SARS-CoV-2 nucleocapsid antigen in plasma of children hospitalized for COVID-19 or with incidental detection of SARS-CoV-2 infection

In hospitalized children, SARS-CoV-2 infection can present as either a primary reason for admission (patients admitted for COVID-19) or an incidental finding during follow-up (patients admitted with COVID-19). We conducted a nested case-control study within a cohort of pediatric patients with confirmed SARS-CoV-2 infection, to investigate the concentration of plasma nucleocapsid antigen (N-Ag) in children admitted for COVID-19 or with COVID-19. While reverse transcriptase polymerase chain reaction Ct values in nasopharyngeal swab were similar between the two groups, children admitted for COVID-19 had a higher rate of detectable N-Ag (12/18 (60.7%) versus 6/18 (33.3%), p = 0.0455) and a higher concentration of N-Ag (medians: 19.51 g/mL vs. 1.08 pg/mL, p = 0.0105). In children hospitalized for COVID-19, the youngest had higher concentration of N-Ag (r = -0.74, p = 0.0004). We also observed a lower prevalence of detectable spike antibodies in children hospitalized for COVID-19 compared to those hospitalized for other medical reasons (3/15 [20%] vs. 13/16 [81.25%], respectively, p = < 0.0011), but similar rates of IgG nucleocapsid antibodies (5/14 [35.7%] vs. 6/17 [35.3%], respectively, p = 0.99). Our findings indicate that N-Ag is associated with COVID-19-related hospitalizations in pediatric patients, and less frequently detected in children tested positive for SARS-CoV-2 but hospitalized for another medical reason. Further studies are needed to confirm the value of N-Ag in identifying COVID-19 disease infections in which SARS-CoV-2 is the main pathogen responsible for symptoms.

High sera levels of SARS-CoV-2 N antigen are associated with death in hospitalized COVID-19 patients

The presence of free severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid-antigen in sera (N-antigenemia) has been shown in COVID-19 patients. However, the link between the quantitative levels of N-antigenemia and COVID-19 disease severity is not entirely understood. To assess the dynamics and clinical association of N-antigen sera levels with disease severity in COVID-19 patients, we analyzed data from patients included in the French COVID cohort, with at least one sera sample between January and September 2020. We assessed N-antigenemia levels and anti-N IgG titers, and patient outcomes was classified in two groups, survival or death. In samples collected within 8 days since symptom onset, we observed that deceased patients had a higher positivity rate (93% vs. 81%; p < 0.001) and higher median levels of predicted N-antigenemia (2500 vs. 1200 pg/mL; p < 0.001) than surviving patients. Predicted time to N-antigen clearance in sera was prolonged in deceased patients compared to survivors (23.3 vs 19.3 days; p < 0.0001). In a subset of patients with both sera and nasopharyngeal (NP) swabs, predicted time to N-antigen clearance in sera was prolonged in deceased patients (p < 0.001), whereas NP viral load clearance did not differ between the groups (p = 0.07). Our results demonstrate a strong relationship between N-antigenemia levels and COVID-19 severity on a prospective cohort.

Frequency of Dirofilaria immitis infection in blood donor dogs of the Rio de Janeiro state

Dirofilariasis, a parasitic disease caused by the nematode Dirofilaria immitis, commonly known as heartworm, primarily inhabits the pulmonary artery and right heart of dogs and other animals. The disease is transmitted through diptera, predominantly from the Culex, Aedes, and Anopheles genera. Dirofilariasis is cosmopolitan in nature, endemic in coastal regions and tropical climates. Factors such as temperature, humidity, vector density, and the presence of definitive hosts significantly contribute to the spread of this parasitic disease. In the state of Rio de Janeiro, a prevalence of 58.6% of D. immitis infected animals has been recorded in municipalities like Niterói. Given that blood transfusions are routine clinical procedures and blood bags are not always accurately evaluated, an investigation into D. immitis infection in blood donor dogs from the metropolitan region of Rio de Janeiro was conducted. A total of 1044 blood donor dog files from a blood bank in Niterói, RJ, collected from January 2019 to December 2022, were analyzed. These samples, originating from kennels in various municipalities in the Metropolitan Region, were tested for the presence of microfilariae through direct examination using tubes and microhematocrit evaluated in optical microscopy. Additionally, the search for antigens was conducted using the enzyme-linked immunosorbent assay technique. Out of the 1044 records evaluated, 17.8% (186/1044) were positive for heartworm infection, with 2% (21/1044) samples positive for microfilariae and 14.8% (154/1044) positive for D. immitis antigens. The high prevalence rate indicates that canine D. immitis infection remains prevalent in the state of Rio de Janeiro, necessitating effective guidelines for prescribing preventive medications by veterinarians and an increase in epidemiological surveillance in the region.

