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Moderna-induced super-IgG4 in Macaques
A look at some mRNA-IgG4'ified macaques challenged with Omicron infection, with ambiguous results
Summary (click to expand):
Reader and researcher Jim H, who alerted me to the first IgG4 study last July, contributed excellent comments to Tuesday’s IgG4 dangers paper review. First, by pointing out that he had already proposed the IgG4 “pan-cancer” risk (due to IgG4 flippy-binding to random IgG1 antibodies (“Fc-Fc binding”)), in a post which I had read and regrettably forgotten before hitting send on Tuesday. Here is that:
Second, by highlighting a new study happening to look at IgG4 in macaques injected with a primary series of two Moderna Covid vaccines, with the astonishing finding that IgG4 comes to dominate all anti-spike IgG after a third dose with either Moderna or a switch to Novavax:
There is only one reaction appropriate here…
The study design is encapsulated in the following graphic, with my annotations:
The authors set their monkeys up with a normal primary course of the human Moderna Covid vaccine, and 17 weeks after the first dose, boost with either a 3rd dose of Moderna or a Novavax for the original spike or the Omicron BA.1 spike. Another 13 weeks later, they challenge the monkeys with infection with BA.5 Omicron. To repeat for emphasis, all monkeys start off with double-Moderna injection, so this is still mostly a story about mRNA and IgG4.
Results: Sky-high IgG4 (No, that’s not normal for macaques)
It’s not a design that seems to reflect any clear vision, and it results in unanswered questions galore. Judging from the supplemental materials, there doesn’t seem to be any evaluation of IgG subtypes for the week 17 draw, only weeks 6 and 19. This makes it impossible to parse how much of the surge in IgG4 found two weeks after the boosters is truly due to the third injection, rather than slow conversion after week 6 as suggested by Irrgang, et al. (the original IgG4 study in humans).
The Novavax-boosted monkeys wind up having roughly the same levels of IgG4, but since IgG1 is lower, their overall response is far more IgG4-dominant than the Moderna boosted. Here is an incredible graphic I made visually representing overall anti-spike antibodies and percentages as a “table”:
It’s notable, here, that IgG4 is already a bit high at week 6. More to the point, we can see that IgG4 is higher in absolute terms in the Moderna-boosted, but is not so remarkably dwarfing IgG1 in that group. Whereas in the Novavax-boosted, IgG1 is almost entirely “faded out” for some of the monkeys.
My best guess is that the Novavax-receiving monkeys happened to already be more IgG4-dominant before the booster, and the Novavax booster is prompting less of a surge in antibody vs. the Moderna booster, and all of this detail is obscured by the failure to measure and report IgG subtypes in the week 17 draw.
The alternate possibility is that the Novavax booster is somehow driving a rapid, higher conversion to IgG4 despite prompting less of a boost in overall IgG antibodies, which does not seem plausible, as the conversion to IgG4 should be driven by overall presence of antigen. A third possibility is that Novavax, by directly introducing all spike at the same instant rapidly induces B Cells to convert to IgG4 via overstimulation, with less of an evident surge in overall antibodies because the antigen is rapidly cleared or masked by the same antibodies; whereas, the Moderna booster may be exerting more of a “slow burn” effect that keeps antibodies higher on week 19 due to continued production of spike, but effects a slower induction of IgG4 conversion.
None of these are likely very relevant: We know mRNA vaccines induce IgG4 conversion by some means, but they did not “invent” IgG4 conversion via prolonged and repeated antigen-stimulation, and there is nothing particularly surprising about the finding that (maybe) a subunit vaccine like Novavax can enhance IgG4 after an mRNA primer. However, I find my first proposal the most plausible.
Importantly, high IgG4 is not some weird “macaque thing”
To confirm that such dramatic conversions to IgG4 are not normal, I searched for previous studies that might report IgG subtypes in macaques. A paper by Siddiqui, et al. explored antibody responses after macaques were naturally infected with SARS-CoV-2, and found that anti-spike IgG4 is predictably rare after infection, including several weeks afterward:
Absolute and relative increase in IgG1 are higher than IgG4 between weeks 2 and 7 after infection, such that the ratio of IgG1 to IgG4 goes from a range of 1 to 14 to a range of 4 to 20 in individual donors, with an average of 16.5 (whereas, after the first two Moderna injections in the new paper, it is only 6 at week 6).
