Detection of specific antibodies to an antigenic mannoprotein for diagnosis of Penicillium marneffei penicilliosis

Antibody screening reveals antigenic proteins involved in Talaromyces marneffei and human interaction

Talaromycosis is a fungal infection that generally affects immunocompromised hosts and is one of the most frequent systemic mycoses in HIV patients, especially in endemic areas such as Southeast Asia. Talaromyces marneffei, the causative agent of talaromycosis, grows as a mold in the environment but adapts to the human body and host niches by transitioning from conidia to yeast-like cells. Knowledge of the human host and T. marneffei interaction has a direct impact on the diagnosis, yet studies are still lacking. The morbidity and mortality rates are high in taloromycosis patients if the diagnosis and treatments are delayed. Immunogenic proteins are excellent candidates for developing detection tools. Previously, we identified antigenic proteins that were recognized by antibodies from talaromycosis sera. Three of these identified proteins have been previously characterized in detail, while the others have not been explored. To expedite the progress of antigen discovery, the complete list of antigenic proteins and their features was fully reported in this study. Functional annotation and Gene Ontology examination revealed that these proteins showed a high association with membrane trafficking. Further bioinformatics analyses were performed to search for antigenic protein characteristics, including functional domains, critical residues, subcellular localization, secretory signals, and epitope peptide sequences. Expression profiling of these antigenic encoding genes was investigated using quantitative real-time PCR. The results demonstrated that most genes were expressed at low levels in the mold form, but were highly upregulated in the pathogenic yeast phase, consistent with the antigenic role of these genes during the human-host interaction. Most transcripts accumulated in the conidia, suggesting a role during phase transition. The collection of all antigen-encoding DNA sequences described here is freely accessible at GenBank, which could be useful for the research community to develop into biomarkers, diagnostic tests, research detection tools, and even vaccines.

An Overview of Diagnostic and Management Strategies for Talaromycosis, an Underrated Disease

Underrated and neglected, talaromycosis is a life-threatening fungal disease endemic to the tropical and subtropical regions of Asia. In China, it has been reported that talaromycosis mortality doubles from 24 to 50% when the diagnosis is delayed, and reaches 100% when the diagnosis is missed. Thus, the accurate diagnosis of talaromycosis is of utmost importance. Herein, in the first part of this article, we provide an extensive review of the diagnostic tools used thus far by physicians in the management of cases of talaromycosis. The challenges encountered and the perspectives which may aid in the discovery of more accurate and reliable diagnostic approaches are also discussed. In the second part of this review, we discuss the drugs used to prevent and treat T. marneffei infection. Alternative therapeutic options and potential drug resistance reported in the contemporary literature are also discussed. We aim to guide researchers towards the discovery of novel approaches to prevent, diagnose, and treat talaromycosis, and therefore improve the prognosis for those afflicted by this important disease.

Immunologic Diagnosis of Endemic Mycoses

The endemic mycoses blastomycosis, coccidioidomycosis, histoplasmosis, paracoccidioidomycosis, cryptococcosis, sporotrichosis, talaromycosis, adiaspiromycosis, and emergomycosis are mostly caused by geographically limited thermally dimorphic fungi (except for cryptococcosis), and their diagnoses can be challenging. Usual laboratory methods involved in endemic mycoses diagnosis include microscopic examination and culture of biological samples; however, serologic, histopathologic, and molecular techniques have been implemented in the last few years for the diagnosis of these mycoses since the recovery and identification of their etiologic agents is time-consuming and lacks in sensitivity. In this review, we focus on the immunologic diagnostic methods related to antibody and antigen detection since their evidence is presumptive diagnosis, and in some mycoses, such as cryptococcosis, it is definitive diagnosis.

Talaromyces marneffei Infection: Virulence, Intracellular Lifestyle and Host Defense Mechanisms

Talaromycosis (Penicilliosis) is an opportunistic mycosis caused by the thermally dimorphic fungus Talaromyces (Penicillium) marneffei. Similar to other major causes of systemic mycoses, the extent of disease and outcomes are the results of complex interactions between this opportunistic human pathogen and a host’s immune response. This review will highlight the current knowledge regarding the dynamic interaction between T. marneffei and mammalian hosts, particularly highlighting important aspects of virulence factors, intracellular lifestyle and the mechanisms of immune defense as well as the strategies of the pathogen for manipulating and evading host immune cells.

Title of Paper: First case of subcutaneous infection by Talaromyces marneffei in a renal transplant recipient from India and review of literature

Talaromyces marneffei is one of the endemic mycoses prevalent in South-East Asian region. The infection, which was once considered to be opportunistic infection in HIV-positive patients, is establishing foothold in transplant and immunocompetent population. We report a case of a 41-year-old post-renal transplant female with a travel history to Assam two years back presenting with a subcutaneous lesion on right side of scalp associated with pain and blurring of vision in right eye. Fine-needle aspiration from the scalp lesion showed yeast cells with transverse septation in cytological examination and culture grew Talaromyces marneffei, which was confirmed by sequencing of ITS region. Patient was successfully managed with oral itraconazole 200 mg twice daily for ten months without subsequent recurrence. To our knowledge, this is the first case of subcutaneous infection by T. marneffei in a renal transplant recipient from India.

Rapid Genomic Diagnosis of Fungal Infections in the Age of Next-Generation Sequencing

Next-generation sequencing (NGS) technologies have recently developed beyond the research realm and started to mature into clinical applications. Here, we review the current use of NGS for laboratory diagnosis of fungal infections. Since the first reported case in 2014, >300 cases of fungal infections diagnosed by NGS were described. Pneumocystis jirovecii is the predominant fungus reported, constituting ~25% of the fungi detected. In ~12.5% of the cases, more than one fungus was detected by NGS. For P. jirovecii infections diagnosed by NGS, all 91 patients suffered from pneumonia and only 1 was HIV-positive. This is very different from the general epidemiology of P. jirovecii infections, of which HIV infection is the most important risk factor. The epidemiology of Talaromyces marneffei infection diagnosed by NGS is also different from its general epidemiology, in that only 3/11 patients were HIV-positive. The major advantage of using NGS for laboratory diagnosis is that it can pick up all pathogens, particularly when initial microbiological investigations are unfruitful. When the cost of NGS is further reduced, expertise more widely available and other obstacles overcome, NGS would be a useful tool for laboratory diagnosis of fungal infections, particularly for difficult-to-grow fungi and cases with low fungal loads.

Analysis of clinical characteristics and prognosis of talaromycosis (with or without human immunodeficiency virus) from a non-endemic area: a retrospective study

Purpose

Talaromyces marneffei (TM) is a pathogenic fungus endemic in Southeast Asia and human immunodeficiency virus (HIV)-positive populations, but studies related to non-endemic areas and HIV-negative populations are still limited. Therefore, this study aims to provide more additional evidence for clinical work of talaromycosis.

Methods

To collect clinical information of patients with talaromycosis admitted to hospitals in Zhejiang Province, China from January 1, 2010 to May 31, 2020, retrospectively analyzed clinical characteristics and prognosis, COX multivariate regression analysis was used for survival analysis.

Results

A total of 92 patients were enrolled, including 76 males, 73 HIV-positive patients, with an average age of 40.1 ± 13.0. Compared to HIV-positive group, the negative group had higher admission age (47.7 ± 14.6 vs 38.1 ± 11.9, p = 0.003) and lower proportion of male (89.0% vs 57.9%, p = 0.004), there was no significant difference in imaging of lungs. There were significantly more HIV-positive patients in those with pleural effusion (100% vs 69.4%, p = 0.001). COX multivariate regression analysis suggested pleural effusion (HR = 3.220; 95% CI 1.117–9.287; p = 0.030) and HIV infection (HR = 0.057; 95% CI 0.009–0.370; p = 0.003) which were independent predictors of prognosis in patients with talaromycosis.

