CROI 2018 Abstract eBook

Abstract eBook

Oral Abstracts

ordinary cDC obtained from healthy donors. Notably, circulating Mo from Neut2 neutralizers were de-enriched for the inflammatory CD16+ subset (p=0.002), but differentially transcribed genes involved in IL-12 production (p=0.034) compared to Non Neuts. Finally, B cells from Neut2 patients differentially transcribed genes involved in BCR signaling (p= 0.003) and Ig-class switching (p= 0.004) and were more enriched in memory IgD- IgM+ B cells (p<0.0001) compared to Non Neuts. Conclusion: cDC function is associated with distinct Mo and B cells phenotypical patterns in a subgroup of controllers that develop neutralizing Ab breadth. IL-12 represents a promising adjuvant for vaccine-mediated induction of Tfh responses and bNAb. 16LB INTERDOMAIN STABILIZATION IMPAIRS CD4 BINDING AND IMPROVES IMMUNOGENICITY OF SOSIPS Peng Zhang 1 , Jason Gorman 1 , Hui Geng 1 , Yin Lin 1 , Yaroslavl Tsybovsky 2 , Huiyi Miao 1 , Qingbo Liu 1 , Tsion Andine 1 , Alice Kwon 1 , Ferzan Uddin 1 , Mit Patel 1 , Christina Guzzo 1 , John R. Mascola 1 , Peter D. Kwong 1 , Paolo Lusso 1 1 NIH, Bethesda, MD, USA, 2 NIH, Frederick, MD, USA Background: The remarkable structural flexibility of the HIV-1 envelope (Env) and the susceptibility to antigenic remodeling upon CD4 binding represent key obstacles to the development of a protective vaccine. Here, we fixed the HIV-1 Env in pre-fusion configuration with impaired CD4-binding capacity via structure-guided introduction of a neo-disulfide bond bridging the outer and inner domains of gp120. This design was successfully applied to both soluble trimers and native full-length gp160 from diverse HIV-1 strains. Interdomain- locked trimers displayed increased thermal stability, restricted antigenic profile with enhanced binding to trimer-preferring broadly neutralizing antibodies (bNAbs) and lack of recognition by non-neutralizing antibodies. Crystallization of a locked BG505 SOSIP.664 trimer provided a structural basis for the loss of CD4 interaction. In rabbit immunization studies, stabilized trimers elicited the production of neutralizing antibodies against tier-2 autologous viruses with intact glycan shields, irrespective of complexing with a CD4 mimic. Methods: Mutagenesis, Protein Expression and Purification Negative-staining Electron Microscopy Crystal Structure Expression of Full-length HIV-1 gp160 Flow Cytometry Surface Plasmon Resonance Analysis Rabbit Immunization Pseudovirus Preparation, Infectivity and Neutralization Assays Results: We stabilized the HIV-1 Env trimer in native pre-fusion configuration using a novel structure-guided strategy bridging two cardinal structural elements, the inner and outer domains, of the gp120 glycoprotein. We designed and characterized interdomain-locked trimers that are selectively and efficiently targeted by potent bNAbs, are poorly, if at all, recognized by weakly- and non-neutralizing antibodies, and are unable to physiologically interact with human CD4. Stabilized trimers derived from two different HIV-1 strains showed improved immunogenicity in rabbits, eliciting the production of potent neutralizing antibodies against tier-2 autologous viruses with intact glycan shield independently of pre-complexing with a CD4-mimetic miniprotein. Conclusion: The present study provides a new strategy to stabilize the HIV-1 Env trimer and thereby reduce access to epitopes for non-neutralizing antibodies and abrogate CD4 binding. The lack of CD4 binding ensures that Env- based immunogens would not undergo unwanted antigenic modifications or be lost by CD4+ T-cell sequestration after injection into human vaccines.

Oral Abstracts

17 EQUAL DISTRIBUTION OF SIV DNA IN MEMORY T HELPER CELL SUBSETS OF RHESUS MACAQUES Stephen Lai 1 , Joseph Mudd 2 , Jason Brenchley 1 1 NIAID, Bethesda, MD, USA, 2 NIAID, Baltimore, MD, USA Background: Interleukin-17 (IL-17) producing T helper cells (Th) are critical to maintaining gut barrier integrity and host response against extracellular bacterial and fungal infections. During the course of Simian Immunodeficiency Virus (SIV) infection, Th17 cells that express C-C chemokine receptor 6 (CCR6) are rapidly and preferentially depleted frommucosal tissues. It has been proposed that CCR6+ Th17 cells are more permissive to SIV, and are thus, preferentially infected. Methods: Lymphocytes from Peripheral Blood Mononuclear Cells (PBMC), spleen, and Mesenteric Lymph Nodes (MLN) of SIV+, viremic rhesus macaques were isolated and simulated for 6 hours with PMA and ionomycin in the presence of Brefeldin A. CD28+memory CD4 T cells were studied and CCR6+/ IL-17+ and IL-17- CD4 T cells (Th17 cells), CCR4-/IFNg+ and IFNg- CD4 T cells (Th1 cells), CCR4+/IFNg-/IL-17- CD4 T cells (Th2 cells) and FoxP3+ CD4 T cells (Tregs) were then flow cytometrically isolated, and the proportions of cells harboring SIV DNA were then assessed through qPCR. Results: Viral DNA was detected in all subsets of memory CD4 T cells (irrespective of functionality, phenotype, or anatomic location). However, irrespective of anatomic site studied, we found that no one population of isolated memory, CD28+, CD4 T cells harbored more (or less) viral DNA than any other population of memory CD4 T cells. Conclusion: Loss of CD4 T cells is a hallmark of progressive HIV/SIV infection and several studies have shown that Th17 cells are preferentially loss from mucosal tissues and lymph nodes that drain mucosal tissues. From our data it is unlikely that preferential loss of Th17 cells is attributed to preferential infection by the virus, itself.

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CROI 2018