BACKGROUND:A heterologous Ad26.Mos4.HIV and clade C gp140 vaccine regimen did not show overall significant efficacy against HIV-1 acquisition [point estimate 14.1%; 95% confidence interval (CI), -22.0 to 39.5] in the HVTN 705/HPX2008 trial in southern African women. We examined whether and how vaccine efficacy (VE) against HIV-1 diagnosis over 7-24 months post-first dose varied by HIV-1 Envelope (Env) amino acid sequence features. METHODS:HIV-1 viral sequences were generated by PacBio SMRT-UMI sequencing from the first RNA-positive sample of participants who acquired HIV-1. Env amino acid sequence features were prespecified for analyses based on 1) being hypothesised to impact VE; and 2) having sufficient variability. Sieve analyses assessed VE by a single representative sequence and by viral population composition. FINDINGS:The majority of Env features showed no evidence of differential VE, with only two signals having familywise error rate (FWER) P-values <0.10. In single-sequence analyses, VE declined with increasing physicochemical-weighted Hamming distance from the C97ZA vaccine insert in clade C broadly neutralising antibody resistance-associated signature positions (FWER P = 0.08). Sequence-predicted Env structural features showed no significant vaccine vs. placebo differences in structural divergence from the C97ZA vaccine-insert Env sequence. In multi-sequence analyses (median 121 sequences/individual), VE was higher against viral populations with ≥99% vs. <99% L832 prevalence (VE = 91.7%; 95% CI, 67.4-97.9 vs. VE = -7.0%; 95% CI, -55.5 to 26.4) (unadjusted P = 0.0002 for differential VE, FWER P = 0.023). INTERPRETATION:Despite extensive prespecified and exploratory analyses including Env features supported by prior studies to potentially impact VE, there was only limited, weak evidence that Env sequence features modified VE in HVTN 705. Although previous work suggested a protective role of IgG3 binding to V1V2 in a small subgroup of vaccine recipients, a V1V2 sieve signal was absent. FUNDING:National Institutes of Health and Johnson & Johnson.

BACKGROUND:The Antibody Mediated Prevention trials (HVTN 703 and HVTN 704) demonstrated that infusions of the bnAb VRC01 prevented HIV-1 acquisition with viruses sensitive to VRC01 neutralization. We evaluated how VRC01 epitope distances differed across groups in the trials. METHODS:We calculated VRC01 epitope distances (a 3D structure informed measure of how the VRC01 epitope in a sequence differs from that epitope in known VRC01 sensitive strains) to compare >35,000 Envelopes sampled from 172 participants with mostly subtype C viruses in HVTN 703 and subtype B in HVTN 704. RESULTS:At the first visit with detectable HIV-1, we found fewer distinct VRC01 epitopes in the sequences from participants in the VRC01 high-dose group in HVTN 704 (p=0.054), suggesting that some epitope variants were blocked in these participants who harbored subtype B viruses. In both trials, VRC01 epitope distances were significantly larger in the VRC01 high-dose groups than in the placebo groups (p≤0.010). Moreover, sequences sampled in the first month after diagnosis showed that the rate of change in VRC01 epitope distances was significantly higher in the VRC01 groups than in the placebo in the HVTN 703 trial (p≤0.036). CONCLUSIONS:These findings show the impact of sieve acquisition (variants blocked among subtype B viruses) and post-acquisition (stronger impact of VRC01-mediated escape in subtype C) effects, highlighting a complex intersection between HIV-1 subtypes, escape pathways and antibody-mediated prevention. The differential pressure exerted by VRC01 on subtype B vs. C viruses emphasizes that escape pathways need to be considered when selecting bnAbs for clinical trials.

Understanding the selective forces acting upon HIV early in infection is crucial to design prevention strategies. By leveraging deep sequencing and the short diagnostic intervals of the FRESH and RV217 cohorts (median 4 days) between the last-negative and first-positive RNA tests, we captured a precise and early snapshot of acute HIV infection. The frequency of multiple transmitted viruses of 38% in these as well as placebo recipients from the AMP trials was higher than previously published, with the true frequency likely to be higher. The relative abundance of lineages fluctuated substantially over time in two-thirds of the multilineage infections, generating uncertainty in identifying the specific viruses that were transmitted and founding the infection. Viral populations exhibited diversity and selection on the Gag and Env proteins at the earliest times examined, with sites inferred to be undergoing negative selection most evident. These data may help explain vaccination failures and provide new targets for prevention.

