Duration of immunity following a single vaccination with irradiated sporozoites of Plasmodium berghei

A rodent model of sporozoite immunization against malaria based on a single immunizing dose is described. The duration of protective immunity was measured as a function of dose, and the results suggest that the percentage of protection follows a bimodal distribution. The first peak occurs between days 7-12 after immunization, while the second peak occurs at approximately 28 days. Although the percentage of protection declines steadily after the second peak, some immunity was detectable as long as 140 days after immunization with the higher doses.

The use of membrane screen filters in the isolation of Plasmodium berghei sporozoites from mosquitos

An improved procedure is presented for the isolation of Plasmodium berghei sporozoites from host mosquitos. The method employs filtration through a series of Nuclepore membranes followed by two consecutive centrifugations of the filtrate layered over Renografin-60 solutions of different densities. A Coulter Counter was used to compare isolations prepared by this technique with those prepared by a routinely employed discontinuous gradient method. When the sporozoite concentration in each preparation was standardized at 300 sporozoites per ml, isolations prepared by the new technique were significantly cleaner than isolations prepared by the discontinuous gradient method, containing an average of 1706 total particles per ml compared with 46 107 total particles per ml. The latter procedure was more effective, however, in removing viable microorganisms. Sporozoites isolated by both techniques were similar in immunogenicity and virulence.

Bancroftian filariasis and membrane filters: are night surveys necessary?

Paired day and night blood specimens from 41 persons living in a hyperendemic Wuchereria bancrofti area of southwestern Ethiopia were examined for microfilariae by Nuclepore filter, thick film, and counting chamber techniques. Filtering techniques were so highly sensitive that more infected persons were identified by filtering day blood than by examining night blood by conventional methods. Increasing the volume of blood filtered from 1 ml to 5 ml increased the number of positives identified during the day. Filtering 5 ml of day blood obviated the need for examining night blood, even though a high proportion of infected persons had very low numbers of circulating microfilariae.

The use of penicillamine as an adjuvant to tartar emetic in the treatment of experimental schistosomiasis

One of the principal drawbacks of antimonial therapy in schistosomiasis has been the prevalence of annoying, and sometimes dangerous, side-effects. The adjuvant administration of chelating agents offers a possible solution to this problem, providing this can be achieved without appreciably decreasing the therapeutic effect of the drug.The authors found that the chelating agent penicillamine lowered the toxicity of tartar emetic for mice and hamsters without affecting the tissue uptake of antimony. When administered in a similar manner to hamsters infected with Schistosoma mansoni there was no effect on the uptake of antimony by the parasites, or on the cure rate. This suggests a potential usefulness of penicillamine in antimony therapy.