Next-generation sequencing in dermatology

Over the past decade, Next-Generation Sequencing (NGS) has advanced our understanding, diagnosis, and management of several areas within dermatology. NGS has emerged as a powerful tool for diagnosing genetic diseases of the skin, improving upon traditional PCR-based techniques limited by significant genetic heterogeneity associated with these disorders. Epidermolysis bullosa and ichthyosis are two of the most extensively studied genetic diseases of the skin, with a well-characterized spectrum of genetic changes occurring in these conditions. NGS has also played a critical role in expanding the mutational landscape of cutaneous squamous cell carcinoma, enhancing our understanding of its molecular pathogenesis. Similarly, genetic testing has greatly benefited melanoma diagnosis and treatment, primarily due to the high prevalence of BRAF hot spot mutations and other well-characterized genetic alterations. Additionally, NGS provides a valuable tool for measuring tumor mutational burden, which can aid in management of melanoma. Lastly, NGS demonstrates promise in improving the sensitivity of diagnosing cutaneous T-cell lymphoma. This article provides a comprehensive summary of NGS applications in the diagnosis and management of genodermatoses, cutaneous squamous cell carcinoma, melanoma, and cutaneous T-cell lymphoma, highlighting the impact of NGS on the field of dermatology.

Plasma Thrombospondin as an Indicator of Intravascular Platelet Activation in Patients with Vasculitis

The use of plasma thrombospondin (TSP) concentration was investigated as an indicator of intravascular platelet activation. Patients (n = 20) with diseases that have known vasculitis were included in the study. The range and the mean of plasma TSP concentrations of patients with vasculitis were 117 ng/ml to 6500 ng/ml and 791±1412 ng/ml (mean ± SD); the range and the mean of plasma TSP concentrations of control individuals (n = 33) were 13 ng/ml to 137 ng/ml and 59±29 ng/ml. When plasma TSP concentrations were correlated with plasma concentrations of another platelet activation marker, β-thromboglobulin (P-TG), it was found that the TSP concentration inei eased exponentially as the plasma β-TG level rose. A positive correlation between plasma levels of plasma TSP and serum fibrin degradation products was also observed. The results suggest that platelets are the primary source of plasma TSP in patients with various vasculitis and that plasma TSP can be a better indicator than β-TG to assess intravascular platelet activation due to its longer circulation half life.

Host-determined T cell fine specificity for self-H-2 in radiation bone-marrow chimeras of standard C57BL/6 (H-2(b)) mutantHz1 (H-2 (ba)), and F (1) mice

Reciprocal radiation bone-marrow chimeras were produced between the standard C57BL/6 (=B6) and the mutant B6.C-H-2 ( ba ) (=Hz1) strain. When infected with vaccinia virus, these chimeras, as well as an (Hz1 × B6)=→ Hz1 chimera, produced cytotoxic cells that killed vaccinia-infected H-2K(k)H-2D(b) target cells but failed to kill virus-infected H-2K(b)H-2D(d) cells. Virus-infected (Hz1 × B6)F(1) → B6 chimeras, however, killed both types of target. These experiments demonstrate strict T-cell specificity capable of differentiating between two molecules that apparently differ by a single amino acid substitution.

Retiform purpura in a patient with a history of cocaine use

There have been rare published cases of retiform purpura related to cocaine use. Levamisole, a common adulterant, has been implicated as the etiologic agent. We describe a female patient, aged 48 years, with cocaine-related retiform purpura involving her face, abdomen, and legs and alert physicians to the dangers of levamisole-contaminated cocaine.

Mycoplasma testudineum sp. nov., from a desert tortoise (Gopherus agassizii) with upper respiratory tract disease

Mycoplasma testudineum sp. nov., first cultured from the upper respiratory tract of a clinically ill tortoise (Gopherus agassizii) in the Mohave Desert, was distinguished from previously described mollicutes serologically and by 16S rRNA gene sequence comparisons. It lacks a cell wall; ferments glucose, mannose, lactose and sucrose; does not produce ‘film and spots’; does not hydrolyse arginine, aesculin or urea; is sensitive to digitonin; and lacks phosphatase activity. The organism causes chronic rhinitis and conjunctivitis of tortoises. The type strain of M. testudineum is BH29T (=ATCC 700618T=MCCM 03231T).

Experimental transmission of a herpesvirus in Greek tortoises (Testudo graeca)

An experimental transmission study aimed at fulfilling Koch's postulates for a herpesvirus-associated stomatitis-rhinitis in Mediterranean tortoises is presented. Clinical, pathologic, serologic, and molecular studies were performed linking tortoise herpesvirus with the pathogenesis of stomatitis-rhinitis. Four adult Greek tortoises received either intranasally or intramuscularly two tortoise herpesvirus isolates by primary experimental infection and secondary challenge 11 months later. After the primary experimental infection and the secondary challenge, clinical signs of illness developed, which included conjunctivitis, diphtheritic oral plaques, and oral discharge. At 4 weeks after the secondary challenge, all tortoises were humanely euthanatized and evaluated. Although neutralizing antibodies developed after the primary experimental infection, they apparently did not prevent the later development of recurrent clinical signs. Polymerase chain reaction (PCR) and reverse transcription-PCR analyses allowed sensitive characterization of the systemic distribution of the herpesvirus DNA sequences and their presence in the cranial nerves and brains of the infected tortoises. Despite the failure to recover the herpesviruses used in the transmission study, the findings support the premise that tortoise herpes-virus is a primary pathogen of Greek tortoises.

Application of immunoperoxidase-based techniques to detect herpesvirus infection in tortoises

Indirect (IIP) and direct (DIP) immunoperoxidase assays were developed for the serological and histological diagnoses of herpesvirus infection in tortoises, respectively. A mouse monoclonal antibody (MAb HL1546), specific for the heavy chain of tortoise IgY, was used as the secondary antibody in the IIP assay. Rabbit polyclonal antisera raised against 2 sucrose gradient-purified tortoise herpesvirus isolates (HV4295/7R/95 and HV1976) were used as primary antibodies for the detection of herpesvirus antigen either in infected cell cultures or in formalin-fixed, paraffin-embedded tissues. The IIP and DIP assays could detect either the presence of anti-herpesvirus antibody in the plasma of exposed tortoises or the presence of herpesvirus antigen in infected tissues, respectively. Although the IIP test complements the enzyme-linked immunosorbent assay and the serum neutralization test already available for measuring herpesvirus-specific antibody in tortoises, the DIP test is useful for the histological diagnosis of herpesvirus infection in tortoises.

