ABSTRACT The antigenic potential of seven immunogenic peptides of the dengue virus was evaluated in the sera of patients with dengue confirmed by IgM/IgG serology. Antibodies IgM and IgG against dengue virus peptides were analyzed by ELISA in 31 dengue sero-positive and 20 sero-negative patients. The P5 peptide showed significant IgG immunoreactivity mostly in the sera of patients with dengue without warning signs in comparison with patients with dengue with warning signs, correlating with mild disease. This finding suggests that the low antibody response against P5 epitope could be a risk factor for higher susceptibility to dengue virus infection with warning signs, and that P5 could be a potential antigen for vaccine development.

Giardia duodenalis is one of the most prevalent enteroparasites in children. This parasite produces several clinical manifestations. The aim of this study was to determine the prevalence of genotypes of G. duodenalis causing infection in a region of southeastern Mexico. G. duodenalis cysts were isolated (33/429) from stool samples of children and molecular genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis, targeting the triosephosphate isomerase ( tpi ) and glutamate dehydrogenase ( gdh ) genes. The tpi gene was amplified in all of the cyst samples, either for assemblage A (27 samples) or assemblage B (6 samples). RFLP analysis classified the 27 tpi -A amplicons in assemblage A, subgenotype I. Samples classified as assemblage B were further analysed using PCR-RFLP of the gdh gene and identified as assemblage B, subgenotype III. To our knowledge, this is the first report of assemblage B of G. duodenalis in human clinical samples from Mexico.

The MeOH extract of Cupania dentata bark (Sapindaceae) as well as its hexane, CH2Cl2, EtOAc, and BuOH fractions showed high activity against Giardia lamblia trophozoites (IC50 = 2.12-9.52 μg/mL). The phytochemical study of fractions resulted in the isolation of taraxerone (1), taraxerol (2), scopoletin (3), and two mixtures of steroidal compounds. Taraxerone was the metabolite with the highest giardicidal activity (IC50 = 11.33 μg/mL).

El extracto MeOH de Cupania dentata corteza (Sapindaceae) así como sus fracciones de hexano, CH2C1(2), AcOEt y BuOH mostraron gran actividad contra los trofozoítos de Giardia lamblia (CI50 = 2.12-9.52 μg/mL). El estudio fitoquímico de estas fracciones resultó en el aislamiento de taraxerona (1), taraxerol (2), escopoletina (3) y dos mezclas esteroidales. Taraxerona tuvo la más alta actividad giardicida (CI50 = 11.33 μg/mL).

Protease secretion by Giardia duodenalis trophozoites upon interaction with epithelial cells and its association with the parasite adhesion was studied in co-cultures of parasites with IEC6 epithelial cell monolayers in the presence or absence of protease inhibitors. Proteolytic activity in supernatants from trophozoites was enhanced when they were co-cultured with IEC6 cells. This activity was strongly inhibited by pre-incubation of live trophozoites with E-64 and TPCK and a concomitant inhibition of parasite adhesion to IEC6 cells was observed. These data suggest that trophozoites secrete cysteine-type proteases that play a role in the adhesion of G. duodenalis to epithelial cells.