Comparison of Commercial ELISA Kits to Confirm the Absence of Transmission in Malaria Elimination Settings
Background: Antimalarial antibody measurements are useful because they reflect historical and recent exposure to malaria. As such, they may provide additional information to assess ongoing transmission in low endemic or pre-elimination settings where cases are rare. In addition, the absence of antibody responses in certain individuals can indicate the cessation of transmission.
Commercial malaria enzyme-linked immunosorbent assays (ELISA) detect antimalarial antibodies and are commonly used to screen blood donations for possible malaria infection. However, there is no standardized test to detect antimalarial antibodies for epidemiological use. Here we compared five commercially available ELISA kits (Trinity Biotech, newbio, DiaPro, Cellabs, and NovaTec) in search of a standardized tool for supporting claims of absence of malaria transmission. For comparison, a research-based (RB) ELISA protocol was performed alongside the commercial kits.
Results: The commercial kits were first compared using serum samples from known malaria-unexposed individuals (n = 223) and Toxoplasma-infected individuals (n = 191) to assess specificity and cross-reactivity against non-malaria infections. In addition, 134 samples from ≥10-year-olds collected in a hyperendemic region in the Gambia in the early 1990s were used to assess sensitivity. Three out of five kits showed high sensitivity (90-92%), high specificity (98-99%), low cross-reactivity (0-3%) and were considered user-friendly (Trinity Biotech, newbio and NovaTec).
Two of these kits (Trinity Biotech and NovaTec) were taken forward for epidemiological evaluation and results were compared to those using the RB-ELISA. Samples from two pre-elimination settings (Praia, Cape Verde; n = 1,396, and Bataan, the Philippines; n = 1,824) were tested.
Serological results from both the Trinity Biotech kit and the RB-ELISA concurred with recent passively detected case counts in both settings. Results from the Trinity Biotech kit reflected a significant decrease in the number of reported cases in Bataan in the 1990s better than the RB-ELISA. Results from the NovaTec kit did not reflect transmission patterns in either setting.
Conclusion: The Trinity Biotech commercial ELISA kit was considered reliable for epidemiological use and accurately described transmission patterns in two (previously) malaria endemic settings. The use of this simple and standardized serological tool may aid national control and elimination programs by confirming that regions are free from malaria.
A dual antigen ELISA allows the assessment of SARS-CoV-2 antibody seroprevalence in a low transmission setting
Estimates of seroprevalence of SARS-CoV-2 antibodies have been hampered by inadequate assay sensitivity and specificity. Using an ELISA-based approach that combines data about IgG responses to both the Nucleocapsid and Spike-receptor binding domain antigens, we show that excellent sensitivity and specificity can be achieved.
We used this assay to assess the frequency of virus-specific antibodies in a cohort of elective surgery patients in Australia and estimated seroprevalence in Australia to be 0.28% (0 to 1.15%). These data confirm the low level of transmission of SARS-CoV-2 in Australia before July 2020 and validate the specificity of our assay.
Serological cross-reactivity using a SARS-CoV-2 ELISA test in acute Zika virus infection, Colombia
Objectives: We investigated seroreactivity, using a commercial SARS-CoV-2 ELISA test, in samples collected from different individuals’ groups, including patients diagnosed as Dengue, Zika, and Chikungunya infection during 2015 and 2019, from an endemic area at the Caribbean Colombian region.
Methods: A total of 127 sera, obtained from six different groups of individuals, were included in this study: Group A: patients with confirmed SARS-CoV-2 infection; Group B: patients with symptoms suggestive of COVID-19 or asymptomatic contacts of confirmed patients; Group C: patients with acute or recent dengue virus infection; Group D: patients with acute Zika virus infection; Group E: patients with previous Chikungunya virus infection; and Group F: individuals with exposure to spotted fever group rickettsiae.
Results: Overall, group A, group B, and group D showed seroreactivity to SARS-CoV-2 in 92%, 75%, and 26% of samples, respectively; meanwhile, group C, group E, and group F showed 100% of seronegative.
Conclusions: We found 26% of serological cross-reactivity in patients with acute Zika virus infection using a commercial SARS-CoV-2 ELISA test. Further studies could evaluate if serological cross-reaction is maintaining along the time in a non-acute patient with previous exposure to the Zika virus and its effect in SARS-CoV-2 serosurveys in endemic areas for this arbovirus.
Development and Optimization of In-house ELISA for Detection of Human IgG Antibody to SARS-CoV-2 Full Length Spike Protein
- The ongoing coronavirus disease 19 (COVID-19) pandemic, caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), poses a threat to human health. Despite this, many affected countries are now in the process of gradual lifting of COVID-19 restrictions that were initially implemented in response to the pandemic.
- The success of the so-called “exit strategy” requires continued surveillance of virus circulation in the community and evaluation of the prevalence of protective immunity among population. Serology tests are valuable tools for these purposes. Herein, SARS-CoV-2 full-length spike (S) recombinant protein was utilized to develop and optimize an indirect enzyme-linked immunoassay (ELISA) that enables a reliable detection of virus-specific IgG antibody in human sera.
- Importantly, the performance of this assay was evaluated utilizing micro-neutralization (MN) assay as a reference test. Our developed ELISA offers 100% sensitivity, 98.4% specificity, 98.8% agreement, and high overall accuracy. Moreover, the optical density (OD) values of positive samples significantly correlated with their MN titers.
- The assay specifically detects human IgG antibodies directed against SARS-CoV-2, but not those to Middle East respiratory syndrome coronavirus (MERS-CoV) or human coronavirus HKU1 (HCoV-HKU1). The availability of this in-house ELISA protocol would be valuable for various diagnostic and epidemiological applications.
Detection of Cannabinoids by LC-MS-MS and ELISA in Breast Milk
Cannabis is the most commonly used drug of abuse in pregnancy and after delivery. However, little is known regarding the disposition of cannabinoids in breast milk, although delta-9-tetrahydrocannabinol (THC), the main psychoactive component, is highly lipophilic. Quantification of cannabinoids in breastmilk is essential for clinical monitoring and research studies and breastmilk banks mainly rely on ELISA in terms of screening for cannabinoids.
To support clinical studies on disposition of cannabinoids in breastmilk, we validated a high-performance liquid chromatography-tandem mass spectrometry (LC-MS-MS) assay for the simultaneous quantification of 12 cannabinoids and their metabolites in human breast milk. Said assay was based upon a simple one-step protein precipitation, online column extraction and detection in the positive multiple reaction monitoring mode.
After successful validation, the assay was used to analyze 30 samples from a clinical research study that had tested negative using an ELISA kit that is commonly used by breastmilk banks. In human breast milk, depending on the analyte, the lower limits of quantification of the LC-MS-MS assay ranged from 0.39 to 7.81 ng/mL. Acceptance criteria for intra- and inter-batch accuracy (85-115%) and imprecision (<15%) were met for all compounds.
Mean extraction efficiencies were above 60% for all analytes. Mean matrix effect ranged from -12.5% to 44.5% except of THC- glucuronide for which significant matrix effects were noted. No carry-over was detected. Although cannabinoid-negative based on the ELISA, all 30 samples tested positive for THC using LC-MS-MS (0.8-130 ng/mL) and several also for 11-OH-THC, THCCOOH, CBD and CBG. We validated a sensitive and specific assay for the quantification of 12 cannabinoids in human breastmilk that outperformed an ELISA commonly used by breastmilk banks.