Comparative evaluation of phenol and thimerosal as preservatives for a candidate vaccine against American cutaneous leishmaniasis

For decades thimerosal has been used as a preservative in the candidate vaccine for cutaneous leishmaniasis, which was developed by Mayrink et al. The use of thimerosal in humans has been banned due to its mercury content. This study addresses the standardization of phenol as a new candidate vaccine preservative. We have found that the proteolytic activity was abolished when the test was conducted using the candidate vaccine added to merthiolate (MtVac) as well as to phenol (PhVac). The Montenegro's skin test conversion rates induced by MtVac and by PhVac was 68.06 percent and 85.9 percent, respectively, and these values were statistically significant (p < 0.05). The proliferative response of peripheral mononuclear blood cells shows that the stimulation index of mice immunized with both candidate vaccines was higher than the one in control animals (p < 0.05). The ability of the candidate vaccines to induce protection in C57BL/10 mice against a challenge with infective Leishmania amazonensis promastigotes was tested and the mice immunized with PhVac developed smaller lesions than the mice immunized with MtVac. Electrophoresis of phenol-preserved antigen revealed a number of proteins, which were better preserved in PhVac. These results do in fact encourage the use of phenol for preserving the immunogenic and biochemical properties of the candidate vaccine for cutaneous leishmaniasis.

Comparative stabilities of glutaraldehyde & heat inactivated pertussis vaccine components of adsorbed DPT vaccine with different preservatives.

The stability of pertussis component (glutaraldehyde or heat inactivated pertussis vaccine) of the adsorbed diphtheria-pertussis-tetanus (DPT) vaccine preserved in thiomersal or benzethonium chloride was studied at 4-8 degrees C and 35 degrees C for 30 days. The potency of pertussis component of adsorbed DPT vaccine preserved with benzethonium chloride was lower than that preserved with thiomersal. After the initial loss of potency of pertussis component in the benzethonium chloride during blending, the stability of potency of pertussis component at 4-8 degrees C and 35 degrees C for 30 days was similar for vaccines preserved with either benzethonium chloride or thiomersal. The stability of both types of pertussis components inactivated with glutaraldehyde or heat was also similar at both the temperatures for 30 days.