ABSTRACT
Objective: To evaluate the expression of DNA plasmid-harboring modified antibody gene that produces neutralizing human monoclonal antibodies against four serotypes of dengue virus (DENV) without enhancing activity in BALB/c mice. Methods: We constructed pFUSE-based vectors (pFUSE-1G7C2-hVH and pFUSE-1G7C2-hVL) containing genes encoding the variable domains of the heavy or light chain of the anti-dengue virus antibody 1G7C2, a human IgG1 that has been characterized for its neutralizing activity to DENV-1-4. Leucine (L) at positions 234 and 235 on the Fc CH2 domain in pFUSE-1G7C2-hVH was mutated to alanine (A) (LALA mutation) by site direct mutagenesis, and the new plasmid was termed pFUSE-1G7C2-hVH-LALA. An equal amount of pFUSE-1G7C2-hVL and 1G7C2hG1-LALA plasmids were co-Transfected into Chinese hamster ovary cells (CHO-K1) and a single dose of 100 μg 1G7C2-hG1-LALA plasmid was intramuscularly injected, followed by electroporation in BALB/c mice. The secreted 1G7C2-hG1-LALA antibodies in cell culture supernatant and mouse serum were examined for their biological functions, neutralization and enhancing activity. Results: The co-Transfection of heavy-And light-chain 1G7C2-hG1-LALA plasmids in CHO-K1 cells produced approximately 3 900 ng/mL human IgG and neutralized 90%-100% all four DENV, with no enhancing activity. Furthermore, the modified human IgG was produced more than 1 000 ng/mL in mouse serum on day 7 post plasmid injection and showed cross-neutralization to four DENV serotypes. Subsequently, antibody production and neutralization decreased rapidly. Nevertheless, the secreted neutralizing 1G7C2-hG1-LALA in mouse serum demonstrated complete absence of enhancing activities to all DENV serotypes. Conclusions: These findings reveal that a new modified 1G7C2-hG1-LALA expressing plasmid based on gene transfer is a possible therapeutic antibody candidate against DENV infection.
ABSTRACT
A survey of Strongyloides stercoralis infection was conducted in 11 southern provinces of Thailand by agar-plate culture technique. A total of 1,308 stool samples were collected by 30-cluster sampling technique during July-August 2007. The results revealed that the overall prevalence of S. stercoralis in the study areas was 20.6% and the intensity was mostly low. The highest infection rate was found in Phatthalung Province (29.9%), and the lowest in Phuket Province (7.5%). The highest positive finding was among the group aged 60 years and over (28.5%), and the rate of infection was comparatively high among males (25.4%). At cluster or village level, the highest infection rate was 51.9% in Ban Don Gun Village, Nakhon Si Thammarat Province, and the lowest 2.3% in Ban Yang Mark Village, Trang Province. The results of the surveillance showed that a majority of the population had high trongyloidiasis-related risk behaviors–poor hygiene and inappropriate footwear behaviors, such as wearing open sandals, so that 89.9% had an enhanced risk of infection, and only 22.2% wore casual shoes. Only 24.1% habitually wore boots when they worked in the paddy field, with the remaining 75.9% at higher risk of infection. However, it was also instructive to learn that the proportion of people who routinely washed fresh vegetables thoroughly before eating, to prevent larval contamination, was quite high (94.4%). Almost all (96.0%) of the people habitually defecated in a sanitary latrine when at home; however, when they worked in the field, the rate was far lower, at only 37.7%. It was interesting to find that 11.6% of the people habitually defecated outside a latrine, on the ground, while about 50.1% sometimes defecated on the ground, which would also result in a higher risk of the spread of disease. The information obtained from the behavioral survey also showed that high-level risk behaviors for the transmission of strongyloidiasis in southern Thailand, where potential hosts do exist, higher than the previously reported data about the prevalence of S. stercoralis infection. Proactive health education and empowerment of the community are recommended to control strongyloidiasis, and so prevent health problems among the people in such areas.