Allogeneic transplantation (allo-HCT) has led to the cure of HIV in one individual, raising the question of whether transplantation can eradicate the HIV reservoir. To test this, we here present a model of allo-HCT in SHIV-infected, cART-suppressed nonhuman primates. We infect rhesus macaques with SHIV-1157ipd3N4, suppress them with cART, then transplant them using MHC-haploidentical allogeneic donors during continuous cART. Transplant results in ~100% myeloid donor chimerism, and up to 100% T-cell chimerism. Between 9 and 47 days post-transplant, terminal analysis shows that while cell-associated SHIV DNA levels are reduced in the blood and in lymphoid organs post-transplant, the SHIV reservoir persists in multiple organs, including the brain. Sorting of donor-vs.-recipient cells reveals that this reservoir resides in recipient cells. Moreover, tetramer analysis indicates a lack of virus-specific donor immunity post-transplant during continuous cART. These results suggest that early post-transplant, allo-HCT is insufficient for recipient reservoir eradication despite high-level donor chimerism and GVHD.

BackgroundIn humans it has been reported that a major site of the latent reservoir of HIV is within CD4+ T cells expressing the memory marker CD45RO, defined by the mAb UCHL1. There are conflicting reports regarding the expression of this antigen in macaques, the most relevant animal species for studying HIV pathogenesis and testing new therapies. There is now a major effort to eradicate HIV reservoirs and cure the infection. One approach is to eliminate subsets of cells housing the latent reservoir, using UCHL1 to target these cells. So that such studies may be performed in macaques, it is essential to determine expression of CD45RO.MethodsWe have used immunofluorescence and flow cytometry to study cell surface expression of CD45RO on lymphocytes from PBMC, lymphoid, and GI organs of rhesus, pigtailed, and cynomolgus macaques. Both direct and indirect immunofluorescence experiments were performed.FindingsCD45RO is expressed on a subset of CD4+ lymphocytes of all pigtailed, a fraction of rhesus, and neither of the cynomolgus macaques studied. The binding of UCHL1 to macaque cells was of lower avidity than to human cells. This could be overcome by forming UCHL1 multimers. Directly conjugating fluors to UCHL1 can inhibit UCHL1 binding to macaque cells. Patterns of UCHL1 expression differ somewhat in macaques and humans, and from that of other memory markers often used in macaques.ConclusionsCD45RO, defined with mAb UCHL1, is well expressed on CD4+ cells in pigtailed macaques. Using tissues recovered from latently infected pigtailed macaques we are determining whether UCHL1, or other memory markers, can define the cellular locus of the reservoir. The low avidity of this interaction could limit the utility of UCHL1, in its conventional form, to eliminate cells in vivo and test this approach in macaque models of HIV infection.

Nonhuman primate models of human AIDS have been used successfully to evaluate candidate vaccines and infection intervention therapies. Successes of pathogenicity studies in primate models have been limited because of the varied infection outcomes and characteristic low number of study animals. The acutely pathogenic HIV-2(287)--Macaca nemestrina model has shown promise both in antiviral drug evaluation and in pathogenicity studies. Here we describe virus replication, spread, and host responses during the first 28 days of HIV-2(287) infection. Focusing on 18 macaques from a larger 27-macaque study, we report changing virus loads, CD4(+) cell depletions, and antibody responses both systemically and in the mucosa of the small intestine. After intravenous inoculation, blood and intestinal tissue were collected from pairs of macaques at 12 hr and 1, 2, 4, 6, 10, 14, 21, and 28 days postinfection. Specimens were examined for evidence of infection by quantitative cultures, in situ hybridization, lymphocyte subset monitoring, and antibody production. The data were presented serially as though all samples were collected from a single macaque. The highest blood virus loads were detected between days 10 and 14 and subsequently decreased through day 28. This coincided with a significant increase in ileum mucosa virus loads on day 10, which became undetectable by day 28. The lowest levels of CD4(+) cells were observed on days 21 and 28 in blood and ileum mucosa. CD4(+):CD8(+) cell ratios in blood and ileum dropped dramatically after day 10 to lowest levels by day 28. Intestinal virus loads were inversely correlated with CD4(+) cell and virus-specific antibody levels in the ileum after day 6. These results underscore the suitability of this model for pathogenicity studies as well as the importance of the intestinal lymphoid tissues as an initial site of virus replication and cell destruction during the acute, asymptomatic stage of AIDS development.

