[Dynamic changes of serum antibody titer in a rabbit model of Acanthamoeba keratitis].

Ten healthy New Zealand white rabbits were randomly divided into two groups named as experiment group (n=8) and normal control group (n=2). Left eyes were for experiment, right eyes served as control. New Zealand rabbits were each injected by subconjunctival route with hydrocortisone for three days, and then Acanthamoeba keratitis was induced by intrastromal injection of live Acanthamoeba healyi trophozoites and cysts. Eyes in control group were injected with equivalent volume of physiological saline. Corneal lesions of rabbits were recorded every day after injection, etiological diagnosis was carried out by corneal scraping. Blood samples were examined for serum antibody titer by ELISA. Corneas were removed for pathological examination. Corneal scraping and corneal histopathologic examination proved that experiment eyes were infected by Acanthamoeba, and appeared typical manifestations and pathological changes of Acanthamoeba keratitis. Serum antibody titer raised continuously with infection time and reached the highest level (A450 value=2.2358) on the 28th days post-infection, then began to decline and remained higher level than the control until the rabbits were sacrificed. In control group, no significant change in antibody titer had taken place.

Biological characteristics and pathogenicity of Acanthamoeba.

Acanthamoeba is an opportunistic protozoa, which exists widely in nature and is mainly distributed in soil and water. Acanthamoeba usually exists in two forms, trophozoites and cysts. The trophozoite stage is one of growth and reproduction while the cyst stage is characterized by cellular quiescence, commonly resulting in human infection, and the lack of effective monotherapy after initial infection leads to chronic disease. Acanthamoeba can infect several human body tissues such as the skin, cornea, conjunctiva, respiratory tract, and reproductive tract, especially when the tissue barriers are damaged. Furthermore, serious infections can cause Acanthamoeba keratitis, granulomatous amoebic encephalitis, skin, and lung infections. With an increasing number of Acanthamoeba infections in recent years, the pathogenicity of Acanthamoeba is becoming more relevant to mainstream clinical care. This review article will describe the etiological characteristics of Acanthamoeba infection in detail from the aspects of biological characteristic, classification, disease, and pathogenic mechanism in order to provide scientific basis for the diagnosis, treatment, and prevention of Acanthamoeba infection.

Establishment of a CaCC-based Cell Model and Method for High-throughput Screening of M3 Receptor Drugs.

Muscarinic acetylcholine receptor subtype 3 (M3 receptor) is a G Protein-Coupled Receptor (GPCR) that mediates many important physiological functions. Currently, most M3 receptor drugs also have high affinity for other subtypes of muscarinic acetylcholine receptors (mAChRs) and produce the risk of side effects. Therefore, in order to find M3 receptor drugs with high specificity, high activity and low side effects, we established a cell model and method for efficient and sensitive screening of M3 receptor based on calcium-activated chloride channels (CaCCs), and this method is also suitable for the screening of other GPCR drugs. This screening model consists of Fischer rat thyroid follicular epithelial (FRT) cells that endogenously express M3 receptors, CaCCs, and the indicator YFP-H148Q/I152L. We verified that the model can sensitively detect changes in intracellular Ca2+ concentration using fluorescence quenching kinetics experiments, confirmed the screening function of the model by applying available M3 receptor drugs, and also evaluated the good performance of the model in high-throughput screening.

[Research progress on the mechanisms of antigenic variation in Giardia lamblia].

The intestinal protozoan parasite Giardia lamblia is one of the most common causes of diarrhoea and undergoes antigenic variation. In pathogenic microorganisms, antigenic variation is often described as a mechanism to evade the host immune system, resulting in chronic and/or recurrent infections. In the recent years, significant advances in the knowledge of the antigen switching process have been achieved. Here we review the principal knowledge on the mechanisms that regulate this process, including genomic organization, post-transcriptional gene silencing, expressional modifications, and processing and turnover of VSPs.

Construction and characterization of a full-lengh cDNA library from non-fresh Giardia lamblia.

OBJECTIVE: To construct rapidly a full-length cDNA library from nanogram amounts total RNA of Giardia lamblia (G. lamblia) trophozoites stocked in RNA stabilization reagent. METHODS: Total RNA of Giardia was extracted using Trizol reagent. A full-length cDNA library of G. lamblia trophozoites was constructed by a long-distance PCR (LD-PCR) method. The recombinant rate and the coverage rate of full-length clones of the library were evaluated. The inserted fragments were identified and sequenced by PCR amplification. RESULTS: The titer of cDNA library was 3.85 × 10(7) pfu/mL. The length of inserted fragments ranged from 0.4 to 2.5 kb, and the recombination efficiency accounted for 100% (20/20). The coverage rate of full-length clones is high (17/20). CONCLUSIONS: The RNA stabilization reagent may be used to fix the cells and prevent the RNA in cells even though delivered under normal atmospheric temperature. The long-distance PCR can be used to construct a full-length cDNA library rapidly and it needs less RNA than the traditional method from mRNA.