A novel therapeutic vaccine composed of a rearranged human papillomavirus type 16 E6/E7 fusion protein and Fms-like tyrosine kinase-3 ligand induces CD8+ T cell responses and antitumor effect.

The development of cervical cancer is mainly caused by infection with high risk genotypes of human papillomavirus, particularly type 16 (HPV16), which accounts for more than 50% of cervical cancer. The two early viral oncogenes, E6 and E7, are continuously expressed in cervical cancer cells and are necessary to maintain the malignant cellular phenotype, thus providing ideal targets for immunotherapy of cervical cancer. In this study, a novel vaccine strategy was developed based on a rationally shuffled HPV16 E6/E7 fusion protein, the addition of Fms-like tyrosine kinase-3 ligand (Flt3L) or the N domain of calreticulin (NCRT), and the usage of a CpG adjuvant. Four recombinant proteins were constructed: m16E6E7 (mutant E6/E7 fusion protein), rm16E6E7 (rearranged mutant HPV16 E6/E7 fusion protein), Flt3L-RM16 (Flt3L fused to rm16E6E7), and NCRT-RM16 (NCRT fused to rm16E6E7). Our results suggest that Flt3L-RM16 was the most potent of these proteins in terms of inducing E6- and E7-specific CD8+ T cell responses. Additionally, Flt3L-RM16 significantly induced regression of established E6/E7-expressing TC-1 tumors. Higher doses of Flt3L-RM16 trended toward higher levels of antitumor activity, but these differences did not reach statistical significance. In summary, this study found that Flt3L-RM16 fusion protein is a promising therapeutic vaccine for immunotherapy of HPV16-associated cervical cancer.

Arabidopsis FIMBRIN5, an actin bundling factor, is required for pollen germination and pollen tube growth.

Actin cables in pollen tubes serve as molecular tracks for cytoplasmic streaming and organelle movement and are formed by actin bundling factors like villins and fimbrins. However, the precise mechanisms by which actin cables are generated and maintained remain largely unknown. Fimbrins comprise a family of five members in Arabidopsis thaliana. Here, we characterized a fimbrin isoform, Arabidopsis FIMBRIN5 (FIM5). Our results show that FIM5 is required for the organization of actin cytoskeleton in pollen grains and pollen tubes, and FIM5 loss-of-function associates with a delay of pollen germination and inhibition of pollen tube growth. FIM5 decorates actin filaments throughout pollen grains and tubes. Actin filaments become redistributed in fim5 pollen grains and disorganized in fim5 pollen tubes. Specifically, actin cables protrude into the extreme tips, and their longitudinal arrangement is disrupted in the shank of fim5 pollen tubes. Consequently, the pattern and velocity of cytoplasmic streaming were altered in fim5 pollen tubes. Additionally, loss of FIM5 function rendered pollen germination and tube growth hypersensitive to the actin-depolymerizing drug latrunculin B. In vitro biochemical analyses indicated that FIM5 exhibits actin bundling activity and stabilizes actin filaments. Thus, we propose that FIM5 regulates actin dynamics and organization during pollen germination and tube growth via stabilizing actin filaments and organizing them into higher-order structures.