P03-02. SCID-hu mice generate HIV specific human immune responses after gp96 vaccination

NOD.SCID common gamma chain (NSG) knockout mice have no functional adaptive immune system of their own and readily accept human CD34+ hematopoietic stem cell xenografts (SCID-hu). These SCID-hu represent a unique opportunity to study human adaptive immunological responses in a small rodent animal model. We have previously developed a cell based vaccine system utilizing a secreted form of heat shock protein gp96 along with HIV gag protein (293-gp96Ig-HIVgag).

Day 1 neonatal NSG mice were sub lethally irradiated and transplanted with 10⁶ human CD34+ hematopoietic stem cells intrahepatically. The pups were fostered, allowed to engraft and weened at 28 days. SCID-hu mice were vaccinated i.p. with 106 293-gp96Ig-HIVgag cells or 293 cells on days 0, 14 and 28. On day 33 the mice were sacrificed, spleen and peritoneal cavity cells (PEC) were harvested. 2 × 10⁵ cells were plated in triplicate, stimulated for 20 hours with 20 μg/ml of SLYNVATL, HIV gag peptide, for an IFN-γ ELISPOT assay.

Flow cytometry analysis of peripheral blood in pre-vaccination animals revealed human engraftment (mCD45 vs. hCD45) ranging from 4%–7%. Post vaccination analysis of the spleen indicated human engraftment ranging from 16–20%, PECs from SCID-hu after gp96 vaccination were primarily of human origin (90%–95%). SCID-hu vaccinated with 293-gp96Ig-HIVgag i.p. generated an HIV specific immune response. 293-gp96Ig-HIVgag vaccination generated an average of 778 spots per 2 × 10⁵ cells plated whereas mice vaccinated with 293 cells alone generated an average of 88.5 spots per 2 × 10⁵ cells plated (p < 0.05).

We conclude that SCID-hu mice are able to mount a human HIV-specific immune response after gp96 vaccination. Given the high cost of nonhuman primate models SCID-hu further represent an innovative way to study human immunological responses in a small animal model.