[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.

[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.