Survey of Florida green turtles for exposure to a disease-associated herpesvirus

A recently developed enzyme-linked immunosorbent assay (ELISA) was used to assess exposure of Florida wild green turtles Chelonia mydas to LETV, the herpesvirus associated with lung-eye-trachea disease (LETD). Plasma samples from 329 wild juvenile green turtles netted in the Indian River lagoon, along the Sebastian reef, or in the Trident basin (Indian River and Brevard Counties, Florida) were tested by ELISA for the presence of antibodies to LETV. Plasma samples from 180 wild juvenile green turtles were tested from these study sites to compare the prevalence of anti-LETV antibodies. While some plasma samples from each site contained anti-LETV antibodies (confirmed by Western blot analysis), plasma samples collected from the Indian River lagoon had statistically higher optical density values measured in the ELISA. No statistical differences were observed when these same plasma samples were analyzed for changes in the level of anti-LETV antibodies over 3 years (1997, 1998, and 1999). To explore the relationship between anti-LETV antibodies and fibropapillomatosis (FP), plasma from 133 green turtles scored for fibropapilloma tumor severity were tested by ELISA. There was no correlation between tumor severity and the presence of antibodies against LETV. Additional plasma samples collected from 16 tagged green turtles captured and sampled more than once (recaptures) were also tested to monitor antibody levels to LETV relative to the FP status of individual turtles over time. Again there was no clear relationship between FP tumor status and the presence of antibodies to LETV. Finally, ELISA tests on plasma from 13 nesting female turtles (9 green and 4 loggerhead) revealed high levels of anti-LETV antibodies in 11 individuals, including 2 loggerhead turtles. These results provide strong evidence that wild Florida green turtle populations at these 3 study sites are exposed to LETV or a closely related virus and that loggerhead turtles may be exposed as well. Based on a cutoff optical density value of 0.310, 71 out of the 329 wild Florida green turtles tested were seropositive for LETV antibodies (seroprevalence = 21.6%). In addition, no relationship between FP tumor severity or status and the presence of anti-LETV antibodies was found, further supporting the hypothesis that LETV and the FP-associated herpesvirus (FPHV) are separate infections of marine turtles.

Surface step effects on nanoindentation

Atomistic simulation is used to examine nanoindentation of a Au(111) crystal both near and far from a surface step. While the load needed to nucleate dislocations decreases significantly when indenting close to the step, the extent of the step's influence is not as great as seen experimentally. This behavior is explained by measuring the contact area from the simulation data. A new metric, the slip vector, shows material slip coinciding with the <112> directions of a lowest unstable stacking fault barrier. The slip vector is used to calculate an atomic critical resolved shear stress, which is shown to be a good dislocation nucleation criterion.

Detection of antibodies to a disease-associated herpesvirus of the green turtle, Chelonia mydas

Lung-eye-trachea disease-associated herpesvirus (LETV) is linked with morbidity and mortality in mariculture-reared green turtles, but its prevalence among and impact on wild marine turtle populations is unknown. An enzyme-linked immunosorbent assay (ELISA) was developed for detection of anti-LETV antibodies and could distinguish LETV-exposed green turtles from those with antibodies to fibropapillomatosis-associated herpesvirus (FPHV). Plasma from two captive-reared green turtles immunized with inactivated LETV served as positive controls. Plasma from 42 healthy captive-reared green turtles and plasma from 30 captive-reared green turtles with experimentally induced fibropapillomatosis (FP) and anti-FPHV antibodies had low ELISA values on LETV antigen. A survey of 19 wild green turtles with and 27 without FP (with and without anti-FPHV antibodies, respectively) identified individuals with antibodies to LETV regardless of their FP status. The seroprevalence of LETV infection was 13%. The presence of antibodies to LETV in plasma samples was confirmed by Western blot and immunohistochemical analyses. These results are the first to suggest that wild Florida green turtles are exposed to LETV or to an antigenically closely related herpesvirus(es) other than FPHV and that FPHV and LETV infections are most likely independent events. This is the first ELISA developed to detect antibodies for a specific herpesvirus infection of marine turtles. The specificity of this ELISA for LETV (ability to distinguish LETV from FPHV) makes it valuable for detecting exposure to this specific herpesvirus and enhances our ability to conduct seroepidemiological studies of these disease-associated agents in marine turtles.

Enzyme-linked immunosorbent assay for detecting herpesvirus exposure in Mediterranean tortoises (spur-thighed tortoise [Testudo graeca] and Hermann's tortoise [Testudo hermanni])

An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of antibodies to a herpesvirus associated with an upper respiratory tract disease in Mediterranean tortoises [spur-thighed tortoise (Testudo graeca) and Hermann's tortoise (Testudo hermanni)]. This serodiagnostic test was validated through a hyperimmunization study. The mean of the A(405) readings of the plasma samples collected at time zero of the hyperimmunization study plus three times the standard deviation was used as the cutoff for seropositivity in tortoises. ELISA results were compared to serum neutralization (SN) values for the same samples by using the McNemar test. The results obtained by SN and ELISA were not significantly different (P > 0.05). This new ELISA could be used as an important diagnostic tool for screening wild populations and private and zoo collections of Mediterranean tortoises.

Differential gene expression associated with tumorigenicity of cultured green turtle fibropapilloma-derived fibroblasts

Fibroblast cell lines derived from normal skin and experimentally induced fibropapillomas of green turtles (Chelonia mydas), were propagated in vitro and tested for tumorigenicity in immunodeficient mice. Differential display RT-PCR was used to identify differences in messenger RNA expression between normal and tumorigenic fibropapillomatosis (FP)-derived fibroblasts from the same individual. Four unique products that were apparently overexpresed in FP and three that were apparently underexpressed were cloned and sequenced. Differential expression was confirmed for three products by Northern blotting. Two overexpressed products showed extensive sequence matches to the known mammalian cellular genes, beta-hexosaminidase and chain termination factor. The product that was underexpressed in FP showed homology with mammalian thrombospondin, a known tumor-suppressor gene and an inhibitor of angiogenesis. All of the partial gene sequences identified are novel and will require full length cDNA sequencing to further analyze their identities. These results, however, provide the foundation for further investigation to determine the role of each of these gene products in FP pathogenesis and cellular transformation. The potential for some of these products to serve as biomarkers for FP is discussed.

Mycoplasma agassizii sp. nov., isolated from the upper respiratory tract of the desert tortoise (Gopherus agassizii) and the gopher tortoise (Gopherus polyphemus)

Biochemical, serological and molecular genetic studies were performed on seven mycoplasma isolates that were recovered from the upper respiratory tract of clinically ill desert tortoises. The isolates were serologically related to each other but serologically distinct from previously described species. Unique mycoplasma species-specific 16S rRNA nucleotide sequences were found in the proposed type strain. The name Mycoplasma agassizii is proposed for these isolates. The type strain is PS6T (= ATCC 700616T) which caused upper respiratory tract disease (URTD) in experimentally infected tortoises.

Persistent infectivity of a disease-associated herpesvirus in green turtles after exposure to seawater

Herpesviruses are associated with several diseases of marine turtles including lung-eye-trachea disease (LETD) and gray patch disease (GPD) of green turtles (Chelonia mydas) and fibropapillomatosis (FP) of green, loggerhead (Caretta caretta), and olive ridley turtles (Lepidochelys olivacea). The stability of chelonian herpesviruses in the marine environment, which may influence transmission, has not been previously studied. In these experiments, LETD-associated herpesvirus (LETV) was used as a model chelonian herpesvirus to test viral infectivity after exposure to seawater. The LETV virus preparations grown in terrapene heart (TH-1) cells were dialyzed for 24 to 120 hr against aerated artificial or natural seawater or Hank's balanced salt solution (HBBS). Fresh TH-1 cells were inoculated with dialyzed LETV, and on day 10 post-infection cells were scored for cytopathic effect. Virus samples dialyzed up to 120 hr were positive for the herpesvirus DNA polymerase gene by polymerase chain reaction. Electron microscopy revealed intact LETV nucleocapsids after exposure of LETV to artificial seawater or HBSS for 24 hr at 23 C. LETV preparations remained infectious as long as 120 hr in natural and artificial seawater at 23 C. Similar results were obtained with a second culturable chelonian herpesvirus, HV2245. LETV infectivity could not be detected after 48 hr exposure to artificial seawater at 30 C. Since LETV and HV2245 remain infectious for extended periods of time in the marine environment, it is possible that FP-associated and GPD-associated herpesviruses also may be stable. These findings are significant both for researchers studying the epidemiological association of herpesviruses with diseases of marine turtles and for individuals who handle turtles in marine turtle conservation efforts.

