Customize FTA Antibody

Description

Definition and Purpose

The FTA Antibody refers to immunoglobulins detected in the Fluorescent Treponemal Antibody Absorption (FTA-ABS) test, a confirmatory assay for syphilis. Unlike non-treponemal tests (e.g., RPR, VDRL), which detect nonspecific antibodies, the FTA-ABS identifies T. pallidum-specific IgG antibodies . Its primary roles include:

Confirming syphilis after a reactive non-treponemal screening test .
Excluding neurosyphilis when cerebrospinal fluid (CSF) FTA-ABS is negative .

Mechanism of Action

The FTA-ABS test involves:

Step	Description
Antigen Preparation	Lyophilized T. pallidum extracted from rabbit testicular tissue is fixed onto slides .
Absorption	Patient serum is pre-treated with Treponema phagedenis extract to remove cross-reactive antibodies .
Detection	Secondary antibodies labeled with FITC (anti-treponemal) and TRITC (anti-human) fluorophores confirm antibody binding .

Sensitivity and Specificity

Sensitivity:
- Primary syphilis: 78.2% .
- Secondary/early latent syphilis: 95–100% .
- Neurosyphilis: Near 100% sensitivity in CSF .
Specificity:
- 98.5% in serum, though cross-reactivity occurs with T. pertenue and autoimmune conditions (e.g., lupus) .

Diagnostic Limitations

Cannot monitor treatment response (remains positive lifelong) .
Subjective interpretation requires skilled technicians .

Comparative Performance

Test	Sensitivity (Primary Syphilis)	Specificity	Notes
FTA-ABS	78.2%	98.5%	Subjective, manual
TPPA	94.5–96.4%	100%	Automated, objective
Immunoassays (EIA/CIA)	94.5–100%	97–99%	Preferred for high-throughput screening

Key findings:

FTA-ABS underperforms in primary syphilis compared to TPPA and immunoassays .
TPPA is now recommended over FTA-ABS due to higher specificity and automation .

Cross-Reactivity

False positives occur in 3.6% of pregnancies and 20% of Epstein-Barr virus cases .
Lupus and leprosy sera may yield false reactivity .

Neurosyphilis Application

CSF FTA-ABS has a 96% sensitivity for neurosyphilis but cannot differentiate active from past infections .

Automation Challenges

FTA-ABS remains labor-intensive, prompting shifts toward automated treponemal immunoassays (e.g., BioPlex 2200) .

Current Guidelines

CDC and WHO: FTA-ABS is no longer prioritized due to variability and manual workflow .
Canadian Guidelines: Reserved for CSF testing in suspected neurosyphilis .

Limitations and Considerations

Factor	Impact
Chronic Infections	Persistent positivity limits utility in reinfection cases .
Technical Complexity	Requires fluorescence microscopy and trained personnel .
Cost	Higher per-test cost compared to automated alternatives .

Product Specs

Buffer

Preservative: 0.03% Proclin 300
Constituents: 50% Glycerol, 0.01M PBS, pH 7.4

Form

Liquid

Lead Time

Made-to-order (14-16 weeks)

Synonyms

FTA antibody; At3g59380 antibody; F25L23.240Protein farnesyltransferase/geranylgeranyltransferase type-1 subunit alpha antibody; EC 2.5.1.58 antibody; EC 2.5.1.59 antibody; CAAX farnesyltransferase subunit alpha antibody; FTase-alpha antibody; Ras proteins prenyltransferase subunit alpha antibody; Type I protein geranyl-geranyltransferase subunit alpha antibody; GGTase-I-alpha antibody

Target Names

FTA

Uniprot No.

Q9LX33

Target Background

Function

This antibody targets the essential subunit of both the farnesyltransferase and the geranylgeranyltransferase complex. It plays a crucial role in the transfer of a farnesyl or geranylgeranyl moiety from farnesyl or geranylgeranyl diphosphate to a cysteine residue at the fourth position from the C-terminus of several proteins containing the C-terminal sequence Cys-aliphatic-aliphatic-X.

Gene References Into Functions

PFT exhibits broad specificity for CaaX substrates. PMID: 20565889

Database Links

KEGG: ath:AT3G59380

STRING: 3702.AT3G59380.1

UniGene: At.1520

Protein Families

Protein prenyltransferase subunit alpha family

Q&A

Here’s a structured FAQ for researchers investigating the FTA Antibody (FTA-ABS) in syphilis diagnostics, based on methodological and analytical challenges in academic research:

Sensitivity by Stage (Data from ):

Stage	FTA-ABS Sensitivity	TP-PA Sensitivity
Primary	81–86%	92–96%
Secondary	94–98%	97–99%
Early Latent	90–94%	95–98%

Design implication: For primary syphilis studies, pair FTA-ABS with PCR or dark-field microscopy to offset its lower sensitivity .

What explains contradictory specificity reports for FTA-ABS in the literature?

Reagent variability: Antigen preparation methods (washed vs. non-washed treponemal suspensions) affect nonspecific binding .
Subjective interpretation: Fluorescence intensity grading varies between technicians (κ = 0.65–0.78 in inter-rater studies) .
Solution: Adopt automated fluorescence quantification systems or consensus panels for equivocal samples .

How can researchers optimize FTA-ABS protocols to improve reproducibility?

Reagent standardization:
- Use anti-human IgG conjugates (not IgM/IgA) to reduce cross-reactivity .
- Validate sorbent batches against CDC reference panels .
Automation: Implement microplate-based FTA-ABS to reduce manual variability .

Performance comparison (N=262 syphilis cases, ):

Assay	Sensitivity	Specificity
FTA-ABS	90.8%	98.0%
LIAISON CIA	96.9%	94.5%
Bioplex MBIA	96.9%	96.7%

Trend: Automated immunoassays (e.g., CIA, MBIA) now match or exceed FTA-ABS sensitivity while providing objective, high-throughput results .

How should researchers address FTA-ABS’s declining use in modern diagnostic algorithms?

Historical context: FTA-ABS was a 1970s gold standard but lacks standardized reagents and automation .
Transition strategy: Use FTA-ABS as a secondary test in research to validate novel assays, leveraging its high specificity in late-stage syphilis .

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FTA Antibody