Science Spotlight

Targeting HIV vaccines to dendritic cells boosts the immune response

From the Vaccine and Infectious Disease Division

Currently, HIV-1 infection can be controlled by antivirals, however there is still no cure. Vaccine efforts focus on inducing a strong long-lived immune response made up of both HIV antibodies and cytotoxic T cell responses. In an effort to increase vaccine efficiency, research groups have started to directly target immune cells important for initiating and regulating the cells’ response. In a collaborative study, researchers at Fred Hutch in the Vaccine and Infectious Disease Division worked to further their earlier findings with a replicating Vaccinia virus vector (NYVAC-KC) by linking the vector prime with a dendritic cell (DC) targeting boost. To do this, the team created two different targets; the first is an anti-human LOX-1 antibody fused to HIV envelope (ENV) gp140, and the second is an anti-human CD40 antibody conjugated to the ENV gp140. The LOX-1 construct specifically targets LOX-1 on antigen-presenting cells (APCs) favoring a humoral response. The CD40 construct targets CD40 on APCs, which is a TNF family receptor that is broadly expressed on APCs and should elicit cytotoxic T cell responses as well as T cell dependent humoral responses. In this study, the group looked at the individual DC targeting components alone, with NYVAC-KC and with or without poly ICLC adjuvant.

Table 1: Vaccine groups and vaccination schedule.

Group week 0 week 4 week 12 week 24

In order to test the different vaccine regimens, non-human primates were divided into five groups as shown in table 1. After vaccination, sera were collected at various time points to test the antibody response. Overall, the IgG titers were highest after the last boost and waned 8 weeks later. With regard to CD40 and poly ICLC, there seemed to be a benefit to administering the CD40 construct with poly ICLC.  IgA levels seemed to be lower after the NYVAC-KC vaccination but were boosted with the DC- targeting constructs, with the highest increase in the 4th vaccine regimen group. Looking closer at antibody magnitude and breadth, all groups developed cross-clade, multi-epitope antibodies, with groups 2 and 4 having the highest magnitude of binding. Neutralization activity was measured showing neutralization of sensitive viruses only, and decreased between week 26 and 32. Groups 3 and 4 had the highest overall magnitude and breadth of neutralization for each time point measured. Antibody dependent cell-mediated cytotoxicity assays showed positive results for all groups at week 14 and 26 but only group 2 and 4 had positivity at week 32.

To evaluate the antigen-specific T cell response, IFN-gamma was measured with samples that became positive after DC-targeted boosts. The LOX-1 response was similar with or without vector prime, however the CD40 group produced more IFN with vector prime and poly ICLC. To look at antigen-specific CD4 T cell responses, intracellular cytokine staining was analyzed. In this assay the investigators found low levels in the vector prime and high quality responses after DC boost. Similar results were seen for antigen specific CD8 T cell responses, with highest quality responses measured in the group two and no change with or without poly ICLC. Durability of antibody response was also measured. Overall, CD40 showed better durability compared with LOX-1 and group 4 had the best antibody and neutralizing durability. In conclusion, targeting of APCs by CD40 with poly ICLC (group4) produced the best antibody response and T cell responses including best durability. The response in group 4 produced robust, cross clade, multi-epitope reactive antibodies. Specifically, NYVAC-KC co-administration with DC-targeting boosts did not improve the magnitude of humoral responses but did generate high quality antigen- specific CD8 T cells. The poly ICLC adjuvant improved the humoral response in the CD40 groups, which showed better magnitude, breadth, durability and CD8 T cell responses compared to LOX-1 targeting.

Funding for this work was provided by the Bill & Melinda Gates Foundation and the Vaccine Research Institute HIV vaccine program.

Zurawski G,Shen X,Zurawski S,Tomaras GD,Montefiori DC,Roederer M,Ferrari G,Lacabaratz C,Klucar P,Wang Z,Foulds KE,Kao SF,Yu X,Sato A,Yates NL,LaBranche C,Stanfield-Oakley S,Kibler K,Jacobs B,Salazar A,Self S,Fulp J,Gottardo R,Galmin L,Weiss D,Cristillo A,Pantaleo G,Levy Y. 2017. Superiority in Rhesus Macaques of Targeting HIV-1 Env Gp140 to CD40 Versus LOX-1 in Combination with Replication Competent NYVAC-KC for Induction of Env-Specific Antibody and T Cell Responses. J Virol. pii: JVI.01596-16. doi: 10.1128/JVI.01596-16.