Conclusions

In non-endemic areas, clinical symptoms, signs, and laboratory tests of patients with talaromycosis are similar to those in endemic areas. Patients with pleural effusion have lower survival rate, HIV-infected people are less likely to relapse, and there is no significant correlation between extent of lung involvement and survival of infected patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s15010-021-01679-6.

Diagnosis of Pulmonary Infections Due to Endemic Fungi

Endemic mycoses including Histoplasma, Blastomyces, Coccidioides, Paracoccidioides, and Talaromyces are dimorphic fungi that can cause a variety of clinical manifestations, including respiratory infections. Their pulmonary presentations are variable, and diagnosis is often delayed as they can mimic other infectious and non-infectious causes of pulmonary disease. Delay in diagnosis can lead to unnecessary antibiotic use, repeat hospitalizations, and increased morbidity and mortality. The diagnosis of endemic fungal pulmonary infections often relies on multiple diagnostic tests including culture, tissue histopathology, antigen assays, and antibody assays. Due to the increased use of immunosuppressive agents and the widening geographic ranges where these infections are being found, the prevalence of endemic fungal infections is increasing. Physicians need to be aware of the clinical manifestations of pulmonary infections due to endemic fungal in order to ensure that the proper diagnostic work up is obtained promptly. A high index of suspicion is particularly important in patients with suspected pulmonary infections who have failed to improve despite antibiotics in the appropriate setting. We present a review diagnostic testing for pulmonary infections due to endemic mycoses.

Antifungal activity of marine-derived actinomycetes against Talaromyces marneffei

AIMS

This study aimed to isolate actinomycetes from marine environments and examine their antifungal activity against Talaromyces marneffei both in vitro and in vivo.

METHODS AND RESULTS

Nineteen out of 101 actinomycete extracts were active and further determined for their minimum inhibitory concentrations (MIC). Three extracts of AMA50 that isolated from sediment showed strong antifungal activity against T. marneffei yeast (MICs ≤0·03-0·25 µg ml^-1 ) and mould (MICs 0·5-16 µg ml^-1 ) forms. The hexane extract from the cells of AMA50 (AMA50CH) exhibited the best activity against both the forms (MIC ≤ 1 µg ml^-1 ). Three extracts from AMA50 killed the melanized yeast cells at 0·5 µg ml^-1 . The AMA50CH was further tested for protective effects in Caenorhabditis elegans model. At concentrations of 1-8 µg ml^-1 , the AMA50CH prolonged survival of T. marneffei-infected C. elegans with a 60-70% survival rate. The composition of AMA50CH was determined by gas chromatography-mass spectrometry. The major components were n-hexadecanoic acid, tetradecanoic acid and pentadecanoic acid. Sequencing analysis revealed that isolate AMA50 belonged to the genus Streptomyces.

CONCLUSIONS

The AMA50CH from Streptomyces sp. AMA50 was the most effective extract against T. marneffei.

SIGNIFICANCE AND IMPACT OF THE STUDY

Talaromyces marneffei is one of the most important thermally dimorphic pathogenic fungi. These results indicated the potency of marine-derived actinomycete extracts against T. marneffei both in vitro and in vivo.

Diagnosis of Breakthrough Fungal Infections in the Clinical Mycology Laboratory: An ECMM Consensus Statement

Breakthrough invasive fungal infections (bIFI) cause significant morbidity and mortality. Their diagnosis can be challenging due to reduced sensitivity to conventional culture techniques, serologic tests, and PCR-based assays in patients undergoing antifungal therapy, and their diagnosis can be delayed contributing to poor patient outcomes. In this review, we provide consensus recommendations on behalf of the European Confederation for Medical Mycology (ECMM) for the diagnosis of bIFI caused by invasive yeasts, molds, and endemic mycoses, to guide diagnostic efforts in patients receiving antifungals and support the design of future clinical trials in the field of clinical mycology. The cornerstone of lab-based diagnosis of breakthrough infections for yeast and endemic mycoses remain conventional culture, to accurately identify the causative pathogen and allow for antifungal susceptibility testing. The impact of non-culture-based methods are not well-studied for the definite diagnosis of breakthrough invasive yeast infections. Non-culture-based methods have an important role for the diagnosis of breakthrough invasive mold infections, in particular invasive aspergillosis, and a combination of testing involving conventional culture, antigen-based assays, and PCR-based assays should be considered. Multiple diagnostic modalities, including histopathology, culture, antibody, and/or antigen tests and occasionally PCR-based assays may be required to diagnose breakthrough endemic mycoses. A need exists for diagnostic tests that are effective, simple, cheap, and rapid to enable the diagnosis of bIFI in patients taking antifungals.

The mycobiota of the human body: a spark can start a prairie fire

Mycobiota are inseparable from human health, shaking up the unique position held by bacteria among microorganisms. What is surprising is that this seemingly small species can trigger huge changes in the human body. Dysbiosis and invasion of mycobiota are confirmed to cause disease in different parts of the body. Meanwhile, our body also produces corresponding immune changes upon mycobiota infection. Several recent studies have made a connection between intestinal mycobiota and the human immune system. In this review, we focus on questions related to mycobiota, starting with an introduction of select species, then we summarize the typical diseases caused by mycobiota in different parts of the human body. Moreover, we constructed a framework for the human anti-fungal immune system based on genetics and immunology. Finally, the progression of fungal detection methods is also reviewed.

Diagnostic laboratory immunology for talaromycosis (penicilliosis): review from the bench-top techniques to the point-of-care testing

The pathogenic fungus Talaromyces (formerly Penicillium) marneffei is a thermally dimorphic fungus that can cause disseminated infection in patients with secondary immunodeficiency syndrome, in particular in the setting of advanced HIV infection. The areas of highest incidence are in Southeast Asia, Southern China, and Indian subcontinents. Talaromycosis (formerly penicilliosis) is identified as an AIDS-defining illness, and it has recently been recognized in non-HIV-associated patients with impaired cellular-mediated immunity. Microbiological culture is the gold standard method for the diagnosis of T. marneffei infection and usually requires up to 2-4 weeks for detectable growth to occur, which may result in a delay of appropriate treatment. Immunodiagnosis has become an alternative method for confirming talaromycosis. This article reviews various immunological tests for the diagnosis of talaromycosis, including a proposed novel rapid point-of-care assay using a new T. marneffei yeast phase-specific monoclonal antibody.

Bio-detheobromination of cocoa pod husks: reduction of ochratoxin A content without change in nutrient profile

Background

Utilization of cocoa pod husks (CPH) in animal feed is hindered by the presence of theobromine, which is variably toxic to animals. Treatment of this agro-waste to remove theobromine, while preserving its nutrient content, would allow beneficial use of the millions of metric tonnes discarded annually. The aim of this study was to assess the suitability of selected theobromine-degrading filamentous fungi for use as bio-tools in degradation of theobromine in CPH.

Results

The candidate fungi assessed in this study were an Aspergillus niger (AnTD) and three Talaromyces spp. (TmTD-1, TmTD-2, TvTD) isolates. All the fungi eliminated CPH theobromine, 0.15% w/w starting concentration, within 7 days of start of treatment, and were capable of degrading caffeine and theophylline. The fungi decreased CPH ochratoxin A content by 31–74%. Pectin was not detectable in fungus-treated CPH whereas parameters assessed for proximate composition were not affected.

