Camellia sinensis solvent extract, epigallocatechin gallate and caffeine confer trophocidal and cysticidal effects against Acanthamoeba castellanii.

We examined the anti-acanthamoebic efficacy of green tea Camellia sinensis solvent extract (SE) or its chemical constituents against Acanthamoeba castellanii by using anti-trophozoite, anti-encystation, and anti-excystation assays. C. sinensis SE (625-5000 µg/mL) inhibited trophozoite replication within 24-72 h. C. sinensis SE exhibited a dose-dependent inhibition of encystation, with a marked cysticidal activity at 2500-5000 µg/mL. Two constituents of C. sinensis, namely epigallocatechin-3-gallate and caffeine, at 100 µM and 200 µM respectively, significantly inhibited both trophozoite replication and encystation. Cytotoxicity analysis showed that 156.25-2500 µg/mL of SE was not toxic to human corneal epithelial cells, while up to 625 µg/mL was not toxic to Madin-Darby canine kidney cells. This study shows the anti-acanthamoebic potential of C. sinensis SE against A. castellanii trophozoites and cysts. Pre-clinical studies are required to elucidate the in vivo efficacy and safety of C. sinensis SE.

In vitro activity of Camellia sinensis (green tea) against trophozoites and cysts of Acanthamoeba castellanii.

The effect of Camellia sinensis (green tea) on the growth of Acanthamoeba castellanii trophozoites was examined using a microplate based-Sulforhodamine B (SRB) assay. C. sinensis hot and cold brews at 75% and 100% concentrations significantly inhibited the growth of trophozoites. We also examined the structural alterations in C. sinensis-treated trophozoites using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). This analysis showed that C. sinensis compromised the cell membrane integrity and caused progressive destruction of trophozoites. C. sinensis also significantly inhibited the parasite's ability to form cysts in a dose-dependent manner and reduced the rate of excystation from cysts to trophozoites. C. sinensis exhibited low cytotoxic effects on primary corneal stromal cells. However, cytotoxicity was more pronounced in SV40-immortalized corneal epithelial cells. Chromatographic analysis showed that both hot and cold C. sinensis brews contained the same number and type of chemical compounds. This work demonstrated that C. sinensis has anti-acanthamoebic activity against trophozoite and cystic forms of A. castellanii. Further studies are warranted to identify the exact substances in C. sinensis that have the most potent anti-acanthamoebic effect.

Vaccination with Toxoplasma gondii calcium-dependent protein kinase 6 and rhoptry protein 18 encapsulated in poly(lactide-co-glycolide) microspheres induces long-term protective immunity in mice.

BACKGROUND: Toxoplasmosis is a worldwide zoonosis caused by the intracellular parasite Toxoplasma gondii. However, no effective vaccine is yet available. Poly(lactide-co-glycolide) polymers can reduce protein degradation and sustain the release of antigens over a long period, which could generate a long-lasting immune response in vivo. Using a mouse model of toxoplasmosis, we evaluated the protective efficacy of vaccination with two recombinant proteins, which are formulated in biodegradable polymers. METHODS: Two recombinant proteins, rCDPK6 and rROP18, were encapsulated in poly(D,L-lactide-co-glycolide) (PLG), and then injected subcutaneously into Kunming mice. The mice immune responses were evaluated in terms of lympho-proliferation, cytokine expression, and antibodies. The survival of infected mice and brain cyst formation were also evaluated at 6 weeks after challenge with T. gondii RH strain (genotype I) or PRU strain (genotype II). RESULTS: Both protein vaccines induced Th1-biased immune responses, with increased specific antibodies and T cells, high levels of interferon-γ and interleukin 2, and strong lymphocyte proliferative responses. The mice immunized with the various protein vaccines survived slightly longer time than the control groups (P > 0.05) after injection with T. gondii RH strain. There were fewer brain cysts in the mice in all the immunized groups than that in the control groups, and the brain cysts were significantly reduced in mice immunized with proteins + 206, rCDPK6 + PLG and rCDPK6 + rROP18 + PLG (P < 0.05) compared controls. Further comparison of the immune responses to the proteins adjuvanted with PLG or Montanide™ ISA 206 VG 6 weeks after the last immunization revealed that antigens encapsulated in PLG conferred greater protective immunity against challenge. CONCLUSIONS: These findings suggest that the two recombinant T. gondii proteins encapsulated in PLG conferred immunity to T. gondii for an extended period, providing the foundation for the further development of a commercial vaccine against toxoplasmosis.

Co-administration of interleukins 7 and 15 with DNA vaccine improves protective immunity against Toxoplasma gondii.

