Neutrophils contribute to development of a protective immune response during onset of infection with Leishmania donovani.

Neutrophils are key components of the inflammatory response and as such contribute to the killing of microorganisms. In addition, recent evidence suggests their involvement in the development of the immune response. The role of neutrophils during the first weeks post-infection with Leishmania donovani was investigated in this study. When L. donovani-infected mice were selectively depleted of neutrophils with the NIMP-R14 monoclonal antibody, a significant increase in parasite numbers was observed in the spleen and bone marrow and to a lesser extent in the liver. Increased susceptibility was associated with enhanced splenomegally, a delay in the maturation of hepatic granulomas, and a decrease in inducible nitric oxide synthase expression within granulomas. In the spleen, neutrophil depletion was associated with a significant increase in interleukin 4 (IL-4) and IL-10 levels and reduced gamma interferon secretion by CD4(+) and CD8(+) T cells. Increased production of serum IL-4 and IL-10 and higher levels of Leishmania-specific immunoglobulin G1 (IgG1) versus IgG2a revealed the preferential induction of Th2 responses in neutrophil-depleted mice. Altogether, these data suggest a critical role for neutrophils in the early protective response against L. donovani, both as effector cells involved in the killing of the parasites and as significant players influencing the development of a protective Th1 immune response.

Differential cytotoxicity of phospholipid analogues to pathogenic Acanthamoeba species and mammalian cells.

OBJECTIVES: Previous studies have reported the ability of several phospholipid analogues to successfully inhibit the growth of Acanthamoeba species in vitro. This study tests further phospholipid analogues, either as free drug or in liposomal formulations, and unlike previous studies, examines their comparative toxicities to mammalian cells. METHODS: The relative cytotoxic activities of the phospholipid derivatives hexadecyl-PC, octadecyl-PC, elaidyl-PC, erucyl-PC and edelfosine, against Acanthamoeba castellanii, Acanthamoeba polyphaga and a rabbit corneal epithelial (RCE) cell line, was determined by the alamarBlue assay. Free and liposomal formulations were compared for hexadecyl-PC and elaidyl-PC. RESULTS: Both hexadecyl-PC and octadecyl-PC (IC50 values between 3.9 and 7.8 microM) demonstrated considerable activity against A. castellanii, as did elaidyl-PC (IC50 values between 15.6 and 31.25 microM). Both hexadecyl-PC and elaidyl-PC also proved effective against A. polyphaga (IC50 values between 15.6 and 31.25 and between 31.25 and 62.5 microM, respectively). In contrast, neither erucyl-PC nor edelfosine was inhibitory against either Acanthamoeba species. The growth of RCE cells was inhibited by octadecyl-PC, erucyl-PC and edelfosine (octadecyl-PC and erucyl-PC IC50 values between 7.8 and 15.6 microM and edelfosine IC50 values between 31.25 and 62.5 microM). Liposomal formulations of hexadecyl-PC and elaidyl-PC were less effective than free drug against both Acanthamoeba species. CONCLUSIONS: These results demonstrate that hexadecyl-PC has the highest therapeutic index and is the most promising for the treatment of acanthamoebiasis.

Both interleukin-4 (IL-4) and IL-4 receptor alpha signaling contribute to the development of hepatic granulomas with optimal antileishmanial activity.

The roles of interleukin-4 (IL-4) and IL-13 in the regulation of immunity to Leishmania donovani infection are still poorly understood. Here we show that the increased parasite load observed in IL-4(-/-) and IL-4 receptor alpha(-/-) mice correlates with retarded granuloma maturation and antileishmanial activity and that the increased parasite load observed in IL-4 receptor alpha(-/-) mice correlates with increased NOS2 expression and decreased serum gamma interferon levels. IL-4 and IL-13 appear to play little role in regulating collagen deposition in L. donovani-induced granulomas.

An essential role for IL-13 in maintaining a non-healing response following Leishmania mexicana infection.

A comparison of the growth of Leishmania mexicana in IL-4(-/-), IL-4Ralpha(-/-) and wild-type BALB/c mice demonstrated a disease exacerbative role for IL-13 as well as IL-4. Thus, while both IL-4(-/-) and IL-4Ralpha(-/-) mice were more resistant than wild-type controls to infection with L. mexicana, IL-4Ralpha(-/-) mice, which are unresponsive to IL-13 as well as IL-4, were significantly more resistant to parasite growth than their IL-4(-/-) counterparts. Cytokine and antibody analysis revealed a Th1-biased specific response in both infected IL-4(-/-) and IL-4Ralpha(-/-) mice compared with wild-type animals. Reconstituting SCID mice with IL-4(-/-), IL-4Ralpha(-/-) or wild-type splenocytes prior to infection demonstrated that the early onset of lesion growth was dependent on the presence of lymphocytes responding to IL-4 and/or IL-13, as lesions failed to develop in only the SCID IL-4Ralpha(-/-) reconstituted mice. An independent role for IL-13 in L. mexicana infection was demonstrated by comparing disease progression in IL-13(-/-), IL-4(-/-)/IL-13(-/-) and wild-type B6/129 mice. In contrast to IL-4(-/-)/IL-13(-/-) mice, which were resistant, IL-13(-/-) mice developed lesions similar in size to wild-type animals up to week 8 post-infection. However, in contrast to wild-type mice in which disease continued to progress, lesions eventually healed in IL-13(-/-) mice, in association with the development of a Th1 response. Collectively our results suggest that IL-4 plays a critical role in early lesion development, and that IL-13 plays a crucial part in maintaining a chronic non-healing infection.

Immune responses to a GnRH-based anti-fertility immunogen, induced by different adjuvants and subsequent effect on vaccine efficacy.

A modified GnRH peptide (CHWSYGLRPG-NH2) was conjugated to tetanus toxoid and formulated with different adjuvants (non-ionic surfactant vesicles, aluminium hydroxide, Quil A, PLGA (poly(lactide-co-glycolide)/triacetin), and Quil A/PLGA). A comparison of the anti-fertility efficacy of the formulations was made by examining specific antibody levels, antibody subclasses, endocrine ablation and gonadal atrophy. The production of IgG2b antibody provided the best correlation for castration. PLGA was considered the most effective adjuvant as it produced a consistent anti-fertility response in all the treated animals.