Atopic dermatitis in infants and children. An update

The goal in treating patients with atopic dermatitis is to maintain adequate hydration while decreasing pruritus and inflammation. It is also important to recognize factors that are responsible for flares. Although the etiology of atopic dermatitis remains unknown, therapies are being developed targeting immunologic defects in this disease.

Pathology of upper respiratory tract disease of gopher tortoises in Florida

Between August 1993 and September 1995, 24 gopher tortoises (Gopherus polyphemus) were received for pathological evaluations from various locations in Florida (USA). All tortoises were examined for clinical signs of upper respiratory tract disease (URTD) including nasal and ocular discharge, palpebral edema, and conjunctivitis. Of the 24 tortoises, 10 had current or previously observed clinical signs of URTD and 14 did not. A blood sample was drawn for detection of anti-mycoplasma antibodies by ELISA, and nasal lavage samples were collected for culture and detection of Mycoplasma agassizii gene sequences by polymerase chain reaction (PCR). Of the 14 clinically healthy tortoises, eight were sero-, culture- and PCR-negative, and six were seropositive for antibodies against M. agassizii. Of those six, five were culture- and/or PCR-positive for M. agassizii, and one was culture- and PCR-negative. Of the 10 ill tortoises, nine were seropositive by the ELISA and one was in the suspect range. Nine of the ill tortoises, including the suspect tortoise, were culture- and/or PCR-positive for M. agassizii, and one was culture- and PCR-negative. For histologic evaluation and discussion, the eight sero-, culture-, and PCR-negative tortoises were designated URTD-negative, and the other 16 were classified as URTD-positive. Histologic evaluation of the upper respiratory tract (URT) indicated the presence of mild to severe inflammatory, hyperplastic, or dysplastic changes in 14 URTD-positive tortoises. Seven of eight URTD-negative tortoises had normal appearing nasal cavities; one had mild inflammatory changes. Transmission electron microscopy revealed an organism consistent with Mycoplasma spp. on the nasal mucosal surface of tortoises with clinical signs and lesions of URTD. Additionally, gram-negative bacteria were isolated more frequently from the nasal cavities of URTD-positive tortoises than URTD-negative tortoises. Because clinical signs of URTD were never observed in six of the URTD-positive tortoises, we also conclude that subclinical URTD can occur in gopher tortoises.

Drug-induced linear IgA bullous dermatosis after vancomycin discontinuance in a patient with renal insufficiency

Linear IgA bullous dermatosis (LABD) is an autoimmune, subepidermal, vesiculobullous disease that has been commonly associated with the use of vancomycin hydrochloride. Lesions typically appear during vancomycin therapy, 24 hours to 15 days after the first dose. A 65-year-old white man with renal insufficiency developed pruritic, tense bullae on the right chest, right medial arm, right flank, abdomen, and right upper thigh 14 days after his last dose of vancomycin. Histopathologic examination and immunofluorescence studies were diagnostic of LABD. Vancomycin-related LABD may appear as long as 2 weeks after the drug is discontinued.

An evidence-based review of the efficacy of antihistamines in relieving pruritus in atopic dermatitis

OBJECTIVE

To critically review the body of clinical trials that refute or support the efficacy of antihistamines in relieving pruritus in patients with atopic dermatitis.

DESIGN

Review of MEDLINE from 1966 through March 1999, the Cochrane Database of Systematic Reviews, and Best Evidence to identify therapeutic trials of antihistamines in patients with atopic dermatitis.

MAIN OUTCOME MEASURES

All randomized controlled trials or clinical trials of antihistamines used in the treatment of atopic dermatitis. We found 16 studies throughout the literature.

RESULTS

Large, randomized, double-blind, placebo-controlled clinical trials with definitive conclusions (grade A trials) have not been performed. Two grade B trials (small, rigorous, randomized trials with uncertain results due to moderate to high alpha or beta error) refuted the use of antihistamines in relieving pruritus. One grade B trial supported the efficacy of antihistamines in relieving pruritus. All remaining trials (grade C) lacked placebo controls or randomization, or contained fewer than 20 patients in each treatment group.

CONCLUSIONS

Although antihistamines are often used in the treatment of atopic dermatitis, little objective evidence exists to demonstrate relief of pruritus. The majority of trials are flawed in terms of the sample size or study design. Based on the literature alone, the efficacy of antihistamines remains to be adequately investigated. Anecdotally, sedating antihistamines have sometimes been useful by virtue of their soporific effect and bedtime use may be warranted. There is no evidence to support the effectiveness of expensive nonsedating agents.

Comparative pathology and pathogenesis of spontaneous and experimentally induced fibropapillomas of green turtles (Chelonia mydas)

Tumor biopsy samples from 25 Floridian and 15 Hawaiian green turtles (Chelonia mydas) with spontaneous green turtle fibropapillomatosis (GTFP) and from 27 captive-reared green turtles with experimentally induced GTFP were examined microscopically to differentiate the histologic features that result from GTFP pathogenesis and those that result from incidental factors that may vary according to geographic region. Common histologic features for spontaneous and experimentally induced tumors included fibroblast proliferation in the superficial dermis, epidermal acanthosis and hyperkeratosis, epidermal basal cell degeneration with dermal-epidermal cleft formation, spinous layer degeneration with intraepidermal vesicle and pustule formation, and ulceration. Visceral tumors, found in eight of 10 (80%) free-ranging turtles with cutaneous disease that were examined after death, had extensive interstitial fibrous proliferation. The presence of spirorchid trematode eggs and associated foreign body granulomas, common secondary findings within spontaneous tumors, varied by geographic location, and these findings were not observed in experimentally induced tumors. Eosinophilic intranuclear inclusions and intranuclear herpesvirus-associated antigen immunoreactivity were found in 18 of 38 (47%) experimentally induced cutaneous tumors and nine of 119 (7.5%) spontaneous tumors from Floridian but not Hawaiian turtles. The possible involvement of GTFP-associated herpesvirus in the pathogenesis of epidermal degenerative changes and GTFP pathogenesis is discussed.

Seroepidemiology of upper respiratory tract disease in the desert tortoise in the western Mojave Desert of California

Several factors have combined with an upper respiratory tract disease (URTD) to produce declines on some population numbers of desert tortoises (Gopherus agassizii) in the western USA. This study was designed to determine the seroepidemiology of URTD in a population of wild adult tortoises at the Desert Tortoise Research Natural Area (DTNA) study site in Kern County (California, USA). Prior to initiation of the study, there was a dramatic decline in the number of individuals in this population. At each individual time point, samples were obtained from 12 to 20 tortoises with radiotransmitters during winter, spring, summer, and fall from 1992 through 1995. During the course of the study, 35 animals were sampled at one or more times. Only 10 animals were available for consistent monitoring throughout the 4 yr period. Specific antibody (Ab) levels to Mycoplasma agassizii were determined for individual tortoises by an enzyme-linked immunosorbent assay (ELISA) test. Specific Ab levels were not influenced by the gender of the tortoise. Levels of Ab and distribution of ELISA+, ELISA- and suspect animals were not consistently affected by season within a single year or for a season among the study years. Significantly more tortoises presented with clinical signs in 1992 and 1995. The profile of ELISA+ animals with clinical signs shifted from 5% (1992) to 42% (1995). In 1992, 52% of tortoises lacked clinical signs and were ELISA-. In 1995, this category accounted for only 19% of tortoises. Based on the results of this study, we conclude that URTD was present in this population as evidenced by the presence of ELISA+ individual animals, and that the infectious agent is still present as evidenced by seroconversion of previously ELISA- animals during the course of the study. There is evidence to suggest that animals may remain ELISA+ without showing overt disease, a clinical pattern consistent with the chronic nature of most mycoplasmal infections. Further, there are trends suggesting that the clinical expression of disease may be cyclical. Continued monitoring of this population could provide valuable information concerning the spread of URTD in wild tortoise populations.

