Hybrid spreading mechanisms and T cell activation shape the dynamics of HIV-1 infection

HIV-1 can disseminate between susceptible cells by two mechanisms: cell-free infection following fluid-phase diffusion of virions and by highly-efficient direct cell-to-cell transmission at immune cell contacts. The contribution of this hybrid spreading mechanism, which is also a characteristic of some important computer worm outbreaks, to HIV-1 progression in vivo remains unknown. Here we present a new mathematical model that explicitly incorporates the ability of HIV-1 to use hybrid spreading mechanisms and evaluate the consequences for HIV-1 pathogenenesis. The model captures the major phases of the HIV-1 infection course of a cohort of treatment naive patients and also accurately predicts the results of the Short Pulse Anti-Retroviral Therapy at Seroconversion (SPARTAC) trial. Using this model we find that hybrid spreading is critical to seed and establish infection, and that cell-to-cell spread and increased CD4+ T cell activation are important for HIV-1 progression. Notably, the model predicts that cell-to-cell spread becomes increasingly effective as infection progresses and thus may present a considerable treatment barrier. Deriving predictions of various treatments' influence on HIV-1 progression highlights the importance of earlier intervention and suggests that treatments effectively targeting cell-to-cell HIV-1 spread can delay progression to AIDS. This study suggests that hybrid spreading is a fundamental feature of HIV infection, and provides the mathematical framework incorporating this feature with which to evaluate future therapeutic strategies

HIV-1-Induced Cell-Cell Fusion: Host Regulation And Consequences For Viral Spread

Human immunodeficiency virus type 1 (HIV-1) is a human retrovirus of the lentivirus subgroup which primarily infects T cells and macrophages, and causes acquired immune deficiency syndrome (AIDS). Since its emergence in the early 1980s, HIV-1 has caused a global pandemic which is still responsible for over one million deaths per year, primarily in sub-Saharan Africa. HIV-1 has been the subject of intense study for over three decades, which has resulted not only in major advances in cell biology, but also in numerous drug treatments that effectively control the infection. However, cessation of treatment always results in reemergence of the infection due to the ability of HIV-1 (and other lentiviruses) to establish a persistent quiescent infection known as latency. The elimination of latently-infected cells is the primary goal of current research towards a cure for HIV-1, alongside efforts to develop vaccines, which have thus far been fruitless. The spread of HIV-1 to susceptible target cells (which express the receptor CD4 and a co-receptor; CXCR4 or CCR5) can take place when antigen-presenting cells, such as dendritic cells, capture virus particles and then pass them on to target cells, without themselves becoming infected. Alternatively, productively infected T cells or macrophages can spread HIV-1 either by shedding virus particles to the milieu, which are then stochastically acquired by target cells, or through transient contacts between infected and uninfected cells known as virological synapses (VSs). VS-mediated cell-to-cell transmission is thought to be highly efficient due to the release of virus directly onto (or very near to) a target cell, and some evidence suggests that the VS is a privileged site which allows the virus to evade neutralizing antibodies and drugs. However, and most importantly, it is of central interest to us because the same transient cell adhesions that facilitate virus transfer can also result in the fusion of the two cells to form a syncytium, due to the presence of the viral fusogen Env and its receptor and co-receptor on either side of the VS. While T cell syncytia can be found in vivo, they remain small, and it appears that the majority of VSs resolve without fusion. The regulation of HIV-1-induced cell-cell fusion and the fate of those syncytia are the focus of the work presented here. A family of host transmembrane proteins, the tetraspanins, which regulate cell-cell fusion in other contexts (e.g. the fusion of myoblasts to form and maintain myotubes), were found to inhibit HIV-1-induced cell-cell fusion. Our investigations have further characterized this regulation, concluding that tetraspanins allow cells to reach the fusion intermediate known as hemifusion before their ability to repress fusion takes effect. In parallel, because syncytia are nevertheless found both in infected individuals and in a humanized mouse model for HIV-1, we also became interested in whether small T cell-based syncytia were able to participate in HIV-1 spread by transmitting virus to target cells. Using a simple three dimensional in vitro culture system which closely recapitulates those in situ observations, we found that small syncytia can contact target cells and transmit virus without fusing with them. Overall, these studies further our understanding of HIV-1-induced syncytia and reveal a previously unrecognized role for these entities as active participants in HIV-1 spread

Experimental and computational analyses reveal that environmental restrictions shape HIV-1 spread in 3D cultures

