Trypanosoma musculi and Trichinella spirails: Concomitant infections and selection for resistance genotypes in mice

Trypanosoma musculi infections were given to mice of different strains before, at the same time, and after an infection with 400 Trichinella spiralis. Examined parameters of the host response to T. spiralis were worm rejection, antifecundity responses, development of immunological memory, and muscle larvae burden. After dual infection, each mouse strain showed characteristic effects on resistance to T. spiralis. This was due to a dynamic interaction between the genes controlling rejection of T. spiralis and those influencing T. musculi growth. C3H mice develop high trypanosome parasitemias. This impairs worm expulsion and the development of memory to T. spiralis when Trypanosoma infections take place on the same day or 7 days before. The C57B1/6 mouse develops low parasitemias and T. musculi infections on the same day, or 7 days before T. spiralis, delaying worm rejection only slightly despite the overall weak capacity of B6 mice to expel worms. NFR-strain mice are strong responders to T. spiralis and also develop low parasitemias. Trypanosome infections on the same day, or after T. spiralis, produce a delay in worm rejection; the former is comparable to C3H mice. However, NFR mice alone showed enhanced rejection of worm when T. musculi infections preceded T. spiralis by 7 days. An unusual feature of C3H mice was that T. musculi infections 7 days before T. spiralis increased antifecundity responses at the same time that worm expulsion was inhibited. Trypanosome infections can therefore modulate distinct antihelminth immune responses in different directions simultaneously. The different outcomes of dual infections compared with single infections provides another selective mechanism by which genetic polymorphisms can be established and maintained in the vertebrate host.     

Immune responses to Trichinella pseudospiralis and Trichinella spiralis in mice

Primary infections with Trichinella pseudospiralis and Trichinella spiralis were followed in rapid- (NIH) and slow- (B10G) responder strains of mice. Expulsion of T. pseudospiralis was slower in both strains, but markedly so only in slower responder B10G mice. Blast cell activity in the mesenteric lymph nodes of the mice correlated with the expulsion patterns. In NIH mice, both parasites stimulated a strong response by day 8 of infection and activity had returned to control levels by day 11. In B10G mice, T. spiralis elicited an earlier peak response (day 12) than T. pseudospiralis (day 18), but in both, activity returned to control levels by day 21. Immunity to T. pseudospiralis and T. spiralis could be stimulated in NIH mice by prior infection with either parasite, by injection of T. spiralis larval antigen and by adoptive transfer of immune mesenteric lymph node cells taken from mice infected with either parasite. This extensive cross reactivity, and the differences seen during primary infections, are discussed in relation to the biology and specific identity of the two worms.     

Comparison of rapid expulsion of Trichinella spiralis in mice and rats

Alizadeh H. and Wakelin D. 1982. Comparison of rapid expulsion of Trichinella spiralis in mice and rats. International Journal for Parasitology12: 65–73. Primary infections of Tricliinella spiralis in both NIH mice and Wistar rats resulted in increased levels of mucosal mast cells and goblet cells. In mice the numbers of both cell types rose sharply before worm expulsion (days 8–10), remained at an increased level for a short time and declined quickly, reaching control levels on day 14 for goblet cells and between days 28 and 35 for mast cells. In contrast, in rats, the numbers of goblet cells and mast cells increased during worm expulsion and remained above control levels for a prolonged period. Challenge infections given shortly after expulsion of a primary infection (day 14) were expelled rapidly, worm loss being virtually complete with 24 h. In mice this response to challenge was short-lived and persisted only until day 16 after primary infection. After this time, challenge worms were expelled more slowly after infection. In rats the rapid expulsion response was expressed for at least 7 weeks after primary infection. Mice and rats showed differences in the conditions of infection necessary to prime for rapid expulsion, mice requiring larger and longer duration primary infections, but the expression of the response appeared to be similar in both species. In mice it was shown that rapid expulsion of T. spiralis was a response evoked specifically by prior infection with this species; infections with other intestinal nematodes had no effect. Similarly, the effect upon challenge infection was also specific to T. spiralis. The rapidity with which challenge infections are expelled suggests that either the specific inflammatory changes generated during primary infection result in an environment that is unsuitable for establishment of subsequent infections or that challenge infections provide a stimulus that can provoke an almost instantaneous response in the primed intestine. The relationship of the observed cellular changes to such mechanisms is discussed.     

