Even though ferrets are one of the principal animal models for influenza pathogenesis, the lack of suitable immunological reagents has so far limited their use in host response studies. Using recently established real-time PCR assays for a panel of ferret cytokines, we analyzed the local ferret immune response to human influenza isolates of the H1N1 and H3N2 subtypes that varied in their virulence. We observed that the severity of clinical signs correlated with gross- and histopathological changes in the lungs and was subtype-independent. Strains causing a mild disease were associated with a strong and rapid innate response and upregulation of IL-8, while severe infections were characterized by a lesser induction of type I and II interferons and strong IL-6 upregulation. These findings suggest that more virulent strains may interfere more efficiently with the host response at early disease stages.

The multiple sclerosis-associated retrovirus (MSRV), originally identified in cell cultures from patients with multiple sclerosis (MS), is closely related to the human endogenous retrovirus family W (HERV-W). Recently, HERV-W gag and env protein expression was demonstrated in MS lesions in situ. Here, the authors show that HERV-W gag and env proteins are induced by herpes simplex virus type 1 (HSV-1) in neuronal and brain endothelial cells in vitro. The transactivation of HERV-W proteins by HSV-1 could enhance their potential oligodendrotoxic and immunopathogenic effects, representing a mechanism by which HSV-1, and possibly also other herpesviruses associated with MS, may be linked to the pathogenesis of this disease.

Gamma interferon (IFN-␥

The type I interferon (IFN) response represents one of the first lines of defense against influenza virus infections. In this study, we assessed the protective potential of exogenous IFN-␣ against seasonal and highly pathogenic influenza viruses in ferrets. Intranasal treatment with IFN-␣ several hours before infection with the H1N1 influenza A virus strain A/USSR/90/77 reduced viral titers in nasal washes at least 100-fold compared to mock-treated controls. IFN-treated animals developed only mild and transient respiratory symptoms, and the characteristic fever peak seen in mock-treated ferrets 2 days after infection was not observed. Repeated application of IFN-␣ substantially increased the protective effect of the cytokine treatment. IFN-␣ did not increase survival after infection with the highly pathogenic H5N1 avian influenza A virus strain A/Vietnam/ 1203/2004. However, viral titers in nasal washes were significantly reduced at days 1 and 3 postinfection. Our study shows that intranasal application of IFN-␣ can protect ferrets from seasonal influenza viruses, which replicate mainly in the upper respiratory tract, but not from highly pathogenic influenza viruses, which also disseminate to the lung. Based on these results, a more intensive evaluation of IFN-␣ as an emergency drug against pandemic influenza A is warranted.

No abstract

Measles virus (MV) infects endothelial cells of the skin, the brain and other organs during acute or persistent infections. Endothelial cells are supposed to play an important role in virus spread from the blood stream to surrounding tissues. CD46 and CD150 (signalling lymphocytic activation molecule, SLAM) have been described as cellular receptors for certain MV strains. We found that human umbilical vein and brain microvascular endothelial cells (HUVECs and HBMECs) were CD46-positive, but did not express SLAM. Wild-type MV strains, which do not use CD46 as a receptor at the surface of transfected Chinese hamster ovary cells, infected HUVECs and HBMECs to varying extents in a strain-dependent way. This infection was not inhibited by antibodies to CD46. These data suggest the presence of an additional unidentified receptor for MV uptake and spread in human endothelial cells. INTRODUCTIONAfter acute infection of the upper respiratory tract, measles virus (MV) is rapidly transported to draining lymph nodes forming giant cells in the reticulo-endothelial system. MV then establishes a systemic infection and spreads to different organs, including the skin. In these organs, virus replicates primarily in endothelial cells (ECs), epithelial cells and monocytes/macrophages (Griffin & Bellini, 1996). ECs of dermal capillaries (Kimura et al., 1975) and small vessels throughout the body show clear evidence of MV infection. This appears to play a central role in pathogenesis, leading to changes in the skin, conjunctivae, mucous membranes and the brain (Cosby & Brankin, 1995), accompanied by vascular dilatation, increased vascular permeability, mononuclear cell infiltration and infection of surrounding tissues. In rare cases, the EC infection may extend to a severe haemorrhagic infection with confluent haemorrhagic skin eruptions and intravascular coagulopathy, so-called haemorrhagic or black measles. Brain ECs and capillary endothelium of lymph nodes and the thymus have been found to be infected in fatal cases of acute measles (Esolen et al., 1995; Moench et al., 1988). In subacute sclerosing panencephalitis (SSPE) patients, brain ECs appear to be infected in addition to various neural cells (Allen et al., 1996;Isaacson et al., 1996;Kirk et al., 1991).Following the identification of CD46 as a receptor for MV vaccine and laboratory strains (Dörig et al., 1993;Naniche et al., 1993a), evidence has accumulated that many wildtype isolates do not use CD46 as a receptor. Recently, the signalling lymphocytic activation molecule (SLAM, CD150) has been identified as a common receptor interacting with MV vaccine as well as wild-type strains (Erlenhoefer et al., 2001(Erlenhoefer et al., , 2002Hsu et al., 2001; Ono et al., 2001a, b;Tatsuo et al., 2000). SLAM is expressed on human B cell lines, primary activated B and T cells, memory cells and activated monocytes and monocyte-derived dendritic cells (Cocks et al., 1995;Minagawa et al., 2001;Ohgimoto et al., 2001;Polacino et al., 1996;Punnonen et al., 1997), and its usage as a receptor c...

Cotton rats (Sigmodon hispidus) replicate measles virus (MV) after intranasal infection in the respiratory tract and lymphoid tissue. We have cloned the cotton rat signaling lymphocytic activation molecule (CD150, SLAM) in order to investigate its role as a potential receptor for MV. Cotton rat CD150 displays 58% and 78% amino acid homology with human and mouse CD150, respectively. By staining with a newly generated cotton rat CD150 specific monoclonal antibody expression of CD150 was confirmed in cotton rat lymphoid cells and in tissues with a pattern of expression similar to mouse and humans. Previously, binding of MV hemagglutinin has been shown to be dependent on amino acids 60, 61 and 63 in the V region of CD150. The human molecule contains isoleucine, histidine and valine at these positions and binds to MV-H whereas the mouse molecule contains valine, arginine and leucine and does not function as a receptor for MV. In the cotton rat molecule, amino acids 61 and 63 are identical with the mouse molecule and amino acid 60 with the human molecule. After transfection with cotton rat CD150 HEK 293 T cells became susceptible to infection with single cycle VSV pseudotype virus expressing wild type MV glycoproteins and with a MV wildtype virus. After infection, cells expressing cotton rat CD150 replicated virus to lower levels than cells expressing the human molecule and formed smaller plaques. These data might explain why the cotton rat is a semipermissive model for measles virus infection.