Association of herpesvirus with fibropapillomatosis of the green turtle Chelonia mydas and the loggerhead turtle Caretta caretta in Florida

Sea turtle fibropapillomatosis (FP) is a disease marked by proliferation of benign but debilitating cutaneous fibropapillomas and occasional visceral fibromas. Transmission experiments have implicated a chloroform-sensitive transforming agent present in filtered cell-free tumor homogenates in the etiology of FP. In this study, consensus primer PCR methodology was used to test the association of a chelonian herpesvirus with fibropapillomatosis. Fibropapilloma and skin samples were obtained from 17 green and 2 loggerhead turtles affected with FP stranded along the Florida coastline. Ninety-three cutaneous and visceral tumors from the 19 turtles, and 33 skin samples from 16 of the turtles, were tested. All turtles affected with FP had herpesvirus associated with their tumors as detected by PCR. Ninety-six percent (89/93) of the tumors, but only 9% (3/33) of the skin samples, from affected turtles contained detectable herpesvirus. The skin samples that contained herpesvirus were all within 2 cm of a fibropapilloma. Also, 1 of 11 scar tissue samples from sites where fibropapillomas had been removed 2 to 51 wk earlier from 5 green turtles contained detectable herpesvirus. None of 18 normal skin samples from 2 green and 2 loggerhead turtles stranded without FP contained herpesvirus. The data indicated that herpesvirus was detectable only within or close to tumors. To determine if the same virus infected both turtle species, partial nucleotide sequences of the herpesvirus DNA polymerase gene were determined from 6 loggerhead and 2 green turtle samples. The sequences predicted that herpesvirus of loggerhead turtles differed from those of green turtles by only 1 of 60 amino acids in the sequence examined, indicating that a chelonian herpesvirus exhibiting minor intratypic variation was the only herpesvirus present in tumors of both green and loggerhead turtles. The FP-associated herpesvirus resisted cultivation on chelonian cell lines which support the replication of other chelonian herpesviruses. These results lead to the conclusion that a chelonian herpesvirus is regularly associated with fibropapillomatosis and is not merely an incidental finding in affected turtles.

Upper respiratory tract disease in the gopher tortoise is caused by Mycoplasma agassizii

Upper respiratory tract disease (URTD) has been observed in a number of tortoise species, including the desert tortoise (Gopherus agassizii) and the gopher tortoise (Gopherus polyphemus). Clinical signs of URTD in gopher tortoises are similar to those in desert tortoises and include serous, mucoid, or purulent discharge from the nares, excessive tearing to purulent ocular discharge, conjunctivitis, and edema of the eyelids and ocular glands. The objectives of the present study were to determine if Mycoplasma agassizii was an etiologic agent of URTD in the gopher tortoise and to determine the clinical course of the experimental infection in a dose-response infection study. Tortoises were inoculated intranasally with 0.5 ml (0.25 ml/nostril) of either sterile SP4 broth (control group; n = 10) or 10(8) color-changing units (CCU) (total dose) of M. agassizii 723 (experimental infection group; n = 9). M. agassizii caused clinical signs compatible with those observed in tortoises with natural infections. Clinical signs of URTD were evident in seven of nine experimentally infected tortoises by 4 weeks postinfection (p.i.) and in eight of nine experimentally infected tortoises by 8 weeks p.i. In the dose-response experiments, tortoises were inoculated intranasally with a low (10(1) CCU; n = 6), medium (10(3) CCU; n = 6), or high (10(5) CCU; n = 5) dose of M. agassizii 723 or with sterile SP4 broth (n = 10). At all time points p.i. in both experiments, M. agassizii could be isolated from the nares of at least 50% of the tortoises. All of the experimentally infected tortoises seroconverted, and levels of antibody were statistically higher in infected animals than in control animals for all time points of >4 weeks p.i. (P < 0.0001). Control tortoises in both experiments did not show clinical signs, did not seroconvert, and did not have detectable M. agassizii by either culture or PCR at any point in the study. Histological lesions were compatible with those observed in tortoises with natural infections. The numbers of M. agassizii 723 did not influence the clinical expression of URTD or the antibody response, suggesting that the strain chosen for these studies was highly virulent. On the basis of the results of the transmission studies, we conclude that M. agassizii is an etiologic agent of URTD in the gopher tortoise.

Persistence of maternal antibodies against Mycoplasma agassizii in desert tortoise hatchlings

OBJECTIVE

To investigate Mycoplasma agassizii-specific maternal antibodies in desert tortoise (Gopherus agassizii) hatchlings.

SAMPLE POPULATION

Plasma from 43 captive-reared desert tortoise hatchlings.

PROCEDURE

ELISA for M agassizii-specific antibodies was performed. Four hatchlings from 4 clutches of 3 M agassizii-seropositive females with chronic upper respiratory tract disease (URTD) were tested on the day of hatching (set 1), and 20 hatchlings from 4 clutches of 4 M agassizii-seropositive females with URTD and 19 hatchlings from 4 M agassizii-seronegative healthy females were tested at 4, 8, 12, and 29 months old (set 2). Immunoblot analysis was performed to determine immunoglobulin classes in yolk and plasma of hatchlings. To determine infection status of hatchlings, yolk, egg shell membranes (set 1), and nasal lavage fluid (sets 1 and 2) were examined for M agassizii by use of polymerase chain reaction.

RESULTS

Yolk and hatchling plasma had significantly lower amounts of specific antibodies than did plasma from adult females. The IgG and IgM antibodies were transferred, but M agassizii-specific antibodies were of the IgG class. Hatchlings were not infected with mycoplasmas. Offspring of sick females had significantly higher specific antibody titers than did offspring of healthy females. Titers were still significantly different in 1-year-old hatchlings.

CONCLUSIONS

Desert tortoise females transfer specific IgG and IgM antibodies to their offspring that are still detectable after 1 year.

CLINICAL RELEVANCE

Infection with M agassizii may be misdiagnosed in hatchlings with persistent maternal antibodies. Passively acquired antibodies may have a role in pathogenesis of mycoplasma-induced respiratory tract disease and other diseases.

Acute infection with Trichophyton rubrum associated with flares of atopic dermatitis

Trichophyton rubrum has been implicated as a potential trigger in flares of atopic dermatitis. We describe a patient with atopic dermatitis who presented with a history of multiple flares and concurrent acute tinea pedis and onychomycosis. Symptoms of atopic dermatitis and culture-positive acute infection with T. rubrum resolved during each flare using systemic antifungals. Flares of atopic dermatitis may be triggered by acute T. rubrum infections. Antifungal therapy should be considered in these patients.

