Evaluation of the protective immune response of an attenuated strain of Toxoplasma gondii with long-term passages on the Gecko cell line

Toxoplasma gondii is an obligate intracellular parasite that causes the zoonoses disease, named toxoplasmosis, with global prevalence. Until now, no cost-effective treatment method has been found to deal with toxoplasma, and vaccination is the best way to deal with the infection. In the case of pathogenic protozoa, mainly live vaccines have had successful results compared to other vaccine platforms. This study evaluated the efficacy of a live experimental vaccine through long-term passages on the Gecko cell line (Z1) in inducing a protective immune response in BALB/c mice. Thirty mice were divided into three equal groups; G1: the immunized/challenged group (injection of attenuated strain), G2: the immunized/unchallenged group (injection of attenuated strain), and G3: the control group (injection of culture medium).One month after immunization, the studied mice were challenged with 1ₓ103 live tachyzoites of Toxoplasma acute RH strain. We performed Serological investigations, including evaluating antibodies, interferon-gamma (IFN-γ), and interleukins 2, 4, 10, and 12 (IL-2,4,10,12). At the study's end, a molecular test was performed on brain and liver tissues in the immunized groups to check the presence of parasites. The results from the serological tests for the evaluation of antibodies, interferon-gamma (IFN-γ), and interleukins 10 and 12 (IL-10, 12) show a significant difference (p < 0.05) between the vaccinated group and the control group, which are essential indicators of protective immunity against toxoplasma infection. Thus, in the vaccinated group, the survival rate of mice against the challenge was 70%. Also, in group two (G2), the attenuated strain of Toxoplasma gondii had no pathogenicity, and all mice survived until the end of the study period. Molecular results also showed the absence of parasites in the brain and liver tissues in this immunized group and the parasite was found in only one case of liver tissue in G1. Therefore, the attenuated strain has caused significant and protective humoral and cellular immune responses in vaccinated groups. This study showed that with the long-term passage of the acute strain on the Gecko cell line, it is possible to quickly obtain a non-diseased attenuated strain with the ability to induce protective immunity. This successful finding can introduce further research to achieve a promising vaccine in the target animals.

Neospora caninum and Toxoplasma gondii infections in one-humped camels (Camelus dromedarius) in central desert of Iran

The protozoan parasite Neospora caninum infects carnivores as definitive and a wide range of mammals as intermediate hosts. This parasite is regarded as an important cause of abortion in cattle worldwide, causing significant economic losses. Although there is serological evidence of infection in Old World camelids, the significance of N. caninum in these animal species is still poorly understood. The aim of this study was to use molecular and histological methods to detect N. caninum in the blood and tissues of 100 slaughtered one-humped camels (Camelus dromedarius) in Iran. For this, genomic DNA was extracted from blood, brain, portal lymph node and liver of the camels, and nested-PCR assay followed by sequencing were performed. Besides, paraffin-embedded tissue sections were stained with hematoxylin and eosin (H&E) and studied microscopically. In addition, immunohistochemical staining for N. caninum was attempted on brain samples with positive PCR results. All animals were tested for antibodies against N. caninum and Toxoplasma gondii by whole tachyzoite-agglutination tests. N. caninum DNA was detected in blood, brain, and portal lymph node, but not in the liver of two (2%) camels. Histopathological examination revealed cysts resembling N. caninum in brain samples of one of these camels; however, immunohistochemical staining for N. caninum and T. gondii did not allow a morphological identification. IgG antibodies to N. caninum and T. gondii were detected in 36% and 35% of the camels, respectively. This study provides the first insight into direct detection of N. caninum in C. dromedarius in Iran. Further molecular studies on aborted fetuses, stillborn animals and cases of perinatal mortality are needed to understand the possible involvement of N. caninum in cases of reproductive failure. As the definitive hosts of N. caninum are domestic and wild canids, producers should be advised to monitor and limit exposure of their camelids to these species and their feces.

Potential Protective Role of Cyrtopodion Scabrum in Antioxidant Parameters in Serum and Liver of Rats with 5-FU-Induced Oxidative Damage

Chemotherapy is the main approach for the treatment of cancer; however, it often causes unpleasant oxidative damages. Therefore, the development of an effective alternative/complementary therapy with improved tumor suppression efficiency and lower adverse effects is highly required. Recently, it has been shown that Cyrtopodion scabrum extract (CsE) is an effective and selective tumor suppressor medicine. The present study investigated the antioxidant activity of Cyrtopodion scabrum homogenate (CsH) and CsE and their effects on attenuating 5-fluorouracil (5-FU)-induced liver dysfunction in rats. A total of 60 male rats (weight: 200-220 g) were divided into six groups and treated for 14 days. The control (group I) and 5-FU (group II) groups received distilled water and 5-FU, respectively. The other four groups were orally administered with CsE, CsH, CsE+5-FU, and CsH+5-FU (groups III to VI), respectively by gavages based on a daily schedule. The 5-FU-induced oxidative damage was evaluated by changes in the weight and food and water intake during the treatment and antioxidant parameters in the liver and serum of the treated rats. The obtained data indicated that the administration of CsH and CsE significantly improved liver function and defense system of antioxidants by attenuating the levels or activities of malondialdehyde, superoxide anion, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase and decrease of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione S-transferase, total antioxidant capacity, glutathione, total protein, and albumin in the liver and serum, induced by 5-FU treatment. The obtained data of the current study suggested that CsH and CsE play a protective role in the imbalance elicited by 5-FU and can be used as alternative/complementary supplements with 5-FU to reduce oxidative damages which is the consequence of reactive oxygen species production in cancerous patients.

Composition and Anti-Toxicity Effects of Cichorium intybus Distillate on Serum Antioxidant Status in Carbon Tetrachloride-Treated Rats

The role of oxidative stress in female fertility is a compelling area for research. According to traditional medicine, Cichorium intybus, known as Kasni, is believed to improve fertility. For this purpose, the effects of C. intybus distillate (CI) on blood antioxidant status were assessed in rats with carbon tetrachloride (CCl4)-induced toxicity. The rats were assigned to four experimental groups of Control, CI, CCl4, and CI+CCl410 (n=10 in each group). The level of antioxidant enzymes, such as glutathione peroxidase (GPx), glutathione reductase (GR), and catalase (CAT), as well as lipid peroxidation and reduced glutathione (GSH) level, were measured in serum samples. In the second part of the study, the antioxidant activity and phytochemical composition of the hydrodistillate of C. intybus aerial parts were determined by DPPH radical scavenging and gas chromatography-mass spectrometry analysis, respectively. The administration of CCl4 decreased the enzyme activities of GPx, GR, and CAT which were significantly ameliorated after CI administration. The decreased level of serum GSH following CCl4 administration was not considerably elevated in the CI+CCl4 group. Furthermore, the level of malondialdehyde in the serum of CI+CCl4 rats was decreased, compared to the CCl4 group. The main compositions of the essential oil from the C. intybus distillate were the antioxidants of Pulegone (8.10%), Piperitenone (7.68%), dihydroactinidiolide (5.0%), and carvone (4.18%). The antioxidant activity of the distillate was obtained at 75&micro;g/l using the DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) test. In general, the results of the present study demonstrated that C. intybus distillate, as a safe herbal remedy, can attenuate CCl4-induced oxidative damages via boosting the endogenous antioxidant defense system.

