High-titer manufacturing of SARS-CoV-2 Spike-pseudotyped VSV in stirred-tank bioreactors.

The severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) pandemic highlighted the importance of vaccine innovation in public health. Hundreds of vaccines built on numerous technology platforms have been rapidly developed against SARS-CoV-2 since 2020. Like all vaccine platforms, an important bottleneck to viral-vectored vaccine development is manufacturing. Here, we describe a scalable manufacturing protocol for replication-competent SARS-CoV-2 Spike-pseudotyped vesicular stomatitis virus (S-VSV)-vectored vaccines using Vero cells grown on microcarriers in a stirred-tank bioreactor. Using Cytodex 1 microcarriers over 6 days of fed-batch culture, Vero cells grew to a density of 3.95 ± 0.42 ×106 cells/mL in 1-L stirred-tank bioreactors. Ancestral strain S-VSV reached a peak titer of 2.05 ± 0.58 ×108 plaque-forming units (PFUs)/mL at 3 days postinfection. When compared to growth in plate-based cultures, this was a 29-fold increase in virus production, meaning a 1-L bioreactor produces the same amount of virus as 1,284 plates of 15 cm. In addition, the omicron BA.1 S-VSV reached a peak titer of 5.58 ± 0.35 × 106 PFU/mL. Quality control testing showed plate- and bioreactor-produced S-VSV had similar particle-to-PFU ratios and elicited comparable levels of neutralizing antibodies in immunized hamsters. This method should enhance preclinical and clinical development of pseudotyped VSV-vectored vaccines in future pandemics.

Author Correction: Smac mimetics and oncolytic viruses synergize in driving anticancer T-cell responses through complementary mechanisms.

The originally published version of this article contained an error in the spelling of the author Pankaj Tailor, which was incorrectly given as Pankaj Taylor. This has now been corrected in both the PDF and HTML versions of the article.

Smac mimetics and oncolytic viruses synergize in driving anticancer T-cell responses through complementary mechanisms.

Second mitochondrial activator of caspase (Smac)-mimetic compounds and oncolytic viruses were developed to kill cancer cells directly. However, Smac-mimetic compound and oncolytic virus therapies also modulate host immune responses in ways we hypothesized would complement one another in promoting anticancer T-cell immunity. We show that Smac-mimetic compound and oncolytic virus therapies synergize in driving CD8+ T-cell responses toward tumors through distinct activities. Smac-mimetic compound treatment with LCL161 reinvigorates exhausted CD8+ T cells within immunosuppressed tumors by targeting tumor-associated macrophages for M1-like polarization. Oncolytic virus treatment with vesicular stomatitis virus (VSVΔM51) promotes CD8+ T-cell accumulation within tumors and CD8+ T-cell activation within the tumor-draining lymph node. When combined, LCL161 and VSVΔM51 therapy engenders CD8+ T-cell-mediated tumor control in several aggressive mouse models of cancer. Smac-mimetic compound and oncolytic virus therapies are both in clinical development and their combination therapy represents a promising approach for promoting anticancer T-cell immunity.Oncolytic viruses (OV) and second mitochondrial activator of caspase (Smac)-mimetic compounds (SMC) synergistically kill cancer cells directly. Here, the authors show that SMC and OV therapies combination also synergize in vivo by promoting anticancer immunity through an increase in CD8+ T-cell response.