Serological association between spirorchidiasis, herpesvirus infection, and fibropapillomatosis in green turtles from Florida

Serodiagnostic tests for detecting green turtle (Chelonia mydas) antibody responses were developed to test the strength of association between exposure to spirorchid trematode antigens or herpesvirus antigens and having green turtle fibropapillomatosis (GTFP). Plasma samples from 46 captive-reared green turtles, including paired pre- and 1-yr post-inoculation samples from 12 turtles with experimentally induced GTFP, were found by enzyme-linked immunosorbent assay (ELISA) to be negative for antibodies to adult spirorchid (Learedius learedi) antigens. In contrast, all 12 turtles that developed experimentally induced GTFP converted within 1 yr from having negative to positive antibody reactivity to GTFP-associated herpesvirus antigens, whereas the three controls and four turtles that failed to develop tumors remained negative. Plasma samples from 104 free-ranging green turtles from two Florida (USA) coastal feeding grounds with different GTFP prevalences were tested by ELISA for antibodies to L. learedi adult antigens; and there was no statistically significiant association between antibody prevalence and sampling site. When a low optical density cutoff value (0.15) was used to interpret ELISA results, 98% of the turtles from each site were spirorchid antibody-positive and there was no association between antibody reactivity to spirorchids and GTFP status. When a higher negative cutoff value was used, however, a statistically significant association between antibody reactivity to spirorchids and GTFP-free status was found. These results suggest that spirorchids do not have a role in GTFP pathogenesis. All 20 of the tumor-bearing lagoon turtles had antibodies to herpesvirus antigens whereas only two (10%) of the tumor-free reef turtles had detectable anti-herpesvirus reactivity. The strong association between antibody reactivity to herpesvirus antigens and GTFP status in both captive-reared and free-ranging turtles is consistent with the hypothesis that the transmissible agent that causes GTFP is a herpesvirus.

Tumorigenicity of green turtle fibropapilloma-derived fibroblast lines in immunodeficient mice

Fibroblast lines derived from normal skin and spontaneous or experimentally induced fibropapillomas of green turtles (Chelonia mydas) were established and propagated in medium composed of a combination of Dulbecco's minimal essential with F12 medium plus 10% fetal bovine serum at 30 degrees C. Fibropapilloma-derived fibroblasts were indistinguishable from normal skin fibroblasts in vitro. Tumor lines did not exhibit loss of contact inhibition, anchorage independence, or reduced serum requirements. Inoculation of primary and early-passage tumor cells into the medial margin of the pinna of C57BL/6J-nu/nu, C.B17-scid/scid, or NOD-scid/scid mice, however, resulted in fibroma formation, whereas inoculation of normal skin fibroblasts did not. Tumor-derived cells inoculated into the flanks of mice did not form tumors. The turtle origin of fibroblasts in tumors from mouse ears was confirmed by immunohistochemical and karyotype analysis. Fibroblast lines that were established from mouse ear fibromas had the normal karyotype (modal 2N = 55) of C. mydas. The cooler anatomic sites (ears) of immunodeficient mice are useful for confirming the tumorigenic (transformed) phenotype of green turtle fibropapillomatosis-derived fibroblasts. This mouse ear tumorigenicity test should facilitate studies of mechanisms of cellular transformation in green turtle fibropapillomatosis and other neoplastic diseases of poikilothermic vertebrates.

Relationship between clinical signs of upper respiratory tract disease and antibodies to Mycoplasma agassizii in desert tortoises from Nevada

Plasma samples collected in 1990 from free-ranging desert tortoises (Gopherus agassizii) with and without clinical signs of upper respiratory tract disease (URTD) from Las Vegas Valley, Clark County, Nevada (USA), were tested by enzyme-linked immunosorbent assay (ELISA) for antibodies to Mycoplasma agassizii, a causative agent of URTD. The relationship between clinical signs and ELISA test results was evaluated. Of the 144 tortoises tested, 45 (31%) had clinical signs while 72 (50%) were seropositive. Presence of clinical signs of URTD was positively related to positive ELISA results (P < 0.0001) regardless of sex or age of the animal. Eighty-four percent of animals with clinical signs tested seropositive. Mucous nasal discharge, the most severe and obvious of the clinical signs, was highly predictive for exposure to M. agassizii based on the ELISA. Ninety-three percent of tortoises with mucous nasal discharge tested seropositive. Serologic testing for M. agassizii antibodies supported clinical signs as useful indicators of URTD, but it also detected potential subclinical infection in 34 (34%) of 99 animals without clinical signs.

Development of monoclonal antibodies for measurement of immunoglobulin G antibody responses in blue and gold macaws (Ara ararauna)

OBJECTIVES

To produce monoclonal antibodies (MAB) with specificity for the heavy chain of macaw IgG; to incorporate these MAB into an ELISA to measure IgG responses of macaws inoculated with bovine serum albumin (BSA); and to evaluate the antigenicity of BSA in Blue and Gold Macaws.

ANIMALS

Four 1-year-old Blue and Gold Macaws, 2 males and 2 females.

PROCEDURE

1 male and 1 female 1 were randomly assigned to each of 2 study groups. Group-1 birds were inoculated with 200 micrograms of BSA on days 0, 14, 28, and 42. Group-2 birds were inoculated with 200 micrograms of BSA on days 0 and 28. Blood was collected weekly for measurement of anti-BSA titer. Hybridomas were prepared from mice immunized with Scarlet Macaw (Ara macao) IgG purified by salt precipitation and gel chromatography. Specificity for IgG of Scarlet Macaw and other macaw species was confirmed by ELISA and western blot analysis. Hybridoma HL544 was cloned and the antibody purified. Following biotinylation, MAB HL544 was incorporated into an ELISA that measured IgG responses of macaws inoculated with BSA.

RESULTS

Adult Blue and Gold Macaws developed strong primary and secondary anti-BSA antibody titers 14 days after inoculation with 200 micrograms of BSA. An inoculation interval of 28 days resulted in stronger secondary responses than an interval of only 14 days.

CONCLUSIONS

MAB specific for macaw immunoglobulins can be used in ELISA to evaluate the humoral immune responses of macaws. 1-year-old Blue and Gold Macaws developed strong anti-BSA titer when inoculated with 200 micrograms of BSA. An inoculation interval of 28 days resulted in stronger secondary responses than did an interval of only 14 days.

CLINICAL RELEVANCE

These MAB, the first reported to have specificity for a psittacine antibody class, will be useful in the evaluation of psittacine antibody responses and in the development of psittacine diagnostic assays.

Maternal immunoglobulin G antibody transfer and development of immunoglobulin G antibody responses in blue and gold macaw (Ara ararauna) chicks

OBJECTIVE

To document the maternal transfer of IgG antibodies from Blue and Gold Macaw hens to chicks via the egg; to measure serum IgG half-life in macaw chicks; and to measure the ability of 2- to 10-week-old macaw chicks to generate primary and secondary IgG responses.

PROCEDURE

4 adult Blue and Gold Macaw hens were inoculated with 200 micrograms of bovine serum albumin (BSA) every 21 days throughout the breeding season. Eggs laid by these hens were incubator hatched to eliminate the possibility of antibody transfer through crop secretions during feeding. Anti-BSA titer was measured just prior to each inoculation in hens and in chicks from 14 to 42 days of age. 1 chick from each of 5 macaw clutches hatched to nonimmunized hens was assigned to 1 of 2 experimental groups. Group-1 chicks were inoculated with 200 micrograms of BSA at 2 and 6 weeks of age. Group-2 chicks were inoculated with 200 micrograms of BSA at 6 and 10 weeks of age. Anti-BSA titer was measured weekly for 8 weeks after primary inoculation. Blood samples were centrifuged, and serum was harvested and frozen at -85 C until analyzed. Anti-BSA IgG titer were measured by ELISA. In the maternal transfer experiment, an exponential decay model was used to calculate the half-life of BSA antibodies in chicks. In the BSA antibody response experiment, comparison of primary and secondary anti-BSA responses of 2- and 6-week-old chicks was performed, using a two-way repeated measures ANOVA, with significance set at P < 0.05.