Prevalence and Factors Associated With Cryptoccocal Antigenemia Among Patients With Advanced Human Immunodeficiency Virus in Eastern Uganda: A Facility-Based Cross-sectional Study

Background

Cryptoccocal infection remains an important cause of morbidity and mortality among people with advanced human immunodeficiency virus disease (AHD). In resource-limited settings, there is a paucity of data on cryptoccocal infections. We described the prevalence and factors associated with cryptoccocal antigenemia among people with AHD in Mbale Regional Referral Hospital in Eastern Uganda.

Methods

In this cross-sectional study, data on sociodemographic, clinical, and laboratory characteristics of adults with AHD were collected, and factors associated with cryptoccocal antigenemia were determined using multivariate logistic regression models.

Results

We enrolled 228 participants with a median CD4 cell count of 194/µL (interquartile range, 129-370/µL). The prevalence of cryptoccocal antigen was 10 in 228 (4.4% [95% confidence interval, 2.4%-80%]). CD4 cell counts <100/µL (adjusted odds ratio, 3.70) and poultry keeping were risk factors. The main predictors were headaches (adjusted odds ratio, 1), neck pains (8.817), confusion (6.323), and neck stiffness (676.217). No notable significant associations were found in the multivariate analysis.

Conclusions

The prevalence of cryptoccocal antigen was 4.4%, and antiretroviral therapy was protective.

Investigation of Blood Plasma Viral Nucleocapsid Antigen as a Marker of Active Severe Acute Respiratory Syndrome Coronavirus 2 Omicron Variant Infection

Background

Nasopharyngeal qualitative reverse-transcription polymerase chain reaction (RT-PCR) is the gold standard for diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, but it is not practical or sufficient in every clinical scenario due to its inability to distinguish active from resolved infection. Alternative or adjunct testing may be needed to guide isolation precautions and treatment in patients admitted to the hospital.

Methods

We performed a single-center, retrospective analysis of residual clinical specimens and medical record data to examine blood plasma nucleocapsid antigen as a candidate biomarker of active SARS-CoV-2. Adult patients admitted to the hospital or presenting to the emergency department with SARS-CoV-2 ribonucleic acid (RNA) detected by RT-PCR from a nasopharyngeal swab specimen were included. Both nasopharyngeal swab and a paired whole blood sample were required to be available for analysis.

Results

Fifty-four patients were included. Eight patients had positive nasopharyngeal swab virus cultures, 7 of whom (87.5%) had concurrent antigenemia. Nineteen (79.2%) of 24 patients with detectable subgenomic RNA and 20 (80.0%) of 25 patients with N2 RT-PCR cycle threshold ≤ 33 had antigenemia.

Conclusions

Most individuals with active SARS-CoV-2 infection are likely to have concurrent antigenemia, but there may be some individuals with active infection in whom antigenemia is not detectable. The potential for high sensitivity and convenience of a blood test prompts interest in further investigation as a screening tool to reduce reliance on nasopharyngeal swab sampling and as an adjunct diagnostic test to aid in clinical decision making during the period after acute coronavirus disease 2019.

SARS-CoV-2 Antigenemia is Associated With Pneumonia in Children But Lacks Sensitivity to Diagnose Acute Infection

BACKGROUND

Nucleocapsid antigenemia in adults has demonstrated high sensitivity and specificity for acute infection, and antigen burden is associated with disease severity. Data regarding SARS-CoV-2 antigenemia in children are limited.

METHODS

We retrospectively analyzed blood plasma specimens from hospitalized children with COVID-19 or MIS-C. Nucleocapsid and spike were measured using ultrasensitive immunoassays.

RESULTS

We detected nucleocapsid antigenemia in 62% (50/81) and spike antigenemia in 27% (21/79) of children with acute COVID-19 but 0% (0/26) and 15% (4/26) with MIS-C from March 2020-March 2021. Higher nucleocapsid levels were associated with radiographic infiltrates and respiratory symptoms in children with COVID-19.

