulmonary calcification far in excess of that which can be explained on the basis of tuberculosis as revealed by tuberculin cutaneous testing. In the past twenty years there has been an increasing interest in this subject, and there have appeared a number of papers which show a consistent discrepancy between the tuberculin tests and the prevalence of pulmonary calcification. In these papers 27 to 83 per cent of young persons were

A histoplasmosis outbreak affecting 6 previously healthy Air Force cadets is herein presented. The patients suffered from fever and respiratory symptoms after having cleaned an abandoned hangar soiled with pigeons and bat droppings. They all presented fever, myalgia, tachypnea, and nonproductive cough. Chest X-ray and CT scan studies showed disseminated reticulonodular images affecting both lungs. Hiliar adenomegalies were also observed. All patients achieved a favourable outcome without antifungal treatment. Both serologic tests searching for specificic antibodies (immunodiffusion and counterimmunoelectrophoresis) and histoplasmin skin tests were positive in all cases. Five soil samples mixed with pigeons and bat droppings were collected from the hangar. Suspensions of these samples were inoculated into 20 hamsters by intraperitoneal injection; mycelial phase of H. capsulatum was isolated from liver and spleen cultures. The genetic profile of this strain was compared with 12 isolates obtained from Argentinean patients, and a great degree of homogeneity was observed (96% similarity). Although histoplasmosis is endemic in the wet Pampas, this is the first epidemic outbreak reported south of the 34th parallel.

It has recently been suggested that in the central eastern region of the United States there is a disease or a group of diseases which closely simulates tuberculosis. This has been indicated by the observation of pulmonary calcification in persons who are negative reactors to tuberculin but in whom the reaction to histoplasmin is positive. Until the past decade pulmonary calcification in the presence of a negative reaction to tuberculin has been considered a manifestation of a disturbance of the allergic mechanism, but the more probable explanation is that there is another disease or group of diseases which account for many instances of pulmonary calcification. That this is a likely possibility is demonstrated by the striking similarity in some instances of coccidioidomycosis to tuberculosis during the active and the end stages of disease. Christie and Peterson 1 and Palmer 2 have shown a correlation of sensitivity to histoplasmin with pulmonary

DURING the period of rapid demobilization of the United States Army following cessation of hostilities, many soldiers were found to have roentgenologic evidence of pulmonary pathema. This was discovered at routine physical examination during the process of their separation from the Service. More than 1,500 patients were sent to the Moore General Hospital from various separation centers over the country because of roentgenologic evidence of pulmonary disease. Most of them were asymptomatic. Their sputum on repeated examinations was negative for acid-fast organisms in more than 50 per cent of the cases. Of the total number, 3.5 per cent had a negative reaction to the cutaneous test for tuberculin. For the most part, these patients were to be observed for a period of at least six months. This period of observation was necessary to determine the presence of activity. All patients were considered to have pulmonary tuberculosis until it was proved

Epidemiologic studies of deep mycosis have been scarce in Bolívar state, where paracoccidioidomycosis and histoplasmosis are considered as endemic diseases. The aim of this study was to determine paracoccidioidomycosis and histoplasmosis prevalences in people from a suburb of San Félix, Bolívar state, Venezuela. Three-hundred volunteers agreed to participate in this study and they were inoculated with paracoccidioidine and histoplasmine. Identification and epidemiologic data were registered. Reading of skin tests after 24 hours was performed in 275 persons. Paracoccidioidine test was positive in 10.2% (n=28). A higher percentage of positive reactions in the age group of 40-50 years old (n=10; 35.7%) was observed. Bricklayers, farmers and miners were positive in 27.3 % (3 out of 11), a higher percentage than in people with other occupations. Histoplasmine test was positive in 7.6% of cases (n= 21). The higher percentage of reactivity was observed in the age group of 40-50 years old (n=9; 42.9%). There was a direct proportional relationship between staying time in the locality and H. capsulatum infection mainly in persons staying in the area for more than 30 years (p

