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Microbes & Immunity Carotene and immunity to COVID-19 vaccine

reported a significantly higher IgG response than the high the enrichment of the Ruminococcaceae family and the
Vitamin A-supplemented group (250,000 IU/kg diet). 30 reduction of the Mucispirillum genus compared to the
The proliferation rate of splenocytes in response to an vaccinated control group. The Ruminococcaceae family
37
antigen represents the spleen’s multiplication rate in response is a prominent butyrate producer. The Mucispirillum
to the antigenic stimulus. This serves as an indicator of genus, primarily represented by Mucispirillum
vaccine response, immune activation, and T-cell and B-cell schaedleri, is a mucus-resident intestinal bacterium in
rodents and is considered a pathobiont, a commensal
responses. In this study, the splenocytes from vaccinated organism that may contribute to disease. This indicates
38
mice fed with carotene showed a higher proliferation rate the potential of carotene supplementation to inhibit
(p<0.05) than those from vaccinated mice fed with the harmful bacteria in the gut. The findings from this
vehicle, suggesting that carotene supplementation can study revealed that carotene supplements significantly
modulate the host immune system. A similar result was decreased the abundance of SCFA producers (e.g.,
reported in a study on astaxanthin, a type of carotenoid, Odoribacter) and pectin-degrading bacteria in
in BALB/c mice, where lipopolysaccharide (LPS)-induced the feces of unvaccinated mice. In contrast, in the
lymphocyte proliferation was significantly increased by carotene-supplemented vaccinated group, there was an
astaxanthin administration. 31
increase in the abundance of butyrate producers (e.g.,
Interferon‐gamma is a pro-inflammatory cytokine Ruminococcaceae) and a decrease in the abundance of
produced by activated Th1 cells, CTLs, and NK cells. potential pathobionts (e.g., Mucispirillum) in the host
32
This cytokine is pivotal in stimulating and modulating gut microbiome. The Ruminococcaceae and Odoribacter
cell-mediated immune responses and class-switching enriched by carotene supplementation were reported
antibodies to the IgG class. Therefore, IFN‐γ is a to have a strong association with the metabolism and
7,31
key biomarker to evaluate cellular immune response, absorption of β-carotene. 39
where it is primarily produced by Th1 cells. In this In this study, the GC-MS analysis revealed that
33
study, the differences in the levels of IFN‐γ produced by carotene supplementation did not significantly modulate
antigen-stimulated splenocytes across all groups were SCFA (e.g., acetic acid, butyric acid, and propionic acid)
not statistically significant (p>0.05), indicating that the levels in the fecal samples. This result is in contrast
supplementation of carotene did not affect the production to recent research that deployed an in vitro anaerobic
of IFN‐γ regardless of the status of vaccination. However, fermentation model to study gut microbiome interaction
both the vaccinated control and carotene groups displayed with β-carotene, where β-carotene significantly
elevated levels of IFN‐γ compared to their unvaccinated increased the production of acetic acid and propionic
counterparts, indicating the activation of T lymphocytes acid compared to the control group. The discrepancy
10
by the inactivated virus vaccine. In contrast to the present in findings can be due to the difference in the research
result, cultured splenocytes from BALB/c mice fed with models, where quantification of SCFAs was affected
β-carotene and immunized with ovalbumin were reported by absorption of SCFAs in the colon but not in the in
to produce higher IFN‐γ and show increased IFN‐γ mRNA vitro model. Besides, this animal study was challenged
34
expression compared to the control group. In another by vaccination. The immunological challenge can cause
study, supplementation of astaxanthin, a carotenoid, to an inflammatory reaction associated with gut dysbiosis,
BALB/c mice showed significantly higher IFN-γ production potentially inhibiting SCFA producers. This finding was
in response to LPS or concanavalin A. The results of supported by a recent study where COVID-19 patients
31
the present study suggest that daily supplementation of reported significantly reduced SCFA levels. 19
carotene after vaccination can increase SARS-CoV-2-
specific humoral responses by promoting the proliferation 5. Conclusion
of lymphocytes.
This study used the BALB/c mice model to explore
In the present study, daily carotene supplementation the interaction of carotene supplementation with an
in unvaccinated BALB/c mice was observed to have inactivated SARS-CoV-2 virus vaccine. To evaluate the
reduced Odoribacter and Monoglobus in the gut association between carotene and vaccine response,
microbiome compared to unvaccinated controls. this study investigated the effect of carotene on immune
Odoribacter is a member of the SCFA producers in parameters, gut microbiome, and SCFA levels. Carotene
a healthy, balanced gut microbiota. Monoglobus is supplementation did not significantly affect the antibody
35
primarily represented by Monoglobus pectinilyticus, a gut levels related to the inactivated SARS-CoV-2 vaccine,
bacterium that breaks down pectin. On the other hand, IFN-γ levels, and fecal SCFA levels. However, it increases
36
carotene supplementation in vaccinated mice caused the proliferation rate of splenocytes in vaccinated mice.

Volume 2 Issue 3 (2025) 82 doi: 10.36922/MI025110021