Comparison of serological and molecular methods for differentiation between genotype A and genotype B strains of small ruminant lentiviruses

Abstract

Introduction: Small ruminant lentiviruses (SRLV) cause multisystemic, degenerative and chronic disease in sheep and goats.There are five genotypes (A, B, C, D and E), of which A and B are the most widespread. The purpose of this study was to evaluatethe serotyping efficiency of the Eradikit SRLV Genotyping ELISA and the molecular typing efficiency of a newly developed nestedreal-time PCR targeting the long terminal repeat–gag (LTR-gag) region using samples from animals infected with subtypes ofSRLV known to circulate in Poland. Material and Methods: A total of 97 sera samples taken from 34 sheep and 63 goats wereimmunoassayed, and 86 DNA samples from 31 sheep and 55 goats were tested with the PCR. All ruminants were infected withknown SRLV strains of the A1, A5, A12, A13, A16, A17, A18, A23, A24, A27, B1 and B2 subtypes. Results: A total of 69 (80.2%,95% confidence interval 71.6%–88.8%) out of 86 tested samples gave positive results in the PCR. In 17 out of the 86 (19.8%)samples, no proviral DNA of SRLV was detected. The differentiation between MVV (genotype A) and CAEV (genotype B) byPCR matched the predating phylogenetic analysis invariably. No cross-reactivity was observed. On the other hand, the proportionof samples genotyped the same by the older phylogenetic analysis and the Eradikit SRLV Genotyping ELISA was 42.3%. The testwas unable to classify 40.2% of samples, and 17.5% of sera were incorrectly classified. Conclusion: Our results showed thatthe Eradikit SRLV genotyping kit is not a reliable method for predicting SRLV genotype, while the nested real-time PCR basedon the LTR-gag region did prove to be, at least for genotypes A and B.