Conclusions

The data provide ample evidence that the four isolates can be applied to CPH for the purpose of eliminating theobromine and decreasing ochratoxin A content without affecting nutrient profile. Comparatively, Talaromyces verruculosus TvTD was considered as most suitable for use as a bio-tool in detheobromination of CPH for animal feed.

Accuracy of rapid diagnosis of Talaromyces marneffei: A systematic review and meta-analysis

Background

To examine the accuracy of Rapid Diagnosis of Talaromyces marneffei (RDTM) in order to improve diagnosis and treatment for clinical measures and reduce the mortality due to associated infections.

Methods

In this systematic review and meta-analysis, we screened PubMed, Ovid (Cochrane library) and Web of Science, Chinese database CNKI and Wanfang for articles published between 1956 and December, 2017. Data were taken from cross-sectional studies as well as from baseline measurements in longitudinal studies with clinical follow-up. Articles were excluded if they did not contain a cohort with T. marneffei and a control cohort or a cohort with standard fungus culture. Data were extracted by two authors and checked by three for accuracy. For quality assessment, modified QUADAS-2 criteria were used.

Results

The 26 included diagnostic studies enrolled 5,594 objectives in 632 patients with T. marneffei infections and 2,612 negative controls between 1996 and 2017 in Thailand, Vietnam and China. The total combined sensitivity and specificity of rapid diagnosis of T. marneffei was 0.82 (95% CI: 0.68–0.90) and 0.99 (95% CI: 0.98–1.00). According to the experimental method, the included studies can be divided into three subgroups, including PCR-based, ELISA-based and others. The results showed these three subgroups had a highly pooled specificity of 1.00 (95% CI: 0.99–1.00), 0.99 (0.98–1.00) and 0.97 (95% CI: 0.91–1.00), respectively, while combined sensitivity was 0.84 (95% CI: 0.37–0.98), 0.82 (95% CI: 0.64–0.92) and 0.77 (95% CI: 0.54–0.91), respectively.

Conclusions

Although serological methods with a high specificity is essential for potential rapid diagnostic, false-negative results can be obtained in the serum samples, there is no suitable rapid serological test to refer to as is the case with TM infection.

Development and evaluation of a real‐time polymerase chain reaction assay for the rapid detection of Talaromyces marneffei MP1 gene in human plasma

Penicilliosis caused by Talaromyces marneffei is a common AIDS‐defining illness in South and Southeast Asia. Diagnosis is based on culture which can take up to 14 days for identification, leading to treatment delay and increased mortality. We developed a TaqMan real‐time PCR assay targeting the MP1 gene encoding an abundant cell wall protein specific to T. marneffei. The assay's performance was evaluated in MP1‐containing plasmids, clinical isolates, and plasma from HIV‐infected patients with and without penicilliosis. The assay consistently detected 10 copies of MP1‐containing plasmids per reaction and 100 T. marneffei yeast cells per millilitre plasma. There were no amplification with seven other Penicillium species and six other HIV‐associated fungal pathogens tested. The assay was evaluated in 70 patients with AIDS: 50 patients with culture‐confirmed penicilliosis and 20 patients with opportunistic infections other than penicilliosis. The diagnostic sensitivity was 70.4% (19/27, 95% CI: 51.5–84.1%) and 52.2% (12/23, 95% CI: 33.0–70.8%) in plasma samples collected prior to and within 48 h of antifungal therapy respectively. The diagnostic specificity was 100% (20/20, 95% CI: 83.9–100%). This assay provides a useful tool for the rapid diagnosis of T. marneffei infection and has the potential to improve the management of patients with penicilliosis.

Mp1p Is a Virulence Factor in Talaromyces (Penicillium) marneffei

Background

Talaromyces marneffei is an opportunistic dimorphic fungus prevalent in Southeast Asia. We previously demonstrated that Mp1p is an immunogenic surface and secretory mannoprotein of T. marneffei. Since Mp1p is a surface protein that can generate protective immunity, we hypothesized that Mp1p and/or its homologs are virulence factors.

Methodology/Principal Findings

We examined the pathogenic roles of Mp1p and its homologs in a mouse model. All mice died 21 and 30 days after challenge with wild-type T. marneffei PM1 and MP1 complemented mutant respectively. None of the mice died 60 days after challenge with MP1 knockout mutant (P<0.0001). Seventy percent of mice died 60 days after challenge with MP1 knockdown mutant (P<0.0001). All mice died after challenge with MPLP1 to MPLP13 knockdown mutants, suggesting that only Mp1p plays a significant role in virulence. The mean fungal loads of PM1 and MP1 complemented mutant in the liver, lung, kidney and spleen were significantly higher than those of the MP1 knockout mutant. Similarly, the mean load of PM1 in the liver, lung and spleen were significantly higher than that of the MP1 knockdown mutant. Histopathological studies showed an abundance of yeast in the kidney, spleen, liver and lung with more marked hepatic and splenic necrosis in mice challenged with PM1 compared to MP1 knockout and MP1 knockdown mutants. Likewise, a higher abundance of yeast was observed in the liver and spleen of mice challenged with MP1 complemented mutant compared to MP1 knockout mutant. PM1 and MP1 complemented mutant survived significantly better than MP1 knockout mutant in macrophages at 48 hours (P<0.01) post-infection. The mean fungal counts of Pichia pastoris GS115-MP1 in the liver (P<0.001) and spleen (P<0.05) of mice were significantly higher than those of GS115 at 24 hours post-challenge.

Conclusions/Significance

Mp1p is a key virulence factor of T. marneffei. Mp1p mediates virulence by improving the survival of T. marneffei in macrophages.

Talaromyces (Penicillium) marneffei is an opportunistic thermal dimorphic fungus most prevalent in Southeast Asia. Our team has previously shown that Mp1p, a protein encoded by the MP1 gene, is an immunogenic surface and secretory protein of T. marneffei. In this study, we showed that mice challenged with T. marneffei with the MP1 gene died but those challenged with T. marneffei without the MP1 gene did not die. There was also significantly higher fungal load and more necrosis in organs of mice challenged with T. marneffei with the MP1 gene than T. marneffei without the MP1 gene. Furthermore, T. marneffei with the MP1 gene survived better in macrophages than T. marneffei without the MP1 gene and Pichia pastoris with the MP1 gene survived in mice better than P. pastoris without the MP1 gene. Our data support that Mp1p is a key virulence factor of T. marneffei and Mp1p mediates virulence by improving the survival of T. marneffei in macrophages.

Development and evaluation of a real-time polymerase chain reaction assay for the rapid detection of Talaromyces marneffei MP1 gene in human plasma

Penicilliosis caused by Talaromyces marneffei is a common AIDS‐defining illness in South and Southeast Asia. Diagnosis is based on culture which can take up to 14 days for identification, leading to treatment delay and increased mortality. We developed a TaqMan real‐time PCR assay targeting the MP1 gene encoding an abundant cell wall protein specific to T. marneffei. The assay's performance was evaluated in MP1‐containing plasmids, clinical isolates, and plasma from HIV‐infected patients with and without penicilliosis. The assay consistently detected 10 copies of MP1‐containing plasmids per reaction and 100 T. marneffei yeast cells per millilitre plasma. There were no amplification with seven other Penicillium species and six other HIV‐associated fungal pathogens tested. The assay was evaluated in 70 patients with AIDS: 50 patients with culture‐confirmed penicilliosis and 20 patients with opportunistic infections other than penicilliosis. The diagnostic sensitivity was 70.4% (19/27, 95% CI: 51.5–84.1%) and 52.2% (12/23, 95% CI: 33.0–70.8%) in plasma samples collected prior to and within 48 h of antifungal therapy respectively. The diagnostic specificity was 100% (20/20, 95% CI: 83.9–100%). This assay provides a useful tool for the rapid diagnosis of T. marneffei infection and has the potential to improve the management of patients with penicilliosis.

