Frequent release of low amounts of herpes simplex virus from neurons: results of a mathematical model.

Department of Medicine, University of Washington, Seattle, WA 98195, USA.
Science translational medicine (Impact Factor: 14.41). 11/2009; 1(7):7ra16. DOI: 10.1126/scitranslmed.3000193
Source: PubMed

ABSTRACT Herpes simplex virus-2 (HSV-2) is a sexually transmitted infection that is the leading cause of genital ulcers worldwide. Infection is life long and is characterized by repeated asymptomatic and symptomatic shedding episodes of virus that are initiated when virus is released from neurons into the genital tract. The pattern of HSV-2 release from neurons into the genital tract is poorly understood. We fit a mathematical model of HSV-2 pathogenesis to curves generated from daily quantification of HSV in mucosal swabs performed from patients with herpetic genital ulcers. We used virologic parameters derived from model fitting for stochastic model simulations. These simulations reproduced previously documented estimates for shedding frequency, and herpetic lesion diameter and frequency. The most realistic model output occurred when we assumed minimal amounts of daily neuronal virus introduction. In our simulations, small changes in average total quantity of HSV-2 released from neurons influenced detectable shedding frequency, while changes in frequency of neuronal HSV-2 release had little effect. Frequent HSV-2 shedding episodes in humans are explained by nearly constant release of small numbers of viruses from neurons that terminate in the genital tract.

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    ABSTRACT: Background Herpes simplex virus type 2 (HSV-2) genital lesion recurrence is modulated by psychological factors, but no such link with viral shedding (and thus asymptomatic transmission) has been observed in humans. Purpose The moderating effects of average psychological distress, emotional stability, and emotion regulation on HSV-2 recurrence were tested. Methods Nineteen HSV-2 seropositive women were followed over 22 weeks. Daily measures of HSV-2 recurrence and psychological distress were collected. HSV-2 lesions and viral shedding were modeled as linear oscillator systems, with psychological distress moderating the periodicity of each process. Results High levels of distress, more labile moods, and less ability to regulate emotional states were associated with fewer days elapsed between the onset of lesion episodes. Viral shedding showed the same pattern. Conclusions Results are consistent with research indicating that psychological distress suppresses immune system functioning, and provide new evidence that genital HSV-2 viral shedding is related to, and regulated by, psychological distress.
    Annals of Behavioral Medicine 10/2014; 49(2). DOI:10.1007/s12160-014-9640-9 · 4.20 Impact Factor
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    ABSTRACT: Herpes simplex virus-2 (HSV-2) is a chronic reactivating infection that leads to recurrent shedding episodes in the genital tract. A minority of episodes are prolonged, and associated with development of painful ulcers. However, currently, available tools poorly predict viral trajectories and timing of reactivations in infected individuals. We employed principal components analysis (PCA) and singular value decomposition (SVD) to interpret HSV-2 genital tract shedding time series data, as well as simulation output from a stochastic spatial mathematical model. Empirical and model-derived, time-series data gathered over >30 days consists of multiple complex episodes that could not be reduced to a manageable number of descriptive features with PCA and SVD. However, single HSV-2 shedding episodes, even those with prolonged duration and complex morphologies consisting of multiple erratic peaks, were consistently described using a maximum of four dominant features. Modeled and clinical episodes had equivalent distributions of dominant features, implying similar dynamics in real and simulated episodes. We applied linear discriminant analysis (LDA) to simulation output and identified that local immune cell density at the viral reactivation site had a predictive effect on episode duration, though longer term shedding suggested chaotic dynamics and could not be predicted based on spatial patterns of immune cell density. These findings suggest that HSV-2 shedding patterns within an individual are impossible to predict over weeks or months, and that even highly complex single HSV-2 episodes can only be partially predicted based on spatial distribution of immune cell density.
    PLoS Computational Biology 11/2014; 10(11):e1003922. DOI:10.1371/journal.pcbi.1003922 · 4.83 Impact Factor
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    ABSTRACT: Despite its importance in modulating HSV-2 pathogenesis, the nature of tissue-resident immune memory to HSV-2 is not completely understood. We used genital HSV-2 infection of guinea pigs to assess the type and location of HSV-specific memory cells at peripheral sites of HSV-2 infection. HSV-specific antibody-secreting cells were readily detected in the spleen, bone marrow, vagina/cervix, lumbosacral sensory ganglia, and spinal cord of previously-infected animals. Memory B cells were detected primarily in the spleen and to a lesser extent in bone marrow but not in the genital tract or neural tissues suggesting that the HSV-specific antibody-secreting cells present at peripheral sites of HSV-2 infection represented persisting populations of plasma cells. The antibody produced by these cells isolated from neural tissues of infected animals was functionally relevant and included antibodies specific for HSV-2 glycoproteins and HSV-2 neutralizing antibodies. A vigorous IFN-γ-secreting T cell response developed in the spleen as well as the sites of HSV-2 infection in the genital tract, lumbosacral ganglia and spinal cord following acute HSV-2 infection. Additionally, populations of HSV-specific tissue-resident memory T cells were maintained at these sites and were readily detected up to 150 days post HSV-2 infection. Unlike the persisting plasma cells, HSV-specific memory T cells were also detected in uterine tissue and cervicothoracic region of the spinal cord and at low levels in the cervicothoracic ganglia. Both HSV-specific CD4+ and CD8+ resident memory cell subsets were maintained long-term in the genital tract and sensory ganglia/spinal cord following HSV-2 infection. Together these data demonstrate the long-term maintenance of both humoral and cellular arms of the adaptive immune response at the sites of HSV-2 latency and virus shedding and highlight the utility of the guinea pig infection model to investigate tissue-resident memory in the setting of HSV-2 latency and spontaneous reactivation.
    PLoS ONE 12/2014; 9(12):e114652. DOI:10.1371/journal.pone.0114652 · 3.53 Impact Factor

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