Bats may host emerging viruses, including coronaviruses (CoV). We conducted an evaluation of CoV in

The primary target of severe acute respiratory syndrome-associated coronavirus (SARS-CoV) is epithelial cells in the respiratory and intestinal tract. The cellular receptor for SARS-CoV, angiotensin-converting enzyme 2 (ACE2), has been shown to be localized on the apical plasma membrane of polarized respiratory epithelial cells and to mediate infection from the apical side of these cells. Here, these results were confirmed and extended by including a colon carcinoma cell line (Caco-2), a lung carcinoma cell line (Calu-3) and Vero E6 cells in our analysis. All three cell types expressed human ACE2 on the apical membrane domain and were infected via this route, as determined with vesicular stomatitis virus pseudotypes containing the S protein of SARS-CoV. In a histological analysis of the respiratory tract, ACE2 was detected in the trachea, main bronchus and alveoli, and occasionally also in the small bronchi. These data will help us to understand the pathogenesis of SARS-CoV infection.Epithelia are a primary barrier to infection by microorganisms entering their host via body cavities such as the respiratory or intestinal tract (reviewed by Compans & Herrler, 2005). Epithelial cells are organized in a polarized fashion that involves the separation of the plasma membrane into an apical and a basolateral domain. The polarity of these cells affects both the early and late stages of infection, i.e. viruses may enter into and exit from a cell either via the apical membrane facing the external environment or via the basolateral membrane directed to the internal milieu of the organism. An important determinant of the virus infection is the presence of suitable receptors on the cell surface that allow attachment to and penetration through the plasma membrane. For viruses entering their host via the respiratory or gastrointestinal route, infection is understood most easily when the virus receptor is expressed on the apical surface.The primary target of the coronavirus associated with severe acute respiratory syndrome (SARS-CoV) is the respiratory tract. In addition to respiratory complications, some patients show intestinal symptoms, indicating that not only the respiratory but also the intestinal epithelium is susceptible to infection. It has been shown recently that the receptor for SARS-CoV, angiotensin-converting enzyme 2 (ACE2; Li et al., 2003;Wang et al., 2004), is localized on and mediates infection through the apical plasma membrane of respiratory epithelial cells (Jia et al., 2005;Sims et al., 2005; Tseng et al., 2005). On the other hand, ACE2 has been reported to be absent from enterocytes of the colon (Hamming et al., 2004), despite active replication of SARS-CoV in this portion of the intestine (Leung et al., 2003).To determine whether epithelial cells of different origin differ in the expression of ACE2, we included in our analysis three cell lines that form a highly polarized epithelial monolayer when grown on microporous filters: (i) Calu-3 (human lung carcinoma cells), (ii) Caco-2 (human colon carcinoma ce...

Bats (Chiroptera) host major human pathogenic viruses including corona-, paramyxo, rhabdo- and filoviruses. We analyzed six different cell lines from either Yinpterochiroptera (including African flying foxes and a rhinolophid bat) or Yangochiroptera (genera Carollia and Tadarida) for susceptibility to infection by different enveloped RNA viruses. None of the cells were sensitive to infection by transmissible gastroenteritis virus (TGEV), a porcine coronavirus, or to infection mediated by the Spike (S) protein of SARS-coronavirus (SARS-CoV) incorporated into pseudotypes based on vesicular stomatitis virus (VSV). The resistance to infection was overcome if cells were transfected to express the respective cellular receptor, porcine aminopeptidase N for TGEV or angiotensin-converting enzyme 2 for SARS-CoV. VSV pseudotypes containing the S proteins of two bat SARS-related CoV (Bg08 and Rp3) were unable to infect any of the six tested bat cell lines. By contrast, viral pseudotypes containing the surface protein GP of Marburg virus from the family Filoviridae infected all six cell lines though at different efficiency. Notably, all cells were sensitive to infection by two paramyxoviruses (Sendai virus and bovine respiratory syncytial virus) and three influenza viruses from different subtypes. These results indicate that bat cells are more resistant to infection by coronaviruses than to infection by paramyxoviruses, filoviruses and influenza viruses. Furthermore, these results show a receptor-dependent restriction of the infection of bat cells by CoV. The implications for the isolation of coronaviruses from bats are discussed.

The surface proteins S of severe acute respiratory syndrome coronavirus (SARS-CoV) and transmissible gastroenteritis virus (TGEV) were compared for their ability to mediate infection of viral pseudotypes based on vesicular stomatitis virus (VSV). The cell tropism of the respective pseudotypes corresponded to the tropism of the viruses from which the S protein was derived.Higher infectivity values were obtained with the SARS-CoV S protein than with the TGEV S protein. Differences were observed with respect to the importance of the cytoplasmic tail and the membrane anchor of the S proteins. In the case of the SARS-CoV S protein, truncation of the cytoplasmic tail resulted in increased infectivity. For the TGEV S protein, the inactivation of an intracellular retention signal in the cytoplasmic tail was required. Exchange of the membrane anchor of the S proteins led to a low infection efficiency. Our results indicate that related glycoproteins may show substantial differences in their ability to mediate pseudotype infection.

In a prospective study of 16,756 consecutive blood donors, we found 54 donors (0.3%) to be anti-hepatitis C virus (HCV)-positive by a first-generation enzyme-linked immunosorbent assay. After retesting, 18 donors were confirmed positive or indeterminate by a second-generation recombinant immunoblot assay. Sixteen of these donors were found positive by a second-generation enzyme-linked immunosorbent assay, and 15 of these were positive by HCV polymerase chain reaction with two primer sets. Nine donors (50%) had a history of drug abuse. In 15 donors found positive by a second-generation enzyme-linked immunoblot assay liver biopsy specimens were taken after at least 6 months' follow-up. In all except one hepatitis C RNA-negative donor, histologic abnormalities were observed, even when alanine aminotransferase (ALAT) levels were continuously normal or only moderately elevated. The abnormalities were less pronounced in these donors (n = 5) than in donors with ALAT levels increased more than twice the upper normal limit (p < 0.05). In conclusion, we found the proportion of previous drug abusers in anti-HCV-positive blood donors to be high. We confirm that the presence of anti-HCV (second generation) usually, and HCV-RNA always, seems to indicate ongoing infection--also when ALAT levels are normal. Our study further suggests that low-activity hepatitis, evaluated by ALAT levels, may indicate a milder disease.