Amplification of Herpes simplex type 1 and Human Herpes type 5 viral DNA from formalin-fixed Alzheimer brain tissue

It is known that nucleic acids from formalin-fixed tissues are not nearly as good templates for DNA amplification as those extracted from fresh tissues. However, specimens stored in most pathologic archives are initially fixed in formalin. The possibility of an infectious etiology of several diseases including Alzheimer's underscores the usefulness of archived tissue in assessing the association of infectious agents with specific pathology. In this report, we describe in detail a method resulting in robust amplification of HSV1 and Human Herpes type (HHV) 5 viral DNA targets using formalin-fixed Alzheimer brain frontal and temporal tissue as source of amplification template. Herpes simplex type 2 viral DNA was not detected in the limited samples examined in this study. Amplicons were verified by sequence analysis. Brain tissue stored in formalin longer than 1 year prior to post-formalin-fixation analysis gave rise to significantly shorter amplicons consistent with the observation that template DNA integrity decreases significantly with increasing time of storage in formalin. Thus, this report should be useful in PCR-based investigations assessing the regional presence of viral DNAs in formalin-fixed brain tissue.