NEWS ▶▶▶ Transgenic pigs tested to stop ASFv

Trials will soon start in Germany to observe progress with transgenic pigs with immune cells that show resistance to African Swine Fe- ver virus (ASFv). Originally, tests were sched- uled for May to test pigs for ASF resistance, by challenging them with infections with virulent ASFv. Due to Covid-19, the work is now expect- ed to commence in June. Dr Björn Petersen and his colleagues at the Friedrich-Loeffler-Institut, Germany’s Federal Research Institute for Animal Health, are build- ing on research that has shown that it is possi- ble to generate pigs that are resistant to viral attacks through the use of gene editing. Using CRISPR/Cas9, Petersen and his team have ap- plied a genetic construct from a bacteria into foetal swine cells called fibroblasts. This edit resulted in a genetic ‘scissor’ that cuts essential parts of the viral genome and therefore de- stroys it. The cells were tested to see if the bac- teria genes were being expressed in a stable manner, and ASFv replication was indeed sup- pressed. Petersen said, “We found that expres- sion of the anti-viral guide RNA leads to

Larvae meal as fishmeal replacement

roughly a 10,000-fold decrease in virus replica- tion of the ‘Armenia’ strain of ASF.” The fibroblasts were then cloned to generate living offspring. Macrophages in blood sam- ples from these pigs were challenged with ASFv, and reduced levels of ASFv replication were noted.

Gene editing is a sensitive issue in the Europe- an Union. Offspring of gene-edited animals are considered genetically modified organisms in the EU, hence these animals cannot be used for commercial production. For research purposes, however, gene editing is allowed.

UK: ASF vaccine protects 100% of pigs

UK scientists are a step closer to developing a vital vaccine for African Swine Fever (ASF). In a recent trial, 100% of pigs immunised with the new vaccine survived a lethal dose of ASF virus (ASFv). The research, carried out by scientists from The Pirbright Institute in the UK, was published in the peer reviewed journal Vaccines. According to a news release shared by the institute, the team developed a vectored vaccine, which uses a non-harmful virus (the vector) to deliver eight strategically selected genes from the ASFv genome into pig cells. Once inside the cell, the genes produce viral proteins which prime the pig immune cells to respond to an ASF infection. All pigs that were immunised with the vaccine were protected from severe disease after challenge with an otherwise fatal strain of ASFv, although some clinical signs of disease did develop. Dr Chris Netherton, head of Pirbright’s ASF vaccinology group, said: “It is very encouraging to see that the genes we have selected are

able to protect pigs against ASF. Although the pigs showed clinical signs of infection after challenge with the virus, our study has shown for the first time that a vectored vaccine against ASF is a realistic possibility.” This type of vaccine will also enable the differ- entiation of infected animals from those that have received a vaccine. According to the insti- tute, that is an important feature, as it would allow vaccination programmes to be estab- lished without sacrificing the ability to trade. The research paper stated that the data pro- vide the basis for the further development of a subunit vaccine against ASF. Dr Netherton said, “Our next step will be to uncover the mechanisms behind how the proteins pro- duced by the virus genes stimulate the im- mune system so we can refine and add to those included in the vaccine to improve effectiveness.” Earlier, teams in the USA and in China had also reported positive results in their attempts to get closer to a vaccine against ASF.

In an attempt to learn whether larvae meal of the black soldier fly can be a sustainable al- ternative to fishmeal for piglets, Chinese re- searchers have studied the effects of different inclusion levels on various performance pa- rameters. The black soldier fly (Hermetia illu- cens) is one of the most promising species to be used in livestock nutrition, due to its rela- tively high crude protein content, with a well-balanced essential amino acid profile. Their article in Animal Feed Science and Tech- nology described a trial with 128 piglets, four levels of full-fat H. illucens inclusion and two feeding phases. The researchers zoomed in on the question of whether the larvae could also be an alternative to fishmeal and wheth- er that would affect growth performance, ap- parent nutrient digestibility, blood parame- ters and gut morphology of weanling piglets. Among the results shared, the researchers noted that the body weight on day 14, aver- age daily growth across days 1–14, and the relative weight of the liver, pancreas and small intestine had a linear increase in re- sponse to H. illucens larvae meal consump- tion, while the feed conversion ratio across days 1–14 exhibited a linear and quadratic decrease in the response. Linear and quadrat- ic decreases were detected for the crude pro- tein and crude fat digestibility. In addition, 2% H. illucens larvae increased the villus height in the jejunum, the scientists wrote. The researchers concluded that the results in- dicated that feeding 2% full-fat H. illucens lar- vae meal to partly replace fishmeal changed the host metabolism, immune status and in- testinal morphology of weanling piglets.


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▶PIG PROGRESS | Volume 36, No. 4, 2020 49


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