In Latin America, the country of Ecuador was one of the first and most severely affected by the COVID-19 pandemic. This study aimed to evaluate the demand for a COVID-19 vaccine in Ecuador by estimating individuals’ willingness to pay (WTP) for the vaccine, and by assessing the effect of vaccine attributes (duration of protection and efficacy) and individuals’ characteristics on this valuation. The sample used (N = 1,050) was obtained through an online survey conducted from April 2 to April 7, 2020. Two levels of vaccine efficacy (70% and 98%) and two levels of vaccine duration of protection (1 and 20 years) were considered. The willingness to pay estimates were obtained using a double-bounded dichotomous-choice contingent valuation format. Survey results show that a very large proportion of individuals (at least 97%) were willing to accept a COVID-19 vaccine, and at least 85% of individuals were willing to pay a positive amount for that vaccine. Conservative estimates of the average WTP values ranged from USD 147.61 to 196.65 and the median WTP from USD 76.9 to 102.5. Only the duration of protection was found to influence individuals’ WTP for the vaccine ( p < 0.01). On average, respondents were willing to pay 30% more for a COVID-19 vaccine with 20 years of protection relative to the vaccine with 1 year of protection. Regression results show that WTP for the vaccine was associated with income, employment status, the perceived probability of needing hospitalization if contracting the virus causing COVID-19, and region of residence.
Granulysin is a protein present in the granules of human cytotoxic T lymphocytes (CTL) and natural killer (NK) cells, with cytolytic activity against microbes and tumors. Previous work demonstrated the therapeutic effect of intratumoral injection of recombinant granulysin using in vivo models of breast cancer and multiple myeloma. In the present work we have developed a granulysin gene fusion to the anticarcinoembryonic antigen (CEA/CEACAM5) single chain Fv antibody fragment MFE23. Both granulysin and the granulysin-based immunotoxin were expressed in Pichia pastoris. The immunotoxin specifically recognized CEA, purified or expressed on the cell surface. Moreover, the bioactivity of the immunotoxin against several CEA + cell lines was higher than that of granulysin alone. Granulysin and the immunotoxin were tested as a treatment in in vivo xenograft models in athymic mice. When injected intratumorally, both granulysin and the immunotoxin were able to inhibit tumor growth. Furthermore, systemic administration of the immunotoxin demonstrated a decrease in tumor growth in a CEA + tumor-bearing mouse model, whereas granulysin did not exhibit a therapeutic effect. This is the first granulysin-based immunotoxin and the present work constitutes the proof of concept of its therapeutic potential.
Granulysin is a protein present in the granules of human cytotoxic T lymphocytes (CTL) and natural killer (NK) cells, with cytolytic activity against microbes and tumors. Previous work demonstrated the therapeutic effect of the intratumoral injection of recombinant granulysin and of the systemic injection of an immunotoxin between granulysin and the anti-carcinoembryonic antigen single-chain Fv antibody fragment MFE23, which were produced in the yeast Pichia pastoris. In the present work, we developed a second immunotoxin combining granulysin and the anti-Tn antigen single-chain Fv antibody fragment SM3, that could have a broader application in tumor treatment than our previous immunotoxin. In addition, we optimized a method based on electroporation by pulsed electric field (PEF) to extract the remaining intracellular protein from yeast, augmenting the production and purificiation yield. The immunotoxin specifically recognized the Tn antigen on the cell surface. We also compared the thermal stability and the cytotoxic potential of the extracellular and intracellular immunotoxins on Tn-expressing human cell lines, showing that they were similar. Moreover, the bioactivity of both immunotoxins against several Tn+ cell lines was higher than that of granulysin alone.
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