Tissue and Cell Tropism of African Horse Sickness Virus Demonstrated by Immunoperoxidase Labeling in Natural and Experimental Infection in Horses in South Africa

Abstract

Tissues from 196 experimental and confirmed natural cases of African horse sickness (all 9 serotypes) were examined with a standardized and validated immunohistochemical assay for detection of the causative virus. The study confirmed that heart and lung are the main target tissues for African horse sickness virus (across all serotypes), followed closely by spleen. It also indicated that microvascular endothelial cells and monocyte-macrophages are the main target cells for virus replication. The importance of monocytes as target cells was emphasized, with relatively few tissue macrophages containing antigen in the lung and spleen, respectively. The results were largely in agreement with those of previous studies, but the large number of cases examined permitted more precise description of the location and distribution of antigen in different tissues. Comparison with descriptions of tissue and cell tropism of other orbiviruses indicated similarity with African horse sickness. Immunohistochemistry was shown to be a useful and consistent technique for demonstrating target cells, but the difficulty of identifying cell types-in particular, different types of monocyte-macrophages-is a limitation.

Pathology of fatal lineage 1 and 2 West Nile virus infections in horses in South Africa

“…Lineage 2 WNV has been reported in South Africa since 2007-2008 as a cause of severe, emerging neurological disease in horses (Venter et al 2009) and humans (Zaayman & Venter 2012). Since 2004, it has been reported in Europe as a cause of severe illness or death in birds (Bakonyi et al 2006;Danis et al 2010), horses (Kutasi et al 2009) and humans (Danis et al 2010;Papa, Danis, Baka, Bakas, Douglas, Lytras et al 2010;Papa, Perperidou, Tzouli & Castilleti 2010;Papa, Bakonyi, Xanthopoulou, Vasquez, Tenorio & Nowotny 2011;Papa, Danis, Tsergouli, Tsioka & Gavana 2011;Papa, Xanthopoulou, Gewehr & Mourelatos 2011;Platonov et al 2008). Recent outbreaks of lineage 2 WNV in Romania in 2010 (Sirbu et al 2011) and lineage 1 WNV in the United States of America (USA) in 2012 (Chung et al 2013) have shown the incidence of neuroinvasive disease in humans to have risen to more than 50% of clinical cases.…”

Characterising Non-Structural Protein NS4 of African Horse Sickness Virus

“…In naturally infected horses, it was previously shown that sections of heart, lung and spleen consistently label positive for AHSV proteins across all serotypes [ 36 , 37 ]. Here, tissues from confirmed (virus isolation- and virus neutralisation or RT-PCR-positive) AHSV-4 (probably Clade I, but not confirmed with sequencing) and AHSV-7 (Clade II) cases (naturally and experimentally infected horses, respectively, that presented for necropsy) were selected for immunoperoxidase labelling to determine the location of NS4 within the mammalian host of AHSV ( Fig 5 ).…”

“…These horses had been slaughtered according to internationally prescribed humane methods for the slaughter of horses for human consumption. Ethical approval for the use of the AHSV-4 infected and uninfected horse material was obtained from the University of Pretoria, Faculty of Veterinary Science, Animal Use and Care Committee, with Protocol and Ethical Approval number V049/04, and other work based on these samples has been published previously [ 36 , 37 ]. Ethical approval for the use of the AHSV-7 infected material was obtained from the Deltamune Ethics Committee, Project number 201308–27, Ethics Committee reference CR-13-119.…”

African horse sickness virus infects BSR cells through macropinocytosis

“…The mechanism by which AHSV-4 triggers macropinocytosis in BSR cells is currently unknown, but likely involves interaction between its surface protein (VP2) and cellular receptors. Considering that AHSV infects and replicates in a wide range of cells (Meiring et al, 2009;Clift and Penrith, 2010;Stassen et al, 2012), it is plausible that its entry into cells is mediated by the binding of VP2…”