Both humoral and cellular immune responses are critical for the control of HIV infection and replication. We have established systems for production of HIV and SIV virus-like particles containing high levels of viral Env proteins using the baculovirus expression system. Evaluation of immunogenicity showed that immunization with virus-like particles induced both cellular and neutralizing antibody responses. Furthermore, mucosal administration of virus-like particles effectively induced both mucosal and systemic immune responses. These results indicate that virus-like particles consisting of HIV structural proteins are an attractive vaccine platform for eliciting anti-viral immune responses, especially neutralizing antibody responses. We have also synthesized codon-optimized genes for HIV Env proteins and evaluated their immunogenicity. Combinations of virus-like particle and DNA-based vaccination are promising for inducing strong cellular and neutralizing antibody responses against HIV.