CONCLUSIONS

Antigenemia lacks the sensitivity to diagnose acute infection in children but is associated with signs and symptoms of lower respiratory tract involvement. Further study into the mechanism of antigenemia, its association with specific organ involvement, and the role of antigenemia in the pathogenesis of COVID-19 is warranted.

Measurement of Severe Acute Respiratory Syndrome Coronavirus 2 Antigens in Plasma of Pediatric Patients With Acute Coronavirus Disease 2019 or Multisystem Inflammatory Syndrome in Children Using an Ultrasensitive and Quantitative Immunoassay

BACKGROUND

Detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens in blood has high sensitivity in adults with acute coronavirus disease 2019 (COVID-19), but sensitivity in pediatric patients is unclear. Recent data suggest that persistent SARS-CoV-2 spike antigenemia may contribute to multisystem inflammatory syndrome in children (MIS-C). We quantified SARS-CoV-2 nucleocapsid (N) and spike (S) antigens in blood of pediatric patients with either acute COVID-19 or MIS-C using ultrasensitive immunoassays (Meso Scale Discovery).

METHODS

Plasma was collected from inpatients (<21 years) enrolled across 15 hospitals in 15 US states. Acute COVID-19 patients (n = 36) had a range of disease severity and positive nasopharyngeal SARS-CoV-2 RT-PCR within 24 hours of blood collection. Patients with MIS-C (n = 53) met CDC criteria and tested positive for SARS-CoV-2 (RT-PCR or serology). Controls were patients pre-COVID-19 (n = 67) or within 24 hours of negative RT-PCR (n = 43).

RESULTS

Specificities of N and S assays were 95-97% and 100%, respectively. In acute COVID-19 patients, N/S plasma assays had 89%/64% sensitivity; sensitivities in patients with concurrent nasopharyngeal swab cycle threshold (Ct) ≤35 were 93%/63%. Antigen concentrations ranged from 1.28-3844 pg/mL (N) and 1.65-1071 pg/mL (S) and correlated with disease severity. In MIS-C, antigens were detected in 3/53 (5.7%) samples (3 N-positive: 1.7, 1.9, 121.1 pg/mL; 1 S-positive: 2.3 pg/mL); the patient with highest N had positive nasopharyngeal RT-PCR (Ct 22.3) concurrent with blood draw.

CONCLUSIONS

Ultrasensitive blood SARS-CoV-2 antigen measurement has high diagnostic yield in children with acute COVID-19. Antigens were undetectable in most MIS-C patients, suggesting that persistent antigenemia is not a common contributor to MIS-C pathogenesis.

Nucleocapsid Antigenemia Is a Marker of Acute SARS-CoV-2 Infection

Detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is essential for diagnosis, treatment, and infection control. Polymerase chain reaction (PCR) fails to distinguish acute from resolved infections, as RNA is frequently detected after infectiousness. We hypothesized that nucleocapsid in blood marks acute infection with the potential to enhance isolation and treatment strategies. In a retrospective serosurvey of inpatient and outpatient encounters, we categorized samples along an infection timeline using timing of SARS-CoV-2 testing and symptomatology. Among 1860 specimens from 1607 patients, the highest levels and frequency of antigenemia were observed in samples from acute SARS-CoV-2 infection. Antigenemia was higher in seronegative individuals and in those with severe disease. In our analysis, antigenemia exhibited 85.8% sensitivity and 98.6% specificity as a biomarker for acute coronavirus disease 2019 (COVID-19). Thus, antigenemia sensitively and specifically marks acute SARS-CoV-2 infection. Further study is warranted to determine whether antigenemia may aid individualized assessment of active COVID-19.

Measurement of SARS-CoV-2 antigens in plasma of pediatric patients with acute COVID-19 or MIS-C using an ultrasensitive and quantitative immunoassay

BACKGROUND

Detection of SARS-CoV-2 antigens in blood has high sensitivity in adults with acute COVID-19, but sensitivity in pediatric patients is unclear. Recent data suggest that persistent SARS-CoV-2 spike antigenemia may contribute to multisystem inflammatory syndrome in children (MIS-C). We quantified SARS-CoV-2 nucleocapsid (N) and spike (S) antigens in blood of pediatric patients with either acute COVID-19 or MIS-C using ultrasensitive immunoassays (Meso Scale Discovery).

