I would think that initials would stand for United States Licensed Pratical Nurse

see below:

Licensed Practical Nurses may be granted selected nursing credits WITHOUT taking challenge examinations. Guidelines provided by the Association and adopted by the Department of Nursing and Public Administration of Marywood University apply.

The L.P.N. must complete an individual evaluation by the Nursing Department Chairperson. At this meeting the L.P.N. must provide evidence of

a current U.S. L.P.N. license,