Trusted biological materials for every stage of vaccine development
Fuel critical immunogenicity tests, functional assays, and preclinical research with reagents from a large-scale producer of antibody-depleted human complement and baby rabbit complement. From early discovery to regulatory submission, Pel-Freez delivers quality and consistency you can count on.
Key applications we support
Opsonophagocytic assays (OPA/OPKA)
Opsonophagocytic assays are the functional readout for Streptococcus pneumoniae vaccine and serology studies, and Pel-Freez baby rabbit complement is the complement source in published pneumococcal OPAs (Ahn et al., 2015; Ahmad et al., 2024). The same OPA format with Pel-Freez complement is published for Group A Streptococcus, Group B Streptococcus, and Staphylococcus aureus.
Bulk volumes and lot-locked supply maintain consistency across studies and sites.
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Serum bactericidal assays (SBA)
Serum bactericidal assays rely on active complement to assess vaccine-induced protection against pathogens such as N. meningitidis, N. gonorrhea, and Shigella spp. Pel-Freez is a leading supplier of bulk complement-preserved human and animal sera, supporting reliable and reproducible measurement of functional antibody responses during vaccine R&D.
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Viral neutralization tests
Pel-Freez provides high-quality human and animal sera for viral neutralization assays, including plaque reduction neutralization tests (PRNT), microneutralization, and pseudovirus-based formats.
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Bulk supply & consistency you can count on
From lot-locked supply to cold chain logistics, we make sure your reagents arrive ready to perform.
- Bulk volumes and custom purification
- U.S.-based production and traceability
- Consistent quality for long-term studies
- 40,000 sq.ft. ISO 9001-certified manufacturing space
It all began with rabbits
Beginning in 1911 as a backyard rabbit farm, Pel-Freez now serves the global research community as a large-scale producer of U.S.-sourced rabbit tissues and blood products, including baby rabbit complement.
With the largest USDA-inspected rabbit facility in the country, we control every step from sourcing to QC to deliver consistent, quality biological reagents to vaccine developers and labs worldwide.
Results start with the right materials
Start your next project with the products and support trusted by scientific teams around the world.
What researchers say about Pel-Freez
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“For over a decade Pel-Freez Biologicals has been a consistent supplier of high-quality reagents and an excellent partner.”
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“The IgG/IgM-depleted human complement batch worked great in our hands, so we went straight back to Pel-Freez for a single-lot follow-on volume.”
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“We screened Pel-Freez human complement lots for our program and were very happy with the results. Screening succeeded and we moved forward with a specific lot, with additional vials held for our manufacturing partner.”
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“We screened several baby rabbit complement lots and were pleased with the preliminary results of lot 30745*. Being able to hold reserve bottles of the lots that work has been essential before we scale up.”
Should I use human, rabbit, or guinea pig complement for my application?
Work backwards from the readout. Complement regulators are host-specific, so the complement source is part of the assay method, not a preference.
- Antibody-depleted human complement for the hSBA (serogroup B meningococcus and gonococcus; correlate hSBA ≥ 1:4). Neisseria recruits human factor H, which rabbit and guinea pig factor H cannot replace, and the donor antibodies in native human serum would kill the target on their own.
- Baby rabbit complement for the rSBA (serogroups A, C, W and Y; correlate rSBA ≥ 1:8) and for pneumococcal OPA/MOPA, which was standardized on it.
- Adult rabbit complement for complement-dependent cytotoxicity and HLA crossmatching, the classical cell-lysis source.
- Guinea pig complement where potency per volume is the point: CH50 titration, complement fixation and the vibriocidal assay.
When the model animal's own cascade is the readout, use matched-species complement. Mouse, rat, pig, canine, cynomolgus, goat and hamster complement are available on request through our custom quote form.
For what the research literature actually uses, by pathogen and assay, see which complement source for which assay.