An article published by Alana L. Whitcombe et al at The University of Auckland, New Zealand in the January 2022 issue of Journal of Immunological Methods, reported on development of an eight-plex immunoassay from both serum and dried blood samples. The paper is entitled “An eight-plex immunoassay for Group A streptococcus serology and vaccine development.”
It describes the development and validation of a high sensitivity multiplex ligand binding assay for serological assays and vaccine development of Group A streptococcus (GAS) infection. The method deployment was highly successful, and the authors commented that this 8-plex assay '"will be a powerful tool for simultaneously measuring the prevalence and dynamics of GAS antibodies in populations affected by GAS disease to inform GAS vaccine development.”
Group A streptococcus (GAS) infections cause a wide range of problems ranging from strep throat to scarlet fever and the skin condition impetigo. Antibiotics are used to effectively treat these bacterial infections, but it is estimated that there are 1.78 million new GSA cases worldwide each year, with more than 500,000 individuals succumbing to complications from severe GAS diseases.
One such complication is rheumatic heart disease (RHD), an inflammatory autoimmune disorder resulting from rheumatic fever that permanently damages the heart valves, impairing heart function. Indeed, it is estimated that out of the 500,000 deaths linked to GAS, 320,000 are as a result of RDH.
The Covid-19 pandemic has demonstrated the incredible efficacy of vaccines for helping to prevent severe SARS-CoV-2 infections, which can result in serious complications. Just as vaccines have been a major step forward in the battle against Covid-19, they could have a similar impact in preventing GAS infections and the related disease complications, such as rheumatic fever and RHD.
There are several GAS vaccines in development, some of which target the M-protein. Yet, because there are at least 200 variants of M-protein, targeting it for vaccines is challenging. There are, however, a few conserved proteins too, which are more appealing as vaccine targets. It is hoped that combined vaccines will be able to cover > 98% of all GAS agents.
There are several ways to diagnose GAS, such as via bacterial swab & culturing. Serology is another popular way to test for GAS and targets such as Streptolysin O (SLO), which is a cytolytic toxin released by GAS. Another popular target for such assays is DNaseB, an extracellular virulent protein with DNA-degrading activity.
The same research group at the University of Auckland had previously developed a 3-plex assay to look at these SLO and DNaseB targets as well as a novel target (SpnA). The group’s goal for this current project was to add to their 3-plex array with 5 antigens obtained from vaccine development.
They also wanted to look at a subset of paired venous blood to serum samples to confirm that this assay would also be compatible for dried blood samples collected remotely with microsampling devices, such as DBS or VAMS. With this more comprehensive list of targets tested on serum and dried blood, they hoped that the assay would provide “the possibility for serosurveillance and vaccine antigen response studies to be more readily conducted in remote settings and high-risk populations.”
The research group in New Zealand manufactured and purified recombinant proteins for a number of the of the antigens, however SpyCEP, SpyAD and the GAC were supplied by the GSK Vaccines Institute for Global Health.
Coupling finger-prick sampling with new high-sensitivity multiplex immunoassays, is enabling a new frontier of serological and vaccine science. Indeed, this approach was used with great success in the Covid-19 pandemic, providing a valuable insight into the serological landscape of the disease as well as vaccine efficacy.
Interestingly, such an approach was described in the 2019 paper by J Wang et al in a related serology study measuring > 30 strains of influenza using remotely collected VAMS microsamples. It is good to see that in only three years, remote approaches are becoming successful for a progressively wider range of antibody assays.
This study paper was summarized for our readers by James Rudge, PhD, Neoteryx Technical Director. This is curated content. To learn more about the important research outlined in this review, visit the original article published in the Journal of Immunological Methods.
Image Credit: Vaccine Research, iStock