Cultivation and Serological Characterization of a Human Theiler's-Like Cardiovirus Associated with Diarrheal Disease

Abstract

Cardioviruses (e.g., Theiler's murine encephalomyelitis virus [TMEV]) are members of the Picornaviridae family that cause myocarditis and encephalitis in rodents. Recently, several studies have identified human cardioviruses, including Saffold virus (SAFV) and a related virus named human TMEV-like cardiovirus (HTCV). At least eight cardiovirus genotypes are now recognized, with SAFV and most strains of HTCV belonging to genotypes 1 and 2, respectively; genotype 2 strains are the most common in the population. Although a genotype 3 cardiovirus has recently been cultured (SAFV-3), the genotype 1 and 2 cardioviruses have been difficult to propagate in vitro, hindering efforts to understand their seroprevalence and pathogenicity. Here we present the isolation and characterization of a genotype 2 human cardiovirus (HTCV-UC6). Notably, successful cultivation of HTCV-UC6 from stool required the addition of cytokine-blocking antibodies to interrupt downstream antiviral pathways. Unlike SAFV-3, HTCV-UC6 exhibited slow replication kinetics and demonstrated only a moderate cytopathic effect. Serologic assays revealed that 91% of U.S. adults carry antibodies to the genotype 2 cardioviruses, of which 80% generate neutralizing antibodies, in agreement with previous data showing that cardiovirus infection is widespread in humans. We also demonstrate an acute cardiovirus seroconversion event in a child with diarrhea and vomiting, thus reporting for the first time evidence linking cardiovirus infection to diarrheal disease in humans.

Metagenomic sequencing for virus identification in a public-health setting

“…In several cases, SAFV has been detected in addition to other viruses known to cause gastroenteritis, thus hindering interpretation regarding SAFV infection and observed pathology (Chiu et al, 2008;Drexler et al, 2008;Ren et al, 2009). SAFV-2 has recently been linked to infection in a child with diarrhoea and vomiting, based on an acute seroconversion event supporting an association between this virus and diarrhoeal disease (Chiu et al, 2010). Although SAFV-3 was the only viral agent identified in five of 15 of the unexplained cellculture samples in this study, it cannot be concluded that these viruses were causing illness or clinical symptoms.…”

“…2). In the USA, it has been shown that 91 % of adults carry antibodies against SAFV-2, with 80 % of studied individuals generating neutralizing antibodies against this genotype (Chiu et al, 2010).…”

Isolation of Saffold Virus Type 2 from Children with Acute Respiratory Infections by Using the RD-18S-Niigata Cell Line

“…In general, whereas SAFV-3 has shown efficient growth and a clear cytopathic effect (CPE) in several cell lines, SAFV-2 strains are difficult to propagate and the detection of SAFV-2 has been mainly performed using molecular methods (5,9,12,(18)(19)(20). Chiu et al succeeded in isolating the SAFV-2 HTCV-UC6 strain only after the addition of monoclonal anti-cytokine antibodies (20).…”

“…Chiu et al succeeded in isolating the SAFV-2 HTCV-UC6 strain only after the addition of monoclonal anti-cytokine antibodies (20). Although they analyzed viral tropism in vitro by using the HTCV-UC6 strain and 11 cell lines, they observed that viral replication was quite limited (20).…”

“…Chiu et al succeeded in isolating the SAFV-2 HTCV-UC6 strain only after the addition of monoclonal anti-cytokine antibodies (20). Although they analyzed viral tropism in vitro by using the HTCV-UC6 strain and 11 cell lines, they observed that viral replication was quite limited (20). Hertzler et al reported the successful adaptation of SAFV-2 to a limited number of cell lines, such as HeLa and U118MG, after repeated passaging in 14 human, non-human, and rodent cell lines (19).…”