Evaluation of an alternative method for determination of Protective Dose50 of Classical swine fever vaccines.

Classical Swine Fever (CSF) is still one of the most economically important viral diseases of pigs. The disease is controlled by vaccination in the endemic countries. Hence, availability or supply of efficacious and potent vaccine in the field settings is of utmost importance. Currently, as per requirement of any Pharmacopoea, a CSF vaccine must contain 100 PD50/dose which is determined by vaccinating pigs at 1/40th and 1/160th dilution of each dose followed by virulent challenge at 28 days post vaccination (dpv). Here, the control and the unprotected groups succumb to disease and need to be euthanized. Moreover, such challenge experiments are not feasible for each batch of the vaccine. In this communication, an alternate method of PD50 dose calculation of live-attenuated CSF vaccines by measuring Serum Neutralizing Titre i.e Fluorescent Antibody Virus Neutralization (FAVN) titre of the vaccinated pigs at 28 dpv was established. This alternative method do not require the vaccinated pigs to be challenged. Serum samples, generated out of QC testing of eight batches of CSF vaccines in the laboratory, were tested and found that pigs having FAVN titre ≥10 were protected against challenge. Initially this test was optimized in serum samples of 12 animals and then validated with another 56 serum samples. It was found that the alternate method is 100% correlating with the challenge experiment. Thus, based on FAVN titre of the vaccinated animal serum, it can be predicted whether the pigs would or would not come through the challenge infection. Using the predicted status (protected/succumbed), PD50 can be calculated by applying Reed and Muench formula, hence alternate method can be used as routine QC test for potency of CSF vaccines. The newly developed assay was specific since no signal was observed in controls.

Ongoing Assessment of the Molecular Evolution of Peste Des Petits Ruminants Virus Continues to Question Viral Origins.

Understanding the evolution of viral pathogens is critical to being able to define how viruses emerge within different landscapes. Host susceptibility, which is spread between different species and is a contributing factor to the subsequent epidemiology of a disease, is defined by virus detection and subsequent characterization. Peste des petits ruminants virus is a plague of small ruminant species that is a considerable burden to the development of sustainable agriculture across Africa and much of Asia. The virus has also had a significant impact on populations of endangered species in recent years, highlighting its significance as a pathogen of high concern across different regions of the globe. Here, we have re-evaluated the molecular evolution of this virus using novel genetic data to try and further resolve the molecular epidemiology of this disease. Viral isolates are genetically characterized into four lineages (I-IV), and the historic origin of these lineages is of considerable interest to the molecular evolution of the virus. Our re-evaluation of viral emergence using novel genome sequences has demonstrated that lineages I, II and IV likely originated in West Africa, in Senegal (I) and Nigeria (II and IV). Lineage III sequences predicted emergence in either East Africa (Ethiopia) or in the Arabian Peninsula (Oman and/or the United Arab Emirates), with a paucity of data precluding a more refined interpretation. Continual refinements of evolutionary emergence, following the generation of new data, is key to both understanding viral evolution from a historic perspective and informing on the ongoing genetic emergence of this virus.

Stability of live attenuated classical swine fever cell culture vaccine virus in liquid form for developing an oral vaccine.

Classical swine fever (CSF) is an important viral disease of pigs and controlled by vaccination. Unorganised backyard and wild pigs are difficult to vaccinate by needle vaccination. Here we formulated liquid vaccines using an Indian CSF cell culture vaccine virus and four stabilisers and evaluated their stability at 4 °C, 25 °C and 37 °C up to 24 h for use as oral vaccine. The stabilisers were Lactalbumin hydrolysate-Trehalose, Lactalbumin hydrolysate-Trehalose-Gelatin, Lactalbumin hydrolysate-Lactose-Sucrose and Lactalbumin hydrolysate-Sucrose. The liquid vaccines, with or without stabilisers, were stable at 4 °C up to 24 h, whereas, a drop of one log10 titre was observed at 25 °C during the same period. At 37 °C, the virus titre diminished by only one log10 with the Lactalbumin hydrolysate-Trehalose (LT) stabiliser up to 24 h compared to two log10 losses in virus titre with other stabilisers and virus control. We therefore conclude that for developing a CSF oral vaccine, the vaccine virus in liquid form can be used directly during the winter, whereas for developing the oral vaccine for summer, the LT stabiliser would provide maximum stability to the virus to withstand the warm temperature while maintaining adequate therapeutic titre for inducing a protective immune response.