Seroepidemiological study of Pneumocystis jirovecii infection in healthy infants in Chile using recombinant fragments of the P. jirovecii major surface glycoprotein

Novel Pneumocystis Antigens for Seroprevalence Studies

Pneumocystis jirovecii is the most common cause of fungal pneumonia in children under the age of 2 years. However, the inability to culture and propagate this organism has hampered the acquisition of a fungal genome as well as the development of recombinant antigens to conduct seroprevalence studies. In this study, we performed proteomics on Pneumocystis-infected mice and used the recent P. murina and P. jirovecii genomes to prioritize antigens for recombinant protein expression. We focused on a fungal glucanase due to its conservation among fungal species. We found evidence of maternal IgG to this antigen, followed by a nadir in pediatric samples between 1 and 3 months of age, followed by an increase in prevalence over time consistent with the known epidemiology of Pneumocystis exposure. Moreover, there was a strong concordance of anti-glucanase responses and IgG against another Pneumocystis antigen, PNEG_01454. Taken together, these antigens may be useful tools for Pneumocystis seroprevalence and seroconversion studies.

A therapeutic vaccine strategy to prevent Pneumocystis pneumonia in an immunocompromised host in a non-human primate model of HIV and Pneumocystis co-infection

Introduction

Pneumocystis is a ubiquitous fungal pathogen that causes pneumonia (PCP) and pulmonary sequelae in HIV-infected individuals and other immunocompromised populations. With the success of anti-retroviral therapy for HIV-infected individuals the frequency of PCP in that population has decreased, however, PCP remains a significant cause of morbidity and mortality in individuals with hematologic and solid malignancies, and in individuals treated with immunosuppressive therapies for autoimmune diseases, and following bone marrow and solid organ transplantation. Despite the clinical need, there is no approved vaccine to prevent PCP in vulnerable populations. The ultimate goal of the field is to develop an effective vaccine that can overcome immune deficits in at risk populations and induce long-lasting protective immunity to Pneumocystis. Toward this goal, our laboratory has established a model of PCP co-infection in simian immunodeficiency virus (SIV)-infected non-human primates (NHP) and identified a recombinant protein sub-unit vaccine, KEX1, that induces robust anti-Pneumocystis immunity in immune-competent macaques that is durable and prevents PCP following simian immunodeficiency virus (SIV)-induced immunosuppression. Type I, or invariant natural killer T (iNKT) cells have the potential to provide B cell help under conditions of reduced CD4+ T cell help.

Methods

In the present study, we used the SIV model of HIV infection to address whether therapeutic vaccination with the iNKT cell-activating adjuvant α-galactosylceramide (α-GC) and KEX1 (α-GC+KEX1) can effectively boost anti-Pneumocystis humoral immunity following virus-induced immunosuppression.

Results

Immunization of antigen-experienced NHPs with α-GC+KEX1 during the early chronic phase of SIV-infection significantly boosted anti-Pneumocystis humoral immunity by increasing memory B cells and antibody titers, and enhanced titer durability during SIV-induced immunosuppression. This therapeutic vaccination strategy boosted anti-Pneumocystis immune responses during SIV-infection and contributed to protection against Pneumocystis co-infection in KEX1-vaccinated macaques.

Conclusion

These studies present a novel strategy for stimulating durable anti-Pneumocystis humoral immunity in the context of complex, chronic SIV-induced immunosuppression and may be further applied to immunization of other immunosuppressed populations, and toward other common recall antigens.

