Pathogenesis, immunity, and control of coronaviruses in a large natural host animal, the pig

自2003年以来，冠状病毒已导致三次人类严重呼吸道疾病流行，最后一次是目前的COVID-19大流行。在每种情况下，病毒都来自一种动物，但能够感染人类。在前两次流行病中，SARS和MERS，虽然病毒从动物传播到人类，但它并不容易从一个人传播到另一个人，限制了流行病的规模。另一方面，SARS-CoV-2很容易在人类之间传播。由于病毒可以变异（改变其遗传物质），随着时间的推移，它可以逃避免疫反应，因此就像流感一样，可能需要重复接种疫苗来预防严重疾病，尽管迄今为止疫苗未能阻止病毒传播。人类与许多动物的接触越来越密切，因此进一步流行的风险很高。猪就是这样一个物种，可以感染许多冠状病毒，包括猪呼吸道冠状病毒（PRCV），它会导致类似于COVID-19的肺炎。与SARS-CoV-2一样，猪冠状病毒也会发生变异，最近出现了毒性更强的病毒，可在猪群中引起经济上重要的疾病。猪冠状病毒也在一些人身上被检测到，尽管它们似乎还没有在人与人之间传播。由于PRCV毒株的出现会在猪中引起经济上重要的疾病，并且由于猪冠状病毒可能会转移到人类并引起另一场冠状病毒流行，我们希望更好地了解病毒如何感染呼吸道细胞，免疫系统如何反应感染早期的病毒以及后来如何导致肺部损伤或防止进一步感染。这些信息对于设计预防或治疗猪和人类疾病的新方法非常重要。我们还将测试一种新的疫苗平台，该平台有可能诱导非常强的免疫反应，并可能诱导免疫反应，从而抵御各种不同的冠状病毒。我们已经发现PRCV毒株可导致严重的肺部疾病（肺炎）或非常轻微的肺部炎症。我们还发现，那些导致严重疾病的病毒在鼻子、气管和肺的细胞中繁殖，而那些导致轻度炎症的病毒只在鼻子中繁殖良好。比较这些毒株的结构，并通过基因操作制造新毒株，将使我们能够确定病毒进入呼吸道不同细胞的重要部分。这些研究的一部分将在培养的肺和气管（气管）组织上进行，尽量减少使用活体动物。为了发现免疫系统对有毒和无害病毒的反应，我们将从感染两种病毒株的动物身上提取组织，分析感染后一天和十四天哪些基因被激活。这将告诉我们这两种病毒株是如何编程免疫应答的，以及在病毒与免疫系统的早期相互作用后会产生什么样的免疫应答。我们将使用一种新的疫苗平台，该平台允许病毒与细胞结合的部分（受体结合域或RBD）展示在颗粒上，并在猪体内产生病毒的内部蛋白质，以提出几个问题。首先，这种疫苗是否能诱导出强大的保护性抗体，其次，它是否也能诱导出保护性T细胞（免疫反应的第二个保护臂），第三，抗体和T细胞结合在一起是否比单独使用更具保护性。最后，我们将使用该系统测试在疫苗中展示许多不同的RBD是否诱导可以保护许多不同病毒株的抗体

Coronaviruses have caused three epidemics of severe respiratory disease in humans since 2003, the last being the present COVID-19 pandemic. In each case the virus came from an animal species but was able to infect humans. In the first two epidemics, SARS and MERS, although the virus passed from an animal to humans, it did not pass readily from one human to another, limiting the size of the epidemic. SARS-CoV-2 on the other hand is readily transmitted between humans. Because the virus can mutate (change its genetic material), over time it can escape from the immune response, so that as in the case of influenza, repeated vaccination may be required to prevent severe disease, although so far the vaccines have failed to prevent virus transmission.Humans are in increasingly close contact with many animal species and the risk of further epidemics is therefore high. Pigs are one such species and can be infected with many coronaviruses including porcine respiratory coronavirus (PRCV), which causes a pneumonia similar to COVID-19. Like SARS-CoV-2 porcine coronaviruses can mutate, and recently more virulent viruses have emerged that cause economically important disease in pig herds. Pig coronaviruses have also been detected in some humans although as yet they do not appear to transmit between people. Because of the emergence of PRCV strains that cause economically important disease in pigs and because pig coronaviruses might jump to humans and cause another coronavirus epidemic, we wish to understand better how the virus infects cells in the respiratory tract, how the immune system reacts to the virus early in infection and how later on it either causes lung damage or protects against further infection. This information will be important for designing new ways to prevent or treat the disease both in pigs and humans. We will also test a novel vaccine platform which has the potential to induce very strong immune responses and possibly immune responses that could protect against widely different coronavirus.We have discovered PRCV strains that cause either severe lung disease (pneumonia) or very mild lung inflammation. We have also shown that those that cause severe disease multiply in the cells of the nose, windpipe and lungs, while those that cause mild inflammation multiply well only in the nose. Comparing the structure of these strains and making new strains by genetic manipulation will allow us to identify the parts of the virus that are important for virus entry into different cells in the respiratory tract. Part of these studies will be performed on cultured lung and tracheal (windpipe) tissues, minimising the use of live animals. To discover how the immune system responds to the virulent and innocuous viruses we will take tissues from animals infected with the two virus strains and analyse what genes are turned on one day and fourteen days after infection. This will tell us how the two virus strains programme the immune response and what sort of immune response develops after the early interaction of the viruses with the immune system.We will use a novel vaccine platform which allows the part of the virus that binds to cells (the receptor binding domain or RBD) to be displayed on a particle and internal proteins of the virus to be produced in the pig to ask several questions. First whether this vaccine induces strong and protective antibodies, second whether it can also induce protective T cells (the second protective arm of the immune response) and thirdly whether if both antibodies and T cells together are more protective than either alone. Finally using this system, we shall test whether displaying many different RBD in the vaccine induces antibodies that can protect against many different virus strains