Effect of host sex on passive immunity in mice infected with Nematospiroides dubius

Dobson C. & Owen M. E. 1978. Effect of host sex on passive immunity in mice infected with Nematospiroides dubius. International Journal for Parasitology8: 359–364. Female C₃H but not Quackenbush (Q) mice harboured fewer Nematospiroides dubius than male C₃H and Q mice. Both strains lost worms 21 days after infection. C₃H and Q mice became progressively immune to infection following 4 sequential doses of N. dubius larvae and showed a sex resistance to infection. Hypothymic nu/nu CBA Balb/c mice did not show these effects on N. dubius infection. The reciprocal transfer of male and female immune mesenteric lymph node cells (IMLNC) to syngeneic male and female recipients showed that the female environment enhanced the protective qualities of both male and female IMLNC but the male environment suppressed these effects. Gonadectomized male and female recipients of male and female IMLNC had levels of infection similar to the entire female recipients. Serum from immune female donor mice protected both male and female recipients better than immune serum from male donors, but female mice in each treatment group were better protected than male mice. Immune serum transferred greater levels of protection then IMLNC to recipient mice against N. dubius infections. These data are consistent with the conclusion that the male environment suppresses lymphocyte activity and the production of protective antibodies and additionally may depress the effectiveness of sensitized lymphocytes and antibodies in ejecting N. dubius. On the other hand the female environment does not appear to adversely affect the mobilization of the protective immune response and may enhance immune effector mechanisms in protecting mice against N. dubius infections.     

Trichinella spiralis and Strongyloides ratti: immune interaction in adult rats.

The consequences of prior and concurrent infection with two species of nematodes were studied in rats. Primary infection with Strongyloides ratti adversely affected the development of a secondary Trichinella spiralis infection. Both immediate and delayed challenge with T. spiralis, following the expulsion of the previous S. ratti infection, reduced the percentage of worm recovery of the former as well as their fecundities and lengths. It is suggested that nonspecific inflammation produced by one species, during the peak period of worm expulsion, was not responsible for the accelerated rate of expulsion of the other; instead a direct, specific cross-immunity was probably operative affecting the survival of the challenge species. The response elicited by previous experience of the intestinal phase was reciprocal, but there was evidence of an enhancing effect by the muscle larval stages of T. spiralis on S. ratti. Rats concurrently infected with both species expelled S. ratti more rapidly than T. spiralis. Possible mechanisms underlying the interaction between the two species are suggested and discussed.     

Nematospiroides dubius: arrested development of larvae in immune mice.

When immune NIH mice were killed 10 days after a challenge infection with Nematospiroides dubius, approximately 10% of the inoculated larvae were recovered from the intestinal lumen, irrespective of the dose administered. When such mice were treated with cortisone from Day 10 for a period of 8 to 14 days and were subsequently killed for worm counts, it was found that they had significantly more worms than the immune control mice killed on Day 10. During the week following the beginning of treatment with cortisone there was little change in the low worm burdens in immune mice. However, 9 to 11 days after this treatment worm counts indicated that worms were accumulating in the intestinal lumen, and concurrently eggs were recorded in the feces of the mice. These observations indicated that a period of 9 to 11 days was required after the initiation of cortisone treatment on Day 10 for the worms in immune mice to complete their development to the adult lumen-dwelling stage. It is suggested that the larvae in the challenge infection became arrested early in their development in the intestinal wall and that growth resumed only after cortisone treatment. When treatment with cortisone was initiated later after challenge, it was still effective in reactivating arrested worms, but the lower worm recoveries in these mice indicated that the arrested larvae were being slowly rejected by the host. In subsequent experiments it was established that the arrested larvae of N. dubius were insusceptible to the activity of pyrantel embonate, an anthelmintic which is 99% effective against adult worms in the intestinal lumen. The mechanism whereby the larvae of N. dubius became arrested in immune mice and subsequently resumed their development after cortisone treatment is discussed.     

Trichinella spiralis: Characterization and strain distribution of rapid expulsion in inbred mice

Appropriately immunized mice display a response that is biologically equivalent to rat rapid expulsion. Only two inbred strains ($\text{NFR}\text{N}\text{and}\text{NFS}\text{N}$ derived from NIH Swiss mice) have been shown to respond in this manner. Mice of the $\text{Balb}\text{c}$, CBA, $\text{A}\text{He}$, C₃H, SJL, or C₅₇Bl strains are “nonresponders” which require approximately twice as much intestinal exposure (in days) to Trichinella spiralis to elicit a response half as effective. Genetically, the responder is dominant, autosomal, and does not appear to be linked to the MHC. The characteristics of mouse and rat rapid expulsion of T. spiralis are not identical but share these features: initial rejection within 24 hr of challenge; a rejection efficiency >90%, from 1 to 5 weeks after the primary; induction of response does not require exposure to the complete infection; rapid expulsion is immunologically specific for preadults; adult worms are resistant. While a genetic basis for responsiveness exists in mice there is, as yet, no evidence for genetic control in rats. In both mice and rats, rapid expulsion is distinguished from the intestinal hyperreactivity associated with rejection of the primary infection by the kinetics and amplitude of the rejection of transplanted adult worms.     

Nematospiroides dubius: Mechanisms of host immunity: II. Skin testing and immunosuppression of orally or subcutaneously sensitized mice

The present study was designed to acquire further understanding of the differences in the immune response of mice orally (OS) or subcutaneously (SS) sensitized to Nematospiroides dubius. Two immunosuppressive agents and skin tests were utilized in this regard.Rabbit antimouse thymus serum (RAMTS) and cyproheptadine (antihistamine-antiserotonin) were similarly effective in suppressing the immune response of subcutaneously sensitized mice. When compared to normal rabbit serum and SS control (sensitized, untreated) animals, observations of the intestinal tunica muscularis in the immunosuppressed SS groups revealed granulomatous lesions in which fewer eosinophils enveloped the sequestered parasite. Cyproheptadine was more successful than the other treatments in interrupting the immune expulsion of N. dubius from orally sensitized mice, but this was only at a borderline significance level.The size and intensity of the active cutaneous anaphylactic skin tests in OS mice injected with an adult or larval antigen, was greater than the response elicited in SS mice or uninfected control mice injected with the same preparations. Similarly, the reaction in subcutaneously sensitized mice exceeded that observed in the noninfected controls.     

Effects of Toxoplasma gondii (Gleadle strain) on the host-parasite relationship in trichinosis.

The effects of concurrent infection with Toxoplasma gondii on the host-parasite relationship in trichinosis were studied. Infected mice showed a delay in expulsion of Trichinella spiralis adults from the gut. Persisting adult female worms were fecund but the numbers of larvae recovered from the muscles were not increased. Increased resistance to the systemic phase of trichinosis was shown by reduced numbers of muscle larvae after intravenous injection of newborn larvae in animals with toxoplasmosis as compared with control mice. There were no differences in small bowel pathology of trichinous mice with and without toxoplasmosis but inflammation around muscle cysts of T. spiralis was reduced in mice with toxoplasmosis. The eosinophilia which normally develops in mice with trichinosis was suppressed by concurrent toxoplasmosis. Trichinella infection did not alter the numbers of T. gondii cysts recovered from the brain 4 weeks after infection. It is suggested that the delay in expulsion of adult worms, decrease in muscle inflammation around T. spiralis cysts, and inhibition of eosinophilia result from immune suppression, while the reduction in numbers of muscle larvae after intravenous injection of newborn larvae reflects enhanced nonspecific resistance to infection in toxoplasmosis.     

