Persistence and Dissemination of Simian Retrovirus Type 2 DNA in Relation to Viremia, Seroresponse, and Experimental Transmissibility in Macaca fascicularis

Abstract

Endemic simian retrovirus (SRV) infection can cause fatal simian AIDS in

Specific Pathogen-Free Macaques: Definition, History, and Current Production

“…However, animals with high levels of virions in the blood and the accompanying high RNA levels transmit the virus more easily (Wilkinson et al 2003). This may indicate that animals with high DNA levels effectively neutralize the virus through cellular and humoral responses but that DNA is still present in infected cells, yielding little or no viral transmission.…”

“…• all animals in the SPF colony should have at least two semiannual virus tests once housed in stable groups or single housing; • animals should be tested 6 to 8 weeks after any new animals are added to an immediate contact area or after they come in contact with new animals; • animals that may have been exposed to an animal of unknown status should be tested-feces, urine, saliva, and blood can be vectors of transmission and any exposure to these fluids from animals of unknown viral status should be considered a potential exposure; • dams and infants should undergo testing 6 to 8 weeks after birth; and • infants at weaning should be screened before being moved to separate housing and once again 4 to 6 weeks after rehousing (Wilkinson et al 2003).…”

“…Their pleotropic nature leads to very productive acute infections with high levels of virus in bodily fluids, making SRV one of the most problematic viruses for SPF colonies due to horizontal and vertical transmission. However, all SRV infections are not equal in terms of transmissibility: some host animals effectively neutralize the virus with strong antibody responses against the envelope glycoproteins, while a small percentage of animals are continuous viral shedders (Wilkinson et al 2003). In this section we describe how these SRV characteristics are important to the viral testing assays used for routine screening and how the timing of testing and retesting should be designed in consideration of these characteristics.…”

“…Animals that express high levels of virus and proviral DNA are often those with the lowest levels of antibody (Wilkinson et al 2003), and although they appear to be serologically negative they can shed virus in almost all bodily fluids for several years. This condition may be related to immune tolerance because such chronic virus shedders are almost always infants and juveniles born to antibody-positive dams and they appear to be incapable of mounting a robust immune response against SRV (Tsai et al 1990).…”

The Mhc class II DRB genotype of Macaca fascicularis does not influence infection by simian retrovirus type 2

“…Whether infected naturally or experimentally, some animals appear able to clear a primary SRV‐2 infection, while others become persistently infected. Individual animals may mount an antibody response to SRV‐2 and show no detectable viraemia, yet SRV‐2 DNA persists (5). Although a proportion of animals recover from detectable viraemia, others can remain asymptomatic carriers and can transmit virus horizontally, by biting and scratching, and vertically.…”