Talaromyces (Penicillium) marneffei infection in non-HIV-infected patients

Talaromyces (Penicillium) marneffei is an important pathogenic thermally dimorphic fungus causing systemic mycosis in Southeast Asia. The clinical significance of T. marneffei became evident when the human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome epidemic arrived in Southeast Asia in 1988. Subsequently, a decline in the incidence of T. marneffei infection among HIV-infected patients was seen in regions with access to highly active antiretroviral therapy and other control measures for HIV. Since the 1990s, an increasing number of T. marneffei infections have been reported among non-HIV-infected patients with impaired cell-mediated immunity. Their comorbidities included primary adult-onset immunodeficiency due to anti-interferon-gamma autoantibodies and secondary immunosuppressive conditions including other autoimmune diseases, solid organ and hematopoietic stem cell transplantations, T-lymphocyte-depleting immunsuppressive drugs and novel anti-cancer targeted therapies such as anti-CD20 monoclonal antibodies and kinase inhibitors. Moreover, improved immunological diagnostics identified more primary immunodeficiency syndromes associated with T. marneffei infection in children. The higher case-fatality rate of T. marneffei infection in non-HIV-infected than HIV-infected patients might be related to delayed diagnosis due to the lack of clinical suspicion. Correction of the underlying immune defects and early use of antifungals are important treatment strategies. Clinicians should be familiar with the changing epidemiology and clinical management of T. marneffei infection among non-HIV-infected patients.

A novel inhibition ELISA for the detection and monitoring of Penicillium marneffei antigen in human serum

The thermally dimorphic fungus Penicillium marneffei is a causative agent of penicilliosis marneffei, a disease considered to be an acquired immune deficiency syndrome (AIDS)-defining illness in Southeast Asia and southern China. We have developed an inhibition enzyme-linked immunosorbent assay (inh-ELISA) incorporating the yeast phase specific mannoprotein-binding monoclonal antibody 4D1 for the detection of P. marneffei infection. In our sample set, the test detected antigenemia in all 45 (100 %) patients with P. marneffei, with a mean antigen concentration of 4.32 μg/ml. No cross-reactivity in this assay was found using serum from 44 additional patients with other fungal infections, such as Aspergillus fumigatus, Cryptococcus neoformans, and Candida albicans, as well as 44 patients with bacterial infections, such as Mycobacterium tuberculosis and Streptococcus suis. Additionally, no reactivity occurred using serum from 31 human immunodeficiency virus (HIV)-infected patients without a history of fungal infections and 113 healthy controls residing in endemic areas. To investigate the potential of the inh-ELISA for disease monitoring, we followed the reduction in antigenemia in six patients who clinically responded to itraconazole and P. marneffei was no longer isolated from their blood or tissues. In contrast, we correlated increased concentrations of antigenemia in patients with relapsed P. marneffei infection with the progression of their clinical symptoms and the isolation of P. marneffei from their clinical specimens. In summary, the P. marneffei inh-ELISA is a promising new assay for the rapid diagnosis of P. marneffei, as well as a tool for evaluating clinical response and clearance of the fungus during treatment.

Serological surveillance for Penicillium marneffei infection in HIV-infected patients during 2004-2011 in Guangzhou, China

Prevalence of disseminated Penicillium marneffei infection is not known in human immunodeficiency virus (HIV)-infected patients. This retrospective study aimed to evaluate the prevalence of and risk factors for disseminated P. marneffei infection in HIV-infected patients during 2004-11 in Guangzhou, China. We tested 8131 archived HIV-infected patient serum samples for P. marneffei-specific mannoprotein (Mp1p) antigen using a highly sensitive and specific ELISA that we previously established. The CD4 count of 2686 cases was determined by flow cytometry. Logistic regression was used to assess predictors of Mp1p antigenaemia. The overall prevalence of disseminated penicilliosis as detected by positive serum Mp1p antigen was 9.36% (761/8131), in good concordance with Platelia™ Aspergillus immunoassay. During 2004-11, the prevalence increased to a peak of 12.58% (158/1256) in 2010 and decreased in 2011. Penicilliosis was strongly associated with progression from HIV to AIDS (OR 4.66, 95% CI 3.94-5.51, p <0.001) and humidity (OR 1.02, 95% CI 1.01-1.03, p 0.002). Disseminated penicilliosis occurred mainly during the rainy seasons (p <0.001). For 2686 cases with known CD4 count, logistic regression showed that CD4 count of <200 cells/μL was a risk factor for penicilliosis (OR 2.90, 95% CI 1.10-7.66, p 0.032), especially when it was <50 cells/μL (OR 24.26, 95% CI 10.63-55.36, p <0.001) during which 28.06% of patients developed disseminated penicilliosis. In conclusion, approximately 9.36% of the HIV-infected patients in our study developed disseminated penicilliosis. Rapid diagnosis may be achieved by performing serological surveillance for Mp1p antigenaemia as a routine procedure for all HIV-infected patients with CD4 count of <50 cells/μL.

Immunodetection of fungal and oomycete pathogens: established and emerging threats to human health, animal welfare and global food security

Filamentous fungi (moulds), yeast-like fungi, and oomycetes cause life-threatening infections of humans and animals and are a major constraint to global food security, constituting a significant economic burden to both agriculture and medicine. As well as causing localized or systemic infections, certain species are potent producers of allergens and toxins that exacerbate respiratory diseases or cause cancer and organ damage. We review the pathogenic and toxigenic organisms that are etiologic agents of both animal and plant diseases or that have recently emerged as serious pathogens of immunocompromised individuals. The use of hybridoma and phage display technologies and their success in generating monoclonal antibodies for the detection and control of fungal and oomycete pathogens are explored. Monoclonal antibodies hold enormous potential for the development of rapid and specific tests for the diagnosis of human mycoses, however, unlike plant pathology, their use in medical mycology remains to be fully exploited.

Tobacco mosaic virus in the lungs of mice following intra-tracheal inoculation

Plant viruses are generally considered incapable of infecting vertebrates. Accordingly, they are not considered harmful for humans. However, a few studies questioned the certainty of this paradigm. Tobacco mosaic virus (TMV) RNA has been detected in human samples and TMV RNA translation has been described in animal cells. We sought to determine if TMV is detectable, persists, and remains viable in the lung tissues of mice following intratracheal inoculation, and we attempted to inoculate mouse macrophages with TMV. In the animal model, mice were intratracheally inoculated with 10(11) viral particles and were sacrificed at different time points. The virus was detected in the mouse lungs using immunohistochemistry, electron microscopy, real-time RT-PCR and sequencing, and its viability was studied with an infectivity assay on plants. In the cellular model, the culture medium of murine bone marrow derived macrophages (BMDM) was inoculated with different concentrations of TMV, and the virus was detected with real-time RT-PCR and immunofluorescence. In addition, anti-TMV antibodies were detected in mouse sera with ELISA. We showed that infectious TMV could enter and persist in mouse lungs via the intratracheal route. Over 14 days, the TMV RNA level decreased by 5 log(10) copies/ml in the mouse lungs and by 3.5 log(10) in macrophages recovered from bronchoalveolar lavage. TMV was localized to lung tissue, and its infectivity was observed on plants until 3 days after inoculation. In addition, anti-TMV antibody seroconversions were observed in the sera from mice 7 days after inoculation. In the cellular model, we observed that TMV persisted over 15 days after inoculation and it was visualized in the cytoplasm of the BMDM. This work shows that a plant virus, Tobacco mosaic virus, could persist and enter in cells in mammals, which raises questions about the potential interactions between TMV and human hosts.

