Biology subjects

Van Slyke, G.

Publications and source records attributed to Van Slyke, G..

6 recordsLinked to original sources

bioRxiv2024

Quantitating SARS-CoV-2 Neutralizing Antibodies from Human Dried Blood Spots

BackgroundIn the earliest days of COVID-19 pandemic, the collection of dried blood spots (DBS) enabled public health laboratories to undertake population-scale seroprevalence studies to estimate rates of SARS-CoV-2 exposure. With SARS-CoV-2 seropositivity levels now estimated to exceed 94% in the United States, attention has turned to using DBS to assess functional (neutralizing) antibodies within cohorts of interest. MethodsContrived DBS eluates from convalescent, fully vaccinated and pre-COVID-19 serum samples were evaluated in SARS-CoV-2 plaque reduction neutralization titer (PRNT) assays, a SARS-CoV-2 specific 8-plex microsphere immunoassay, a cell-based pseudovirus assay, and two different spike-ACE2 inhibition assays, an in-house Luminex-based RBD-ACE2 inhibition assay and a commercial real-time PCR-based inhibition assay (NAB-Sure). ResultsDBS eluates from convalescent individuals were compatible with the spike-ACE2 inhibition assays, but not cell-based pseudovirus assays or PRNT. However, the insensitivity of cell-based pseudovirus assays was overcome with DBS eluates from vaccinated individuals with high SARS-CoV-2 antibody titers. ConclusionSARS-CoV-2 neutralizing titers can be derived with confidence from DBS eluates, thereby opening the door to the use of these biospecimens for the analysis of vulnerable populations and normally hard to reach communities.

immunology↗

bioRxiv2023

Effects of aluminum-salt, CpG and emulsion adjuvants on the stability and immunogenicity of a virus-like particle displaying the SARS-CoV-2 receptor binding domain (RBD)

Second-generation COVID-19 vaccines with improved immunogenicity (e.g., breadth, duration) and availability (e.g., lower costs, refrigerator stable) are needed to enhance global coverage. In this work, we formulated a clinical-stage SARS-CoV-2 receptor binding domain (RBD) virus-like particle (VLP) vaccine candidate (IVX-411) with widely available adjuvants. Specifically, we assessed the in vitro storage stability and in vivo mouse immunogenicity of IVX-411 formulated with aluminum-salt adjuvants (Alhydrogel, AH and Adjuphos, AP), without or with the TLR-9 agonist CpG-1018 (CpG), and compared these profiles to IVX-411 adjuvanted with an oil-in-water nano-emulsion (AddaVax, AV). Although IVX-411 bound both AH and AP, lower binding strength of antigen to AP was observed by Langmuir binding isotherms. Interestingly, AH- and AP-adsorbed IVX-411 had similar storage stability profiles as measured by antigen binding assays (competitive ELISAs), but the latter displayed higher pseudovirus neutralizing titers (pNT) in mice, at levels comparable to titers elicited by AV-adjuvanted IVX-411. CpG addition to alum (AP or AH) resulted in a marginal trend of improved pNTs in stressed samples only, yet did not impact the storage stability profiles of IVX-411. In contrast, previous work with AH-formulations of a monomeric RBD antigen showed greatly improved immunogenicity and decreased stability upon CpG addition to alum. At elevated temperatures (25, 37{degrees}C), IVX-411 formulated with AH or AP displayed decreased in vitro stability compared to AV-formulated IVX-411and this rank-ordering correlated with in vivo performance (mouse pNT values). This case study highlights the importance of optimizing antigen-adjuvant interactions to develop low cost, aluminum-salt adjuvanted recombinant subunit vaccine candidates.

immunology↗

bioRxiv2022

The Flexible Linker of Decorin Binding Protein A from Borrelia burgdorferi is a Target of Antibodies in Lyme disease

Decorin binding protein A (DbpA) is a surface adhesin expressed by Borrelia burgdorferi, the causative agent of Lyme disease. While DbpA is one of the most immunogenic B. burgdorferi antigens in Lyme disease patients, the B cell epitopes recognized over the course of infection have not been defined. In this report we profiled [~]300 human serum samples from early, mid, and late-stage Lyme disease for IgM and IgG reactivity with DbpA and a tiled DbpA 18-mer peptide array derived from B.b. strains B31 and 297. Using ELISA and multiplex immunoassays (MIA), we identified 12 DbpA-derived peptides whose reactivity was elevated in Lyme disease patients as compared to healthy controls. The most reactive peptide ("A7") corresponds to the flexible loop between DbpAB31 -helix 1 and -helix 2, implicated in influencing DbpA binding to heparin and dermatan sulfate. An A7-like peptide is also reportedly a target of antibodies in Lyme neuroborreliosis patients. The remaining peptides, while highly reactive in serum samples across disease stages, likely represent non-native epitopes, as antibody reactivity to a subset of peptides in competition assays was unaffected by the addition of soluble DbpA. Moreover, peptide reactivity of any given patient sample rarely correlated with overall DbpA antibody levels, suggesting the antibodies were raised against DbpA degradation products. Insights into B cell epitopes on DbpA elicited during Lyme disease have important implications for understanding how B.burgdorferi persists in the face of an overwhelming antibody response. IMPORTANCEThe bacterium, Borrelia burgdorferi, is the causative agent of Lyme disease, the most reported tick-borne illness in the United States. In humans, clinical manifestations of Lyme disease are complex and can persist for months, even in the face of a robust antibody response directed against numerous B. burgdorferi surface proteins, including decorin binding protein A (DbpA), which is involved in early stages of infection. In this study we employed [~]300 serum samples from Lyme disease patients to better understand antibody reactivity with specific regions ("epitopes") of DbpA. We identified one epitope on DbpA recognized by antibodies from almost half of the serum samples tested and that, theoretically, should block DbpAs ability to function in promoting B. burgdorferi colonization of human hosts.

