Nelda E. Alger

Nosema algerae: Infection of the white mouse by a mosquito parasite

Abstract Spores of Nosema algerae, a microsporidan parasite of mosquitoes, were subcutaneously injected into the ears, tail, and feet of white mice. Infections were transient and localized at the injection sites. Spore germination tests in blood plasma indicated that it is unlikely that spores injected by an infected mosquito bite would result in an infection.

The effect of the microsporidan, Nosema algerae, on Anopheles stephensi

Abstract A bioassay method was established to examine infectivity differences between different batches of Nosema algerae spores. The IC 50 of N. algerae spores produced in one unusual host, Heliothis zea, was the same as for spores from the normal mosquito host, Anopheles stephensi . Soil and sand bottoms caused an approximate 200–400 fold increase in the IC 50 . Nosematosis had little effect on the survival of larvae and pupae but the adult life span was reduced to the extent that malaria transmission would be doubtful.

AXENIC HELMINTH CULTURES AND THEIR USE FOR THE PRODUCTION OF ANTIPARASITIC VACCINES

Research on immunologic resistance of vertebrate animals to metazoan parasites has encompassed a wide variety of infections including cestode, trematode, and nematode parasites. In this presentation, special emphasis is placed on nematode parasites of the families Metastrongylidae and Trichostrongylidae. These helminths parasitize domestic animals and in some cases, man. In general, the parasitic nematodes go through a life cycle involving a free-living stage that takes place in the host’s fecal excrement. Helminth eggs or embryos are passed out in the feces, where they develop and grow, molting twice, into ensheathed third-stage larvae. If the infective third-stage larva is ingested by a suitable host, the larva exsheaths, casting off the extra cuticle retained from the second free-living ecdysis. Inside the host, the larva enters the parastic or histotropic stage and undergoes a further two molts in the host’s tissues or in intimate contact with the intestinal mucosa. After the fourth and final molt, the worm matures, copulates, and eggs are produced and excreted into the host’s intestinal lumen to passed out in the feces. Work of the past thirty years on the mechanism of immunity to infection with parasitic helminths indicates that the sources of antigen and the site of antibody inhibition occur during growth and development of the histotropic stages. More specifically, it has been shown that inhibition of parasite development in resistant hosts is evident at the first, and to a lesser extent, during the second parasitic ecdysis. The functional antigens, which have been incriminated as important stimulants of the host immune response, are apparently elaborated during certain transitory stages (Silverman & Patterson, 1960). The stages which so far have been identified as particularly involved in the immune stimulating process are the molting third to fourth stage and the molting fourth and early fifth (or young adult) stage (Silverman, 1965a). Antigens prepared from these stages obtained by in vivo (Silverman & Patterson, 1960) and in vitro (Silverman, Poynter & Podger, 1962; Silverman, 1965a) means have proved to be effective in inducing resistance to a number of different parasites in animals. Work is presently under way in several laboratories to translate these promising results into practical vaccination procedures in veterinary and human medicine. This paper proposes to deal with some of the problems involved in the large-scale axenic culture of the histotropic stage of helminths for the production of antigen to be used in antiparasitic vaccines.

The control of a microsporidian, Nosema sp., in an anopheline colony by an egg-rinsing technique☆

Abstract An as yet unnamed species of Nosema may be controlled at infection rates of less than 16% in colonies of the mosquito Anopheles stephensi by simply rinsing the eggs with water. The same colony will be destroyed if the eggs are not rinsed. Neither H2O, 1% HCl, nor 1% NaOH killed the spores, whereas overnight exposure to 0.1% formalin, a 20-min exposure to 95% ethanol, or drying for 5 days did kill the spores.

Plasmodium berghei: heat-treated sporozoite vaccination of mice.

Abstract Repeated intravenous (IV) immunizing injections with 25,000 Plasmodium berghei heat-treated sporozoites gave an average protection of 13% in five experiments (0–53%). Four injections of 105 sporozoites gave 50% protection, seven injections of 105 gave 37% protection, and six injections of 105 gave 11% protection. Viable spleen cells (1.2 × 108) from twice challenged immune syngenic mice did not protect naive mice against iv challenge. Six ip injections of the supernatant of Parr Bomb disintegrated sporozoites gave no protection against ip challenge, but 7 ip injections gave 40% protection. Centrifuged pellets from French Pressure Cell-disintegrated sporozoites gave almost no protection either iv, sc, or ip. The supernatant was disc-electrophoresed and compared to normal mosquito heads and salivary glands in order to select sporozoite bands for immunizing injections. Results were discussed with respect to uniformity of antigen batches.

Plasmodium berghei: sporozoite challenge, protection, and hypersensitivity in mice.

Abstract Seruminduced hypersensitivity protected some mice against intraperitoneal (ip) sporozoite challenge but not against intravenous challenge. The injection of serotonin 4 hr prior to challenge destroyed this protection. This protection does not appear to be additive to sporozoite immunization. Protection induced by ip injections of 70 salivary glands per injection appeared to be largely suppressed by prior injection of serotonin. It was concluded that hypersensitivity may possibly be at least partly responsible for protection by injections of 70 salivary glands, but that sporozoite immunity is not primarily due to hypersensitivity.

First parasitic ecdysis of Haemonchus conforfus in vitro without stimulation by carbon dioxide

Abstract Three experiments were performed on infective Haemonchus contortus larvae to determine that in exsheathment counts the greatest variation from the mean in replicate tubes was 6.2 and that exsheathment was already over 60% at 1 hour. A fourth experiment compared various modifications of Earles salt solution with and without NH4Cl, Na2CO3, and gassing with CO2. Neither CO2 gas nor Na2CO3 was required for exsheathment. The ammonium ion enhanced exsheathment when added to Earles salt solution with or without Na2CO3. Exsheathment without stimulation of CO2(HCO3) was related to the “readiness” of the larvae to exsheath dependent on the age of the larvae and the preculture treatment.

Plasmodium berghei: Protection against sporozoites by normal mosquito tissue vaccination of mice

Abstract A/J mice immunized by repeated ip injections of normal mosquito salivary glands or mosquito heads were protected from ip sporozoite challenge but not from iv sporozoite challenge. The pellet from centrifuged salivary glands gave 30% protection, while the supernatant gave 4% protection. Serotonin given 4 hr prior to challenge did not destroy this protection. Mice injected with ground mosquito heads less salivary glands gave 56% protection in spite of the injection of serotonin. It is suggested that a hypersensitive Type 1 reaction may explain a part but perhaps not all of this protection.

Plasmodium berghei: Effect of carrageenan on the course of infection in the A/J mouse

Abstract Seakem-9 calcium carrageenan, a reported anti-macrophage agent, was found to confer partial immunity in mice subsequently challenged with 5 × 10 5 Plasmodium berghei NK65A parasitized erythrocytes. Transient parasitemias and significantly extended survival times were evident in carrageenantreated animals. It was suggested that carrageenan may have enhanced nonspecific cellular immunological mechanisms or affected specific immune reactions through the cytotoxicity to suppressor macrophages.

Haemonchus contortus: somatic and metabolic antigens of third and fourth larval and adult stages.

Abstract Rabbits were immunized with soluble antigens of sonicated infective, exsheathed, fourth larval and adult Haemonchus contortus as well as exsheathing fluid and metabolites. Both cross reacting and non-cross reacting antigens were found by the Ouchterlony technique. The results were correlated with those of previous workers.