La paracoccidioidomicosis es una de las micosis sistémicas más frecuente en Venezuela. Su agente etiológico es Paracoccidioides brasiliensis. Investigaciones previas, sugieren que en el Municipio Tovar del estado Aragua (Venezuela) existen zonas endémicas para Paracoccidioides brasiliensis en las que los agricultores están ocupacionalmente expuestos. Además, han sido descritas algunas áreas endémicas comunes para Paracoccidioides brasiliensis y Histoplasma capsulatum. En consecuencia, se determinó la prevalencia de la infección por ambos hongos en 131 agricultores del "Caserío La Entrada" (Municipio Tovar), mediante la intradermorreacción a la paracoccidioidina e histoplasmina. La prevalencia fue 90,1% para Paracoccidioides brasiliensis y 72,5% para Histoplasma capsulatum, encontrándose copositividades en 88 agricultores (67%). No se encontró asociación estadísticamente significativa (p=0,186) entre las intradermopositividades. La frecuencia de infección por Paracoccidioides brasiliensis y/o Histoplasma capsulatum resultó independiente de la edad, sexo y del tiempo laborando en la agricultura. Altos porcentajes de intradermopositividades fueron encontrados en menores de 10 años de edad (paracoccidiodina: 89,3%; histoplasmina: 75%) y en aquellos que tenían menos de un año como agricultores (paracoccidiodina: 85,4%; histoplasmina: 65,9%). Los hallazgos obtenidos sugieren que en el área geográfica estudiada coexisten Paracoccidioides brasiliensis y Histoplasma capsulatum. Además, que la infección ocurre rápida y tempranamente en la vida de estos individuos, permitiendo inferir que la endemicidad de estos microorganismos y el riesgo de contraer la infección son elevados en los trabajadores agrícolas. The paracoccidioidomycosis is one of the more frequent systemic mycosis in Venezuela. His etiologic agent is Paracoccidioides brasiliensis. Previous investigations, suggest the existence of endemic zones for Paracoccidioides brasiliensis in which the farmers are occupationally exposed in the Tovar Municipality of the Aragua state (Venezuela). In addition, some common endemic areas for Paracoccidioides brasiliensis and Histoplasma capsulatum have been described. Consequently, the prevalence of the infection by both fungi was determined in 131 farmers from the "Caserío La Entrada" (Tovar Municipality), by means of the intradermoreaction to paracoccidioidin and histoplasmin. The prevalence was 90.1% for Paracoccidioides brasiliensis and 72.5% for Histoplasma capsulatum, being the skin reactivity positive for both antigens in 88 farmers (67%). Association was not statistically significant (p=0,186) among the skin reactivities. The frequency of infection by Paracoccidioides brasiliensis and/or Histoplasma capsulatum was independent from age, sex and time working in farms. High percentages of skin reactivity were found in individuals under 10 years of age (paracoccidiodin: 89.3%; histoplasmin: 75%) and in people working as farmers less than one year (paracoccidiodin: 85.4%; histoplasmin: 65.9%). Findings suggest that there is a coexistance of Paracoccidioides brasiliensis and Histoplasma capsulatum in the studied geographic area. In addition, the infection occurs fast and early in the life of these individuals, allowing to infer that those microorganisms are endemic and the risk of contracting the infection are elevated in the farmers.

Detection of complement-fixing antibody to coccidioidin by using the complement fixation test or an immunodiffusion assay for complement-fixing antibody (IDCF) is widely viewed as the most useful immunodiagnostic test for coccidioidomycosis. In this investigation, we report the production of an immunoglobulin G subclass 1 (IgG1) monoclonal antibody (MAb) to the IDCF antigen for use as a biospecific ligand for purifying the IDCF antigen on solid-phase immunosorbents and for use as a reagent for screening genomic or cDNA expression libraries from Coccidioides immitis. BALB/c mice were immunized by intramuscular injections of coccidioidin in adjuvant, followed by an intrasplenic booster injection of coccidioidin in saline. The spleen cells were fused with SP2/0 Ag14 myeloma cells, and the fusion products were screened for IgG antibody to coccidiodin by using an enzyme-linked immunosorbent assay. Positive hybridomas were cloned and evaluated for reactivity to the IDCF antigen by two-dimensional immunoelectrophoresis and by immunoblotting. An IgG1 Mab was produced that was specific for the IDCF antigen when evaluated by two-dimensional immunoelectrophoresis and immunoblotting. The epitope recognized by the MAb was heat labile (60 degrees C, 30 min) and susceptible to enzymatic digestion with pronase but was resistant to treatment with lipase, alpha-mannosidase, glucose oxidase, and endoglycosidase H. This heat-labile peptide epitope appears to be specific to C. immitis, as judged by the fact that the MAb was not reactive in immunoblots or enzyme-linked immunosorbent assays of histoplasmin or blastomycin.

