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While studying transgene expression after systemic administration of lentiviral vectors, we found that splenic B cells are robustly transduced, regardless of the types of pseudotyped envelope proteins. However, the administration of two different pseudotypes resulted in transduction of two distinct B cell populations, suggesting that each pseudotype uses unique and specific receptors for its attachment and entry into splenic B cells. Single-cell RNA sequencing analysis of the transduced cells demonstrated that different pseudotypes transduce distinct B cell subpopulations characterized by specific B cell receptor (BCR) genotypes. Functional analysis of the BCRs of the transduced cells demonstrated that BCRs specific to the pseudotyping envelope proteins mediate viral entry, enabling the vectors to selectively transduce the B cell populations that are capable of producing antibodies specific to their envelope proteins. Lentiviral vector entry via the BCR activated the transduced B cells and induced proliferation and differentiation into mature effectors, such as memory B and plasma cells. BCR-mediated viral entry into clonally specific B cell subpopulations raises new concepts for understanding the biodistribution of transgene expression after systemic administration of lentiviral vectors and offers new opportunities for BCR-targeted gene delivery by pseudotyped lentiviral vectors., Competing Interests: Declaration of interests K.M. holds 2 US patents (US patent numbers 8449875 and 9163248) related to this work., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Coronavirus disease 2019 (COVID-19) is a pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). COVID-19 is defined by respiratory symptoms, but cardiac complications including viral myocarditis are also prevalent. Although ischemic and inflammatory responses caused by COVID-19 can detrimentally affect cardiac function, the direct impact of SARS-CoV-2 infection on human cardiomyocytes is not well understood. Here, we utilize human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) as a model to examine the mechanisms of cardiomyocyte-specific infection by SARS-CoV-2. Microscopy and RNA sequencing demonstrate that SARS-CoV-2 can enter hiPSC-CMs via ACE2. Viral replication and cytopathic effect induce hiPSC-CM apoptosis and cessation of beating after 72 h of infection. SARS-CoV-2 infection activates innate immune response and antiviral clearance gene pathways, while inhibiting metabolic pathways and suppressing ACE2 expression. These studies show that SARS-CoV-2 can infect hiPSC-CMs in vitro , establishing a model for elucidating infection mechanisms and potentially a cardiac-specific antiviral drug screening platform., Competing Interests: The authors declare no competing interests., (© 2020 The Author(s).)

Virus entry into cells is typically initiated by binding of virally encoded envelope proteins to specific cell surface receptors. Studying infectivity of lentivirus pseudotypes lacking envelope binding, we still observed high infectivity for some cell types. On further investigation, we discovered that this infectivity is conferred by the soluble bovine protein S in fetal calf serum, or Gas6, its human homolog. Gas6 enhances native infectivity of pseudotypes of multiple viral envelope proteins. Gas6 mediates binding of the virus to target cells by bridging virion envelope phosphatidylserine to Axl, a TAM receptor tyrosine kinase on target cells. Phagocytic clearance of apoptotic cells is known to involve bridging by Gas6. Replication of vaccinia virus, which was previously reported to use apoptotic mimicry to enter cells, is also enhanced by Gas6. These results reveal an alternative molecular mechanism of viral entry that can broaden host range and enhance infectivity of enveloped viruses., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Targeted gene transduction to organs and tissues of interest is the ultimate goal of therapeutic gene delivery. Lentiviral vectors (LVs) are powerful tools for stable gene delivery but their integration into undesired cell types poses a serious safety concern for their use in the clinic. Here we report the development of a new dual-targeted LV that can preferentially home to and express in prostate cancer bone metastases in vivo after systemic delivery. Transductional targeting is mediated by a modified Sindbis virus envelope that interacts with the prostate stem cell antigen (PSCA) expressed by prostate cancer cells, and transcriptional targeting is mediated by a prostate cell specific promoter. Homing to prostate tumors was achieved in 70% of the animals. Importantly, tumors could be detected in some cases by molecular imaging prior to X-ray detection. The dual-targeted vector presents enhanced specificity with respect to individual transcriptional or transductional targeted vectors. Transgene expression in the liver was 190 times lower than the expression associated with solely transductionally targeted vectors, and there was 12 times less vector DNA than the amount present with solely transcriptionally targeted vectors. The LV presented here is a powerful tool for obtaining stable and site-specific gene expression and can be easily modified for its use in other diseases.