Morphogenetic circuitry regulating growth and development in the dimorphic pathogen Penicillium marneffei

Penicillium marneffei is an emerging human-pathogenic fungus endemic to Southeast Asia. Like a number of other fungal pathogens, P. marneffei exhibits temperature-dependent dimorphic growth and grows in two distinct cellular morphologies, hyphae at 25°C and yeast cells at 37°C. Hyphae can differentiate to produce the infectious agents, asexual spores (conidia), which are inhaled into the host lung, where they are phagocytosed by pulmonary alveolar macrophages. Within macrophages, conidia germinate into unicellular yeast cells, which divide by fission. This minireview focuses on the current understanding of the genes required for the morphogenetic control of conidial germination, hyphal growth, asexual development, and yeast morphogenesis in P. marneffei.

Immunoassays based on Penicillium marneffei Mp1p derived from Pichia pastoris expression system for diagnosis of penicilliosis

Background

Penicillium marneffei is a dimorphic fungus endemic in Southeast Asia. It can cause fatal penicilliosis in humans, particularly in HIV-infected people. Diagnosis of this infection is difficult because its clinical manifestations are not distinctive. Specialized laboratory tests are necessary to establish a definitive diagnosis for successful management. We have demonstrated previously that a cell wall mannoprotein Mp1p, abundant in P. marneffei, is a potential biomarker for diagnosis of P. marneffei infections. In the present study, we describe immunoassays based on Mp1p derived from the yeast Pichia pastoris expression system.

Methodology/Principal Findings

We generated monoclonal antibodies (MAbs) and rabbit polyclonal antibodies (PAbs) against Mp1p expressed in P. pastoris. Subsequently, we developed two Mp1p antigen capture ELISAs which employed MAbs for both the capture and detecting antibodies (MAb-MAb pair) or PAbs and MAbs as the capture and detecting antibodies (PAbs-MAb pair) respectively. The two Mp1p antigen ELISAs detected Mp1p specifically in cultures of P. marneffei yeast phase at 37–40°C and had no cross-reaction with other tested pathogenic fungi. The sensitivities and specificities of the two antigen assays were found to be 55% (11/20) and 99.6% (538/540) for MAb-MAb Mp1p ELISA, and 75% (15/20) and 99.4% (537/540) for PAbs-MAb Mp1p ELISA performed using 20 sera with culture-confirmed penicilliosis, and 540 control sera from 15 other mycosis patients and 525 healthy donors. Meanwhile, we also developed an anti-Mp1p IgG antibody ELISA with an evaluated sensitivity of 30% (6/20) and a specificity of 98.5% (532/540) using the same sera. Furthermore, combining the results of Mp1p antigen and antibody detection improved the sensitivity of diagnosis to 100% (20/20).

Conclusions/Significance

Simultaneous detection of antigen and antibody using the immunoassays based on Mp1p derived from P. pastoris greatly improves detection sensitivity. The procedures should be useful for the routine diagnosis of penicilliosis.

Penicillium marneffei Infection in AIDS

Penicillium marneffei is a dimorphic fungus which is endemic in Southeast Asia. It is an opportunistic pathogen which has emerged to become an AIDS-defining illness in the endemic areas. Early diagnosis with prompt initiation of treatment is crucial for its management. Prompt diagnosis can often be established through careful cytological and histological examination of clinical specimens although microbiological culture remains the gold standard for its diagnosis. Standard antifungal treatment for AIDS patients with penicilliosis is well established. Highly active antiretroviral therapy should be started early together with the antifungal treatment. Special attention should be paid to potential drug interaction between antiretroviral and antifungal treatments. Secondary prophylaxis may be discontinued with a low risk of relapse of the infection once the immune dysfunction has improved.

Characterization of an MPLP6, a gene coding for a yeast phase specific, antigenic mannoprotein in Penicillium marneffei

A gene encoding an antigenic mannoprotein of Penicillium marneffei, MPLP6, was isolated by an antibody screening approach and characterized. The polypeptide chain containing deduced 220 amino acids has a predicted molecular mass of 24 kDa. It has high similarity to Mp1p, the first mannoprotein antigen isolated from P. marneffei. The polypeptide sequence presents the property of cell wall mannoproteins by containing a putative N-terminal signal peptide and potential O-linked glycosylation sites. However, absence of a GPI-anchored signal sequence suggested that this protein is secreted. The MPLP6 transcript was present specifically in the pathogenic yeast form. The transcript was completely absent in the mold phase and conidia. The fusion protein produced in E. coli was Western immunoblotted with P. marneffei-infected human sera and 95% of the patients' sera were positive in the assay. None of the sera obtained from patients with aspergillosis, tuberculosis, histoplasmosis or cryptococcosis tested positive. These results suggest that Mplp6 can be used as a marker in a serodiagnostic assay.

Crystal structure of the Mp1p ligand binding domain 2 reveals its function as a fatty acid-binding protein

Penicillium marneffei is a dimorphic, pathogenic fungus in Southeast Asia that mostly afflicts immunocompromised individuals. As the only dimorphic member of the genus, it goes through a phase transition from a mold to yeast form, which is believed to be a requisite for its pathogenicity. Mp1p, a cell wall antigenic mannoprotein existing widely in yeast, hyphae, and conidia of the fungus, plays a vital role in host immune response during infection. To understand the function of Mp1p, we have determined the x-ray crystal structure of its ligand binding domain 2 (LBD2) to 1.3 A. The structure reveals a dimer between the two molecules. The dimer interface forms a ligand binding cavity, in which electron density was observed for a palmitic acid molecule interacting with LBD2 indirectly through hydrogen bonding networks via two structural water molecules. Isothermal titration calorimetry experiments measured the ligand binding affinity (K(d)) of Mp1p at the micromolar level. Mutations of ligand-binding residues, namely S313A and S332A, resulted in a 9-fold suppression of ligand binding affinity. Analytical ultracentrifugation assays demonstrated that both LBD2 and Mp1p are mostly monomeric in vitro, no matter with or without ligand, and our dimeric crystal structure of LBD2 might be the result of crystal packing. Based on the conformation of the ligand-binding pocket in the dimer structure, a model for the closed, monomeric form of LBD2 is proposed. Further structural analysis indicated the biological importance of fatty acid binding of Mp1p for the survival and pathogenicity of the conditional pathogen.

Current status and future perspectives on molecular and serological methods in diagnostic mycology

Invasive fungal infections are an important cause of infectious morbidity. Nonculture-based methods are increasingly used for rapid, accurate diagnosis to improve patient outcomes. New and existing DNA amplification platforms have high sensitivity and specificity for direct detection and identification of fungi in clinical specimens. Since laboratories are increasingly reliant on DNA sequencing for fungal identification, measures to improve sequence interpretation should support validation of reference isolates and quality control in public gene repositories. Novel technologies (e.g., isothermal and PNA FISH methods), platforms enabling high-throughput analyses (e.g., DNA microarrays and Luminex® xMAP™) and/or commercial PCR assays warrant further evaluation for routine diagnostic use. Notwithstanding the advantages of molecular tests, serological assays remain clinically useful for patient management. The serum Aspergillus galactomannan test has been incorporated into diagnostic algorithms of invasive aspergillosis. Both the galactomannan and the serum β-D-glucan test have value for diagnosing infection and monitoring therapeutic response.

