Neutralizing Activity of Broadly Neutralizing Anti-HIV-1 Antibodies against Clade B Clinical Isolates Produced in Peripheral Blood Mononuclear Cells

ABSTRACT Recently discovered broadly neutralizing antibodies (bNAbs) against HIV-1 demonstrate extensive breadth and potency against diverse HIV-1 strains and represent a promising approach for the treatment and prevention of HIV-1 infection. The breadth and potency of these antibodies have primarily been evaluated by using panels of HIV-1 Env-pseudotyped viruses produced in 293T cells expressing molecularly cloned Env proteins. Here we report on the ability of five bNAbs currently in clinical development to neutralize circulating primary HIV-1 isolates derived from peripheral blood mononuclear cells (PBMCs) and compare the results to those obtained with the pseudovirus panels used to characterize the bNAbs. The five bNAbs demonstrated significantly less breadth and potency against clinical isolates produced in PBMCs than against Env-pseudotyped viruses. The magnitude of this difference in neutralizing activity varied, depending on the antibody epitope. Glycan-targeting antibodies showed differences of only 3- to 4-fold, while antibody 10E8, which targets the membrane-proximal external region, showed a nearly 100-fold decrease in activity between published Env-pseudotyped virus panels and PBMC-derived primary isolates. Utilizing clonal PBMC-derived primary isolates and molecular clones, we determined that the observed discrepancy in bNAb performance is due to the increased sensitivity to neutralization exhibited by 293T-produced Env-pseudotyped viruses. We also found that while full-length molecularly cloned viruses produced in 293T cells exhibit greater sensitivity to neutralization than PBMC-derived viruses do, Env-pseudotyped viruses produced in 293T cells generally exhibit even greater sensitivity to neutralization. As the clinical development of bNAbs progresses, it will be critical to determine the relevance of each of these in vitro neutralization assays to in vivo antibody performance. IMPORTANCE: Novel therapeutic and preventive strategies are needed to contain the HIV-1 epidemic. Antibodies with exceptional neutralizing activity against HIV-1 may provide several advantages to traditional HIV drugs, including an improved side-effect profile, a reduced dosing frequency, and immune enhancement. The activity of these antibodies has been established in vitro by utilizing HIV-1 Env-pseudotyped viruses derived from circulating viruses but produced in 293T cells by pairing Env proteins with a backbone vector. We tested PBMC-produced circulating viruses against five anti-HIV-1 antibodies currently in clinical development. We found that the activity of these antibodies against PBMC isolates is significantly less than that against 293T Env-pseudotyped viruses. This decline varied among the antibodies tested, with some demonstrating moderate reductions in activity and others showing an almost 100-fold reduction. As the development of these antibodies progresses, it will be critical to determine how the results of different in vitro tests correspond to performance in the clinic

Potential of conventional & bispecific broadly neutralizing antibodies for prevention of HIV-1 subtype A, C & D infections

<div><p>There is great interest in passive transfer of broadly neutralizing antibodies (bnAbs) and engineered bispecific antibodies (Abs) for prevention of HIV-1 infections due to their <i>in vitro</i> neutralization breadth and potency against global isolates and long <i>in vivo</i> half-lives. We compared the potential of eight bnAbs and two bispecific Abs currently under clinical development, and their 2 Ab combinations, to prevent infection by dominant HIV-1 subtypes in sub-Saharan Africa. Using <i>in vitro</i> neutralization data for Abs against 25 subtype A, 100 C, and 20 D pseudoviruses, we modeled neutralization by single Abs and 2 Ab combinations assuming realistic target concentrations of 10μg/ml total for bnAbs and combinations, and 5μg/ml for bispecifics. We used IC₈₀ breadth-potency, completeness of neutralization, and simultaneous coverage by both Abs in the combination as metrics to characterize prevention potential. Additionally, we predicted <i>in vivo</i> protection by Abs and combinations by modeling protection as a function of <i>in vitro</i> neutralization based on data from a macaque simian-human immunodeficiency virus (SHIV) challenge study. Our model suggests that nearly complete neutralization of a given virus is needed for <i>in vivo</i> protection (~98% neutralization for 50% relative protection). Using the above metrics, we found that bnAb combinations should outperform single bnAbs, as expected; however, different combinations are optimal for different subtypes. Remarkably, a single bispecific 10E8-iMAb, which targets HIV Env and host-cell CD4, outperformed all combinations of two conventional bnAbs, with 95–97% predicted relative protection across subtypes. Combinations that included 10E8-iMAb substantially improved protection over use of 10E8-iMAb alone. Our results highlight the promise of 10E8-iMAb and its combinations to prevent HIV-1 infections in sub-Saharan Africa.</p></div

Modeling <i>in vivo</i> protection as a function of <i>in vitro</i> neutralization.

