Reinfection in American Cutaneous Leishmaniasis: Evaluation of Clinical Outcomes in the Hamster Model
Vol. 93(3): 353-356
Y Osorio/+, SJ Gonzalez*, VL Gama*, BL Travi
Centro Internacional de Entrenamiento e Investigaciones Médicas (CIDEIM), AA 5390, Cali, Colombia *Universidad de Los Andes, Santafé de Bogotá, Colombia
There is no clear understanding of the outcome of reinfection in New World cutaneous leishmaniasis, and its role in the relationship to the development of protection or secondary disease. For this reason, reinfection experiments with homologous (Leishmania panamensis-L. panamensis) and heterologous (L. major-L. panamensis) species of leishmaniae were conducted in the hamster model. The different protocols for primary infections prior to the challenge with L. panamensis were as follows: (a) L. major, single promastigote injection, (b) L. major, three booster infections, (c) L. panamensis, followed by antimonial treatment to achieve subclinical infection, (d) L. panamensis, with active lesions, (e) sham infected, naive controls. Although all reinfected hamsters developed lesions upon challenge, animals with active primary lesions due to L. panamensis, and receiving booster infections of L. major had the most benign secondary lesions (58-91% and 69-76% smaller than controls, respectively, P<0.05). Subclinically infected animals had intermediate lesions (40-64% smaller than controls, P<0.05), while hamsters which received a single dose of L. major had no significant improvement over controls. Our results suggested that L. major could elicit a cross protective response to L. panamensis, and that the presence and number of amastigotes persisting after a primary infection may influence the clinical outcome of reinfections.
Key words: immunoprophylaxis - reinfection - Leishmania major - Leishmania panamensis - hamster
Human populations in leishmaniasis endemic areas are continuously exposed to the bites of sandflies and consequently are at risk of suffering repeated infections (Sebai & Morsy 1976, Weigle et al. 1993). Understanding the clinical and immunological responses of individuals who are reinfected could shed some light on the most adequate approaches for adopting prevention and control strategies.
In the Old World, leishmanization with small doses of Leishmania major in body sites usually covered by clothes was used as an immunopro-phylactic strategy. Although this method resulted in total or partial protection against a subsequent infection, leishmanization has been abandoned due to the risk of occasional severe lesions, and the fact that a live virulent organism was introduced into humans (Greenblatt 1988, Modabber 1990).
In the New World, the frequency of reinfections is more difficult to assess because a variable proportion of individuals may relapse or suffer mucosal metastasis after a primary infection (Marsden 1986). The higher incidence of cutaneous leishmaniasis in children (CIDEIM, unpublished data) and young adults of the Colombian Pacific coast (Weigle et al. 1993), suggests that older individuals have developed an effective immune response against the parasite. Nevertheless, the proportion of exposed people capable of mounting a protective response against reinfection has yet to be determined. In a limited study involving 24 patients with secondary lesions due to L. viannia spp. it was shown, through kDNA restriction fragment electrophoresis and molecular karyotyping, that reinfection accounted for 50% of the cases, implying that these individuals had not developed a protective immune response as a consequence of the primary infection (Saravia et al. 1990).
Experimental data about reinfection with the viannia subgenus are scarce, mainly due to the lack of adequate laboratory models in which immunological responses could be studied. The contrasting results of reinfection obtained in C57Bl/6 mice infected with L. mexicana (Pérez et al. 1979, Aragort et al. 1993), as well as the inconsistent protective responses observed within each species in Mystromys albicaudatus and Callithrix penicillata (Beacham et al. 1982, Cuba-Cuba & Marsden 1993), underscore the need for a systematic approach to this subject. In order to evaluate the utility of the hamster as a model for immunoprophylactic strategies against L. viannia spp. we carried out reinfection experiments with L. major and L. panamensis.
Figure 1 | Figure 2 | Figure 3
This work was supported by the U.S. National Institute of Allergy and Infectious Diseases, National Institutes of Health, Tropical Medicine Research Center Grant P50-AI30603-04 and COLCIENCIAS 2229-04-004-92.
+Corresponding author. Fax: +57-2-667.2989
Received 15 August 1997
Accepted 18 February 1998
Memórias Home Page | Editorial Office | Subscription Information | Search
Vol. 93(3) - Contents | Instructions to Authors | News and Events | Past Issues | E-mail
