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.     

Influence of serum donor and recipient mouse genotype on the passive transfer of protective immunity with serum against Nematospiroides dubius

Dobson C., Brindley P. J. and Sitepu P. 1982. Influence of serum donor and recipient mouse genotype on the passive transfer of protective immunity with serum against Nematospiroides dubius. International Journal for Parasitology12: 567–572. Different strains of serum donor mice showed variations in innate immunity to primary infections with Nematospiroides dubius. Different levels of anti-N, dubius antibodies were detected in sera from these mouse strains; there was no correlation between antibody titre and numbers of worms recovered. Serum from donor wild and six laboratory strains of mice protected female Quackenbush (Q) recipients against N. dubius infections; donor mouse strain influenced the degree of protection conferred and donor serum antibody titre related to the degree of stunting of worm growth in recipient mice. Five laboratory strains of mice developed different levels of protective immunity following multiple experimental infections with N. dubius. Antibody titres in these mice were strongly correlated with the percentage protection observed after 1–4 infections: Q and CBA mice produced more anti-N. dubius antibody and were better protected than DBA/2, BALB/c and C3H mice. However BALB/c, C3H and CBA mice attained similar anti-N. dubius antibody titres after a single infection with N. dubius but serum from BALB/c gave better protection when transferred to female Q recipients than that from the other two strains. This suggested qualitative differences in the protective antibodies in sera between mouse strains. Five mouse strains were passively immunized with a uniform dose of serum from female Q donors: DBA/2 female recipients showed the least, BALB/c and C3H females were intermediate, and Q and CBA female mice attained the greatest level of passive protection against N. dubius. A close positive correlation existed between the degree of actively acquired and the level of passively acquired protection between the five strains of mice.     

Nematospiroides dubius in mice selected for liability to infection: Modification of parasite biology through host selection

Brindley P. J. and Dobson C. 1982. Nematospiroides dubius in mice selected for liability to infection: modification of parasite biology through host selection. International Journal for Parasitology12: 573–578. Mice selected as liable (L) and refractory (R) over ten generations voided significantly more and less Nematospiroides dubius eggs compared with randomly mated (Rd) mice after primary infections with 100 larvae. There was little difference between the number of parasite eggs voided g^?1 faeces (epg) by individual mice on day 14 compared with day 15 after infection.However there was a significant diurnal variation in the egg values for individual mice but the mean differences observed between the R, Rd and L mice were maintained over a 24 h period. There was a strong correlation between both the total number and the number of female worms, surviving 21 days after infection, and the mean epg 14 and 15 days after infection. Female N. dubius produced more eggs in L mice and fewer eggs in R mice compared with worms in Rd mice. Similarly, worms grew longer in L mice and were shorter in R mice compared with parasites in Rd mice.     

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.     

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.     

Effects of sterols,rat hematin and coproporphyrin on the free-living stages of Nematospiroides dubius and Nippostrongylus brasiliensis

Nematospiroides dubius, unlike the closely related nematode Nippostrongylus brasiliensis, lacks a sterol requirement for the completion of its development to the L₃ stage in an aqueous suspension of formalin-killed Escherichia coli. These larvae were justascapable of completing their development to adults in mice as those grown on charcoal-feces cultures. In addition, sterols had a toxic effect on the larvae of N. dubius which was removed by substituting a Krebs-Ringer solution for distilled water.In order to interpret the absence of a sterol requirement for the development of N. dubius larvae, an analysis of the egg lipids for both species was made. N. brasiliensis had about twice the sterol concentration of N. dubius eggs. A comparison of the development for both species showed, however, that N. brasiliensis grows more than twice as much as N. dubius to reach the L₃ larval stage. Therefore, the amount of endogenous sterol is insufficient for N. brasiliensis to develop from the egg to the L₃ stage.N. dubius and N. brasiliensis also differ in their porphyrin requirements. Unlike N. brasiliensis, coproporphyrin did not increase the size of N. dubius larvae so that they were comparable to those grown on charcoal-feces cultures. Coproporphyrin did result in larvae that were more robust in appearance than those grown without a supplement.     

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.     

Influence of serial passage on the infectivity and immunogenicity of Nematospiroides dubius in mice

Dobson C. and Owen M. E. 1977. Influence of serial passage on the infectivity and immunogenicity of Nematospiroides dubius in mice. International Journal for Parasitology7: 463–466. The infectivity of Nematospiroides dubius was increased for Quackenbush (Q) mice by ten serial passages through this host. At the same time C(In3)H mice became more refractory to infection with successive Q generations of the parasite. Both strains of mice rejected the most highly selected parasites more readily than parasites from the earlier generations. These responses were shown to be immunological in nature by infections in hypothymic Balb/c CBA nu/nu and nu/+ mice and to be dose dependent. The selection of N. dubius for increased infectivity in Q mice enhanced its immunogenicity in this and other mouse strains possibly because of increased genetic homogenicity in the selected populations. N. dubius selected for Q mice showed a degree of immunologieal adaptation to Q but not to C₃H mice.     

The developmental antigens of Nematospiroides dubius

The developmental antigen spectrum of Nematospiroides dubius was determined using a combination of metabolic labelling, immunoprecipitation and sodium dodecyl sulphate polyacrylamide gel-electrophoresis (SDS-PAGE) analysis. Antigens produced and assessed in this way were shown to be useful for the discrimination of high (SJL) and low (CBA) responder strains of mice. Interesting differences were also noted between larvae (immunogenic?) and adult (immunomodulatory?) stages, lending support to the hypothesis that adults and larvae may differentially produce immunogenic and immunomodulatory molecules. Experiments were also done to ascertain the optimal conditions for fractionating N. dubius polypeptides, and to produce candidate immunomodulatory molecules in vitro by gene-cloning methodology.     

Trichinella spiralis: Delayed rejection in mice concurrently infected with Nematospiroides dubius

The immune response of mice to the nematode Trichinella spiral's was markedly altered when the infection was superimposed upon an existing infection with Nematospiroides dubius. The expulsion of a primary infection of T. spiralis was delayed in such mice, and the worms persisted for at least 4 weeks longer than they did in control mice. The degree to which expulsion was suppressed was related to the number of N. dubius present. It would appear that both adult and larval stages of N. dubius can exert a suppressive effect, since the expulsion of T. spiralis was affected within days of a super-imposed (i.e., larval) N. dubius infection. When adult N. dubius were removed from mice 4 days before infection with T. spiralis, the mice expelled the latter parasite within the normal time, indicating that recovery from the suppressive effects of concurrent infection occurred rapidly. Concurrent infection with N. dubius appeared to affect both the afferent and efferent arms of the immune response to T. spiralis, since sensitization by, and memory of, prior infection were impaired and the expression of acquired immunity was inferior to that of controls.     

Regulation of toxocariasis in mice selectively reared for high and low immune responses to Nematospiroides dubius

Test mice have been selectively reared for high (H) or low (L) immune responses to Nematospiroides dubius. After secondary infection with N. dubius, the L mice voided ten times as many eggs in their faeces as the H mice, and at necropsy, 71% versus 20% of the inoculum of N. dubius were recovered as adult worms from the L and H mice respectively. Furthermore, N. dubius were more fecund in the L than in H mice. High or low immune responsiveness was not restricted to N. dubius infection in these mice but was also observed during Toxocara canis infection. The migration of T. canis larvae from gut via the liver to skeletal muscle and CNS was inhibited in H versus L mice. Many more larvae were recovered from the livers of H compared with L mice which was indicative of greater immunity in the H mice. The protective immune response in H compared with L mice to both N. dubius and T. canis included pronounced eosinophilia and elevated antiparasite antibody titres.     

Immunologic studies on Heligmosomoides polygyrus infection in the mouse: the dynamics of single and multiple infections and the effect of DDT upon acquired resistance

Neilson J.T. McL., Forrester D.J. and Thompson N.P. 1973. Immunologic studies on Heligmosomoides polygyrus infection in the mouse: The dynamics of single and multiple infections and the effect of DDT upon acquired resistance. International Journal for Parasitology3: 371–378. Swiss Webster mice were given infections of 100,200, 300 and 400 Heligmosomoides polygyrus (= Nematospiroides dubius) larvae respectively at intervals of 4 weeks. Where appropriate, the preceding infection was terminated with anthelmintic 7 days prior to the subsequent infection. Animals were killed at regular inteivals following each infection and the worm burdens compared with those found in control mice given a primary infection of similar size. The expulsion of worms in mice given three previous infections occurred after day 3 and before day 7 postinfection indicating that those larvae moulting from the fourth to fifth stages may be most susceptible to the host's resistance mechanisms. The administration of p,p'-DDT to hyperinfected mice did not interfere with the immunologic expulsion of worms.     

Infection of Red Clover Seedlings by Heterodera trifolii Goffart and Pratylenchus penetrans (Cobb)

Penetration of 3-day-old ''Kenland'' red clover seedlings by Heterodera trifolii Goffart and Pratylenchus penetrans (Cobb) was investigated in 50-mm petri dishes on 1% agat or discs of Miracloth® (Chicopee Mills, Inc., New York, N.Y. 10018). Penetration by both nematodes increased arithmetically with increased numbers in the inoculum. H. trifolii larvae slowly penetrated all root tissue but in relatively low numbers, 25-30% of inocula. Swelling of larvae and formation of syncytia within roots was detectable 96 hr after inoculation. Initially, adults of P. penetrans preferentially penetrated the region 3-10 mm behind the root tip, but subsequently they invaded all along roots. P. penetrans penetration efficiency was high, 75-90% of inocula, and penetration was relatively rapid. When introduced simultaneously neither nematode affected the invasiveness of the other. Prior infection by H. trifolii did not affect the invasiveness of P. penetrans.     

Effect of Nippostrongylus brasiliensis infection on anti-hapten IgE antibody response in the mouse: I. Induction of carrier specific helper cells

Inoculation of infective larvae of Nippostrongylus brasiliensis into A/J, BALB/c, and SJL mice primed intraperitoneally (ip) 3 weeks before infection with 1 μg of dinitrophenylated keyhole limpet hemocyanin (DNP-KLH) mixed with 1 mg Al(OH)₃ induced a carrier effect on anti-DNP IgE and IgG₁ antibody responses when the experimental mice were secondarily immunized with an ip injection of 1 μg of DNP-coupled N. brasiliensis extract (DNP-Nb) plus alum 2 weeks after infection. The magnitude of the hapten specific antibody response did not correlate rigidly with the number of larvae in the inoculum. Thus, a dose of 100 larvae was as effective in inducing the carrier effect as a dose of 800 larvae. Kinetic studies in A/J and BALB/c mice revealed that the anti-DNP IgE antibody response reached a maximum titer 7 days after the secondary immunization. These studies also showed that the enhanced IgE antibody response persisted for more than 40 days, while the response in all control groups terminated prior to that time. Using the adoptive transfer system, it was demonstrated that lymphoid cells obtained from the spleens or the mesenteric lymph nodes of infected mice cooperated with DNP-KLH primed cells to produce hapten specific IgE and IgG, antibodies when the challenge was made with DNP-Nb but not when it was made with 1 μg DNP-ovalbumin, clearly indicating carrier specificity. The helper activity of the cells obtained from infected mice was completely abolished or greatly reduced by the in vitro treatment with anti-θ serum and complement. The helper cells with maximum activity were present as early as 14 days after inoculation. The level of helper activity gradually decreased after 14 days. The results indicate that N. brasiliensis infection is effective in inducing carrier specific helper cells of thymic origin (T cells) in anti-DNP antibody responses. These results confirm those obtained by other investigators and add the new observation that N. brasiliensis infection elicits special helper T cells which induce an enhancement as well as a prolongation of anti-DNP IgE antibody response.     

Circulating immunoglobulins and complement in mice with Hymenolepis nana infection

Changes in the circulating immunoglobulins and complement in ddY mice were assayed at various times after immunizing and challenge infections with Hymenolepis nana eggs. The levels of IgG1 and IgG2a consistently increased during 3–4 weeks after immunizing infection. The increase of these immunoglobulins after challenge infection was quicker and more intense than that following immunization. It was not possible to correlate increased levels of IgG1 and IgG2a with the onset of destruction of challenge larvae in immunized mice. IgM concentrations increased slightly during 4 days after immunization but challenge infection did not further increase IgM levels. IgA and IgG2b levels showed no significant change during the course of the infection. Serum C3 levels showed no discernible change after either immunizing or challenge infections. An attempt to specifically suppress the acquisition of resistance by administration of the complement-depleting agent, cobra venom factor (CoF), before immunization failed and depletion of complement activity with CoF that was administered just before challenge infection also failed to affect resistance. These results suggest that complement has no critical role in either induction of the response nor in the anamnestic response to H. nana infection in mice.     

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.     

Co-Occlusion and Persistence of a Baculovirus Mutant Lacking the Polyhedrin Gene

A co-occlusion process was evaluated as a commercially and ecologically acceptable strategy for the development of genetically improved baculovirus insecticides. Coinfection of Spodoptera frugiperda (IPLB-SF-21) tissue culture cells with Autographa californica nuclear polyhedrosis virus (AcMNPV) and an AcMNPV mutant (Ac-E10) lacking the polyhedrin gene resulted in occlusion of both virus types within polyhedra. The amount of occluded Ac-E10 virions in progeny polyhedra populations during serial passage in Trichoplusia ni larvae was evaluated. Maintenance of the mutant in progeny polyhedra required polyhedra inocula containing equal numbers of the two virus types at a high dose. A significant reduction in occluded mutant nucleocapsids occurs with inoculum levels below a 100% lethal dose. At inoculum levels below a 30% lethal dose, the majority of fourth-instar larvae were infected with only one type of virus. The commercial application and ecological advantages of the co-occlusion process are discussed.     

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.     

Effects of Nematicides on Nematode Densities in Turf in Connecticut

The plant-parasitic nematodes Criconemoides lobatum, Hoplolaimus tylenchiformis, and Tylenchorhynchus dubius were present in the top 7.5 cm of sod consisting of numerous stolons and fibrous roots. Phenamiphos and 1,2-dibromo-3-chloropropane (DBCP) controlled all three species, whereas ethoprop and oxamyl controlled H. tylenchiformis and T. dubius but not C. lobatum. Benomyl and carbofuran controlled H. tylenchiformis but had poor control of C. lobatum and T. dubius. The effectiveness of carbofuran varied with the type of formulation, being most effective as a quick-release formulation. C. lobatum was the most difficult to control with chemicals. No chemical treatment improved the growth of ''Astoria colonial'' bentgrass (A. tenuis Sibth.) or Kentucky bluegrass (Poa pratensis L.) under the moist condtions prevalent in these tests.     

Passive transfer of immunity with serum in mice infected with Nematospiroides dubius: in vitro effect of immune serum on larval infectivity

Dobson C. and Cayzer C. J. R. 1982. Passive transfer of immunity with serum in mice infected with Nematospiroides dubius: in vitro effect of immune serum on larval infectivity. International Journal for Parasitology12: 413–421. Incubation of Nematospiroides dubius larvae in serum in vitro induced 15% exsheathment after 3h. Larvae incubated in immune mouse serum at 37°C for 3h lost 20% of their infectivity for mice. Immune serum from donors given 1–7 concurrent or anthelmintic abbreviated infections all depressed larval infectivity to the same extent. Larvae incubated in immune sera were protected from the effects of passively transferred immune serum in mice following infection. The effects of incubation of larvae in immune serum were prolonged into the adult stages of the parasite and were seen as stunting of worms and a reduction in the male-female sex ratio of the parasites.