Concurrent Infection with SARS-CoV-2 and Pneumocystis jirovecii in Immunocompromised and Immunocompetent Individuals

Coronavirus disease 2019 (COVID-19) may occur with concurrent infections caused by bacterial and fungal microorganisms. This systematic review evaluated studies reporting concomitant COVID-19 and Pneumocystis jirovecii pneumonia (PJP). We found 39 patients (74% male, median age: 56.8 (range: 11-83) years), including 66% immunosuppressed individuals (23% HIV-infected and 41% on long-term corticosteroid therapy). Patients were characteristically severely ill (mechanical ventilation: 70%), associated with 41% mortality. The median lymphocyte count was 527 cells/mm3 (range: 110-2200), and the median CD4+ T cell count was 206 cells/mm3 (range: 8-1021). We identified three patterns of concurrent COVID-19 and P. jirovecii infection. The first pattern (airway colonization with a low burden of P. jirovecii) does not seem to modify the COVID-19 course of illness. However, P. jirovecii superinfection, typically occurring weeks after COVID-19 diagnosis as a biphasic illness, and P. jirovecii coinfection characteristically results in progressive multilobar pneumonia, which is associated with poor outcomes. To support this categorization, we reported three patients with concurrent PJP and COVID-19 identified in our institution, presenting these clinical scenarios. The diagnosis of PJP requires a high index of suspicion, since clinical and radiological characteristics overlap with COVID-19. Observational studies are necessary to determine the PJP burden in patients with COVID-19 requiring hospitalization.

Sero-Epidemiology of Pneumocystis Infection among Infants, Children, and Adults in Chile

Previous serologic surveys show >80% of infants in Chile have anti-Pneumocystis antibodies by 2 years of age, but the seroepidemiology of Pneumocystis infection beyond infancy is unknown. We describe the sero-epidemiology in infants, children, and adults at different locations in Chile. Serum samples were prospectively obtained from 681 healthy adults (age ≥ 17 years) and 690 non-immunocompromised infants/children attending eight blood banks or outpatient clinics (2 in Santiago) in Chile. ELISA was used to measure serum IgM and IgG antibodies to Pneumocystis jirovecii major surface antigen (Msg) constructs MsgA and MsgC1. Serologic responses to Pneumocystis Msg showed a high frequency of reactivity, inferring infection. Among infants/children increasing age and the proportion with detectable IgM responses to MsgA, and IgG responses to MsgA, and MsgC1 were positively associated. Among adults there was almost universal seropositivity to one or more Pneumocystis Msg constructs. In infants and children rates of detectable IgM responses to MsgC1 and MsgA were greater than IgG responses. In Santiago, rates of seropositivity among infants/children were greater in clinics located in a more socio-economically deprived part of the city. In Chile, a serological response to Pneumocystis Msg constructs was common across ages regardless of geographical location and climatic conditions. Observed higher rates of IgM responses than IgG responses is consistent with concept of recent/ongoing exposure to Pneumocystis in children and adults. Higher rates of seropositivity in infants/children residing in more densely populated areas of Santiago infers crowding poses an increased risk of transmission.

Transmission and Colonization of Pneumocystis jirovecii

Pneumocystis spp. was discovered in 1909 and was classified as a fungus in 1988. The species that infects humans is called P. jirovecii and important characteristics of its genome have recently been discovered. Important advances have been made to understand P. jirovecii, including aspects of its biology, evolution, lifecycle, and pathogenesis; it is now considered that the main route of transmission is airborne and that the infectious form is the asci (cyst), but it is unclear whether there is transmission by direct contact or droplet spread. On the other hand, P. jirovecii has been detected in respiratory secretions of hosts without causing disease, which has been termed asymptomatic carrier status or colonization (frequency in immunocompetent patients: 0–65%, pregnancy: 15.5%, children: 0–100%, HIV-positive patients: 20–69%, cystic fibrosis: 1–22%, and COPD: 16–55%). This article briefly describes the history of its discovery and the nomenclature of Pneumocystis spp., recently uncovered characteristics of its genome, and what research has been done on the transmission and colonization of P. jirovecii. Based on the literature, the authors of this review propose a hypothetical natural history of P. jirovecii infection in humans.

Pneumocystis primary infection in non-immunosuppressed infants in Lima, Peru

OBJECTIVES

To provide original data on Pneumocystis primary infection in non-immunosuppressed infants from Peru.

