Immunization with the recombinant myosin regulatory light chain (FhrMRLC) in Adjuplex® adjuvant elicits a Th1-biased immune response and a reduction of parasite burden in Fasciola hepatica infected rats

The aim of this study was to assess the immune response and the protective efficacy elicited by the vaccination with the recombinant Fasciola hepatica myosin regulatory light chain (FhrMRLC) in Adjuplex® adjuvant against the infection with F. hepatica in rats. Four groups of 15 animals each were used for the study, one group was immunized with the recombinant F. hepatica MRLC in Adjuplex® adjuvant and the other groups remained as adjuvant, positive and negative control groups. The parasitological study showed that a statistically significant reduction of 65.1% and 82.1% in fluke burden and fecal egg count, respectively, was detected in vaccinated animals. In addition, vaccination with FhrMRLC induced a well-defined humoral and cellular immune response characterized by a significant production of specific IgG and IL-2, IL-12, TNF-α and IFN-γ; which confirms the immunogenic capacity of the FhrMRLC.

A Preliminary Study of a Lettuce-Based Edible Vaccine Expressing the Cysteine Proteinase of Fasciola hepatica for Fasciolosis Control in Livestock

Oral vaccination with edible vaccines is one of the most promising approaches in modern vaccinology. Edible vaccines are an alternative to conventional vaccines, which are typically delivered by injection. Here, freeze-dried transgenic lettuce expressing the cysteine proteinase of the trematode Fasciola hepatica (CPFhW) was used to orally vaccinate cattle and sheep against fasciolosis, which is the most important trematode disease due to the parasite's global distribution, wide spectrum of host species and significant economic losses of farmers. In the study, goals such as reducing the intensity of infection, liver damage and F. hepatica fecundity were achieved. Moreover, we demonstrated that the host sex influenced the outcome of infection following vaccination, with female calves and male lambs showing better protection than their counterparts. Since differences occurred following vaccination and infection, different immunization strategies should be considered for different sexes and host species when developing new control methods. The results of the present study highlight the potential of oral vaccination with plant-made and plant-delivered vaccines for F. hepatica infection control.

Immune response of rats vaccinated orally with various plant-expressed recombinant cysteine proteinase constructs when challenged with Fasciola hepatica metacercariae

Background

Cysteine proteinases of Fasciola hepatica are important candidates for vaccine antigens because of their role in fluke biology and host-parasite relationships. In our previous experiments, we found that a recombinant cysteine proteinase cloned from adult F. hepatica (CPFhW) can protect rats against liver fluke infections when it is administered intramuscularly or intranasally in the form of cDNA. We also observed considerable protection upon challenge following mucosal vaccination with inclusion bodies containing recombinant CPFhW produced in Escherichia coli.

In this study, we explore oral vaccination, which may be the desired method of delivery and is potentially capable of preventing infections at the site of helminth entry. To provide antigen encapsulation and to protect the vaccine antigen from degradation in the intestinal tract, transgenic plant-based systems are used.

Methodology

In the present study, we aimed to evaluate the protective ability of mucosal vaccinations of 12-week-old rats with CPFhW produced in a transgenic-plant-based system. To avoid inducing tolerance and to maximise the immune response induced by oral immunisation, we used the hepatitis B virus (HBV) core protein (HBcAg) as a carrier. Animals were immunised with two doses of the antigen and challenged with 25 or 30 metacercariae of F. hepatica.

Conclusions

We obtained substantial protection after oral administration of the plant-produced hybrids of CPFhW and HBcAg. The highest level of protection (65.4%) was observed in animals immunised with transgenic plants expressing the mature CPFhW enzyme flanked by Gly-rich linkers and inserted into c/e1 epitope of truncated HBcAg. The immunised rats showed clear IgG1 and IgM responses to CPFhW for 4 consecutive weeks after the challenge.

Infection with Fasciola hepatica, a liver fluke, is one of the most significant veterinary problems due to the worldwide distribution of this parasite, a wide spectrum of host organisms and the resulting economic loss. Human fasciolosis caused by F. hepatica is recognised by the World Health Organization as an important emerging but neglected tropical disease. Development of an effective vaccine against this disease is becoming a priority, especially as the appearance of drug-resistant strains undermine the currently employed drug-based treatments. The two primary issues when developing a vaccine are the selection of an appropriate vaccine antigen and the route of antigen administration. In our studies, we use one of the F. hepatica cysteine proteinases, which are promising antigens for vaccine construction. We evaluate the immunogenicity and protective ability of various modifications of this cysteine proteinase produced in plants. We show that substantial protection can be obtained when plant-expressed hybrid proteins are administered orally.

Variations in cercarial production and the level of in vitro activation of metacercariae of two different isolates of Fasciola hepatica

Fasciola hepatica infections cause large economic losses and are a serious veterinary medicine problem in many regions of the world. Recent studies examining fascioliasis in the bison population from Bialowieza National Park have shown that the prevalence of infection with this parasite is up to 100%. Liver flukes isolated from bison from Bialowieza National Park in Poland were compared with a fluke strain originally obtained from the Central Veterinary Laboratory, Weybridge, UK, to determine variations in cercarial production and establish the ability of their metacercariae to activate in vitro. Some small differences in cercarial production between the two isolates are shown, while significant differences in the ability of their metacercariae to activate in vitro were observed.

