Nippostrongylus brasiliensis: Peripheral blood leucocyte response of rats,with special reference to basophils

Changes in peripheral blood leucocytes were followed in male August rats given one or two infections with the parasitic nematode, Nippostrongylus brasiliensis. During the initial infection, there was a biphasic increase in total numbers of leucocytes, lymphocytes, neutrophils, large mononuclear cells, and eosinophils. All except eosinophils fell rapidly to normal levels as the parasites were expelled, but eosinophils were elevated much longer. All these cell types increased in number to a single peak 5 days after reinfection. Basophils were detected at very low levels in uninfected rats (0.06% or $\text{1}\text{1600}$ leucocytes) and increased in number to a peak 13 days after initial infection, at which time they represented about 4.5% of total leucocytes, an 80-fold increase compared with the number in normal rats. In reinfected rats, the basophilia occurred more rapidly than in a primary infection, suggesting that the appearance of these cells in the circulation is probably an immunologically mediated event.     

Nippostrongylus brasiliensis: Effect of cyclophosphamide treatment on worm expulsion in rats

The precise immunological mechanisms associated with expulsion of the gastrointestinal nematode Nippostrongylus brasiliensis remain controversial. In order to investigate the effects of drug-induced immunosuppression on parasite burdens and expulsion, various regimens of cyclophosphamide were administered to parasitized Wistar rats. It was observed that both the number of worms established from an infective dose of 3000 larvae and the time of expulsion were markedly increased with higher doses of cyclophosphamide. Thus, at the highest sublethal level of treatment (100 mg/kg), 82% of the infective dose was recovered at Day 9 postinfection compared with 51% in nontreated controls. Furthermore, in such treated rats expulsion was delayed in 6 days beyond that of nontreated animals. As cyclophosphamide, at the levels used in the present study, is known to primarily effect B-cell function, the results support the view that antibody-mediated responses play an essential role in worm expulsion.     

Nippostrongylus brasiliensis: Mast cell kinetics at small intestinal sites in infected rats

Mast cell kinetics during infection with the nematode Nippostrongylus brasiliensis were studied at various sites in the small bowel of rats and in heterotopically transplanted isografts of foetal small intestine placed under the kidney capsule. Infection produced an increase in the number of mast cells not only in the proximal jejunum, where most of the worms are located, but also in the distal ileum and in isografts of small intestine. However, globule leucocyte infiltration of the gut epithelium was confined to the proximal small intestine and did not occur in the distal ileum or isografts. These results show that the mast cell increase in the small bowel of N. brasiliensis-infected rats is a property of the whole organ, and is not restricted to sites of worm infection; but that in contrast, globule leucocyte infiltration of the epithelium is dependent upon the presence of worms within the bowel lumen.     

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.     

Nippostrongylus brasiliensis: intestinal goblet-cell response in adoptively immunized rats.

Goblet-cell differentiation was studied in the intestinal epithelium of rats infected with the nematode Nippostrongylus brasiliensis. An increase in the proportion of goblet cells occurred at the time of worm expulsion in rats infected with 1000 or 4000 third stage larvae. Adoptive immunization of infected rats with immune-thoracic duct lymphocytes (TDL) induced extensive goblet-cell differentiation whereas the transfer of immune-TDL into normal rats had no effect. The extent of goblet-cell differentiation in adoptively immunized infected rats was proportional to the number of cells transferred. A goblet-cell response also occurred in adoptively immunized rats harboring implanted “normal” and “damaged” worms but recipients of normal worms which were not given cells were unable either to expel their worm burden or to induce a goblet-cell response. Experiments in which the parasites were expelled with an anthelmintic drug suggested that the goblet-cell increase was not simply a repair process associated with the expulsion of the parasites. In all situations where immune expulsion of the parasites occurred, there was a concomitant rise in the proportion of goblet cells. These experiments suggest that thoracic duct lymphocytes either directly or indirectly regulate the differentiation of intestinal goblet cells.     

