Background Serological diagnosis of Zika virus (ZIKV) infection is challenging because of the antibody cross-reactivity among flaviviruses. At the same time, the role of Nucleic Acid Testing (NAT) is limited by the low proportion of symptomatic infections and the low average viral load. Here, we compared the diagnostic performance of commercially available IgM, IgAM, and IgG ELISAs in sequential samples during the ZIKV and chikungunya (CHIKV) epidemics and co-circulation of dengue virus (DENV) in Brazil and Venezuela. Methodology/Principal findings Acute (day of illness 1–5) and follow-up (day of illness ≥ 6) blood samples were collected from nine hundred and seven symptomatic patients enrolled in a prospective multicenter study of symptomatic patients recruited between June 2012 and August 2016. Acute samples were tested by RT-PCR for ZIKV, DENV, and CHIKV. Acute and follow-up samples were tested for IgM, IgAM, and IgG antibodies to ZIKV using commercially available ELISAs. Among follow-up samples with a RT-PCR confirmed ZIKV infection, anti-ZIKV IgAM sensitivity was 93.5% (43/48), while IgM and IgG exhibited sensitivities of 30.3% (10/35) and 72% (18/25), respectively. An additional 24% (26/109) of ZIKV infections were detected via IgAM seroconversion in ZIKV/DENV/CHIKV RT-PCR negative patients. The specificity of anti-ZIKV IgM was estimated at 93% and that of IgAM at 85%. Conclusions/Significance Our findings exemplify the challenges of the assessment of test performance for ZIKV serological tests in the real-world setting, during co-circulation of DENV, ZIKV, and CHIKV. However, we can also demonstrate that the IgAM immunoassay exhibits superior sensitivity to detect ZIKV RT-PCR confirmed infections compared to IgG and IgM immunoassays. The IgAM assay also proves to be promising for detection of anti-ZIKV seroconversions in sequential samples, both in ZIKV PCR-positive as well as PCR-negative patients, making this a candidate assay for serological monitoring of pregnant women in future ZIKV outbreaks.

STRUCTURED ABSTRACTBackground and ObjectivesMuscular dystrophies associated with decreased sarcolemma integrity lack validated clinical measures of sarcolemma fragility that can be used to assess disease progression and the effects of therapies designed to reduce sarcolemma fragility. We conducted a pilot study to test the hypothesis that physical activity leads to significant changes in muscle-derived plasma enzymes in participants with “fragile sarcolemmal muscular dystrophies” (FSMD).MethodsWe enrolled ambulatory individuals clinically affected with genetically confirmed FSMD neither taking anti-inflammatory medications nor having relevant co-morbidities for an inpatient study. Over five days, blood samples at 20 time points were obtained. Plasma enzymes alanine and aspartate aminotransferase (ALT, AST), creatine kinase (CK), and lactate dehydrogenase (LDH), all found in muscle, were measured before and after routine morning activities and motor function testing. Analysis of Z-transformed time series data led to feature and kinetic models that revealed activity-dependent feature and kinetic parameters.ResultsAmong the 11 enrolled participants, (LGMD Type 2B/R2 Dysferlin-related (4F/1M), LGMD Type 2L/R12 Anoctamin-5-related (3F/2M), LGMD Type 2I/R9 FKRP-related (1M)), plasma enzymes increased with activity. The average % change +/- SEM with morning activity across all participants was ALT 12.8 ± 2.8%, AST 11.6 ± 2.9%, CK 12.9 ± 2.8%, and LDH 12.2 ± 3.9%, suggesting the increases originate from the same stimulated source, presumably skeletal muscle. For ALT, AST, CK, and LDH, characteristic kinetic features include (a) elevated enzyme activities on arrival that decreased overnight; (b) a longer decay trend observed over the week, and (c) for ALT, AST, and CK, a similar decay trend observed with post-morning activity blood draws.DiscussionControlled activity-dependent changes in plasma ALT, AST, and CK on time scales of days to weeks can serve as common outcome measures for sarcolemma integrity and may be efficient and effective tools for monitoring disease progression and treatment efficacy for both individuals and patient populations. In addition, this study provides data that may benefit patient management as it can inform guidance on duration and type of activity that minimizes muscle damage.

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