Cloning full-length dengue type 4 viral DNA sequences: analysis of genes coding for structural proteins

DNA sequences (approximately 11,000 nucleotides) representing the full-length genome of the dengue virus type 4 were cloned. The sequence of the first 2,429 nucleotides at the 5' terminus which includes the coding region for the structural proteins is presented. The virion structural proteins are encoded in one long open reading frame specifying a polyprotein precursor which is apparently proteolytically cleaved by a mechanism resembling that proposed for expression of structural proteins of other flaviviruses such as yellow fever (YF) and West Nile (WN) viruses. The N terminus for each of the dengue virus structural proteins was tentatively assigned by homology alignment to the corresponding sequence of YF or WN virus. Comparison of sequence homology of structural proteins suggests that dengue virus is more closely related to WN virus than to YF virus or Murray Valley encephalitis virus. Finally, analysis of the extreme 5'- and 3'-terminal nucleotides of the dengue virus genome revealed sequences that may be involved in transcription, replication, and packaging of viral RNA.

Cytochemical and ultrastructural studies of the Langerhans' cells. Sequential observations in experimental contact allergic reaction

In the guinea pig, experimental allergic contact dermatitis (ACD) and primary irritant contact dermatitis (PICD) were induced with different concentrations of dinitrochlorobenzene (DNCB). The epidermal Langerhans' cells (LCs) were observed sequentially by both adenosine triphosphatase (ATPase) and electron microscopy. Light microscopically, in ACD, the density and dendritic processes of LC decreased markedly within 12 h after antigen challenge. Almost no recognization LCs could be seen within 2 to 5 days. Later, LCs began to repopulate in the epidermis. Within 14 days, the density and shape of the LCs returned to normal. On the contrary, LCs changed more rapidly in PICD. The dendritic processes of LC decreased within 2 h and cell density decreased dramatically within 6 h after DNCB application. LCs also repopulated more rapidly in the epidermis. Electron microscopically, in ACD, we observed that lymphocyte-like cells apposed to LCs; LCs were activated and damaged; however, in PICD, we found neither the apposition of lymphocyte-like cells to LCs, nor the activation of LCs. LCs play an important role in the convalescence phase as well as in the early and later phases of contact allergic reaction.