Antiparasitic DNA vaccines in 21st century

Demands for effective vaccines to control parasitic diseases of humans and livestock have been recently exacerbated by the development of resistance of most pathogenic parasites to anti-parasitic drugs. Novel genomic and proteomic technologies have provided opportunities for the discovery and improvement of DNA vaccines which are relatively easy as well as cheap to fabricate and stable at room temperatures. However, their main limitation is rather poor immunogenicity, which makes it necessary to couple the antigens with adjuvant molecules. This paper review recent advances in the development of DNA vaccines to some pathogenic protozoa and helminths. Numerous studies were conducted over the past 14 years of 21st century, employing various administration techniques, adjuvants and new immunogenic antigens to increase efficacy of DNA vaccines. Unfortunately, the results have not been rewarding. Further research is necessary using more extensive combinations of antigens; alternate delivery systems and more efficient adjuvants based on knowledge of the immunomodulatory capacities of parasitic protozoa and helminths.

In vivo studies of the early, peritoneal, cellular and free radical response in rats infected with Fasciola hepatica by flow cytometric analysis

Early recruitment of the peritoneal cell population was observed during migration of newly excysted juvenile flukes. The peritoneal lavages were examined for T cells, cytotoxic NK cells (CNK) and free radicals production of rats at an early stage of infection by Fasciola hepatica. Male Sprague-Dawley rats were infected with 50 metacercariae of F. hepatica and non-infected controls were euthanized 2, 4 and 7 days post infection (d.p.i.), respectively. The peritoneal fluid of experimental animals was analyzed by flow cytometry to estimate cell phenotypes. The peritoneal areas were infiltrated by inflammatory cells, particularly from numerous neutrophils, eosinophils and CD4+ lymphocytes, which were significantly higher for infected rats than non-infected. CNK cells dominated in the peritoneal fluid of infected rats as early as 2d.p.i. However, after 4d.p.i. there was a decreased level of CNK cells which may indicate a change from a cytotoxic natural killer (NK) to a regulatory NK response. The challenged group generated very high in vivo levels of inducible nitric oxide (NO) from eosinophils. Superoxide expression was very high in macrophages and neutrophils compared to the uninfected control. In conclusion, our studies suggest that early F. hepatica infection could directly affect lymphoid cells and generate a high in vivo NO production by eosinophils in the peritoneal cavity. Moreover juvenile flukes could stimulate the macrophages and neutrophils to generate H(2)O(2) radicals. The host parasite interactions resulting from immune response regulation by effector cells and immune evasion are discussed.

Detection of Giardia intestinalis assemblages A, B and D in domestic cats from Warsaw, Poland

Giardia intestinalis is a complex species divided into 7 assemblages (A - G). Two of them (A and B) are infective for both humans and animals. In cats four assemblages can occur: A, B, D, and F Assemblages A and B infect either cats, dogs and humans, assemblage D infects cats and dogs and assemblage F only cats. The purpose of this study was to determine the prevalence and genotypes of G. intestinalis in cats from Warsaw. From November 2006 to March 2007 a hundred sixty samples of stool were collected and examined by light microscopy. G. intestinalis cysts were detected in 3.75% of samples. DNA extracted from positive samples was used as template for PCR-RFLP using Giardia specific primers and the amplicons were sequenced. A comparison of the obtained DNA sequences with the Giardia sequences in the GeneBank database revealed assemblage A in 1.25% of the investigated cats, assemblage B in 1.25% and D in 1.25%.

The molecular evidence of Babesia microti in hard ticks removed from dogs in Warsaw (central Poland)

The purpose of this study was to specify the occurrence and prevalence of Babesia microti in hard ticks removed from dogs in Warsaw (central Poland). Among 590 collected ticks, 209 were identified as Ixodes ricinus, and 381 as Dermacentor reticulatus. B. microti DNA was detected in 11 out of 590 (1.86%) samples of ticks. The DNA of the parasite was detected only in lysates from female I. ricinus ticks (11 out of 193; 5.7%). The result of this study is the first evidence of B. microti in I. ricinus ticks in Warsaw.

Detection of the DNA of Borrelia afzelii, Anaplasma phagocytophilum and Babesia canis in blood samples from dogs in Warsaw

Each month, from March 2003 to February 2004, 34 blood samples from dogs were randomly selected from the blood samples delivered to two veterinary laboratories in Warsaw and tested for the DNA of Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, Babesia canis and Hepatozoon canis. Borrelia DNA was detected in seven of the 408 dogs, A phagocytophilum DNA was found in two, and B canis DNA was found in 48 (11.8 per cent). The DNA of H canis was not found in any of the blood samples. Sequencing of the seven Borrelia amplicons showed that only the genospecies Borrelia afzelii was present, the first time it has been detected in dogs in Poland.

New localities of Dermacentor reticulatus tick (vector of Babesia canis canis) in central and eastern Poland

Dermacentor reticulatus tick is a vector and final host of Babesia canis canis, protozoan parasite of the dog. In Poland and other European countries, endemic regions for canine babesiosis caused by B. canis canis are the same as endemic regions for D. reticulatus. In many of these regions, canine babesiosis is the most prevalent tick-borne disease in dogs. In Europe, increasing range of geographical distribution of D. reticulatus is observed. A consequence of this fact may be increasing range of canine babesiosis. D. reticulatus is one of the most common ticks occurring in Poland, however, it occurs mainly in the north-eastern and eastern part of the country, and there are many areas in which this species has not been reported yet. In this study, D. reticulatus ticks were collected from March 2007 to November 2008 in central and eastern Mazowsze region, and in some localities in Białystok and Lublin regions. Twenty four new sites for D. reticulatus, mainly in central and eastern regions of Mazowsze Province have been found. 18 localities are placed on banks of the fishing ponds or in river valleys and 6 are forests borders or barren lands and meadows, not situated near rivers or other water reservoirs. All tick-rich sites are localized in river valleys or on pond banks. However, statistical analysis showed that there were no differences in the density of ticks between groups of areas. These results show that the occurrence of D. reticulatus in newly detected areas has became endemic. Probably woodless, unregulated river valleys are important migration tracts for this species of tick and enable them to penetrate new territories. It seems likely that geographical range of D. reticulatus is widening from east to west of Poland what can induce an increase in the number of canine babesiosis cases in areas non-endemic for B. canis canis and its vector. Climate change may be also partially responsible for earlier beginning of tick's seasonal activity as well as for bigger faunal diversity (more potential host species both for adults and immature stages).

