The Leishmania HSP20 is antigenic during natural infections, but, as DNA vaccine, it does not protect BALB/c mice against experimental L. amazonensis infection.

Protozoa of the genus Leishmania are causative agents of leishmaniasis, an important health problem in both human and veterinary medicine. Here, we describe a new heat shock protein (HSP) in Leishmania, belonging to the small HSP (sHSP) family in kinetoplastids. The protein is highly conserved in different Leishmania species, showing instead significant divergence with sHSP's from other organisms. The humoral response elicited against this protein during Leishmania infection has been investigated in natural infected humans and dogs, and in experimentally infected hamsters. Leishmania HSP20 is a prominent antigen for canine hosts; on the contrary, the protein seems to be a poor antigen for human immune system. Time-course analysis of appearance of anti-HSP20 antibodies in golden hamsters indicated that these antibodies are produced at late stages of the infection, when clinical symptoms of disease are patent. Finally, the protective efficacy of HSP20 was assessed in mice using a DNA vaccine approach prior to challenge with Leishmania amazonensis.

Importance of small heat shock protein 20 (hsp20) C-terminal extension in cardioprotection.

Recent studies show that overexpression of small heat shock protein 20 (Hsp20) in mouse hearts reduces infarct size and improves cardiac performance. However, it is not known whether Hsp20 exerts its protective action through improved calcium handling or chaperone activity. The C-terminal extensions of small heat shock proteins, such as alphaB-crystallin and Hsp25, are implicated in chaperoning activity. Through adenovirus mediated overexpression of Hsp20 with C-terminal extension substitution, we delineated the mechanism of protection. Neonatal and adult rat cardiomyocytes overexpressing either the full-length Hsp20 or Hsp20 with a C-terminal extension substitution were subjected to simulated ischemia for 14-16 h followed by reperfusion 6-8 h. Overexpressing Hsp20 with a C-terminus extension substitution did not protect against simulated ischemia/reperfusion in either adult (98+/-8.8% LDH release of control) or neonatal cardiomyocytes (103+/-1.8% CK release of control) as measured by creatine kinase (CK) and lactate dehydrogenase (LDH) cell viability assays (n=4, P<0.05). However, this Hsp20 C-terminal substitution mutant increased calcium transients 33+/-11% and cell contraction amplitude 60+/-15% as quantified through epifluorescence microscopy (n=16 to 34 cells per heart from 4 to 5 hearts, P<0.05). In contrast, overexpression of the full-length Hsp20 protected cultured adult (53+/-8.5% LDH release of control) and neonatal rat (57+/-8.3% CK release of control) cardiomyocytes from simulated ischemia/reperfusion injury. This overexpression also increased calcium transients 30+/-10% and cell contraction amplitude 50+/-10%. These novel data suggest that the C-terminal extension of Hsp20 is essential for cardioprotection. Hsp20 renders this protection through its C-terminal extension protein domain, while this part of the protein is not involved in the Hsp20 ability to increase both calcium transients and cell contraction.