FOLR1-induced folate deficiency reduces viral replication via modulating APOBEC3 family expression

Folate supports IL-25-induced tuft cell expansion following enteroviral infections

Intestinal tuft cells, a kind of epithelial immune cells, rapidly expand in response to pathogenic infections, which is associated with infection-induced interleukin 25 (IL-25) upregulation. However, the metabolic mechanism of IL-25-induced tuft cell expansion is largely unknown. Folate metabolism provides essential purine and methyl substrates for cell proliferation and differentiation. Thus, we aim to investigate the roles of folate metabolism playing in IL-25-induced tuft cell expansion by enteroviral infection and recombinant murine IL-25 (rmIL-25) protein-stimulated mouse models. At present, enteroviruses, such as EV71, CVA16, CVB3, and CVB4, upregulated IL-25 expression and induced tuft cell expansion in the intestinal tissues of mice. However, EV71 did not induce intestinal tuft cell expansion in IL-25-/- mice. Interestingly, compared to the mock group, folate was enriched in the intestinal tissues of both the EV71-infected group and the rmIL-25 protein-stimulated group. Moreover, folate metabolism supported IL-25-induced tuft cell expansion since both folate-depletion and anti-folate MTX-treated mice had a disrupted tuft cell expansion in response to rmIL-25 protein stimulation. In summary, our data suggested that folate metabolism supported intestinal tuft cell expansion in response to enterovirus-induced IL-25 expression, which provided a new insight into the mechanisms of tuft cell expansion from the perspective of folate metabolism.

Pralatrexate inhibited the replication of varicella zoster virus and vesicular stomatitis virus: An old dog with new tricks

Varicella zoster virus (VZV) is associated with herpes zoster (HZ) or herpes zoster ophthalmicus (HZO). All antiviral agents currently licensed for the management of VZV replication via modulating different mechanisms, and the resistance is on the rise. There is a need to develop new antiviral agents with distinct mechanisms of action and adequate safety profiles. Pralatrexate (PDX) is a fourth-generation anti-folate agent with an inhibitory activity on folate (FA) metabolism and has been used as an anti-tumor drug. We observed that PDX possessed potent inhibitory activity against VZV infection. In this study, we reported the antiviral effects and the underlying mechanism of PDX against VZV infection. The results showed that PDX not only inhibited VZV replication in vitro and in mice corneal tissues but also reduced the inflammatory response and apoptosis induced by viral infection. Furthermore, PDX treatment showed a similar anti-VSV inhibitory effect in both in vitro and in vivo models. Mechanistically, PDX inhibited viral replication by interrupting the substrate supply for de novo purine and thymidine synthesis. In conclusion, this study discovered the potent antiviral activity of PDX with a novel mechanism and presented a new strategy for VZV treatment that targets a cellular metabolic mechanism essential for viral replication. The present study provided a new insight into the development of broad-spectrum antiviral agents.

Regulatory variants of APOBEC3 genes potentially associate with COVID-19 severity in populations with African ancestry

Since November 2019, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused the worldwide pandemic of the coronavirus disease 2019 (COVID-19), the impact of which is huge to the lives of world populations. Many studies suggested that such situation will continue due to the endless mutations in SARS-CoV-2 genome that result in complexity of the efforts for the control of SARS-CoV-2, since the special enrichment of nucleotide substitution C>U in SARS-CoV-2 sequences were discovered mainly due to the editing by human host factors APOBEC3 genes. The observation of SARS-CoV-2 variants Beta (B.1.351) and Omicron (B.1.1.529) firstly spreading in South Africa promoted us to hypothesize that genetic variants of APOBEC3 special in African populations may be attributed to the higher mutation rate of SARS-CoV-2 variants in Africa. Current study was conducted to search for functional variants of APOBEC3 genes associate with COVID-19 hospitalization in African population. By integrating data from the 1000 Genomes Project, Genotype-Tissue Expression (GTEx), and Host Genetics Initiative (HGI) of COVID-19, we identified potential functional SNPs close to APOBEC3 genes that are associated with COVID-19 hospitalization in African but not with other populations. Our study provides new insights on the potential contribution of APOBEC3 genes on the evolution of SARS-CoV-2 mutations in African population, but further replication is needed to confirm our results.