Abstract In the antibody mediated prevention (AMP) trials, the broadly neutralizing antibody (bNAb) VRC01 demonstrated protective efficacy against susceptible HIV strains. To understand how VRC01 shaped breakthrough infections, deep sequencing was performed on 172 participants (>100,000 gag-Δpol and rev-env-Δnef sequences), at diagnosis and over time, in the placebo and treatment arms of the African (HVTN703/HPTN081; NCT02568215) and Americas/Europe (HVTN704/HPTN085; NCT02716675) cohorts. A high frequency of multilineage infections was detected (38%), including co-infection with both VRC01 sensitive and resistant viruses. This high frequency is largely accounted for by low-abundance lineages. Although VRC01 does not significantly affect the genetic transmission bottleneck compared to placebo, higher VRC01 doses trend towards greater VRC01 neutralization differences among co-infecting lineages. Two-thirds of multilineage infections showed evidence of recombination at the diagnostic timepoint. In the treatment group there is evidence of recombinant viruses preferentially inheriting resistance-associated mutations. This study provides critical insights into viral genetic and antigenic diversity that needs to be targeted to achieve protection, and highlights the role of recombination in facilitating escape.

Although a protective HIV-1 vaccine has not yet been realized, significant progress has been made in vaccine designs that trigger B cell lineages with potential to produce broadly neutralizing antibodies (bnAbs). Advancing these strategies by optimizing vaccine boosting regimens requires early detection of maturing antibodies with neutralizing activity against native envelope glycoprotein (Env) trimers and streamlined strategies to identify antibodies as they begin to manifest desired levels of breadth and potency. Thus, we designed three types of pseudovirus screening panels based on Envs of contemporary HIV-1 isolates to facilitate detection of bnAb lineages that are on favorable trajectories during a vaccination course. The panels were selected from Tier 2 Transmitted Founder Lineage (TFL) HIV-1 Envs from placebo participants in the Antibody Mediated Prevention (AMP) efficacy trials. Using 15 bnAbs to evaluate the neutralization sensitivity of the viruses, we selected 8-member bnAb class-specific panels most sensitive to bnAbs representing their class: V2-apex, V3-glycan, CD4-receptor binding site (CD4bs), Membrane-Proximal External Region (MPER), or fusion peptide (FP). Next, we combined the most sensitive viruses among the class-specific panels to create a 12-virus panel to enable optimal detection of low-titer bnAb activity across epitope specificities. Finally, as HIV-1 continues to evolve greater levels of antigenic diversity and as current global pseudoviruses bnAb panels rely on viruses collected more than twenty years ago, we showed the importance of using contemporary viral panels to assess bnAb breadth and potency and designed a 12-virus panel representative of the spectrum neutralization profiles among AMP placebo viruses. We characterized pseudoviruses bearing each selected Env using standardized human sera to confirm their Tier 2 status and biological relevance. These updated panels enable sensitive screening of neutralization activity in vaccine studies and can also provide a realistic assessment of the expected breadth and potency of maturing responses against contemporary HIV-1 Envs.

Understanding broadly neutralizing antibody (bnAb) lineage development in rhesus macaques (RMs) infected with simian-human immunodeficiency virus (SHIV) may inform HIV-1 vaccine designs. We analyzed HIV-1 envelope (Env)-antibody coevolution in 18 RMs infected with SHIV.BG505 (subtype A) and found conserved patterns of antibody recognition and Env escape, including in three animals that developed V3-glycan-reactive bnAbs. From one RM with V3-glycan-targeted plasma Abs that neutralized heterologous HIV-1 strains, we isolated 203 members of a single clonal antibody lineage designated DH1030. DH1030 antibodies demonstrated genetic, functional, and structural similarities with the human V3-glycan bnAb lineage DH270, which was isolated from an individual with subtype C HIV-1 CH848 infection. Human-DH270 and macaque-DH1030 bnAbs shared early improbable mutations in the heavy chain complementarity determining region 2 that were critical for bnAb development. These convergent patterns of antibody evolution, accumulation of key improbable mutations, and mode of epitope recognition were shared across primate species and distinct HIV-1 subtypes, findings that may be leveraged in HIV-1 vaccine designs. Furthermore, our data highlight the value of SHIV-infected macaques as an outbred model system to explore conserved molecular pathways of bnAb development after infection and vaccination.