Trichinella spiralis: Immunization of rats with an antigen fraction enriched for allergenicity

Trichinella spiralis whole muscle larval extract was fractionated by gel filtration and anion-exchange chromatography, and the protein fractions were assayed for allergenicity by a footpad-swelling test in mice; IgE antibody levels in rats immunized with the fractions were determined by passive cutaneous anaphylaxis test in rats. By these methods, an allergenic fraction from T. spiralis was isolated. The fraction, F1-b, was shown to be monodisperse by analysis with SDS-PAGE, IEP, and isoelectric focusing, indicating that it is a single protein moiety with a molecular weight of approximately 45,000 and a pI of approximately 5.1. The Schiff-periodate test showed Fl-b to be a glycoprotein. Rats immunized with Fl-b had significantly fewer intestinal worms than did nonimmunized controls at 24 hr and 7 days after oral challenge with T. spiralis larvae.     

Angiostrongylus cantonensis: Biogenic amines in the lungs of infected rats

Levels of histamine, serotonin, norepinephrine, and dopamine were estimated sequentially in rats parasitized by the lungworm, Angiostrongylus cantonensis, between 30 and 75 days postinfection. The highest level of histamine in the infected lungs was 52.19 μg/g wet wt tissue, 13 times higher than the level found in control rats. The level of serotonin rose from the normal level of 6.41 to 10.27 μg/g wet wt tissue after the worms had lodged in the pulmonary artery for 15 days. There were no changes in norephinephrine or dopamine. Studies of host cell response to infection revealed that the increased histamine and serotonin levels corresponded to a rise in the lung population of mast cells, suggesting that these cells produced the amines.     

Trichinella spiralis: Genetics of worm expulsion in inbred and F1 mice infected with different worm doses

The nematode Trichinella spiralis is rejected from the intestine at a time that is characteristic for each inbred strain of mouse. Previous work (R. G. Bell et al. 1982a) had empirically identified strong, intermediate, and weak phenotypes (NFR, $\text{C}\text{H}\text{He}$, and $\text{C57}\text{10}$ mice, respectively) in mice infected with 400 muscle larvae. It is shown that this classification applies to another eight inbred strains: SWR, $\text{DBA}\text{2}$, $\text{DBA}\text{1}$, LP, $\text{Bub}\text{Bn}$—all intermediate, and $\text{NZB}\text{BIN}$, C57L, A, and Mus molossinus—all weak. This phenotypic classification consistently applies with infections of 400–800 muscle larvae. Below doses of 300 muscle larvae, the strain designation of phenotype does not consistently apply. By this it is meant that the relative rejection rate changes for certain strains so that eventually some strains that were strong (NFR) or intermediate (AKR) responders to 400 muscle larvae become weak responders to 50 muscle larvae. Other strains increase their relative rejection time (B10 · BR, B10 · Q) while many do not change (NFS, $\text{C}\text{3}\text{Heb}\text{Fe}$, $\text{DBA}\text{2}$, $\text{DBA}\text{1}$). The phenomenon is most apparent in inbred parental strains rather than in F₁ crosses, and it represents a phenotypic variation in rejection time that is dependent on dose. It is also demonstrated that time of rejection is directly proportional to dose in all inbred and F₁ mouse strains that we have examined. Analysis of F₁ crosses shows that most have the rejection time of the strongest responding parental line, suggesting simple genetic control of strong, intermediate, and weak responses. Two F₁ crosses invalidated this theory. The $\text{DBA}\text{1}\text{×}\text{C3}\text{H}\text{He}$ (intermediate × intermediate) showed a strong response. The additive effects of parental rejection phenotype indicated that these lines could not be genetically identical for intermediate responsiveness. Similarly, the NFR (strong) × B10 · BR (weak) F₁ showed intermediate rejection, indicating partial dominance of $\text{C}\text{57}\text{B}\text{1}\text{10}$ genes over the strong responder NFR strain. Neither the primary expulsion time phenotype, phenotypic variation to low doses, or the rejection characteristics of F₁ crosses could be ascribed to genes linked to the major histocompatibility complex.     

