THE HAEMADSORPTION AT AFRICAN SWINE FEVER (review)

Abstract

A b s t r a c tThe capability of causing haemadsorption at African swine fever (ASF) virus (ASFV) reproduction in swine bone marrow cell cultures, leukocytes or continuous cells in the presence of swine erythrocytes is characteristic of the majority of the virus isolates (W.A. Malmquist, D. Hay, 1960). This trait is used for ASF diagnosis based on autohaemadsorption in porcine blood, the virus titration in cell culture, and selection of its attenuated variants in vitro (A.D. Sereda et al., 2014). The haemadsorption inhibition assay (HIA) in tandem with the bioassay using the disease-resistant pigs is applied for seroimmunotype-based classification of ASFV isolates (N.I. Mitin et al., 1985). The heterogeneity of an ASFV population for quantitative haemadsorption characteristic (like «dense», «moderate» or «loose») is a phenotypic trait of ASFV isolates, strains and/or variants (V. Makarov et al., 2016). Also, the proportion of the circumference of red blood cells as observed at their contact with infected macrophages serves as another quantifiable feature of haemadsorption. Some quantitative differences in HIA activity levels of swine blood sera are determined in the assays carried out using virulent reference variants and their attenuated derivatives, and the obtained results require some interpretation. The loss of ability to induce haemadsorption is not critical for ASFV reproduction and often accompanied by a decrease in the pathogen virulence levels. Hence, as a rule, attenuated ASFV variants are prepared through a selection by limiting dilution from populations of virulent isolates of the virus clones that are characterized by a reduced potential to induce haemadsorption (D.V. Kolbasov et al., 2014). In the course of the virus reproduction, haemadsorption precedes the exocytosis. Virions do not play a significant role in the mechanism of haemadsorption, nevertheless, their interaction with erythrocyte membranes promotes the virus dissemination throughout the swine organism and more effective introduction into the gut cells of ticks (L.K. Dixon et al., 2004). ASFV haemadsorbing potentiality is determined by highly glycosylated transmembrane protein CD2v (J.M. Rodríguez et al., 1993). Probably, nonhaemadsorbing avirulent isolates emerge as a result of some shift of the open reading frames for EP402R and EP153R encoding the CD2v and lectin-like proteins, respectively (D. A. Chapman et al., 2008). An assumption is made that the haemadsorption phenomenon is due to an interaction between carbohydrate residues of glycoproteins of ASFV oligosaccharides and lectin-like receptors of swine red blood cells.

African swine fever virus serotype-specific proteins are significant protective antigens for African swine fever

“…Further, the fact that the solid protection afforded by immunization with the Congo-attenuated (KK-262) strain, an SG2 virus, was lost when the Congo CD2v/C-type lectin genes were replaced with those from a virulent France strain (F32), an SG4 virus, directly supports the emerging concept that ASF protective immunity is HAI serotype-specific (Balyshev et al, 1995;Sereda & Balyshev, 2011;Sereda et al, 1992;Vishnjakov et al, 1991;Malogolovkin et al, unpublished data).…”

“…Eight ASFV serogroups (SGs) have been identified, although more are likely to exist (Balyshev et al, 1995(Balyshev et al, , 2010Malogolovkin et al, 2015a;Sereda & Balyshev, 2011;Sereda et al, 1992;Vishnjakov et al, 1995). Notably and of particular significance for vaccine development, ASF protective immunity may be serotype-specific, as viruses of homologous HAI SG appear to cross-protect against one another while heterologous viruses do not (Balyshev et al, 1995;Sereda & Balyshev, 2011;Sereda et al, 1992;Vishnjakov et al, 1991;Malogolovkin A., Sereda A., Balyeshev V. and Kolbasov D., unpublished data). Recently, we have shown that two ASFV-encoded proteins, CD2v (EP402R) and/or C-type lectin (EP153R), are necessary and sufficient for mediating HAI serological specificity (Malogolovkin et al, 2015b).…”

Genetic and antigenic diversity of African swine fever virus

“…Eight ASFV serogroups (SG) were defined and thoroughly characterized; however, more SG may exist. Additional parameters such as HA density (number of erythrocytes per infected cells) and erythrocyte contact maps were used to refine ASFV isolate classification (Makarov et al, 2016;Sereda et al, 1994). The HAI based assay was used for ASFV strains selection and screening for development a potential liveattenuated vaccine candidates (Sereda et al, 1992;Sereda and Balyshev, 2011).…”

“…Additional parameters such as HA density (number of erythrocytes per infected cells) and erythrocyte contact maps were used to refine ASFV isolate classification (Makarov et al, 2016;Sereda et al, 1994). The HAI based assay was used for ASFV strains selection and screening for development a potential liveattenuated vaccine candidates (Sereda et al, 1992;Sereda and Balyshev, 2011). Surprisingly, the key significance of HAI classification was discovered even earlier again by Malmquist W.A., who used the HAI assay for ASFV grouping (homologous vs heterologous).…”

IMMUNOBIOLOGICAL AND MOLECULAR GENETIC PROPERTIES OF NON-HEMADSORBING AFRICAN SWINE FEVER VIRUS STRAINS (review)

“…Как правило, у природных хозяев, включая клещей, вирус АЧС вызывает субклиническую хроническую или инаппарантную формы инфекции (10,11). Изоляты и штаммы вируса АЧС различаются по патогенным, антигенным, гемадсорбирующим, генетическим свойствам (12)(13)(14). В частности, на основе 3´-концевых последовательностей гена B646L, кодирующего основной капсидный белок p72, в Африке идентифицировано 24 генотипа вируса АЧС (15)(16)(17).…”