Detection of picogram quantities of potyviruses using a dot blot immunobinding assay

Effects of smoking and treatment status on periodontal bacteria: evidence that smoking influences control of periodontal bacteria at the mucosal surface of the gingival crevice

BACKGROUND

We examined whether smoking status could influence growth of potentially pathogenic bacteria in the periodontal environment of treated and untreated periodontal patients.

METHODS

We have previously reported effects of treatment status on marker bacteria in our patients. We established a history of any smoking during 6 months prior to microbiological sampling (F-ME, 16 smokers out of 64; MHM, 70 smokers out of 185). We used a commercial immunoassay to quantitate Porphyromonas gingivalis, Prevotella intermedia, and Actinobacillus actinomycetemcomitans in paper point samples from periodontal sites.

RESULTS

Logistic regression showed that in smokers, neither P. gingivalis nor A. actinomycetemcomitans was quantitatively increased, while P intermedia was somewhat increased. Multiple regression demonstrated that smoking disrupts the positive relationship between increasing probing depth and increasing bacterial growth that is found in non-smokers. In smokers, growth of marker bacteria at shallow sites (< or =5 mm) was significantly increased to the levels found at deeper sites (>5 mm) in both smokers and non-smokers. Supragingival plaque biofilm was identified as a reservoir for marker bacteria; smokers and nonsmokers had equal ranges of oral cleanliness.

CONCLUSIONS

Smoking-associated periodontitis is not simply a reflection of oral cleanliness. Smoking extends a favorable habitat for bacteria such as P. gingivalis, P. intermedia, and A. actinomycetemcomitans to shallow sites (< or =5 mm). Molecular byproducts of smoking interfere with mechanisms that normally contain growth of damaging bacteria at the surface of the oral mucosa in gingival crevices. In this way, smoking can promote early development of periodontal lesions.

Performance of a commercial immunoassay for detection and differentiation of periodontal marker bacteria: analysis of immunochemical performance with clinical samples

BACKGROUND

We employed a commercial immunoassay for simultaneous detection and differentiation of marker bacteria Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia and reassessed the immunochemical performance of the assay.

METHODS

We compared the analytical performance of the immunoassay in our study of clinical samples from 249 periodontal patients in 2 private periodontal practices with the previously reported analytical performance of the same immunoassay. We also compared immunoassay measurements of the marker bacteria in clinical samples with values obtained in other studies by direct culture of the same organisms.

RESULTS

The assay produced 3 times more high-end readings than reported previously. We also reassessed and revised previously published calibration curves for the immunoassay. The immunoassay provided measurements of the marker bacteria in clinical samples from our patients that were comparable to and consistent with measurements of the same bacteria by direct culture in other studies.

CONCLUSIONS

We ascribe the increased sensitivity of the immunoassay in our study to: 1) a more standardized and vigorous sample dispersion that improves release of particulate and soluble antigens from dental plaque biofilm, and 2) better visualization of the reaction product of the enzyme-linked immunoassay. High-technology assays, such as diagnostic immunoassays, have a significant potential for future development in dental diagnosis, because they simplify detection and measurement of biologically important markers such as specific bacteria in clinical samples. Commercial assays also have an important potential for standardization of clinical measurements of biological markers.

Sensitive avidin-biotin amplified fluorogenic enzyme immunoassay using biotinylated monoclonal antibodies for the identification and quantitation of virus

A highly sensitive amplified fluorogenic enzyme-linked immunosorbent assay (FELISA), which utilizes the high affinity interaction of the vitamin biotin for the multiple binding sites on the glycoprotein avidin, was developed for the detection and identification of a model virus, Newcastle disease virus (NDV). Monoclonal antibodies (MCA) directed against the virus were purified and labelled with biotin. Biotinylated MCA was then used with avidin-labelled enzyme and a fluorogenic substrate to detect NDV adsorbed directly on nitrocellulose membranes. Reagents were standardized and, using purified virus, the theoretical lower limit of test sensitivity of the amplified FELISA was determined to be 1 fg/ml of test sample (50 ag/well). The specificity of the amplified FELISA was evaluated by challenging the assay system with homologous and heterologous strains of NDV, and with other serologically related and unrelated viruses. The test was simple to perform and multiple samples could be conveniently assayed with results obtainable in 3-4 h.