Broadly neutralizing antibodies (bNAbs) show promise for HIV treatment and prevention, but are vulnerable to resistance evolution. Comprehensively understanding in vivo viral escape from individual bNAbs is necessary to design bNAb combinations that will provide durable responses. We characterize viral escape from two such bNAbs, 10-1074 and 3BNC117, using deep, longitudinal sequencing of full-length HIV envelope (env) genes from study participants treated with bNAb monotherapy. Improved sequencing depth and computational evolutionary analyses permit us to identify in vivo routes and parallelism underlying HIV escape from each bNAb, providing insight into this evolutionary process. We find that 10-1074 escape is restricted to a small number of previously documented pathways seen across participants, but these escape mutations 1) emerge via extensively recurrent mutation, 2) are not equally preferred, and 3) can preexist at low frequency in intrahost viral populations before therapy, although their detection does not predict rebound timing. In contrast, 3BNC117 escape follows background-specific patterns in which specific escape mutations present in one intrahost population rarely emerge or spread in other populations, except among highly related viruses. Despite this, 3BNC117 escape mutations can still emerge recurrently within their host. Our findings map longitudinal in vivo antibody escape across 20 diverse clade B HIV intrahost populations and reveal clinically relevant resistance dynamics that highlight how combination bNAb therapies will need to contend with extensively recurring escape mutations and dependence on genetic background.

Newborns represent only 1% of the population. Yet, HIV vertical transmissions represent 10% of all new infections globally, even though antiretroviral therapy (ART) has been shown to reduce the risk of vertical transmission to less than 2%. While vaccines still represent the most efficient and cost-effective intervention to eradicate new infections, HIV immunogens that can effectively elicit broad-spectrum protection are still at least a decade away. In contrast, passive immunization with broadly neutralizing antibody (bnAb) combinations has the potential to provide a more immediate pathway to HIV prophylaxis. Early-phase infant trials are underway to establish the safety and pharmacokinetics of bnAb combinations selected for their potency against viruses acquired via adult transmissions. However, the specific characteristics and phenotypic differences of vertically transmitted viruses in infants compared to those in adults remain uncertain, including their susceptibility to known broadly neutralizing antibodies (bnAbs). We review the current knowledge of vertically transmitted HIV viruses, including their genetics and phenotypic features. Differences in immunity between adults and infants lead us to hypothesize that distinct selection and evolutionary pressures act on the virus at the time of transmission and during the early phases of infection, and these may in turn affect the choice of bnAb combinations needed for protection against vertical transmission of HIV.

HIV viruses that establish infection possess phenotypic and genotypic characteristics that have been selected for and that differ across transmission routes, including their susceptibility to broadly neutralizing antibodies (bnAbs). While sexually transmitted viruses have been well characterized, studies of vertically transmitted viruses are sparse and from cohorts that are often small in size and more than a decade old. To investigate whether viruses transmitted vertically during lactation possess distinct neutralization profiles compared to viruses transmitted sexually, we compared the neutralization sensitivity of 25 clade C breastmilk viruses to that of 99 contemporaneous clade C viruses from sera of adults with sexual acquisition against three bnAbs in clinical development. Three out of 7 breastmilk donors (43%) had one or more viruses resistant to 2 or more bnAbs, compared to 8 out of 99 (8%) contemporaneous adult viruses (p=0.02). Breastmilk viruses were more resistant to PGT121 and VRC07.523 (median IC80 >50 compared to 1.16 for PGT121, and 12.75 vs. 0.38 for VRC07.523; p=0.013 and <0.001 respectively), and more breastmilk viruses than adult viruses were resistant to VRC07.523 (94% vs. 43%, p=0.001). Interestingly, the breastmilk viruses most resistant to VRC07.523 had on average one or more glycans in V3 compared to adult transmitted viruses (median 3 vs. 2 glycosylation sites, including flanking position 295; p=0.009), and the number of V3 glycans was negatively correlated with VRC07.523 sensitivity (p=0.007). These findings highlight potential differences in bnAb susceptibility of vertically transmitted viruses and emphasize the need to increase sequencing efforts and screening of infant viruses to better inform the efficacy of candidate bnAbs to prevent vertical transmission of HIV.