Challenge infection with BA.5: Only a slight suggestion of an IgG4 detriment
13 weeks after the 3rd dose, our IgG4-ified macaques are challenged with infection with BA.5 (none of them having been given a vaccine for that version of the spike protein in advance), and compared with un-vaccinated controls. Does IgG4 cause infection enhancement?
Our expectations here should be calibrated by a few points:
Natural infection with SARS-CoV-2 is not very pathogenic for macaques. There is minimal weight-loss, only brief temperature elevation, and mild lung pathology at necropsy.
Another study has already evaluated infection outcomes after triple-injecting macaques with the Moderna vaccine, and did not find any infection enhancement.
Point 2 is particularly important, because even though that previous study did not report IgG subtypes, presumably a similar amount of IgG4 was generated by the Moderna vaccine, because… it’s the same vaccine. If the results in this new study were not generalizable, we wouldn’t be interested in them. This previous study is a preprint from last year which readers may already have seen, Gagne, M. et al.It is “that macaque Covid vaccine study you read about last year,” unless that phrase has no meaning to you.
Both Gagne, et al. and the new study find that Moderna-vaccinated monkeys outperform unvaccinated controls in suppressing PCR-measured viral replication almost completely. However, when animals are sacrificed, and using a similar scoring system as the new study, Gagne, et al. report perfect suppression of viral antigen, yet less than complete reduction of inflammation, but no enhancement:
The new paper’s mRNA-1273 x 3 group only differs in terms of the schedule of events after the primary course (and naturally the other two groups differ by being boosted with Novavax), notably with 13 weeks between the third dose and infection in the new study vs. 4 in Gagne, et al., and this seems to effect a turn for the worse in terms of lung inflammation at necropsy. These poor results, by the way, are not even presented in the main text in visual form, but relegated to the supplemental materials:
Again, however, it should be emphasized that no infections were severe. When overlaying the average inflammation score with the authors’ example images for each animal, it seems clear that the “enhancement” observed for the triple-Moderna group is trivial, if not imaginary:
These macaques might therefore be modeling Omicron infection outcomes in a naturally resistant human group, i.e. children. Extreme IgG4 conversion doesn’t appear to interfere with suppression of viral replication, and doesn’t seem to lead to any remarkable enhancement of inflammation in the lungs. But, this might not be generalizable to older humans navigating infection with future variants with mRNA-induced tolerance.
Additionally, this offers nothing in the way of long-term outcomes, and obviously cannot highlight rare IgG4 infection-related harms (e.g. organ damage or long-term complaints) given such a small number of animals.
There are other remarks one could make about the study, including the dramatic ablation of FcgRIIIA activation reported on week 19, suggesting that IgG4 conversion has begun to disable antibody-activated Natural Killer cell recruitment in response to spike (although all the cellular cytotoxicity results are steady). However, I found no obvious relationship between low FcgRIIIA scores on week 19 and high lung pathogenicity scores (likewise for IgG1 and IgG4 levels).Overall, my goal with this review, after having kicked the tires on Routhu, et al. as much as I could, is simply to report that nothing obviously alarming was found (beyond what we already knew about mRNA-induced IgG4).
Routhu, et al. confirms mRNA Covid vaccine-induced IgG4 conversion in an animal model, and offers a preview of SARS-CoV-2 infection outcomes given extremely high levels of IgG4 — with no obvious detriment revealed.
If you derived value from this post, please drop a few coins in your fact-barista’s tip jar.
Routhu, NK. et al. “Efficacy of mRNA-1273 and Novavax ancestral or BA.1 spike booster vaccines against SARS-CoV-2 BA.5 infection in non-human primates.” Sci Immunol. 2023 May 16;eadg7015
Siddiqui, SM. et al. “2022 Serological Markers of SARS-CoV-2 Reinfection.” mBio. 2022 Jan-Feb; 13(1): e02141-21.
Data shown is from supplemental file.
Munster, VJ. et al. “Respiratory disease in rhesus macaques inoculated with SARS-CoV-2.” Nature. 2020 Sep;585(7824):268-272.
Again from supplemental data: