Could you try fusion to something like the FH8 tag?

Several good papers from Costa et al. in Portugal, well worth reading and seems to have decent performance in a variety of systems.

Best of luck,  Robin

i.e. - the paper where they use the tag to improve immunogenicity :

http://dx.doi.org/10.4161/bioe.26003

Conjugating the peptide to a highly antigenic carrier protein such as keyhole limpet hemocyanin is a method that is used to increase the antigenicity of a peptide.

I would like to express my opinion.   A researcher has previously made an IgG against fucoidan using limpet hemocyanin (please see file; Tokita ELISA), but the result of the fucoidan transport is miserable (please see file; ELISA Fucoidan) as compared to the reliable and true HPLC method (please see file; SEC Fucoidan determination). 

Thus, protein binding assay such as ELISA is neither reliable nor sensitive at all.

Then, protein binding assay always gives sad results, and DNA sequence or amino acid sequence may not be important in the binding reaction.

Therefore, I recommend another method than immunology to reliably apply for the binding reactions, since binding reaction seems to be also ruled by glyco-chains of eucaryotic glycoproteins.   Such a binding reaction of biotin to avidin (glycoprotein of hen's egg white) is resistant to trypsin treatment (please see file; Netherlands Biotin).   Binding reaction may be detectable by using HPLC analysis, since binding and/or affinity reaction can also be detectable in the HPLC method.  

Added on 17 September 2017

I have recently expressed about notorious ELISA issue.

The differences in determination values of fucoidan between HPLC-photometric method and ELISA method have been occurred recently (please see files to compare; SEC fucoidan determination and ELISA fucoidan).

The determined value of fucoidan (Okinawa-fucan) is c.a. 2,000-fold higher in the HPLC-photometric analysis as compared to notorious ELISA method (our experience together with Dr. Takeaki Nagamine, M.D., Graduate School of Health Sciences, Gunma University, Showa-machi, Maebashi, Gunma, Japan).   Dr. Tajeaki Nagamine has miserably thrown away the fucoidan-assay kit of ELISA when he is retiring from the University (my unpublished observation or experience).

(1) Direct photometric assay without purification gives only 50% value as compared to HPLC-photometric assay due to violence to Lambert-Beer's law (please see Fig. 10 of file "SEC fucoidan determination" again). 

(2) Further, binding protein is not so specific; i.e., avidin binds biotin (vitamin H), lipoic acid (thioctic acid), and amino acids, and binding is stronger to lipoic acid than biotin (please see file; Thioctic acid determination) .   Then, biotin assay by using avidin is very difficult since serum has 10-fold higher concentration of lipoic acid than biotin; i.e., lipoic acid may interfere the biotin binding reaction of avidin.   Similarly, binding protein of IgG seems to have a broad binding specificity. 

(3) Furthermore, specificity of binding protein increases 10-fold by homo-dimerization(please see file; The Fascio effect).   The specificity of IgG seems to be 100-fold lower than pentamer IgM due to the Fascio effect.

Then, 2 (1) x 10 (2) x 100 (3) = 2000-fold difference seems to be occurred between HPLC-photometric method and ELISA method.   Therefore, ELISA is not quantitative and not sensitive; i.e., it gives only false value at ng/mL.

Further, similar differences in determination value of biotin have also been occurred between HPLC-photometric method and binding assay method; i.e., such a biotin assay as has been reported; i.e., "Anal Biochem. 1986 Apr;154(1):367-70. A sensitive enzyme assay for biotin, avidin, and streptavidin, Edward A. Bayer, Haya Ben-Hur, Meir Wilchek, Department of Biophysics, The Weizmann Institute of Science, Rehovot 76100, Israel, Abstract; Reciprocal enzyme assays are described for the vitamin biotin and for the biotin-binding proteins avidin and streptavidin. The assays are based on the following steps: (a) biotinylated bovine serum albumin is adsorbed onto microtiter plates; (b) streptavidin (or avidin) is bound to the biotincoated plates: (c) biotinylated enzyme (in this case alkaline phosphatase) is then interacted with the free biotin-binding sites on the immobilized protein. For biotin assay, competition between the free vitamin and the biotinylated enzyme is carried out between steps (b) and (c). The method takes advantage of the four biotin-binding sites which characterize both avidin and streptavidin. The method is extremely versatile and accurate over a concentration range exceeding three orders of magnitude. The lower limits of detection are approximately 2 pg/ml (0.2 pg/sample) for biotin and less than 100 ng/ml (10 ng/sample) for either avidin or streptavidin."   However, this method also gives only a false value with detection limit as 0.2 pg of biotin.   This detection limit is not true since linear regression line is not obtained in any of the binding assays.

True HPLC-biotin determination method is presented in the file (Netherlands biotin).   HPLC-photometric detection method gives a true value with detection limit 17 pg of biotin.   This detection limit is true since linear regression line inserting to zero point is obtained in HPLC-photometric detection method.  

If your peptide/protein sequence is homologous to the sequence of the protein in the host animal, immunogenicity is usually negligible.

You can change the AAs that are not critical for binding by AAs with greater Antigenicity Index.