P14-15 LB. The safety and immunogenicity of HIV-1 vaccines based on DNA and replication competent vaccinia vector in phase I clinical trial

Improved safety of a replication-competent poxvirus-based HIV vaccine with the introduction of the HSV-TK/GCV suicide gene system

INTRODUCTION

Replication-competent vaccinia viruses (VACVs) show prolonged antigen expression time and greater stimulation of immune responses than their replication-incompetent counterparts. However, there is the potential risk of serious post-vaccination complications, especially for children and immunocompromised individuals, leading to safety concerns about the reintroduction of VACV as a vaccine vector. In this study, we improved the safety of the vaccinia virus TianTan (VACV-TT) based HIV vaccine by introducing the HSV-TK/GCV suicide gene system, which is composed of the herpes simplex virus type 1 thymidine kinase gene (HSV-tk) and the antiviral drug ganciclovir (GCV).

MATERIALS AND METHODS

By inserting the HSV-tk gene into the replication-competent VACV-TT genome, a new vector, TT-TK (VACV-TT expressing the HSV-tk gene), and a candidate vaccine, TT-EnvTK (TT-TK expressing the HIV-1 env gene), were constructed.

RESULTS

The new vector TT-TK exhibited reduced replication capacity both in vitro and in vivo in the presence of GCV. GCV inhibited the replication of TT-TK in the brains of mice and skin of rabbits, and provided 100% protection in mice against lethal challenge with TT-TK at a dose of 80mg/kg/day. Furthermore, the candidate vaccine TT-EnvTK induced cellular and humoral immunity against HIV-1 antigen that was comparable to the immunity induced by VTKgpe (VACV-TT expressing HIV-1 env, gag, and pol genes).

DISCUSSION

These promising results suggest a new strategy to mitigate the potential risk of post-vaccination complications from replication-competent VACV-based HIV vaccines.

Scientific Approaches to AIDS Prevention and Control in China

The HIV epidemic in China started among intravenous drug users in the late 1980s. The second wave of the epidemic was caused by an outbreak in the paid plasma donors in central China in the mid-1990s. Sexually transmitted HIV cases have steadily increased and comprised more than half the reported HIV/AIDS infections since 2007. In the last 5 years, there has been a sharp increase of HIV infection in men who have sex with men. The HIV epidemic in China has expanded from high-risk groups to the general population and from rural regions to urban areas. This brief article discusses the history of HIV epidemics in China and the challenges facing the current AIDS control efforts in the country. It explains that only scientific approaches can sustain the national AIDS control programs and introduce the type of research needed to address those challenges. The selected research areas include molecular epidemiology, drug resistance surveillance, and the Chinese HIV vaccine research.

AIDS vaccine for Asia Network (AVAN): expanding the regional role in developing HIV vaccines

The HIV/AIDS pandemic continues to spread and an AIDS vaccine is urgently needed. Regional alliances and international collaborations can foster the development and evaluation of the next generation of AIDS vaccine candidates. The importance of coordinating and harmonizing efforts across regional alliances has become abundantly clear. We recently formed the AIDS Vaccine for Asia Network (AVAN) to help facilitate the development of a regional AIDS vaccine strategy that accelerates research and development of an AIDS vaccine through government advocacy, improved coordination, and harmonization of research; develops clinical trial and manufacturing capacity; supports ethical and regulatory frameworks; and ensures community participation.