Differentiation of HPV-containing cells using organotypic "raft" culture or methylcellulose.

The study of human papillomaviruses (HPVs) has been challenging due to the differentiation-dependent aspects of their productive life cycles. The use of HPV virions, isolated from tissues, to study viral pathogenesis has been complicated due to the low numbers of HPV virions synthesized and inefficient infection of cells in tissue culture. As an alternative approach, genetic methods have been developed to study the papillomavirus life cycle in its natural host, human keratinocytes. Techniques have been developed to transfect keratinocytes with cloned HPV DNA and to isolate cell lines that maintain viral DNA as extra-chromosomal elements. Since the productive phase of the HPV life cycle is dependent on differentiation, in vitro tissue-culture models have also been used to recapitulate epithelial differentiation. Differentiation in organotypic raft cultures as well as upon suspension in semi-solid media have been used to study both early and late stages of the viral life cycle.