Precipitin responses of infected mice to exoantigens and cellular antigens of Trypanosoma musculi.

Plasma were collected from mice which had been immunosuppressed with 650 R from a cobalt-60 gamma radiation source and infected with Trypanosoma musculi. Trypanosomes were also collected from immuno-suppressed mice and from nonirradiated, infected animals. Rabbit antiserum was prepared against trypanosomes fron nonirradiated mice and employed in immunodiffusion analyses to detect trypanosome exoantigens (ExAg) in plasma of irradiated, infected mice and cellular antigens (CAg) in extracts of parasites which had been collected from immunosuppressed and nonirradiated hosts. The rabbit antiserum formed at least 3 precipitin lines with plasma from irradiated, infected mice and 8–9 precipitin lines with extracts of parasites which were obtained from immunosuppressed and untreated mice. Two of the precipitin reactions were against mouse plasma antigens (PAg). Lower levels of PAg appeared to be present in extracts of trypanosomes which were isolated from the irradiated mice than in those from nonirradiated animals.Mice synthesized antibodies against 1 ExAg which was demonstrable in immunodiffusion tests by 14 days after T. musculi infection. A single precipitin reaction was also seen after 21 days. One to 2 precipitin lines were formed with ExAg after 42 days of infection. Two to 3 precipitin lines formed between the ExAg and mouse antisera collected 98, 175 and 341 days after injection of the T. musculi.Similar immunodiffusion reactions were detected with CAg present in both the extracts of T. musculi which had been isolated from irradiated and those from nonirradiated mice and the mouse antisera. One to 2 precipitin lines were found between CAg and antisera from mice which had been infected for 14 days. Two precipitating antigen-antibody systems were seen with antisera collected after 21, 42 and 98 days and 2–3 precipitin reactions were formed between CAg and antisera collected from mice 175 and 341 days after infection.Absorption and immunodiffusion analyses conducted with rabbit and mouse antisera indicated parasite ExAg in plasma of irradiated, T. musculi infected mice were also present in preparations of CAg of the trypanosomes. The persistence of antibody and the increase in the numbers of antigen-antibody systems detected by immunodiffusion during the course of the infection may in part be related to the presence of parasites in capillaries of the kidneys long after they cannot be demonstrated in the peripheral blood of the host.     

Trypanosoma lewisi: ultrastructural observations of surface antigen movement induced by antibody.

Cellular antigens of Trypanosoma lewisi have been located with ferritin-conjugated antibody (FCA) at the ultrastructural level. Incubation of live T. lewisi with antibodies from infected rats and ferritin-labeled rabbit anti-rat γ-globulin induced aggregation of surface antigens in the flagellar pockets, the desmosomal regions, and the flagellar membranes of parasites. Aggregation of surface antigens was not observed when the trypanosomes were incubated with γ-globulin and FCA at low temperatures (0–4 C). Sections of trypanosomes incubated at 37 C for 15 or 30 min after incubation at 0 C with FCA showed internalization of FCA in membrane-bound vesicles. Studying the movement and aggregation of these parasites' surface antigens may give information about the molecular dynamics of the plasma membrane and provide insights into the trypanosomes' antigenic modulation and the hosts' immunological responses.     

Trypanosoma brucei: influence of host strain and parasite antigenic type on infections in mice

Inbred mice were infected with cloned populations of Trypanosoma brucei brucei Lister S42 under carefully controlled conditions. The course of infection was found to depend both on host strain and the antigenic type of the infecting organisms. The two antigenic types used, “NIM2” and “NIM6” had differing virulence for (CBA/H × C57BL/6)F₁ mice, and when mice were infected with parasites of one clone, trypanosomes of the other type frequently appeared after the initial population had been eliminated. Different mouse strains had varying susceptibility to clone NIM6. In most cases there was an inverse relation between the survival time and the parasite load during the first peak of parasitemia. The differences in resistance to T. brucei were unrelated to H-2 haplotype: C57BL/6 and (CBA/H × C57BL/6)F₁ were most resistant, CBA/H, BALB/c and DBA/2 less so, and C3H/He most susceptible.     

