Innate Functions of Immunoglobulin M Lessen Liver Gene Transfer with Helper-Dependent Adenovirus

Abstract

The immune system poses obstacles to viral vectors, even in the first administration to preimmunized hosts. We have observed that the livers of B cell-deficient mice were more effectively transduced by a helper-dependent adenovirus serotype-5 (HDA) vector than those of WT mice. This effect was T-cell independent as shown in athymic mice. Passive transfer of the serum from adenovirus-naïve WT to Rag1KO mice resulted in a reduction in gene transfer that was traced to IgM purified from serum of adenovirus-naïve mice. To ascribe the gene transfer inhibition activity to either adenoviral antigen-specific or antigen-unspecific functions of IgM, we used a monoclonal IgM antibody of unrelated specificity. Both the polyclonal and the irrelevant monoclonal IgM inhibited gene transfer by the HDA vector to either cultured hepatocellular carcinoma cells or to the liver of mice in vivo. Adsorption of polyclonal or monoclonal IgMs to viral capsids was revealed by ELISAs on adenovirus-coated plates. These observations indicate the existence of an inborn IgM mechanism deployed against a prevalent virus to reduce early post-infection viremia. In conclusion, innate IgM binding to adenovirus serotype-5 capsids restrains gene-transfer and offers a mechanism to be targeted for optimization of vector dosage in gene therapy with HDA vectors.

Impact of Natural IgM Concentration on Gene Therapy with Adenovirus Type 5 Vectors

“…Natural IgM does not directly neutralize Ad5 in vitro (8), but natural IgM nevertheless inhibits liver transduction by Ad5 vectors in vivo (9,10). KCs are a major sink for Ad5 vectors (11)(12)(13)(14)(15).…”

“…Although the presence of natural antibodies clearly inhibits Ad5 liver transduction (9,10), the impact of natural antibody concentrations is unclear. To examine ;CD19 cre/ϩ mice have a B cell-specific deletion in the Shp1 tyrosine phosphatase which causes expansion of B-1a cells and elevated IgM (24).…”

“…Error bars represent SD. Transferring natural IgM to antibody-deficient mice decreases Ad5 liver transduction, while transfer of natural IgG has no effect (9,10). Recently, Unzu et al (10) found that liver transduction was suppressed by transfer of a monoclonal IgM antibody against the human AE2 anion exchanger, suggesting that IgM may nonspecifically suppress liver transduction by Ad5.…”

“…Transferring natural IgM to antibody-deficient mice decreases Ad5 liver transduction, while transfer of natural IgG has no effect (9,10). Recently, Unzu et al (10) found that liver transduction was suppressed by transfer of a monoclonal IgM antibody against the human AE2 anion exchanger, suggesting that IgM may nonspecifically suppress liver transduction by Ad5. However, the monoclonal antibody used by Unzu et al also exhibited strong binding with Ad5 (10), suggesting that their antibody was actually a polyreactive monoclonal antibody with reactivity to both the AE2 anion exchanger and Ad5.…”

Interaction of adenovirus with antibodies, complement, and coagulation factors

“…Instead, natural IgM can enhance the clearance of AdV by liver macrophages known as Kupffer cells (KCs) , which reduces the amount of virions available to transduce hepatocytes. IgM‐deficient mice show increased hepatocyte transduction by AdV‐5 vectors when compared with wild‐type mice . Moreover, the concentration of IgM in different strains of mice inversely correlates with the ability of intravenously administered AdV vectors to transduce hepatocytes.…”