Study of compartmentalization in the visna clinical form of small ruminant lentivirus infection in sheep

Abstract

BackgroundA central nervous system (CNS) disease outbreak caused by small ruminant lentiviruses (SRLV) has triggered interest in Spain due to the rapid onset of clinical signs and relevant production losses. In a previous study on this outbreak, the role of LTR in tropism was unclear and env encoded sequences, likely involved in tropism, were not investigated. This study aimed to analyze heterogeneity of SRLV Env regions - TM amino terminal and SU V4, C4 and V5 segments - in order to assess virus compartmentalization in CNS.ResultsEight Visna (neurologically) affected sheep of the outbreak were used. Of the 350 clones obtained after PCR amplification, 142 corresponded to CNS samples (spinal cord and choroid plexus) and the remaining to mammary gland, blood cells, bronchoalveolar lavage cells and/or lung. The diversity of the env sequences from CNS was 11.1-16.1% between animals and 0.35-11.6% within each animal, except in one animal presenting two sequence types (30% diversity) in the CNS (one grouping with those of the outbreak), indicative of CNS virus sequence heterogeneity. Outbreak sequences were of genotype A, clustering per animal and compartmentalizing in the animal tissues. No CNS specific signature patterns were found.ConclusionsBayesian approach inferences suggested that proviruses from broncoalveolar lavage cells and peripheral blood mononuclear cells represented the common ancestors (infecting viruses) in the animal and that neuroinvasion in the outbreak involved microevolution after initial infection with an A-type strain. This study demonstrates virus compartmentalization in the CNS and other body tissues in sheep presenting the neurological form of SRLV infection.

Small Ruminant Lentiviruses: Genetic Variability, Tropism and Diagnosis

“…Signature patterns that define organ tropism (disease form) have not been found so far in SRLV infections [116,117]. At the single individual level infected with a lentiviral quasi-species, each particular virus variant may be confined to one particular compartment, organ or tissue within the individual.…”

“…Likely, PBMC become infected after the intake of virus or infected cells/particles through respiratory and/or mammary secretions, including colostrum/milk. Neuroinvasion in the visna outbreak involved microevolution after initial infection with SRLV [117]. Of note, the findings on SRLV diversification, adaptation and/or compartmentalization in the brain may be independent of those observed in lymphoid tissues or other organs, where the virus is exposed to more abundant immune pressures affecting viral replication [134].…”

A review of tuberculosis at the wildlife-livestock-human interface in Zambia

“…Carcasses are declared fit for human consumption once the organs showing gross lesions are removed according to standard regulations [21]. The laboratory procedures (AFB staining, culture and typing, including molecular methods) (see Table 2) [18,22] are only implemented in the Veterinary Research Institutes and the Faculty of Veterinary Science at the University of Zambia in Lusaka. Furthermore, no resources are allocated for BTB testing and control at the national level as it is not considered a disease of national economic importance.…”

Frequência de ovinos soropositivos para lentivírus de pequenos ruminantes no município de Colinas do Tocantins, estado do Tocantins, Brasil

“…Diante desses resultados, foi possível concluir que a frequência de ovinos soropositivos no município é baixa. (Sheffield et al, 1980;Mota, 2008, Ramírez et al, 2012.…”