Toxoplasma gondii is an obligatory intracellular parasite, which can infect all warm-blooded animals including humans. Cytokines, including IL-15 and IL-7, play a critical role in the regulation of the homeostasis of naive and memory T cells. Co-administration the DNA vaccine with cytokines may improve its efficacy. IL-7 and IL-15 from splenic tissues of Kunming mice were cloned, and eukaryotic plasmid pVAX-IL-7-IL-15 was constructed. Kunming mice were administrated with DNA vaccine expressing T. gondii calcium-dependent protein kinase 1 (TgCDPK1), pVAX-CDPK1, in the presence or absence of IL-7 and IL-15 plasmids (pVAX-IL-7-IL-15), immune responses were analyzed including lymphoproliferative assay, cytokine and serum antibody measurements, flow cytometric surface markers on lymphocytes, and thus protective immunity against acute and chronic T. gondii infection was estimated. Mice injected with pVAX-CDPK1 supplemented with pVAX-IL-7-IL-15 showed higher Toxoplasma-specific IgG2a titers, Th1 responses associated with the production of IFN-γ, IL-2 as well as cell-mediated cytotoxic activity where stronger frequencies of IFN-γ secreting CD8+ and CD4+ T cells (CD8+/CD4+ IFN-γ+ T cells) compared to controls. Co-administration of pVAX-IL-7-IL-15 and pVAX-CDPK1 significantly (P < 0.05) increased survival time (18.07 ± 5.43 days) compared with pVAX-CDPK1 (14.13 ± 3.85 days) or pVAX-IL-7-IL-15 (11.73 ± 1.83 days) alone, and pVAX-IL-7-IL-15 + pVAX-CDPK1 significantly reduced the number of brain cysts (73.5%) in contrast to pVAX-CDPK1 (46.0%) or pVAX-IL-7-IL-15 alone (45.0%). Our results indicate that supplementation of DNA vaccine with IL-7 and IL-15 would facilitate specific humoral and cellular immune responses elicited by DNA vaccine against acute and chronic T. gondii infection in mice.

Major trends in human parasitic diseases in China.

Tremendous progress has been made in the control and prevention of human parasitic diseases in mainland China in the past 30 years because of China's Reform and Opening to the Outside Policies initiated in 1978. However, parasitic diseases remain a major human health problem, with significant morbidity and mortality as well as adverse socioeconomic consequences. Although soil-transmitted parasitic diseases are in the process of being gradually controlled, food-borne parasitic diseases and emerging parasitic diseases are becoming the focus of new campaigns for control and prevention. This article reviews major trends in human parasitic diseases in mainland China, with perspectives for control.

Evaluation of the adjuvant properties of Astragalus membranaceus and Scutellaria baicalensis GEORGI in the immune protection induced by UV-attenuated Toxoplasma gondii in mouse models.

Human vaccines are not available and current anti-toxoplasma treatment is disappointing. To investigate the possible adjuvant effect of aqueous extracts obtained from medicinal herbs of Astragalus membranaceus (Am) and Scutellaria baicalensis GEORGI (Sb) on the immune response to Toxoplasma gondii in the mouse models induced by ultraviolet (UV)-attenuated T. gondii, this paper studies the possible vaccination strategies to help combat infections with Toxoplasma and looking towards developing new vaccine and approaches. We used UV-attenuated T. gondii (UV-T.g) of RH strain as a vaccine and the extracts of Am (AmE) and Sb (SbE) as adjuvant. Mice were infected by intraperitoneal (i.p.) injection of 10(2) RH tachyzoites alone (infected controls), infected and treated with AmE (T.g+AmE) and SbE (T.g+SbE), respectively; and mice immunized i.p. with UV-T.g alone, UV-T.g co-administrated with AmE (UV-T.g+AmE) or SbE (UV-T.g+SbE), and then challenged with T.g, respectively. The animal survival time, parasite burden in peritoneal lavage fluids, liver histopathological analysis, and levels of serum antibodies among the groups were compared after either infection or challenge. The results showed that, compared to infected controls, infected mice treated with AmE or SbE, or vaccinated mice and then challenged, had significantly prolonged survival time, decreased parasite burden, improved liver histopathological score, and increased Th1-type cellular immune response; furthermore, vaccinated mice co-administrated with AmE or SbE had even longer survival, lower parasite burden, lower liver histopathological score, and higher Th1 response after challenge. Our data demonstrated that the protective immunity of UV-attenuated T. gondii could be markedly enhanced by AmE or SbE co-administration, which suggests that both AmE and SbE may have the potential to be used as effective vaccine adjuvant.