Nippostrongylus brasiliensis and Nematodirus battus: Changes in numbers and weight during the course of infection

Nematodirus battus has been shown to be subject to a “self-cure” mechanism when lambs 6 weeks of age are infected with 60,000 larvae. It is proposed that this self-cure phenomenon is an immune response similar to that which occurs in rats infected with Nippostrongylus brasiliensis. Changes in the weight of adult Nematodirus sp. and Nippostrongylus sp. occur over the period of an infection in their hosts. Females of both species from high-dose infections increased in weight up to that time postinfection where most adult worms were present, then decreased in weight with the onset of rejection from the host. Male Nematodirus sp. showed a similar pattern of weight change to that of females but male Nippostrongylus sp. maintained a steady weight throughout the infection. The consequences of these changes in weight are discussed with relevance to expression of enzyme activities of the nematodes on a weight of individual nematode basis.     

Brugia pahangi: Antibodies and microfilaremias in Lewis rats

Male and female Lewis rats were inoculated subcutaneously in the left groin with 75 infective larvae of Brugia pahangi and microfilaremias were followed for as long as 420 days postinoculation. Patent infections developed in 64% of the female rats and 95% of the male rats. Mean prepatent periods were similar (65.9 and 63.9 days, respectively), but mean microfilaremias in males rose much higher, to a mean of 218 mf/0.25 ml blood at 270 days postinoculation. IgG titers, as measured by enzyme-linked immunosorbent assay (ELISA), to adult worm somatic antigen were higher than those to microfilariae in almost all rats. For both sexes, the most consistently microfilaremic rats had highest titers to these antigens. Granulomas with degenerating microfilaria were present in the spleen of male rats with high microfilaremias (>100–300 mf/0.25 ml blood). Ouchterlony precipitin reactions suggested that most rats with spleen granulomas responded to microfilarial antigen components to which most rats without granulomas did not. Neither spleen granulomas nor antibody responses measured in this study appeared to have protective (microfilaremia-lowering) value. As measured by microfilaremias, the male Lewis rat is not as susceptible as some conventional hosts of B. pahangi, but it does consistently become infected and remains microfilaremic for more than a year. Preferential male susceptibility indicates that this model may be useful for studying this aspect of human lymphatic filariasis.     

Nippostrongylus brasiliensis: local humoral responses in the lungs and intestines of rats following vaccination with irradiated larvae

Groups of rats were infected with 2000 normal larvae of Nippostrongylus brasiliensis or larvae irradiated with 10 to 120 kR. On Day 10 after infection half the animals from each group were autopsied. The remainder were challenged with 5000 unirradiated larvae on Day 15 and killed ten days later. During the experiment enteric antibody levels were estimated by coproantibody measurement. At autopsy the worm burdens were determined and worm-specific antibodies evaluated in lung extracts and serum. It was found that the levels of coproantibody detected with adult worm metabolites were positively correlated with the number of adult nematodes recovered from the intestine after primary infection. The challenge induced a similar increase of these antibodies in all immunised rats which reflected a high immunity to reinfection of vaccinated animals. Preliminary immunochemical studies suggested that the coproantibodies had SIgA properties. In lung extracts of rats immunised with larvae irradiated at 40, 80, or 120 kR and in all animals after challenge, antibodies reacting with infective larval antigens were found. Their titres were negatively correlated with serum antibody levels. The significance of bronchial and enteric antibodies in conferring protection against challenge remains to be elucidated.     

