The present decision explores the limits of what can be said to be disclosed in an A 54(3) document.
The appeal was filed by the opponent after the Opposition Division (OD) had maintained the patent in amended form. Independent claim 4 of the request before the Board read:
A process for preparing a human-antibody library, which comprises mRNA being isolated from nonactivated peripheral human B-lymphocytes and being transcribed into cDNA, subsequently amplifying the cDNA coding for antibodies by PCR by means of suitable primers, then carrying out an incorporation into suitable expression plasmids and finally expressing the antibody cDNA in individual clones, and wherein only the variable regions are amplified in each case by the primers used, the expression plasmids do not code for any constant domains of an antibody, and wherein the design of the primer used for the reverse reaction for the synthesis of the noncoding strand of the DNA of the heavy chains is based on IgM sequences.
The Board confirmed the finding of the OD that this claim was novel over document D1:
*** Translation of the German original ***
[1] In the impugned interlocutory decision the OD established that document D1 did not disclose the process according to claim 4 because the document did not contain an unambiguous reference to IgM-specific primers. The reference in document D1 to a publication by Larrick et al filed as document D11 during the opposition proceedings was only made in the context of the location of the primers and not in the context of the selection of a primer that was specific for a particular immunoglobulin isotype […], as the opponent had asserted.
[2] There is no doubt that document D1 is [to be] considered as prior art pursuant to A 54(3)(4) EPC 1973, the content of which is only to be considered for the assessment of novelty. As far as novelty is concerned, the only question to be decided in the appeal proceedings is whether document D1 directly and unambiguously discloses a process having all the features of claim 4 to an average skilled person.
[3] Document D1 discloses a process wherein sequences which encode at least part of the variable domain of the heavy chain of immunoglobulin molecules are amplified by PCR (see column 8, lines 7 to 38) and used for establishing expression libraries. Molecules having particular binding properties can then be isolated from these libraries (see column 16, lines 5 to 8).
[4] The [opponent] has not contested that document D1 did not expressly disclose the feature of the process of claim 4 according to which the design of the PCR primer used for the reverse reaction for the synthesis of the noncoding strand of the DNA of the heavy chains is based on IgM sequences […]. However, the [opponent] pointed out that this feature could be derived directly and unambiguously from the reference to the content of the publication of Larrick et al (document D11 in the present proceedings) in column 14, lines 21-25 of document D1.
[5] [The Board] cannot endorse this argument. The passage of document D1 on which the [opponent] relies reads:
The Board cannot see any clear reference to a particular part of document D11 which directly and unambiguously discloses the feature under consideration to an average skilled person. In particular, the Board cannot see any direct reference to figure 1 or Table 1B od document D11, let alone the IgM specific primer described in Table 1B. The indication of references in the above cited passage merely concerns the proposed location (“… may be located …”) of the primers used for cloning the variable domain of the heavy chain. Therefore, a skilled reader, even if he had become aware of the specific primer in Table 1B of document D11 would not have considered relevant that this was an IgM specific primer. Under these circumstances the Board is of the opinion that the combination of this particular feature with the teaching of document D1 would not impose itself on the skilled person (see T 291/85).
[6] Therefore, the Board comes to the conclusion that at least one feature of the process according to claim 4, i.e. that the design of the primer used for the PCR reaction is based on IgM sequences, is not directly and unambiguously disclosed to the skilled person in document D1. As a consequence, the subject-matter of claim 4 is to be considered novel within the meaning of A 54.
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