Malignant Catarrhal Fever Induced by Alcelaphine herpesvirus 1 Is Associated with Proliferation of CD8+ T Cells Supporting a Latent Infection

Abstract

Alcelaphine herpesvirus 1 (AlHV-1), carried by wildebeest asymptomatically, causes malignant catarrhal fever (WD-MCF) when cross-species transmitted to a variety of susceptible species of the Artiodactyla order. Experimentally, WD-MCF can be induced in rabbits. The lesions observed are very similar to those described in natural host species. Here, we used the rabbit model and in vivo 5-Bromo-2′-Deoxyuridine (BrdU) incorporation to study WD-MCF pathogenesis. The results obtained can be summarized as follows. (i) AlHV-1 infection induces CD8+ T cell proliferation detectable as early as 15 days post-inoculation. (ii) While the viral load in peripheral blood mononuclear cells remains below the detection level during most of the incubation period, it increases drastically few days before death. At that time, at least 10% of CD8+ cells carry the viral genome; while CD11b+, IgM+ and CD4+ cells do not. (iii) RT-PCR analyses of mononuclear cells isolated from the spleen and the popliteal lymph node of infected rabbits revealed no expression of ORF25 and ORF9, low or no expression of ORF50, and high or no expression of ORF73. Based on these data, we propose a new model for the pathogenesis of WD-MCF. This model relies on proliferation of infected CD8+ cells supporting a predominantly latent infection.

Ex Vivo Bioluminescence Detection of Alcelaphine Herpesvirus 1 Infection during Malignant Catarrhal Fever

“…Phenotyping of mononuclear leukocytes infiltrating lymphoid and nonlymphoid tissues during WD-MCF. We previously observed that WD-MCF is associated with proliferation of CD8 ϩ T cells that become the predominant cell type in lymphoid tissues with the progression of the disease (12). Here, we phenotyped the mononuclear leukocytes infiltrating lymphoid and nonlymphoid tissues during WD-MCF.…”

“…Total DNA was extracted from PBMC or pLN cells using the QIAamp miniprep kit (Qiagen). AlHV-1 genomic DNA copies were quantified using an AlHV-1 ORF3 real-time PCR with normalization on the cellular beta-globin genomic sequence, as described previously (12). Viral and cellular gene-specific primers are listed in Table 1.…”

“…Recently, we demonstrated that WD-MCF in rabbits is associated with a severe proliferation of CD8 ϩ T cells in peripheral blood mononuclear cells (PBMC) and lymphoid organs (12). Moreover, we demonstrated that in PBMC the infection is restricted to CD8 ϩ cells that support predominantly a latent type of infection (12).…”

“…These observations led to the hypothesis that WD-MCF lesions could be due to uninfected cells dysregulated by very few infected cells (1,4,31). Recently, this hypothesis was challenged by the observation that Ն10% of CD8 ϩ T cells in PBMC are infected during WD-MCF in rabbits (12).…”

“…Animals of each group were inoculated intravenously with 4 ϫ 10 6 mock-infected EBL-NLS-Cre cells or with 4 ϫ 10 6 EBL-NLS-Cre cells infected with the wild type (WT) or the 247Nluc ϩ -excised strain, respectively. Infected cells for inoculation were harvested from cultures in which the cytopathic effect (CPE) reached 90% or more and normalized with real-time PCR (12). Rabbits were examined daily for clinical signs and body temperature.…”