OR.6. Loss of SAP Expression in XLP Patient T CellsImpairs TCR-induced Apoptosis Independent ofEBV InfectionAndrew Snow,1 Rebecca Marsh,2 Philip Roehrs,2 Lisa Young,2

Jack van Hoff,3 Kejian Zhang,2 Alexandra Filipovich,2

Helen Su,1 Jack Bleesing,2 Michael Lenardo.1 1NationalInstitute of Allergy and Infectious Diseases, NIH, Bethesda,MD;

2Cincinnati Children's HospitalMedicalCenter, Cincinnati,

OH;3Yale University School of Medicine, New Haven, CT

X-linked lymphoproliferative disease (XLP) is a rareprimary immunodeficiency caused by mutations in the geneencoding signaling lymphocyte activation molecule (SLAM)-associated protein (SAP). Although XLP is frequently asso-ciated with fulminant Epstein Barr virus (EBV)-associatedinfectious mononucleosis/hemophagocytic lymphohistiocy-tosis (HLH), clinical manifestations also occur in the absenceof EBV infection. We recently studied four SAP-deficient,EBV-naÝve XLP patients who developed lymphoproliferativedisease associated with B cell lymphoma and/or Tcell drivenHLH-like disorders. Immunologic evaluation of these patientsrevealed known lymphocyte abnormalities inherent to XLP,as well as signs of hyperactive T cell responses linked toprevious infections. Strikingly, activated XLP patient T cellswere resistant to death induced by T cell receptor (TCR)restimulation, an important self-regulatory mechanism forcontrolling immune responses. Knockdown of SAP expressionin normal donor cells using RNA interference recapitulatedthis defect in both CD4+ and CD8+ T cells without alteringprimary T cell activation, suggesting SAP is critical for aspecific TCR-induced apoptotic signal. Other death pathwaystriggered through Fas ligation or IL-2 withdrawal remainedunaffected in the absence of SAP expression. In conclusion,our data suggests that defective T cell homeostasis, as-sociated with impaired TCR-induced apoptosis, contributesto lymphoproliferative disorders in XLP patients independentof EBV infection.

doi:10.1016/j.clim.2008.03.011

OR.7. Treatment of HIV-Infected Patients with GcProtein-derived Macrophage Activating Factor(GcMAF) Eradicates HIV-infectionNobuto Yamamoto,1 Kazuya Hashinaka,1 Masumi Ueda,1

Theodore Sery,1 Charles Benson.2 1Socrates Institute forTherapeutic Immunology, Philadelphia, PA;

2University of

Pennsylvania, Philadelphia, PA

Serum vitamin D-binding protein (known as Gc protein) isthe precursor for the principal macrophage activating factor(MAF). The MAF precursor activity of serum Gc protein ofHIV-infected patients was lost or reduced because Gcprotein is deglycosylated by serum α-N-acetylgalactosami-nidase (Nagalase) secreted from HIV-infected cells. SinceNagalase is the intrinsic component of gp120, serumNagalase was already complexed with anti-HIV immunoglo-bulin G (IgG) in patient blood stream. These antibodies werelargely not neutralizing antibodies. The IgG-bound viralproteins retained Nagalase activity that is required for

infectivity and also deglycosylates Gc protein, leading toimmunosuppression. Stepwise treatment of purified Gcprotein with immobilized β-galactosidase and sialidasegenerated the most potent MAF (termed GcMAF) everdiscovered, which produces no side effect in humans.Macrophages activated by intramuscular administration ofGcMAF (100 ng/patient) develop a large amount of Fc-receptors as well as enormous variation of receptors thatphagocytize IgG bound and unbound HIV virions. Cellslatently infected with HIV are unstable and spontaneouslyrelease the virions at a high rate. After less than 18 weeklyadministrations of 100 ng GcMAF to twenty-one nonanemicpatients, they exhibited low serum Nagalase activitiesequivalent to healthy controls, indicating eradication ofHIV-infection. Since GcMAF has a potent mitogenic activityon myeloid progenitor cells (MPC) and intravenous admin-istration of GcMAF allows rapid interaction of GcMAF withMPC in bone marrow, the systemic cell counts of theactivated macrophages increased to 200-fold. Weeklyintravenous administration of 100 ng GcMAF to HIV-infectedpatients eradicates HIV-infection in 8-12 weeks.

doi:10.1016/j.clim.2008.03.012

Shaping Immune Cell FunctionFriday, June 6

2:45 pm–4:45 pm

OR.8. Lack of High Affinity Competition DuringAntigen-specific Priming of Polyclonal T CellsUnmasks IL-4 ProductionJoshua Milner, William Paul. NIAID, Bethesda, MD

In TCR transgenic priming cultures, low concentrationsof antigen favor Th2 differentiation. This is presumed to bedue to low avidity TCR-MHC engagement during priming.We hypothesized that during physiologic polyclonalresponses, cells with higher affinity for antigen generallyfail to become Th2 cells and, by dominating the response,prevent low affinity cells from acquiring a Th2 phenotype.To examine this point, we utilized naïve 5CC7 Vβ3transgenic CD4 T-cells, which have normal, endogenous,polyclonal TCRα chain rearrangement. Cells were initiallysorted based on expression of CD5, a marker of avidity, andprimed with a high concentration of pigeon cytochrome Cpeptide (pPCC). Only the CD5lo cells were capable ofproducing IL-4 and only when cultured at low celldensities. Priming cell populations depleted of cells thatbind a pPCC tetramer efficiently resulted in IL-4 productioneven at higher T-cell density. Addition of fewer than 500tetramer-binding T-cells to this depleted cell populationinhibited priming for IL-4 production. Single cell cloninganalysis of both polyclonal 5CC7 Vβ3 and monoclonalVα11Vβ3 TCR transgenics using high peptide concentrationsshowed that while the very few clones emerging from therelatively high affinity αβ TCR transgenic T cell made IL-4,the vast majority of clones derived from polyclonal 5CC7Vβ3 transgenic donors made significant amounts, andappeared, on average, to have less CD69 upregulation in

S6 Abstracts