Prevalence of Babesia canis, Borrelia afzelii, and Anaplasma phagocytophilum infection in hard ticks removed from dogs in Warsaw (central Poland)

The purposes of this study were to specify the occurrence and prevalence of Babesia canis, Borrelia burgdorferi sensu lato, and Anaplasma phagocytophilum in ticks removed from dogs in Warsaw, and to determine the Borrelia species occurring in Ixodes ricinus ticks. Among 590 collected ticks, 209 were identified as I. ricinus, and 381 as Dermacentor reticulatus. DNA of B. canis was detected in 11% of D. reticulatus ticks. We found that 6.2% of I. ricinus ticks harbored B. burgdorferi s.l. specific DNA and 2.9% harbored A. phagocytophilum DNA. In these samples sequencing of the detected Borrelia amplicon confirmed infection with Borrelia afzelii genospecies. New sequences were submitted to the GenBank database (accession no. EU152128, EU152127, EU152126). This work is the first detection of B. afzelii and A. phagocytophilum in ticks from Warsaw, and the first survey for the prevalence of B. canis, B. afzelii, and A. phagocytophilum in ticks in central Poland.

Azithromycin in the treatment of a dog infected with Giardia intestinalis

Giardia intestinalis infection is a common cause of diarrhoea in humans and other mammalian species throughout the world. This report describes a case of a dog suffering from diarrhoea, infected with G. intestinalis, effectively treated with azithromycin. Azithromycin is an azalide, semisynthetic macrolide antibiotic having a large spectrum of activity against bacterial pathogens and some protozoa. In this case, Giardia infection in a dog was confirmed by microscopic examination and PCR. Sequencing of the detected Giardia amplicon confirmed infection with assemblage A-I. The dog received azithromycin administered at dose of 10 mg/kg per os, once a day for 5 days. After the therapy, the diarrhoea stopped. Effectiveness of the treatment was also confirmed by PCR and microscopic examination. This is the first report on the therapy of canine giardiosis with azithromycin. It seems that azithromycin can be considered as promising antibiotic for the control of Giardia infection in dogs.

Vaccine potential of inclusion bodies containing cysteine proteinase of Fasciola hepatica in calves and lambs experimentally challenged with metacercariae of the fluke

Despite intensive research efforts, progress in the development of effective anti-Fasciola hepatica vaccine has not been satisfactory. However, it has been found that cysteine proteinases of F. hepatica are very important candidates for a vaccine antigen because of their role in fluke biology and in the host-parasite relationship. In our previous experiments we found that recombinant cysteine proteinase which we have cloned from adult F. hepatica (CPFhW) can protect rats against the liver fluke infection when administered intramuscularly or when given intranasally in the form of cDNA. In the present experiments we aimed to evaluate the protectivity of the mucosal vaccination in calves and lambs with inclusion bodies containing recombinant CPFhW using different vaccination doses and various sites of antigen delivery. Female calves vaccinated intranasally with two doses of 300 microg of the recombinant CPFhW showed 54.2% protection against the subsequent challenge of 400 metacercariae (mc). Flukes which developed in vaccinated calves showed a reduction of reproductive potential. Male Corriedale lambs vaccinated at the age of 4 months demanded three doses of the antigen to gain 56.5% of protection to a challenge with 250 mc of F. hepatica. Vaccinated animals showed significantly lower blood eosinophil counts. No correlation was found between serum and mucosal IgG or IgA reacting with F. hepatica ES antigens and the protection level.

Hematological changes during the course of canine babesiosis caused by large Babesia in domestic dogs in Warsaw (Poland)

In the presented study we evaluated the hematological changes in samples of blood obtained from 248 dogs naturally infected with large Babesia. The evaluation included red blood cell count, hemoglobin concentration, hematocrit, mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), leucocyte counts, thrombocyte counts, mean platelet volume (MPV), morphology of erythrocytes and leucogram. The most common disorders in affected dogs were thrombocytopenia and anisocytosis. The count of erythrocytes below reference values was detected in 26.2% of dogs and 31.4% of affected animals presented hematocrit below the reference values. Hemoglobin concentration below the reference values was noted in 29% of dogs, an increase of MCHC above normal values was detected in 21% of examinated dogs and MCV below normal values was recognized in 2% of dogs. 60.5% of dogs presented anisocytosis, 25% poikilocytosis, 23.8% polychromasia, 19.7% hypochromia and 4.4% erythroblastosis. Thrombocytopenia was detected in 99.5% of dogs, but only 15.3% of examined animals showed increase of MPV, which suggests a response of the bone marrow. 36.3% of dogs had neutropenia, and 21.8% presented a left shift, 14.9% had the lymphocytosis and 7.2% lymphopenia.

