Sindbis virus replicon particles encoding calreticulin linked to a tumor antigen generate long-term tumor-specific immunity

Abstract

Alphavirus vectors have emerged as a promising strategy for the development of cancer vaccines and gene therapy applications. In this study, we used the replication-defective vaccine vector SIN replicon particles from a new packaging cell line (PCL) to develop SIN replicon particles encoding calreticulin (CRT) linked to a model tumor antigen, human papillomavirus type 16 (HPV16) E7 protein. The linkage of CRT to E7 in SIN replicon particles resulted in a significant increase in E7-specific CD8 þ T-cell precursors and a strong antitumor effect against E7-expressing tumors in vaccinated mice. SINrep5-CRT/E7 replicon particles enhanced presentation of E7 through the major histocompatibility complex (MHC) class I pathway by infecting dendritic cells (DCs) directly and pulsing DCs with lysates of cells infected by SINrep5-CRT/E7 replicons. Vaccination of immunocompromised (BALB/c nu/nu) mice with SINrep5-CRT/E7 replicon particles also generated significant reduction of lung tumor nodules, suggesting that antiangiogenesis may contribute to the antitumor effect of SINrep5-CRT/E7 replicon particles. Furthermore, SINrep5-CRT/E7 replicon particles generated long-term in vivo tumor protection effects and antigen-specific memory immunities. We concluded that the CRT strategy used in the context of SIN replicon particles facilitated the generation of a highly effective vaccine for cancer prophylaxis and immunotherapy.

Alphavirus vectors as tools in neuroscience and gene therapy

“…Antigen-specific CTL responses enhanced anti-tumor activity at low IL-12 doses, but higher doses did neither improve the immune response nor tumor regression. Co-expression of HPV E7 and the endoplasmatic reticulum Ca2+ binding transporter calreticulin (CRT) from SIN particles was evaluated as a prophylactic vaccine (Cheng et al, 2006). Intramuscular immunization generated antigenspecific immune responses, an anti-angiogenic effect and strong anti-tumor activity.…”

Alphavirus-Based Vaccines

“…Moreover, strong in vivo anti-tumor activity was induced. In another study, SIN virus particles expressing both HPV E7 and calreticulin (CRT), an endoplasmic reticulum Ca 2+ binding transporter, were tested as prophylactic vaccines [88]. Vaccinations generated antigen-specific immune responses, an anti‑angiogenic effect and a strong anti-tumor activity.…”

Immunotherapy for Cervical Cancer

“…Their high infection efficiency and excellent expression of antigens encoded by the virus in the infected cells make them an appealing choice for the delivery of HPV antigens (for review, see (29)). Many live viral vectors have been used for therapeutic HPV vaccine development, including adenoviruses (30–32), adeno-associated viruses (33), fowlpox viruses (34), vaccinia viruses (35–41), vesicular stomatitis viruses (VSV) (42), and alphaviruses (such as the Semliki Forest virus (43–46), Venezuelan equine encephalitis (VEE) virus (47, 48), and Sindbis virus (49)). In the following sections, we will focus on adenovirus, vaccinia and alphavirus for further discussion of their applications in both preclinical models and clinical trials.…”