Pouring petrol on the flames: Using oncolytic virotherapies to enhance tumour immunogenicity.

Oncolytic viruses possess the ability to infect, replicate and lyse malignantly transformed tumour cells. This oncolytic activity amplifies the therapeutic advantage and induces a form of immunogenic cell death, characterized by increased CD8 + T-cell infiltration into the tumour microenvironment. This important feature of oncolytic viruses can result in the warming up of immunologically 'cold' tumour types, presenting the enticing possibility that oncolytic virus treatment combined with immunotherapies may enhance efficacy. In this review, we assess some of the most promising candidates that might be used for oncolytic virotherapy: immunotherapy combinations. We assess their potential as separate agents or as agents combined into a single therapy, where the immunotherapy is encoded within the genome of the oncolytic virus. The development of such advanced agents will require increasingly sophisticated model systems for their preclinical assessment and evaluation. In vivo rodent model systems are fraught with limitations in this regard. Oncolytic viruses replicate selectively within human cells and therefore require human xenografts in immune-deficient mice for their evaluation. However, the use of immune-deficient rodent models hinders the ability to study immune responses against any immunomodulatory transgenes engineered within the viral genome and expressed within the tumour microenvironment. There has therefore been a shift towards the use of more sophisticated ex vivo patient-derived model systems based on organoids and explant co-cultures with immune cells, which may be more predictive of efficacy than contrived and artificial animal models. We review the best of those model systems here.

Identification of Host Trafficking Genes Required for HIV-1 Virological Synapse Formation in Dendritic Cells.

Dendritic cells (DCs) are one of the earliest targets of HIV-1 infection acting as a "Trojan horse," concealing the virus from the innate immune system and delivering it to T cells via virological synapses (VS). To explicate how the virus is trafficked through the cell to the VS and evades degradation, a high-throughput small interfering RNA screen targeting membrane trafficking proteins was performed in monocyte-derived DCs. We identified several proteins including BIN-1 and RAB7L1 that share common roles in transport from endosomal compartments. Depletion of target proteins resulted in an accumulation of virus in intracellular compartments and significantly reduced viral trans-infection via the VS. By targeting endocytic trafficking and retromer recycling to the plasma membrane, we were able to reduce the virus's ability to accumulate at budding microdomains and the VS. Thus, we identify key genes involved in a pathway within DCs that is exploited by HIV-1 to traffic to the VS.IMPORTANCE The lentivirus human immunodeficiency virus (HIV) targets and destroys CD4+ T cells, leaving the host vulnerable to life-threatening opportunistic infections associated with AIDS. Dendritic cells (DCs) form a virological synapse (VS) with CD4+ T cells, enabling the efficient transfer of virus between the two cells. We have identified cellular factors that are critical in the induction of the VS. We show that ADP-ribosylation factor 1 (ARF1), bridging integrator 1 (BIN1), and Rab GTPases RAB7L1 and RAB8A are important regulators of HIV-1 trafficking to the VS and therefore the infection of CD4+ T cells. We found these cellular factors were essential for endosomal protein trafficking and formation of the VS and that depletion of target proteins prevented virus trafficking to the plasma membrane by retaining virus in intracellular vesicles. Identification of key regulators in HIV-1 trans-infection between DC and CD4+ T cells has the potential for the development of targeted therapy to reduce trans-infection of HIV-1 in vivo.

Masters of manipulation: Viral modulation of the immunological synapse.

In order to thrive, viruses have evolved to manipulate host cell machinery for their own benefit. One major obstacle faced by pathogens is the immunological synapse. To enable efficient replication and latency in immune cells, viruses have developed a range of strategies to manipulate cellular processes involved in immunological synapse formation to evade immune detection and control T-cell activation. In vitro, viruses such as human immunodeficiency virus 1 and human T-lymphotropic virus type 1 utilise structures known as virological synapses to aid transmission of viral particles from cell to cell in a process termed trans-infection. The formation of the virological synapse provides a gateway for virus to be transferred between cells avoiding the extracellular space, preventing antibody neutralisation or recognition by complement. This review looks at how viruses are able to subvert intracellular signalling to modulate immune function to their advantage and explores the role synapse formation has in viral persistence and cell-to-cell transmission.

Capture and inactivation of viral particles from bioaerosols by electrostatic precipitation.

Infectious viral particles in bioaerosols generated during laparoscopic surgery place staff and patients at significant risk of infection and contributed to the postponement of countless surgical procedures during the COVID-19 pandemic causing excess deaths. The implementation of devices that inactivate viral particles from bioaerosols aid in preventing nosocomial viral spread. We evaluated whether electrostatic precipitation (EP) is effective in capturing and inactivating aerosolized enveloped and non-enveloped viruses. Using a closed-system model mimicking release of bioaerosols during laparoscopic surgery, known concentrations of each virus were aerosolized, exposed to EP and collected for analysis. We demonstrate that both enveloped and non-enveloped viral particles were efficiently captured and inactivated by EP, which was enhanced by increasing the voltage to 10 kV or using two discharge electrodes together at 8 kV. This study highlights EP as an effective means for capturing and inactivating viral particles in bioaerosols, which may enable continued surgical procedures during future pandemics.