Potential Protective Role of Cyrtopodion Scabrum in Antioxidant Parameters in Serum and Liver of Rats with 5-FU-Induced Oxidative Damage

Chemotherapy is the main approach for the treatment of cancer; however, it often causes unpleasant oxidative damages. Therefore, the development of an effective alternative/complementary therapy with improved tumor suppression efficiency and lower adverse effects is highly required. Recently, it has been shown that Cyrtopodion scabrum extract (CsE) is an effective and selective tumor suppressor medicine. The present study investigated the antioxidant activity of Cyrtopodion scabrum homogenate (CsH) and CsE and their effects on attenuating 5-fluorouracil (5-FU)-induced liver dysfunction in rats. A total of 60 male rats (weight: 200-220 g) were divided into six groups and treated for 14 days. The control (group I) and 5-FU (group II) groups received distilled water and 5-FU, respectively. The other four groups were orally administered with CsE, CsH, CsE+5-FU, and CsH+5-FU (groups III to VI), respectively by gavages based on a daily schedule. The 5-FU-induced oxidative damage was evaluated by changes in the weight and food and water intake during the treatment and antioxidant parameters in the liver and serum of the treated rats. The obtained data indicated that the administration of CsH and CsE significantly improved liver function and defense system of antioxidants by attenuating the levels or activities of malondialdehyde, superoxide anion, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase and decrease of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione S-transferase, total antioxidant capacity, glutathione, total protein, and albumin in the liver and serum, induced by 5-FU treatment. The obtained data of the current study suggested that CsH and CsE play a protective role in the imbalance elicited by 5-FU and can be used as alternative/complementary supplements with 5-FU to reduce oxidative damages which is the consequence of reactive oxygen species production in cancerous patients.

Molecular and Serological Evaluation of Neospora caninum Infection in Dogs from a Rural Setting in Fars Province, Southern Iran

Background:

Dogs, as the definitive host of Neospora caninum, are important in the epidemiology of this parasitic infection. We aimed to determine the prevalence of N. caninum infection in a dog population from a rural setting in Fars Province, Southern Iran, using a combination of molecular and serological techniques.

Methods:

This cross-sectional study was carried out in Nov 2018 in three rural districts, Sar Mashhad, HosseinAbad, and Tolesaman located in Kazeroun Township in Fars province, southern Iran. Blood samples were taken from 60 stray and household dogs. Dogs’ sera were tested for antibodies against N. caninum, using a Neospora-Modified Agglutination Test. Moreover, dogs’ buffy coats were tested for Neospora DNA, using a molecular method.

Results:

Anti-Neospora antibodies were detected in sera of 4 out of 60 dogs, corresponding to a seroprevalence rate of 6.7%. Out of 25 female dogs, 1 was seropositive and of 35 males, 3 were seropositive, yet the differences were not statistically significant. The infection was more prevalent in adult dogs (> 12 months), nevertheless, the differences between age and Neospora seropositivity was not statistically significant. N. caninum DNA was not detected in the buffy coat of any of the studied dogs.

Conclusion:

Findings of the study indicate that N. caninum is a common infection in dogs in rural areas of Fars province in southern Iran. The infected dogs might be a potentially important source of N. caninum infection to livestock in the area.

The evaluation of attenuated Neospora caninum by long-term passages on murine macrophage cell line in prevention of vertical transmission in mice

To date, there is no effective vaccine to prevent abortion or vertical transmission associated with neosporosis in cattle. In the present study, the efficacy of a live experimental vaccine of Neospora caninum attenuated (NCa) by long-term serial passages on a murine macrophage cell line was evaluated in the prevention of vertical transmission and abortion in the mouse model. Forty non-pregnant mice were randomly divided into four equal groups including non-immunized/challenged (injected with PBS); positive control (inoculated with un-attenuated NC-1 tachyzoites); immunized/challenged (inoculated with NCa attenuated strain) and immunized/non-challenged or vaccinated (inoculated with NCa) groups. Following pregnancy synchronization, both the immunized and control mice were challenged with virulent live NC-1 tachyzoites (2.5 × 10⁶) in the mid-pregnancy stage. The number of abortions and post-natal pup mortalities was recorded. Serological, molecular, and histopathologic examinations were employed to evaluate the efficacy of the vaccine and the vertical transmission rates. Results indicated that the live attenuated N. caninum strain (NCa) could significantly reduce the risk of abnormal parturitions and fetal mortality in the vaccinated group (20 %) compared to the non-immunized/challenged group (80 %). Also, the NCa strain reduced the lesion score in the brain of the offspring (0.3 vs 1.9) compared to the non-immunized/challenged group (P < 0.05). The molecular assay showed a decrease in the parasite DNA detection rates from 83 % and 77 % in the non-immunized/challenged group to 27 % and 0 % in the vaccine group in the brain and liver tissues, respectively. While in the immunized/non-challenged group no parasite DNA was detected in the brain tissue samples of the pups. Serological analyses showed that NCa strain was able to stimulate the humoral immunity and create effective protection against neosporosis with a moderate systemic IFN-γ response. In conclusion, the NCa strain could significantly (P < 0.05) reduce the risk of vertical transmission and proved to be a safe vaccine while conferring significant levels of protection in the laboratory mice.

Sperm quality and hormonal levels in C57BL/6 mice infected with Neospora caninum

Neospora caninum is a major pathogen of cattle and dogs, and neosporosis is widespread in five continents. In this study effect of experimental neosporosis on sperm quality of C57BL/6 mice in different days was investigated. Based on the results sperm concentration was not changed in infected groups but neosporosis induced a significant decrease in epididymis sperm motility at 60 days post infection. A significant increase in the number of abnormal sperms at five, 15, 30 and 60 days post infection was found. At days 15, 30 and 60 post infection testosterone concentrations were significantly low in infected groups and FSH level was significantly high in infected groups at five and 30 days post infection. LH level was decreased in infected groups, but the difference was significant at five, 15 and 30 days post infection. Comparison of TSH and T4 levels between groups revealed a significant decrease in infected groups at five, 15, 30 and 60 days post infection. Except 15 days post infection T3 levels decreased significantly in infected groups. GPX activity, MDA and TAC level was significantly increased in infected mice at five days post infection. In this study neosporosis is associated with hypogonadotrophic gonadal insufficiency in infected C57BL/6 male mice.

An investigation of the concurrency of anti-Neospora antibody and parasitemia in water buffalo (Bubalus bubalis) in northwest of Iran

Neospora caninum is an obligate intracellular parasite causing abortion and reproductive failure in ruminants. Here, the seroprevalence of Neospora DNA and anti-Neospora antibodies and the correlation between the DNA and the antibody using polymerase chain reaction (PCR) and a new developed whole cell-based enzyme-linked immunosorbent assay (ELISA) in water buffalo (Bubalus bubalis) were investigated. To determine the level of anti-Neospora antibody, 83 serum samples were collected from buffaloes in the northwest of Iran. Plates were coated with 2 × 10⁶ whole Neospora tachyzoites and the anti-Neospora antibody level was determined by calculating the ratio of sample/positive control (S/P) optical densities (ODs) in the ELISA. All samples with the ration of 0.50 or above were accounted as positive. To confirm the presence of Neospora DNA, the serum samples were directly subjected to PCR and nested PCR for detection of Neospora NC5 gene without the DNA isolation process. A total number of 83 buffalo serum samples were examined for the presence of anti-N. caninum immunoglobulin G and Neospora DNA. All samples with the S/P ratio of 0.50 or above (16 samples, 19.27%) were also positive for Neospora DNA. All samples with OD less than 0.50 (34 samples, 40.96%) were negative for Neospora DNA. However, 33 samples with the S/P ratio of bellow 0.50 (39.75%) showed a significant level of antibody. A 100% correlation was observed between high levels of the anti-Neospora antibody and Neospora DNA in the serum of water buffalo, and the whole N. caninum tachyzoites have the potency to be used as antigens for detection of the parasite in ELISA.

Embryonated pigeon eggs as a model to investigate Neospora caninum infection

It has been shown that embryonated chicken eggs can be used as animal models for experimental infections. The aim of the present study was to investigate pigeon embryonated eggs as animal models for experimental neosporosis. An infection with Neospora caninum Nc1 isolate was conducted in chicken and pigeon embryonated eggs to evaluate LD50. After calculation of LD50, 2LD50 of tachyzoites were injected into the eggs. Macroscopic changes of each embryo were observed, and immunohistochemistry (IHC) and molecular methods were used to investigate the parasitic distribution in the tissues. In the present study, histopathological changes were considered, and sections of those used for histopathological examination including the heart, liver, brain and chorioallantoic (CA) membrane were also subjected to IHC. Pigeon embryos showed more macroscopic changes than chicken embryos. A hemorrhage of the CA membrane was the main gross lesion. Microscopic examination of tissues revealed acute neosporosis due to hemorrhage, necrosis and infiltration of mononuclear inflammatory cells. Based on IHC and molecular results, the parasite DNA was detected in the liver, heart and CA membrane. As with chicken embryonated eggs, these results reinforce the susceptibility of pigeon embryonated eggs to N. caninum, and provide new insights into using an inexpensive and available animal model for N. caninum research. The results of the present study suggest that pigeon embryos may be a good choice for studying the biology of N. caninum in living organisms.

Suspension culture of Besnoitia caprae by murine macrophage

Besnoitia caprae is a tissue cyst-forming protozoan that infects goats and has considerable economic importance in certain regions of Asia and Africa. Murine macrophage J774 cell line was inoculated with tachyzoites of Besnoitia caprae (BC-Pars isolate) collected from mice. A significant growth of tachyzoites was observed in J774. Mice were inoculated with tachyzoites harvested from J774 cell culture. Skin samples from the mice infected with tachyzoites of BC-Pars were PCR positive. One mouse showed alopecia and skin lesions on 45 DPI. Dermal lesions started from around right eye and gradually developed more and more. After euthanasia on 60 DPI, histopathological evaluation of skins around the eye showed necrosis of the epidermis and follicular adnexa with chronic inflammatory cell infiltration. Histopathological sections of their skin showed the presence of necrosis and mononuclear cell infiltration. To the authors' knowledge, this is the first report of successful production of Besnoitia caprae tachyzoites was achieved in vitro by suspension culture technique. Another interesting finding is the report of the alopecia and skin lesions around the eye in mouse that quite similar to lesions of goats due to infection of Besnoitia caprae.

First isolation and establishment of in vitro culture of Theileria lestoquardi from a naturally infected cow

Theileria infected cell line was isolated from the prescapular lymph node of an adult crossbred cow. Molecular study confirmed this cell line of bovine lymphocyte has been transformed by the Theileria lestoquardi. This strain of T. lestoquardi designated Ka-6 and sheep were inoculated with this strain didn't show any clinical signs of theileriosis which shows the significance of this cell line to develop a tissue-culture vaccine against malignant ovine theileriosis. Contrary to accepted belief that the T. lestoquardi not capable of causing disease in cattle, the present study describes the first isolation and establishment of in vitro culture of T. lestoquardi-infected cell line from a naturally infected cow with typical singes of acute theileriosis.

Use of chicken embryonated eggs for evaluating the virulence of Toxoplasma gondii

The objective of the present study was to examine the virulence of Toxoplasma gondii RH strain tachyzoites in embryonated eggs after continuous passage in Vero cell line. The first T. gondii tachyzoites was considered low passage (no passage) and then passaged for 80 times on Vero as high passage. Groups of 9-day-old embryonated eggs with ten eggs in each group were inoculated with 10²,10³ and 10⁴ of low or high-passage T. gondii tachyzoites, and any mortality was recorded. Suitable samples from different tissues (liver, heart, and brain) of the dead embryos were collected for histopathological study. In this study, the mortality in group 10³ and 10⁴ was observed, but there was no significant differences in mortality rate in T. gondii low passage and high passage. This finding exactly correspond to previous studies that were performed in mice as animal model for T. gondii RH strain. Thus on base of this study we could introduce the embryonated eggs as an appropriate animal model to evaluate the virulence of T. gondii tachyzoites.