Here, using an integrative experimental and computational approach, Imle et al. show how cell motility and density affect HIV cell-associated transmission in a three-dimensional tissue-like culture system of CD4+ T cells and collagen, and how different collagen matrices restrict infection by cell-free virions

Psychiatric Co-Morbidity in People with HIV/AIDS: A Cross Sectional Study

BACKGROUND: Infection with Human Immunodeficiency Virus (HIV) and its end stage, Acquired Immunodeficiency Syndrome (AIDS) is the major public health challenge of our times, the majority of whom, without access to therapy. Psychiatric co morbidity in HIV/AIDS is an important factor in determining the course and outcome of HIV/AIDS and is associated with treatment follow-up factors like defaulting and poor compliance. Proper identification and treatment of psychiatric co morbidity will help improve patient adherence and quality of life and illness outcome in HIV/AIDS. AIM AND OBJECTIVES: 1. To assess the prevalence of psychiatric illnesses in people undergoing treatment for HIV/AIDS. 2. To assess the association between psychiatric co morbidity and different sociodemographic factors (age, gender, education) and disease related factors (duration of illness, stages of HIV/AIDS, CD4 count, HIV-TB and other co infections and other opportunistic infections). MATERIAL AND METHODS: This is a cross sectional study, Patients attending ART center, at Govt. Kilpauk Medical College Hospital and diagnosed as having HIV/AIDS and receiving treatment and who are willing to participate are included. A semistructured sociodemographic proforma administered to all the participants. And psychiatric comorbidity were diagnosed by using ICD-10 and various scales were administered according to psychiatric diagnosis. RESULTS: Prevalence of psychiatric illnesses in our study population was 45%. Depressive disorder was the commonest morbidity (21.1%), followed by alcohol dependence syndrome (9.2%), Adjustment disorder (8.3), Psychosis (2.8%), and nicotine dependence syndrome (1.8%), and anxiety disorders (1.8%)

Analysis Of Host Factors Involved In Regulating Hiv-1-Induced Syncytium Formation

Human Immunodeficiency Virus type 1 (HIV-1) is a retrovirus and the causative agent of Acquired Immunodeficiency Syndrome (AIDS). HIV-1 can spread through multiple modes of transmission including cell-to-cell transmission between CD4+ T cells at a transient junction known as the virological synapse (VS). The VS forms upon HIV-1 Envelope (Env) on the surface of an infected (producer) cell binding CD4 on an uninfected (target) cell. While the VS typically resolves with complete cell separation and transfer of virus particles, Env can occasionally facilitate cell-cell fusion at this site, forming a multinucleated infected cell (syncytium). Excessive syncytium formation is prevented by viral and host factors, though this subpopulation of infected cells can still comprise ~20% of all infected cells in vivo. T cell-based syncytia detected in vivo are unique from mononucleated infected cells as they contain 2-4 nuclei, can have an elongated morphology, and appear highly motile. Despite such significant presence of syncytia, little is known about how these multinucleated infected entities contribute to HIV-1 spread and pathogenesis. During cell-to-cell transmission at the VS, viral and host factors are enriched at this site to support virus spread (reviewed in Chapter 2). This thesis focused on fusion inhibitory factors HIV-1 Gag and several host proteins, including tetraspanins, ezrin, and EWI-2. We determined that EWI-2 is recruited specifically to the producer cell side of the VS (the presynapse) where it inhibits HIV-1-induced cell-cell fusion in a dose-dependent manner (Chapter 3). Although both EWI-2 and tetraspanins are typically downregulated upon infection, both tetraspanin CD81 and EWI-2 surface levels are partially restored on HIV-1-induced CD4+ primary T cell-based syncytia compared to mononucleated infected cells. We sought to determine whether target cells influence the surface profile upon fusion and whether the altered protein levels are maintained for the lifetime of a syncytium (Chapter 4). We demonstrated that EWI-2 surface levels on syncytia correlate with levels of the target cell population, suggesting that EWI-2 brought along by target cells at least partially restores surface expression in syncytia. Further, we determined that newly formed, “young” syncytia, have higher levels of EWI-2 than older ones, suggesting that downregulation of EWI-2 continues in syncytia. We expect that higher levels of EWI-2 on young syncytia will render them less susceptible to continued cell-cell fusion than mononucleated infected cells and may also reduce virus particle infectivity. This will be tested by analysis of a purified syncytia population to measure fusogenicity and particle infectivity relative to fusogenicity and particle infectivity of mononucleated infected cells. Those data will be included in a future manuscript. Collectively, the work presented in this dissertation has furthered our understanding of HIV-1-induced cell-cell fusion regulation and allowed us to characterize distinct differences in protein expression between syncytia and mononucleated infected cells. These findings open the door to future investigations aimed at understanding how syncytia contribute to virus transmission and pathogenesis