Enteral vaccination of rats against Fasciola hepatica using recombinant cysteine proteinase (cathepsin L1)

Cysteine proteinases released by Fasciola hepatica play a key role in parasite feeding, migration through host tissues and in immune evasion. Hence, a recombinant cysteine proteinase (CPFhW) expressed as inclusion bodies in Escherichia coli was used for enteral vaccination of rats against fasciolosis. We managed to activate this proteinase and found it to have cathepsin L1-like substrate preference. Enteral vaccination of rats induced a 78-80% protection against challenge with fluke metacercariae (mc). The immunised rats showed clear immunological response. The challenge with mc caused a remarkable infiltration of eosinophils into the peritoneal cavity of both the vaccinated rats and challenge control rats. However, CD8+ and CD4+ lymphocytes appeared in significantly higher numbers in the peritoneal fluid of vaccinated rats than in controls.

Biochemical abnormalities observed in serum of dogs infected with large Babesia in Warsaw (Poland)

Biochemical abnormalities observed in canine babesiosis are related to the severity of the disease. The primary biochemical abnormalities found in affected dogs are: increase of the serum activity of transaminases and alkaline phosphatase, azotemia, and hypoglycemia. The purposes of this study were: 1) to estimate biochemical abnormalities in dogs infected with large Babesia in Warsaw and 2) to evaluate statistically changes observed during canine babesiosis in dogs from Warsaw. Samples of serum were collected from dogs naturally infected with large Babesia. Among 2023 positive samples, 202 were randomly selected. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), creatinine, blood urea nitrogen (BUN), total serum protein (TSP), albumin and blood glucose concentration were determined with a clinical chemistry analyser. Elevated activity of ALT, AST and ALP was detected accordingly in: 64.9, 92.6 and 31.7% of dogs. Elevated creatinine concentration and BUN were detected accordingly in 30.7 and 62.4% of dogs. Decrease of TSP, albumin, BUN, and hypoglycemia was detected accordingly in: 19.8, 32.7, 1.5 and 18.3% of dogs. The most common biochemical abnormalities found in affected dogs were: increase of activity of transaminases and ALP, elevated creatinine concentration, hypoalbuminemia and hypoglycemia. These abnormalities resulted from hepatopathy, renal failure and fasting.

[Search for protective antigens of hookworms]

Hookworms are very important blood sucking nematode parasites of humans and domestic animals. The host with a heavy infection can lose almost a cup of blood per day. This may contribute to anemia which is associated with many physical and mental developmental insults. The works on obtaining an effective hookworm vaccine have been lasting for about eighty years. Recent identifications of a number of bioactive molecules produced by larval and adult stages of Ancylostomatidae are very helpful for selecting of nematode proteins crucial for host-parasite interactions and promising vaccine antigens. Many of these molecules are involved in host skin penetration by infective larvae, intestinal tissue invasion and digestion of haemoglobin and/or other macromolecular substrates. However, the results of many vaccination trials using recombinant forms of these proteins showed no sufficient protection against experimental hookworm infections.

Occurrence of hard ticks in dogs from Warsaw area

Ticks are known as a vector of many viral, bacterial, rickettsial and protozoan infections of dogs. The threat with particular tick-transmitted disease depends very much on the tick species which feeds on the dog. In this paper we present results of research designed to identify tick species which attack dogs in the Warsaw area. Ticks were collected from dogs presented for medical examination in veterinary clinics in different parts of Warsaw. All of 590 tick specimens found on dogs belonged to the family Ixodidae (hard ticks). The majority (64.6 %) of the collected ticks were identified as Dermacentor reticulatus--vector of Babesia canis. The other tick species found on examined dogs was Ixodes ricinus. The male to female ratio was more than 3 times higher in D. reticulatus than in I. ricinus.

[Prevalence of Giardia intestinalis in domestic dogs in Warsaw]

INTRODUCTION

Giardia intestinalis is the most common intestinal protozoan parasite, which infects humans, dogs and other mammals throughout the world. So far eight genotypes of the parasite have been described of which four were found in dogs. Assemblages A-I and B infect either dogs or humans. Assemblages C and D occur only in dogs. The aim of the study was to determine the prevalence and genotypes of G. intestinalis in domestic dogs of Warsaw area.

MATERIAL AND METHODS

From October 2005 to March 2006 fecal samples were collected from 350 dogs and examined using light microscopy and PCR techniques.

RESULTS

5.14% of dogs was found to be positive for G. intestinalis by microscopy and prevalence of 9.14% was found by PCR. The PCR amplicons were sequenced and the DNA sequences were compared with Giardia sequences in GeneBank database. The analysis revealed assemblage A-I in 1.71% of dogs, assemblage C in 1.14% and assemblage D in 6.28% of dogs in Warsaw. According to literature, the genotype A can infect humans however a role of dogs as a reservoir of human giardiosis in Poland is not known.

Computational analysis of Ancylostoma ceylanicum cysteine proteinase

The potential tertiary structure of Ancylostoma ceylanicum cysteine proteinase was obtained by Automatic Program 3D-JIGSAW and used for finding homologues of known structure by VAST program. The results of computational analysis showed the presence of domains recognizing host immunoglobulins. Based on this analysis we suggest that this protein is involved in cleaving of host antibodies and therefore it may be promising vaccine candidate. In this paper we present the computational analysis of parasitic antigen which is very helpful in evaluation of the potential role of this protein.