Prevalence of O157:H7 and non-O157 E. coli in Iranian domestic sheep

The aim of the present study was the isolation of both E. coli O157 and non-O157 in sheep. Verotoxins (VT) 1, 2 and eae genes were tested for this propose. Sheep faces are an important source of Shiga toxin-producing Escherichia coli (STEC). Escherichia coli O157:H7 is a highly virulent food-borne pathogen and threat to public health. Rectal swab samples from sheep were collected during 2009-2010. Conventional plating and Polymerase Chain Reaction (PCR) were carried out according to virulence factors (Stx1, Stx2 and eaeA).There significant differences between prevalence of STEC and session were observed. It was at highest in spring and late summer. Six (3.92%) sheep carcasses were contaminated by E. coli O157:H7.Only six samples were positive by PCR specific for the VT2 gene and produced verocytotoxin VT2, whereas all isolates were negative for the presence of VT1 and eae virulence genes considered. Geographical variations and season may be influenced in the prevalence rate. The composition of the gastrointestinal flora may be changed by different diet and, therefore O157 STEC rate in sheep and lamb was different. Iranian sheep indicated as a natural host of E. coli O157 strains therefore, may be potentially pathogenic for humans. This is the first report of E. coli O157 detection from sheep in Iran.

Suspension culture of Neospora caninum by Theileria annulata-infected cell line

There are some limiting aspects of scaling up the Neospora caninum tachyzoites in continuous cell lines, particularly as related to the absence of surface attachment. In this study, suspension cell culture of Theileria annulata-infected lymphoblastoid (TIL) was used as a host cell for the continous production of N. caninum tachyzoites. The numbers of free tachyzoites in the medium supernatant were showed regularly increased up to the day 6 post-cultivation. Transmission electron microscopy demonstrated that N. caninum tachyzoites invaded the TIL cells and multiplied intracellularly. This showed that the tachyzoites were successfully proliferated in TIL cells and were released in complete Dulbecco's modified Eagle's medium. This is a successful report of in vitro cultivation of N. caninum tachyzoites achieved by using suspension host cell culture.

Comparison of use of Vero cell line and suspension culture of murine macrophage to attenuation of virulence of Neospora caninum

In this study the tachyzoite yields of Neospora caninum were compared in two cell lines: Vero (African Green Monkey Kidney) and suspension culture of murine macrophage (J774) cell lines. Then, N. caninum were continuously passaged in these cell lines for 3 months and the effect of host cells on virulence of tachyzoites was assessed by broiler chicken embryonated eggs. Inoculation was performed in the chorioallantoic (CA) liquid of the embryonated eggs with different dilutions (0.5 × 10(4), 1.0 × 10(4), 1.5 × 10(4)) of tachtzoites isolated from these cell cultures. The mortality pattern and pathological changes of the dead embryos and hatched chickens were noted. Tissue samples of brain, liver and heart were examined by histopathological and detection of DNA of parasite by polymerase chain reaction (PCR). Also, consecutive sections of the tissues examined histologically were used for immunohistochemical (IHC) examination. Embryos inoculated with tachyzoites derived from Vero cell line (group V) showed a higher mortality rate (100%) than the embryos that received tachyzoites derived from J774 cell line (group J) (10% mortality rate). The results of this study indicated that the culture of N. caninum in J774 cell led to a marked increase in the number of tachyzoite yields and rapid attenuation in comparison to Vero, so the results were confirmed by IHC and PCR. This study is the first report of the significant effect of host cell on the attenuation of virulence of N. caninum tachyzoites. These findings could potentially provide a practical approach in the mass production of N. caninum tachyzoites, and also in producing live attenuated vaccine.

Development of a disperse dye immunoassay technique for detection of antibodies against Neospora caninum in cattle

In this study a disperse dye immunoassay method was standardized and evaluated for detection of antibodies against Neospora caninum in cattle. Sera from 150 cattle with a recent history of abortion were collected and tested by commercial ELISA kit and a standardized in-house dye immunoassay system. The positivity rate for the sera used in this study was 34.6% for the disperse dye immunoassay (DDIA) compared to 32% obtained by ELISA kit. This study showed no significant difference between DDIA and ELISA. The results indicated that the DDIA provide an economic, simple, rapid and robust test for detection of N. caninum infection in cattle.

Evaluation of Cross Immunity and Histopathological Findings in Experimentally Infected BALB/c Mice with Neospora caninum and Besnoitia caprae

BACKGROUND

Caprine besnoitiosis is an economically important disease of goats. Neospora caninum, another coccidian parasite of worldwide distribution, infects several animal species and is a major cause of abortion in cattle. Combined infections of N. caninum and Besnoitia caprae can occur in geographical areas endemic for both species of parasite in goats. This experiment was conducted to investigate the possible cross-immunity between these two infections in experimentally infected BALB/c mice.

METHODS

Forty BALB/c mice were divided into four equal groups. The mice of Groups 1 and 4 were inoculated with 1×10(6) live virulent tachyzoites of N. caninum (NC-1), while animals of Groups 2 and 3 were inoculated with sterile tissue culture medium. Each mouse in Groups 1 and 2 was challenged 28 days later with 1×10(6) live virulent bradyzoites of B. Caprae (BC-1).

RESULTS

Following the challenge, the mice in Groups 1 and 2 showed 100% morbidity and 100% mortality within 9 days post infection, while all the animals of Groups 3 and 4 remained alive. The dead animals were necropsied. The survivors (mice in Group 3 and 4) were euthanized 9 days after inoculation and the gross and histopathological lesions in different organs were investigated.

CONCLUSION

Immunization and challenge experiments with lethal dose of B. caprae in the highly susceptible BALB/c mice showed no cross-protection between N. caninum and B. caprae.