RESULTS

Hens maintained high anti-BSA titer throughout the breeding season. Maternal transfer of anti-BSA IgG antibodies was documented in all 7 chicks. Anti-BSA titer in chicks decreased in exponential fashion with an average serum IgG half-life of 3.85 days. By 42 days of age, antibodies to BSA were virtually undetectable in all chicks. The primary antibody response of 6-week-old chicks was significantly higher than that of 2-week-old chicks (P = 0.016). No significant difference was observed in the magnitude of the secondary antibody responses between these age groups. Peak anti-BSA IgG antibody responses were reached by 14 days after primary and secondary immunization. Chicks of both age groups generated lower anti-BSA IgG titer than did adult Blue and Gold Macaws.

CONCLUSIONS

Blue and Gold Macaw hens transfer IgG antibodies to their chicks through the egg. The half-life of IgG in newly hatched chicks is approximately 3.85 days. 6-week-old chicks develop higher anti-BSA titers than do 2-week-old chicks, but significantly lower titers than do adult macaws.

CLINICAL RELEVANCE

Information on the nondomestic avian immune system will be useful in the development of vaccination and other preventive health programs for psittacine birds.

Monoclonal antibodies for the measurement of class-specific antibody responses in the green turtle, Chelonia mydas

Monoclonal antibodies (Mabs) were developed against the known immunoglobulin classes of the green turtle, Chelonia mydas. Plasma protein fractions enriched for 5.7S IgY, 7S IgY, and IgM turtle immunoglobulins were used to immunize Balb/c mice for hybridoma production and for hybridoma screening. Fifteen hybridomas produced Mabs with specificity for turtle immunoglobulins and for affinity purified dinitrophenol (DNP) specific turtle antibodies. Three Mabs specific for either turtle 5.7S IgY heavy chain (HL814), 7S IgY heavy chain (HL857), or IgM heavy chain (HL846) were purified and used in an enzyme-linked immunosorbent assay (ELISA) to measure antibody responses in two turtles immunized with 2,4-dinitrophenylated bovine serum albumin (DNP-BSA) over a 10 month period. In both turtles the 7S IgY antibody response developed within 5 weeks of the first inoculation and remained high over the following 9 months. The 5.7S IgY antibody response was detected in one turtle at 3-4 months and in the other at 8 months, and reached high levels in both individuals by 10 months. The IgM responses were difficult to interpret. One turtle had pre-inoculation anti-DNP IgM antibody in its plasma and the other developed only a weak, transient response at about 4 months. The class-specific antibody activity in immune turtle plasma could be strongly inhibited by soluble DNP or by rabbit anti-DNP specific antiserum, showing that these antibody responses were directed predominantly to the DNP hapten on the DNP-BSA antigen. Antibody responses to the BSA carrier could not be detected in either turtle over the course of the immunization. Mab HL814, specific for an epitope on the 5.7S green turtle immunoglobulin heavy chain, will be useful for characterizing the molecular relationships of 5.7S, 7S and IgM heavy chains and the role of 5.7S antibody in humoral immunity in this species. All anti-turtle Ig Mabs were screened against the plasma globulins of Loggerhead (Caretta caretta), Olive Ridley (Lepidochelys olivacea), Kemp's Ridley (Lepidochelys kempi), Hawksbill (Eretmochelys imbricata), and Leatherback (Dermochelys coriacea). While the Mabs specific for IgM and 5.7S IgY reacted only with the green turtle, two Mabs specific for light chain reacted with all species except the leatherback, and nine mabs specific for 7S IgY heavy chain reacted with all five species. Thus, these Mabs may be useful for immunodiagnostic applications in these endangered species as well.

Green turtle fibropapillomatosis: challenges to assessing the role of environmental cofactors

Green turtle fibropapillomatosis (GTFP) is a growing threat to the survival of green turtle (Chelonia mydas) populations worldwide. Recent transmission studies point to an infectious etiology. Several field studies suggest that high GTFP prevalence is associated with marine habitats that have been impacted by agricultural, industrial, or urban development. Environmental contaminants could be involved in GTFP through several plausible mechanisms including cocarcinogenesis and contaminant-induced immune suppression. However, an association of contaminants with GTFP has not been established. A broader perspective is needed when studying infectious diseases such as GTFP in complex ecosystems. Alternative explanations for high GTFP prevalence in some near-shore habitats include the following: a) these habitats provide an optimum physical environment for survival and transmission of the infectious agent; b) these habitats attract a high density of susceptible turtles or harbor a higher density of potential vectors, facilitating transmission of the pathogen in a density-dependent fashion; and c) these habitats may contain other stressors that render turtles more susceptible to GTFP. Application of scientifically rigorous criteria in the epizootiology of GTFP in free-ranging populations remains a formidable challenge.

Taxonomic analysis of the tortoise mycoplasmas Mycoplasma agassizii and Mycoplasma testudinis by 16S rRNA gene sequence comparison

The nucleotide sequences of the 16S rRNA genes of two mycoplasmas, Mycoplasma agassizii (proposed sp. nov.) and Mycoplasma testudinis, isolated from tortoises were determined and used for taxonomic comparisons. Signature nucleotide sequence motifs and overall sequence similarities to other mollicutes positioned these mycoplasmas in the M. hyorhinis and M. pneumoniae phylogenetic groups, respectively. A third, previously unrecognized tortoise mycoplasma was detected by 16S rRNA gene amplification and sequence analysis and was positioned in the M. fermentans phylogenetic group. The 16S rRNA gene of Acholeplasma laidlawii was similarly detected in a tortoise isolate, showing that diverse mollicutes can share the same family of reptilian host.

Mycoplasma agassizii causes upper respiratory tract disease in the desert tortoise

The desert tortoise is listed by the United States government as a threatened species in part of its range. A major contributing factor in the decline of this animal has been the presence of an upper respiratory tract disease (URTD) which is characterized by a chronic disease which eventually leads to severe occlusion of the nares with viscous exudate and destruction of the respiratory epithelium. Electron microscopy of infected tissues demonstrated the presence of a mycoplasma-like organism attached to the respiratory surfaces. The mycoplasma was isolated and designated as a new species, with the proposed name Mycoplasma agassizii. The current study was designed to fulfill Koch's postulates and determine if M. agassizii was the etiologic agent of URTD. Clinically healthy animals with known antibody status were infused intranasally with pooled exudate (n = 8) from ill donor animals, with M. agassizii alone (n = 9) or in combination with Pasteurella testudinis (n = 8), with P. testudinis alone (n = 9), or with sterile broth (n = 12). The pooled exudate was culture positive for M. agassizii. Tortoises which received exudate or M. agassizii alone or in conjunction with P. testudinis were significantly more likely to develop clinical disease (P < 0.0004) than animals which received P. testudinis alone or the broth controls. Tortoises demonstrated a strong immune response to M. agassizii, and seroconversion was seen in all groups with clinical disease. M. agassizii was isolated from the upper respiratory tracts of clinically ill animals up to 6 months postinfection. On the basis of the results of these transmission studies, we conclude that M. agassizii is an etiologic agent of URTD in the desert tortoise.

