Abstract
Infants with severe primary combined immunodeficiency (SCID) and children post-allogeneic hematopoietic stem cell transplantation (HSCT) are extremely susceptible to unusual infections. The lack of generic tools to detect disease-causing viruses among more than 200 potential human viral pathogens represents a major challenge to clinicians and virologists. We investigated retrospectively the causes of a fatal disseminated viral infection with meningoencephalitis in an infant with gamma C-SCID and of chronic gastroenteritis in 2 other infants admitted for HSCT during the same time period. Analysis was undertaken by combining cell culture, electron microscopy and sequence-independent single primer amplification (SISPA) techniques. Caco-2 cells inoculated with fecal samples developed a cytopathic effect and non-enveloped viral particles in infected cells were detected by electron microscopy. SISPA led to the identification of astrovirus as the pathogen. Both sequencing of the capsid gene and the pattern of infection suggested nosocomial transmission from a chronically excreting index case to 2 other patients leading to fatal infection in 1 and to transient disease in the others. Virus-specific, real-time reverse transcription polymerase chain reaction was then performed on different stored samples to assess the extent of infection. Infection was associated with viremia in 2 cases and contributed to death in 1. At autopsy, viral RNA was detected in the brain and different other organs, while immunochemistry confirmed infection of gastrointestinal tissues. This report illustrates the usefulness of the combined use of classical virology procedures and modern molecular tools for the diagnosis of unexpected infections. It illustrates that astrovirus has the potential to cause severe disseminated lethal infection in highly immunocompromised pediatric patients.
Highlights
Infants with severe combined immunodeficiency (SCID) and children after allogeneic hematopoietic stem cell transplantation (HSCT) are exceptionally susceptible to viral infections and viral reactivations
Identification of the infecting virus Three infants suffering from severe congenital immunodeficiency were admitted for allogeneic HSCT at the University of Zurich Children’s Hospital during the same time period (Figure 1)
Application of the sequence-independent single primer amplification (SISPA) method allowed the identification of an astrovirus. 5 of 13 clones sequenced thanks to this method represented astroviral sequences (1 clone covered nt 2540 to 2948 of the reference astrovirus 4 genome [GenBank DQ344027]); the second, nt 3140 to 3795; and the 3 remaining clones overlapped over nt 4101 to 5094
Summary
Infants with severe combined immunodeficiency (SCID) and children after allogeneic hematopoietic stem cell transplantation (HSCT) are exceptionally susceptible to viral infections and viral reactivations. The lack of functional cytotoxic T- and NK-cells prior to and for a certain time after HSCT opens the door to infections by unexpected pathogens either community acquired or nosocomial. Viral infections, including those that commonly cause self-limited childhood diseases, can lead to protracted infections with chronic viral shedding, and to disseminated disease with infection of organs rarely affected in immunocompetent hosts [1]. Generic molecular tools, such as microarrays [3], ultra-deep sequencing [4], sequence-independent single primer amplification (SISPA) [5], virus discovery based on cDNA-amplified fragment length polymorphism [6], or any other similar procedures, offer potentially attractive alternatives the sensitivity is limited
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