Overexpression of the natural inhibitor of cysteine peptidases in Leishmania mexicana leads to reduced virulence and a Th1 response.
Leishmania mexicana cysteine peptidases (CPs) have been identified as important parasite virulence factors. More recently, a natural inhibitor of CPs (ICP) from L. mexicana has been characterized, and ICP mutants have been created. Infection of BALB/c mice with ICP null mutants or ICP reexpressing mutants resulted in nonhealing, progressively growing lesions albeit slightly attenuated compared with the growth of lesions produced by wild-type parasites. In contrast, BALB/c mice infected with mutants overexpressing ICP were able to significantly control lesion growth or heal. While BALB/c mice infected with wild-type parasites, ICP null mutants, or ICP reexpressing mutants produced significant antibody responses, including immunoglobulin E (IgE), no Th1 response, as indicated by antigen-induced splenocyte gamma interferon (IFN-gamma) production, could be demonstrated. In contrast, BALB/c mice infected with mutants overexpressing ICP produced significantly less antibody, particularly IgE, as well as significantly reduced splenocyte interleukin-4 and enhanced IFN-gamma production. BALB/c mice were able to resolve infection following infection with one ICP overexpressing clone, which was subsequently used for vaccination studies with BALB/c mice. However, no protection was afforded these mice when they were challenged with wild-type parasites. Nevertheless, two other mouse strains susceptible to L. mexicana, C3H and C57BL/6, vaccinated with overexpressing ICP mutants were able to control challenge infection associated with an enhanced Th1 response. This study confirms that L. mexicana CPs are virulence factors and that ICPs have therapeutic potential.
Bryson
Karen
K
Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom.
Besteiro
Sébastien
S
McGachy
H Adrienne
HA
Coombs
Graham H
GH
Mottram
Jeremy C
JC
Alexander
James
J
D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000096:biosynthesis* / Q000235:genetics; D005260:Female; D017353:Gene Deletion; D005816:Genetic Complementation Test; D007073:Immunoglobulin E / Q000097:blood; D007371:Interferon-gamma / Q000378:metabolism; D007894:Leishmania mexicana / Q000276:immunology* / Q000472:pathogenicity*; D016773:Leishmaniasis, Cutaneous / Q000276:immunology / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D012720:Severity of Illness Index; D013154:Spleen / Q000276:immunology; D018417:Th1 Cells / Q000276:immunology*; D014774:Virulence; D037521:Virulence Factors / Q000037:antagonists & inhibitors*
D000913:Antibodies, Protozoan; D015853:Cysteine Proteinase Inhibitors; D037521:Virulence Factors; D007073:Immunoglobulin E; D007371:Interferon-gamma; D003546:Cysteine Endopeptidases