[Influence of vaccination of calves with recombinant cysteine proteinase of Fasciola hepatica on development and infectivity of miracidia]

The aim of the study was to evaluate an influence of vaccination of the final host on F. hepatica development in intermediate hosts. Fluke eggs were isolated from the biliary tracts of calves vaccinated orally with recombinant cysteine proteinase of F. hepatica after the challenge infection and from control calves which received the infection only. To asses the effect of the vaccine on egg "hatch rate" the eggs were transferred to the Petri dishes with distilled water and incubated at 25 degrees C for 16-19 days. They were subsequently exposed to light for about 2 h, at a temperature of 27 +/- 1 degrees C, to stimulate sprouting of the miracidia and asses the egg hatchability. In order to evaluate infectivity and pathogenicity of the miracidia, single miracidium infections of Lymnea truncatula by F. hepatica were carried out under laboratory conditions using 4-mm-high snails. The prevalence of snail infections with F. hepatica was calculated using the ratio between the number of cercariae-shedding snails in each group and that of surviving snails. It appeared that the eggs isolated from immunized calves demonstrated significantly lower hatchability than the eggs isolated from non-vaccinated control hosts. Also, the proportion of infected snails as well as their mortality were lower after exposition to miracidia originating from vaccinated calves. It is suggested that effectors of the immune response in vaccinated calves inhibited in part biological activity of cysteine proteinases of the fluke which are known to be involved in egg shell formation, penetration of host's tissues and worm feeding.

Immunoprotective properties of transgenic plants expressing E2 glycoprotein from CSFV and cysteine protease from Fasciola hepatica

Immune responses were elicited in laboratory animals after oral vaccination by transgenic plants (lettuce and alfalfa) expressing the E2 glycoprotein of Classical Swine Fever Virus (CSFV) or cysteine protease from Fasciola hepatica. ELISA analyses demonstrated that the oral route is effective in inducing a specific antibody response against these antigens in mice.

The immune response of rats to vaccination with the cDNA or protein forms of the cysteine proteinase of Fasciola hepatica

Our previous experiments have shown that intramuscular injection of Sprague-Dawley rats with a pcDNA 3.1 vector carrying cDNA encoding for a cysteine proteinase (CP) of F. hepatica may induce a high level of protection against subsequent infection with F. hepatica metacercariae (mc). The aim of the present study is to compare the immune response of Sprague-Dawley rats vaccinated intranasally with plasmid containing cDNA of CP of the fluke and intramuscularly or intraperitoneally with the recombinated enzyme protein to challenge with fluke metacercariae. In addition, protection following intranasal DNA vaccination was evaluated. Two experiments were carried out. In the first experiment rats were vaccinated twice with 50microg of cDNA containing plasmid or with 100microg protein of recombinated CP. Three weeks after the second vaccination rats were challenged orally with 25 mc. On days 0, 21, 42 and 63 after the challenge blood samples were collected for the evaluation of white blood cell, eosinophil and specific antibody responses. During the second experiment groups of five male and female rats were vaccinated twice intranasally with CPcDNA then challenged with 30 mc and dissected 5 weeks later. Results obtained in the experiments suggested that intranasal immunisation of rats with CPcDNA seems to favour a Th2 regulated antibody response. Intramuscular or intraperitoneal injections of CP protein stimulate both Th1 and Th2-dependent antibodies. Mean worm burdens found in rats vaccinated intranasally 5 or 10 weeks after the challenge were reduced by 61-75% in comparison with the challenge controls which suggests that intranasal vaccination with CPcDNA may protect hosts against F. hepatica infection.

c-DNA vaccination against parasitic infections: advantages and disadvantages

Recently developed technology for DNA vaccination appears to offer the good prospect for the development of a multivalent vaccines that will effectively activate both the humoral and cell mediated mechanisms of the immune system. Currently, DNA vaccination against such important parasitic diseases like malaria, leishmaniosis, toxoplasmosis, cryptosporidiosis, schistosomosis, fasciolosis offers several new opportunities. However, the outcome of vaccination depends very much on vaccine formulations, dose and route of vaccine delivery, and the species and even strain of the vaccinated host. To overcome these problems much research is still needed, specifically focused on cloning and testing of new c-DNA sequences in the following: genome projects: different ways of delivery: design of vectors containing appropriate immunostimulatory sequences and very detailed studies on safety.

Preliminary analysis of the proteolytic enzymes in the excretory-secretory products of the adult stages of the dog hookworm Uncinaria stenocephala

The paper describes an introductory characterisation of proteinases present in the excretory-secretory products (ESP) of adult Uncinaria stenocephala. In SDS-PAGE gelatine substrate gels ESP resolved as a six bands of proteolytic activity, with a molecular weight of 182, 159, 98, 50, 39 and 26 kDa. The 98 and 39 kDa components were serine proteinases. The 50 kDa band was sensitive to a metalloproteinase inhibitor. The 26 kDa component was highly sensitive to cysteine proteinase inhibitors and was also partially inhibited in the presence of EDTA. The bands of 182 and 159 kDa were sensitive to a Zn-metalloproteinase inhibitor. The enzymes present in ESP showed the highest proteolytic activity at pH 8-9. Quantitative analysis revealed maximum proteolytic activity of the polypeptides of 159 and 182 kDa at pH 7; 98 and 26 kDa at pH 8 while the 50 kDa and 39 kDa components showed the highest activity at pH 9.

[Usefulness of the molecular techniques for detecting and/or identifing of parasites and fungi in humans and animals or pathogens transmitted by ticks (Part I)]

After a long period of using basic microscopic, immunological and biochemical methods for diagnosis, rapid development of nucleic acids investigation enabled introduction of specific and sensitive methods of detection of pathogenic agents on the molecular level. Among others, polymerase chain reaction (PCR), discovered in mid of 80'ies and then automatized, offered an attractive alternative to conventional testing systems. In this paper we describe reliable diagnostic tests widely used in the world, including Poland, and capable of detecting different disease agents as parasites and fungi in clinical specimens and pathogens of emerging zoonotic diseases in ticks. The possibilities of using molecular methods for determination of Plasmodium falciparum drug resistance is also discussed. Moreover, the report offers information concerning kinds of molecular tests and institutions in which there are executed.

