Peter Ott

Human prion diseases: epidemiology and integrated risk assessment.

Human prion diseases are devastating and incurable, but are very rare. Fears that the bovine spongiform encephalopathy epizootic would lead to a large epidemic of its presumed human counterpart, variant Creutzfeldt-Jakob disease (vCJD), have not been realised. Yet a feeling of uncertainty prevails in the general public and in the biomedical world. The lack of data on the prevalence of asymptomatic carriers of vCJD compounds this uncertainty. In addition to this problem, Switzerland is currently faced with another issue of major public concern: a recent rise in the incidence of CJD. Here we examine the plausibility of several scenarios that may account for the increase in CJD incidence, including ascertainment bias due to improved reporting of CJD, iatrogenic transmission, and transmission of a prion zoonosis. In addition, we present the design and current status of a Swiss population-wide study of subclinical vCJD prevalence.

Residual HIV-RNA levels persist for up to 2.5 years in peripheral blood mononuclear cells of patients on potent antiretroviral therapy.

The long-term response of 10 asymptomatic, antiretroviral therapy-naive HIV-1-infected patients to potent combination antiretroviral therapy was characterized by monitoring levels of HIV-1 RNA in plasma, peripheral blood mononuclear cells (PBMC), and lymphoid tissue using highly sensitive HIV-1 RNA assays. Although plasma viral loads were continuously suppressed to levels below 50 HIV-1 RNA copies/ml for up to 2.5 years (60-128 weeks), HIV-1 RNA was still detectable at very low levels (1 to 49 HIV-1 RNA copies/ml) in 25% of the samples. In corresponding PBMC specimens, residual HIV-RNA was detectable in as much as 91% of samples tested (1 to 420 HIV-1 RNA copies/microg total RNA). Similarly, HIV-1 RNA levels in lymphoid tissue also remained detectable at a high frequency (86%). A highly significant correlation was demonstrated between therapy-induced change in PBMC HIV-1 RNA levels and change in plasma HIV-1 RNA levels (r2 = 0.69; p = 0.003). These findings support the concept that measurement of HIV-1 RNA in the easily accessible PBMC compartment is relevant for evaluating the potency of current and future antiretroviral therapies.

Treatment-Induced Decline of Human Immunodeficiency Virus-1 p24 and HIV-1 RNA in Lymphoid Tissue of Patients with Early Human Immunodeficiency Virus-1 Infection

We report detailed quantitative analysis of human immunodeficiency virus-1 (HIV-1) p24 and HIV-1 RNA in tonsil biopsies from 13 patients with early, asymptomatic HIV infection before and during combination antiretroviral therapy. Using fluorescent microscopy in conjunction with reverse transcriptase-polymerase chain reaction of frozen tissue sections, we show that plasma and tissue viral loads decreased by approximately 3 logs during the 1-year treatment period, with good correlation between the HIV-1 p24 and HIV-1 RNA response in tissue. The decrease of tissue viral load was delayed compared to plasma viral load, possibly explained by the observation that the amount of follicular dendritic cell-associated virus correlated best with the area under the curve of plasma HIV-1 RNA throughout the last 12 weeks. Before and during treatment, the relative proportions of HIV-1 on follicular dendritic cells and within mononuclear cells remained constant, suggesting similar decay characteristics in these two lymphoid tissue compartments. However, viral p24 or RNA remained almost always detectable in tissue despite full suppression of HIV-1 RNA in plasma, and increased even after short-term rebounds in plasma viral load. Thus, full and sustained suppression of viral replication was required to efficiently decrease viral load in lymphoid tissue, but complete abolition of residual viral replication was not achieved.

Effects of early antiretroviral treatment on HIV-1 RNA in blood and lymphoid tissue: a randomized trial of double versus triple therapy.