Influence of primary infection on the population dynamics of Nematospiroides dubius after challenge infections in mice

Dobson C., Sitepu P. and Brindley P. J. 1985. Influence of primary infection on the population dynamics of Nematospiroides dubius after challenge infections in mice. International Journal for Parasitology15: 353–359. Similar proportions of the inoculum of Nematospiroides dubius larvae reached sexual maturity by 14 days after administration of 50–400 larvae but more adult worms had been expelled by day 63 after infection from those mice infected with 50 vs 400 larvae. There was a significant correlation between time and worm expulsion for all inoculum size groups except for mice given 400 larvae.In mice reinfected with 100 larvae, after termination of primary infections derived from 10 through 400 larvae, more worms from the challenging dose were recovered from mice given greater compared with those given smaller numbers of larvae at primary infection. The N. dubius population size after challenge infection was correlated positively both with number of larvae administered as the primary infection and with the resultant population size during that infection. The serum anti-N. dubius antibody titres after reinfection were higher in mice given 400 compared with those given fewer larvae at primary infection, and the fecundity and female to male sex ratio of the N. dubius populations decreased in proportion to these antibody titres.Protective immunity against challenge N. dubius infection, in mice which had been drenched free of adult worms established from 400 larvae for 5 down to 1 weeks before reinfection, increased from 45% (1 week) to 80% (5 weeks). There was a negative correlation between the population size of N. dubius during challenge infection and the duration between anthelmintic treatment and challenge infection.     

Trichinella spiralis: mediation of the intestinal component of protective immunity in the rat by multiple, phase-specific, antiparasitic responses.

Rats infected orally with Trichinella spiralis developed an immunity that was induced by and expressed against separate phases of the parasite's enteral life cycle. Infectious muscle larvae generated an immune response (rapid expulsion) that was directed against the very early intestinal infection and resulted in the expulsion of worms within 24 hr. This response eliminated more than 95% of worms in an oral challenge inoculum. Developing larvae (preadults) also induced an immune response that was expressed against adult worms. The effect on adults was dependent upon continuous exposure of worms to the immune environment throughout their enteral larval development. Immunity induced by preadult T. spiralis was not expressed against adult worms transferred from nonimmune rats. While adult worms were resistant to the immunity engendered by preadults they induced an efficient immunity that was autospecific. Both “preadult” and “adult” immunities were expressed in depression of worm fecundity as well as in the expulsion of adults from the gut. However, the two reactions differed in respect to their kinetics and their efficiency against various worm burdens. Preadult immunity was directed mainly against fecundity whereas adult immunity favored worm expulsion. All responses (rapid expulsion, preadult and adult immunity, and antifecundity) acted synergistically to produce sterile immunity against challenge infections of up to 5000 muscle larvae. These findings indicate that the host protective response to T. spiralis is a complex, multifactorial process that operates sequentially and synergistically to protect the host against reinfection.     

Trichinella spiralis: effects on the host-parasite relationship in mice of BCG (attenuated Mycobacterium bovis).

The effects of BCG (Bacillus Calmette-Guérin, i.e., attenuated Mycobacterium bovis) on the host-parasite relationship in murine trichinosis were examined. A total of 2 × 10⁷ colony forming units of BCG given iv 1 week prior to Trichinella spiralis infection delayed the expulsion of adult worms from the gut. The suppression of adult worm elimination was proportional to the dose of BCG given. This finding was associated with a reduction in the degree of partial villous atrophy induced in the small bowel by T. spiralis. Adult female worms were fecund when they were examined 1, 2, and 3 weeks after infection of mice with T. spiralis. Despite the prolongation of fecund adult worms in the gut, there were no significant differences in muscle larval counts 4 and 6 weeks after infection. When newborn larvae were cultivated in vitro and injected iv, there was a significant 25% reduction in larval numbers recovered from the muscles of BCG-treated mice 4 weeks later. The administration of BCG had no effect on the inflammatory reaction around larvae in the muscles 4 and 6 weeks after infection. It is concluded that BCG alters the host-parasite relationship producing retention of adult worms in the gut, reduction in the severity of partial villous atrophy, and increased nonspecific resistance to the systemic larval phase of this parasite.     

