The immunomodulatory effects of the Enalapril in combination with Benznidazole during acute and chronic phases of the experimental infection with Trypanosoma cruzi.

Trypanosoma cruzi infection triggers a chronic inflammatory process responsible for the alterations in the extracellular matrix and functionality of the heart. The angiotensin converting enzyme (ACE) inhibitors affects T. cruzi in vitro surveillance and modulates in vivo some inflammatory mediators. In this study, we investigated the treatment with an ACE inhibitor (Enalapril) and the Benznidazole (Bz) in a single and combination therapies (CT) in C57BL/6 mice infected with VL-10 strain of the T. cruzi. Animals were treated during 20days with different doses of Bz (100, 80, 60mg/kg), Enalapril (25, 20, 15mg/kg) and their CT (100+25; 80+20; 60+15mg/kg) and euthanized at 30° (acute) and at 120° (chronic) days post infection. The plasma and heart were processed for immunopathological investigations. Our data shown that Bz and Enalapril controlled, in part, the parasite replication and reduced plasma levels of TNF, CCL2 and CCL5 in the acute and in chronic phase of infection. However, the CT doses reduced in around 20% the inflammatory parameters obtained with the Bz therapy. The CT doses of 100+25 and 80+20mg/kg increased the IL-10 levels and reduced the cardiac inflammation while Bz inhibited the collagen neogenesis in the infection. In conclusion, we assume that the CT administrated in the initial stage of infection, presents a minor immunomodulatory effect when the VL-10 strain of T. cruzi is used. In contrast, Bz and Enalapril in monotherapies persist suggesting a potential protection against cardiac damages during experimental T. cruzi infection.

Comparative Susceptibility of Different Mouse Strains to Liver-Stage Infection With Plasmodium berghei Sporozoites Assessed Using In Vivo Imaging.

BACKGROUND: The liver stages of Plasmodium parasites are important targets for the discovery and development of prophylactic drugs. METHODS: A real-time in vivo imaging system was used to determine the level of luminescence measured from firefly luciferase expression by sporozoites developing in hepatocytes in different strains of mice. RESULTS: The luminescence values (photon counts/sec) measured from the anatomical liver location in the untreated mice infected with 10,000 Plasmodium berghei sporozoites were 8.15 × 105 for C57BL/6 Albino, 2.12 × 105 for C3H/HeNCrL, 0.91 × 105 for C57BL/6 WT, 0.28 × 105 for BALB/c, and 0.16 × 105 for ICR/CD-1 mice. This data suggests that the C57BL/6 Albino strain is most susceptible to luminescent photon, mainly because the less light scattering and absorption from deeper tissues and the skin in the strain of mouse. The photon count observed in black C57BL/6 wild type mice was shown to be 88.83% lower compared to C57BL/6 Albino mice. Although the highest growth rate of sporozoites in hepatocytes was found for C57BL/6 wild type mice in this study, the black skin of this mouse significantly reduced parasite-associated bioluminescence. CONCLUSIONS: The minimal light scattering and absorption and also enhanced susceptibility to liver infection of C57BL/6 Albino mice makes this strain preferable sensitivity for discovery and development of prophylactic antimalarial drugs.

Occurrence of Fasciola hepatica (Linnaeus, 1758) in capybara (Hydrochoerus hydrochaeris) (Linnaeus, 1766) in Minas Gerais, Brazil / Ocorrência de Fasciola hepatica (Linnaeus, 1758) em capivara (Hydrochoerus hydrochaeris) (Linnaeus, 1766) em Minas Gerais, Brasil

Abstract Fasciola hepatica is a parasite that affects the hepatic ducts of several species of domestic and wild vertebrates, causing huge economic losses to livestock rearing worldwide. Reports on occurrences of F. hepatica in capybaras are an important epidemiological aspect of this disease, since these rodents can be a source of contamination for other animals and humans. In the present study, conducted in a rural area of the municipality of Confins, Minas Gerais, fresh feces from capybaras were collected from the ground near a lagoon at the edge of the Ribeirão da Mata river. These were examined using the technique of four metal sieves. F. hepatica eggs were recovered. This trematode species was confirmed by observing morphological characteristics and measuring the eggs recovered from the capybara feces, and through experimental infection of Lymnaea columella (Say, 1817) by miracidia from these eggs and subsequent infection of C57/BL06 mice with metacercariae originating from these infected mollusks. The data suggest the occurrence of natural cycle of F. hepatica in this region and provide a warning that expansion of the geographical distribution of this parasite by means of this rodent is possible. It is therefore important to adopting measures for epidemiological control of this helminthiasis.