Summary: To assess the effects of early initiation of antiretroviral therapy on cell‐free and cell‐associated viral load in blood and lymphoid tissue, we performed a randomized, open‐label, multicenter trial comparing a double (zidovudine + lamivudine) and triple (zidovudine + lamivudine + ritonavir) drug combination in treatment‐naive, asymptomatic patients with CD4 counts >400 cells/&mgr;l. HIV‐1 RNA was measured in plasma, peripheral blood mononuclear cells, and sequential tonsil or lymph node biopsies (27 patients); the study follow‐up was 2 years. Among 42 randomized patients, the proportion with plasma HIV‐1 RNA <50 copies/ml was 16% and 74% at week 24 (p < .001) in those randomized to double and triple therapy, respectively, necessitating frequent treatment intensification in the double arm. After a rapid decline within 4 weeks in both arms, cell‐associated HIV‐1 RNA decreased further only in those patients with sustained suppression of plasma viral load, but remained almost always detectable at low levels, indicating persisting transcription of viral RNA. CD4 counts increased by 200 to 250 cells/&mgr;l at week 96 in both arms without significant differences (intent‐to‐treat analyses). Thus, even if treatment is initiated early in asymptomatic patients with preserved CD4 counts, three drugs are necessary to achieve sustained decreases of HIV load in blood and lymphoid tissue.

Attenuated and nonproductive viral transcription in the lymphatic tissue of HIV-1-infected patients receiving potent antiretroviral therapy

Human immunodeficiency virus type 1 (HIV-1) RNA that persists in the lymphoid tissue of patients despite treatment with highly active antiretroviral therapy (HAART) may represent extracellular virions or intracellular RNAs residing within HIV-infected cells. To further characterize residual viral transcription, tonsil biopsy specimens from patients receiving long-term HAART, untreated patients, and patients undergoing 2 weeks of structured treatment interruption were analyzed by polymerase chain reaction quantification of virion-encapsidated RNA, intracellular unspliced HIV RNA (HIV UsRNA), multiply spliced HIV RNA encoding tat and rev (HIV MsRNA), and HIV DNA. Tonsil biopsy specimens from viremic patients harbored high amounts of virions, which primarily stemmed from local production, as indicated by a strong correlation of extracellular tonsillar RNA with intracellular HIV-1 nucleic acid levels but not with plasma viremia, and as shown by phylogenetic analysis of clonal env sequences from lymphoid tissue and plasma. In patients receiving HAART, intracellular HIV UsRNA persisted at significantly decreased levels, whereas HIV MsRNA and lymphoid virion levels were depleted. Thus, residual lymphoid HIV-1 RNA in patients receiving HAART indicates attenuated viral transcription in HIV-1-infected cells that lack virion production.

Impact of TNFα, LTα, FcγRII and complement receptor on HIV-1 trapping in lymphoid tissue from HIV-infected patients.

ObjectivesTo investigate HIV trapping mechanisms in patients with acute infection and in asymptomatic individuals prior to and during antiretroviral therapy. To determine the role of complement receptor (CR), Fc gamma receptor II (FcγRII), tumour necrosis factor alpha (TNFα), and lymphotoxin alpha (LTα) expression in HIV trapping efficiency. MethodsLymphoid tissues from three acutely HIV-infected patients and six asymptomatic, chronically HIV-infected patients collected prior to and during antiretroviral therapy were compared with lymphoid tissues from six HIV-seronegative subjects. HIV, TNFα and LTα RNA expression was detected and quantified by fluorescence in situ hybridization. CR, FcγRII and HIV p24 antigen were detected and quantified by fluorescence immunohistochemistry. ResultsThe amount of trapped HIV did not differ significantly between patients with acute HIV infection and asymptomatic individuals, and was independent of the presence of CR or FcγRII expression. However, in patients with acute infection, the amount of trapped virus was correlated inversely with the number of HIV-infected cells (P = 0.0092) and with the size of the light zone (P = 0.037). In these patients, the number of TNFα-expressing cells was correlated inversely with the amount of trapped virus (P = 0.014) and positively correlated with the size of the light zone in germinal centers (P = 0.041). No correlations were observed between TNFα or LTα expression and FcγRII or CR expression. ConclusionThis report provides the first evidence that in humans TNFα is involved in the development of lymphoid follicles, HIV trapping, and, consequently, in early host immune responses. A model is proposed for early events in patients during acute HIV infection.