Detection of antibodies to a pathogenic mycoplasma in desert tortoises (Gopherus agassizii) with upper respiratory tract disease

Mycoplasma agassizii (proposed species novum) is the etiologic agent of an upper respiratory tract disease in the desert tortoise (Gopherus agassizii), which is threatened in most of its range. An enzyme-linked immunosorbent assay (ELISA) for the detection of M. agassizii-specific antibodies in desert tortoises was developed with a monoclonal antibody with specificity for desert tortoise immunoglobulin light chain. Plasma samples from one group of tortoises were tested immediately before and 1 month after challenge either with nasal exudate containing M. agassizii or with a purified preparation of M. agassizii. Plasma samples from a second group of known healthy and sick tortoises were also tested. In the first group, the ELISA detected seroconversion in individual tortoises following challenge with M. agassizii. In the second group, ELISA results were positively correlated with the health status of the tortoises, as determined by clinical and pathologic findings. In addition, the ELISA revealed that tortoise antimycoplasma antibodies were specific for M. agassizii when samples were assayed against M. agassizii, M. pulmonis, M. testudinis, and M. gallisepticum antigens. The observed direct correlation between the presence of nasal mucosal lesions and M. agassizii-specific antibodies proved that the ELISA reliably diagnosed M. agassizii infection in desert tortoises and advocates its use for monitoring M. agassizii-induced upper respiratory tract disease in free-ranging desert tortoises.

Association of 70-kilodalton heat-shock cognate proteins with acclimation to cold

Exposure of young spinach seedlings (Spinacia oleracea L. cv Bloomsdale) to 5 degrees C leads to an increase in the synthesis of several 79-kilodalton proteins that are present in leaf tissue grown at 20 degrees C. Protein sequence analyses and immunological cross-reactivity indicate that this group of proteins belongs to the 70-kilodalton heat-shock family. Steady-state transcript levels and protein synthesis are increased two- to threefold within 1 day, but immunoblot analyses suggest that the steady-state concentration of this protein group in leaf tissue only gradually accumulates at low temperature. It is proposed that the increased synthesis of several members of the 70-kilodalton heat-shock family could result from an influence of low temperature on protein folding and/or assembly processes.

Monoclonal antibodies recognizing normal and retrovirus-transformed chicken hematopoietic cells

The avian hematopoietic system has long been an invaluable model to study the mechanisms of cell growth and differentiation. We have developed six MAbs against either chicken embryonic hematopoietic precursor cells or retrovirus-transformed cells. MAbs Mo1, Mo2, and Mo3 recognized transformation-associated markers expressed in AMV-transformed nonproducer cell line-BM2. Not only were these markers expressed 7 to 10 folds higher on BM2 than on normal monocytic cells, but their expression was drastically reduced when BM2 cells were induced to differentiate into macrophages by PMA. The control of marker expression is associated with v-myb-transforming cascade, since another monocytic lineage-specific oncogene, v-myc, did not enhance the expression of these markers. MAb Em1 detected a marker that is normally present in 20% of the cells from the 30/50% interface of a discontinuous percoll gradient of normal 4-day-embryo yolk sac. Its expression is also found in AEV-transformed cells and MSB1 cells. The epitope for Em1 was exposed after neuraminidase treatment on erythroleukemia cell line 6C2, which suggested that sialylation and/or glycosylation is pivotal in regulating the expression of specific markers in differentiation pathways during embryogenesis and tumorigenesis. MAb Em2 recognized proliferating hematopoietic cells after the fourth day of embryogenesis. MAb Em3, on the other hand, is presumed to be specific for an oncofetal antigen expressed in various transformed cells but only in 10% of the cells from 30/50% interface of a discontinuous percoll gradient of normal 4-day-embryo yolk sac. These MAbs will be useful for dissecting the expression of differentiation markers within normal versus abnormal differentiation pathways in molecular terms.

Enzyme-linked immunosorbent assay for human metallothionein: correlation of induction with infection

Very little information is available concerning the relationship between metallothionein and disease in humans. Recently, investigators have used the Cd-heme method to measure metallothionein levels in human liver samples obtained from autopsy. This assay, however, is not sensitive enough to measure metallothionein in small tissue biopsy specimens. As an alternative, we report the development of a human metallothionein enzyme-linked immunosorbent assay (ELISA). This assay used high-performance liquid chromatography-purified human metallothionein-1 and purified sheep anti-human metallothionein-1 IgG. A limiting antigen coating concentration of 100 ng/ml and a minimal antibody dilution of 1:4000 were chosen. The sensitivity of the ELISA extended to 300 ng/ml (15 ng). The coefficients of interassay and intraassay variation were 15.4% and 4.2%, respectively. Human livers obtained from autopsy were assayed by this method and the values compared with values obtained by the Cd-heme method. The livers were separated by their autopsy reports into four groups: normal, immunosuppression, cancer, and infection. Livers from the infection group (ELISA 2979 micrograms/gm, Cd-heme 1201 micrograms/gm) contained significantly more metallothionein than those from the normal (ELISA, 1035 micrograms/gm, Cd-heme 245 micrograms/gm) and the immunosuppression (ELISA 1272 micrograms/gm, Cd-heme 221 micrograms/gm) groups (p less than 0.05). The cancer group (ELISA 2415 micrograms/gm) also had significantly elevated liver metallothionein levels. We conclude that this ELISA is sensitive enough for the measurement of tissue samples. Furthermore this assay is comparable to the Cd-heme assay in its ability to reflect metallothionein values among various treatment groups. We postulate that hepatic metallothionein induction is mediated by disease-related mechanisms such as interleukin-1, glucocorticoid secretion, or both.

Inhibition of tumor cell-induced platelet aggregation and experimental tumor metastasis by the synthetic Gly-Arg-Gly-Asp-Ser peptide

The mechanism by which the murine fibrosarcoma clone PAK 17.15 induces platelet aggregation [tumor cell-induced platelet aggregation (TCIPA)] was studied because platelet activation by this clone is necessary for metastasis to the lungs. PAK 17.15 TCIPA was completely inhibited by ADP-clearing enzymes, such as apyrase, or a mixture of creatine phosphate and creatine phosphokinase. Thrombin and collagen were not involved in PAK 17.15 TCIPA. Further studies showed that ADP is most likely secreted from activated platelets and that membrane protein(s) on PAK 17.15 cells are responsible for platelet activation. Inasmuch as ADP-dependent platelet aggregation requires fibrinogen and can be inhibited by the Gly-Arg-Gly-Asp-Ser (GRGDS) synthetic peptide, the effect of this peptide on PAK 17.15 TCIPA was studied. PAK 17.15 TCIPA was completely inhibited by the GRGDS peptide (0.4 mM) but not by a control peptide, Gly-Arg-Gly-Glu-Ser (0.8 mM). In addition, the GRGDS peptide inhibited adhesion of PAK 17.15 cells to immobilized fibronectin. As expected, the GRGDS peptide almost completely inhibited lung colonization by iv injected PAK 17.15 cells in C57BL/6 mice. Our results indicate that GRGDS may inhibit pulmonary metastases by interfering with TCIPA as well as with tumor cell adhesion to extra-cellular matrix components in the host.