Resumo Fasciola hepatica é um parasito que acomete os ductos hepáticos de diversas espécies de vertebrados domésticos e silvestres, causando grandes perdas econômicas na pecuária global. Relatos sobre a ocorrência de F. hepatica em capivaras constituem um importante aspecto epidemiológico dessa parasitose, visto que esses roedores podem ser fonte de contaminação para outros animais e humanos. No presente estudo realizado em área rural do município de Confins, Minas Gerais, foram coletadas no solo, próximo à lagoa marginal do rio Ribeirão da Mata, fezes frescas de capivaras. Essas foram examinadas pela técnica de quatro tamises metálicos. Foram recuperados ovos de F. hepatica. A confirmação da espécie desse trematódeo foi realizada por observação de características morfológica e mensuração dos ovos recuperados das capivaras, infecção experimental de moluscos Lymnaea columella (Say, 1817) por miracídios oriundos desses ovos e pela infecção de camundongos C57/BL06 com metacercárias oriundas desses moluscos infectados. Os dados obtidos sugerem a ocorrência do ciclo natural de F. hepatica na região, alertando que a expansão da distribuição geográfica deste parasito por esse roedor é possível. Portanto, é importante a adoção de medidas para o controle epidemiológico desta helmintíase.

Occurrence of Fasciola hepatica (Linnaeus, 1758) in capybara (Hydrochoerus hydrochaeris) (Linnaeus, 1766) in Minas Gerais, Brazil.

Fasciola hepatica is a parasite that affects the hepatic ducts of several species of domestic and wild vertebrates, causing huge economic losses to livestock rearing worldwide. Reports on occurrences of F. hepatica in capybaras are an important epidemiological aspect of this disease, since these rodents can be a source of contamination for other animals and humans. In the present study, conducted in a rural area of the municipality of Confins, Minas Gerais, fresh feces from capybaras were collected from the ground near a lagoon at the edge of the Ribeirão da Mata river. These were examined using the technique of four metal sieves. F. hepatica eggs were recovered. This trematode species was confirmed by observing morphological characteristics and measuring the eggs recovered from the capybara feces, and through experimental infection of Lymnaea columella (Say, 1817) by miracidia from these eggs and subsequent infection of C57/BL06 mice with metacercariae originating from these infected mollusks. The data suggest the occurrence of natural cycle of F. hepatica in this region and provide a warning that expansion of the geographical distribution of this parasite by means of this rodent is possible. It is therefore important to adopting measures for epidemiological control of this helminthiasis.

Validation of IMP dehydrogenase inhibitors in a mouse model of cryptosporidiosis.

Cryptosporidium parasites are a major cause of diarrhea and malnutrition in the developing world, a frequent cause of waterborne disease in the developed world, and a potential bioterrorism agent. Currently, available treatment is limited, and Cryptosporidium drug discovery remains largely unsuccessful. As a result, the pharmacokinetic properties required for in vivo efficacy have not been established. We have been engaged in a Cryptosporidium drug discovery program targeting IMP dehydrogenase (CpIMPDH). Here, we report the activity of eight potent and selective inhibitors of CpIMPDH in the interleukin-12 (IL-12) knockout mouse model, which mimics acute human cryptosporidiosis. Two compounds displayed significant antiparasitic activity, validating CpIMPDH as a drug target. The best compound, P131 (250 mg/kg of body weight/day), performed equivalently to paromomycin (2,000 mg/kg/day) when administered in a single dose and better than paromomycin when administered in three daily doses. One compound, A110, appeared to promote Cryptosporidium infection. The pharmacokinetic, uptake, and permeability properties of the eight compounds were measured. P131 had the lowest systemic distribution but accumulated to high concentrations within intestinal cells. A110 had the highest systemic distribution. These observations suggest that systemic distribution is not required, and may be a liability, for in vivo antiparasitic activity. Intriguingly, A110 caused specific alterations in fecal microbiota that were not observed with P131 or vehicle alone. Such changes may explain how A110 promotes parasitemia. Collectively, these observations suggest a blueprint for the development of anticryptosporidial therapy.