Developing an effective HIV vaccine is a momentous challenge. An exceptionally wide range of candidate HIV vaccines have been tested, yet many were poorly immunogenic, and of the select few that advanced into efficacy trials, only one demonstrated any efficacy. Here we report the results of the largest-scale cross-protocol immunogenicity comparison to date: 13 HIV vaccine trials (including 36 vaccine regimens) conducted across nine countries worldwide, strengthened by standardized trial designs, validated assays in centralized laboratories, and harmonized immunogenicity endpoints - providing an objective approach to identify the HIV vaccine candidate(s) with the best immunogenicity. A polyvalent DNA prime + protein boost regimen (HVTN 124) including Env immunogens of four subtypes, matched between prime and boost, achieved the best anti-V1V2 antibody responses by a large margin and also induced high CD4+ T-cell responses - two key immune responses implicated in HIV vaccine protection. Our results provide strong support to test this promising HIV vaccine design in more advanced phase clinical trials and will also guide the future design of additional HIV vaccines.Trial registration: ClinicalTrials.gov identifier: NCT01799954..Trial registration: ClinicalTrials.gov identifier: NCT02109354..Trial registration: ClinicalTrials.gov identifier: NCT02404311..Trial registration: ClinicalTrials.gov identifier: NCT02207920..Trial registration: ClinicalTrials.gov identifier: NCT02296541..Trial registration: ClinicalTrials.gov identifier: NCT03284710..Trial registration: ClinicalTrials.gov identifier: NCT02915016..Trial registration: ClinicalTrials.gov identifier: NCT02997969..Trial registration: ClinicalTrials.gov identifier: NCT03122223..Trial registration: ClinicalTrials.gov identifier: NCT03409276..Trial registration: ClinicalTrials.gov identifier: NCT02968849..Trial registration: ClinicalTrials.gov identifier: NCT03060629..Trial registration: ClinicalTrials.gov identifier: NCT00223080..

Accurate timing estimates of when participants acquire HIV in HIV prevention trials are necessary for determining antibody levels at acquisition. The Antibody-Mediated Prevention (AMP) Studies showed that a passively administered broadly neutralizing antibody can prevent the acquisition of HIV from a neutralization-sensitive virus. We developed a pipeline for estimating the date of detectable HIV acquisition (DDA) in AMP Study participants using diagnostic and viral sequence data. Using a Bayesian strategy that combines three streams of data (REN [rev/vpu/env/Δnef] sequence, GP [gag/Δpol] sequence, and diagnostic) where their 95% credible intervals overlap based on pre-specified criteria and decision rules. We evaluated the performance of our AMP pipeline using PacBio viral sequence data from 41 participants across two prospective acute HIV acquisition cohort studies, FRESH and RV217, with twice-weekly sampling. These cohort studies enrolled young women in South Africa and men and women in Kenya and Thailand, respectively, with a high likelihood of HIV acquisition. In evaluating performance, "true DDA" was the center of bounds between last-negative and first-positive RNA diagnostic tests (median time 4 days, range 2-7 days); bias was the mean difference between estimated and true DDA. Using diagnostic data alone yielded timing estimates with a bias of 2.4 days and root mean square error (RMSE) of 7.9 days. These results were improved using sequence + diagnostic data (bias 1.5 days, RMSE 6.9 days), as well as by restricting sequence-based estimation to samples from ≤5 weeks post-DDA (bias 0.2 days, RMSE 7.8 days).IMPORTANCEIn HIV prevention trials, accurate timing estimates of when individual participants acquire HIV can be used to estimate antibody levels at the time of acquisition, which is useful for projecting antibody levels needed for prevention. The results we report here suggest that if sequence-based estimation of acquisition timing is used in future clinical trials of combination broadly neutralizing antibody (bnAb) regimens or multispecific bnAbs for HIV prevention, a sampling frequency of at least monthly is needed. Moreover, in the samples analyzed here, we observed less bias in sequence-based timing estimation for samples taken <5 weeks post-DDA. This observation is consistent with the timing of immune-driven selective pressures that may negatively impact the power to detect acquisition sieve effects.

