Detection of Hobi-like infected buffalos with a blocking BDVp80 ELISA kit

FAVARO PAULA; ANDREA PECORA; GASCON; DUS SANTOS, MARÍA J.

Congreso; SWAVLD; 2019

IntroductionHoBi-like viruses are a group of emerging pestiviruses affecting cattle and buffalo. Reliable diagnostic tests are necessary to control and/or eradicate the disease they cause. Seroneutralization (SNT) and ELISAs are the most common techniques for antibody detection. There are some antigenic differences between HoBi-like viruses and BVDV-1 and BVDV-2 strains. The performance of BVDp80 ELISA kits detecting antibodies against this virus is not well known. For this reason, the aim of this study is to evaluate the detectability of a blocking BVD ELISA kit against sera from HoBi-like infected buffalos. Materials and methodsThe study was conducted using 9 sera from HoBi-like naturally infected buffalos. These samples, provided by INTA (Instituto Nacional de Tecnología Agropecuaria, Argentina), had been previously analyzed by SNT and represented a sequence of SNT titer values from 23 to 210 (see Table 1; Andrea Pecora et al, 2017). Samples were analyzed using a blocking BVD p80 ELISA kit (CIVTEST® BOVIS BVD/BD P80) according to the manufacturer?s instructions. The kit expresses results as an Inhibition Percentage (%IN) value, and differentiates between low positive values (%IN 50-80) and high positive values (%IN >80). Samples were evaluated using both protocols of the kit: (i) long protocol; sample incubation o/n at +4ºC and (ii) short protocol; sample incubation 1 hour at +37ºC.Results and discussionQuantitative and qualitative ELISA results for each protocol and sample are shown in Table 1. The kit was able to detect as positives those samples with SNT titers equal or superior to 25 using the long protocol. Buffalo 2 sample, with a 25 SNT titer, was the only sample detected as ?low positive?. The other sample with SNT titer of 25 (Buffalo 6) together with the rest of samples with SNT titers from 26 to 210 were interpreted as ?high positives?. By using the short protocol the kit detected as positive only one of two samples with SNT titer of 25 (Buffalo 6 classified as ?low positive?). Samples with SNT titers from 26 to 28 were also interpreted as ?low positive? and only the samples with SNT titer of 210 were interpreted as ?high positive?.Comparison between SNT and ELISA (%IN) by both protocols is shown in Figure 1. Neither of the protocols detects samples with a SNT titer lower or equal than 24.Conclusion and discussionCIVTEST® BOVIS BVD/BD P80 was able to detect HoBi-like infected buffalo.The kit showed greater detectability by using the long protocol than the short one, as it was able to detect all samples with SNT titers equal or superior than 25. In these conditions, the kit shows the best qualitative performance, indicating that it is suitable to detect HoBi-like infected buffalos.On the other side, the short protocol, despite showing less sensitivity, allows a better semi-quantitative analysis of the samples, since it is able to differentiate between ?low positives? (samples with a SNT titer between 25 and 28) and high positives (samples with SNT titer > 28). So, depending on the type of information we need, we could use one protocol or the other; we would use the long protocol as a screening system, and the short protocol to obtain quantitative information on a positive sample.