The Role of Pyroptosis and Associated Inflammasomes during Experimental Cytomegalovirus Retinitis

Human cytomegalovirus (HCMV) is a species-specific β-herpesvirus that establishes a lifelong latent infection in ~80% of the world’s population and can cause severe opportunistic diseases in immunosuppressed patients including those with AIDS. Of these, AIDS-related HCMV retinitis is a significant ophthalmological problem worldwide. Although the clinical features of AIDS-related HCMV retinitis are well established, the virologic and immunologic events that take place during onset and development of this sight-threatening retinal disease remain poorly understood. Toward this end, an established animal model of murine cytomegalovirus (MCMV) retinitis in mice with retrovirus-induced immunodeficiency (MAIDS) that mimics AIDS-related HCMV retinitis was used in the present investigation to test the central hypothesis that pyroptosis, as a programmed cell death pathway of innate immunity, and associated inflammasomes contribute to the onset and development of full-thickness retinal necrosis during MAIDS-related MCMV retinitis. Our findings show (i) intraocular MCMV infection stimulates key pyroptosis-associated transcripts and proteins within the eyes of retinitis-susceptible MAIDS mice but not within the eyes of retinitis-resistant mice; (ii) a deficiency in key pyroptosis-associated molecules and inflammasomes in MAIDS mice results in an atypical histopathologic pattern of retinal disease within MCMV-infected eyes characterized by preservation of the neurosensory retina without full-thickness retinal necrosis but with proliferation of the retinal pigmented epithelium; (iii) MCMV-infected eyes of corticosteroid-immunosuppressed mice display stimulation of key pyroptosis-associated molecules and inflammasomes similar to that observed for MCMV-infected eyes of mice with MAIDS; (iv) MCMV infection of IC-21 macrophages and mouse embryo fibroblasts grown in culture stimulates key pyroptosis-associated transcripts in a cell-type specific manner; and (v) increased susceptibility to MCMV retinitis during the progression of MAIDS is associated with robust upregulation of a surprisingly large number of immune response genes that operate within several immune response pathways. Taken together, these results suggest that pyroptosis and associated inflammasomes play a significant role during the pathogenesis of full-thickness retinal necrosis within MCMV-infected eyes during MAIDS. These findings add new knowledge to our understanding of the contributions of programmed cell death pathways of innate immunity towards the pathogenesis of AIDS-related HCMV retinitis and may extend to other AIDS-related opportunistic virus infections

Investigating the monitoring and evaluation process of HIV/AIDS programmes by non-governmental organizations in KwaZulu-Natal province

In South Africa, HIV/AIDS takes the lead, and this is a serious health concern. Being a country that is mostly affected by this epidemic, various stakeholders such as international organizations, Non-governmental organizations, private organizations and government organizations have come up with a collaborative effort to manage the epidemic. Through various interventions, it has been noted that monitoring and evaluation of HIV/AIDS remains underdeveloped. The purpose of this study was to investigate the monitoring and evaluation process implemented on HIV/AIDS programmes by the Non- Governmental Organizations (NGOs) in a specific municipality in KwaZulu-Natal province. A quantitative, explorative and descriptive design was used. A self-developed questionnaire was used as data collection instrument. Data was collected from November 2017 to March 2018. Seventeen (17) NGOs and a total of 83 respondents who met the inclusion criteria participated to the study. The results revealed that the NGOs in this specific municipality had some inconsistency in implementing and delivering M&E process on the HIV/AIDS programme. The results of the study indicated that the challenges and issues identified by the respondents affected the way they monitored and evaluated the projects they implemented. It was recommended that through training of staff to acquire skills for designing monitoring and evaluation plan for all projects and development of comprehensive M&E plan document that detailed the programme’s objectives, developed the interventions to achieve these objectives, the NGOs in this specific municipality will be able to improve their current monitoring and evaluation process implementing on HIV/AIDS management programme. The need for communication between programme planners and various funders on how to put in place a structured M&E plan for all the projects to be implemented in future and adequate resources to implement M&E processes and functions were highly recommended.Health StudiesM. P. H