METHODS

Plasma was collected from inpatients (<21 years) enrolled across 15 hospitals in 15 US states. Acute COVID-19 patients (n=36) had a range of disease severity and positive nasopharyngeal SARS-CoV-2 RT-PCR within 24 hours of blood collection. Patients with MIS-C (n=53) met CDC criteria and tested positive for SARS-CoV-2 (RT-PCR or serology). Controls were patients pre-COVID-19 (n=67) or within 24h of negative RT-PCR (n=43).

RESULTS

Specificities of N and S assays were 95-97% and 100%, respectively. In acute COVID-19 patients, N/S plasma assays had 89%/64% sensitivity, respectively; sensitivity in patients with concurrent nasopharyngeal swab cycle threshold (Ct) ≤ 35 were 93%/63%. Antigen concentrations ranged from 1.28-3,844 pg/mL (N) and 1.65-1,071 pg/mL (S) and correlated with disease severity. In MIS-C, antigens were detected in 3/53 (5.7%) samples (3 N-positive: 1.7, 1.9, 121.1 pg/mL; 1 S-positive: 2.3 pg/mL); the patient with highest N had positive nasopharyngeal RT-PCR (Ct 22.3) concurrent with blood draw.

CONCLUSIONS

Ultrasensitive blood SARS-CoV-2 antigen measurement has high diagnostic yield in children with acute COVID-19. Antigens were undetectable in most MIS-C patients, suggesting that persistent antigenemia is not a common contributor to MIS-C pathogenesis.

KEY POINTS

In a U.S. pediatric cohort tested with ultrasensitive immunoassays, SARS-CoV-2 nucleocapsid antigens were detectable in most patients with acute COVID-19, and spike antigens were commonly detectable. Both antigens were undetectable in almost all MIS-C patients.

Survival following screening and preemptive antifungal therapy for subclinical cryptococcal disease in advanced HIV infection

OBJECTIVES

Our study's primary objective was to compare 1-year survival rates between serum cryptococcal antigen (sCrAg)-positive and sCrAg-negative HIV-positive individuals with CD4+ cell counts less than 100 cells/μl without symptoms of meningitis in Zimbabwe.

DESIGN

This was a prospective cohort study.

METHODS

Participants were enrolled as either sCrAg-positive or sCrAg-negative and followed up for 52 weeks or less, with death as the outcome. Lumbar punctures were recommended to all sCrAg-positives and inpatient management with intravenous amphotericin B and high-dose fluconazole was recommended to those with disseminated Cryptococcus. Antiretroviral therapy was initiated immediately in sCrAg-negatives and after at least 4 weeks following initiation of antifungals in sCrAg-positives. Multivariable logistic regression models were used to determine risk factors for mortality.

RESULTS

We enrolled 1320 participants and 130 (9.8%) were sCrAg positive, with a median sCrAg titre of 1 : 20. Sixty-six (50.8%) sCrAg-positives had lumbar punctures and 16.7% (11/66) had central nervous system (CNS) dissemination. Cryptococcal blood cultures were performed in 129 sCrAg-positives, with 10 (7.8%) being positive. One-year (48-52 weeks) survival rates were 83.9 and 76.1% in sCrAg-negatives and sCrAg-positives, respectively, P = 0.011. Factors associated with increased mortality were a positive sCrAg, CD4+ cell count less than 50 cells/μl and having presumptive tuberculosis (TB) symptoms.

CONCLUSION

Our study reports a high prevalence of subclinical cryptococcal antigenemia and reiterates the importance of TB and a positive sCrAg as risk factors for mortality in advanced HIV disease (AHD). Therefore, TB and sCrAg screening remains a crucial component of AHD package, hence it should always be part of the comprehensive clinical evaluation in AHD patients.

Antibody and Antigen Prevalence as Indicators of Ongoing Transmission or Elimination of Visceral Leishmaniasis: A Modeling Study

Background

Control of visceral leishmaniasis (VL) on the Indian subcontinent has been highly successful. Control efforts such as indoor residual spraying and active case detection will be scaled down or even halted over the coming years. We explored how after scale-down, potential recurrence of VL cases may be predicted based on population-based surveys of antibody or antigenemia prevalence.

Methods

Using a stochastic age-structured transmission model of VL, we predicted trends in case incidence and biomarker prevalence over time after scaling down control efforts when the target of 3 successive years without VL cases has been achieved. Next, we correlated biomarker prevalence with the occurrence of new VL cases within 10 years of scale-down.

