In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Differential impact of immune escape mutations G145R and P120T on the replication of lamivudine - resistant hepatitis B virus e antigen - positive and - negative strains .
### Output Text:
Differential impact of immune escape mutations G145R and P120T on the replication of <span class="chemical">lamivudine</span> - resistant <span class="chemical">hepatitis B virus e antigen</span> - positive and - negative strains . 