The use of directed evolution to create a stable and immunogenic recombinant BCG expressing a modified HIV-1 Gag antigen.

Numerous features make Mycobacterium bovis BCG an attractive vaccine vector for HIV. It has a good safety profile, it elicits long-lasting cellular immune responses and in addition manufacturing costs are affordable. Despite these advantages it is often difficult to express viral antigens in BCG, which results in genetic instability and low immunogenicity.

Oral vaccination with a recombinant Salmonella vaccine vector provokes systemic HIV-1 subtype C Gag-specific CD4+ Th1 and Th2 cell immune responses in mice.

Background: Recombinant Salmonella vaccine vectors may potentially be used to induce specific CD4+ T cell responses against foreign viral antigens. Such immune responses are required features of vaccines against pathogens such as human immunodeficiency virus type 1 (HIV-1). The aim of this study was to investigate the induction of systemic HIV-1-specific CD4+ T helper (Th) responses in mice after oral immunization with a live attenuated Salmonella vaccine vector that expressed HIV-1 subtype C Gag.

A prime-boost immunisation regimen using recombinant BCG and Pr55(gag) virus-like particle vaccines based on HIV type 1 subtype C successfully elicits Gag-specific responses in baboons.

Mycobacterium bovis BCG is considered an attractive live bacterial vaccine vector. In this study, we investigated the immune response of baboons to a primary vaccination with recombinant BCG (rBCG) constructs expressing the gag gene from a South African HIV-1 subtype C isolate, and a boost with HIV-1 subtype C Pr55(gag) virus-like particles (Gag VLPs). Using an interferon enzyme-linked immunospot assay, we show that although these rBCG induced only a weak or an undetectable HIV-1 Gag-specific response on their own, they efficiently primed for a Gag VLP boost, which strengthened and broadened the immune responses.

An oral recombinant Salmonella enterica serovar Typhimurium mutant elicits systemic antigen-specific CD8+ T cell cytokine responses in mice.

Background: The induction of antigen-specific CD8+ T cell cytokine responses against an attenuated, oral recombinant Salmonella enterica serovar Typhimurium vaccine expressing a green fluorescent protein (GFP) model antigen was investigated. A GFP expression plasmid was constructed in which the gfp gene was fused in-frame with the 5' domain of the Escherichia coli beta-galactosidase alpha-gene fragment with expression under the lac promoter. Groups of mice were orally immunized three times with the bacteria and systemic CD8+ T cell cytokine responses were evaluated.

Creation and characterisation of a high-copy-number version of the pAL5000 mycobacterial replicon.

The majority of mycobacterial plasmid vectors are derived from the pAL5000 replicon and maintained at approximately five copies per cell. We have devised a method that directly selects for high-copy-number plasmids. This involves enriching for high copy number plasmids by repeatedly isolating and retransforming plasmids from a mutant library.