METHODS

A cross sectional study was performed. Infants less than seven months old, without any underlying medical conditions attending the "well baby" outpatient clinic at one hospital in Lima, Peru were prospectively enrolled during a 15-month period from November 2016 to February 2018. All had a nasopharyngeal aspirate (NPA) for detection of P. jirovecii DNA using a PCR assay, regardless of respiratory symptoms. P. jirovecii DNA detection was considered to represent pulmonary colonization contemporaneous with Pneumocystis primary infection. Associations between infants' clinical and demographic characteristics and results of P. jirovecii DNA detection were analyzed.

RESULTS

P. jirovecii DNA was detected in 45 of 146 infants (30.8%) and detection was not associated with concurrent respiratory symptoms in 40 of 45 infants. Infants with P. jirovecii had a lower mean age when compared to infants not colonized (p <0.05). The highest frequency of P. jirovecii was observed in 2-3-month-old infants (p < 0.01) and in the cooler winter and spring seasons (p <0.01). Multivariable analysis showed that infants living in a home with ≤ 1 bedroom were more likely to be colonized; Odds Ratio =3.03 (95%CI 1.31-7.00; p = 0.01).

CONCLUSION

Pneumocystis primary infection in this single site in Lima, Peru, was most frequently observed in 2-3-month-old infants, in winter and spring seasons, and with higher detection rates being associated with household conditions favoring close inter-individual contacts and potential transmission of P. jirovecii.

Pneumocystis primary infection in infancy: Additional French data and review of the literature

Data on features of Pneumocystis primary infection in infancy are still fragmented. To study Pneumocystis primary infection, 192 infants who were monitored for acute pulmonary disease or fever over a 40-month period were retrospectively investigated. P. jirovecii detection on archival nasopharyngeal aspirates was performed using a qPCR assay. Factors associated with P. jirovecii were assessed using univariate and multivariate analyses. P. jirovecii genotypes in infants and a control group of adults contemporaneously diagnosed with Pneumocystis pneumonia were identified using unilocus, bilocus, and multilocus sequence typing (MLST). P. jirovecii was detected in 35 infants (18.2%). The univariate analysis pointed out four factors: viral infection (P = .035, OR [IC 95], 2.2 [1.1–4.7]), lower respiratory tract infection (P = .032, OR [IC 95], 2.5 [1.1–5.9]), absence of hospital discharge after birth (P = .003, OR (IC 95), 0.1 (0.02–0.5]), and the 63–189-day group (P < .001, OR [IC 95], 42.2 [5.4–332]). The multivariate analysis confirmed these two latter factors (P = .02, OR [IC 95], 0.1 [0.02–0.72]; P = .005, OR [IC 95], 11.5 [2.1–63.5]). Thus, P. jirovecii acquisition mostly takes place in the community. A comparison of these data with those of previously published studies showed that median and interquartile range of positive-infant ages were close to those observed in Chile, Denmark, and Peru, highlighting similar characteristics. Common unilocus or bilocus genotypes were identified in infants and adults, whereas no MLST genotypes were shared. Therefore, a common reservoir made up of infected infants and adults is still hypothetical. Finally, primary infection is a worldwide phenomenon occurring at the same time in childhood regardless of geographical location, rather than an incidental event.

Diagnosis of Pneumocystis jirovecii Pneumonia in Pediatric Patients in Serbia, Greece, and Romania. Current Status and Challenges for Collaboration

Pneumocystis jirovecii can cause fatal Pneumocystis pneumonia (PcP). Many children have been exposed to the fungus and are colonized in early age, while some individuals at high risk for fungal infections may develop PcP, a disease that is difficult to diagnose. Insufficient laboratory availability, lack of knowledge, and local epidemiology gaps make the problem more serious. Traditionally, the diagnosis is based on microscopic visualization of Pneumocystis in respiratory specimens. The molecular diagnosis is important but not widely used. The aim of this study was to collect initial indicative data from Serbia, Greece, and Romania concerning pediatric patients with suspected PcP in order to: find the key underlying diseases, determine current clinical and laboratory practices, and try to propose an integrative future molecular perspective based on regional collaboration. Data were collected by the search of literature and the use of an online questionnaire, filled by relevant scientists specialized in the field. All three countries presented similar clinical practices in terms of PcP prophylaxis and clinical suspicion. In Serbia and Greece the hematology/oncology diseases are the main risks, while in Romania HIV infection is an additional risk. Molecular diagnosis is available only in Greece. PcP seems to be under-diagnosed and regional collaboration in the field of laboratory diagnosis with an emphasis on molecular approaches may help to cover the gaps and improve the practices.

