Novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiologic agent of the ongoing coronavirus disease 2019 (COVID-19) pandemic, which has reached 28 million cases worldwide in 1 year. The serological detection of antibodies against the virus will play a pivotal role in complementing molecular tests to improve diagnostic accuracy, contact tracing, vaccine efficacy testing, and seroprevalence surveillance. Here, we aimed first to evaluate a lateral flow assay's ability to identify specific IgM and IgG antibodies against SARS-CoV-2 and second, to report the seroprevalence estimates of these antibodies among health care workers and healthy volunteer blood donors in Panama. We recruited study participants between April 30th and July 7th, 2020. For the test validation and performance evaluation, we analyzed serum samples from participants with clinical symptoms and confirmed positive RT-PCR for SARS-CoV-2, and a set of pre-pandemic serum samples. We used two by two table analysis to determine the test positive and negative percentage agreement as well as the Kappa agreement value with a 95% confidence interval. Then, we used the lateral flow assay to determine seroprevalence among serum samples from COVID-19 patients, potentially exposed health care workers, and healthy volunteer donors. Our results show this assay reached a positive percent agreement of 97.2% (95% CI 84.2–100.0%) for detecting both IgM and IgG. The assay showed a Kappa of 0.898 (95%CI 0.811–0.985) and 0.918 (95% CI 0.839–0.997) for IgM and IgG, respectively. The evaluation of serum samples from hospitalized COVID-19 patients indicates a correlation between test sensitivity and the number of days since symptom onset; the highest positive percent agreement [87% (95% CI 67.0–96.3%)] was observed at ≥15 days post-symptom onset (PSO). We found an overall antibody seroprevalence of 11.6% (95% CI 8.5–15.8%) among both health care workers and healthy blood donors. Our findings suggest this lateral flow assay could contribute significantly to implementing seroprevalence testing in locations with active community transmission of SARS-CoV-2.
Currently there is a clear trend towards the establishment of virus-like particles (VLPs) as a powerful tool for vaccine development. VLPs are tunable nanoparticles that can be engineered to be used as platforms for multimeric display of foreign antigens. We have previously reported that VLPs derived from rabbit hemorrhagic disease virus (RHDV) constitute an excellent vaccine vector, capable of inducing specific protective immune responses against inserted heterologous T-cytotoxic and B-cell epitopes. Here, we evaluate the ability of chimeric RHDV VLPs to elicit immune response and protection against Foot-and-Mouth disease virus (FMDV), one of the most devastating livestock diseases. For this purpose, we generated a set of chimeric VLPs containing two FMDV-derived epitopes: a neutralizing B-cell epitope (VP1 (140–158)) and a T-cell epitope [3A (21–35)]. The epitopes were inserted joined or individually at two different locations within the RHDV capsid protein. The immunogenicity and protection potential of the chimeric VLPs were analyzed in the mouse and pig models. Herein we show that the RHDV engineered VLPs displaying FMDV-derived epitopes elicit a robust neutralizing immune response in mice and pigs, affording partial clinical protection against an FMDV challenge in pigs.
COVID-19 is the name of the acute respiratory disease caused by the new coronavirus SARS-CoV-2, a close relative of those that caused the severe outbreaks of SARS and MERS several years ago. Since first appearance on December of 2019, the COVID-19 pandemic has cause extremely high levels of mortality, morbidity, global economic breakdown, and the consequent human suffering. The main diagnostic test for the confirmation of symptomatic individuals is the detection of viral RNA by reverse transcriptase–quantitative real time PCR (RT-PCR). Additionally, serology techniques, such as ELISA are useful to measure the antibodies produced in humans after contact with the virus, as well as the direct presence of viral antigens. In this study we aim to assemble and evaluate four ELISA assays to measure the presence of IgG or IgM specific for the viral Spike protein in COVID-19 patients, using either the full recombinant SARS-CoV-2 Spike protein or the fragment corresponding to the receptor binding domain. As a control, we analyzed a group of pre-pandemic serum samples obtained before 2017. Strong reactivity was observed against both antigens. A few pre-pandemic samples displayed high OD values, suggesting the possibility of some cross reactivity. All four assays show very good repeatability, both intra- and inter-assay. Receiver operating characteristic analysis allowed the definition of cutoffs and evaluation of performance for each ELISA by estimation of the area under the curve. This performance parameter was high for all tests (AUC range: 0.98–0.99). Multiple comparisons between tests revealed no significant difference between each other (P values: 0.24–0.95). Our results show that both antigens are effective to detect both specific IgG and IgM antibodies, with high sensitivity (range 0.92–0.99), specificity (range 0.93–0.97) and congruence with the RT-PCR test (Cohen´s Kappa range 0.87–0.93). These assays will allow health authorities to have a new tool to estimate seroprevalence, in order to manage and improve the severe sanitary situation caused by this virus.
bOvine interferon tau (IFN-) is a unique type I interferon with low toxicity and a broad host range in vivo. We report the generation of a nonreplicative recombinant adenovirus expressing biologically active IFN-. Using the B6.A2G-Mx1 mouse model, we showed that single-dose intranasal administration of recombinant Ad5-IFN-can effectively prevent lethality and disease induced by highly virulent hv-PR8 influenza virus by activating the interferon response and preventing viral replication.T ype I interferons (IFN) are crucial inducers of the antiviral response that act by binding to their universally expressed receptor (IFNAR) and regulating the expression of a large set of genes known as interferon-stimulated genes (ISGs) (1). Collectively, these ISGs mediate the establishment of an antiviral state directly precluding or diminishing viral replication within the cell (1, 2). Additionally, IFN modulates the deployment of a correct adaptive antiviral immune response by acting on cells of the immune system. For these reasons, IFN has long been thought of as an important antiviral treatment option (3, 4). However, its use in clinical settings as a broad-spectrum antiviral agent has been delayed due to its short half-life and the toxicity associated with its systemic or sustained delivery (5-8).Therefore, vectors for a localized delivery and tailoring of the signaling properties of IFN are important goals. Recently, adenoviral vectors expressing type I IFN have been generated and shown to be efficient in the prevention of a number of viral diseases in vertebrate hosts, including SARS coronavirus infections in ferrets and Ebola virus infection in macaques (9-12). IFN-is a type I interferon expressed in ruminants only which is known to induce low toxicity while maintaining its antiviral capacities (6,(13)(14)(15)(16)(17)(18). In contrast to other type I IFNs, IFN-can act on receptors from a broad range of species (17,19), and it has shown efficacy in reducing replication of different viruses, including human and feline immunodeficiency viruses (HIV and FIV), human papillomavirus (HPV) (7,20,21), and bovine leukemia virus (BKV) (8).Thus, we generated a recombinant nonreplicative second-generation human adenovirus (method previously described [22]), termed Ad5-IFN-, as a vector for the local delivery of IFN-in vivo (23). We first tested the ability of Ad5-IFN-to drive the expression and secretion of active IFN-. To do so, we assayed increasing amounts of medium from Vero cells, which lack endogenous type I IFN genes, infected with Ad5-IFN-or the parental control Ad5-DsRed virus and harvested at 48 h postinfection (hpi) in an antiviral activity assay. Vero cells were protected in a dose-dependent manner from vesicular stomatitis virus (VSV) infection when incubated with different amounts of the conditioned medium from Ad5-IFN--infected cells (Fig. 1A), indicating the presence of a secreted antiviral activity most likely corresponding to IFN-. As expected, control medium did not prevent VSV infection and showed no toxicity to...
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