Peripheral blood white cell responses during Angiostrongylus cantonensis infection in rats

Yono W. K. and Dobson C. 1984. Peripheral blood white cell responses during Angiostrongylus cantonensis infections in rats. Interntional Journal for Parasitology14: 207–211. Changes in white blood cell (WBC) populations and their proliferative responses to phytohaemagglutinin (PHA) and parasite antigens in vitro were studied in rats given one to three concurrent infections with Angiostrongylus cantonensis. WBC counts were elevated following infection; these changes were augmented following each successive reinfection. The WBC response could be partitioned into variations in the numbers of four major cell types. There was a loss of lymphocytes from the circulation after infection or reinfection followed by an increase in circulating lymphocytes when the parasite migrated to the lungs and matured. An eosinophilia was observed in all rats immediately after infection which was enhanced successively after each reinfection. The monocyte populations increased in a similar, but less obvious manner, to the eosinophil leucocytes. Neutrophil leucocytes increased after infection, but the numbers declined after reinfection. All rats given one to three infections showed a neutrophilia late in the experiment. A reversal in the neutrophil leucocyte-lymphocyte ratio was observed after each infection. A peak response in the proliferation of peripheral blood lymphocytes in vitro to PHA preceded and exceeded that stimulated by A. cantonensis antigen. These responses were interpreted as the dissemination of uncommitted thymus-dependent lymphocytes involved in the induction of antigen sensitized memory cells released following the protective immune reaction. The degree of lymphocyte responsiveness to mitogens correlated with the numbers of these cells circulating at each time interval. The relationships between in vitro lymphocyte responses and protective immunity in the rat against A. cantonensis are discussed.     

Strongyloides ratti: Dissociation of the rat's protective immunity into systemic and intestinal components

Analysis of the early stages of a challenge infection with Strongyloides ratti has shown that protection is expressed against the developing third-stage larval worms (L₃) and prevents the maturation to adulthood of most larvae. Challenge after an immunizing infection that was restricted to the parenteral L₃ migratory phase showed that some 10–40% of overall protection could be ascribed to systemic antilarval immunity. Some larvae were trapped in the skin at the site of injection whereas others failed to migrate to the head and lung of immune rats. Larvae arriving in the intestine at Days 3, 4, and 5 did not persist beyond Day 7 and 8. Studies using [⁷⁵Se]methionine-labeled L₃ showed a significant increase in fecal label in rats immunized by a complete infection. This loss did not occur to the same extent in rats immunized only with parenteral larvae. Significant rejection of worms transplanted to the intestine also indicated intestinal protection. The possible existence of large numbers of worms in a state of “arrested development” was excluded by their failure to appear after cortisone treatment and the absence of worm accumulation in radiolabeling studies. It is concluded that at least two responses operate against larval S. ratti, one is systemic and the other operates in the intestine against larvae in a manner that resembles the “rapid expulsion” rejection of Trichinella spiralis in immune rats.     

Strongyloides ratti: Mast cell and goblet cell responses in the small intestine of infected rats

Kinetics of intestinal mast cells and goblet cells were examined in relation to worm localization at various sites in the small intestine of rats infected with 3000 filariform (stage 3) larvae of Strongyloides ratti. The most marked intestinal mastocytosis was observed on Day 20 at the anterior site of the small intestine where the majority of the worms had concentrated. The number of mast cells in the posterior small intestine increased in parallel with the posterior shift of parasites at the later stage of the infection. In contrast to the intestinal mast cell response, the number of goblet cells was not significantly affected by the infection. These results strongly suggest that intestinal mastocytosis is closely related to the presence of the worms and that mast cells may play an important role for the expulsion of S. ratti.     

Eimeria tenella,Eimeria necatrix, and Eimeria adenoeides: Peripheral blood leukocyte response of chickens and turkeys to strains adapted to the turkey embryo

The peripheral blood leukocyte responses of chickens and turkeys inoculated with one of three strains of a chicken Eimeria species adapted to the turkey embryo with their respective parent lines, or with E. adenoeides of the turkey were studied. The adapted lines tended to cause hematological changes in chickens and turkeys similar to those caused by E. adenoeides. These parasites caused the most significant increases in large mononuclear white blood cells = (monocytes) in both chickens and turkeys. These results provide further evidence for a monocyte/macrophage effector mechanism in the rejection of heterologous species of Eimeria from a nonspecific host. The results also agree with previous studies that show that increases in mononuclear white blood cells during parent E. tenella and E. necatrix infections in chickens occur during the periods of greatest tissue damage (3–4 days after inoculation). The generally unaffected lymphocyte numbers and increases in mononuclear white blood cells during infections with the adapted lines probably explain the reduced pathogenicity and the lack of immunogenicity seen previously in chickens inoculated with these three lines. Possibly, monocytes/macrophages play a role in the host specificity of the parasites.     

