PDA Technical Glossary

PDA Technical Glossary

PDA Technical Reports are highly valued membership benefits because they offer expert guidance and opinions on important scientific and regulatory topics and are used as essential references by industry and regulatory authorities around the world. These reports include terms which explain the material and enhance the reader’s understanding.

The database presented here includes the glossary terms from all current technical reports. The database is searchable by keyword, topic, or by technical report. Each definition provided includes a link to the source technical report within the  PDA Technical Report Portal.

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Adverse Event (AE) Report
An AE report is a communication to the U.S. FDA of an undesirable sign or symptom associated with use of a drug as required and detailed by 21 CFR 314.80. These reports are logged into the U.S. FDA’s Adverse Event Reporting System (AERS). Drug manufacturers are required to report adverse event information to FDA. These reports may also may be voluntarily submitted to the FDA directly by healthcare professionals or the general public at Med Watch. The reports are reviewed, safety issues are monitored, and data are periodically analyzed and assessed by the Center for Drug Evaluation and Research (CDER). (TR55)
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Aggregation
Clumping of proteins, viruses, or bacteria that may arise from several mechanisms and may be classified in numerous ways, including soluble/insoluble, covalent/noncovalent, reversible/irreversible, and native/denatured. (TR47)
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Bacteriophage
A bacteriophage is any one of a number of viruses that infect bacteria. The term is commonly used in its shortened form, “phage”. (TR41) (TR 47)
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Batch Filtration Process
In a batch filtration process, the entire volume to be filtered is held in a single feed tank. The retentate stream is recycled back to that single feed tank. (TR15)
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Biomethylation
The enzyme chlorophenol o-methyltransferase responsible for fungal methylation has been isolated in cell-free extracts. Biomethylation, in this context, may be seen as a detoxification mechanism, although it plays a role in the production of mycotoxins by secondary metabolism. Slightly xerophilic fungi frequently associated halophenol biomethylation include Trichoderma longibrachiatum, Trichoderma virgatum, Aspergillus sydowii, and Penicillium islandicum. (TR55)
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Bracketing
A demonstration of unit operation performance at two different values of a given parameter (e.g., ionic strength, dwell time or temperature), allowing the use any values of that parameter falling within this range. (TR41)
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Bracketing Approach
A scientific approach for defining product/load characteristics (e.g., viscosity, container sizes, container fill volumes, item sizes, loading configurations) that are tested (in a qualification study or validation study) at upper and/or lower limits. (TR1) (TR61) A validation method that tests the extremes of a process or product. The method assumes the extremes will be representative of all the samples between the extremes. (TR26)
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Cell Substrate
The host cells that are used to propagate or detect viruses. (TR 47) Cells used for the manufacture of a biological medicinal product. (TR 71) (TR 83)
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Cytopathic Effect (CPe)
Morphological changes induced by viruses in infected cells in invitro culture. They are usually localized around a site of initial infection and vary in appearance based on the virus and the cultured cell. (TR47)
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Cytopathic Virus
Viruses where infection of cells results in microscopically visible degeneration of the cells or other morphological changes. (TR47)
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De Novo Sequence Assembly
Assembly of short reads of a sequence to generate a contiguous sequence (contig). (TR71)
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Dynamic Light Scattering (DLS)
A technique used to measure the size and size distribution of particles. Particles suspended in a solution will cause scattering of light and the extent of the scattering is related to the size and shape of the particles. (TR47)
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Endogenous Virus
Endogenous Virus-Like Particles – (e.g., Type C endogenous retroviruses)
Virus-like entity whose genetic material is stably integrated into the germ line of an organism or cell line. Cell lines (notably CHO) may constitutively produce virus-like particles, which are typically noninfectious but still of safety concern. Model retroviruses are generally used as surrogates to measure virus-like particle clearance. (TR41)
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Endpoint PCR
A classical PCR method based on repeated cycling of the reaction mixture between two or three temperatures (denaturing, annealing, and extension) with detection of the amplified product after reaction completion (e.g., by agarose gel electrophoresis). (TR50)
