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Marburg virus; Disease tolerance; Emerging zoonotic Pathogen; Gene expression; Immune response; Monocyte; Reservoir host; Virus-host interaction

Introduction

Marburg virus, a highly pathogenic member of the Filoviridae family, is a significant threat to human health, causing severe hemorrhagic fever outbreaks with high mortality rates. The virus is believed to have originated from bats, with the Egyptian fruit bat (Rousettus aegyptiacus) identified as a natural reservoir [1]. However, what is particularly intriguing is that these bats can harbor the virus without showing any signs of disease—a phenomenon known as asymptomatic infection. This raises important questions about the mechanisms underlying immunoprotective disease tolerance in bats and its implications for both bats and humans. Immunoprotective disease tolerance refers to the ability of an organism to limit the damage caused by a pathogen without necessarily clearing the infection. While humans and other animals suffer from severe disease when infected with Marburg virus, bats that serve as the reservoir species appear to tolerate the virus without any noticeable clinical symptoms. Understanding how bats achieve this immunoprotective disease tolerance is crucial for shedding light on their unique immune responses and potentially translating this knowledge into novel therapeutic strategies for managing viral infections in humans [2].

Bats possess a range of unique immune system characteristics that contribute to their ability to tolerate Marburg virus infection. One such characteristic is a dampened inflammatory response, which prevents excessive tissue damage caused by an overactive immune system. Unlike in humans, bats can efficiently regulate the production of pro-inflammatory molecules, such as cytokines, thereby preventing immunopathology and maintaining tissue homeostasis. Additionally, bats have an enhanced ability to repair damaged DNA caused by the virus [3]. This robust DNA repair mechanism is thought to be one of the factors contributing to their resistance to the deleterious effects of viral replication, reducing the risk of severe disease manifestation. Furthermore, bats possess a higher antioxidant capacity, which helps mitigate oxidative stress induced by the virus, providing another layer of protection against viral-induced tissue damage [4].

Bats carry Marburg virus

People may be at risk of exposure to Marburg viruses if they have contact with: Egyptian rousette bats Rousettus aegyptiacus – the reservoir host, or their urine and/or excretions; People sick with Marburg virus disease (MVD)

Marburg disease

This disease was named Marburg virus disease (MVD) after the West German town of Marburg Ander Lahn, where most human infections and deaths had been recorded. Consequently, the Marburg episode received the most scientific and media attention [5].

Marburg virus, a highly pathogenic member of the Filoviridae family, has caused outbreaks of severe hemorrhagic fever in humans and non-human primates. The virus is thought to originate from bats, specifically the Egyptian fruit bat (Rousettus aegyptiacus), which serves as a natural reservoir. What is particularly intriguing is that these bats appear to tolerate the infection without showing any signs of disease. This phenomenon, known as asymptomatic infection, raises important questions about the mechanisms underlying immunoprotective disease tolerance and its implications for both bats and humans. Asymptomatic infection occurs when an individual is infected with a pathogen but does not exhibit any clinical symptoms. In the case of Marburg virus, while humans and other animals suffer from severe disease, bats that serve as the reservoir species remain seemingly unaffected. This observation suggests that bats have evolved strategies to tolerate the virus without triggering an immune response that leads to disease [6].

Immunoprotective disease tolerance is a concept that describes the ability of an organism to limit the damage caused by a pathogen without necessarily clearing the infection. It involves a delicate balance between the host's immune response and the pathogen's ability to evade or manipulate the immune system. In the case of Marburg virus infection in bats, this tolerance likely plays a critical role in maintaining a harmonious relationship between the host and the virus [7].

Several factors contribute to the immunoprotective disease tolerance observed in bats. First, bats have a unique immune system that exhibits distinct characteristics compared to other mammals. For instance, they have a dampened inflammatory response, which prevents excessive tissue damage caused by an overactive immune system. Additionally, bats have an enhanced ability to regulate the production of pro-inflammatory molecules, such as cytokines, which helps to prevent immunopathology [8].

Furthermore, bats possess a more efficient DNA repair mechanism that enables them to repair damaged DNA caused by the virus more effectively. This enhanced DNA repair capability is thought to contribute to their resistance to the deleterious effects of viral replication, reducing the risk of severe disease. Additionally, bats have a higher antioxidant capacity, which helps mitigate oxidative stress induced by the virus. Another interesting aspect of immunoprotective disease tolerance in bats is their unique antiviral defense mechanisms. Bats have a sophisticated innate immune system that recognizes and responds to viral infections promptly. They possess a diverse repertoire of pattern recognition receptors, such as Toll-like receptors (TLRs), which detect viral components and trigger an immune response. However, the activation of these innate immune pathways is tightly regulated in bats to prevent excessive inflammation and tissue damage [9].

Understanding the mechanisms underlying immunoprotective disease tolerance in bats can provide valuable insights for human health. By deciphering how bats coexist with Marburg virus without suffering from disease, researchers may identify novel therapeutic strategies for combating viral infections in humans. For instance, modulating the immune response to limit excessive inflammation and tissue damage could be a promising avenue for treating diseases caused by other highly pathogenic viruses. Furthermore, investigating the unique antiviral defense mechanisms in bats may uncover novel targets for antiviral drug development. By understanding how bats regulate their immune response, scientists could potentially identify key molecules or pathways that can be targeted to enhance antiviral defenses in humans [10].

Conclusion

The phenomenon of asymptomatic infection in Marburg virus reservoir bats and their immunoprotective disease tolerance have provided valuable insights into the complex interaction between bats and the virus. Bats, particularly the Egyptian fruit bat serve as natural reservoirs for the highly pathogenic Marburg virus, yet they do not exhibit any signs of disease despite being infected. Understanding the mechanisms underlying this immunoprotective disease tolerance has significant implications for both bats and humans.Bats exhibit unique immune system characteristics that contribute to their ability to tolerate Marburg virus infection. Their dampened inflammatory response, enhanced DNA repair mechanisms, and increased antioxidant capacity help prevent excessive tissue damage caused by the virus. Additionally, their sophisticated innate immune system promptly responds to viral infections while tightly regulating inflammation, ensuring a balanced immune response.

The knowledge gained from studying immunoprotective disease tolerance in bats may have profound implications for human health. It can potentially lead to the development of novel therapeutic strategies for managing viral infections in humans. By modulating the immune response and preventing excessive inflammation and tissue damage, scientists may find ways to mitigate the severity of diseases caused by highly pathogenic viruses. Furthermore, understanding the antiviral defense mechanisms in bats may uncover new targets for antiviral drug development. By identifying key molecules or pathways that enhance antiviral defenses, researchers can potentially develop effective treatments for viral infections in humans.

Studying how bats coexist with Marburg virus without suffering from disease not only provides insights into the biology of bats but also offers valuable lessons for preventing severe outcomes in human infections. By unraveling the secrets of bat immunoprotective disease tolerance, scientists can better understand viral pathogenesis and devise strategies to control and manage outbreaks more effectively. The immunoprotective disease tolerance observed in Marburg virus reservoir bats is a fascinating phenomenon that sheds light on the intricate relationship between bats and the virus. The unique immune system characteristics and defense mechanisms of bats have implications for human health, including the development of novel therapeutic approaches and the identification of potential targets for antiviral drug development. Understanding how bats tolerate viral infections without succumbing to disease can guide us in managing viral infections in humans and mitigating their impact on public health.

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