Establishment of an international autoantibody reference standard for human anti-DFS70 antibodies: proof-of-concept study for a novel Megapool strategy by pooling individual specific sera.

Background International autoantibody standards, traditionally based on material obtained from plasmapheresis of single subjects, represent individual immune response and may not comprehend the heterogeneity of the general population. The anti-DFS70 autoantibody yields a characteristic dense fine speckled (DFS) nuclear pattern on indirect immunofluorescence assay on HEp-2 cells (HEp-2 IFA) and speaks against autoimmunity. We propose a novel strategy for developing autoantibody reference standards, based on stepwise pooling of serum samples from hundreds of individuals with anti-DFS70 antibodies. Methods Within a 2-year period, serum samples were selected from routine HEp-2 IFA according to the following criteria: DFS HEp-2 IFA pattern at titer ≥1:640; anti-DFS70 reactivity in three analyte-specific tests (Western blot [WB], enzyme-linked immunosorbent assay [ELISA] and chemiluminescent immunoassay [CLIA]). Aliquots of individual samples were combined into progressively larger pools with stepwise validation of intermediary pools as for individual samples. Validated intermediary pools were merged into a final pool for lyophilization. Results A total of 741 validated samples yielded a 750 mL final pool that was lyophilized into thousands of 200 µL-aliquots. Reconstituted aliquots yielded the expected anti-DFS70 reactivity in ELISA, CLIA and WB, as well as high-titer DFS HEp-2 IFA pattern. The appropriate anti-DFS70 reactivity of the lyophilized pool was confirmed by seven international expert centers, using HEp-2 IFA, ELISA, WB and immunoprecipitation. Conclusions This proof-of-concept study provides an innovative and efficient strategy to build serum reference standards for autoantibody testing. The anti-DFS70 standard will integrate the panel of standards of Autoantibody Standardization Committee (ASC, www.autoab.org), contributing to education for proper assay validation and interpretation of the DFS pattern and other HEp-2 IFA patterns.

Etiologies and manifestations of persistent diarrhea in adults with HIV-1 infection: a case-control study in Lima, Peru.

UNLABELLED: OBJECTIVE We sought to determine the etiologies, manifestations, and risk factors for persistent (> or =7 days) diarrhea in human immunodeficiency virus type 1 (HIV-1)-infected persons in Peru. DESIGN: The present study is a case-control study of 147 HIV-1-infected case subjects with persistent diarrhea and 147 HIV-1-infected control subjects without diarrhea. METHODS: We obtained clinical, demographic, and exposure data, CD4 lymphocyte counts, and stool samples for detection of enteric parasitic and bacterial pathogens and rotavirus. RESULTS: One or more enteric pathogen was identified in 55% of case subjects and 21% of control subjects (odds ratio adjusted for CD4 lymphocyte count, 3.8; 95% confidence interval, 2.2-6.5). The median CD4 lymphocyte count was highest with pathogen-free diarrhea and lowest with Cryptosporidium infection. Cryptosporidium species (the most frequent pathogen), Giardia lamblia, Aeromonas species, Campylobacter species, and rotavirus were all significantly associated with diarrhea. Bacterial pathogens were significantly associated with G. lamblia and rotavirus infection. Of the bacterial pathogens (Aeromonas, Campylobacter, Salmonella, and Vibrio species and enterotoxigenic Escherichia coli), only 24% were susceptible to cotrimoxazole, whereas 90% were susceptible to ciprofloxacin. In no case did the sensitivity or positive predictive value of specific clinical and laboratory findings for curable enteric infections exceed 50%. CONCLUSIONS: Several enteric pathogens were associated with diarrhea in HIV-1-infected case subjects in Peru, especially among those who were heterosexual. Clinical findings were poor predictors of detectable microbial etiology. The guidelines for initial management of chronic diarrhea with sulfamethoxazole-trimethoprim in HIV-1-infected persons require revision, at least in settings where prophylaxis with this agent is common.