Cross-species transfer of viruses: implications for the use of viral vectors in biomedical research, gene therapy and as live-virus vaccines

Abstract

All living organisms are continuously exposed to a plethora of viruses. In general, viruses tend to be restricted to the natural host species which they infect. From time to time viruses cross the host-range barrier expanding their host range. However, in very rare cases cross-species transfer is followed by the establishment and persistence of a virus in the new host species, which may result in disease. Recent examples of viruses that have crossed the species barrier from animal reservoirs to humans are hantavirus, haemorrhagic fever viruses, arboviruses, Nipah and Hendra viruses, avian influenza virus (AI), monkeypox virus, and the SARS-associated coronavirus (SARS-CoV). The opportunities for cross-species transfer of mammalian viruses have increased in recent years due to increased contact between humans and animal reservoirs. However, it is difficult to predict when such events will take place since the viral adaptation that is needed to accomplish this is multifactorial and stochastic. Against this background the intensified use of viruses and their genetically modified variants as viral gene transfer vectors for biomedical research, experimental gene therapy and for live-vector vaccines is a cause for concern. This review addresses a number of potential risk factors and their implications for activities with viral vectors from the perspective of cross-species transfer of viruses in nature, with emphasis on the occurrence of host-range mutants resulting from either cell culture or tropism engineering. The issues are raised with the intention to assist in risk assessments for activities with vector viruses.

Genetically Engineered Virus-Vectored Vaccines – Environmental Risk Assessment and Management Challenges

“…The emergence of new viral infections often follows environmental, ecological and technological changes caused by human activities (Louz et al, 2005). Such activities may lead to an increased contact between humans and livestock on one hand, and animal hosts acting as reservoirs of zoonotic viruses on the other hand.…”

“…Against this background the intensified use of viruses and their genetically modified variants as viral gene transfer vectors for biomedical research, experimental gene therapy and as live-vector vaccines is a cause for concern (reviewed by Louz et al, 2005).…”

Animal Cell Cultures: Risk Assessment and Biosafety Recommendations

“…Well-documented cases of viruses that have crossed the species barrier from animal reservoirs to humans include hantavirus (murine reservoir), haemorrhagic fever viruses (Ebola, Marburg) (Peters et al, 1992), avian Influenza virus and SARS-associated coronavirus (SARS-CoV). Although increased growth, mobility and altered food patterns of the human population has been generally recognized as the main cause for the increased incidence of cross-species transfer of mammalian viruses, the occupational risks related to exposure to infected animal tissues or cell cultures should not be underestimated (Louz et al, 2005;Mahy et al, 2000).…”

How Viruses Shape the Tree of Life

“…I suggest that such a relationship deserves much more attention and respect than it has previously received. Persistence is neither a trivial nor easily attained relationship [6]. A persisting virus is not simply a reservoir for acute disease; it is a central and successful life strategy.…”