Humoral response in hamsters following vaccination with cDNA encoding acey-1 cysteine proteinase of Ancylostoma ceylanicum

The humoral response in hamsters following vaccination against Ancylostoma ceylanicum infections with DNA construct was investigated. Groups of hamsters were injected intramuscularly with plasmid pcDNA 3.1. containing cDNA of ACEY-1 cysteine proteinase. Vaccination resulted in IgG antibody response to somatic extracts of adult A. ceylanicum. The highest level of antibodies was observed seven weeks after vaccination.

Molecular cloning of a cysteine proteinase cDNA from adult Ancylostoma ceylanicum by the method of rapid amplification of cDNA ends using polymerase chain reaction

The hookworm Ancylostoma ceylanicum is a parasite of great importance in human and veterinary medicine. The most promising vaccination trials against hookworm infections are based on antigens belonging to the proteinase family. The aim of the present research was to isolate a cysteine proteinase gene from A. ceylanicum. This was achieved by rapid amplification of cDNA ends using polymerase chain reaction (RACE-PCR). A set of consensus oligonucleotide primers was designed to anneal to the conserved coding regions of cysteine proteinase. The PCR products were cloned and sequenced. The novel sequence displayed a high degree of homology with genes of cysteine proteinases known from other hookworm species. In the coding region the nucleotide identity with accp-1, the cysteine proteinase gene of A. caninum, reaches 84.3%. Analysis of the expression of acey-1. the cysteine proteinase gene of A. ceylanicum, suggests that it is produced exclusively in the gland cells of either adult worms or blood-feeding stages of A. ceylanicum.

Successful DNA immunisation of rats against fasciolosis

The liver fluke Fasciola hepatica contributes to great economic and health losses in the cattle industry in many countries, including Poland. Unfortunately, no vaccine against fasciolosis is commercially available. We have designed a DNA vaccine and tested it in rats. Groups of male or female rats received one intramuscular injection of 50 microg of a pcDNA 3.1 vector carrying cDNA encoding for a cysteine proteinase of F. hepatica. The plasmid was diluted in saline containing 0.05% bupivacaine. Control rats were injected with empty plasmid or not injected at all. All rats were challenged with 45 metacercariae of the fluke on day 28 of the experiment. Seven weeks after the challenge infection fluke burdens were evaluated in vaccinated and control rats. Male rats vaccinated with cysteine proteinase cDNA revealed 100% protection against F. hepatica infection. Females immunised in the same way exhibited the reduction of fluke burden by 74%.

[Usability of PCR-based techniques for diagnosis of parasitic infections in ruminants]

Sensitivity and specificity are the two most important criteria that define the quality of a diagnostic technique. DNA probes and PCR-based techniques may simplify the diagnosis of parasitic infections. PCR is a powerful diagnostics tool. The method enables detection of even a very small amount of DNA. An extreme sensitivity of the PCR, being a major advantage of the method is also a cause of potentially false positive results. To achieve reliable diagnostic results several modifications have been introduced to the classic PCR procedure. PCR and PCR-based techniques are currently increasingly used for detection of parasitic infections, to differentiate closely related species which are difficult to be recognised with traditional methods, for estimation of parasite burdens, and for the detection of drug resistant strains.

[The new generations of vaccines against parasites]

The protection of humans and domestic animals against parasitic infections remains a major goal, especially in light of developing of drug resistant strains in many parasite species. "Classic" vaccines are based on attenuated infective stages of protozoan and helminth parasites. Although such vaccines are effective in confering host immunity against several protozoan (coccidiosis, giardiosis, toxoplasmosis) diseases and one helminth (dictyocaulosis) they are very unstable and expensive. Recombinant techniques enable to obtain protective antigens quickly and in considerable quantities, cultivating of the bacteria and purification of the recombinant protein is less expensive than the maintenance of host animals and isolation of the protective antigens from harvested parasites. Moreover, the cloned protective antigens may be deprived of epitopes responsible for immunopathology. However, at present only one anti-parasite recombinant protein vaccine is commercially available (TickGARD). Such a situation may result from that many protective parasitic antigens cannot be expressed in bacteria or yeast in anative from. DNA vaccines present many advantages over protein ones. Firstly, the antigenic proteins synthesised within the host cell possess an appropriate molecular structure and undergo a post-translational modifications specific for a native protein. The next advantage of DNA vaccines is that DNA is easier to handle and more resistant than proteins to temperature changes. DNA vaccines are likely to induce novel mechanisms of immune response, which may be beneficial in case of parasitic invasions. Costs of DNA vaccines are comparable, and may be even lower, in comparison to recombinant protein vaccines. The main obstacle preventing the use of DNA vaccines is still lack of the complete knowledge concerning mechanisms of their action. Vaccines based on transgenic plants (=edible vaccines), expressing the protective parasitic antigens, present another promising approach in research on anti-parasitic vaccines. Such vaccines may be of special importance in prevention of infections with gastrointestinal parasites.

