Michael A. Feaster, who was believed to be the first person in the nation to be charged with assault with a dangerous weapon for having sex while infected with the AIDS virus, was sentenced on related charges here yesterday to 98 to 295 years in prison.

Feaster was acquitted in D.C. Superior Court of the charges of assault with the deadly virus, but was convicted by a jury in July of 26 counts of sodomy, indecent acts on a minor and enticing a minor. The charges involved six boys ranging in age from 9 to 15.

The sentence, imposed by Judge Ricardo M. Urbina, was believed to be one of the most severe handed down in the District.

The U.S. Attorney's Office said last night that Feaster "gained the confidence of vulnerable, often crack-addicted women and persuaded them to relinquish the care of their sons to him."

Feaster "used the boys for his own sexual purposes," according to a statement issued by the prosecutor's office. He "sodomized some of them and forced others to perform sexual acts on him."

Authorities said the incidents occurred in a house at 10th and K streets NE where Feaster lived.

U.S. Attorney Jay B. Stephens said in an interview last night that he believed the sentence "recognizes the defendant's outrageous victimization of these vulnerable children."

Stephens said the term appears to take account of "how the defendant preyed upon {his} victims, utilized his . . . special relationship to them . . . {and} their vulnerable quality."

He said he believed that the sentence also took into consideration Feaster's "knowledge of his own condition" in carrying the AIDS virus, and his "acting in deliberate disregard despite that knowledge."

In a statement, the prosecutor's office said Feaster tested positive in 1987 for the virus that causes AIDS and had been warned against engaging in sexual intercourse of any kind.

Urbina acquitted Feaster of the charge of assault with the AIDS virus on a motion from the defense. The judge ruled that the prosecution had failed to prove that the virus was transferred to any of the victims.