Immunohistochemical and polymerase chain reaction studies in Neospora caninum experimentally infected broiler chicken embryonated eggs

The diagnostic characteristics of immunohistochemistry (IHC) and polymerase chain reaction (PCR) methods were studied in the tissues of broiler chicken embryos experimentally infected by Neospora caninum. An infection with N. caninum NC-1 isolate was conducted in 70 broiler chicken embryonated eggs randomly divided into seven equal groups. After 8 days of incubation, six groups were inoculated with 10, 10(2), 10(3), 10(4), 10(5), and 10(6) doses of tachyzoites/embryonated egg. The 7th group was considered as control. The mortality rate and pathological changes of the dead embryos and hatched chickens up to 60 days old were noticed. Consecutive sections to those used for histopathological examination including the liver, heart, brain, and chorioalantoic (CA) membrane were subjected to IHC. The intensity and distribution of the immunostaining was graded as highly to mildly positive. For PCR procedure, DNA was extracted from 50mg of the tissues and primer pair Np21/Np6 was used for amplification of the Nc-5 gene. The results of the immunosignaling ranged from variable degrees of mild to moderate staining as dark-brown to brown and coarsely to finely granular, mostly within the cytoplasm of infected cells such as the endothelial cells of blood vessels. The parasite aggregation was more predominant in the heart than other tissues. Immunoreactivity for N. caninum antigen was multifocally moderate positive in the heart, liver and CA of the 10(3) dose, and also heart, liver, brain and CA of the 10(4) dose. IHC showed mildly positive in the liver and heart of the chicken embryos infected with 10 and 10(2) tachyzoites, as well. The results of the PCR confirmed the existence of the parasite in all of the examined tissues from the 10(3) and 10(4) doses. In conclusion, the results indicate a good agreement between IHC and PCR in diagnosis of neospora antigen in the infected tissues.

Seroprevalence of Neospora spp. in horses in South of Iran

Neospora caninum, an apicomplexan protozoan parasite, is recognized as a major cause of abortion in cattle. However, limited information is presently available on the seroprevalence of Neospora antibodies in horses worldwide. The aim of the present study is to determine serological prevalence of Neospora infection in horses in Iran. Blood samples were obtained from 200 horses and tested for serum antibodies against Neospora spp. by the Neospora modified direct agglutination test (N-MAT). Antibodies were found in 64 (32%) horses being tested with titers of 1:80. This is the first serological survey for Neospora antibodies performed on horses in Iran.

Study on Theileria lestoquardi antigens as potential vaccine candidates

Theileria lestoquardi is the causative agent of malignant theileriosis of sheep and goats, causing morbidity and mortality in these animals worldwide. Western blot analysis based on T. lestoquardi schizont antigens was carried out using sera collected from Iranian sheep, which had been immunized with T. lestoquardi schizont-infected cells. The results of Western blot analysis demonstrated that schizont-immunized animals produced antibodies reacting with protein bands at 73, 42, 20, 14, and 12 kDa. Comparison of the results of the current Western blotting test with earlier studies of Theileria spp. revealed two immunogenic schizont proteins with molecular weights of 73 and 42 kDa shared between T. annulata and T. lestoquardi. Two other proteins with molecular weights of 14 and 12 kDa have not been previously found in other Theileria species. Our results suggest that the 73-kDa protein could be a potential vaccine candidate and that the 14- and 12-kDa proteins could be considered as diagnostic antigens.

Phylogenetics of Theileria species in small ruminants

Our study is based on the collection of blood and ticks from sheep in Iran and Italy. Polymerase chain reaction (PCR) testing was performed to target the 18S rRNA gene and RLB was performed using previously published probes. In Italy and Iran 78.7% and 76.0% of the sheep were PCR positive, which after sequencing and RLB showed that they were Theileria ovis and Theileria lestoquardi, respectively. Phylogenetic analysis was performed using the Clustal W multiple sequence alignment program and our sequences were compared with more than 50 others already published in the EMBL database. Our T. lestoquardi sequences linked with other T. lestoquardi sequences from Iran, Tanzania, and Sudan and Theileria annulata showed the importance of having species-specific probes between these two species. However, distinctive clades were found between T. lestoquardi ticks and those found in sheep blood. Italian T. ovis seemed to be closer to Theileria spp. from Namibia and Iran than with other T. ovis from Spain, Turkey, Tanzania, and Sudan adding some information to the controversy about this species. However, some confusion was found on the existing database where the location of pathogens, years, and species names was inaccurate and when available sequences were not always appropriately used. This article will discuss our results and some comparisons with other phylogenetic approaches.

Blood-brain barrier and neuronal membrane transport of 6-[18F]fluoro-L-DOPA

The transport of 6-[18F]fluoro-L-3,4-dihydroxyphenylalanine ([18F]FDOPA) across the blood-brain barrier (BBB) and neuronal membranes was compared with that of L-3,4-dihydroxyphenylalanine (L-DOPA) in rats. The carotid injection method was used as a direct measurement of [18F]FDOPA, 1-[14C]-L-DOPA, and 3-[14C]-L-DOPA transport across the BBB, while isolated nerve terminals were used to examine neuronal membrane transport of [3H]-L-DOPA. [18F]FDOPA appeared to use the same large neutral amino acid carrier for BBB transport as L-DOPA and L-phenylalanine. In addition, carbidopa [L-alpha-hydrazino-alpha-methyl-beta-(3,4-dihydroxyphenyl)propionic acid] was found not to have direct interference with the transport carrier on the BBB, but indirectly inhibited aromatic L-amino acid decarboxylase (AAAD) activity in brain endothelium by depletion of pyridoxal phosphate, a necessary cofactor of the enzyme. In striatal and cortical synaptosomes, [3H]-L-DOPA uptake was inhibited by non-radioactive L-DOPA, FDOPA, and 6-fluoro-L-meta-tyrosine (6-FMT). The inhibition was significantly greater in terminals isolated from the striatum than in those from the cerebral cortex. FDOPA, 6-FMT, and L-DOPA equally inhibited the neuronal transport of [3H]-L-DOPA. This suggests that FDOPA and 6-FMT compete with L-DOPA at similar transport sites at the neuronal membrane.

Quantitative imaging of gene induction in living animals

Methods to repeatedly, non-invasively, and quantitatively image gene expression in living animals are rapidly emerging and should fundamentally change studies of gene expression in vivo. We previously developed assays utilizing positron emission tomography (PET) to image reporter gene expression. In this paper we: (1) describe a new bi-directional, tetracycline-inducible system that can be used to pharmacologically induce target gene expression and to quantitatively image induced expression by using a PET reporter gene; (2) demonstrate the potential of this system in transient and stable cell transfection assays; and (3) demonstrate the ability to repetitively and quantitatively image tetracycline and tetracycline analog induction of gene expression in living animals. We utilize the dopamine type-2 receptor (D(2)R) and the mutant herpes-simplex virus type 1 thymidine kinase (HSV1-sr39tk) reporter genes to validate this system. We utilize microPET technology to show that quantitative tomographic imaging of gene induction is possible. We find a high correlation (r(2) = 0.98) between 'target' and reporter gene expression. This work establishes a new technique for imaging time-dependent variation of gene expression both from vectors with inducible promoters and in transgenic animals in which pharmacologic induction of gene expression must be monitored. These techniques may be applied both in gene therapy and for the study of gene expression in transgenic animals.

