Poster presentation

Open Access

# P02-06. The adjuvancy of OX40 ligand (CD252) on an HIV-1 canarypox vaccine

J Liu*, N Ngai, GW Stone, F Yue and MA Ostrowski

Address: University of Toronto, Toronto, Canada

from AIDS Vaccine 2009

Paris, France. 19–22 October 2009

Published: 22 October 2009

Retrovirology 2009, 6(Suppl 3):P11 doi:10.1186/1742-4690-6-S3-P11

This abstract is available from: http://www.retrovirology.com/content/6/S3/P11

© 2009 Liu et al; licensee BioMed Central Ltd.

## Background

The immunogenicity of current human immunodeficiency virus-1 (HIV-1) canarypox vaccines is weak and needs to be improved. Ligation of OX40 (CD134), a member of tumor necrosis factor receptor superfamily (TNFRSF), by its ligand OX40L (CD252), a tumor necrosis factor superfamily (TNFSF) molecule, has been demonstrated to provide a pivotal costimulatory signal to enhance CD4 T cell help of humoral and cytotoxic T cell immune responses. The present study examined whether an OX40L expressing vector could boost the immunogenicity of the HIV-1 canarypox vaccine, vCP1452, in mice.

## Methods

Female Balb/c mice were vaccinated 3 times with 2-week intervals according to the following schedule: group 1: naive unimmunized mice; group 2: 10 pfu of vCP1452 + 10 pfu empty vector ALVAC II; group 3: 10 pfu of vCP1452 + 10 pfu vCPmOX40L; group 4: 10 pfu of vCP1452 + 5 × 10 pfu vCPmOX40L + 5 × 10 pfu vCPmCD40L. Six weeks after the last immunization, mice were sacrificed and spleens and sera were collected for immunological analysis, including IFN-γ ELISPOT, tetramer staining, ICS, CFSE proliferation assay, and anti-Gag ELISA.

## Results

Co-immunization of mice with OX40L-expressing canarypox and vCP1452 augmented HIV-1 specific CD8 T cell responses in terms of frequency and cytokine expression. OX40L-expressing canarypox enhanced the frequency of

antigen specific CD8 T cells with an effector (CD127 CD62L) phenotype, which was associated with an *ex vivo* expansion of HIV-1 specific CD4 T cells. Surprisingly, OX40L did not enhance antibody responses elicited by the HIV-1 canarypox vaccine. We saw no added benefit by combining OX40L and CD40L vectors as an adjuvant strategy for vCP1452.

## Conclusion

Our results indicate that, similar to CD40L, OX40L can enhance the cellular but not humoral immunogenicity of HIV-1 canarypox vaccines. In summary, our findings show that OX40L can be used as a molecular adjuvant to enhance T cell immune responses.

<footnote>* Corresponding author</footnote>