A general method for the detection of potyviral gene products in plant protoplasts and tissue

A rapid immunostaining procedure for detecting potyviral antigens in individual protoplasts, isolated mesophyll cells, and epidermal strips of Nicotiana tabacum is described. Although all specific antibodies tested detected potyviral antigens in electroporated protoplasts, those against cytoplasmic inclusion (CI) protein provided the most useful results. The number of protoplasts reacting with anti-CI increased with time after inoculation, roughly in parallel with the accumulation of capsid protein, which was measured independently by enzyme-linked immunosorbent assay. Potyviral gene products were also detected in epidermal strips and mesophyll cells separated from systemically infected leaves, indicating that the immunostaining method is generally applicable and that it may prove useful for studying the movement of potyviruses from cell to cell in intact plants.

Sensitive fluorogenic enzyme immunoassay on nitrocellulose membranes for quantitation of virus

A highly sensitive fluorogenic enzyme-linked immunosorbent assay (FELISA), which utilizes nitrocellulose membranes as solid phase support, has been developed for the detection and identification of virus in clinical samples. Reagents were standardized and, using purified Newcastle disease virus (NDV) as a model, the theoretical lower limits of test sensitivity of the FELISA were compared, in both "sandwich" and "indirect" formats, to those of a comparable chromogenic enzyme-linked immunosorbent assay (CELISA). Of the systems evaluated, the "sandwich" FELISA exhibited maximum sensitivity and detected 10 fg of purified virus protein per milliliter of test sample (500 ag per test volume). Specificity of the "sandwich" FELISA was evaluated by challenging the system with heterologous strains of NDV and with other serologically related and unrelated viruses. In a clinical trial in which fecal materials from chickens undergoing vaccination with NDV were assayed directly by FELISA, the virus was detected from the first to approximately the tenth day post-vaccination. The test is simple to perform and results can be obtained in approximately 4 h.

Detection of herpes simplex virus type 1 in herpetic ocular diseases by DNA-DNA hybridization using a biotinylated DNA probe

A diagnostic hybridization assay for detecting herpes simplex virus type 1 (HSV-1) in ocular specimens was developed using cloned viral DNA as a probe. This hybridization assay is based on visualizing a biotinylated probe that is hybridized to the target DNA by a streptavidin/alkaline phosphatase system. The time required for performing this assay system is only two days. This assay system could detect a probe which had been hybridized to as little as 1 pg of homologous DNA and did not cross-react with DNA of other human herpes viruses except that of herpes simplex virus type 2 (HSV-2) which showed weak cross-reactivity. The assay system was applied to experimental keratitis in albino rabbits and clinical specimens. In experimental keratitis in rabbits it was possible to detect HSV-1 DNA in the eye swab samples at least until the ninth day after virus inoculation. Five clinical specimens collected from patients with corneal ulcer or blepharitis contained HSV-1 DNA in spite of the failure of demonstration of viral antigen and/or virus isolation in two cases.

A quantitative immunobinding assay for vitamin D-dependent calcium-binding protein (calbindin-D28k) using nitrocellulose filters

A sensitive dot immunobinding assay has been developed for the quantitative determination of vitamin D-dependent calcium-binding protein (calbindin-D28k; CaBP) in rat and human kidney and brain. Protein samples are spotted onto nitrocellulose sheets, fixed, and then rinsed with Tris-buffered saline. The remaining protein binding sites are blocked with bovine serum albumin, gelatin, or nonfat dry milk protein and the filters are then incubated sequentially with antiserum to calbindin-D28k (1:500 dilution) and 125I-protein A (200,000 cpm/ml). After washing, the radioactivity bound to each sample is quantitated by counting in a gamma counter. The sensitivity of the assay is such that 10 ng calbindin-D28k can be accurately quantitated. The highest levels of CaBP were detected in kidney (7.8 +/- 0.5 micrograms/mg protein) and cerebellum (22.1 +/- 1.4 micrograms/mg protein). Ten micrograms calmodulin, lactalbumin, or parvalbumin and 100 micrograms liver extract showed no reactivity in the assay. The assay is precise (intraassay variability, 4.0%) and reproducible (interassay variability, 8.8%). There was good agreement between the data in this assay and the data we obtained using radioimmunoassay (RIA). The assay has several advantages over the RIA. Iodination of pure antigen is not required and it is possible to detect membrane-bound and insoluble antigens using this assay. Also, the antiserum and 125I-protein A solutions can be saved and reused. This assay represents a major modification of the original immunobinding assays which used the less sensitive peroxidase stain. It is also an improvement over previous 125I immunobinding assays which were not quantitative but were used as antigen "spot tests" or which required iodination of the antibody.