Human pharmacokinetic and dosimetry studies of [(18)F]FHBG: a reporter probe for imaging herpes simplex virus type-1 thymidine kinase reporter gene expression

9-[4-[(18)F]fluoro-3-(hydroxymethyl)butyl]guanine ([(18)F]FHBG) has been used as a reporter probe to image expression of herpes simplex virus type-1 thymidine kinase (HSV1-tk) reporter gene in living animals. Our aim was to study the kinetics, biodistribution, stability, dosimetry, and safety of [(18)F]FHBG in healthy human volunteers, preparatory to imaging patients undergoing HSV1-tk gene therapy.

METHODS

[(18)F]FHBG was synthesized with a specific activity of 37,000--444,000 GBq/mmol and a radiochemical purity > 99%. Ten healthy volunteers consented to participate in the study. A transmission scan was obtained before bolus injection of 70.3--229.4 MBq [(18)F]FHBG into a hand vein, followed by dynamic PET imaging with 4 consecutive emission scans. Warmed hand-vein blood was withdrawn at various times after injection for blood time--activity measurements. Electrocardiography, blood pressure, and blood and urine pharmacologic parameters were measured before and after injection of the [(18)F]FHBG tracer (n = 5). The stability of [(18)F]FHBG in the urine was analyzed. Attenuation-corrected images were reconstructed using the ordered-subsets expectation maximization algorithm. Image region-of-interest time-activity data were used with the MIRD program to estimate absorbed radiation dosages.

RESULTS

[(18)F]FHBG had rapid blood clearance; only 8.42% +/- 4.76% (mean +/- SD) of the peak blood activity remained at approximately 30 min. The average ratio of plasma activity to whole-blood activity during the study was 0.91 +/- 0.04. Penetration of [(18)F]FHBG across the blood-brain barrier was not observed. The primary routes of clearance were renal and hepatobiliary. High activities were observed in the bladder, gut, liver, and kidneys, but <0.0002% of the injected dose per gram was observed in other tissues. In the urine, 83% of activity 180 min after injection was stable [(18)F]FHBG. Blood and urine pharmacologic parameters did not change significantly after injection of the [(18)F]FHBG tracer. The bladder absorbed the highest radiation dose.

CONCLUSION

[(18)F]FHBG has the desirable in vivo characteristics of stability, rapid blood clearance, low background signal, biosafety, and acceptable radiation dosimetry in humans. This study forms the foundation for using [(18)F]FHBG in applications to monitor HSV1-tk reporter gene expression.

Direct correlation between positron emission tomographic images of two reporter genes delivered by two distinct adenoviral vectors

Biodistribution, magnitude and duration of a therapeutic transgene's expression may be assessed by linking it to the expression of a positron emission tomography (PET) reporter gene (PRG) and then imaging the PRG's expression by a PET reporter probe (PRP) in living animals. We validate the simple approach of co-administering two distinct but otherwise identical adenoviruses, one expressing a therapeutic transgene and the other expressing the PRG, to track the therapeutic gene's expression. Two PET reporter genes, a mutant herpes simplex virus type 1 thymidine kinase (HSV1-sr39tk) and dopamine-2 receptor (D(2)R), each regulated by the same cytomegalovirus (CMV) promoter, have been inserted into separate adenoviral vectors (Ad). We demonstrate that cells co-infected with equivalent titers of Ad-CMV-HSV1-sr39tk and Ad-CMV-D(2)R express both reporter genes with good correlation (r(2) = 0.93). Similarly, a high correlation (r(2) = 0.97) was observed between the expression of both PRGs in the livers of mice co-infected via tail-vein injection with equivalent titers of these two adenoviruses. Finally, microPET imaging of HSV1-sr39tk and D(2)R expression with 9-(4-[(18)F]fluoro-3-hydroxymethylbutyl) guanine ([(18)F]FHBG) and 3-(2-[(18)F]fluoroethyl)spiperone ([(18)F]FESP), utilizing several adenovirus-mediated delivery routes, illustrates the feasibility of evaluating relative levels of transgene expression in living animals, using this approach.

8-[18F]Fluoropenciclovir: an improved reporter probe for imaging HSV1-tk reporter gene expression in vivo using PET

We have synthesized and evaluated 8-[18F]fluoropenciclovir (FPCV) and compared it with 8-[18F]fluoroganciclovir (FGCV) for monitoring the expression of herpes simplex virus type 1 thymidine kinase (HSV1 -tk) reporter gene in cell culture and in vivo.

METHODS

C6 rat glioma cells stably transfected with HSV1-tk (C6-stb-tk+) and control C6 cells were evaluated for their ability to accumulate FGCV versus FPCV. For in vivo studies, 15 mice were injected by tail vein with increasing levels of an adenoviral vector carrying HSV1-tk. Forty-eight hours later the mice were injected with FPCV and killed 3 h later. The percentage injected dose per gram (%ID/g) liver was then determined. Two additional mice were studied by microPET and autoradiography using FPCV to image adenoviral-mediated hepatic HSV1-tk reporter gene expression. A tumor-bearing mouse (C6 control and C6-stb-tk+) was imaged with FDG, FGCV, and FPCV. Two mice carrying tumors expressing two different reporter genes, HSV1-tk and dopamine type 2 receptor (D2R), were also imaged by microPET using FPCV (day 1) and 3-(2'-[18F]fluoroethyl)spiperone (FESP) (day 2).

RESULTS

FPCV shows a significantly greater accumulation in C6-stb-tk+ cells than does FGCV (P < 0.05). Over identical ranges of adenoviral administration, mouse liver shows a higher %ID/g liver for FPCV (0%-9%) compared with our previously reported results with FGCV (0%-3%). In C6 control and C6-stb-tk+ tumor-bearing mice, FPCV has a greater accumulation than does FGCV for equal levels of HSV1-tk gene expression. In mice carrying tumors expressing either HSV1-tk or D2R reporter genes, there is a corresponding retention of FPCV and FESP, respectively.

CONCLUSION

These results indicate that FPCV is a better reporter probe than is FGCV for imaging lower levels of HSV1 -tk gene expression in vivo. The results also reveal the ability to monitor the expression of two distinct reporter genes in the same animal using reporter probes specific for each gene.