Immune response of lambs to vaccination with Ostertagia circumcincta surface antigens eliciting bile antibody responses

Immune responses to surface antigens of infective larvae of Ostertagia circumcincta recognized by bile antibodies of sheep immune to challenge were studied in 5-month-old Finn-Dorset male lambs. The sheep were vaccinated subcutaneously with 2 doses of 25 micrograms/kg body weight of surface proteins immunoprecipitated by bile antibodies derived from protected lambs. These antigens were purified from immune complexes by affinity chromatography and then injected with beryllium hydroxide as an adjuvant. The immunized lambs were challenged with 5 x 10(4) L3 and the worm burdens evaluated on day 21 post challenge. These were significantly (P < 0.01) lower in the vaccinated group than in the challenged controls (72% protection). The mucosal and bile IgM, recognizing the L3 surface, showed significantly higher levels in the vaccinated lambs compared to the challenge controls. Mucosal and bile IgA antibody levels against the same antigens were low and no significant differences were observed between vaccinated and control lambs.

Somatic antigens of adult Dicrocoelium dendriticum recognised by bile antibodies of naturally infected cattle

Bile samples, from slaughtered cattle harbouring between 120 and 280 adult lancet flukes, were used to investigate the range of somatic proteins inducing local antibody responses in naturally infected animals. Lancet fluke infections induced local (bile) antibody responses against Tris-buffered saline (TBS) soluble, sodium dodecyl sulphate (SDS) soluble and 2-mercaptoethanol (2-Me) soluble somatic proteins of adult Dicrocoelium dendriticum. IgA antibody isotypes predominated in the response against buffer-soluble somatic antigens, whereas SDS-soluble and 2-Me-soluble proteins induced similar level of both IgA and IgG1 antibodies. Analysis of the antigens recognised by particular isotype-specific bile antibodies suggests that different antigens preferentially induce isotype restricted antibody responses. The bile antibody response was highly species specific, only one antigen from somatic protein extracts of Fasciola hepatica being precipitated by bile samples showing the highest reactivity against D. dendriticum.

Surface and excretory/secretory antigens of fourth-stage larvae and adult Ostertagia circumcincta

With the use of an enzyme-linked immunosorbent assay (ELISA), it was revealed that surface antigens of both adult and fourth-stage larvae (L4) of Ostertagia circumcincta induced high levels of serum IgG antibodies, while serum IgA antibody levels were low but increased significantly (P < 0.01) after infection. Immunofluorescence studies on the surface of viable L4 and adult nematodes showed that the IgG response was stage-specific only in animals vaccinated with adult surface extracts. The results of Western blot analysis using these antibodies suggested that at least eight polypeptides were shed from the L4 surface to the environment and that infection induced (or boosted) IgG antibody against a further four polypeptides. A comparison of reactivity of pre- and post-infection sera of sheep vaccinated with adult nematode surface antigens suggested that only one of the antigens stripped from the nematode surface was immunogenic and/or present in a concentration sufficient to induce an IgG response following parenteral vaccination. Infection boosted the IgG antibodies to a further four polypeptides. Only one polypeptide of 63 kDa seems to be shed in vivo from the adult nematode surface. Ten to eleven antigens were recognised in adult excretory/secretory products by serum IgG of multiple-infected sheep.

The effect of adjuvant and specific or non-specific vaccination on development of protective immunity of rabbits against Trichostrongylus colubriformis infection

Adult New Zealand rabbits were vaccinated subcutaneously with one dose of 100 micrograms adult nematode phosphate buffered saline-soluble proteins (PBS-ASP, groups I and II), a detergent-soluble fraction of adult somatic proteins (DS-ASP, group III) or three doses of 1 mg normal rabbit serum proteins (group IV). Injections of the immunogens in groups II, III and IV were accompanied with beryllium hydroxide, Be(OH)2 as an adjuvant. Vaccinated rabbits and also those of group V (naive) were challenged orally with 10,000 infective larvae of T. colubriformis 14 days after antigen injection and necropsied 2 weeks later. A single dose of PBS-ASP induced 33.5% protection when the antigen was given alone (group I) and 69.4% when injected with Be(OH)2 (group II). A detergent-soluble fraction of ASP given with the adjuvant provided 87.2% protection (group III), whilst non-specific vaccination with serum proteins plus Be(OH)2 elicited 99% protection (group IV). Mesenteric lymph node leukocyte responses were measured using a leukocyte migration inhibition assay. A significant response was observed only in group IV. In ELISA tests IgA antibodies specific to PBS-ASP reached the highest level in the intestinal mucosa of groups I and II and in the bile of groups I and III. Antibody levels of IgG isotype were similar in the intestinal mucosa of all the immunized groups. Nematode antigen was detected using a 'sandwich' ELISA method in faecal protein extracts of rabbits of groups II and III on days 2-6 after challenge.

Pathophysiology of the periparturient egg rise in sheep: a possible role for IgA

The relationship between anti-parasite IgA antibody levels in plasma and the periparturient egg rise in sheep was investigated. Ostertagia circumcincta larvae (5000 third stage larvae three times weekly) were administered to three groups of seven adult immune ewes from 12 weeks before until three weeks after lambing (group 1) or from six (group 2) or 14 (group 3) weeks before until three weeks before lambing. Seven additional ewes were not challenged (group 4 controls). Ewes in groups 1, 2 and 4 received anthelmintics 14 weeks before lambing. Challenge of the pregnant ewes with O circumcincta larvae resulted in substantial increases in faecal egg counts only during the periparturient period regardless of the larval dosing regimen. Furthermore, the periparturient rise in faecal egg counts was closely associated with a significant increase in anti-parasite IgA antibody levels in plasma. This rise in IgA antibody levels occurred at a time when IgA is transported from the gut to milk during early lactation. It is postulated that this may lead to a temporary reduction in abomasal antibody levels of ewes and hence permit the establishment of larvae and, or, the emergence and development of inhibited larvae and thereby lead to the periparturient rise in faecal egg count.