Dirofilaria immitis: Parasite-specific humoral and cellular immune responses in experimentally infected dogs

Humoral and cellular immune responses to adult antigens of Dirofilaria immitis were evaluated in experimentally infected dogs during the chronic phase of infection. All infected dogs had significantly elevated IgG (enzyme-linked immunosorbent assay) and IgE (passive cutaneous anaphylaxis) titers against D. immitis adult antigens. However, there was little difference between infected dogs and uninfected controls in cellular-immune responses to D. immitis adult antigen or phytohemagglutinin as assessed by the lymphocyte transformation assay. Although neither cellular nor humoral responses correlated with worm burdens, cellular responses among infected dogs correlated inversely with IgG titers to D. immitis adult antigen. These results are consistent with observations in other nematode and trematode systems which suggest that in chronic tissue helminth infections there is suppression of cellular immune responses to parasite antigens while humoral responses to the same antigens remain relatively preserved.     

Trichinella spiralis: Rapid,immunologically influenced reduction of intestinal,sodium-coupled sugar transport in the rat

Epithelium of isolated small intestinal segments were studied in Ussing-type chambers to detect physiological changes associated with rapid, immune rejection of Trichinella spiralis infective larvae. Electrophysiological parameters associated with Na⁺-coupled hexose transport were measured. Changes in transepithelial electrical potential difference (PD), resistance, and short circuit current (I_sc) due to the addition of actively absorbed β-methyl-d-glucoside (BMG) to the mucosal solution were determined. Measurements were made prior to and 30 min after primary and secondary infections. Animals were infected by intraduodenal inoculation. As the infective larval dose in primarily infected (nonimmunized) rats increased from 50 to 2000 larvae the magnitude of the rise in I_sc elicited by BMG decreased in a dose-dependent fashion, with 50 larvae per rat having no effect. In previously infected (immunized) rats challenged with a secondary inoculum, all doses, ranging from 50 to 2000 larvae per rat, decreased the BMG-stimulated change in I_sc by approximately 50%. The effect of 50 worms per rat in immunized hosts was equivalent to that produced by ~1600 worms in nonimmunized animals. Measurements of ¹⁴C-BMG mucosa-to-serosa flux confirmed that Na⁺-BMG cotransport was responsible for observed changes in I_sc. Results support the conclusion that changes in intestinal epithelial function are associated with larval challenge of immune rats.     

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.     

Nippostrongylus brasiliensis: Increase of sialomucins reacting with anti-mucin monoclonal antibody HCM31 in rat small intestinal mucosa with primary infection and reinfection

Infections with the parasitic helminth, Nippostrongylus brasiliensis, cause changes in rat small intestinal goblet cell mucin, particularly in the peripheral sugar residues of oligosaccharide. These changes may correlate with expulsion. In this study, we examined changes in mucin oligosaccharides caused by primary infection and reinfection with N. brasiliensis, using two monoclonal antibodies, HCM31 and PGM34, that react with sialomucin and sulfomucin, respectively. Enzyme-linked immunosorbent assay of jejunal mucins showed that the relative reactivity of mucins with HCM31, but not PGM34, increased up to 16 days after primary infection and 6 days after reinfection, the times when the worms were expelled from the rats. Immunohistochemical studies confirmed that goblet cells stained with HCM31 greatly increased at the time of worm expulsion. These results indicate that the marked increase observed in HCM31-reactive sialomucins may be related to expulsion of the worms.     

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.