Inducing broadly neutralizing antibodies (bnAb) is a central challenge in HIV vaccine development. The HIV envelope (Env) fusion peptide (FP) is a highly conserved bnAb epitope, yet is inefficiently targeted by antibodies elicited by experimental vaccines. Here, we test how Env trimer design and dosing strategies shape the magnitude and specificity of antibody responses by pairing FP priming with boosts using native-like Env trimers. Escalating-dose (ED) immunization regimens are a recently described approach to deliver antigens over a prolonged period, resulting in sustained increased antigen stability in the lymph node and germinal-center activity, improved immune kinetics, and enhanced recruitment and selection of targeted B-cell populations. The impact of ED regimens on boosting HIV-1 FP-specific responses has not been explored.
Here, guinea pigs (n = 5 per group) were primed with FP-rTTHC followed by boosts with prefusion trimers from clade A (BG505), clade C (ConC), or a Triple-Tandem-Trimer (three trimeric units of ConC, linked one after another: ConC-DS-14ln-TTT), delivered either as bolus injections or ED regimens.
All strategies elicited strong Env-specific responses, but the quality of these responses varied among immunogen designs. Bolus boosts using BG505 or ConC generated the most robust FP-specific recall responses, but neutralization levels ultimately converged across regimens. However, the TTT trimer expanded reactivity to non-FP epitopes, suggesting broader epitope engagement during boosting. Notably, cross-reactive BG505-binding antibodies appeared as early as week 6 after two FP primes, highlighting rapid activation of FP-targeting B cells.
These findings clarify how trimer architecture and dosing influence the trajectory of epitope targeting, strengthening the case for FP priming as a powerful method for engaging a vulnerable HIV Env epitope and demonstrating that the TTT platform may serve as an effective boost to epitopes beyond FP.
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Vaccines and Immunotherapy (VAC)
Shreyanshu Ray, Cheng Cheng, K. McKee et al.· Journal of Immunology· 0 citations
For rapidly mutating viruses such as influenza viruses and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), immune memory recalled by antigenically drifted variants primarily comprises antibodies that cross-react to the priming strain rather than de novo elicited responses, a phenomenon termed original antigenic sin or immune imprinting. The composition and functionality of de novo responses elicited by variant exposures remain unclear. Here we isolated and characterized hundreds of recall and de novo neutralizing monoclonal antibodies after sequential exposures to SARS-CoV-2 variants in ancestral-imprinted humans. De novo variant type-specific antibodies used different V(D)J genes that were closer to germline sequence, potently neutralized future variants and targeted distinct receptor binding domain epitopes compared to ancestral cross-reactive (recall) antibodies. Nevertheless, neutralizing responses to the updated 2024–2025 booster were predominantly ancestral cross-reactive. These results reveal the distinct contributions of recall and de novo antibodies to a balanced immune response and underscore the benefit of updated booster vaccines, which augment both subsets. Updated SARS-CoV-2 boosters broaden humoral immunity by recalling cross-reactive antibodies and eliciting new less cross-reactive Omicron type-specific antibodies that target distinct RBD epitopes and more potently neutralize recent variants.
T. Johnston, S. Li, M. Painter et al.· Nature Immunology· 2 citations
Assembly of flaviviruses such as Zika virus (ZIKV), dengue virus, and West Nile virus in the host cell endoplasmic reticulum is driven by the structural envelope (E) and premembrane (prM) proteins. The formation of an infectious virion requires cleavage of prM by the host furin protease during a maturation step that is dependent on a conformational change in virion structure. Here, we demonstrate that the biogenesis of flavivirus particles does not require an intact prM protein or proteolytic activation. The expression of E protein preceded by a truncated version of prM (M-E) was sufficient for the formation of noninfectious ZIKV subviral particles and pseudo-infectious reporter virions. Subviral particles encoded by a ZIKV M-E DNA vaccine elicited a neutralizing antibody response in macaques that was insensitive to the virion maturation state, a feature of flavivirus humoral immunity shown to correlate with protection. M-E vaccines that uniformly present structural features shared with mature virions offer a higher-quality and more broadly applicable approach for vaccination against flaviviruses.
Kimberly A. Dowd, Michelle Schroeder, Egan Sanchez et al.· Science Translational Medici...· 0 citations
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