Infection of C57BL/6 mice by Trypanosoma musculi modulates host immune responses during Brucella abortus cocolonization.

Brucellosis, which results in fetal abortions in domestic and wildlife animal populations, is of major concern in the US and throughout much of the world. The disease, caused by Brucella abortus, poses an economic threat to agriculture-based communities. A moderately efficacious live attenuated vaccine (B. abortus strain RB51) exists. However, even with vaccine use, outbreaks occur. Evidence suggests that elk (Cervus canadensis), a wild host reservoir, are the source of recent outbreaks in domestic cattle herds in Wyoming, USA. Brucella abortus establishes a chronic, persistent infection in elk. The molecular mechanisms allowing the establishment of this persistent infective state are currently unknown. A potential mechanism could be that concurrent pathogen burdens contribute to persistence. In Wyoming, elk are chronically infected with Trypanosoma cervi, which may modulate host responses in a similar manner to that documented for other trypanosomes. To identify any synergistic relationship between the two pathogens, we simulated coinfection in the well-established murine brucellosis model using Trypanosoma musculi and B. abortus S19. Groups of C57BL/6 mice (Mus musculus) were infected with either B. abortus strain 19 (S19) or T. musculi or both. Sera were collected weekly; spleens from euthanized mice were tested to determine bacterial load near the end of normal brucellosis infection. Although changes in bacterial load were observed during the later stages of brucellosis in those mice coinfected with T. musculi, the most significant finding was the suppression of gamma interferon early during the infection along with an increase in interleukin-10 secretion compared with mice infected with either pathogen alone. These results suggest that immune modulatory events occur in the mouse during coinfection and that further experiments are warranted to determine if T. cervi impacts Brucella infection in elk.

Warmer temperatures reduce the vectorial capacity of malaria mosquitoes.

The development rate of parasites and pathogens within vectors typically increases with temperature. Accordingly, transmission intensity is generally assumed to be higher under warmer conditions. However, development is only one component of parasite/pathogen life history and there has been little research exploring the temperature sensitivity of other traits that contribute to transmission intensity. Here, using a rodent malaria, we show that vector competence (the maximum proportion of infectious mosquitoes, which implicitly includes parasite survival across the incubation period) tails off at higher temperatures, even though parasite development rate increases. We also show that the standard measure of the parasite incubation period (i.e. time until the first mosquitoes within a cohort become infectious following an infected blood-meal) is incomplete because parasite development follows a cumulative distribution, which itself varies with temperature. Including these effects in a simple model dramatically alters estimates of transmission intensity and reduces the optimum temperature for transmission. These results highlight the need to understand the interactive effects of environmental temperature on multiple host-disease life-history traits and challenge the assumptions of many current disease models that ignore this complexity.

Comparison of a fur mite PCR assay and the tape test for initial and posttreatment diagnosis during a natural infection.

Fur mites were diagnosed in a colony of mice at our research institution. In the current study, we compared the effectiveness of PCR and tape test in a small population of mice at the onset of diagnosis and throughout treatment. Samples were collected 1 d prior to treatment with permethrin impregnated cotton balls and 6 and 12 wk after treatment. PCR confirmed the presence of Myocoptes musculinus and Radfordia affinis or Myobia musculi, but tape test confirmed only the presence of Myocoptes spp. The results of the PCR and tape test agreed 97.2% of the time during active infection on day 1, but only 59.5% and 48.4% of results coincided at 6 and 12 wk after treatment, respectively. At 6 wk, 11 of the 37 samples were PCR-negative but tape-test-positive, compared with 9 of the 31 samples at 12 wk. Our results show that PCR is a reliable diagnostic method during active fur mite infection but that false-negative results are possible after treatment. Negative PCR results after treatment should be interpreted carefully, and a secondary diagnostic method should be considered.