Differential effects of halothane and isoflurane on carotid body glomus cell intracellular Ca2+ and background K+ channel responses to hypoxia.

We recently reported that volatile anaesthetics directly depress the isolated glomus cell response to hypoxia, halothane more so than sevoflurane, in a manner mimicking the action of these agents on the human hypoxic ventilatory response. We wished to extend these investigations to action of another agent (isoflurane), and we planned to examine the effects of this agent and halothane on background K(+) channels. In an isolated rat pup glomus cell preparation intracellular calcium [Ca(2+)]i (measured using indo-1 dye), halothane and isoflurane (0.45-2.73 MAC) depressed the Ca(2+) transient response to hypoxia (p = 0.028), halothane more than isoflurane (p < 0.001). Evaluating the effects of halothane, isoflurane (both 2.5 MAC) and hypoxia on the open probability of background TASK-like K(+) channels in cell attached patch recordings, halothane in euoxia strongly increased channel activity (2 fold) but isoflurane only increased activity by 50% (p < 0.001). In the presence of hypoxia halothane also increased channel activity (3 fold) while isoflurane again only had weak effects (p = 0.004). Thus there were marked differences between these agents on K(+) channel activity, comparable to their effects on the hypoxia induced Ca(2+) transient. When glomus cells were exposed to a depolarising stimulus using 100 mM K(+), both halothane and isoflurane modestly reduced the magnitude of the resulting Ca(2+) transient (by 44% and 10% respectively, p < 0.001). We conclude that the effect of volatile anaesthetics on the glomus cell response to hypoxia is mediated at least in part by their effect on background K(+) channels, and that this plausibly explains their whole-body effect. An additional effect on voltage-gated Ca(2+) is also possible.

Dendritic Cells Promote the Spread of Human T-Cell Leukemia Virus Type 1 via Bidirectional Interactions with CD4+ T Cells.

Human T-cell leukemia virus type 1 (HTLV-1) propagates within and between individuals via cell-to-cell transmission, and primary infection typically occurs across juxtaposed mucosal surfaces during breastfeeding or sexual intercourse. It is therefore likely that dendritic cells (DCs) are among the first potential targets for HTLV-1. However, it remains unclear how DCs contribute to virus transmission and dissemination in the early stages of infection. We show that an HTLV-1-infected cell line (MT-2) and naturally infected CD4+ T cells transfer p19+ viral particles to the surface of allogeneic DCs via cell-to-cell contacts. Similarly organized cell-to-cell contacts also facilitate DC-mediated transfer of HTLV-1 to autologous CD4+ T cells. These findings shed light on the cellular structures involved in anterograde and retrograde transmission and suggest a key role for DCs in the natural history and pathogenesis of HTLV-1 infection.

The Ticking CLOCK of HSV-2 Pathology.

Herpes simplex virus type 2 (HSV-2) is the causative agent of genital herpes. Matsuzawa et al have demonstrated that, in a mouse model, HSV-2 pathology is influenced by the time infection occurs. Increased expression of the HSV-2 receptor Nectin-1 under the control of CLOCK coincided with an increase in viral titer suggesting that HSV-2 infection is regulated by the host circadian clock.

NAADP influences excitation-contraction coupling by releasing calcium from lysosomes in atrial myocytes.

In atrial myocytes, the sarcoplasmic reticulum (SR) has an essential role in regulating the force of contraction as a consequence of its involvement in excitation-contraction coupling (ECC). Nicotinic acid adenine dinucleotide phosphate (NAADP) is a Ca(2+) mobilizing messenger that acts to release Ca(2+) from an acidic store in mammalian cells. The photorelease of NAADP in atrial myocytes increased Ca(2+) transient amplitude with no effect on accompanying action potentials or the L-type Ca(2+) current. NAADP-AM, a cell permeant form of NAADP, increased Ca(2+) spark amplitude and frequency. The effect on Ca(2+) spark frequency could be prevented by bafilomycin A1, a vacuolar H(+)-ATPase inhibitor, or by disruption of lysosomes by GPN. Bafilomycin prevented staining of acidic stores with LysoTracker red by increasing lysosomal pH. NAADP-AM also produced an increase in the lysosomal pH, as detected by a reduction in LysoSensor green fluorescence. These effects of NAADP were associated with an increase in the amount of caffeine-releasable Ca(2+) in the SR and may be regulated by ß-adrenoceptor stimulation with isoprenaline. These observations are consistent with a role for NAADP in regulating ECC in atrial myocytes by releasing Ca(2+) from an acidic store, which enhances SR Ca(2+) release by increasing SR load.