Immunogenicity testing is central to vaccine development, helping researchers determine whether a vaccine candidate can elicit a protective immune response. But for many assays, especially serum bactericidal assays (SBA) and opsonophagocytic killing assays (OPKA), the presence of naturally occurring antibodies in human serum sources can interfere with results.
Pel-Freez has developed a scalable, validated method for removing select immunoglobulins (IgG, IgM, and IgA) from native human complement—without compromising its functional activity. The result is a reagent that’s gaining traction among vaccine developers who need to reduce variability and increase confidence in their immunogenicity testing results.
Antibody-depleted human complement helps vaccine researchers minimize background interference
Researchers developing vaccines need to clearly measure how effectively vaccine candidates stimulate protective immune responses. But common immunogenicity assays, like SBA and OPKA, depend heavily on complement sources that can unintentionally introduce variability.
Traditionally, researchers have faced a significant hurdle: complement sources derived from human serum often contain preexisting antibodies from prior infections or vaccinations, leading to ambiguous assay results. At Pel-Freez, our team sought to solve this problem by efficiently manufacturing large batches of antibody-depleted human complement (ADHC), offering vaccine researchers a cleaner starting point for assays.
Preexisting antibodies create background noise, complicating assay interpretation
Human complement serum used in assays inevitably contains naturally occurring (IgG, IgM, and/or IgA) from donor exposure to common pathogens or prior vaccinations. These antibodies activate the complement cascade independently of vaccine-induced antibodies, resulting in elevated background activity and unreliable assay results. This variability significantly complicates data interpretation and reproducibility, a critical challenge for both research and commercial assay workflows.
Previously, labs attempted to manage this issue by identifying rare seronegative donors or performing complex, time-consuming antibody depletion in-house, both resource-intensive and impractical solutions.
Pel-Freez's antibody depletion preserves complement function and essential proteins
Our team developed a proprietary process to selectively remove IgG, IgM, and IgA from pooled human serum at liter-scale volumes. Crucially, this method preserves complement function, other major serum fractions, and critical matrix proteins. By maintaining the complement cascade's integrity, Pel-Freez ADHC ensures assay results reflect genuine vaccine-induced responses rather than confounding background noise.
Figure 1. Total complement hemolytic titer is retained following antibody depletion, enabling its use as a source of exogenous complement in vaccine efficacy and immunogenicity testing.
Figure 2. A) The Pel-Freez immunoglobulin removal process does not remove other major serum fractions, such as serum albumin, alpha1 globulins, alpha2 globulins, and beta globulins from pooled human serum, as demonstrated by serum protein electrophoresis. B) Comparison of pre- and post-depletion preparations by SDS-PAGE demonstrates similar protein profiles with the exception of IgG and IgM, which have been removed.
Figure 3. Analysis of pre- and post-depletion human serum by mass spectrometry indicates minimal differences in levels of critical matrix proteins (n = 3, *p > 0.05, †p < 0.05 due to increased serum concentration following depletion and diafiltration).
Cited in studies spanning a broad range of pathogenic targets
Pel-Freez ADHC researchers across academia and the pharmaceutical industry have successfully integrated ADHC and antibody-depleted human serum (ADHS) into immunogenicity assays targeting a diverse array of bacterial and viral pathogens, including:
- Neisseria gonorrhoeae
- N. meningitidis
- Haemophilus influenzae
- Respiratory syncytial virus
- Staphylococcus aureus
- SARS-CoV-2
- Rickettsia
- Klebsiella pneumoniae
- Acinetobacter spp.
- Mycoplasma genitalium
The resulting citations in peer-reviewed studies demonstrate the versatility and robust applicability of our antibody-depleted human complement and serum reagents, reducing the need for assay-specific complement sourcing and simplifying lab workflows.
Figure 4. Distribution of literature citations by application since launch of ADHC and ADHS, n = 24.
Increasing adoption across leading research institutions and biopharma companies
User adoption of Pel-Freez ADHC/ADHS has steadily increased, with over 60 labs across 21 countries using it in just the first 5 years since launch. Leading pharmaceutical companies and research institutions, including Sanofi, UCSF, UMass Chan Medical School, and others, have incorporated ADHC/ADHS into their workflows for both routine assays and innovative vaccine programs.
Figure 5. Example customer application: Comparison of Pel-Freez ADHC and a qualified complement source prepared by a vaccine developer in hSBA using sera from 12 vaccinated individuals.
Why researchers rely on Pel-Freez antibody-depleted human complement:
- Significantly reduces background interference: Eliminating IgG and IgM provides clearer, more interpretable assay results.
- Consistent lot-to-lot reproducibility: Stringent QC protocols ensure assay reliability across studies.
- Flexible concentration options: Complement activity is tunable by adjusting ADHC concentration, accommodating various assay sensitivity needs.
- Scalable supply availability: Large-volume manufacturing supports seamless scale-up from preclinical to clinical trials.
Reliable immunogenicity testing starts with better reagents
Immunogenicity testing provides the foundation for critical vaccine-development decisions, making assay reliability non-negotiable. Pel-Freez antibody-depleted human complement removes a significant source of uncertainty—background antibody interference—giving researchers confidence in their results.
If your team prioritizes accuracy, consistency, and scalability in immunogenicity testing, Pel-Freez ADHC represents a straightforward upgrade to elevate your assay capabilities.
Contact us to request a sample or view our antibody-depleted human products to start optimizing your next immunogenicity assay.