Transmission of tropical and geographically restricted infections during solid-organ transplantation

In recent years, the increasing number of donors from different regions of the world is providing a new challenge for the management and selection of suitable donors. This is a worldwide problem in most countries with transplantation programs, especially due to the increase in immigration and international travel. This paper elaborates recommendations regarding the selection criteria for donors from foreign countries who could potentially transmit tropical or geographically restricted infections to solid-organ transplant recipients. For this purpose, an extensive review of the medical literature focusing on viral, fungal, and parasitic infections that could be transmitted during transplantation from donors who have lived or traveled in countries where these infections are endemic has been performed, with special emphasis on tropical and imported infections. The review also includes cases described in the literature as well as risks of transmission during transplantation, microbiological tests available, and recommendations for each infection. A table listing different infectious agents with their geographic distributions and specific recommendations is included.

MP1 homologue-based multilocus sequence system for typing the pathogenic fungus Penicillium marneffei: a novel approach using lineage-specific genes

A highly reproducible and discriminative typing system is essential for better understanding of the epidemiology of Penicillium marneffei, the most important thermal dimorphic fungus causing respiratory, skin, and systemic mycosis in Southeast Asia. The sequences of 11 housekeeping genes were identical among 10 strains of P. marneffei, but those of MP1 and its 13 homologues, a novel superfamily of mannoproteins in the subdivision Pezizomycotina of Ascomycetes, mostly species of Penicillium and Aspergillus, showed significant variations. Therefore, a multilocus sequence typing (MLST) system for P. marneffei was constructed using MP1 (549 bp) and the four of its homologues (MPLP4 [337 bp], MPLP7 [347 bp], MPLP10 [546 bp], and MPLP13 [422 bp]) that showed the greatest variations. Among the 2,201 bp of the five loci, 183 polymorphic sites were observed in 44 strains of P. marneffei. The median number of alleles at each locus was five (range, 5 [MPLP4, MPLP7, and MPLP13] to 15 [MPLP10]). Four of the five genes had nonsynonymous substitution/synonymous substitution (d(n)/d(s)) ratios of >1. A total of 35 different sequence types (STs) were assigned to the 44 P. marneffei isolates, with 28 of the 35 STs identified only once. The discriminatory power was 0.9884. MP1 and its homologues were better than housekeeping genes for MLST in P. marneffei. Due to their more rapid evolutionary rates, lineage-specific genes may be better candidates than housekeeping genes for sequence-based typing, especially in microbes that evolve slowly or have evolved recently.

Nucleotide sequence-based analysis for determining the molecular epidemiology of Penicillium marneffei

The dimorphic fungus, Penicillium marneffei, is an emerging opportunistic pathogen endemic in Southeast Asia, especially for those with impaired cellular immunity such as human immunodeficiency virus-infected persons. A discriminatory and reproducible method based on the analysis of nucleotide sequences would facilitate epidemiologic investigations of this fungus. Twenty-four clinical or environmental isolates of P. marneffei obtained from China, Thailand, and Vietnam were analyzed by nucleotide sequence analysis. A total of 3,803 bp, consisting of eight nuclear gene fragments (transcription factor [AbaA], catalase [CpeA]], homodomain transcription factor [StlA], isocitrate lyase [Icl1], polyaromatic amino acid biosynthesis [PAA], NADH-dependent glutamate synthase [NGS], lovastatin nonaketide synthase [LNS], a cell wall mannoprotein [MP1], and a gene fragment of the cytochrome oxidase subunit 1 gene [COX1] of the P. marneffei mitochondrial genome) were amplified by PCR and then sequenced. No polymorphic sites within the Cox1 gene fragment were observed. Likewise, no nucleotide sequence polymorphisms were observed for three gene fragments: StlA, AbaA, and NGS. Seven single-nucleotide polymorphisms were observed for three gene fragments, Icl1, CpeA, and PAA, providing only a low degree of discriminatory power (D = 0.747). In contrast, the gene fragment for an antigenic cell wall glycoprotein, MP1, a useful immunologic marker for infection, was observed to be highly polymorphic with 12 different MP1 types (D = 0.887). Single-nucleotide polymorphisms were observed at 21 different locations in the MP1 gene fragment. Indels of 3, 21, 24, and 42 bp were observed and were in frame for protein translation. The relatively high degree of MP1 polymorphisms suggests the sequence is rapidly evolving in order to evade host immune responses. After all polymorphic gene sequences were combined, a high degree of genetic variation was observed (D = 0.949) for a total of 16 different haploid sequence types with 11 genotypes represented by single isolates. Phylogenetic analysis detected clusters composed of isolates obtained only from China or Thailand, as well as clusters with a combination of isolates from these two countries, indicating some mixing or common descent. Identical sequences were observed for isolates passed in vitro for 8 weeks, suggesting good reproducibility. The low degree of nucleotide diversity in housekeeping and regulatory genes suggests the recent emergence and spread as a species or an evolutionary bottleneck. In summary, multilocus sequence typing demonstrated a high degree of discriminatory power and reproducibility and may provide a robust and reliable adjunct method for genotyping isolates of P. marneffei and facilitating interlaboratory comparisons.

A novel approach for screening immunogenic proteins inPenicillium marneffeiusing the ΔAFMP1ΔAFMP2deletion mutant ofAspergillus fumigatus

Using serum from guinea-pigs immunized with a DeltaAFMP1DeltaAFMP2 deletion mutant of Aspergillus fumigatus to screen a cDNA library of A. fumigatus, we cloned a novel immunogenic 57-kDa protein in A. fumigatus. We also cloned its 55-kDa homologue in Penicillium marneffei, which was possibly related to amino acid biosynthesis and metabolism, with homologues present only in the subphylum Pezizomycotina of Ascomycota. The recombinant 55-kDa protein of P. marneffei reacted strongly with guinea-pig serum immunized with P. marneffei and with the sera of patients with P. marneffei infection. A similar approach could be applied to immunogenic protein screening in other microorganisms for serological diagnosis, epidemiological studies and the study of vaccines.

Genomic and experimental evidence for a potential sexual cycle in the pathogenic thermal dimorphic fungus Penicillium marneffei

All meiotic genes (except HOP1) and genes encoding putative pheromone processing enzymes, pheromone receptors and pheromone response pathways proteins in Aspergillus fumigatus and Aspergillus nidulans and a putative MAT-1 alpha box mating-type gene were present in the Penicillium marneffei genome. A putative MAT-2 high-mobility group mating-type gene was amplified from a MAT-1 alpha box mating-type gene-negative P. marneffei strain. Among 37 P. marneffei patient strains, MAT-1 alpha box and MAT-2 high-mobility group mating-type genes were present in 23 and 14 isolates, respectively. We speculate that P. marneffei can potentially be a heterothallic fungus that does not switch mating type.