Anopheles stephensi saliva enhances progression of cerebral malaria in a murine model.

Malaria accounts for the greatest morbidity and mortality of any arthropod-borne disease globally. Recently, it was determined that the protective antisporozoite CD8+ T-cell response originates predominantly from cutaneous lymph nodes draining the site of parasite inoculation by an Anopheles mosquito. The female mosquito inoculates sporozoites along with an assortment of salivary proteins into the skin of its mammalian host. Mosquito saliva has demonstrable antihemostatic as well as various immunomodulatory activities, and studies with mosquito-borne viruses support a role for mosquito saliva in enhancement of transmission and exacerbation of disease. Early differences in immune response can be detected, which discriminate between mice that are resistant and susceptible to neurological pathology. This supports the idea that early divergence in the immune response may influence the likelihood of progression to the more severe forms of malaria. To evaluate the effect of mosquito feeding on the pathogenesis and immune response to malaria, we injected washed Plasmodium berghei sporozoites intradermally in the presence or absence of mosquito feeding. We observed that mice exposed to mosquito feeding in tandem with the inoculation of sporozoites had higher parasitemias and an elevated progression to cerebral malaria. This was associated with, in particular, elevated levels of interleukin-4 and interleukin-10, suppression of overall transcription in response to infection, and decreased extravasation of dendritic cells and monocytes. This study enhances to our understanding of the complexity of the interactions between the malaria parasite, its host, and the mosquito vector.

Interleukin-17-mediated control of parasitemia in experimental Trypanosoma congolense infection in mice.

BALB/c mice are highly susceptible to experimental Trypanosoma congolense infections, whereas C57BL/6 mice are relatively resistant. Infected highly susceptible BALB/c mice die of systemic inflammatory response syndrome. Because interleukin-17 (IL-17) and Th17 cells regulate inflammatory responses, we investigated their role in the pathogenesis of experimental African trypanosomiasis in mice. We show that the production of IL-17 by spleen and liver cells and the serum IL-17 level increased after T. congolense infection in mice. Interestingly, infected highly susceptible BALB/c mice produced more IL-17 and had more Th17 cells than infected relatively resistant C57BL/6 mice. Paradoxically, neutralization of IL-17 with anti-IL-17 monoclonal antibody in vivo induced higher parasitemia in both the susceptible and the relatively resistant mice. Interestingly, anti-IL-17 antibody-treated mice had higher serum levels of alanine aminotransferase and aspartate aminotransferase, and the production of IL-10 and nitric oxide by liver cells was markedly decreased. Moreover, recombinant IL-17-treated mice exhibited significantly faster parasite control and lower peak parasitemia compared to control mice. Collectively, these results suggest that the IL-17/Th17 axis plays a protective role in murine experimental African trypanosomiasis.

High-yield amplification of Cryptosporidium parvum in interferon gamma receptor knockout mice.

To date, large-scale production of Cryptosporidium parvum oocysts has only been achieved by amplification in neonatal calves and sheep. Many laboratories currently depend on supplies from external sources and store oocysts for prolonged periods which results in progressive loss of viability. Six to 8-week-old interferon gamma receptor knockout (IFN gamma R-KO) mice on a C57BL/6 background were inoculated by gavage (2000 oocysts/animal). Fecal pellets were collected daily from 7 days post-infection (p.i.) up to 2 weeks p.i. Intestinal oocyst yield was assessed at days 11, 12 and 14 p.i. by homogenization of intestinal tissues. Ether extraction and one or more NaCl flotations were used to purify oocysts. Total recoveries averaged 2.6 x 10(6) oocysts/mouse from fecal material and 3.8 x 10(7) oocysts/mouse from intestinal tissues. Overall, 2.3 x 10(9) purified oocysts were obtained from 60 mice. Recovered oocysts were capable of sporulation and were shown to be infectious both in vitro and in vivo. Oocyst amplification was achieved in only 11-14 days with minimal expense. The simplicity of this method presents a practical alternative for the routine passage, maintenance and storage of C. parvum in biomedical laboratories.