Broadly neutralizing antibodies (bNAbs) show promise for HIV treatment and prevention, but are vulnerable to resistance evolution. Comprehensively understanding in vivo viral escape from individual bNAbs is necessary to design bNAb combinations that will provide durable responses. We characterize viral escape from two such bNAbs, 10-1074 and 3BNC117, using deep, longitudinal sequencing of full length HIV envelope (env) genes from study participants treated with bNAb monotherapy. Improved sequencing depth and computational evolutionary analyses permit us to identify in vivo routes and parallelism underlying HIV escape from each bNAb, providing new insights into this evolutionary process: 10-1074 escape is restricted to a small number of previously documented pathways, but these escape mutations 1) pre-exist in intra-host viral populations before therapy, 2) are not all equally preferred, and 3) emerge with a high degree of genetic parallelism within and across viral populations. In contrast, 3BNC117 escape follows background-specific patterns in which specific escape mutations present in one population rarely emerge or spread in other populations, but often still exhibit parallel evolutionary responses within their host. That bNAbs elicit starkly different in vivo escape profiles depending on their Env target exposes the limitations of generalizing escape patterns across therapies and highlights the substantial challenges in predicting a viral population's bNAb susceptibility from genetic diversity alone.

Broadly neutralizing antibodies (bnAbs) show promise in HIV prevention, yet viral escape remains a challenge. In the Antibody Mediated Prevention (AMP) trials, the CD4 binding site (CD4bs) bNAb VRC01 blocked acquisition by VRC01-sensitive strains. However, its influence on viral evolution post-acquisition is not fully understood. Here we analyzed >12,000 HIV env sequences from 47 participants from the AMP trials, identifying VRC01-mediated de novo escape mutations in 8 of 26 VRC01-treated participants but none in 21 placebo participants. These mutations were found at very low frequency (<1%) in global viruses. Escape mutations, primarily located in the Loop-D and β23/V5 regions of Env, conferred cross-resistance to several CD4bs bnAbs, while more potent CD4bs bnAbs like N6 and 1-18 largely retained their activity. Our findings demonstrate that prophylactic VRC01 can select for viral escape after infection, underscoring the need for next-generation bnAbs with improved breadth and potency to enhance durability and efficacy of antibody-based HIV prevention.

BACKGROUND:The HVTN 705 Imbokodo trial of 2636 people without HIV and assigned female sex at birth, conducted in southern Africa, evaluated a heterologous HIV-1 vaccine regimen: mosaic adenovirus 26-based vaccine (Ad26.Mos4.HIV) at Months 0, 3, 6, 12 and alum-adjuvanted clade C gp140 at Months 6, 12. Per-protocol vaccine efficacy (VE) against HIV-1 diagnosis from seven to 24 months was 14.1% (95% CI: -22.0% to 39.5%). Immune correlates analysis was performed for markers selected based on prior evidence in efficacy trials and/or nonhuman primate models. METHODS:Humoral and cellular immune response markers at Month 7 were evaluated as immune correlates of risk and of protection in a breakthrough case-control cohort (n = 52 cases, 246 non-cases). Primary markers were IgG binding to vaccine-strain gp140, IgG3 binding to diverse Env antigens (IgG3 Env breadth), IgG3 binding to diverse V1V2 antigens (IgG3 V1V2 breadth), antibody-dependent phagocytosis against the vaccine-strain gp140, Env-specific CD4+ and CD8+ T-cell responses, and multi-epitope functions. FINDINGS:No immune markers were statistically significant correlates of risk. IgG3 V1V2 breadth trended toward an inverse association: hazard ratio 0.70 (95% CI: 0.36 to 1.35; p = 0.29) per 10-fold increase and 0.51 (95% CI: 0.21 to 1.24; p = 0.14) in a Cox model with all primary markers. The VE estimate was 11.8% (95% CI: -17.9% to 34.0%) at all IgG3 V1V2 breadth values below 667 weighted geometric mean net MFI; just above this value, the VE estimate sharply increased to 62.6% (95% CI: -17.9% to 89.6%), and further increased to 80.9% (95% CI: -17.9% to 99.5%) at 1471 MFI, the 95th percentile of the marker distribution. Mediation analysis yielded a VE of 35.7% (95% CI: 15.0% to 51.3%) attributable to the vaccine's impact on this marker. INTERPRETATION:The trend in association of greater IgG3 V1V2 antibody breadth with lower likelihood of HIV acquisition is consistent with the identification of antibodies against V1V2 as immune correlates in three other HIV vaccine efficacy trials and suggests that a greater emphasis should be placed on studying this region in the HIV-1 envelope as a vaccine immunogen. FUNDING:National Institute of Allergy and Infectious Diseases and Janssen Vaccines & Prevention BV.

