Recombinant vaccinia virus expression of Anaplasma marginale surface protein MSP-1a: effect of promoters, leader sequences and GPI anchor sequence on antibody response.

Anaplasma marginale surface protein MSP-1a was expressed by recombinant vaccinia viruses with different promoters and as hybrid proteins. Transcription of msp1 alpha with P11 late promoter resulted in more MSP-1a than with P7.5 early-late promoter; however, mice immunized with the recombinants had similar antibody titres. Recombinants expressing hybrid MSP-1a with either a murine leukaemia virus or a trypanosomal glycoprotein signal sequence did not enhance antibody responses and resulted in a diffuse intracellular distribution of MSP-1a which did not accumulate in the Golgi apparatus as was noted in the absence of these signal sequences. In contrast, antibody titres to MSP-1a in mice immunized with a recombinant virus expressing hybrid MSP-1a with a trypanosomal GPI anchor signal sequence were significantly increased over all other constructs.