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Extraction Control
A known test article processed with a nucleic acid extraction procedure in order to ensure the proper extraction of nucleic acid. (TR50)
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Extraction Recovery
The efficiency of extraction of target analyte from a test matrix. It is usually measured as ratio (percentage) of analyte amount extracted from the matrix to that originally present in the matrix before extraction. (TR50)
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Focus Forming Unit (FFU)
A measure of virus infectively based on formation of a region or “focus”, of infected cells within a monolayer culture that is caused by viruses that do not kill their host, but rather transform them. The number of foci is directly correlated to the number of infectious virus particles. (TR47)
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Frank (Canonical) Pathogens
Microorganisms responsible for infection in healthy individuals (i.e., individuals with normal operative and functional host defense mechanisms) that may be acquired from exposure to other infected people or animals, environmental reservoirs (exogenous) or the individual’s normal (endogenous) microbial flora. (TR67)
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Genome Copy (GC)
An amount of nucleic acid equivalent to the genetic complement present in the genome of a single microorganism. (TR50)
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Genotypic
Relating to those characters that reside in the genetic complement of a specific strain of a specific organism. (TR51)
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Hemadsorption
Adherence of red blood cells to virus-specific antigens on the surface of infected cells. In cellbased in vitro assays the reaction is used as an end point for virus detection. (TR47) (TR71)
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Hemagglutination
A clumping together or agglutination of red blood cells. In the context of this Technical Report hemagglutination indicates presence of virus that binds to erythrocytes. (TR47) The clumping of red blood cells by binding to virus particles. The hemagglutination reaction is used in cell-based in vitro assays as an end point for virus detection. (TR71)
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Hybridization
The formation of a double-stranded complex of complementary strands of nucleic acids (e.g., a primer and single-stranded DNA or RNA) (TR50)
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Indicator Cells
Cell lines that are used in in vitro assays to detect the presence of viral agents. (TR71)
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Infectious Unit
A measure of quantity of infectious virus. An infectious unit does not necessarily reflect the number of virus particles, as virus preparations also contain noninfectious virus particles and, depending on the cellular host, more than one virus particle may be necessary to infect a cell. (TR47)
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Inoculated Carrier
A carrier upon which a defined number of test organisms have been deposited. (TR51)
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Internal Control
A reaction performed to provide confirmation of adequate performance of the NAT assay including preparation of nucleic acid, its amplification using appropriate amplification technology, and analysis of amplified products. An example is the amplification of a housekeeping gene from the production cell line which provides a positive signal even in the absence of contaminant DNA. (TR50)
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Latent Virus
Latency is the ability of a virus to be dormant (latent) within a cell (for example, genetic episomes; provirus). Under certain conditions the virus may become active and produce particles. (TR71)
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Limiting Dilution
In the context of this Technical Report the limiting dilution technique is used for virus cloning. The virus suspension is diluted until virus is no longer detectable. The dilution immediately before the dilution where infection of cells is no longer detectable is considered to contain only one virus particle or a very low number of virus particles. (TR47)
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Log Reduction
Log reduction is defined as the first log being 90%, the second log being 9% and the third log being 0.09% of the original inoculums. (TR70)
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Matrix Spike Control
An internal control in which an amplifiable amount of nucleic acid is added to a test article to determine inhibition of the PCR. This addition is usually performed pre-extraction and should provide a weak signal 100% of the time. Also known as “interference control”. (TR50)
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Media
The part of the filter through which fluid passes that retains particles during filtration. (TR45)
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Melting Temperature (Tm)