Results

Occurrence of at least 1 new VL case in a population of 10 000 was highly correlated with the seroprevalence and antigenemia prevalence at the moment of scale-down, or 1 or 2 years afterward. Receiver operating characteristic curves indicated that biomarker prevalence in adults provided the most predictive information, and seroprevalence was a more informative predictor of new VL cases than antigenemia prevalence. Thresholds for biomarker prevalence to predict occurrence of new VL cases with high certainty were robust to variation in precontrol endemicity.

Conclusions

The risk of recrudescence of VL after scaling down control efforts can be monitored and mitigated by means of population-based surveys. Our findings highlight that rapid point-of-care diagnostic tools to assess (preferably) seroprevalence or (otherwise) antigenemia in the general population could be a key ingredient of sustainable VL control.

SARS-CoV-2 Antigenemia as a Confounding Factor in Immunodiagnostic Assays: A Case Study

Humoral immunity has emerged as a vital immune component against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Nevertheless, a subset of recovered Coronavirus Disease-2019 (COVID-19) paucisymptomatic/asymptomatic individuals do not generate an antibody response, constituting a paradox. We assumed that immunodiagnostic assays may operate under a competitive format within the context of antigenemia, potentially explaining this phenomenon. We present a case where persistent antigenemia/viremia was documented for at least 73 days post-symptom onset using ‘in-house’ methodology, and as it progressively declined, seroconversion took place late, around day 55, supporting our hypothesis. Thus, prolonged SARS-CoV-2 antigenemia/viremia could mask humoral responses, rendering, in certain cases, the phenomenon of ‘non-responders’ a misnomer.

Prevalence and Correlates of Lymphatic Filariasis Infection and Its Morbidity Following Mass Ivermectin and Albendazole Administration in Mkinga District, North-Eastern Tanzania

Lymphatic filariasis (LF) is a neglected tropical disease targeted for elimination as public health problem through morbidity management and preventive annual mass drug administration (MDA). This cross-sectional community-based surveillance assessed the prevalence and correlates of LF infection in Mkinga district, Tanga-region, Tanzania. A total of 4115 individuals (49.7% males, 35.2% children) were screened for circulating filarial antigens (CFA), microfilaremia (mf) and disease manifestations in 15 villages between November 2018 and January 2019. MDA uptake in the previous year was assessed. Overall prevalence of CFA-positivity was 5.8% (239/4115; 95% CI: 5.1–6.6), with significant heterogeneity between villages (range 1.2% to 13.5%). CFA-positivity was higher in males (8.8%) than females (3.3%), and correlated with increasing age (p < 0.001). Prevalence of mf among CFA-positives was 5.2%. Only 60% of eligible inhabitants in the study area took MDA in the previous year, and CFA-positivity was 2-fold higher in those who missed MDA (p < 0.0001). Prevalence of scrotal enlargement, hydrocele, arms or legs swelling, lymphoedema and lymphadenopathy was 6.4%, 3.7%, 1.35%, 1.2% and 0.32%, respectively. Compared to baseline data, 16 years of MDA intervention significantly reduced LF transmission and morbidity, although the intended elimination target of <1% mf and <2% antigenemia to level where recrudescence is unlikely to occur by the year 2020 may not be attained. The finding of hotspots with ongoing transmission calls for intensified control measures.

Follow-Up of Viral Parameters in FeLV- or FIV-Naturally Infected Cats Treated Orally with Low Doses of Human Interferon Alpha

Specific treatments for the long-life infections by feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are either toxic, expensive or not too effective. Interferon α (IFN-α) is an immunomodulatory molecule which has been shown in vitro to decrease the release of infective particles. The aim of this study was to follow the progress of the clinical score and viral parameters of FeLV- and FIV-naturally infected privately owned cats treated with recombinant human IFN-α (rHuIFN-α, Roferon-A). Twenty-seven FeLV-infected cats (FeLV+) and 31 FIV-infected cats (FIV+) were enrolled in the study. Owners were instructed to orally administer 1 mL/day of 60 IU rHuIFN-α/mL in alternating weeks for four months. Blood samples were taken at the beginning of the study (M0), mid-treatment (M2), end of treatment (M4), and 6-10 months later (M10). Clinical status at these time points improved notably with rHuIFN-α treatment, regardless of the initial severity of the disease, an effect which lasted throughout the study in most animals (15 of the 16 FeLV+ symptomatic cats; 20 of the 22 FIV+ symptomatic cats) improved markedly their clinical situation. In FeLV+ cats plasma antigenemia (p27CA), reverse transcriptase (RT) activity, and proviral load decreased at M2 and M4 but increased again at M10 ("rebound effect"). The level of antigenemia or RT activity was below the detection limits in FIV+ cats, and the effect on proviral load was less marked than in FeLV+ cats. Taken together, these results indicate that rHuIFN-α is a good candidate for treating FeLV+ cats, but the "rebound effect" seen when treatment was discontinued suggests that additional studies should be conducted to clarify its effect on progression of the infection in cats.

