Category Blogging

With this entry we conclude the series of posts where we have delved into the peculiarities of the different types of ELISA.

After knowing the rationale and procedure on which each of them is based and seeing the main characteristics that differentiate them , today we will focus on analyzing the advantages and disadvantages of the different types of ELISA .

ADVANTAGES AND DISADVANTAGES OF THE DIFFERENT TYPES OF ELISA

In order to make this entry as visual and practical as possible, we will summarize and group the main advantages and disadvantages of the different types of ELISA in the following table:

TYPES OF ELISA	ADVANTAGE	DISADVANTAGES
ELISA direct	1.- The protocol is simple and fast.2.- There is no possibility of cross reactivity with the secondary antibody.3.- Less probability of error due to the use of fewer reagents and steps in the procedure.	1.- It can give more background noise, since other proteins present in the sample (in addition to the antigen of interest) can adhere to the plate.2.- There is no signal amplification since secondary antibodies are not used, which reduces the sensitivity of the assay.3.- The primary antibody must be labeled, which reduces the flexibility of the assay, and can be used to alter its immunoreactivity.
Indirect ELISA	1.- High sensitivity, since the use of secondary antibodies makes it possible to amplify the signal.2.- High flexibility due to the fact that the same secondary antibody can be used with different primary antibodies, which also translates into an economic benefit.3.- The primary antibody maintains its immunoreactivity intact by not being conjugated.	1.- Protocol more complex than the direct ELISA, which includes additional incubation steps with the secondary antibody.2.- The use of secondary antibodies can lead to cross reactivity.
ELISA sandwich	1.- High flexibility, since detection can be done both by direct and indirect procedure.2.- High sensitivity and specificity, due to the use of two antibodies against the same antigen.	1.- The antigen must be large enough to allow two antibodies to bind simultaneously.2.- It is not always easy or possible to have pairs of antibodies that work well in this type of assay.
Competitive ELISA	1.- High flexibility: it can be based on a direct, indirect or sandwich procedure.2.- High sensitivity, robustness and consistency.3.- It allows the detection of small size antigens and in low concentrations.4.- It does not require the previous processing of the samples to be analyzed.	1.- The protocol is relatively complex.2.- Requires the use of inhibition antigen.

As a conclusion after analyzing the advantages and disadvantages of the different types of ELISA, we can determine the ideal use of each of them :

• Direct ELISA : it is the technique of choice to analyze the immune response to a certain antigen, for example, in the production of antibodies or in diagnostic procedures.
• Indirect ELISA : test of choice to determine the total concentration of antibodies in a certain sample.
• Sandwich ELISA : technique of choice when it comes to analyzing complex samples, without the need to purify the antigen previously.
• Competitive ELISA : ideal technique to detect antigens of small size or that are present in very low concentrations in the sample.

For all medicines and therapeutic agents , the WHO (World Health Organization) assigns a generic name known as INN ( International Non- proprietary Name ) in order to facilitate the identification of the active pharmaceutical ingredients that comprise it.

This INN is also applicable in the case of monoclonal antibodies , which are assigned a generic name based on a specific schematic structure. The International Nonproprietary Name (INN) for each monoclonal antibody is composed of a prefix, two intermediate particles that serve the type of target to which the monoclonal antibody is directed and the species of origin thereof, respectively, and a common suffix for all of them.

Want to know what the names of the antibodies mean? In this entry we analyze the scheme and the specific structure that is followed in the monoclonal antibody nomenclature.

MONOCLONAL ANTIBODIES NOMENCLATURE

As we said, the name or INN of each monoclonal antibody is assigned based on a scheme that includes 4 aspects:

• Random prefix
• Target type
• Origin species
• Common suffix

Let’s take a closer look at each of them:

1.- RANDOM PREFIX

This part of the monoclonal antibody name or INN does not meet any specific criteria. Its “function” is to distinguish one monoclonal antibody from another (since the name of two antibodies directed at the same target and originating from the same species will only be distinguished by the prefix), so it must be unique, and it is free choice by the manufacturer of the same.

2.- TARGET TYPE

After the random prefix, a particle representing the type of target to which the monoclonal antibody is directed is added. This particle generally consists of a consonant to which a vowel is added only in the case where the particle representing the origin of the antibody begins with a consonant.

3.- ORIGIN SPECIES

Third, the particle corresponding to the origin of the monoclonal antibody is added, and it can be of animal, chimeric, humanized or totally human origin.

4.- SUFFIX

The names of all monoclonal antibodies will always end with the common suffix -mab , indicating that it is an immunoglobulin or a fragment of it, provided that it includes at least one variable domain.