Functional role of platelets in experimental metastasis studied with cloned murine fibrosarcoma cell variants

The involvement of platelets in experimental metastasis was studied with cloned cell lines derived from PAK 17, a recently induced methylcholanthrene-induced C57BL/6 mouse fibrosarcoma. Tumor cell-induced platelet aggregation and lung colonization assays were used to distinguish three major stable phenotypes among the clones: a low metastatic-low platelet aggregating type, e.g., clone PAK 17.12; a low metastatic-high platelet aggregating type, e.g., clone PAK 17.14; and a high metastatic-high platelet aggregating phenotype, e.g., clone PAK 17.15. Clones with high metastatic but low platelet aggregating potential were not observed in the study. Intravenously injected PAK 17.14 and PAK 17.15 cells, but not PAK 17.12 cells, induced greater than 50% reductions in circulating platelet levels in C57BL/6 mice. Since highly metastatic clone PAK 17.15 cells consistently induced high levels of tumor cell-induced platelet aggregation regardless of the platelet donor, it was selected to study the relationship between its tumor cell-induced platelet aggregation and lung colonizing abilities. (a) A 93% decrease in lung colony number resulted in mice injected with 100 micrograms of prostacyclin immediately before injection of clone PAK 17.15 cells. Prostacyclin was also able to inhibit, in a dose dependent fashion (0-5 ng), platelet aggregation induced by clone PAK 17.15 cells in vitro. (b) A 92% reduction in lung colony number occurred in mice showing marked thrombocytopenia following injection of 100 micrograms of rabbit anti-mouse platelet antibody 24 h before tumor cell injection. (c) A greater than 80% reduction in clone PAK 17.15 lung colony number was observed in mice rendered thrombocytopenic by i.v. injection of 0.038 units of neuraminidase 24 h before i.v. injection of 10(5) tumor cells. These results suggest that platelets are required for successful lung colonization by clone PAK 17.15 cells. However, the presence in this fibrosarcoma of high platelet aggregating-poorly metastatic cells, such as clone PAK 17.14, demonstrates that while the ability to aggregate platelets is necessary for successful metastasis by some tumor cells, it is insufficient if tumor cells lack other critical properties required for completion of the metastatic cascade.

Plasma thrombospondin as an indicator of intravascular platelet activation in patients with vasculitis

The use of plasma thrombospondin (TSP) concentration was investigated as an indicator of intravascular platelet activation. Patients (n = 20) with diseases that have known vasculitis were included in the study. The range and the mean of plasma TSP concentrations of patients with vasculitis were 117 ng/ml to 6500 ng/ml and 791 +/- 1412 ng/ml (mean +/- SD); the range and the mean of plasma TSP concentrations of control individuals (n = 33) were 13 ng/ml to 137 ng/ml and 59 +/- 29 ng/ml. When plasma TSP concentrations were correlated with plasma concentrations of another platelet activation marker, beta-thromboglobulin (beta-TG), it was found that the TSP concentration increased exponentially as the plasma beta-TG level rose. A positive correlation between plasma levels of plasma TSP and serum fibrin degradation products was also observed. The results suggest that platelets are the primary source of plasma TSP in patients with various vasculitis and that plasma TSP can be a better indicator than beta-TG to assess intravascular platelet activation due to its longer circulation half life.

Viral oncolysis in the A2G mouse revisited: monoclonal antibody-mediated tumor rejection

A2G mice can be immunized against the Ehrlich ascites tumor (EAT) by influenza virus oncolysis or with influenza virus oncolysates. To facilitate studies of the cellular antigens immunopotentiated by viral oncolysis, monoclonal antibodies (mAbs) against EAT cells were produced from postoncolytic EAT-immune A2G mice. Reciprocal competitive binding on EAT cells was used to classify the mAbs into epitope-related groups. One mAb, 198.9, could fully protect A2G mice against EAT cell challenge, could rescue A2G mice from an established EAT, and could mediate lysis of EAT cells in vivo. mAb 198.9 provides a new tool for studying the biochemical characteristics and immunological properties of a cellular antigen centrally involved in this model.

A monoclonal antibody-based enzyme-linked immunosorbent assay for quantitation of plasma thrombospondin

An enzyme-linked immunosorbent assay was developed to quantitate the platelet secretory glycoprotein, thrombospondin (TSP), in plasma. Specificity of the assay was provided by using an anti-TSP monoclonal antibody (McAb) to coat 96 well polystyrene assay plates. The effective range of the standard curve for the assay was between 2.5 ng/mL and 500 ng/mL. Interassay and intraassay variations were 6.9% and 7.5%, respectively. To avoid spontaneous release of TSP from platelets after the blood was drawn, and to obtain a valid measurement of plasma TSP concentration, it was essential to place and maintain blood samples on ice immediately after blood was drawn and to separate plasma from cellular constituents within two hours. The mean plasma TSP concentration of 24 healthy adults was 64.3 +/- 18.0 ng/mL (mean +/- SD). The TSP concentration of pooled normal human serum (n = 6) was 15.9 micrograms/mL. Interference occurred when undiluted plasma or serum samples were assayed. This interfering effect could be eliminated completely by a tenfold dilution of plasma or serum samples before the assay. The assay also was applied successfully to quantitate TSP release from platelets after induction of aggregation by different platelet-aggregating agents.

Functional involvement of thrombospondin in platelet aggregation induced by low versus high concentrations of thrombin

Thrombospondin (TSP) is a major platelet secretory glycoprotein. Earlier studies of various investigators demonstrated that TSP is the endogenous platelet lectin and is responsible for the hemagglutinating activity expressed on formaldehyde-fixed thrombin-treated platelets. The direct effect of highly purified TSP on thrombin-induced platelet aggregation was studied. It was observed that aggregation of gel-filtered platelets induced by low concentrations of thrombin (less than or equal to 0.05 U/ml) was progressively inhibited by increasing concentrations of exogenous TSP (greater than or equal to 60 micrograms/ml). However, inhibition of platelet aggregation by TSP was not observed when higher than 0.1 U/ml thrombin was used to activate platelets. To exclude the possibility that TSP inhibits platelet aggregation by affecting thrombin activation of platelets, three different approaches were utilized. First, by using a chromogenic substrate assay it was shown that TSP does not inhibit the proteolytic activity of thrombin. Second, thromboxane B2 synthesis by thrombin-stimulated platelets was not affected by exogenous TSP. Finally, electron microscopy of thrombin-induced platelet aggregates showed that platelets were activated by thrombin regardless of the presence or absence of exogenous TSP. The results indicate that high concentrations of exogenous TSP (greater than or equal to 60 micrograms/ml) directly interfere with interplatelet recognition among thrombin-activated platelets. This inhibitory effect of TSP can be neutralized by anti-TSP Fab. In addition, anti-TSP Fab directly inhibits platelet aggregation induced by a low (0.02 U/ml) but not by a high (0.1 U/ml) concentration of thrombin.(ABSTRACT TRUNCATED AT 250 WORDS)

Melanoma cells growing in aggregates on a non-adhesive poly(HEMA) substrate exhibit polykaryocytosis but do not develop an increased metastatic capability

B16-F1 melanoma cells were plated onto plastic tissue-culture dishes rendered non-adhesive for cells by coating with 0.12 per cent poly(2-hydroxyethyl methylacrylate), poly(HEMA). These growth conditions caused the normally flat, adherent B16-F1 cells to grow as single cells in suspension. Within 24 hours, the rounded cells formed aggregates and grew at a slower rate than control cells grown at the same density on untreated plastic dishes. Microscopic observations provided evidence that polykaryocytosis was occurring among the aggregates. Following replating onto standard adhesive tissue-culture plastic, 20-30 per cent of the aggregates were observed to contain varying numbers of multinucleated giant cells (polykaryocytes). The study has revealed a previously undescribed propensity of certain B16-F1 cells cultivated as aggregates in suspension to develop into polykaryocytes, most probably as a result of spontaneous tumor cell-tumor cell fusion. The possible relevance of this behavior in vitro to events in tumor progression is discussed. This study, however, does not support the findings of others that the metastatic capability of B16-F1 cells is increased by such non-adherent culture conditions. No increase in metastatic potential was observed for B16-F1 cells, or for a low metastatic clone (F1-7) derived from it, grown for 72 or 96 hours in a spherical configuration compared to control cells grown in a flat, adherent monolayer.