Immune responses of sheep to surface antigens of infective larvae of Ostertagia circumcincta

Immune responses to surface antigens of infective larvae of Ostertagia circumcincta were studied in 5-month old Finn-Dorset male lambs. The sheep were vaccinated subcutaneously with 2 doses of 25 micrograms/kg body weight of infective larvae surface or somatic extracts and Freund's or beryllium hydroxide adjuvants. It was found that only in lambs vaccinated with L3 surface extracts and beryllium hydroxide as an adjuvant did worm burdens differ significantly (P less than 0.01) from those of challenge controls (71.7% protection). Sheep vaccinated with the same antigenic preparation but administered with Freund's adjuvant or with beryllium adjuvant and somatic extracts demonstrated rather poor protection (32.4 and 30.5% respectively). All the vaccinated sheep showed a high IgG response to L3 surface antigens while significant levels of serum and bile IgA reacting with the surface extracts were only detected in those lambs vaccinated with L3 surface extracts and beryllium hydroxide. In immunofluorescence tests serum IgA of this group reacted with the whole surface of exsheathed larvae or with the site of opening of excretory pore while IgG antibodies reacted strongly with the anterior and posterior parts of the infective larvae. Both IgA and IgG responses to surface antigens were stage specific.

Influence of adjuvants on immunity in rabbits vaccinated with infective larval somatic proteins of Trichostrongylus colubriformis

Adult New Zealand rabbits were vaccinated at 2-week intervals with three doses of 100 micrograms of infective larval somatic proteins (L3SP) administered subcutaneously with Freund's complete adjuvant (FCA) or beryllium hydroxide and then challenged orally with 10,000 L3. Groups of rabbits immunized orally with three doses of 5000 or 2000 L3 served as vaccination controls. Intestinal worm burdens on Day 21 after challenge revealed that beryllium hydroxide effectively potentiates the protective immunogenicity of L3SP. The level of protection obtained using the beryllium adjuvant (94.8%) was nearly as high as that in rabbits immunized with three doses of 5000 L3 (99.8%). Rabbits vaccinated using FCA showed very poor immunity (29.5%). Local and systemic antibody levels detected by radioimmunoprecipitation tests using 125I-L3SP showed very little correlation with the degree of protection. The beryllium hydroxide-treated group demonstrated significantly higher bile IgA antibody levels than other experimental rabbits. FCA-treated rabbits developed a much higher serum precipitating antibody response, detectable using gel double diffusion tests, than the beryllium group. Also, mucosal IgA antibody levels detected on Day 21 after challenge were significantly higher in the FCA group than in other groups.

Surface antigens of Obeliscoides cuniculi inducing local and systemic humoral responses in infected rabbits

125I-radiolabelled surface proteins of various developmental stages of Obeliscoides cuniculi were used to analyze serum and gastrointestinal immunoglobulin responses of the host to primary infection with 10,000 larvae of the nematode, using a radioimmunoprecipitation method. Serum IgM, IgA, and IgG antibodies reacted mostly with infective larval and adult nematodal surface proteins. The highest binding activity was shown by IgG against the surface of infective larvae on days 56 and 86 after infection. Local (gastric mucosal) antibodies were also predominantly directed against surface antigens of infective larvae and adults, although considerable binding of the fourth-stage larval surface proteins by gastric mucosal IgG occurred 35 days after infection. Physicochemical analysis of the radiolabelled surface antigens revealed that the strongest antigenicity was found in proteins with molecular weights of 40,000 and 145,000. Nonspecific binding demonstrated in our tests by infective larval surface proteins was associated with particles with a molecular weight of 550,000.

Inhibition phenomena mechanisms in experimental obeliscoidosis in rabbits. II. Local and systemic antibody responses

A series of experiments was carried out using adult outbred Polish race rabbits of both sexes infected, during spring or autumn, with 10,000 larvae of Obeliscoides cuniculi, either fresh or stored at 4 degrees C. Extracts of mucosal proteins and bile were collected at postmortem 6 or 12 weeks after infection. Antibody levels were determined in antisera, bile and stomach mucosa by haemagglutination and precipitation tests. Local antibody responses were demonstrated in the stomach and bile, and reactions were obtained with the tissue fluids by haemagglutination and precipitation tests with worm antigens and ES products. Additionally, some specific immunological response was observed in the circulation during the primary infection. These results suggest a clear-cut relationship between increased levels of these antibodies and either larval inhibition or worm expulsion during O. cuniculi infections.

Local and systemic antibody responses in gerbils following vaccination with irradiated or non-irradiated Trichostrongylus colubriformis larvae

Groups of 10 Mongolian gerbils, Meriones unguiculatus, were vaccinated with 1,500 gamma-irradiated Trichostrongylus colubriformis infective larvae (L3) or with non-irradiated larvae. 25 days later five gerbils from each group were necropsied and the remaining gerbils challenged with 1,500 non-irradiated T. colubriformis infective larvae. Systemic, local intestinal and coproantibody levels were compared in each group of gerbils 25 days after vaccination and 26 days after challenge. Strong local intestinal and faecal antibody responses were detected. Coproantibodies reflected antibody levels in the intestinal contents and in mucosal extracts. The results gave further support to the view that coproantibody measurements provide a sensitive index of immunity at mucosal surfaces to intestinal parasites.