Galactomannan antigenemia as a biomarker for therapeutic response of invasive aspergillosis: implications for clinical trial design and patient care

INTRODUCTION

Clinical trials for invasive pulmonary aspergillosis, a potentially lethal mold infection, are complex investigations that require protracted time and extensive resources, delaying the development of new antifungal agents for this important disease. Areas covered: In this paper, the authors examine a novel approach to study invasive pulmonary aspergillosis in humans, with a focus on the potentials and pitfalls of surrogate end points such as galactomannan antigenemia to evaluate therapeutic response to novel compounds. Expert commentary: The authors believe the use of serum galactomannan as a primary end point in clinical trials may allow for development studies that could be accomplished with fewer resources. It is widely appreciated that serum galactomannan values strongly correlate with outcome of invasive aspergillosis in patients with hematologic cancer and may be applicable to other at-risk patient populations.

Translational Development and Application of (1→3)-β-d-Glucan for Diagnosis and Therapeutic Monitoring of Invasive Mycoses

Early diagnosis and prompt initiation of appropriate antimicrobial therapy are crucial steps in the management of patients with invasive fungal infections. However, the diagnosis of invasive mycoses remains a major challenge in clinical practice, because presenting symptoms may be subtle and non-invasive diagnostic assays often lack sensitivity and specificity. Diagnosis is often expressed on a scale of probability (proven, probable and possible) based on a constellation of imaging findings, microbiological tools and histopathology, as there is no stand-alone assay for diagnosis. Recent data suggest that the carbohydrate biomarker (1→3)-β-d-glucan may be useful in both the diagnosis and therapeutic monitoring of invasive fungal infections due to some yeasts, molds, and dimorphic fungi. In this paper, we review recent advances in the use of (1→3)-β-d-glucan to monitor clinical response to antifungal therapy and explore how this assay may be used in the future.

Three infants with rotavirus gastroenteritis complicated by severe gastrointestinal bleeding

Rotavirus gastroenteritis causes substantial morbidity and mortality worldwide in children. We report three infants with rotavirus gastroenteritis complicated by various severity of gastrointestinal bleeding. Two patients (cases 1 and 2) recovered completely without any specific treatments. One patient (case 3) died despite extensive treatments including a red blood cell transfusion and endoscopic hemostatic therapy. Rotavirus genotypes G1P[8] and G9P[8] were detected in cases 2 and 3, respectively. Rotavirus antigenemia levels were not high at the onset of melena, suggesting that systemic rotaviral infection does not play an important role in causing melena.

The usefulness of a diagnostic method combining high-resolution CT findings and serum markers for cytomegalovirus pneumonia and pneumocystis pneumonia in non-AIDS patients

BACKGROUND

The combination of high-resolution computed tomography (HRCT) findings and serum markers would be of great value in diagnosing cytomegalovirus pneumonia (CMVP) and pneumocystis pneumonia (PCP) considering low invasiveness.

PURPOSE

To compare the HRCT findings of CMVP and PCP and to evaluate the differences in HRCT findings between patients diagnosed based on pathologic evidence and serum markers.

MATERIAL AND METHODS

Two radiologists retrospectively evaluated the HRCT findings of 21 patients with CMVP and 70 patients with PCP. Eight patients with CMVP and 32 patients with PCP were diagnosed based on pathologic evidence ("Path" group), while 13 patients with CMVP and 38 patients with PCP were diagnosed based on serum markers (CMV antigenemia, β-D-glucan) ("Serum-Marker" group). A total of 19 CT morphological criteria were evaluated, and the significance of the differences between the two diseases and between the "Path" and "Serum-Marker" groups with respect to each disease was calculated.