immunology↗

bioRxiv2020

Assessment of sample pooling for clinical SARS-CoV-2 testing

Accommodating large increases in sample workloads has presented one of the biggest challenges to clinical laboratories during the COVID-19 pandemic. Despite the implementation of new automated detection systems, and previous efficiencies such as barcoding, electronic data transfer and extensive robotics, throughput capacities have struggled to meet the demand. Sample pooling has been suggested as an additional strategy to further address this need. The greatest concern with this approach in a clinical setting is the potential for reduced sensitivity, particularly the risk of false negative results when weak positive samples are pooled. To investigate this possibility, detection rates in pooled samples were evaluated, with extensive assessment of pools containing weak positive specimens. Additionally, the frequency of occurrence of weak positive samples across ten weeks of the pandemic were reviewed. Weak positive specimens were detected in all five-sample pools but failed to be detected in four of the 24 nine-sample pools tested. Weak positive samples comprised an average 16.5% of the positive specimens tested during the pandemic thus far, slightly increasing in frequency during later weeks. Other aspects of the testing process should be considered, however, such as accessioning and reporting, which are not streamlined and may be complicated by pooling procedures. Therefore, the impact on the entire laboratory process needs to be carefully assessed prior to implementing such a strategy.

microbiology↗

bioRxiv2020

Endpoint and Epitope-specific Antibody Responses as Correlates of Vaccine-mediated Protection of Mice against Ricin Toxin

The successful licensure of vaccines for biodefense is contingent upon the availability of well-established correlates of protection (CoP) in at least two animal species that can then be applied to humans, without the need to assess efficacy in the clinic. In this report we describe a multivariate model that combines pre-challenge serum antibody endpoint titers (EPT) and values derived from an epitope profiling immune-competition capture (EPICC) assay as a predictor in mice of vaccine-mediated immunity against ricin toxin (RT), a Category B biothreat. EPICC is a modified competition ELISA in which serum samples from vaccinated mice were assessed for their ability to inhibit the capture of soluble, biotinylated (b)-RT by a panel of immobilized monoclonal antibodies (mAbs) directed against four immunodominant toxin-neutralizing regions on the enzymatic A chain (RTA) of RT. In a test cohort of mice (n=40) vaccinated with suboptimal doses of the RTA subunit vaccine, RiVax(R), we identified two mAbs, PB10 and SyH7, which had EPICC inhibition values in pre-challenge serum samples that correlated with survival following a challenge with 10 x LD50 of RT administered by intraperitoneal (IP) injection. Analysis of a larger cohort of mice (n=645) revealed that a multivariate model combining endpoint titers and an epitope-profiling immune-competition capture (EPICC) assay values for PB10 and SyH7 as predictive variables had significantly higher statistical power than any one of the independent variables alone. Establishing the correlates of vaccine-mediated protection in mice represents an important steppingstone in the development of RiVax(R) as a medical countermeasure under the United States Food and Drug Administrations "Two Animal Rule."

immunology↗

bioRxiv2018

Fine Specificity Epitope Analysis by HX-MS Identifies Contact Points on Ricin Toxin Recognized by Protective Monoclonal Antibodies

Ricin is a fast-acting protein toxin classified by the Centers for Disease Control and Prevention as a biothreat agent. In this report we describe five new mouse monoclonal antibodies (mAbs) directed against an immunodominant region, so-called epitope cluster II, on the surface of ricins ribosome-inactivating enzymatic subunit, RTA. The five mAbs were tested alongside four previously described cluster II-specific mAbs for their capacity to passively protect mice against 10 x LD50 ricin challenge by injection. Only three of the mAbs (LE4, PH12 and TB12) afforded protection over the seven-day study period. Neither binding affinity nor in vitro toxin-neutralizing activity could fully account for LE4, PH12 and TB12s potent in vivo activity relative to the other six mAbs. However, epitope mapping studies by hydrogen exchange-mass spectrometry (HX-MS) revealed that LE4, PH12 and TB12 shared common contact points (i.e., \"strong\" protection by HX-MS) on RTA that encompassed residues 154-164 and 62-69, which correspond to RTA -helices D-E and {beta}-strands d-e, respectively, located on the back side of RTA relative to the active site. The other six mAbs recognized overlapping epitopes on RTA but none shared the same HX-MS profile as LE4, PH12 and TB12. A high-density competition ELISA with a panel of ricin-specific single domain camelid antibodies (VHHs) indicated that even though LE4, PH12 and TB12 make contact with similar secondary motifs, they ultimately approach RTA different from angles. These results underscore how subtle differences in epitope specificity have significant impacts on the antibody functionality in vivo and have important implications in the design of immune-based countermeasures against ricin.

immunology↗