Dimorphism and Dissemination of Histoplasma capsulatum in the Upper Respiratory Tract after Intranasal Infection of Bats and Mice with Mycelial Propagules

AbstractCryptococcus neoformans is an important fungal pathogen, causing life-threatening pneumonia and meningoencephalitis. Brain dissemination of C. neoformans is thought to be a consequence of an active infection in the lung which then extravasates to other sites. Brain invasion results from dissemination via the bloodstream, either by free yeast cells in bloodstream or Trojan horse transport within mononuclear phagocytes. We assessed brain dissemination in three mouse models of infection: intravenous, intratracheal, and intranasal. All three modes of infection resulted in dissemination of C. neoformans to the brain in under 3 hours. Further, C. neoformans was detected in the entirety of the upper respiratory tract and the ear canals of mice. In recent years, intranasal infection has become a popular mechanism to induce pulmonary infection because it avoids surgery but our findings show that instillation of C. neoformans produces cryptococcal nasal infection. These findings imply that immunological studies using intranasal infection should assume the initial sites of infection of infection are brain, lung and upper respiratory tract, including the nasal airways.ImportanceCryptococcus neoformans causes an estimated 181, 000 deaths each year, mostly associated with untreated HIV/AIDS. C. neoformans has a ubiquitous worldwide distribution. Humans become infected from exposure to environmental sources and the fungus lays dormant within the human body. Upon immunosuppression, such as AIDS or therapy-induced as required by organ transplant recipients or autoimmune disease patients, cryptococcal disease reactivates and causes life-threatening meningitis and pneumonia. This study has detected that upon contact with the host, C. neoformans can quickly (a few hours) reach the host brain and will also colonize the nose of infected animals. Therefore, this work paves the way to better knowledge of how C. neoformans travels through the host body. Understanding how C. neoformans infects, disseminates and survives within the host is critically required so that we can prevent infections and the disease caused by this deadly fungus.

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Intranasal Inoculation of Cryptococcus neoformans in Mice Produces Nasal Infection with Rapid Brain Dissemination

mSphere ◽

10.1128/msphere.00483-19 ◽

2019 ◽

Vol 4 (4) ◽

Cited By ~ 2

Author(s):

Carolina Coelho ◽

Emma Camacho ◽

Antonio Salas ◽

Alexandre Alanio ◽

Arturo Casadevall

Keyword(s):

Respiratory Tract ◽

Cryptococcus Neoformans ◽

Mononuclear Phagocytes ◽

Yeast Cells ◽

Upper Respiratory Tract ◽

Intranasal Infection ◽

Content Type ◽

Brain Invasion ◽

Life Threatening ◽

Upper Respiratory

ABSTRACT Cryptococcus neoformans is an important fungal pathogen, causing life-threatening pneumonia and meningoencephalitis. Brain dissemination of C. neoformans is thought to be a consequence of an active infection in the lung which then extravasates to other sites. Brain invasion results from dissemination via either transport by free yeast cells in the bloodstream or Trojan horse transport within mononuclear phagocytes. We assessed brain dissemination in three mouse models of infection: intravenous, intratracheal, and intranasal models. All three modes of infection resulted in dissemination of C. neoformans to the brain in less than 3 h. Further, C. neoformans was detected in the entirety of the upper respiratory tract and the ear canals of mice. In recent years, intranasal infection has become a popular mechanism to induce pulmonary infection because it avoids surgery, but our findings show that instillation of C. neoformans produces cryptococcal nasal infection. These findings imply that immunological studies using intranasal infection should assume that the initial sites of infection of infection are brain, lung, and upper respiratory tract, including the nasal airways. IMPORTANCE Cryptococcus neoformans causes an estimated 181, 000 deaths each year, mostly associated with untreated HIV/AIDS. C. neoformans has a ubiquitous worldwide distribution. Humans become infected from exposure to environmental sources, after which the fungus lays dormant within the human body. Upon AIDS-induced immunosuppression or therapy-induced immunosuppression (required for organ transplant recipients or those suffering from autoimmune disorders), cryptococcal disease reactivates and causes life-threatening meningitis and pneumonia. This study showed that upon contact with the host, C. neoformans can quickly (a few hours) reach the host brain and also colonizes the nose of infected animals. Therefore, this work paves the way to better knowledge of how C. neoformans travels through the host body. Understanding how C. neoformans infects, disseminates, and survives within the host is critically required so that we can prevent infections and the disease caused by this deadly fungus.

Download Full-text