The Relationship between Pneumocystis Infection in Animal and Human Hosts, and Climatological and Environmental Air Pollution Factors: A Systematic Review

BACKGROUND

Over the past decade, there has been rising interest in the interaction of Pneumocystis with the environment. This interest has arisen in part from the demonstration that environmental factors have important effects on the viability and transmission of microbes, including Pneumocystis. Environmental factors include climatological factors such as temperature, humidity, and precipitation, and air pollution factors including carbon monoxide, nitrogen dioxide, sulfur dioxide, and particulate matter.

METHODS

We undertook a systematic review in order to identify environmental factors associated with Pneumocystis infection or PCP, and their effects on human and animal hosts.

RESULTS

The systematic review found evidence of associations between Pneumocystis infection in animal and human hosts, and climatological and air pollution factors. Data from human studies infers that rather than a seasonal association, presentation with PCP appears to be highest when the average temperature is between 10 and 20°C. There was evidence of an association with hospitalization with PCP and ambient air pollution factors, as well as evidence of an effect of air pollution on both systemic and bronchoscopic lavage fluid humoral responses to Pneumocystis. Interpretation of human studies was confounded by possible genetically-determined predisposition to, or protection from infection.

CONCLUSIONS

This systematic review provides evidence of associations between Pneumocystis infection in both animal and human hosts, and climatological and environmental air pollution factors. This information may lead to an improved understanding of the conditions involved in transmission of Pneumocystis in both animal and human hosts. Such knowledge is critical to efforts aimed at prevention.

Effects of clinical and environmental factors on bronchoalveolar antibody responses to Pneumocystis jirovecii: A prospective cohort study of HIV+ patients

BACKGROUND

Humoral immunity plays an important role against Pneumocystis jirovecii infection, yet clinical and environmental factors that impact bronchoalveolar antibody responses to P. jirovecii remain uncertain.

METHODS

From October 2008-December 2011 we enrolled consecutive HIV-infected adults admitted to San Francisco General Hospital (SFGH) who underwent bronchoscopy for suspected Pneumocystis pneumonia (PCP). We used local air quality monitoring data to assign ozone, nitrogen dioxide, and fine particulate matter exposures within 14 days prior to hospital admission. We quantified serum and bronchoalveolar lavage fluid (BALF) antibody responses to P. jirovecii major surface glycoprotein (Msg) recombinant constructs using ELISA. We then fit linear regression models to determine whether PCP and ambient air pollutants were associated with bronchoalveolar antibody responses to Msg.

RESULTS

Of 81 HIV-infected patients enrolled, 47 (58%) were diagnosed with current PCP and 9 (11%) had a prior history of PCP. The median CD4+ count was 51 cells/μl (IQR 15-129) and 44% were current smokers. Serum antibody responses to Msg were statistically significantly predictive of BALF antibody responses, with the exception of IgG responses to MsgC8 and MsgC9. Prior PCP was associated with increased BALF IgA responses to Msg and current PCP was associated with decreased IgA responses. For instance, among patients without current PCP, those with prior PCP had a median 73.2 U (IQR 19.2-169) IgA response to MsgC1 compared to a 5.00 U (3.52-12.6) response among those without prior PCP. Additionally, current PCP predicted a 22.5 U (95%CI -39.2, -5.82) lower IgA response to MsgC1. Ambient ozone within the two weeks prior to hospital admission was associated with decreased BALF IgA responses to Msg while nitrogen dioxide was associated with increased IgA responses.