Penicillium marneffei infection and recent advances in the epidemiology and molecular biology aspects

Penicillium marneffei infection is an important emerging public health problem, especially among patients infected with human immunodeficiency virus in the areas of endemicity in southeast Asia, India, and China. Within these regions, P. marneffei infection is regarded as an AIDS-defining illness, and the severity of the disease depends on the immunological status of the infected individual. Early diagnosis by serologic and molecular assay-based methods have been developed and are proving to be important in diagnosing infection. The occurrence of natural reservoirs and the molecular epidemiology of P. marneffei have been studied; however, the natural history and mode of transmission of the organism remain unclear. Soil exposure, especially during the rainy season, has been suggested to be a critical risk factor. Using a highly discriminatory molecular technique, multilocus microsatellite typing, to characterize this fungus, several isolates from bamboo rats and humans were shown to share identical multilocus genotypes. These data suggest either that transmission of P. marneffei may occur from rodents to humans or that rodents and humans are coinfected from common environmental sources. These putative natural cycles of P. marneffei infection need further investigation. Studies on the fungal genetics of P. marneffei have been focused on the characterization of genetic determinants that may play important roles in asexual development, mycelial-to-yeast phase transition, and the expression of antigenic determinants. Molecular studies have identified several genes involved in germination, hyphal development, conidiogenesis, and yeast cell polarity. A number of functionally important genes, such as the malate synthase- and catalase-peroxidase protein-encoding genes, have been identified as being upregulated in the yeast phase. Future investigations pertaining to the roles of these genes in host-fungus interactions may provide the key knowledge to understanding the pathogenicity of P. marneffei.

Serodiagnosis of mycoses using recombinant antigens

The early diagnosis of mycoses is important for the institution of an effective antifungal therapy. Detection of antibodies against crude antigenic extracts is one of the standard techniques for the diagnosis of most mycoses. However, while these crude antigenic extracts are relatively easy to obtain, they usually show low reproducibility and are not very specific, since antibodies from patients with different mycoses may show cross-reactivity. The application of molecular biology techniques to the study of fungal antigens has allowed the production of recombinant antigens that may help to solve these problems. The purpose of this review is to discuss the use of recombinant fungal antigens in the diagnosis of mycoses.

Detection of specific antibodies to severe acute respiratory syndrome (SARS) coronavirus nucleocapsid protein for serodiagnosis of SARS coronavirus pneumonia

We report the evaluation of recombinant severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) nucleocapsid protein enzyme-linked immunosorbent assay (ELISA)-based antibody tests for serodiagnosis of SARS-CoV pneumonia and compare the sensitivities and specificities of this ELISA for detection of immunoglobulin G (IgG), IgM, IgA, and their combinations with serum samples from 149 healthy blood donors who donated blood 3 years ago as controls and 106 SARS-CoV pneumonia patients in Hong Kong. The specificities of the ELISA for IgG, IgM, and IgA detection were 95.3, 96.6, and 96.6%, respectively, with corresponding sensitivities of 94.3, 59.4, and 60.4%, respectively. The present ELISA appears to be a sensitive test for serodiagnosis of SARS-CoV pneumonia, is much more economical and less labor-intensive than the indirect immunofluorescence assay, and does not require cultivation of SARS-CoV.

AFMP2 encodes a novel immunogenic protein of the antigenic mannoprotein superfamily in Aspergillus fumigatus

We cloned the Aspergillus fumigatus mannoprotein 2 (AFMP2) gene, which encodes a novel immunogenic protein (Afmp2p) of the antigenic mannoprotein superfamily, in A. fumigatus. Sequence analysis revealed that Afmp2p has 510 amino acid residues, with a predicted molecular mass of 51.5 kDa. Afmp2p has a putative N-terminal signal peptide, a putative C-terminal glycosylphosphatidylinositol membrane attachment signal sequence, and an upstream GAA cleavage site commonly used for cytoplasmic membrane attachment and implicated in fungal cell wall assembly. Upstream of the GAA cleavage site, Afmp2p contains a 302-amino-acid serine- and threonine-rich region as a site for potential O-glycosylation. Within this serine- and threonine-rich region, 13 repeats of ETSTPCE(T)(n) were observed. Western blot analysis of Afmp2p in A. fumigatus fungal cell lysate and culture supernatant and immunogold staining and electron microscopy showed that Afmp2p is predominantly secreted into the culture supernatant, whereas only minimal amounts can be detected in the cell lysate and cell wall. Finally, it was observed that patients with aspergilloma and invasive aspergillosis due to A. fumigatus develop a specific antibody response against recombinant Afmp2p. The abundance of Afmp2p in secreted form, its minimal cross-reactivity with Afmp1p, and the presence of an antibody response against Afmp2p in patients with A. fumigatus infections suggest that Afmp2p is a good candidate for complementing Afmp1p in serodiagnosis of A. fumigatus infections.

Relative rates of non-pneumonic SARS coronavirus infection and SARS coronavirus pneumonia

BACKGROUND

Although the genome of severe acute respiratory syndrome coronavirus (SARS-CoV) has been sequenced and a possible animal reservoir identified, seroprevalence studies and mass screening for detection of subclinical and non-pneumonic infections are still lacking.

METHODS

We cloned and purified the nucleocapsid protein and spike polypeptide of SARS-CoV and examined their immunogenicity with serum from patients with SARS-CoV pneumonia. An ELISA based on recombinant nucleocapsid protein for IgG detection was tested with serum from 149 healthy blood donors who donated 3 years previously and with serum positive for antibodies against SARS-CoV (by indirect immunofluorescence assay) from 106 patients with SARS-CoV pneumonia. The seroprevalence of SARS-CoV was studied with the ELISA in healthy blood donors who donated during the SARS outbreak in Hong Kong, non-pneumonic hospital inpatients, and symptom-free health-care workers. All positive samples were confirmed by two separate western-blot assays (with recombinant nucleocapsid protein and recombinant spike polypeptide).

FINDINGS

Western-blot analysis showed that the nucleocapsid protein and spike polypeptide of SARS-CoV are highly immunogenic. The specificity of the IgG antibody test (ELISA with positive samples confirmed by the two western-blot assays) was 100%, and the sensitivity was 94.3%. Three of 400 healthy blood donors who donated during the SARS outbreak and one of 131 non-pneumonic paediatric inpatients were positive for IgG antibodies, confirmed by the two western-blot assays (total, 0.48% of our study population).

INTERPRETATION

Our findings support the existence of subclinical or non-pneumonic SARS-CoV infections. Such infections are more common than SARS-CoV pneumonia in our locality.

The mitochondrial genome of the thermal dimorphic fungus Penicillium marneffei is more closely related to those of molds than yeasts

We report the complete sequence of the mitochondrial genome of Penicillium marneffei, the first complete mitochondrial DNA sequence of a thermal dimorphic fungus. This 35 kb mitochondrial genome contains the genes encoding ATP synthase subunits 6, 8, and 9 (atp6, atp8, and atp9), cytochrome oxidase subunits I, II, and III (cox1, cox2, and cox3), apocytochrome b (cob), reduced nicotinamide adenine dinucleotide ubiquinone oxireductase subunits (nad1, nad2, nad3, nad4, nad4L, nad5, and nad6), ribosomal protein of the small ribosomal subunit (rps), 28 tRNAs, and small and large ribosomal RNAs. Analysis of gene contents, gene orders, and gene sequences revealed that the mitochondrial genome of P. marneffei is more closely related to those of molds than yeasts.

