All data were analysed with LC96 software version 1
All data were analysed with LC96 software version 1.1. microarray work has used serum as the sample matrix, requiring quick laboratory processing and a continuous cold chain, therefore limiting applications in remote locations. Dried blood spots (DBS) pose minimal biohazard, do not require immediate laboratory processing, and are stable at room heat for transport, making them potentially superior alternatives to serum. The goals of this study were to assess the viability of DBS as a source for antibody profiling and to use DBS to identify serological signatures of low-density infections in malaria-endemic regions of Myanmar. Methods Matched DBS and serum samples from a cross-sectional study in Ingapu Township, Myanmar were probed on protein microarrays populated with antigen fragments. Signal and trends in both sample matrices were compared. A case-control study was Brevianamide F then performed using banked DBS samples from malaria-endemic regions of Myanmar, and a regularized logistic regression model was used to identify antibody signatures of ultrasensitive PCR-positive infections. Results Approximately 30% of serum IgG activity was recovered from DBS. Despite this loss of antibody activity, antigen and populace trends were well-matched between the two sample matrices. Responses to 18 protein fragments were associated with the odds of asymptomatic contamination, albeit with Brevianamide F modest diagnostic characteristics (sensitivity 58%, specificity 85%, unfavorable predictive value 88%, and positive predictive value 52%). Conclusions Malaria-specific antibody responses can be reliably detected, quantified, and analysed from DBS, opening the door to serological studies in populations where serum collection, transport, and storage would otherwise be impossible. While test characteristics of antibody signatures were insufficient for individual diagnosis, serological testing may be useful for identifying exposure to asymptomatic, low-density malaria infections, particularly if sero-surveillance strategies target individuals with low previous exposure as sentinels for populace exposure. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03915-8. 3D7 reference genome (Pf250) . It was also hypothesized that long-term exposure to low-density infections, which have been shown to persist for months , may elicit antibody signatures that could serve as biomarkers of contamination. This hypothesis was tested by probing DBS on protein microarrays to identify antibody responses as markers for usPCR-positive (usPCR+) malaria infections. Methods Study settings and participants A cross-sectional study was conducted in Ingapu Township, Myanmar, during the rainy season in August 2018. This region was previously characterized by the Myanmar National Malaria Control Programme as a medium-transmission area, with reported usPCR Brevianamide F prevalence of 8.7% infections and 5.6% infections during the rainy season in 2015 . A study carried Brevianamide F out in 2015 found the annual parasite index (API) in the region to be 1C5 malaria cases per 1000 individuals under surveillance per year . Individuals aged 6 months or older, including pregnant women and the elderly, were enrolled in the study after provision of written informed consent. Parents/guardians provided written consent for participants younger than 18 years old. Written assent was also provided by children age 8 to 17 years of age. Enrollment in the study was offered to individuals attending a mobile clinic staffed by local public health volunteers. One hundred individuals were enrolled. To identify potential markers of asymptomatic usPCR+?malaria infections, a retrospective case-control study nested within a previously reported 2015 cross-sectional survey  in which participants provided consent for additional analysis of samples was performed. Samples originated from Injanyang and Ann Townships, both of which have reported API? ?5 cases per 1000 individuals under surveillance per year . No participants reported malaria Brevianamide F symptoms, nor were any RDT-positive. Antibody responses were measured from archived case and control DBS samples on Protein Saver 903 Cards. Cases (n?=?50) were individuals who tested positive for by usPCR, and controls (n?=?175) were individuals who tested negative for by usPCR. This study was designed specifically to identify antibody markers of usPCR+?malaria PIK3C2G infections, so individuals with mixed and mono-infections were included in the.