Background : The Berlin patient is thus far the only individual considered cured of HIV. Three aspects of the Berlin Patient's treatment are thought to have contributed to his cure following allogeneic hematopoietic stem cell transplantation (HCT): 1) the myeloablative conditioning regimen, 2) transplantation with HIV-resistant cells, and 3) graft-versus-host disease (GVHD). This cure occurred in the context of HCT from an unrelated donor whose cells contained two copies of the CCR5delta32 mutation, which rendered them resistant to CCR5-tropic viruses (the vast majority of the transmitted variants). He also developed GVHD, which is thought to have contributed to his cure by inducing a graft-versus-viral-reservoir (GVVR) effect. While it is still unknown which of these factors was critical to the cure achieved in this patient, the viral rebound observed following allogeneic transplantation with wild-type cells in two Boston patients suggests that HIV-resistance factors may be key to achieving a permanent HIV cure through HCT. Our lab has previously shown that transplantation with autologous unmodified hematopoietic stem cells is not sufficient to eradicate the viral reservoir in a non-human primate (NHP) model of infection. However, the relative contributions of myeloablative conditioning, GVVR, and HIV resistant cells to the clearance of the HIV reservoir have not been rigorously determined. To dissect the impact of each of these factors on the viral reservoir, we have developed the first NHP model of allogeneic bone marrow transplantation (BMT) in Simian/Human Immunodeficiency Virus (SHIV)-infected, combined antiretroviral therapy (cART)-treated rhesus macaques. Methods : We intravenously infected 6 animals with SHIV-1157ipd3N4 and left them untreated for six months, followed by six months of cART (PMPA, FTC, Raltegravir). 3 animals served as untransplanted controls, and 3 animals received haplo-identical BMT following myeloablative total body irradiation (1020 Gy) without cART discontinuation. Donor chimerism was monitored by molecular analysis and by flow cytometry. Plasma viral RNA was measured by RT-PCR, and cell-associated DNA and RNA were quantified by qPCR in 6 tissues longitudinally, and in >20 tissues at necropsy. Results : All animals showed peak SHIV plasma viral loads (1.5e7 copies/ml) 10-11 days post-infection, subsequently reaching viral set points. 1 of 6 animal controlled viremia before cART initiation. In all other animals, plasma viral RNA became undetectable 2-3 weeks post cART initiation. We euthanized the transplant recipients at day 47, 29, and 9 post-transplant, due to infection, graft-versus host disease, and renal complications, respectively. Analysis of whole blood and gated CD4+ T cells showed acquisition of 100% donor blood chimerism at day 29, with lower T cell chimerism in 1 animal. Despite undetectable SHIV plasma viremia post-transplant, the cell-associated SHIV DNA reservoir persisted in multiple tissues, including lymphoid, hematopoietic and major organs, gut and CNS, and was even increased in certain tissues of transplanted animals compared to untransplanted controls. Conclusions : Our results indicate that the DNA reservoir persists and may even increase early after transplantion, despite control of peripheral viremia. Thus, allogeneic HCT is likely associated with an initial loss of anti-HIV immunity leading to an increase in the size of the viral reservoir. This may also explain the rebound observed in the Boston patients. Thus, we propose that reservoir eradication will require additional HIV resistance factors and/or anti-HIV strategies post-transplant to enhance 1) donor cell resistance, and 2) the targeted killing of infected cells. Disclosures Kiem: Rocket Pharmaceuticals: Consultancy, Equity Ownership, Patents & Royalties, Research Funding. Kean: Regeneron: Research Funding; Bristol Myers Squibb: Consultancy; Juno: Research Funding; Kymab Ltd: Research Funding.