TLR2, TLR4 and TLR9 are differentially modulated in liver lethally injured from BALB/c and C57BL/6 mice during Trypanosoma cruzi acute infection.

Toll-like receptor (TLR) family is crucial for microbial elimination and homeostasis, and has an important immunoregulatory role. In this study, we comparatively analyze innate immune response and tissular injury elicited in BALB/c and C57BL/6 (B6) mice during acute Trypanosoma cruzi infection. The liver was the most affected tissue with numerous cellular infiltrates, apoptotic cells and necrotic areas. The apoptotic rate, evaluated by Hoescht stain, was highest in liver of B6. Infection increased transaminase activities in both mouse strains, although they were highest in B6. BALB/c showed sixfold higher parasitemias than B6 but the latter presented higher mortality (80%) than BALB/c (40%). To gain insight into the molecular basis, we investigated the TLRs commitment in liver. We found that, TLR2 and TLR4 were up-regulated in BALB/c while they were down-regulated in B6. However, TLR9 showed a diminution in BALB/c and an increase in B6 at the end of infection. Moreover, an intensified pro-inflammatory cytokine profile was observed in B6 and F4/80+ and Gr1+ leukocytes were the predominant cells in liver from both mouse strains. Thus, altered TLR2, TLR4 and TLR9 signalling and exacerbate inflammatory cytokine profile could be responsible of the fatal hepatic damage observed in infected B6.

Host cell traversal is important for progression of the malaria parasite through the dermis to the liver.

The malaria sporozoite, the parasite stage transmitted by the mosquito, is delivered into the dermis and differentiates in the liver. Motile sporozoites can invade host cells by disrupting their plasma membrane and migrating through them (termed cell traversal), or by forming a parasite-cell junction and settling inside an intracellular vacuole (termed cell infection). Traversal of liver cells, observed for sporozoites in vivo, is thought to activate the sporozoite for infection of a final hepatocyte. Here, using Plasmodium berghei, we show that cell traversal is important in the host dermis for preventing sporozoite destruction by phagocytes and arrest by nonphagocytic cells. We also show that cell infection is a pathway that is masked, rather than activated, by cell traversal. We propose that the cell traversal activity of the sporozoite must be turned on for progression to the liver parenchyma, where it must be switched off for infection of a final hepatocyte.

[Biological characteristics of the Korean isolate KI-1 of Toxoplasma gondii].

OBJECTIVE: To study the biological characteristics of newly isolated Toxoplasma gondii Korean isolate-1 (KI-1). METHODS: The morphology and infectivity of KI-1 were observed by transmission electron microscopy and animal inoculation. Both RH and KI-1 antigens were detected by an anti-T. gondii monoclonal antibody (mAb), Tg563, and an anti-Neospora caninum mAb, 12B4. The genotype was determined by PCR-RFLP analysis of SAG2 locus. The sequence heterogeneity of the SAG1, ROP1 gene coding regions of the RH and KI-1 was detected by an automated sequencer. RESULTS: The morphology and infectivity of KI-1 were similar to those of RH strain. Both RH and KI-1 antigens reacted with Tg563, not with 12B4. In comparison to RH strain, the KI-1 showed a difference of seven positions of nucleotide substitutions and six positions of amino acid substitutions in both SAG1 and ROP1 gene coding regions. CONCLUSION: KI-1 is an isolate of T. gondii with strong virulence. Compared with RH strain, certain genetic differences exist.

[Study on methods for isolation and purification of Cryptosporidium parvum oocysts from mouse feces].

