**Exhibit 31.1**

CERTIFICATION

I, Una S. Ryan, certify that:

1.        I have reviewed thisreport on Form 10-Q of AVANT Immunotherapeutics, Inc.;

2.        Based on my knowledge,this report does not contain any untrue statement of a material fact or omit tostate a material fact necessary to make the statements made, in light of thecircumstances under which such statements were made, not misleading withrespect to the period covered by this report;

3.        Based on my knowledge, thefinancial statements, and other financial information included in this report,fairly present in all material respects the financial condition, results ofoperations and cash flows of the registrant as of, and for, the periodspresented in this report;

4.        The registrant’s othercertifying officer and I are responsible for establishing and maintainingdisclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and15d-15(e)) for the registrant and have:

(a)        Designed suchdisclosure controls and procedures, or caused such disclosure controls andprocedures to be designed under our supervision, to ensure that materialinformation relating to the registrant, including its consolidatedsubsidiaries, is made known to us by others within those entities, particularlyduring the period in which this report is being prepared;

(b)       Designed suchinternal control over financial reporting, or caused such internal control overfinancial reporting to be designed under our supervision, to provide reasonableassurance regarding the reliability of financial reporting and the preparationof financial statements for external purposes in accordance with generallyaccepted accounting principles;

(c)        Evaluated theeffectiveness of the registrant’s disclosure controls and procedures andpresented in this report our conclusions about the effectiveness of thedisclosure controls and procedures, as of the end of the period covered by thisreport based on such evaluation; and

(d)       Disclosed inthis report any change in the registrant’s internal control over financialreporting that occurred during the registrant’s most recent fiscal quarter (theregistrant’s fourth fiscal quarter in the case of an annual report) that hasmaterially affected, or is reasonably likely to materially affect, theregistrant’s internal control over financial reporting;

5.        The registrant’s othercertifying officer and I have disclosed, based on our most recent evaluation ofinternal control over financial reporting, to the registrant’s auditors and theaudit committee of the registrant’s board of directors (or persons performingthe equivalent functions):

(a)        Allsignificant deficiencies and material weaknesses in the design or operation ofinternal control over financial reporting which are reasonably likely toadversely affect the registrant’s ability to record, process, summarize andreport financial information; and

(b)        Any fraud, whether or not material, that involvesmanagement or other employees who have a significant role in the registrant’sinternal control over financial reporting.
| Date: November 9, 2006 | By     | /s/ UNA S. RYAN                       |
|-----------------------------|--------|---------------------------------------|
|                        | Name:  | Una S. Ryan, Ph.D.                    |
|                        | Title: | President and Chief Executive Officer |

 

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