Distribution volume of 3-O-methyl-6

The distribution volume (DV) of 6-[F-18]fluoro-L-DOPA (FDOPA) in the cerebellum recently has been linked using positron emission tomography (PET) to plasma large neutral amino acid (LNAA) concentrations in monkeys. In this article the authors provide additional experimental support for this relation by directly measuring the DV as the steady-state tissue to plasma radioactivity ratio in rats using a labeled LNAA analog 3-O-methyl-6-[F-18]FDOPA (OMFD), a compound that has no known specific enzyme or receptor interactions in brain tissue. The measured DV for OMFD (tissue OMFD concentration/plasma OMFD concentration) was found to be inversely related to plasma LNAA concentrations. The relation (DV = 1.5-0.00094*[LNAA], R--2 = 0.79) resulted in an 8% DV decrease per 100 nmol/mL plasma LNAA increase within the observed range of 330 to 510 nmol/mL. This was similar to recent noninvasive observations with FDOPA PET in vervet monkeys and with 6-[F-18]Fluoro-m-tyrosine PET in squirrel monkeys. The OMFD striatum to cerebellum (Str/Cb) ratio was greater than 1.0 for all measurements, averaging 1.09 +/- 0.04, and was approximately equal to the Str/Cb LNAA ratio of 1.12 +/- 0.05. This current study verifies the variation of DV of OMFD or FDOPA as a function of plasma LNAA concentrations and suggests the possibility of using OMFD for measuring cerebral LNAA noninvasively with PET.

Seeing is believing: non-invasive, quantitative and repetitive imaging of reporter gene expression in living animals, using positron emission tomography

The ability to monitor reporter gene expression in living animals and in patients will permit longitudinal examinations both of somatically transferred DNA in experimental animals and patients and of transgenic constructs expressed in experimental animals. If investigators can non-invasively monitor the organ and tissue specificity, the magnitude and the duration of gene expression from somatically transferred DNA and from transgenes, conceptually new experimental paradigms will be possible. If clinicians can non-invasively monitor the location, extent and duration of somatically transferred genes, they will be better able to determine the correlations between expression of therapeutic genes and clinical outcomes. We have developed two reporter gene systems for in vivo reporter gene imaging in which the protein products of the reporter genes sequester positron-emitting reporter probes. The "PET reporter gene" dependent sequestration of the "PET reporter probes" is subsequently measured in living animals by Positron Emission Tomography (PET). We describe here the principles of PET reporter gene/PET reporter probe in vivo imaging, the development of two imaging systems, and the validation of their ability to non-invasively, quantitatively and repetitively image reporter gene expression in murine viral gene transfer and transgenic models.

A mutant herpes simplex virus type 1 thymidine kinase reporter gene shows improved sensitivity for imaging reporter gene expression with positron emission tomography

We are developing assays for noninvasive, quantitative imaging of reporter genes with positron emission tomography (PET), for application both in animal models and in human gene therapy. We report here a method to improve the detection of lower levels of PET reporter gene expression by utilizing a mutant herpes simplex virus type 1 thymidine kinase (HSV1-sr39tk) as a PET reporter gene. The HSV1-sr39tk mutant was identified from a library of site-directed mutants. Accumulation (net uptake) of the radioactively labeled substrates [8-(3)H]penciclovir ([8-(3)H]PCV), and 8-[(18)F]fluoropenciclovir (FPCV) in C6 rat glioma cells expressing HSV1-sr39tk is increased by a factor of approximately 2.0 when compared with C6 cells expressing wild-type HSV1-tk. The increased imaging sensitivity of HSV1-sr39tk when FPCV is used is also demonstrated in vivo both with tumor cells stably transfected with either HSV1-tk or HSV1-sr39tk, and after hepatic delivery of HSV1-tk or HSV1-sr39tk by using adenoviral vectors. The use of HSV1-sr39tk as a PET reporter gene and FPCV as a PET reporter probe results in significantly enhanced sensitivity for imaging reporter gene expression in vivo.

Synthesis of 8-[(18)F]fluoroguanine derivatives: in vivo probes for imaging gene expression with positron emission tomography

A new method for the preparation of 8-[(18)F]fluoroguanine derivatives based on a direct radiofluorination reaction has been developed. The radiofluorination of ganciclovir (1a) with [(18)F]F(2) was carried out in absolute ethanol in the presence of tetraethylammonium hydroxide at room temperature to give 8-[(18)F]fluoroganciclovir (3a) in an approximately 1% radiochemical yield. Similarly, 8-[(18)F]fluoropenciclovir (3b), 8-[(18)F]fluoroacyclovir (3c), and 8-[(18)F]fluoroguanosine (3d) were synthesized from penciclovir (1b), acyclovir (1c), and guanosine (1d), respectively, using [(18)F]F(2). The structural analyses of the final products (3a, 3b, 3c, and 3d) were carried out after (18)F decay by (1)H, (13)C, and (19)F nuclear magnetic resonance and high resolution mass spectroscopy.

2Beta-carbomethoxy-3beta-(4- and 2-[18F]fluoromethylphenyl)tropanes: specific probes for in vivo quantification of central dopamine transporter sites

Dopamine reuptake transporter binding kinetics of 2beta-carbomethoxy-3beta-(4-[18F]fluoromethylphenyl)tropane (p-FWIN) and 2beta-carbomethoxy-3beta-(2-[18F]fluoromethylphenyl)tropane (o-FWIN) were determined in vervet monkeys using positron emission tomography (PET). Ligand localization was rapid and specific to the striatum with kinetic estimates comparable with those of 11C-labeled WIN 35,428 (CWIN). Binding was more specific with p-FWIN than with CWIN or o-FWIN. The relatively longer half-life of the 18F radiolabel enabled longer acquisition times with p-FWIN, resulting in less variability in the kinetic estimates.

Synthesis of 3beta-(4-[18F]fluoromethylphenyl)- and 3beta-(2-[18F] fluoromethylphenyl)tropane-2beta-carboxylic acid methyl esters: new ligands for mapping brain dopamine transporter with positron emission tomography

The synthesis of two new dopamine transporter ligands, 3beta-(4-fluoromethylphenyl)tropane-2beta-carboxylic acid methyl ester and 3beta-(2-fluoromethylphenyl)tropane-2beta-carboxylic acid methyl ester, and their spectral characterization are described. The precursors for these ligands were prepared by TiCl4 catalyzed chloromethylation of 3beta-phenyltropane-2beta-carboxylic acid methyl ester followed by separation of the isomeric product mixture of 2- and 4-chloromethylphenyltropane derivatives. Reaction of the chloromethyl analogs with no-carrier-added [18F]fluoride ion followed by high performance liquid chromatography purification provided the corresponding [18F]fluoromethyltropanes, in good radiochemical yields, useful for imaging the brain dopamine transporter system in vivo with positron emission tomography.