<p>(A) The maximum likelihood model for the <i>in vivo</i> probability of infection as a function of IIP using data from the low-dose, repeated SHIV challenge macaque study [<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006860#ppat.1006860.ref021" target="_blank">21</a>] is shown in black line. This model had the same parameters across all Abs. The IIP values at the time of challenge when animals were infected are shown on top with ‘+’ and when animals were protected are shown below with ‘x’. Data for animals from different Ab groups are shown separately with different colors, and data for control animals (9 out of 33 challenges resulting in infection) are not shown. (B) The relative probability of infection as a function of concentration of the bispecific 10E8-iMAb against each clade C panel pseudovirus (grey lines) and the average across the panel viruses (red line).</p

Potential of conventional & bispecific broadly neutralizing antibodies for prevention of HIV-1 subtype A, C & D infections - Fig 1

<p><b><i>In vitro</i> neutralization data for individual antibodies against A, C & D subtype pseudovirus panels.</b> (A) Distribution of HIV-1 subtypes in sub-Saharan Africa using the “Geography Search Interface” on the Los Alamos HIV Database. (B-D) Experimental IC₈₀ titers for antibodies against subtype C, A and D panels, respectively. Viruses are represented on rows and antibodies on columns. Red-yellow shades indicate more-less potent neutralization, and blue cells indicate IC₈₀ titers above experimental threshold or 10μg/ml. (E) Comparison of IC₈₀ distributions for each antibody across subtypes. The percent of viruses in each subtype with IC₈₀ above experimental threshold for each antibody are indicated in the figure. The IC₈₀ distributions between subtypes were compared for each antibody using Wilcoxon rank sum test and comparisons with p < 0.01 are indicated.</p

Performance of bispecific Abs and 2 conventional bnAb combinations.

<p>(A-C) show the results for subtypes A, C and D, respectively. The left panels show the IC₈₀ breadth-potency curves using experimental titers for bispecifics and predicted titers for 2 bnAb combinations. The central panels show fraction maximum inhibition values for bispecific Abs and 2 bnAb combinations against viruses from a given subtype virus panel. Maximum inhibition values are calculated at 5μg/ml for bispecific Abs and at 5μg/ml of each bnAb for 2 bnAb combinations. The right panels show breadth-potency curves for 2 bnAb combination IC₈₀ titers by considering only those viruses that were neutralized by both bnAbs with single bnAb IC₈₀ < 5μg/ml.</p

Predicted <i>in vivo</i> protection for individual Abs and combinations.

<p>The average relative <i>in vivo</i> probability of infection predicted using above modeling is shown for single Abs (A), combinations of two conventional Abs (B) and combinations with one or two bispecific Abs (C) for the subtype A (left), C (middle) and D (right) panels. The curves show the relative probability of infection at a given concentration averaged over pseudoviruses from each panel. For Ab combinations, the total concentration of both Abs is shown.</p

The role of medical schools in UK students’ career intentions: findings from the AIMS study

Abstract Objectives To investigate differences in students’ career intentions between UK medical schools. Design Cross-sectional, mixed-methods online survey. Setting The primary study included all 44 UK medical schools, with this analysis comprising 42 medical schools. Participants Ten thousand four hundred eighty-six UK medical students. Main outcome measures Career intentions of medical students, focusing on differences between medical schools. Secondary outcomes included variation in medical students’ satisfaction with a prospective career in the NHS, by medical school. Results 2.89% of students intended to leave medicine altogether, with Cambridge Medical School having the highest proportion of such respondents. 32.35% of respondents planned to emigrate for practice, with Ulster medical students being the most likely. Of those intending to emigrate, the University of Central Lancashire saw the highest proportion stating no intentions to return. Cardiff Medical School had the greatest percentage of students intending to assume non-training clinical posts after completing FY2. 35.23% of participating medical students intended to leave the NHS within 2 years of graduating, with Brighton and Sussex holding the highest proportion of these respondents. Only 17.26% were satisfied with the prospect of working in the NHS, with considerable variation nationally; Barts and the London medical students had the highest rates of dissatisfaction. Conclusions This study reveals variability in students’ career sentiment across UK medical schools, emphasising the need for attention to factors influencing these trends. A concerning proportion of students intend to exit the NHS within 2 years of graduating, with substantial variation between institutions. Students’ intentions may be shaped by various factors, including curriculum focus and recruitment practices. It is imperative to re-evaluate these aspects within medical schools, whilst considering the wider national context, to improve student perceptions towards an NHS career. Future research should target underlying causes for these disparities to facilitate improvements to career satisfaction and retention. </jats:sec