Faculty Bibliography

HIV-1 envelope (Env) conformation determines the susceptibility of infected CD4⁺ T cells to antibody-dependent cellular cytotoxicity (ADCC). Upon interaction with CD4, Env adopts more "open" conformations, exposing ADCC epitopes. HIV-1 limits Env-CD4 interaction and protects infected cells against ADCC by downregulating CD4 via Nef, Vpu, and Env. Limited data exist, however, of the role of these proteins in downmodulating CD4 on infected macrophages and how this impacts Env conformation. While Nef, Vpu, and Env are all required to efficiently downregulate CD4 on infected CD4⁺ T cells, we show here that any one of these proteins is sufficient to downmodulate most CD4 from the surface of infected macrophages. Consistent with this finding, Nef and Vpu have a lesser impact on Env conformation and ADCC sensitivity in infected macrophages compared with CD4⁺ T cells. However, treatment of infected macrophages with small CD4 mimetics exposes vulnerable CD4-induced Env epitopes and sensitizes them to ADCC.

Due to the recrudescence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections worldwide, mainly caused by the Omicron variant of concern (VOC) and its sub-lineages, several jurisdictions are administering an mRNA vaccine boost. Here, we analyze humoral responses induced after the second and third doses of an mRNA vaccine in naive and previously infected donors who received their second dose with an extended 16-week interval. We observe that the extended interval elicits robust humoral responses against VOCs, but this response is significantly diminished 4 months after the second dose. Administering a boost to these individuals brings back the humoral responses to the same levels obtained after the extended second dose. Interestingly, we observe that administering a boost to individuals that initially received a short 3- to 4-week regimen elicits humoral responses similar to those observed in the long interval regimen. Nevertheless, humoral responses elicited by the boost in naive individuals do not reach those present in previously infected vaccinated individuals.

Latent reservoirs in human-immunodeficiency-virus-1 (HIV-1)-infected individuals represent a major obstacle in finding a cure for HIV-1. Hematopoietic stem and progenitor cells (HSPCs) have been described as potential HIV-1 targets, but their roles as HIV-1 reservoirs remain controversial. Here we provide additional evidence for the susceptibility of several distinct HSPC subpopulations to HIV-1 infection in vitro and in vivo. In vitro infection experiments of HSPCs were performed with different HIV-1 Env-pseudotyped lentiviral particles and with replication-competent HIV-1. Low-level infection/transduction of HSPCs, including hematopoietic stem cells (HSCs) and multipotent progenitors (MPP), was observed, preferentially via CXCR4, but also via CCR5-mediated entry. Multi-lineage colony formation in methylcellulose assays and repetitive replating of transduced cells provided functional proof of susceptibility of primitive HSPCs to HIV-1 infection. Further, the access to bone marrow samples from HIV-positive individuals facilitated the detection of HIV-1 gag cDNA copies in CD34+ cells from eight (out of eleven) individuals, with at least six of them infected with CCR5-tropic HIV-1 strains. In summary, our data confirm that primitive HSPC subpopulations are susceptible to CXCR4- and CCR5-mediated HIV-1 infection in vitro and in vivo, which qualifies these cells to contribute to the HIV-1 reservoir in patients.

Although SARS-CoV-2 mRNA vaccination has been shown to be safe and effective in the general population, immunocompromised solid organ transplant recipients (SOTRs) were reported to have impaired immune responses after one or two doses of vaccine. In this study, we examined humoral responses induced after the second and the third dose of mRNA vaccine in different SOTR (kidney, liver, lung, and heart). Compared to a cohort of SARS-CoV-2 naïve immunocompetent health care workers (HCWs), the second dose induced weak humoral responses in SOTRs, except for the liver recipients. The third dose boosted these responses but they did not reach the same level as in HCW. Interestingly, although the neutralizing activity against Delta and Omicron variants remained very low after the third dose, Fc-mediated effector functions in SOTR reached similar levels as in the HCW cohort. Whether these responses will suffice to protect SOTR from severe outcome remains to be determined.

BACKGROUND:T but not B cell numbers are decreased. COVID-19 vaccination thereby provides a model to assess whether lymphopenic platelet donors present compromised humoral immune responses. STUDY DESIGN AND METHODS/METHODS:T cell counts (76-1537 cells/μl). In addition to baseline T cell measurements, antibody binding assays to full-length Spike and the Receptor Binding Domain (RBD) were performed pre- and post-vaccination. Furthermore, pseudo-particle neutralization and antibody-dependent cellular cytotoxicity assays were conducted to measure antibody functionality. RESULTS:T cell levels minimally impacted neutralization, Spike recognition, and IgG Fc-mediated effector functions. DISCUSSION/CONCLUSIONS:Overall, our results indicate that lymphopenic plateletpheresis donors do not exhibit significant immune dysfunction; they have retained the T and B cell functionality necessary for potent antibody responses after vaccination.