Immunity to Trichinella spiralis in irradiated mice

Irradiation prevented the accelerated expulsion of Trichinella spiralis from mice immunized by transfer of immune mesenteric lymph node cells (IMLNC) or by prior infection. Nevertheless, worms in irradiated immune mice were smaller and less fecund than those in controls. In adoptively immunized and irradiated mice expulsion could not be achieved by increasing the numbers of IMLNC transferred, although the effect upon worm length was more severe. Thus IMLNC express a direct, anti-worm immunity which is independent of their role in worm expulsion. IMLNC cause expulsion in irradiated mice only when adequate levels of bone marrow-derived cells are available. The results are discussed in terms of a possible antibody-mediated basis for direct anti-worm immunity.     

Response of nonsensitized and sensitized lactating mice to infection with Trichinella spiralis

The effect of lactation on the expulsion of adult Trichinella spiralis were studied in: (1) lactating, (2) induced agalactic post-parturient, (3) previously sensitized, and (4) mice sensitized during lactation. The results indicated that lactation was associated with an altered pattern of worm expulsion; i.e. more adult worms were recovered from nonsensitized and sensitized lactating mice than from control mice. Furthermore, neither mice sensitized before nor during lactation demonstrated an immunity to challenge infection.     

The effect of larval predators Thanasimus dubius (Coleoptera: Cleridae), produced by an improved system of rearing, against the southern pine beetle Dendroctonus frontalis (Coleoptera: Curculionidae)

The southern pine beetle, Dendroctonus frontalis (Coleoptera: Curculionidae) (SPB), is known to be a major bark beetle pest of pines throughout the southeastern United States. A common predator of bark beetles, Thanasimus dubius (Coleoptera: Cleridae), has been suggested to play a prevalent role on SPB dynamics. Evaluations of T. dubius have been limited by rearing methods; an artificial diet for larval T. dubius exists, and preservatives such as sorbic acid could help to maximize diet shelf-life and enhance the efficiency of the rearing system. The effects of sorbic acid at different concentrations (0%, 0.1% and 0.2%) in the larval diet for T. dubius were measured, and the effects of increased feeding time intervals (2-3 vs. 5 days) on predator performance evaluated. In addition, an experimental bioassay was conducted where newly hatched T. dubius larvae were released at four densities (0, 50, 100, and 200 per log) on pine logs infested by SPB. Sorbic acid in the diet reduced female fecundity (by 20-40%), but did not affect adult T. dubius size or longevity. However, using this preservative may not be necessary because it had no effect on the overall efficiency of the rearing system, while refreshing the larval diet every 5 days (compared with 2-3 days) did improve its efficiency, even without sorbic acid. The release of larval T. dubius resulted in a highly significant effect on the SPB ratio of increase (RI). This experiment was facilitated by the improvements in our rearing methods.     

Adoptive transfer of immunity to Trichinella spiralis in mice: generation of effective cells by different life cycle stages

Adoptive transfer of immunity with day 8 mesenteric lymph node cells (MLNC) taken from NIH mice after a chemically abbreviated infection of 3 days duration was as effective as transfer with cells taken from mice which had received an uninterrupted infection. Using a surgical transplantation technique it was demonstrated that adult T. spiralis were not capable of stimulating cells effective upon adoptive transfer. The potent immunogenicity of the early stages of infection was emphasized by data showing that very low numbers of muscle larvae were efficient in stimulating effective mediator cells. Neither the time at which MLNC were taken for transfer after transplantation of adult worms nor the age of adult worms transplanted affected the failure of this life cycle stage to stimulate cells capable of mediating worm expulsion. It is proposed that expulsion of T. spiralis from the gut may be achieved by more than one effector mechanism, and that early and late intestinal stages stimulate these mechanisms differentially.     

