Contamination of DNase Preparations Confounds Analysis of the Role of DNA in Alum-Adjuvanted Vaccines

Abstract

Aluminum salt (alum) adjuvants have been used for many years as adjuvants for human vaccines because they are safe and effective. In spite of its widespread use, the means by which alum acts as an adjuvant remains poorly understood. Recently, it was shown that injected alum is rapidly coated with host chromatin within mice. Experiments suggested that the host DNA in the coating chromatin contributed to alum’s adjuvant activity. Some of the experiments used commercially purchased DNase and showed that co-injection of these DNase preparations with alum and antigen reduced the host’s immune response to the vaccine. Here we report that some commercial DNase preparations are contaminated with proteases. These proteases are responsible for most of the ability of DNase preparations to inhibit alum’s adjuvant activity. Nevertheless, DNase somewhat reduces responses to some antigens with alum. The effect of DNase is independent of its ability to cleave DNA, suggesting that alum improves CD4 responses to antigen via a pathway other than host DNA sensing.

Host DNA released by NETosis promotes rhinovirus-induced type-2 allergic asthma exacerbation

“…When injected in the absence of virus infection, dsDNA from splenocytes recapitulated many but not all of the exacerbating effects of RV on asthma-related outcomes in mice, suggesting that more complex structures containing dsDNA, rather than dsDNA alone, were responsible for the full aggravating effects. This assumption was concordant with the fact that the commercially available DNase that we used degrades not only dsDNA but also DNA-associated proteins19,30–33. We therefore postulated that NETs, which contain both dsDNA and proteins/peptides, were the main source of airway dsDNA elicited by RV infection.…”

Old and new adjuvants

“…It is difficult to evaluate the contributions of NETs since it is difficult to eliminate them entirely from injected alum. As for the accompanying chromatin, a couple of papers have suggested that host DNA may indeed increase alum’s effects but host DNA is certainly not the only intrinsic adjuvant induced by alum ([29–31] but see [32]). Alum may also act simply as a particle, lysing lysosome and releasing lysosomal enzymes into the cytoplasm [33–35] or by distorting the plasma membrane of antigen presenting cells [36] and/or somehow by its ability to rapidly induce production if cytokines and chemokines [37,38].…”

The Syk–NFAT–IL-2 Pathway in Dendritic Cells Is Required for Optimal Sterile Immunity Elicited by Alum Adjuvants

“…Some studies suggested that the release of dsDNA from damaged and dying host cells, which is induced by alum injection, may contribute to priming of Th2 CD4 + T cells (4,5) and enhance MHC class II-mediated Ag presentation, prolonging CD4 + T cell interactions with DCs (5). However, a recent report by Noges et al (6) showed that some of the DNase preparations used in the above studies are contaminated by proteases, casting doubt on the significance of dsDNA in responses to alum.…”