In this study, we established a new experimental murine model of disseminated T. marneffei infection closely mimic the clinic feature of T. marneffei infection observed in humans. The most common clinical features observed in patients with T. mameffei include fever (98.0%), anemia (74.8%), and weight loss (71.6%) . These three symptoms are common non-specific symptoms of infectious diseases. Dissemination of the disease is characterized by skin lesions (69.7%-85%), such as papules with central necrosis [2,13]. This characteristic lesion can be a single or first-episode symptom of Talaromycosis and has a strong suggestive role in the diagnosis of this disease . It is therefore important to observe this particular lesion in a mouse model. The gross appearance of skin lesions in our model is consistent with that of human skin lesions in infected patients. Pulmonary infiltrates, lymphadenopathy, splenomegaly, and hepatomegaly were also noted in many patients . Lesions in these organs were also found in the anatomy of our model group. Previous studies had reported diffuse infiltration of macrophages engorged with proliferating yeast cells in tissues[2,15] and a variety of organs including the skin, bone marrow, lymph nodes, liver, lung, bone, spleen, nasopharynx, bowel, kidney, pericardium, meninges . We observed fungal yeasts in the skin, bone marrow, mesenteric nodules, liver, lung, spleen, kidney, rectum, small intestine tissues, but not in the brain and skeletal muscle. Except for the meninges, our model infection organs were almost identical to the infected organs of patients reported in the literature. Therefore, our murine model successfully mimicked deep-seated visceral fungal infection, and it was the first time that our murine model had skin lesions similar to those found in human patients.
Our modeling method has some advantages over the modeling method in the previous studies[10-12]). The first advantage is that it is easy to operate and no special equipment is needed. Recently, Liu et al had developed a murine pulmonary T. marneffei infection model, and they used BALB/c nude mice with a nebulizer to deliver T. marneffei conidia to the lungs with mice housed in exposure chamber. The procedure needs a nebulizer driven by compressed air to generate a suspension containing conidia to aerosols and then input into a multi-animal exposure chamber. After passing through the exposure chamber the air is needed to filter before being sent into the exhaust system. The generated aerosol was connected to the exposure chamber, which was connected to an air filter though another tube to prevent spores from contaminating the environment. They first constructed a murine pulmonary model that would mimic human Talaromycosis utilizing inhalation exposure . In their study, not only special experimental equipment but also air pollution and safety issues need to be considered. In another study, Sun et al injected T. marneffei yeast suspension the lateral tail vein of mice to establish the infection . However, in operation, the fungal yeast easily agglomerates or precipitates, thus increasing the risk of pulmonary embolism in mice. Kudenken et al established T. marneffei infection in mice by intratracheal instillation, which is also a complex procedure and time-consuming . The second advantage is that no big difference in the total survival time of each T. marneffei infected mouse in our model, with the first death on day 20 and all death on day 25. However, in the inhaled mouse model , animals began to die on day 15 after infection and some were still 35% alive on day 40. In the tail vein injection mouse model , animals began to die on day 8 after infection and all the mice died on day 18, animals of the intratracheal instillation mouse model began to die on day 33 after infection and all the mice died day 44 .
In conclusion, we successfully developed a stable, safe and maneuverable murine model of T. marneffei infection. The symptoms and diseased organs of this model are highly consistent with the disseminated T. marneffei infections in patients. This murine model may be used for understanding the pathogenesis of this disease.