Comparison of humoral immune responses upon DNA and DNA&Protein co-immunization administered by IM injection.

<p>Macaques were immunized twice (V1, V2) at 0 and 2 months with SIV DNA only (N = 10) or co-immunized with DNA&Protein (N = 2) using SIV AT-2 particles as protein source. The DNA vaccine was administered by IM injection (needle/syringe). The protein was administered by subcutaneous and intramuscular injections into the same sites, immediately following the DNA injection. Endpoint bAb titers (in log) to SIVmac251 Env were measured. The endpoint values for the DNA only vaccinated animals were below the cut-off (1∶50) of the assay. Of note, the <i>env</i> DNA used in these animals <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091550#pone.0091550-Rosati2" target="_blank">[22]</a> was different than the improved expression-optimized <i>env</i> DNA used in the subsequent studies presented in this work. In addition, we used a less efficient DNA delivery method, which explains the lower immunogencity of this DNA-only vaccine.