Shares of Cel-Sci Corp., the little Vienna biotech company with the stock symbol HIV, jumped 81 percent last week, and under head-spinning circumstances.

On Wednesday, the Public Relations Newswire had an announcement from a lawyer in Argentina who said his client, a company in the British West Indies, was making an unsolicited buyout offer for Cel-Sci of $124 million, or $7.75 a share.

The stock quickly jumped to $3 a share from less than $2 a share, only to slip back Thursday after Cel-Sci said it hadn't been able to contact the lawyer and couldn't tell whether the offer was genuine.

On Friday there was another press release from the lawyer insisting that his client, identified only as Cel-Sci Acquisition Corp., was indeed interested in a friendly takeover. The stock rose again, to $3.50 a share, but there still was no answer to the question of who was making the offer and if it is, in fact, legitimate.

The motivation for the other big moves by Washington stocks last weeks was easier to assess.

Shares of Allied Research Corp. of Vienna jumped to $6.25 from $4.75 after the company's subsidiary in Belgium, Mecar SA, won an $18 million contract for munitions. Chairman J.R. Sculley said Allied, which makes tank and artillery shells overseas, has received $71 million in new orders since June.

Another new contract added more than $1.50 a share to the stock of LCC International Inc. of McLean. LCC, which designs and installs radio and cellular phone antenna systems, got a $115 million contract from XM Satellite Radio Inc. of Washington.

XM Satellite is building a nationwide radio system that will broadcast directly from satellites to cars and homes. Because mountains and tall buildings can block the satellite signal, XM needs a network of repeater stations on the grounds. That's what LCC will build.

After four down weeks in a row, The Washington Post-Bloomberg regional stock index rebounded slightly. The index, which represents stocks of more than 200 companies in the District, Maryland and Virginia, was up a little more than half a percentage point to 170.09, but it still is well short of its high point for the year of 178.82, set July 16.