Poor performance of the rapid test for human brucellosis in health facilities in Kenya

Human brucellosis is considered to be an important but typically under-diagnosed cause of febrile illness in many low and middle-income countries. In Kenya, and throughout East Africa, laboratory diagnosis for the disease is based primarily on the febrile antigen Brucella agglutination test (FBAT), yet few studies of the diagnostic accuracy of this test exist. Assessment of the performance of the FBAT is essential for its appropriate clinical use, as well as for evaluating surveillance data reported by public health systems. To assess FBAT performance, we collected sera from people with symptoms compatible with brucellosis attending two health facilities in Busia County, Kenya. Sera were tested using the FBAT and results compared with those from the Rose Bengal Test (RBT), an assay with well-known performance characteristics. Positives on either test were confirmed using the classical serum agglutination test (SAT)-Coombs test combination and a rapid IgM/IgG lateral flow immunochromatography assay (LFA). A questionnaire focussing on known risk factors for exposure to Brucella spp. was also conducted, and relationships with FBAT positivity examined using logistic regression. Out of 825 recruited individuals, 162 (19.6%) were classified as positive using the FBAT. In contrast, only eight (1.0%) were positive using the RBT. Of the 162 FBAT positives, one (0.62%) had an atypical agglutination in SAT and three (1.9%) showed low Coombs titres. Out of 148 FBAT positive individuals tested using the LFA, five (3.4%) were IgM positive and none were IgG positive. Poor or no correlation was observed between FBAT results and most established risk factors for Brucella infection. We observed substantial disagreement between the FBAT and a number of well-known serological tests, with the majority of reactive FBAT results appearing to be false positives. Poor FBAT specificity, combined with a lack of confirmatory testing, strongly suggests overdiagnosis of brucellosis is common in this low prevalence setting. This is expected to have important economic impacts on affected patients subjected to the long and likely unnecessary courses of multiple antibiotics required for treatment of the disease

Systems Biology Approach Predicts Antibody Signature Associated with Brucella melitensis Infection in Humans

A complete understanding of the factors that determine selection of antigens recognized by the humoral immune response following infectious agent challenge is lacking. Here we illustrate a systems biology approach to identify the antibody signature associated with Brucella melitensis (Bm) infection in humans and predict proteomic features of serodiagnostic antigens. By taking advantage of a full proteome microarray expressing previously cloned 1406 and newly cloned 1640 Bm genes, we were able to identify 122 immunodominant antigens and 33 serodiagnostic antigens. The reactive antigens were then classified according to annotated functional features (COGs), computationally predicted features (e.g., subcellular localization, physical properties), and protein expression estimated by mass spectrometry (MS). Enrichment analyses indicated that membrane association and secretion were significant enriching features of the reactive antigens, as were proteins predicted to have a signal peptide, a single transmembrane domain, and outer membrane or periplasmic location. These features accounted for 67% of the serodiagnostic antigens. An overlay of the seroreactive antigen set with proteomic data sets generated by MS identified an additional 24%, suggesting that protein expression in bacteria is an additional determinant in the induction of Brucella-specific antibodies. This analysis indicates that one-third of the proteome contains enriching features that account for 91% of the antigens recognized, and after B. melitensis infection the immune system develops significant antibody titers against 10% of the proteins with these enriching features. This systems biology approach provides an empirical basis for understanding the breadth and specificity of the immune response to B. melitensis and a new framework for comparing the humoral responses against other microorganisms

A Case of Cryptococcal Lymphadenitis in HIV: A Chance Diagnosis by Fine Needle Aspiration Cytology

A 15 years old boy was presented with inguinal lymphadenopathy. The fine needle aspiration of lymph node revealed budding yeast cells and Cryptococcus neoformans was isolated on culture of the aspirate. On further investigations, patient was found to be Human Immunodeficiency Virus (HIV) positive with low CD4 count of 207cells/μl. Patient showed good response with antifungal and antiretroviral treatment. Cryptococcosis is the most common, life threatening, opportunistic, fungal disease in HIV infected individuals. Lung, meninges and skin involvement have been described. Lymph node involvement in cryptococcosis is considered to be rare. Therefore a prompt diagnosis is mandatory for early initiation of specific treatment. We report here a case of cryptococcosis presenting as inguinal lymphadenopathy and diagnosed on fine needle aspiration cytology

Serum sICAM, sVCAM and sE-selectin levels in colorectal cancer patients.

Colorectal cancer (CRC) is one of the most common cancers of the gastrointestinal tract and the fourth cause of cancers death in the world. Soluble adhesion molecules (CAMs) are thought to have an important role in host defense against carcinogenesis. They are biomarkers of inflammation and indicators of the immune response to tumors. The study included 40 CRC patients without remote metastases and 24 control subjects. Serum concentrations of sE-selectin, sICAM and sVCAM in patients with CRC were investigated by ELISA method. The level of the sCAMs decreased significantly after radical tumor resection. Preoperative serum concentrations of sICAM and sVCAM in CRC patients were significantly higher compared to the control group, whereas there were no differences regarding serum sE-selectin. Serum levels of sE-selectin, sICAM and sVCAM correlated significantly with each other. There was a significant correlation of serum levels of sICAM-1 and sVCAM-1, but not sE-selectin, with TNM stage and lymph node involvement. No significant relationship was found between serum concentrations of sICAM-1, sVCAM-1 and sE-selectin in CRC patients and patients' age or gender. Our findings suggest that an improved understanding of the mechanisms of membrane shedding of sICAM, sVCAM and sE-selectin is required to delineate their role in tumor progression