OBJECTIVE: To explore an applicable method for isolation and purification of Cryptosporidium parvum oocysts with high purity, recovery and vigor from mouse feces. METHODS: Four techniques were used for isolating and purifying C. parvum oocysts from mouse feces: modified saturated saline flotation, percoll gradient centrifugation, CsCl gradient centrifugation and the classical discontinuous sucrose gradient centrifugation. Oocysts received from the methods were used respectively to infect in vitro bovine fallopian tube epithelial cells (BFTE) and the development of the oocysts was examined under microscope after 48 h and 72 h cultivation. RESULTS: The number of oocysts received by the classical discontinuous sucrose gradient centrifugation [(2.86 +/- 0.08) x 10(7)] was significantly higher than that of percoll gradient centrifugation [(1.52 +/- 0.08) x 10(7)] (P<0.01) and CsCl gradient centrifugation [(2.46 +/- 0.13) x 10(7)] (P<0.05), but similar to that of the modified saturated saline flotation [(2.88 +/- 0.15) x 10(7)]. No significant difference was found on the number of oocysts by BFTE cultivation at 48 and 72 hours post-inoculation(P>0.05). Oocysts received from CsCl gradient centrifugation showed higher purity than those by discontinuous sucrose gradient centrifugation. CONCLUSION: In comparison to the classical discontinuous sucrose gradient centrifugation, operation of the modified saturated saline flotation is easier and faster, and the purity of oocysts isolated by CsCl gradient centrifugation is higher.

Heterogeneity of class I and class II MHC sequences in Schistosoma mansoni.

We investigated the genetic variations in class I and class II major histocompatibility complex (MHC) genes of Schistosoma mansoni and the effects of host MHC genotypes. S. mansoni was maintained in combinations of two mouse strains with different MHC genotypes, and the MHC gene sequences of the cercariae were investigated. The detected class I MHC gene sequences were variable, with high similarity between the H-2D(b) murine host and the parasite. For other combinations, however, the parasite sequence was homologous to those of anthropoids. All class II MHC sequences detected in S. mansoni were homologous to those of anthropoids. Our results suggest that the genetic variation in the MHC sequences of S. mansoni is derived in part from the current host, indicating horizontal transfer of the sequences from mammal to parasite.

A comparative study on mouse MHC class I sequences detected in Schistosoma japonicum recovered from BALB/c (H-2d) and C57BL/6 (H-2b) mice.

The mouse major histocompatibility complex (MHC) class I sequence was detected in all the 8-week-old Schistosoma japonicum recovered from BALB/c (H-2d) and C57BL/6 (H-2b) mice by in situ polymerase chain reaction (in situ PCR). The signals of the mouse class I MHC sequence were observed in the nuclei of the mesenchymal and reproductive cells of 8-week-old S. japonicum. Furthermore, the class I MHC sequence was detected in each DNA extracted from S. japonicum cercariae maintained in BALB/c and C57BL/6 mice by nested PCR. To prove both horizontal and vertical transmission of this sequence in schistosomes, we have used cercariae obtained from parasites maintained in BALB/c mice to infect C57BL/6 and BALB/c mice, and vice versa. The MHC sequences from adult worms were compared to the cercarial MHC and host MHC sequences. Nucleotide sequence comparisons between adult worm DNA, host (H-2d and H-2b mice) DNA and cercarial DNA used for the infection suggested that the sequence of mouse class I MHC was incorporated into schistosome adults and inherited throughout their life-cycle.

Litomosoides sigmodontis: dynamics of the survival of microfilariae in resistant and susceptible strains of mice.

Litomosoides sigmodontis in the BALB/c mouse is the only model of filariasis which allows the observation of the complete development in an immunocompetent mouse. In this study, we injected microfilariae (mf) intravenously, as well as into the pleural cavity, the site of natural release of mf from adult female worms, and followed the kinetics of elimination within the host. In susceptible BALB/c mice, mf circulated at high levels in the blood. In contrast, in C57BL/6 mice, which are refractory to full development, mf were eliminated rapidly from the peripheral blood. However, 6 days after intrapleural injection, viable larvae could be found in the pleural cavity and lung capillaries of both susceptible and resistant strains. The numbers of mf in the pleural cavity and lung capillaries in individual mice were significantly correlated, but not dependent on strain or peripheral microfilaraemia. Thus, although C57BL/6 mice showed enhanced production of nitric oxide by pleural exudate cells and a faster change in the numbers of circulating leukocytes after injection, rapid killing of mf by cell or nitric oxide-mediated mechanisms were not the reason for the different outcome. Furthermore, 3 h after iv injection, only a small percentage of mf could be recovered from the peripheral circulation, indicating the presence of a reservoir for mf containment. In conclusion, injected mf showed disparate dynamics of persistence within susceptible and resistant hosts, which is similar to the disparate outcome of natural infections with L. sigmodontis. This difference became obvious within 1 day after injection. The lung capillary system plays obviously a crucial part in regulation of microfilaremia. Our model also provides a possible means to explain frequent cases of occult infections in human filariasis.