CONCLUSIONS

PCP and ambient air pollutants were associated with BALF IgA responses to P. jirovecii in HIV-infected patients evaluated for suspected PCP.

Pneumocystis jirovecii--from a commensal to pathogen: clinical and diagnostic review

Pneumocystis pneumonia is an opportunistic disease caused by invasion of unicellular fungus Pneumocystis jirovecii. Initially, it was responsible for majority of morbidity and mortality cases among HIV-infected patients, which later have been reduced due to the introduction of anti-retroviral therapy, as well as anti-Pneumocystis prophylaxis among these patients. Pneumocystis pneumonia, however, is still a significant cause of mortality among HIV-negative patients being under immunosuppression caused by different factors, such as transplant recipients as well as oncologically treated ones. The issue of pneumocystosis among these people is particularly emphasized in the article, since rapid onset and fast progression of severe symptoms result in high mortality rate among these patients, who thereby represent the group of highest risk of developing Pneumocystis pneumonia. In contrast, fungal invasion in immunocompetent people usually leads to asymptomatic colonization, which frequent incidence among healthy infants has even suggested the possibility of its association with sudden unexpected infant death syndrome. In the face of emerging strains with different epidemiological profiles resulting from genetic diversity, including drug-resistant genotypes, the colonization phenomenon desires particular attention, discussed in this article. We also summarize specific and sensitive methods, required for detection of Pneumocystis invasion and for distinguish colonization from the disease.

Pneumocystis jirovecii colonization in Chronic Obstructive Pulmonary Disease (COPD)

Chronic obstructive pulmonary disease (COPD) is associated with a chronic inflammatory response in airways and lung parenchyma that results in significant morbidity and mortality worldwide. Cigarette smoking considered as an important risk factor plays a role in pathogenesis of disease. Pneumocystis jirovecii is an atypical opportunistic fungus that causes pneumonia in immunosuppressed host, although the low levels of its DNA in patients without signs and symptoms of pneumonia, which likely represents colonization. The increased prevalence of P. jirovecii colonization in COPD patients has led to an interest in understanding its role in the disease. P. jirovecii colonization in these patients could represent a problem for public health since colonized patients could act as a major reservoir and source of infection for susceptible subjects. Using sensitive molecular techniques, low levels of P. jirovecii DNA have been detected in the respiratory tract of certain individuals. It is necessary to elucidate the role of P. jirovecii colonization in the natural history of COPD patients in order to improve the clinical management of this disease. In the current review paper, we discuss P. jirovecii colonization in COPD patients.

Humoral immune responses to Pneumocystis jirovecii antigens in HIV-infected and uninfected young children with pneumocystis pneumonia

Background

Humoral immune responses in human immunodeficiency virus (HIV)-infected and uninfected children with Pneumocystis pneumonia (PcP) are poorly understood.

Methods

Consecutive children hospitalized with acute pneumonia, tachypnea, and hypoxia in South Africa were investigated for PcP, which was diagnosed by real-time polymerase chain reaction on lower respiratory tract specimens. Serum antibody responses to recombinant fragments of the carboxyl terminus of Pneumocystis jirovecii major surface glycoprotein (MsgC) were analyzed.

Results

149 children were enrolled of whom 96 (64%) were HIV-infected. PcP occurred in 69 (72%) of HIV-infected and 14 (26%) of HIV-uninfected children. HIV-infected children with PcP had significantly decreased IgG antibodies to MsgC compared to HIV-infected patients without PcP, but had similar IgM antibodies. In contrast, HIV-uninfected children with PcP showed no change in IgG antibodies to MsgC, but had significantly increased IgM antibodies compared to HIV-uninfected children without PCP. Age was an independent predictor of high IgG antibodies, whereas PcP was a predictor of low IgG antibodies and high IgM antibodies. IgG and IgM antibody levels to the most closely related MsgC fragments were predictors of survival from PcP.

