However, in vitro and ex vivo assays indicate that viruses bearing subtype C Envs are invariably outcompeted by other subtype Envs in PBMC outgrowth assays [94-96]. phenotypes associated with transmission, subtype specificity, and resistance to broadly neutralizing antibodies (BNAbs). First, we profiled a panel of reference subtype B transmitted/founder (T/F) and chronic Envs (n = 12) by analyzing the infectivity of each Env across 25 unique combinations of CD4/CCR5 expression levels. Affinofile metrics revealed that at low CCR5 levels, our panel of subtype B T/F Envs was more dependent on high levels of CD4 for HIV-1 access compared to chronic Envs. Next, we analyzed a reference panel of 28 acute/early subtype A-D Envs, and noted that subtype C Envs could be distinguished ZM 449829 ZM 449829 from your other subtypes based on their infectivity profiles and relevant Affinofile metrics. Lastly, mutations known to confer resistance to VRC01 or PG6/PG19 BNAbs, when designed into subtypes A-D Envs, resulted in significantly decreased CD4/CCR5 usage efficiency. == Conclusions == GGR Affinofile profiling reveals pathophysiological phenotypes associated with varying HIV-1 access efficiencies, and spotlight the fitness costs associated with resistance to some broadly neutralizing antibodies. Keywords:Virus entry, CD4, CCR5, Receptor usage efficiency, Acute transmitted/founder envelopes, Subtype C, Broadly neutralizing antibodies, Receptor affinity profiling == Background == Human immunodeficiency computer virus type 1 (HIV-1) enters target cells through the stepwise conversation of its envelope glycoproteins (Env) with CD4 and a coreceptor, either CCR5 or CXCR4. Receptor binding induces a series of conformational changes that results in fusion pore formation and computer virus/cell membrane fusion [1]. Acutely transmitted viruses invariably use CCR5 (R5) ZM 449829 regardless of the subtype. Furthermore, although CXCR4-using (X4, R5X4) viruses can emerge ZM 449829 in approximately 40-50% of late stage HIV-1 subtype B infections [2,3], most HIV-1 infected subjects, particularly those with subtype A and C viruses [4-6], progress to late stages of infection despite exclusively harboring R5 viruses. While many viral and host factors contribute to HIV-1 progression, there is a strong body of evidence that supports some Env determinants of pathogenicity. For example, in patients with R5 viruses, isolates from late stages of infection have a greater capacity to infect macrophages [7-9], which correlates with more efficient usage of the low levels of CD4 and CCR5 expressed on these cells [9-13]. These late stage R5 isolates can also cause increased levels of cell-cell fusion [14] and CD4+ T-cell apoptosis [15]. Late stage brain isolates have also been shown to utilize low levels of CD4 and/or CCR5 for entry [16-24]. Therefore, viruses capable of exploiting limiting levels of CD4 and/or CCR5 may have expanded target cell tropism with pathological consequences [24-26]. Furthermore, viruses that are resistant to the CCR5 antagonists vicriviroc (VVC) and maraviroc (MVC) exhibit a reduced ability to use lower levels of CCR5 compared to their Mouse monoclonal to BLK non-resistant counterparts [27-29]. Finally, the recent characterization of transmitter/founder (T/F) Envs has indicated that these R5 variants enter and replicate in activated primary T-cells but not macrophages [30], underscoring the increasingly evident notion that CCR5 usage is not equivalent to macrophage-tropism [5,31]. Together, these studies show that the efficiency with which a viral Env engages CD4 and/or CCR5 can have an influence on pathogenicity, disease progression and resistance to CCR5 antagonists [5,32,33]. Therefore, a more refined understanding of how Env-CD4/CCR5 usage develops and differs under alternate evolutionary histories will inform the development and use of HIV-1 vaccines and therapeutics that target HIV-1 entry. The Affinofile system, based on a CD4 and CCR5 dual-inducible cell line, permits quantitative characterization of HIV-1 infection across 2448 distinct combinations of CD4/CCR5 expression levels [34]. Multiple groups have used this receptor affinity profiling system (Affinofile).