The details of the pediatric immune system that supports induction of antibodies capable of neutralizing geographically-diverse or heterologous HIV-1 is currently unclear. Here we explore the pediatric immune environment in neonatal macaque undergoing Simian-HIV infection. Simian-HIV infection of 11 pairs of therapy-naive dams and infant rhesus macaques for 24 months results in heterologous HIV-1 neutralizing antibodies in 64% of young macaques compared to 18% of adult macaques. Heterologous HIV-1 neutralizing antibodies emerge by 12 months post-infection in young macaques, in association with lower expression of immunosuppressive genes, fewer germinal center CD4 + T regulatory cells, and a lower ratio of CD4 + T follicular regulatory to helper cells. Antibodies from peripheral blood B cells in two young macaques following SHIV infection neutralize 13% of 119 heterologous HIV-1 strains and map to regions of canonical broadly neutralizing antibody epitopes on the envelope surface protein. Here we show that pediatric immunity to SHIV infection in a macaque model may inform vaccine strategies to induce effective HIV-1 neutralizing antibodies in infants and children prior to viral exposure. The specifics of the pediatric immune response that gives rise to antibodies capable of neutralising diverse HIV-1 strains is not fully understood. Here the authors characterise the immune environment of Simian-HIV infected paediatric macaques and link to antibody neutralisation induction.

Human immunodeficiency virus type 1 (HIV-1)-specific broadly neutralizing monoclonal antibodies (bNAbs) have to date shown transient viral suppression when administered as monotherapy or as a cocktail of two antibodies(1-4). A combination of three bNAbs provides improved neutralization coverage of global viruses, which may more potently suppress viral escape and rebound5-7. Here we performed an open-label, two-part study evaluating a single intravenous dose of HIV-1 bNAbs, PGT121, PGDM1400 and VRC07-523LS, in six adults without HIV in part 1 and a multicenter trial of up to six monthly infusions of these three bNAbs in 12 people living with HIV with an antiretroviral therapy (ART) interruption in part 2. The primary endpoints were safety, tolerability and pharmacokinetics, and the secondary endpoints in part 2 were antiviral activity following ART discontinuation, changes in CD4+ T cell counts and development of HIV-1 sequence mutations associated with bNAb resistance. The trial met its prespecified endpoints. The bNAb treatment was generally safe and well tolerated. In part 2, 83% of participants (10 of 12) maintained virologic suppression for the duration of antibody therapy for at least 28 weeks, and 42% of participants (5 of 12) showed virologic suppression for at least 38-44 weeks, despite the decline of serum bNAb concentrations to low or undetectable levels. In exploratory analyses, early viral rebound in two individuals correlated with baseline resistance to PGT121 and PGDM1400, whereas long-term virologic control in five individuals correlated with reduced immune activation, T cell exhaustion and proinflammatory signaling following bNAb therapy. Our data show the potential of a triple bNAb cocktail to suppress HIV-1 in the absence of ART. ClinicalTrials.gov registration: NCT03721510.

We recently demonstrated that Simian-HIV (SHIV)-infected neonate rhesus macaques (RMs) generated heterologous HIV-1 neutralizing antibodies (NAbs) with broadly-NAb (bNAb) characteristics at a higher frequency compared with their corresponding dam. Here, we characterized genetic diversity in Env sequences from four neonate or adult/dam RM pairs: in two pairs, neonate and dam RMs made heterologous HIV-1 NAbs; in one pair, neither the neonate nor the dam made heterologous HIV-1 NAbs; and in another pair, only the neonate made heterologous HIV-1 NAbs. Phylogenetic and sequence diversity analyses of longitudinal Envs revealed that a higher genetic diversity, within the host and away from the infecting SHIV strain, was correlated with heterologous HIV-1 NAb development. We identified 22 Env variable sites, of which 9 were associated with heterologous HIV-1 NAb development; 3/9 sites had mutations previously linked to HIV-1 Env bNAb development. These data suggested that viral diversity drives heterologous HIV-1 NAb development, and the faster accumulation of viral diversity in neonate RMs may be a potential mechanism underlying bNAb induction in pediatric populations. Moreover, these data may inform candidate Env immunogens to guide precursor B cells to bNAb status via vaccination by the Env-based selection of bNAb lineage members with the appropriate mutations associated with neutralization breadth.