Imaging adenoviral-directed reporter gene expression in living animals with positron emission tomography

We are developing quantitative assays to repeatedly and noninvasively image expression of reporter genes in living animals, using positron emission tomography (PET). We synthesized positron-emitting 8-[18F]fluoroganciclovir (FGCV) and demonstrated that this compound is a substrate for the herpes simplex virus 1 thymidine kinase enzyme (HSV1-TK). Using positron-emitting FGCV as a PET reporter probe, we imaged adenovirus-directed hepatic expression of the HSV1-tk reporter gene in living mice. There is a significant positive correlation between the percent injected dose of FGCV retained per gram of liver and the levels of hepatic HSV1-tk reporter gene expression (r2 > 0.80). Over a similar range of HSV1-tk expression in vivo, the percent injected dose retained per gram of liver was 0-23% for ganciclovir and 0-3% for FGCV. Repeated, noninvasive, and quantitative imaging of PET reporter gene expression should be a valuable tool for studies of human gene therapy, of organ/cell transplantation, and of both environmental and behavioral modulation of gene expression in transgenic mice.

Imaging of adenoviral-directed herpes simplex virus type 1 thymidine kinase reporter gene expression in mice with radiolabeled ganciclovir

We are developing procedures to repeatedly and noninvasively image the expression of transplanted reporter genes in living animals and in patients, using PET. We have investigated the use of the Herpes Simplex Virus type 1 thymidine kinase gene (HSV1-tk) as a reporter gene and [8-14C]-ganciclovir as a reporter probe. HSV1-tk, when expressed, leads to phosphorylation of [8-14C]-ganciclovir. As a result, specific accumulation of phosphorylated [8-14C]-ganciclovir should occur almost exclusively in tissues expressing the HSV1-tk gene.

METHODS

An adenoviral vector was constructed carrying the HSV1-tk gene along with a control vector. C6 rat glioma cells were infected with either viral vector and uptake of [8-3H]-ganciclovir was determined. In addition, 12 mice were injected with varying levels of either viral vector. Adenovirus administration in mice leads primarily to liver infection. Forty-eight hours later the mice were injected with [8-14C]-ganciclovir, and 1 hr later the mice were sacrificed and biodistribution studies performed. Digital whole-body autoradiography also was performed on separate animals. HSV1-tk expression was assayed, using both normalized HSV1-tk mRNA levels and relative HSV1-TK enzyme levels, in both the cell culture and murine studies.

RESULTS

Cell culture, murine tissue biodistribution and murine in vivo digital whole-body autoradiography all demonstrate the feasibility of HSV1-tk as a reporter gene and [8-14C]-ganciclovir as an imaging reporter probe. A good correlation (r2 = 0.86) between the [8-14C]-ganciclovir percent injected dose per gram tissue from HSV1-tk positive tissues and HSV1-TK enzyme levels in vivo was found. An initial study in mice with [8-18F]-fluoroganciclovir and microPET imaging supports further investigation of [8-18F]-fluoroganciclovir as a PET reporter probe for imaging HSV1-tk gene expression.

CONCLUSION

These results demonstrate the feasibility of using [8-14C]-ganciclovir as a reporter probe for the HSV1-tk reporter gene, using an in vivo adenoviral mediated gene delivery system in a murine model. The results form the foundation for further investigation of [8-18F]-fluoroganciclovir for noninvasive and repeated imaging of gene expression with PET.

Radiofluorinated L-m-tyrosines: new in-vivo probes for central dopamine biochemistry

In this work, we introduce 6-[18F]fluoro-L-m-tyrosine (6-FMT) and compare its in-vivo kinetic and bio-chemical behaviors in monkeys and rodents with those of 4-FMT and 6-[18F]fluoro-L-3, 4-dihydroxyphenylalanine (DOPA) (FDOPA). These radiofluorinated m-tyrosine presynaptic dopaminergic probes, resistant to peripheral 3-O-methylation, offer a nonpharmacological alternative to the use of catechol-O-methyltransferase inhibitors. Like FDOPA, 4-FMT and 6-FMT are analogs that essentially follow the L-DOPA pathway of central metabolism. After i.v. administration in nonhuman primates and rodents, these new radiofluorinated m-tyrosine analogs accumulate selectively in striatal structures and allow for the detection of additional innervation sites (e.g., brain stem) rich in aromatic amino acid decarboxylase. Bio-chemical analyses in rodents and monkeys revealed the specificity of their central and peripheral metabolism. Molecular and enzymatic mechanisms involved in their retention in central brain structures are consistent with involvement of dopaminergic neurons. The high signal-to-noise ratios observed make these radiofluorinated m-tyrosine analogs outstanding candidates for probing the integrity of central dopaminergic mechanisms in humans.

Synthesis of 6-[18F] and 4-[18F]fluoro-L-m-tyrosines via regioselective radiofluorodestannylation

The regioselective radiofluorodestannylation of 6-trimethylstannyl-L-m-tyrosine derivative 6 with [18F]F2 and [18F]acetyl hypofluorite afforded, after acid hydrolysis, 6-[18F]fluoro-L-m-tyrosine (8a) in radiochemical yields of 23 and 17%, respectively. Similarly, 4-[18F]fluoro-L-m-tyrosine (13a) was synthesized in 11% radiochemical yield from the corresponding 4-trimethylstannyl-L-m-tyrosine derivative 11 using [18F]F2. The structural analyses of precursors (6,11), intermediates, and the final products (after 18F decay), were carried out by 1H, 13C, 19F, 119Sn-NMR and high resolution mass spectroscopy.

Regioselective radiofluorodestannylation with [18F]F2 and [18F]CH3COOF: a high yield synthesis of 6-[18F]Fluoro-L-dopa

A protected 6-trimethylstannyl dopa derivative 6 has been synthesized for the first time as a precursor for the preparation of 6-[18F]fluoro-L-dopa. The tin derivative 6 readily reacted with electrophilic radiofluorinating agents such as [18F]F2 and [18F]AcOF. The [18F]fluoro intermediate 7 was easily hydrolyzed with HBr and the product 6-[18F]fluoro-L-dopa was isolated after HPLC purification in a maximum radiochemical yield of 25%, ready for human use. The various intermediates, the stannyl precursor 6 and the final product (after 18F decay) were all fully characterized by 1H, 13C, 19F and 119Sn NMR as well as high resolution mass spectroscopy.