Although the monoclonal antibody nomenclature may seem confusing or complicated at first glance, it is actually very precise and easy to understand based on these criteria that we have just discussed, and which we summarize in the following table:

Prefix	Target type	Origin species	Suffix
Random	-b (a) – bacterial-am (i) – serum amyloid protein (SAP) / amyloidosis (pre-substem)-c (i) – cardiovascular-f (u) – fungal-gr (o) – skeletal muscle mass related growth factors and receptors (pre-substem)-k (i) – interleukin-l (i) – immunomodulating-n (e) – neural-s (o) – bone-tox (a) – toxin-t (u) – tumor-v (i) – viral	a- rat-axo- rat-mouse (pre-substem)-e- hamster-i- primate-o- mouse-u- human-vet- veterinary use (pre-substem)-xi- chimeric-xizu- chimeric-humanized-zu- humanized	-mab

To finish, we leave you some examples to understand the information provided by the monoclonal antibody nomenclature:

• BASILIXIMAB
  • Basi- (prefix)
  • -li- (immunomodulator)
  • -xi- (of chimeric origin)
  • -mab (monoclonal antibody)

• INFLIXIMAB
  • Inf- (prefix)
  • -li- (immunomodulator)
  • -xi- (of chimeric origin)
  • -mab (monoclonal antibody)

• PALIVIZUMAB
  • Pali- (prefix)
  • -vi- (against a viral antigen)
  • -zu- (humanized)
  • -mab (monoclonal antibody)

• TRASTUZUMAB
  • Tras- (prefix)
  • -tu- (against tumor antigens)
  • -zu- (humanized)
  • -mab (monoclonal antibody)

At the Gene Mapping Workshop held during the 22nd Conference of the International Society for Animal Genetics (ISAG) held in East Lansing, Michigan, USA it was resolved unanimously that animal gene nomenclature should “follow the rules for human gene nomenclature, including the use of identical symbols for homologous genes and the reservation of human symbols for yet unidentified animals genes”. [Animal Genetics (1991) 22, 97-99] The report from the workshop cited the human gene nomenclature rules and lists of mapped genes as published in Cytogenetics and Cell Genetics proceedings of the Human Gene Mapping Workshops. Approved human gene symbols and nomenclature rules can now be accessed through the Web site maintained by the HUGO Gene Nomenclature Committee

The HUGO Gene Nomenclature Committee is responsible for approving and implementing unique human gene symbols and names, and works closely with the Mouse Genome Database and other organism databases. Considerable efforts are made to approve symbols acceptable to workers in the field, but sometimes it is not possible to use exactly what has previously appeared in the literature. In such cases the previously used symbols are listed as aliases for the approved nomenclature in the Human Gene Nomenclature Database (Genew) and LocusLink, to allow retrieval of all the information available for each gene.

Contact: info@thearkdb.org

ARKdb can be queried in a number of ways. The main ways of querying are by locus/marker, by published reference or by map. You can also query by clone or library, although these tend to be less well-used areas of the system. Each species database is accessed in the same way. Brief details of the options available are given below. A more detailed guide to the text-based interfaces (locus and reference queries) can be found using the help links in the relevant query pages..

Locus

You can query for a locus based on its symbol, its description (name), chromosome position or marker type. You can also limit the search to markers mapped on a specific mapping population and further refine this search by limiting the search to a particular mapping cross sex. However, you should be aware that it is possible to generate queries that return no markers simply by choosing the incorrect sex in this form, so the option should only be used if you really know what you are doing. You can also partially customise the report format by choosing to display primer details (in which case the query will return symbol, primer sequences and EMBL accession numbers) and sort criteria.

Reference
You can look for specific references by full or partial title, author, journal name or publication year. Alternatively you can use the internal database identifier unique to each reference (accession number).

Map
You can query for maps using either the “advanced” or the “simpler” interface. Maps are selected by species, chromosome and published map name – you can alternatively use your own data to generate maps.

Clone
You can query the database for details of clones used in mapping experiments. The searchable fields are Clone Name, Vector and Cloning Sites.

Library
You can query the database for details of libraries from which clones used in mapping experiments were derived. The searchable fields are Library Name, Vector and Host.

ARKdb arose initially from the needs of a project co-ordinated at Roslin Institute to map the pig genome. The original intention was to utilise the Jackson Laboratory’s then current mouseGBASE database design, and this was actually implemented for pigs, chickens and sheep. However, it soon became clear that the nature of genome mapping in farmed animal species differed significantly from the methods and population types employed in mouse genetics. These differences meant that the schema we had didn’t fit our data requirements and the decision was taken to develop our own database system.

Because we needed a system that would work for all of the species that we work with at Roslin, we tried to make the design as generic as possible. We hope that we have managed to strike a balance between generalisation and utility. In any case, the number of species that have adopted the ARKdb database system for their genome mapping informatics needs extends considerably beyond those initially in mind when we established the schema.

ARKdb species databases at this site