Conclusions

Young HIV-infected children with PcP have significantly impaired humoral immune responses to MsgC, whereas HIV-uninfected children with PcP can develop active humoral immune responses. The children also exhibit a complex relationship between specific host factors and antibody levels to MsgC fragments that may be related to survival from PcP.

Selective ablation of lung epithelial IKK2 impairs pulmonary Th17 responses and delays the clearance of Pneumocystis

Pneumocystis is an atypical fungal pathogen that causes severe, often fatal pneumonia in immunocompromised patients. Healthy humans and animals also encounter this pathogen, but they generate a protective CD4(+) T cell-dependent immune response that clears the pathogen with little evidence of disease. Pneumocystis organisms attach tightly to respiratory epithelial cells, and in vitro studies have demonstrated that this interaction triggers NF-κB-dependent epithelial cell responses. However, the contribution of respiratory epithelial cells to the normal host response to Pneumocystis remains unknown. IκB kinase 2 (IKK2) is the upstream kinase that is critical for inducible NF-κB activation. To determine whether IKK2-dependent lung epithelial cell (LEC) responses contribute to the anti-Pneumocystis immune response in vivo, transgenic mice with LEC-specific deletion of IKK2 (IKK2(ΔLEC)) were generated. Compared to wild-type mice, IKK2(ΔLEC) mice exhibited a delayed onset of Th17 and B cell responses in the lung and delayed fungal clearance. Importantly, delayed Pneumocystis clearance in IKK2(ΔLEC) mice was associated with an exacerbated immune response, impaired pulmonary function, and altered lung histology. These data demonstrate that IKK2-dependent LEC responses are important regulators of pulmonary adaptive immune responses and are required for optimal host defense against Pneumocystis infection. LECs likely set the threshold for initiation of the pulmonary immune response and serve to prevent exacerbated lung inflammation by promoting the rapid control of respiratory fungal infection.

The ecology of pneumocystis: perspectives, personal recollections, and future research opportunities

I am honored to receive the second Lifetime Achievement Award by International Workshops on Opportunistic Protists and to give this lecture. My research involves Pneumocystis, an opportunistic pulmonary fungus that is a major cause of pneumonia ("PcP") in the immunocompromised host. I decided to focus on Pneumocystis ecology here because it has not attracted much interest. Pneumocystis infection is acquired by inhalation, and the cyst stage appears to be the infective form. Several fungal lung infections, such as coccidiomycosis, are not communicable, but occur by inhaling < 5 μm spores from environmental sources (buildings, parks), and can be affected by environmental factors. PcP risk factors include environmental constituents (temperature, humidity, SO2 , CO) and outdoor activities (camping). Clusters of PcP have occurred, but no environmental source has been found. Pneumocystis is communicable and outbreaks of PcP, especially in renal transplant patients, are an ongoing problem. Recent evidence suggests that most viable Pneumocystis organisms detected in the air are confined to a patient's room. Further efforts are needed to define the risk of Pneumocystis transmission in health care facilities; to develop more robust preventive measures; and to characterize the effects of climatological and air pollutant factors on Pneumocystis transmission in animal models similar to those used for respiratory viruses.

Serologic responses to recombinant Pneumocystis jirovecii major surface glycoprotein among Ugandan patients with respiratory symptoms

BACKGROUND

Little is known about the serologic responses to Pneumocystis jirovecii major surface glycoprotein (Msg) antigen in African cohorts, or the IgM responses to Msg in HIV-positive and HIV-negative persons with respiratory symptoms.

METHODS

We conducted a prospective study of 550 patients, both HIV-positive (n = 467) and HIV-negative (n = 83), hospitalized with cough ≥2 weeks in Kampala, Uganda, to evaluate the association between HIV status, CD4 cell count, and other clinical predictors and antibody responses to P. jirovecii. We utilized ELISA to measure the IgM and IgG serologic responses to three overlapping recombinant fragments that span the P. jirovecii major surface glycoprotein: MsgA (amino terminus), MsgB (middle portion) and MsgC1 (carboxyl terminus), and to three variations of MsgC1 (MsgC3, MsgC8 and MsgC9).