RESULTS

The presence of small nodules, the tree-in-bud pattern, and the halo sign was found more frequently in the CMVP group. Extensive ground-glass attenuation (GGA), a mosaic pattern, and a diffuse distribution were observed more frequently in the PCP group. There were significant differences between the "Path" and "Serum-Marker" groups in average extent of consolidation and distribution of consolidation in PCP, and the distribution of GGA in CMVP, respectively.

CONCLUSION

The combined use of HRCT findings and serum markers is useful for the diagnosis of CMVP and PCP in non-AIDS patients. The typical HRCT findings for the differential diagnosis included extensive GGA with mosaic pattern in PCP and nodules, nodules with or without the tree-in-bud pattern, and the halo sign in CMVP.

Rapid Detection of Toxoplasma gondii Antigen in Experimentally Infected Mice by Dot- ELISA

BACKGROUND

Toxoplasmosis is a worldwide endemic disease. In congenitally infected infants and AIDS patients, toxoplasmosis causes high rates of morbidity and mortality. In these cases antibody detection is difficult; so detection of parasite or its components could be useful tool for early detection and following treatment of the infection.

METHODS

Sixty-three BALB/c mice were injected intra-peritoneal with 5×10(3) tachyzoites of Toxoplasma gondii RH strain, nine mice were sacrificed daily for 7 days. Fourteen mice were injected with phosphate buffer saline as control group. Dot-ELISA was performed for detection of T.gondii antigen in mice sera and capture - ELISA was done as golden standard assay too.

RESULTS

Toxoplasma gondii antigen was detected from day 2 in mice sera; 22% of mice sera on day 2, 33% on day 3,77% on day 4 and 100% on day 5 till their death on day 7 had shown antigenemia by dot - ELISA, no positive result was detected in control mice by dot- ELISA.

CONCLUSION

Dot-ELISA is a sensitive method for diagnosis of T. gondii infection in the animal model; also, this technique is more rapid and easy to perform method in comparison with capture-ELISA.

Active human cytomegalovirus infection and glycoprotein b genotypes in brazilian pediatric renal or hematopoietic stem cell transplantation patients

A prospective analysis of active Human Cytomegalovirus infection (HCMV) was conducted on 33 pediatric renal or hematopoietic stem cell post-transplant patients. The HCMV-DNA positive samples were evaluated for the prevalence of different gB subtypes and their subsequent correlation with clinical signs. The surveillance of HCMV active infection was based on the monitoring of antigenemia (AGM) and on a nested polymerase chain reaction (N-PCR) for the detection of HCMV in the patients studied. Using restriction analysis of the gB gene sequence by PCR-RFLP (Restriction Fragment Length Polymorphism), different HCMV strains could be detected and classified in at least four HCMV genotypes. Thirty-three pediatric recipients of renal or bone marrow transplantation were monitored. Twenty out of thirty-three (60.6%) patients demonstrated active HCMV infection. gB1 and gB2 genotypes were more frequent in this population. In this study, we observed that gB2 had correlation with reactivation of HCMV infection and that patients with mixture of genotypes did not show any symptoms of HCMV disease. Future studies has been made to confirm this.

Antigenemia and specific IgM and IgG antibody responses in rabbits infected with Toxoplasma gondii

In this experiment, the correlation between antigenemia and specific antibody responses in Toxoplasma gondii-infected rabbits was assessed. We injected 1,000 T. gondii tachyzoites (RH) subcutaneously into 5 rabbits. Parasitemia, circulating antigens, and IgM and IgG antibody titers in blood were tested by ELISA and immunoblot. For detection of parasitemia, mice were injected with blood from rabbits infected with T. gondii and mice died between days 2 and 10 post-infection (PI). Circulating antigens were detected early on day 2 PI, and the titers increased from day 4 PI and peaked on day 12 PI. Anti-Toxoplasma IgM antibody titers increased on day 6 PI and peaked on days 14-16 PI. IgG was detected from day 10 PI, and the titers increased continuously during the experiment. The antigenic protein patterns differed during the infection period, and the number of bands increased with ongoing infection by the immunoblot analysis. These result indicated that Toxoplasma circulating antigens during acute toxoplasmosis are closely related to the presence of parasites in blood. Also, the circulating antigen levels were closely correlated with IgM titers, but not with IgG titers. Therefore, co-detection of circulating antigens with IgM antibodies may improve the reliability of the diagnosis of acute toxoplasmosis.