(Reuters) -Proxy advisory firm Institutional Shareholder Services (ISS) on Friday backed only one of Carl Icahn's three nominees to Illumina Inc (NASDAQ: ILMN )'s board, saying that the activist investor's push to remove the company's CEO was too disruptive. ISS backed Icahn's candidate Andrew Teno and said he could be an adequate replacement for Illumina Chairman John Thompson, but did not support any other Icahn nominee. The partial backing by ISS comes just two days after another proxy adviser, Glass Lewis, backed Teno and another Icahn nominee, and said shareholders should vote against the re-election of current CEO Francis deSouza and Chairman Thompson. Illumina, which specializes in gene sequencing, and Icahn have been locked in a months-long proxy battle, where Icahn has been looking to remove deSouza and Thompson from the company's board and criticized Illumina's deal to buy cancer test maker Grail.