We identified a Delta-Omicron SARS-CoV-2 recombinant in an unvaccinated, immunosuppressed kidney transplant recipient who had positive COVID-19 tests in December 2021 and February 2022 and was initially treated with Sotrovimab. Viral sequencing in February 2022 revealed a 5' Delta AY.45 portion and a 3' Omicron BA.1 portion with a recombination breakpoint in the spike N-terminal domain, adjacent to the Sotrovimab quaternary binding site. The recombinant virus induced cytopathic effects with characteristics of both Delta (large cells) and Omicron (cell rounding/detachment). Monitoring of immunosuppressed COVID-19 patients treated with antiviral monoclonal antibodies is crucial to detect potential selection of recombinant variants.

BACKGROUND:In 2021, Delta became the predominant SARS-CoV-2 variant worldwide. While vaccines have effectively prevented COVID-19 hospitalization and death, vaccine breakthrough infections increasingly occurred. The precise role of clinical and genomic determinants in Delta infections is not known, and whether they contributed to increased rates of breakthrough infections compared to unvaccinated controls. METHODS:We studied SARS-CoV-2 variant distribution, dynamics, and adaptive selection over time in relation to vaccine status, phylogenetic relatedness of viruses, full genome mutation profiles, and associated clinical and demographic parameters. FINDINGS/RESULTS:We show a steep and near-complete replacement of circulating variants with Delta between May and August 2021 in metropolitan New York. We observed an increase of the Delta sublineage AY.25 (14% in vaccinated, 7% in unvaccinated), its spike mutation S112L, and AY.44 (8% in vaccinated, 2% in unvaccinated) with its nsp12 mutation F192V in breakthroughs. Delta infections were associated with younger age and lower hospitalization rates than Alpha. Delta breakthrough infections increased significantly with time since vaccination, and, after adjusting for confounders, they rose at similar rates as in unvaccinated individuals. INTERPRETATION/CONCLUSIONS:We observed a modest adaptation of Delta genomes in breakthrough infections in New York, suggesting an improved genomic framework to support Delta's epidemic growth in times of waning vaccine protection despite limited impact on vaccine escape. FUNDING/BACKGROUND:The study was supported by NYU institutional funds. The NYULH Genome Technology Center is partially supported by the Cancer Center Support Grant P30CA016087 at the Laura and Isaac Perlmutter Cancer Center.

Of 379 severe acute respiratory syndrome coronavirus 2 samples collected in New York, USA, we detected 86 Omicron variant sequences containing Delta variant mutation P681R. Probable explanations were co-infection with 2 viruses or contamination/amplification artifact. Repeated library preparation with fewer cycles showed the P681R calls were artifactual. Unusual mutations should be interpreted with caution.

V2p and V2i antibodies (Abs) that are specific for epitopes in the V1V2 region of the HIV gp120 envelope (Env) do not effectively neutralize HIV but mediate Fc-dependent anti-viral activities that have been correlated with protection from, or control of HIV, SIV and SHIV infections. Here, we describe a novel molecular toolbox that allows the discrimination of antigenically and functionally distinct polyclonal V2 Ab responses. We identify different patterns of V2 Ab induction by SHIV infection and three separate vaccine regimens that aid in fine-tuning an optimized immunization protocol for inducing V2p and V2i Abs. We observe no, or weak and sporadic V2p and V2i Abs in non-vaccinated SHIV-infected NHPs, but strong V2p and/or V2i Ab responses after immunization with a V2-targeting vaccine protocol. The V2-focused vaccination is superior to both natural infection and to immunization with whole Env constructs for inducing functional V2p- and V2i-specific responses. Strikingly, levels of V2-directed Abs correlate inversely with Abs specific for peptides of V3 and C5. These data demonstrate that a V1V2-targeting vaccine has advantages over the imprecise targeting of SIV/SHIV infections and of whole Env-based immunization regimens for inducing a more focused functional V2p- and V2i-specific Ab response.

The HIV-1 Nef and Vpu accessory proteins are known to protect infected cells from antibody-dependent cellular cytotoxicity (ADCC) responses by limiting exposure of CD4-induced (CD4i) envelope (Env) epitopes at the cell surface. Although both proteins target the host receptor CD4 for degradation, the extent of their functional redundancy is unknown. Here, we developed an intracellular staining technique that permits the intracellular detection of both Nef and Vpu in primary CD4+ T cells by flow cytometry. Using this method, we show that the combined expression of Nef and Vpu predicts the susceptibility of HIV-1-infected primary CD4+ T cells to ADCC by HIV+ plasma. We also show that Vpu cannot compensate for the absence of Nef, thus providing an explanation for why some infectious molecular clones that carry a LucR reporter gene upstream of Nef render infected cells more susceptible to ADCC responses. Our method thus represents a new tool to dissect the biological activity of Nef and Vpu in the context of other host and viral proteins within single infected CD4+ T cells. IMPORTANCE HIV-1 Nef and Vpu exert several biological functions that are important for viral immune evasion, release and replication. Here, we developed a new method allowing simultaneous detection of these accessory proteins in their native form together with some of their cellular substrates. This allowed us to show that Vpu cannot compensate the lack of a functional Nef, which has implication for studies that use Nef-defective viruses to study ADCC responses.