RESULTS

HIV-positive patients demonstrated significantly lower IgM antibody responses to MsgC1, MsgC3, MsgC8 and MsgC9 compared to HIV-negative patients. We found the same pattern of low IgM antibody responses to MsgC1, MsgC3, MsgC8 and MsgC9 among HIV-positive patients with a CD4 cell count <200 cells/µl compared to those with a CD4 cell count ≥200 cells/µl. HIV-positive patients on PCP prophylaxis had significantly lower IgM responses to MsgC3 and MsgC9, and lower IgG responses to MsgA, MsgC1, MsgC3, and MsgC8. In contrast, cigarette smoking was associated with increased IgM antibody responses to MsgC1 and MsgC3 but was not associated with IgG responses. We evaluated IgM and IgG as predictors of mortality. Lower IgM responses to MsgC3 and MsgC8 were both associated with increased in-hospital mortality.

CONCLUSIONS

HIV infection and degree of immunosuppression are associated with reduced IgM responses to Msg. In addition, low IgM responses to MsgC3 and MsgC8 are associated with increased mortality.

Colonization by Pneumocystis jirovecii and its role in disease

Although the incidence of Pneumocystis pneumonia (PCP) has decreased since the introduction of combination antiretroviral therapy, it remains an important cause of disease in both HIV-infected and non-HIV-infected immunosuppressed populations. The epidemiology of PCP has shifted over the course of the HIV epidemic both from changes in HIV and PCP treatment and prevention and from changes in critical care medicine. Although less common in non-HIV-infected immunosuppressed patients, PCP is now more frequently seen due to the increasing numbers of organ transplants and development of novel immunotherapies. New diagnostic and treatment modalities are under investigation. The immune response is critical in preventing this disease but also results in lung damage, and future work may offer potential areas for vaccine development or immunomodulatory therapy. Colonization with Pneumocystis is an area of increasing clinical and research interest and may be important in development of lung diseases such as chronic obstructive pulmonary disease. In this review, we discuss current clinical and research topics in the study of Pneumocystis and highlight areas for future research.

Serum antibody levels to the Pneumocystis jirovecii major surface glycoprotein in the diagnosis of P. jirovecii pneumonia in HIV+ patients

Background

Pneumocystis jirovecii remains an important cause of fatal pneumonia (Pneumocystis pneumonia or PcP) in HIV+ patients and other immunocompromised hosts. Despite many previous attempts, a clinically useful serologic test for P. jirovecii infection has never been developed.

Methods/Principal Findings

We analyzed serum antibody responses to the P. jirovecii major surface glycoprotein recombinant fragment C1 (MsgC1) in 110 HIV+ patients with active PcP (cases) and 63 HIV+ patients with pneumonia due to other causes (controls) by an enzyme-linked immunosorbent assay (ELISA). The cases had significantly higher IgG and IgM antibody levels to MsgC1 than the controls at hospital admission (week 0) and intervals up to at least 1 month thereafter. The sensitivity, specificity and positive predictive value (PPV) of IgG antibody levels increased from 57.2%, 61.7% and 71.5% at week 0 to 63.4%, 100%, and 100%, respectively, at weeks 3–4. The sensitivity, specificity and PPV of IgM antibody levels rose from 59.7%, 61.3%, and 79.3% at week 0 to 74.6%, 73.7%, and 89.8%, respectively, at weeks 3–4. Multivariate analysis revealed that a diagnosis of PcP was the only independent predictor of high IgG and IgM antibody levels to MsgC1. A high LDH level, a nonspecific marker of lung damage, was an independent predictor of low IgG antibody levels to MsgC1.

Conclusions/Significance

The results suggest that the ELISA shows promise as an aid to the diagnosis of PCP in situations where diagnostic procedures cannot be performed. Further studies in other patient populations are needed to better define the usefulness of this serologic test.