Prior exposure to an attenuated Listeria vaccine does not reduce immunogenicity: pre-clinical assessment of the efficacy of a Listeria vaccine in the induction of immune responses against HIV.
BACKGROUND
We have evaluated an attenuated Listeria monocytogenes (Lm) candidate vaccine vector in nonhuman primates using a delivery regimen relying solely on oral vaccination. We sought to determine the impact of prior Lm vector exposure on the development of new immune responses against HIV antigens.


RESULTS
Two groups of rhesus macaques one Lm naive, the other having documented prior Lm vector exposures, were evaluated in response to oral inoculations of the same vector expressing recombinant HIV-1 Gag protein. The efficacy of the Lm vector was determined by ELISA to assess the generation of anti-Listerial antibodies; cellular responses were measured by HIV-Gag specific ELISpot assay. Our results show that prior Lm exposures did not diminish the generation of de novo cellular responses against HIV, as compared to Listeria-naïve monkeys. Moreover, empty vector exposures did not elicit potent antibody responses, consistent with the intracellular nature of Lm.


CONCLUSIONS
The present study demonstrates in a pre-clinical vaccine model, that prior oral immunization with an empty Lm vector does not diminish immunogenicity to Lm-expressed HIV genes. This work underscores the need for the continued development of attenuated Lm as an orally deliverable vaccine.
Division of Viral Pathogenesis, Beth Israel Deaconess Medical Center, Boston, MA 02115, USA. jwhitne2@bidmc.harvard.edu.
James B
JB
Whitney
Saied
S
Mirshahidi
So-Yon
SY
Lim
Lauren
L
Goins
Chris C
CC
Ibegbu
Daniel C
DC
Anderson
Richard B
RB
Raybourne
Fred R
FR
Frankel
Judy
J
Lieberman
Ruth M
RM
Ruprecht
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