Supplementation with Lactobacillus reuteri or L. acidophilus reduced intestinal shedding of cryptosporidium parvum oocysts in immunodeficient C57BL/6 mice.

The effect of L. acidophilus supplementation to reduce fecal shedding of Cryptosporidium parvum oocysts was compared to L. reuteri using C57BL/6 female mice immunosuppressed by murine leukemia virus (strain LP-BM5) inoculation. After 12 weeks post LP-BM5 inoculation, 15 immunosuppressed mice each were randomly assinged to one of the following treatment groups: historical control (group A), LP-BM5 control (group B), C. parvum (group C), L. reuteri plus C. parvum (group D) or L. acidophilus plus C. parvum (group E). Mice were pre-fed the L. reuteri or L. acidophilus bacteria strains daily for 13 days, challenged with C. parvum oocysts and thereafter fed the specified Lactobacillus regimens daily during the experimental period. Animals supplemented with L. reuteri shed fewer (p<0.05) oocysts on day-7 post C. parvum challenge compared to controls. Mice supplemented with L. acidophilus also shed fewer (p<0.05) oocysts on days 7 and 14 post-challenge compared to controls. Overall, Lactobacillus supplementation reduced C. parvum shedding in the feces but failed to suppress the production of T-helper type 2 cytokines [interleukin-4 (IL-4), IL-8)] which are associated with immunosuppression. Additionally, Lactobacillus supplementation did not restore T-helper type 1 cytokines (interleukin-2 (IL-2) and gamma interferon (IFN-gamma), which are required for recovery from parasitic infections. Altered T-helper types 1 and 2 cytokine production as a consequence of immunodysfunction permitted the development of persistent cryptosporidiosis while mice with intact immune system were refractory to infection with C. parvum. Reduction in shedding of oocysts observed in the Lactobacillus supplemented mice during deminished IL-2 and IFN-gamma production may be mediated by factors released into the intestinal lumen by the Lactobacillus and possibly other host cellular mechanisms. These observations suggest that L. reuteri or L. acidophilus can reduce C. parvum parasite burdens in the intestinal epithelium during cryptosporidiosis and may serve potential benefits as probiotics for host resistance to intestinal parasitic infections. L. acidophilus was more efficacious in reducing fecal shedding than L. reuteri and therefore may also have implication in the therapy of cryptosporidiosis during immunosuppressive states including human AIDS.

Blocked hepatic-stage parasites and decreased susceptibility to Plasmodium berghei infections in BALB/c mice.

The BALB/c strain of mice is comparatively more resistant to sporozoite infections of Plasmodium berghei than the C57BL6 strain. Infection with live sporozoites results in the formation of small hepatic forms in the BALB/c liver that persist for as long as 6 days. Upon infection with small numbers of sporozoites, some of the parasites are destroyed in the liver whereas the rest persist as blocked forms. When larger numbers of sporozoites are injected the same process occurs but, in addition, a fraction of the liver-stage parasites complete full development and give rise to blood forms. Although blocked liver forms persist until day 6 post-infection they actually develop to only 24 h of maturity. The nature of these persistent forms is similar to those obtained from irradiated sporozoite immunization. There is a stronger cell proliferation to liver-stage antigens by spleen lymphocytes of irradiated sporozoite-immunized BALB/c mice in comparison to that of immunized C57BL6 mice suggesting that a stronger priming to liver-stage antigens, probably due to the presence of blocked hepatic forms in the liver for a longer period of time (as compared to C57BL6), occurs in the BALB/c mice. This could be a reason for the long-lasting protective memory observed in BALB/c mice.