Exploring the Penicillium marneffei genome

Penicillium marneffei is a dimorphic fungus that intracellularly infects the reticuloendothelial system of humans and bamboo rats. Endemic in Southeast Asia, it infects 10% of AIDS patients in this region. The absence of a sexual stage and the highly infectious nature of the mould-phase conidia have impaired studies on thermal dimorphic switching and host-microbe interactions. Genomic analysis, therefore, could provide crucial information. Pulsed-field gel electrophoresis of genomic DNA of P. marneffei revealed three or more chromosomes (5.0, 4.0, and 2.2 Mb). Telomeric fingerprinting revealed 6-12 bands, suggesting that there were chromosomes of similar sizes. The genome size of P. marneffei was hence about 17.8-26.2 Mb. G+C content of the genome is 48.8 mol%. Random exploration of the genome of P. marneffei yielded 2303 random sequence tags (RSTs), corresponding to 9% of the genome, with 11.7, 6.3, and 17.4% of the RSTs having sequence similarity to yeast-specific sequences, non-yeast fungus sequences, and both (common sequences), respectively. Analysis of the RSTs revealed genes for information transfer (ribosomal protein genes, tRNA synthetase subunits, translation initiation, and elongation factors), metabolism, and compartmentalization, including several multi-drug-resistance protein genes and homologues of fluconazole-resistance gene. Furthermore, the presence of genes encoding pheromone homologues and ankyrin repeat-containing proteins of other fungi and algae strongly suggests the presence of a sexual stage that presumably exists in the environment.

AFLMP1 encodes an antigenic cel wall protein in Aspergillus flavus

We have previously reported the cloning and characterization of the MP1 gene in Penicillium marneffei and the AFMP1 gene in Aspergillus fumigatus and their use for serodiagnosis of penicilliosis and aspergilloma and invasive aspergillosis, respectively. In this study, we describe the cloning of the AFLMP1 gene, which encodes the homologous antigenic cell wall protein in Aspergillus flavus, the most common Aspergillus species associated with human disease in our locality and in other Asian countries and the second most common Aspergillus species associated with human disease in Western countries. AFLMP1 codes for a protein, Aflmp1p, of 273 amino acid residues, with a few sequence features that are present in Mp1p and Afmp1p, the homologous antigenic cell wall proteins in P. marneffei and A. fumigatus, respectively, as well as several other cell wall proteins of Saccharomyces cerevisiae and Candida albicans. It contains a serine- and threonine-rich region for O glycosylation, a signal peptide, and a putative glycosylphosphatidylinositol attachment signal sequence. Specific anti-Aflmp1p antibody was generated with recombinant Aflmp1p protein purified from Escherichia coli to allow further characterization of Aflmp1p. Indirect immunofluorescence analysis indicated that Aflmp1p is present on the surface of the hyphae of A. flavus. Finally, it was observed that patients with aspergilloma and invasive aspergillosis due to A. flavus develop a specific antibody response against Aflmp1p. This suggested that the recombinant protein and its antibody may be useful for serodiagnosis in patients with aspergilloma or invasive aspergillosis, and the protein may represent a good cell surface target for host humoral immunity.

Detection of cell wall galactomannoprotein Afmp1p in culture supernatants of Aspergillus fumigatus and in sera of aspergillosis patients

Mannoproteins are important and abundant structural components of fungal cell walls. The AFMP1 gene encodes a cell wall galactomannoprotein of Aspergillus fumigatus. In the present study, we show that Afmp1p is secreted into the cell culture supernatant at a level that can be detected by Western blotting. A sensitive enzyme-linked immunosorbent assay (ELISA) developed with antibodies against Afmp1p was capable of detecting this protein from the cell culture supernatant of A. fumigatus. The anti-Afmp1p antibody is specific since it fails to react with any protein from lysates of Aspergillus flavus, Aspergillus niger, Aspergillus terreus, Penicillium marneffei, Candida albicans, Cryptococcus neoformans, Blastomyces dermatitidis, and Histoplasma capsulatum by Western blotting. In addition, this Afmp1p antigen-based ELISA is also specific for A. fumigatus since the cell culture supernatants of the other eight fungi gave negative results. Finally, a clinical evaluation of sera from invasive aspergillosis patients indicates that 8 of 15 (53%) patients are Afmp1p antigen test positive. Furthermore, an Afmp1p antibody test was performed with these serum specimens. The combined antibody and antigen tests for invasive aspergillosis carry a sensitivity of 86.7% (13 of 15). The specificities of the tests are high since none of the 138 control sera, including 100 from normal blood donors, 20 from patients with penicilliosis marneffei, 6 from patients with candidemia, 8 from patients with typhoid fever, and 4 from patients with melioidosis, was positive by either test. In conclusion, the combined Afmp1p antibody and antigen tests are highly sensitive and specific for A. fumigatus invasive aspergillosis.

Development and evaluation of rapid urinary antigen detection tests for diagnosis of penicilliosis marneffei

Penicilliosis, caused by the dimorphic fungus Penicillium marneffei, is an important opportunistic systemic fungal infection affecting immunocompromised individuals living in areas where penicilliosis is endemic. We have demonstrated previously that a urinary enzyme-linked immunosorbent assay (ELISA) with purified rabbit polyclonal antibody against killed whole-fission-form arthroconidia of P. marneffei was specific and highly sensitive for the diagnosis of penicilliosis. In this study, a dot blot ELISA and a latex agglutination (LA) test were developed with the same polyclonal antibody and compared with the ELISA for the detection of P. marneffei urinary antigen. Urine specimens from 37 patients with culture-proven penicilliosis and 300 controls (52 healthy subjects and 248 hospitalized patients without penicilliosis) were tested. Antigen was detected in urine from all 37 (100%) penicilliosis patients by the LA test, 35 (94.6%) penicilliosis patients by the dot blot ELISA, and 36 (97.3%) penicilliosis patients by the ELISA. False-positive results were found by the three assays for 2 (0.7%), 8 (2.7%), and 6 (2%) of 300 controls, respectively. The overall sensitivities of the diagnostic tests were as follows: dot blot ELISA, 94.6%; ELISA, 97.3%; and LA test, 100% (specificities, 97.3, 98, and 99.3%, respectively). The LA test is simple, robust, rapid, and convenient and should prove to be an important addition to the existing diagnostic tests for penicilliosis.

Current status of nonculture methods for diagnosis of invasive fungal infections

The incidence of invasive fungal infections has increased dramatically in recent decades, especially among immunocompromised patients. However, the diagnosis of these infections in a timely fashion is often very difficult. Conventional microbiologic and histopathologic approaches generally are neither sensitive nor specific, and they often do not detect invasive fungal infection until late in the course of disease. Since early diagnosis may guide appropriate treatment and prevent mortality, there has been considerable interest in developing nonculture approaches to diagnosing fungal infections. These approaches include detection of specific host immune responses to fungal antigens, detection of specific macromolecular antigens using immunologic reagents, amplification and detection of specific fungal nucleic acid sequences, and detection and quantitation of specific fungal metabolite products. This work reviews the current status and recent developments as well as problems in the design of nonculture diagnostic methods for invasive fungal infections.

Detection of antibodies specific to an antigenic cell wall galactomannoprotein for serodiagnosis of Aspergillus fumigatus aspergillosis

Aspergilloma and invasive aspergillosis are important opportunistic infections caused by Aspergillus species, among which Aspergillus fumigatus is the most common species associated with human disease. We developed an enzyme-linked immunosorbent assay (ELISA)-based antibody assay with Afmp1p, a purified recombinant antigenic cell wall galactomannoprotein of A. fumigatus. Evaluation of the test with guinea pig sera against A. fumigatus and other pathogenic fungi indicated that this assay was specific for A. fumigatus. Clinical evaluation revealed that the assay was 100% sensitive for patients with aspergilloma and 33.3% sensitive for patients with invasive aspergillosis. No false-positive results were found for serum samples from 80 healthy blood donors, 6 patients with typhoid fever, 4 patients with melioidosis, 20 patients with penicilliosis marneffei, 5 patients with candidiasis, and 4 patients with cryptococcosis, indicating a high specificity of the test. Thus, this ELISA-based test for the detection of anti-Afmp1p antibody can be of significant value as a diagnostic for aspergillosis.