Eimeria nieschulzi and Trichinella spiralis: Analysis of concurrent infection in the rat

The effects of concurrent primary infection of the rat with Eimeria nieschulzi and Trichinella spiralis on the number of oocysts of E. nieschulzi shed by the host and on the number, distribution, and fecundity of adult T. spiralis were analyzed. When rats were initially infected with E. nieschulzi followed 9 days later by infection with T. spiralis there occurred a significant decrease in the total numbers of adult worms in the small intestine, a significant shift in the position of these worms along the length of the small gut, a decrease in the fecundity of adult female worms, and a decrease in muscle parasitism when compared with rats infected with T. spiralis alone. When rats were initially infected with T. spiralis, followed 9 days later by infection with E. nieschulzi, there occurred a significant decrease in the numbers of oocysts shed over 24 hr on Days 7, 9, and 11 postinfection below that seen with rats infected only with Eimeria. These changes are discussed in terms of the enteropathophysiologic lesions and enteric inflammation known to occur during infections with these two parasites.     

Trichinella spiralis: Immune response and protective immunity elicited by recombinant paramyosin formulated with different adjuvants

Our previous studies showed that immunization with recombinant paramyosin from Trichinella spiralis (rTs-Pmy) formulated with Freund’s adjuvant significantly reduced larval burden in mice after T. spiralis larval challenge. Since Freund’s adjuvant is toxic and not a suitable adjuvant for clinical vaccine trials, we evaluated the ability of the adjuvants Montanide ISA206 and ISA720 to stimulate immune responses during rTs-Pmy immunization and to enhance protective immunity. The results revealed that immunization of BALB/c mice with rTs-Pmy formulated with either ISA206 or ISA720 triggered Th1 and Th2 immune responses similar to those produced by the conventional Freund’s adjuvant formulation and also provided a similar level of protection against T. spiralis larval challenge. This indicates that the recombinant Ts-Pmy formulated with Montanide ISA206 or ISA720 may be an effective and safety vaccine strategy for trichinellosis.     

Immunosuppressive activity in serum from mice infected with Nematospiroides dubius following passive serum transfer

Dobson C. and Cayzer C. J. R. 1982. Immunosuppressive activity in serum from mice infected with Nematospiroides dubius following passive serum transfer. International Journal for Parasitology12: 561–566. Anti-N. dubius antibody titres increased with time after primary and secondary infections with 100 larvae in mice and 4 days after anthelmintic termination of a 28 day infection. Mice injected with serum from infected mice harboured fewer, smaller worms with reduced fecundities compared with control mice; the difference was greater with serum from donors given two compared with those given one infection.Mice injected with serum from donors infected for 14 days had fewer N. dubius than recipients of serum from mice infected for 28 days. Serum taken from mice 4 days after termination of a primary infection of 28 days duration was more protective when passively transferred to mice than serum from mice infected for 28 days. Serum from mice infected with 50 N. dubius larvae was more protective than serum, with a higher anti-N. dubius antibody titre, from, mice infected with 400 larvae. These observations are discussed in relation to immunosuppressive activities in the donated serum and associated with N. dubius.     

Interactions between Trichinella spiralis and Hymenolepis nana in the intestine of the mouse

Ferretti G., Gabriele F., Palmas C. and Wakelin D. 1984. Interactions between Trichinella spiralis and Hymenolepis nana in the intestine of the mouse. International Journal for Parasitology14: 29–33. The rejection of the intestinal phase of Trichinella spiralis in outbred CD₁ mice is associated with an inflammatory response. The effects of this inflammation were studied in mice concurrently infected with an unrelated parasite, Hymenolepis nana, which stimulates a slight inflammation but is also immunologically rejected by this strain of mice. Moreover though Cd(In)1 mice seem to be ‘slow responders’, in concurrent infections with T. spiralis and H. nana there was a marked effect upon the cesode survival. At the highest level of T. spiralis infection, H. nana failed to establish at all. On the other hand, if 300 T. spiralis were administered 10 weeks earlier, H. nana become established in all mice and the distribution of parasites suggests that immunodepression is involved. An accelerated loss of the nematode, when H. nana was present, was also demonstrated. There was no evidence of any reciprocal or specific cross-immunity between the two parasites.