For each virus, the neutralization outcome is shown as a function of the tier-transformed geometric mean ID50 (Figure 3a). sera against genetically and antigenically diverse viral strains requires standardization. ID50 Etofenamate (or ID80) values, the inhibitory dilutions at which 50% (or 80%) neutralization is usually attained, are decided for a panel of viruses, using the TZM-bl neutralization assay (Sarzotti-Kelsoe et al., 2014). Serum breadth and potency are two measures used to characterize neutralization responses across virus Mouse monoclonal antibody to Hexokinase 1. Hexokinases phosphorylate glucose to produce glucose-6-phosphate, the first step in mostglucose metabolism pathways. This gene encodes a ubiquitous form of hexokinase whichlocalizes to the outer membrane of mitochondria. Mutations in this gene have been associatedwith hemolytic anemia due to hexokinase deficiency. Alternative splicing of this gene results infive transcript variants which encode different isoforms, some of which are tissue-specific. Eachisoform has a distinct N-terminus; the remainder of the protein is identical among all theisoforms. A sixth transcript variant has been described, but due to the presence of several stopcodons, it is not thought to encode a protein. [provided by RefSeq, Apr 2009] diversity. Breadth is the proportion of pseudoviruses with an ID50 score Etofenamate above the threshold of detection, and potency is the geometric mean ID50 (Hraber et al., 2014;Rademeyer et al., 2016). At least half of the variation in neutralization assay results from large panels can be explained by the averaged responses per serum, Env, and the entire panel, overall (Hraber et al., 2014). Serum breadth and potency therefore depend strongly around the Env panels used, which can vary markedly between studies. Virus neutralization sensitivity to panels of sera from chronically infected individuals represents a continuum (Seaman et al., 2010). To characterize Envs in tiers involves partitioning large neutralization panels into three or four groups with comparable sensitivity (Rademeyer et al., 2016;Seaman et al., 2010). Antibodies able to neutralize only tier 1 (most sensitive) viruses are readily elicited by HIV Env gp120 immunogens, but such tier1 responses are not protective; in human vaccine efficacy trials, such responses have been unable to confer protection against the viruses that continue to fuel the pandemic (Gilbert et al., 2010;Montefiori et al., 2012). Tier 2 viruses are more difficult to neutralize than tier 1, and represent the majority of viruses that are transmitted to establish new infections (Rademeyer et al., 2016;Seaman et al., 2010). Tier 3 viruses are the most resistant to neutralization. One difficulty with the tiered scheme for labeling viruses (i.e. tiers 1A, 1B, 2, and 3) is usually that it simplifies a continuous Etofenamate distribution into three or four categories (Seaman et al., 2010), despite wide variation within each category. Moreover, while the system categorizes viruses, it does not help compare serum neutralization potency. For example, a serum that neutralizes one tier 3 virus but only a few tier 2 viruses might subjectively be designated a tier 3 neutralizing serum, while one which neutralizes no tier 3 viruses but many tier 2 viruses a tier Etofenamate 2 serum. The latter serum is likely more potent (protective) in real-world scenarios despite being designated with a lower tier. A metric to rate sera for neutralization potency would be useful, for example to down-select vaccine candidates for further evaluation in clinical trials. Such a metric should be objective and continuous, rather than category-based. It should also provide biologically Etofenamate meaningful and interpretable values that are consistent with expectations of tiered viruses from terminology used by practitioners in this field. Here, we describe an objective, quantitative metric for serum classification, and apply it to characterize serum neutralization activity against both large and smaller panels of pseudoviruses. It uses logistic regression to establish a numerical value for a given serum, based on its ability to neutralize viruses of different tiers. We describe a statistically motivated Neutralization Potency (NP) score, which represents serum neutralization tier on a continuous, rather than categorical, scale. That scale is designed to be intuitively meaningful to HIV researchers, such that sera with a low score (near 1) are able to neutralize only tier1 viruses, while sera with scores ranging from 2 to 3 3 reflect increasing capacity to neutralize tier 2 and 3 viruses. A continuum of NP values enables comparisons between sera. Rather than suggesting most sera can neutralize tier 2 viruses, NP values can distinguish between, say, tier 2.1 and tier 2.5 sera, the higher score indicating a better neutralization outcome. The potency comparisons are similar to comparing geometric mean neutralization titers, but instead are represented in tier-like terms. Because this approach is based on the outcome of yes-or-no neutralization evaluations from a single dilution of serum, it can be.