RESUMO
Updated and revised versions of COVID-19 vaccines are vital due to genetic variations of the SARS-CoV-2 spike antigen. Furthermore, vaccines that are safe, cost-effective, and logistic-friendly are critically needed for global equity, especially for middle- to low-income countries. Recombinant protein-based subunit vaccines against SARS-CoV-2 have been reported using the receptor-binding domain (RBD) and the prefusion spike trimers (S-2P). Recently, a new version of prefusion spike trimers, named HexaPro, has been shown to possess two RBD in the "up" conformation, due to its physical property, as opposed to just one exposed RBD found in S-2P. Importantly, this HexaPro spike antigen is more stable than S-2P, raising its feasibility for global logistics and supply chain. Here, we report that the spike protein HexaPro offers a promising candidate for the SARS-CoV-2 vaccine. Mice immunized by the recombinant HexaPro adjuvanted with aluminum hydroxide using a prime-boost regimen produced high-titer neutralizing antibodies for up to 56 days after initial immunization against live SARS-CoV-2 infection. Also, the level of neutralization activity is comparable to that of convalescence sera. Our results indicate that the HexaPro subunit vaccine confers neutralization activity in sera collected from mice receiving the prime-boost regimen.
RESUMO
BACKGROUND: Testicular germ cell tumors (TGCTs) are the most common malignant cancer in young men. Although TGCTs are generally responsive to platinum-based chemotherapy particularly cisplatin, acquired resistance in patients with metastasis still occurs resulting in poor prognosis. Specifically, differentiation of embryonal carcinoma (EC) cells, the stem cells of TGCTs, can lead to the reduction of cisplatin responsiveness. Therefore, novel therapeutic strategies for TGCTs are needed. System L amino acid transporters have been reported to be up-regulated and to play an important role in tumorigenesis. However, expression and role of system L amino acid transporters in TGCTs remain elusive. MATERIALS AND METHODS: Expression of system L amino acid transporters was analyzed in TGCT samples from The Cancer Genome Atlas (TCGA). Expression of LAT1, LAT2, and 4F2hc was examined in human embryonal carcinoma cell line NTERA2. Roles of system L amino acid transporters on NTERA2 cell survival, cell proliferation, pluripotency, and cisplatin sensitivity were evaluated. RESULTS: Based upon TCGA datasets, we found that two isoforms of system L (LAT1 and LAT2) and their chaperone protein 4F2hc are highly expressed in EC samples compared with other groups. Treatment with the system L inhibitor BCH significantly suppressed leucine uptake into the pluripotent EC cell line NTERA2. The malignant phenotypes including cell viability, cell proliferation, and clonal ability were decreased following BCH treatment. Nonetheless, system L inhibition did not alter expression of stemness genes in NTERA2 cells. After NTERA2 differentiation, expressions of LAT1 and LAT2 were decreased. Finally, co-administration of BCH enhanced cisplatin sensitivity in both undifferentiated and differentiated cells. These effects were associated with the reduction in p70S6K phosphorylation. CONCLUSION: Taken together, these results shed light on the roles of system L amino acid transporters in TGCTs. Therefore, system L amino acid transporters could provide novel therapeutic targets for treatment against TGCTs.
