Different routes and doses influence protection in pigs immunised with the naturally attenuated African swine fever virus isolate OURT88/3

Abstract

This study compares different combinations of doses and routes of immunisation of pigs with low virulent African swine fever virus (ASFV) genotype I isolate OURT88/3, including the intramuscular and intranasal route, the latter not previously tested. Intranasal immunisations with low and moderate doses (103 and 104 TCID50) of OURT88/3 provided complete protection (100%) against challenge with virulent genotype I OURT88/1 isolate. Only mild and transient clinical reactions were observed in protected pigs. Transient moderate virus genome levels were detected in blood samples after challenge that decreased, but persisted until the end of the experiment in some animals. In contrast, pigs immunised intramuscularly with low and moderate doses (103 and 104 TCID50) displayed lower percentages of protection (50–66%), and low or undetectable levels of virus genome were detected in blood samples throughout the study. In addition, clinical courses observed in protected pigs were asymptomatic. In pigs that were not protected and developed acute ASF, an exacerbated increase of IL-10 sometimes accompanied by an increase of IFNγ was observed before euthanasia. These results showed that factors including delivery route and dose determine the outcome of immunisation with the naturally attenuated isolate OURT88/3.

Attenuated and non‐haemadsorbing (non‐HAD) genotypeIIAfrican swine fever virus (ASFV) isolated in Europe, Latvia 2017

“…In Lv17/WB/Rie1 isolate, the nonfunctional CD2‐like protein is responsible of its non‐HAD capacity, a feature shared with other naturally attenuated ASFV strains, such as NH/P68 and OURT88/3. In agreement with previous findings using the same mentioned non‐HAD‐ASFVs (Boinas et al., ; Gallardo et al., ; Leitão et al., ; Sánchez‐Cordón et al., ), pigs intramuscularly infected with Lv/17/WB/Rie1 ASFV developed nonspecific clinical signs, and in some cases remained asymptomatic, showing intermittent and weak viremia and a high antibody response. Furthermore, 2 months following the primary infection with Lv17/WB/Rie1, the two pigs exposed were fully resistant to challenge with a virulent HAD Latvian ASFV.…”

“…Furthermore, 2 months following the primary infection with Lv17/WB/Rie1, the two pigs exposed were fully resistant to challenge with a virulent HAD Latvian ASFV. Similarly, protection induced by oronasal and intramuscular immunizations of pigs with the non-HAD low virulence field ASFV genotype I isolates have been previously described (Boinas et al, 2004;Leitão et al, 2001;Sánchez-Cordón et al, 2017). Even though the number of animals was quite small, these results suggest the potential use of Lv17/WB/Rie1 as a target for live attenu-…”

Epidemiological analyses of African swine fever in the European Union (November 2017 until November 2018)

“…Other drivers include the mating season, when sexual contacts take place and aggressive interactions among males may become more frequent, too. In most of Europe, the main wild boar mating season takes place from October to January (Rosell, 2012), roughly coinciding with the main hunting season. Although the farrowing season may peak in spring, births (and hence mating) can take place in any time of the year (Albrycht et al, 2016), particularly if supplementary feeding is provided.…”

Protective Properties of Attenuated Strains of African Swine Fever Virus Belonging to Seroimmunotypes I–VIII

“…Immunopathological conditions involving hypergammaglobulinemia and systemic immune activation were observed in pigs inoculated with other moderately virulent ASFV isolates [37,38]. Less pronounced clinical reactions, including fever and joint swelling, were described for ASFV strain OURT88/3 [7,39].…”