Trypanosoma lewisi: antibody classes which mediate precipitation, agglutination, and the inhibition of reproduction

Sera from Trypanosoma lewisi-infected and uninfected rats were applied to Protein A-Sepharose CL-4B columns. The absorbed fractions of antisera which contained only IgG molecules were reacted in microimmunodiffusion analyses with the exoantigens of T. lewisi in plasma collected from irradiated infected rats, and formed one precipitin line. These sera were also applied to T. lewisi extract immunoabsorbent columns and bound proteins were eluted and analyzed by immunodiffusion against antisera specific for rat immunoglobulins. IgG₁, IgG_2a, IgG_2b, IgG_2c, and IgM were absorbed by the immuno-absorbent columns. Absorption of the rat antisera with anti-rat IgG or anti-rat IgM removed one of the two precipitin lines against extracts prepared from parasites collected from irradiated infected animals. The absorbed IgG fractions and nonabsorbed fractions of antisera which were collected after Protein A-Sepharose CL-4B column chromatography agglutinated trypanosomes. After treatment of antisera with 2-mercaptoethanol, the agglutinin titers were lower than those of the control antisera suggesting both IgG and IgM are involved in the agglutination. The ablastic activity of the fractions eluted from Protein A-Sepharose CL-4B Chromatographic columns was assayed in cultures of bloodstream forms ofT. lewisi. Ablastic activity of proteins of antisera absorbed by the columns was demonstrated indicating they belonged to the IgG class of antibodies.     

Ascaris suum: suppression of reaginic and hemagglutinating antibody responses in the mouse by crude extract and maintenance fluid.

Intraperitoneal administration in mice of crude extract (CE) or maintenance fluid (MF) of Ascaris suum in Freund's incomplete adjuvant (FICA) in doses of 200 and 2 (CE) and 4 μg (MF) on Days ?4, 0, and +4 relative to the day of the immunization with 10 μg of hen egg white lysozyme (HL) resulted in the suppression of anti-HL reaginic antibody responses at varying degrees depending on the dose and their time of administration. Hemagglutinating antibody responses were also affected but in a different manner. Treatment with CE on Day ?4 resulted in complete suppression of reaginic antibody responses and some degree of suppression of hemagglutinating antibody responses depending on the size of the CE dose. In mice pretreated with MF, transient suppression was found only for reaginic antibody responses. In mice receiving the treatment of CE on Day 0, 200 μg of CE caused complete suppression of reaginic antibody responses, while 2 μg was less effective. Hemagglutinating antibody responses were also suppressed in proportion to the dose. Simultaneous treatment with MF did not cause any suppression of either reaginic or hemagglutinating antibody responses. In mice treated with CE on Day +4, reaginic antibody responses were not markedly suppressed and hemagglutinating antibody responses were also not altered. In contrast, treatment with MF on Day +4 resulted in suppression of reaginic antibody responses during the whole course of the primary response, but had no effect on hemagglutinating antibody responses. When MF was administered 7 days after the priming, no suppressive effect on the antibody responses was demonstrated. On the other hand, if a lower dose (1 μg of HL) was used for the priming, the effect of MF treatment with Day +4 was more pronounced in the primary reaginic antibody response and the secondary response was also affected. A comparable suppression of hemagglutinating antibody responses also was observed.     

Trypanosoma cruzi: acetylcholine content and cholinergic innervation of the heart in rats.

The acetylcholine content, as well as the density and distribution of cholinergic innervation were studied in the hearts of rats after inoculation with the Y strain of Trypanosoma cruzi. Cholinergic innervation was studied by histochemical techniques using acetylcholinesterase in the sinoatrial node, in fragments of the right atrium and auricular appendages. Acetylcholine was assayed on a strip of guinea pig ileum suspended in Tyrode's solution. Twenty days after inoculation, the cardiac content of acetylcholine dropped 40% and the cholinergic innervation was markedly reduced in 80 to 100% of the rats. However, at 70 and 97 days the cardiac content of acetylcholine was not different from that of the controls. The cholinergic innervation in the heart of the animals sacrificed 98 and 180 days after inoculation was normal in 60 to 66% of the rats. The results indicate that the cardiac parasympathetic innervation is damaged during the acute phase of experimental Chagas' disease, but returns to normal during the chronic phase in most animals.     

Trypanosoma cruzi: location of a specific antigen on the surface of bloodstream trypomastigote and culture epimastigote forms.

The nature of surface antigens of culture epimastigote and bloodstream trypomastigote forms of Trypanosoma cruzi was investigated by light and electron microscopy using indirect immunofluorescence and peroxidase labeling techniques and antisera against unique, common, and contaminant antigens. A specific antigen, identified by monospecific rabbit antiserum (anti-component 5 antiserum), is the major constituent of the cell surface and flagellar membrane of both the culture epimastigote and bloodstream trypomastigote forms. Antigens of heterologous stercorarian trypanosomes (Trypanosoma rangeli) and of culture medium proteins could not be detected on the cell surface of culture epimastigote forms and bloodstream trypomastigote forms.