Cytoplasmic Tail Truncation of SARS-CoV-2 Spike Protein Enhances Titer of Pseudotyped Vectors but Masks the Effect of the D614G Mutation.

The high pathogenicity of SARS-CoV-2 requires it to be handled under biosafety level 3 conditions. Consequently, Spike protein-pseudotyped vectors are a useful tool to study viral entry and its inhibition, with retroviral, lentiviral (LV), and vesicular stomatitis virus (VSV) vectors the most commonly used systems. Methods to increase the titer of such vectors commonly include concentration by ultracentrifugation and truncation of the Spike protein cytoplasmic tail. However, limited studies have examined whether such a modification also impacts the protein's function. Here, we optimized concentration methods for SARS-CoV-2 Spike-pseudotyped VSV vectors, finding that tangential flow filtration produced vectors with more consistent titers than ultracentrifugation. We also examined the impact of Spike tail truncation on transduction of various cell types and sensitivity to convalescent serum neutralization. We found that tail truncation increased Spike incorporation into both LV and VSV vectors and resulted in enhanced titers but had no impact on sensitivity to convalescent serum. In addition, we analyzed the effect of the D614G mutation, which became a dominant SARS-CoV-2 variant early in the pandemic. Our studies revealed that, similar to the tail truncation, D614G independently increases Spike incorporation and vector titers, but this effect is masked by also including the cytoplasmic tail truncation. Therefore, the use of full-length Spike protein, combined with tangential flow filtration, is recommended as a method to generate high titer pseudotyped vectors that retain native Spike protein functions. IMPORTANCE Pseudotyped viral vectors are useful tools to study the properties of viral fusion proteins, especially those from highly pathogenic viruses. The Spike protein of SARS-CoV-2 has been investigated using pseudotyped lentiviral and VSV vector systems, where truncation of its cytoplasmic tail is commonly used to enhance Spike incorporation into vectors and to increase the titers of the resulting vectors. However, our studies have shown that such effects can also mask the phenotype of the D614G mutation in the ectodomain of the protein, which was a dominant variant arising early in the COVID-19 pandemic. To better ensure the authenticity of Spike protein phenotypes when using pseudotyped vectors, we recommend using full-length Spike proteins, combined with tangential flow filtration methods of concentration if higher-titer vectors are required.

Hands-Only Cardiopulmonary Resuscitation Education: A Comparison of On-Screen With Compression Feedback, Classroom, and Video Education.

STUDY OBJECTIVE: We compare 3 methods of hands-only cardiopulmonary resuscitation (CPR) education, using performance scores. A paucity of research exists on the comparative effectiveness of different types of hands-only CPR education. This study also includes a novel kiosk approach that has not previously been studied, to our knowledge. METHODS: A randomized, controlled study compared participant scores on 4 hands-only CPR outcome measures after education with a 25- to 45-minute practice-while-watching classroom session (classroom), 4-minute on-screen feedback and practice session (kiosk), and 1-minute video viewing (video only). Participants took a 30-second compression test after initial training and again after 3 months. RESULTS: After the initial education session, the video-only group had a lower total score (compressions correct on hand placement, rate, and depth) (-9.7; 95% confidence interval [CI] -16.5 to -3.0) than the classroom group. There were no significant differences on total score between classroom and kiosk participants. Additional outcome scores help explain which components negatively affect total score for each education method. The video-only group had lower compression depth scores (-9.9; 95% CI -14.0 to -5.7) than the classroom group. The kiosk group outperformed the classroom group on hand position score (4.9; 95% CI 1.3 to 8.6) but scored lower on compression depth score (-5.6; 95% CI -9.5 to -1.8). The change in 4 outcome variables was not significantly different across education type at 3-month follow-up. CONCLUSION: Participants exposed to the kiosk session and those exposed to classroom education performed hands-only CPR similarly, and both groups showed skill performance superior to that of participants watching only a video. With regular retraining to prevent skills decay, the efficient and free hands-only CPR training kiosk has the potential to increase bystander intervention and improve survival from out-of-hospital cardiac arrest.

Glypican 3 as a Serum Marker for Hepatoblastoma.

Hepatoblastoma (HB) is the most common primary liver cancer in children. The conventional serum marker for HB, alpha-fetoprotein (AFP), has its limitations. Novel serum markers need to be explored. Glypican 3 (GPC3) has been reported to be an excellent histological immunomarker for HB. However, the clinical value of serum GPC3 in patients with HB is unknown. A total of 184 serum samples were tested for both GPC3 by ELISA, and AFP by immunometric assay. Of these, 134 were from 32 patients with HB at three treatment stages, 30 from age-matched patients with benign hepatobiliary disorders (BHD) and 20 from age-matched "normal controls"(NC). We found that the GPC3 levels in HB pretreatment group were significantly higher than those in NC group and HB remission group but not statistically different from those in BHD group and HB during treatment group. In contrast, AFP showed significant differences among different groups. The areas under the receiver operating curve (AUROC) value, sensitivity and specificity of GPC3 for HB pretreatment group versus all controls were all significantly lower than those of AFP. Serum GPC3 levels were not associated with prognostic parameters. We concluded that GPC3 is inferior to AFP as a serum marker for HB.