The calculated or observed temperature for a primer/nucleic acid mixture at which 50% of primer-binding sites are in single strand form. (TR50)
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Monodispersed particles
Particles of uniform size in a dispersed phase. In the case of viruses, this term refers to free virus particles not agglomerated to other viruses or proteins in solution. (TR41)
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Most Probable Number (MPN) Method
A statistical method of estimating the number of viable organisms suspended in a liquid. (TR51)
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Nominal Molecular-Weight Cutoff (NMWCO)
A manufacturer’s measure of an ultrafiltration membrane based on a defined solute-retention coefficient. (TR15)
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Nominal Pore Size Rating
A filter rating with an arbitrary value, indicating a particulate size range at which the filter manufacturer claims the filter removes some percentage. Nominal ratings vary from manufacturer to manufacturer and may not be suitable to compare filters among manufacturers. Processing conditions, such as operating pressure and concentration of contaminant may have a significant effect on the retention efficiency of the nominally rated filters. (TR41)
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Nonspecific Model Virus
A virus used for characterization of viral clearance of the process when the purpose is to characterize the capacity of the manufacturing process to remove and/or inactivate viruses in general (i.e., to characterize the general viral clearance capacity of the purification process.) (TR41)
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Nucleic Acid Sequence Based Amplification (NASBA)
An isothermal amplification method targeting RNA in which amplifications of RNA occurs via DNA intermediates. Each of the DNA templates can make 100 to 1000 copies of RNA amplicons, potentially resulting in the production of greater than a billion amplicons. (TR50)
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Nucleic Acid Standard
A sample with a precisely measured content of specific nucleic acid. A nucleic acid standard can be serially diluted to assess the limit of detection of an NAT assay or to create a standard curve for Q-PCR to determine the concentration of target nucleic acid. (TR50)
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Plaque Forming Unit (PFU)
A measure of virus infectively based on formation of a region, or “plaque” of lysed cells within a monolayer culture caused by viruses that kill and disrupt their host cell. The number of plaques is directly correlated to the number of infectious virus particles. (TR47)
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Plasmid
An extra-chromosomal DNA molecule in bacteria which is capable of replicating independently of the host chromosomal DNA. Plasmids are often used as positive controls for NAT assays. (TR50)
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Polymerase Chain Reaction (PCR)
A technique widely used in molecular biology in which a DNA polymerase is used to amplify a piece of DNA by in vitro enzymatic replication. As PCR progresses, the DNA thus generated is itself used as a template for replication. This sets in motion a chain reaction in which the DNA template is exponentially amplified. This technique may be used to quantify virus. (TR41) (TR47)
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Primer
A short synthetic single-stranded nucleic acid complementary to a specific sequence of a target gene, DNA or RNA. It usually serves to initiate the de novo synthesis of nucleic acid from a template. (TR50)
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Pyrogen
Any substance capable of eliciting a febrile (or fever) response upon injection or infection (as in endotoxin released in vivo by Gram-negative bacteria. (TR3) Fever-producing substance (TR69) A material that elicits a pyrogenic response (fever). (TR70)
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Q-PCR Probe
A synthetic, chemically-labeled single-stranded nucleic acid complementary to a selected sequence within a DNA sequence to be amplified using forward and reverse primers in a Q-PCR reaction. A probe is typically labeled with both a fluorophor and quencher. The latter inhibits fluorescence until the quencher and fluorophore are separated by the exonuclease activity of DNA polymerase. (TR50)
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Relevant Virus
A virus used in process evaluation studies that either is the identified virus, or of the same species as the virus known to or likely to contaminate the cell substrate or any other reagents or materials used in the production process. (TR41)
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Reporter Gene
A coding sequence linked to a gene or promoter of interest. It is generally used to determine activation of the promoter or expression of the gene of interest in a cell or organism. (TR50)
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Reverse Transcriptase PCR (RT-PCR)
A technique for amplifying a defined segment of a RNA molecule. The RNA is first reverse-transcribed into complementary DNA (cDNA), followed by amplification of the cDNA using PCR. (TR50)
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