As communicated earlier, Eurocine Vaccines is conducting preclinical trials to evaluate the mRNA and protein technology platforms for its therapeutic Herpes simplex virus type 2, HSV-2, vaccine candidates. The initial results demonstrate that immune responses in mice immunized with the mRNA candidate are not only non-inferior to those elicited by their protein counterpart. In fact, the mRNA vaccine generates superior T cell responses.

Results from the study, comparing the two technology platforms at multiple doses, demonstrate that the mRNA and the protein vaccines were well tolerated and generated T cell and antibody responses. After the full immunization regimen, both vaccines induced exceptionally high anti-body titers at all doses tested. However, T cell responses are considered to be the best correlate to immunologic control of reactivation of HSV-2 and prevention of genital blisters and other sequelae. Importantly, mRNA vaccination stimulated potent T cell responses that significantly outcompeted those generated by the protein vaccine in performance in several specific areas.

Notably, the mRNA vaccine:

• Elicited superior numbers of IFN-γ, IL-2 and TNF-α secreting T-cells.
• Induced high frequencies of both CD4 and CD8 antigen-specific T cells. The CD8 T cell responses were vigorous consisting of up to 14% of the total CD8 T cells in the spleen.

Guineapigs are the most clinically relevant small animal model of HSV-2 infection, and in the next step of the evaluation process, guineapigs with an established HSV-2 infection will be vaccinated. The study is planned to start during spring 2023 and will be indicative for the final decision on which technology to pursue for the portfolio candidate against HSV-2.

“I am overwhelmed by these results” says Dr. Karl Ljungberg, Director of Preclinical Development at Eurocine Vaccines. “The T cell responses that we report here are in line with those that can be detected after recovery from an infection and are focused to a part of the HSV-2 virus that we believe is important to target to obtain immunologic control of the virus” continues Karl Ljungberg.

Note:

HSV-specific T cells are an important factor for immunologic control of HSV-2 infection. HSV-specific effector memory CD4 and CD8 T cells expressing IFN-γ and TNF-α are found in HSV-2 infected ganglia and correlate to fewer recurrencies.

Relevant news preceding this release;

“Eurocine Vaccines inleder första studien med sitt HSV-2 vaccin”, 13 October 2022 (Swedish)

“Eurocine Vaccines outlines a strategic development plan for its newly added therapeutic HSV-2 vaccine candidate”, 4 July 2022

This is an unofficial translation of the Swedish original. In the event of any discrepancies between the Swedish original and the English translation, the Swedish text shall apply.