The incorporation of (3H) thymidine and the biosynthesis of interleukin-2(IL-2) were investigated in Concanavalin A (ConA) and histoplasmin stimulated lymphocytes from spleen of infected Balb/c mice with the yeast phases of Histoplasma capsulatum. The ability to incorporate (3H) thymidine of Con A stimulated lymphocytes in culture from spleen of Histoplasma capsulatum infected mice, as well as the IL-2 content present in the supernatants of that cultures, were depressed along the first three weeks of the experiments, but starting week five, normal values were restored or even discretly increased. Incorporation of (3H) thymidine in histoplasmin stimulated lymphocytes remained inhibited along the seven weeks the experiment lasted. Results showed that inoculation of H. capsulatum yeast in mice provoked a temporary immunosuppression on cell mediated immunity, that can be explained by means of the inability of T cells to produce enough IL-2 necessary for the proliferation of T cells in culture.

One hundred one subjects living in northwest Hunan Province, People's Republic of China (PRC) were tested with histolyn, (Berkeley Biological Laboratories), spherulin (Berkeley Biological Laboratories), and tubersol (PPD 5 tuberculin units, Connaught Laboratories). Age of the tested subjects ranged from 16 to 58 years; 93 subjects were 22 years old or younger. Nine subjects reacted to histolyn with 5.0 mm or more induration, two subjects reacted to spherulin, and 34 subjects reacted to tubersol. One of the spherulin reactors also reacted to both histolyn and tubersol. The feasibility and advisability of doing a large-scale survey throughout the PRC seem clearly supported by this pilot project.

To understand the host-parasite relationship in histoplasmosis, mice were inoculated with histoplasmin (HP), the filtrate of aged cultures of Histoplasma capsulatum, and the immune response of these mice towards sheep red blood cells (SRBC) and to trinitrophenyl hapten was studied. The filtrate abrogated completely the primary antibody response to both antigens as measured by the number of spleen hemolytic plaque forming cells when HP was administered at doses greater than 200 micrograms two days before the antigen. Suppression was elicited by HP when it was injected either intravenously, intraperitoneally, or subcutaneously. Inoculation with HP and antigen on the same day did not result in suppression. The secondary antibody response was not modified at any dose. Variation of the response with time was determined by counting the number of rosette forming cells (RFC) to SRBC every two days for a total of 21 days. Antibody-mediated RFC ('B' rosettes) were depressed throughout the experiment, while the number of non 'B', presumably T, RFC did not vary from control values. In animals inoculated with HP alone, high number of RFC were detected on day 11 after HP inoculation, suggesting that HP may have polyclonal activation effects. These results support the possibility that H. capsulatum evades the immune defenses by induction of a suppressive phenomenon in which the afferent limb of the immune response is not involved. This effect appeared to be induced directly by a product of the fungus, instead of by factors generated during the immune response to this microorganism.

We have developed an indirect sandwich enzyme-lined immunosorbent assay (ELISA) for the detection of antibodies to Histoplasma ribosomes and histoplasmin; we used this test for demonstration of these antibodies in sera from proven cases of histoplasmosis and other infections. Serum dilutions from five negative controls used in each experiment were normalized against 50 normal sera, and a factor of the mean absorbance was used to establish a positive reaction. Antiribosomal antibodies were detected in 97% of the known histoplasmosis patients with ELISA titers ranging from 1:100 to over 1:12,800. In contrast, antibodies to histoplasmin were detected in only 75% of these sera; titers ranged from 1:100 to 1:12,800. Cross-reactions with sera from other fungal infections (blastomycosis, coccidioidomycosis, paracoccidioidomycosis, cryptococcosis, candidiasis, and aspergillosis) were seen in 46% of the cases with ribosomes and 37% with histoplasmin. Fifty percent of the sera from tuberculosis patients gave positive reactions with ribosomes and 29% with histoplasmin. These results warrant further studies on the significance of antibodies to ribosomes and histoplasmin in immunity to hlistoplasmosis.