AUTHOR=Tongluan Natthida , Shelton Layne T. , Collins J. Hunter , Ingraffia Patrick , McCormick Gregory , Pena Maria , Sharma Rahul , Lahiri Ramanuj , Adams Linda B. , Truman Richard W. , Macaluso Kevin R. 

TITLE=Mycobacterium leprae Infection in Ticks and Tick-Derived Cells

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.761420

DOI=10.3389/fmicb.2021.761420

ISSN=1664-302X

ABSTRACT=<p>Leprosy is a zoonosis in the southern United States involving humans and wild armadillos. The majority of patients presenting with zoonotic strains of <italic>Mycobacterium leprae</italic> note extensive outdoor activity but only rarely report any history of direct contact with wild armadillos. Whether <italic>M. leprae</italic> is transmitted to new vertebrate hosts through the environment independently or with the aid of other organisms, e.g., arthropod vectors, is a fundamental question in leprosy transmission. The objectives of this study were to assess the potential for ticks to transmit <italic>M. leprae</italic> and to test if viable <italic>M. leprae</italic> can be maintained in tick-derived cells. To evaluate tick transmission, nymphal <italic>Amblyomma maculatum</italic> ticks were injected with isolated <italic>M. leprae.</italic> Infection and transmission were assessed by qPCR. Ticks infected as nymphs harbored <italic>M. leprae</italic> through vertical transmission events (nymph to adult and adult to progeny); and, horizontal transmission of <italic>M. leprae</italic> to a vertebrate host was observed. <italic>Mycobacterium leprae</italic> DNA was detected in multiple tick life cycle stages. Likewise, freshly isolated <italic>M. leprae</italic> (Thai-53) was used to infect a tick-derived cell line, and enumeration and bacterial viability were assessed at individual time points for up to 49 days. Evaluations of the viability of long-term cultured <italic>M. leprae</italic> (Thai-53 and Br4923) were also assessed in a mouse model. Tick-derived cells were able to maintain viable <italic>M. leprae</italic> over the 49-day course of infection and <italic>M. leprae</italic> remained infectious within tick cells for at least 300 days. The results of this study suggest that ticks themselves might serve as a vector for the transmission of <italic>M. leprae</italic> and that tick cells are suitable for maintenance of viable <italic>M. leprae</italic> for an extended period of time.</p>