Prophylactic effect of cutaneous leishmaniasis against COVID-19: a case-control field assessment

Abstract

Introduction: We assessed the potential relationship between COVID-19 and laboratory-confirmed cutaneous leishmaniasis (CL)-registered cases with a history of scarring, compared with volunteer participants without history of CL.

Methods: This case-control retrospective study was conducted in southeastern Iran with a high anthroponotic cutaneous leishmaniasis (ACL) burden.

Results: Overall, n=1010 CL cases (n=479 male, n=531 female) were evaluated for infection with SARS-CoV-2. In the CL case group, 2 men and 1 woman (0.3% in total) had a mild form of COVID-19 disease; none were hospitalized or died. In contrast, of n=2020 participants without history of CL, n=57 (2.9%) contracted laboratory-confirmed COVID-19, including mild (66.7%), hospitalized (26.3%), critical (3.5%) and fatal (3.5%). There was a strong negative association between CL infection and COVID-19. The burden of COVID-19 in CL-cured participants significantly reduced the morbidity (odds ratio: 0.12; CI: 0.03-0.30; P <0.001) and mortality (percentile: -4.10, -0.02).

Conclusion: Participants with a history of CL scar had significantly reduced incidence of COVID-19 morbidity and mortality. The cross-protection mediated by CL may retard COVID-19 in endemic countries. However, further longitudinal studies are needed to explore the potential profile and duration of this protection offered by CL against COVID-19.

Keywords: COVID-19; coinfection; cutaneous leishmaniasis; prophylactic effect.

Figure 1

Map of Kerman county, southeastern Iran, where the study was carried out.

Figure 2

Representative images of various lesions from cutaneous leishmaniasis patients from Kerman county, southeastern Iran.

Figure 3

A proposed model of immune response. Leishmania-mediated T helper (Th)1 cell concomitant immunity can induce the production of Th1 type cytokines such as interleukin (IL)-12 and interferon (IFN)-γ, which enter the blood from the infected skin and then are diffused into the SARS-CoV-2-infected lungs. IL-12 and IFN-γ can potentiate the anti-viral immune response and prevent viral spreading into the blood. Th1 type cytokines inhibit viral replication and activate local natural killer cells and CD8⁺ cytotoxic T lymphocytes, eliminating virus-infected cells to limit viral load in the lungs (Right). In the absence of Leishmania-mediated Th1 cell concomitant immunity, SARS-CoV-2-infected epithelial cells can produce type I IFN-γ, which can control COVID-19 replication. If SARS-CoV-2 evades the type I IFN-γ-mediated response, it then enters the blood and causes blood viremia and subsequent consequences.