CD8+ T cells are a subset of lymphocytes that play a major role in antiviral defense (Kulinski et al. 2013). However, recently published evidence shows reduced levels of circulating CD8+ T cells in people infected with SARS-CoV-2 (Zheng et al. 2020, Wang et al.  2020; HC= healthy controls, NCP = patients with COVID-19 related pneumonia):

Immune enhancing treatments, including thymalfasin and immunoglobulin are being provided to SARS-COV-2 infected subjects with some success. For example, 37/55 (67%) subjects saw improvements for circulating CD8+ levels in Wang et al. 2020, but additionally, 18/55 subjects did not experience increased CD8+ counts:

Accordingly, levels of CD8+ T cells were identified as an independent predictor for COVID-19 severity and treatment efficacy (Wang et al. 2020). When considering that CD8+ cells were not increased in all subjects in Wang et al., are there are other strategies that may be helpful? Interestingly, increased levels of CD8+ cells are found in the lungs of mice infected with the influenza A virus in response to a high soluble-fiber diet, when compared with control-fed mice (Trompette et al. 2018):

As a result, lung viral load is more than 10-times reduced 8-days after infection in high soluble fiber-fed mice:

Moreover, average survival in mice infected with influenza A is significantly better when fed the high soluble-fiber diet, when compared with control fed-mice:

Is it possible that a high soluble fiber diet can increase CD8+ cells in people infected with SARS-CoV-2, thereby enhancing their recovery and survival? No studies have tested this hypothesis (yet). While conventional medical treatment is obviously helpful, based on the findings of Trompette et al. (2018), further optimization of immune defense against viral infections may occur when including soluble fiber-rich foods.

References

Kulinski JM, Tarakanova VL, Verbsky J. Regulation of antiviral CD8 T-cell responses. Crit Rev Immunol. 2013;33(6):477-88. Review.

Trompette A, Gollwitzer ES, Pattaroni C, Lopez-Mejia IC, Riva E, Pernot J, Ubags N, Fajas L, Nicod LP, Marsland BJ. Dietary Fiber Confers Protection against Flu by Shaping Ly6c^– Patrolling Monocyte Hematopoiesis and CD8⁺ T Cell Metabolism. Immunity. 2018 May 15;48(5):992-1005.e8. doi: 10.1016/j.immuni.2018.04.022.

Wang F, Nie J, Wang H, Zhao Q, Xiong Y, Deng L, Song S, Ma Z, Mo P, Zhang Y. Characteristics of peripheral lymphocyte subset alteration in COVID-19 pneumonia. J Infect Dis. 2020 Mar 30. pii: jiaa150. doi: 10.1093/infdis/jiaa150.

Zheng M, Gao Y, Wang G, Song G, Liu S, Sun D, Xu Y, Tian Z. Functional exhaustion of antiviral lymphocytes in COVID-19 patients. Cell Mol Immunol. 2020 Mar 19. doi: 10.1038/s41423-020-0402-2.

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