Vaccine candidates for dengue virus type 1 (DEN1) generated by replacement of the structural genes of rDEN4 and rDEN4Δ30 with those of DEN1

Table 3 Replication and immunogenicity of rDEN1/4 chimeric viruses in rhesus monkeys.

Virus¹	No. of monkeys	% of monkeys with viremia	Mean no. of viremic days per monkey	Mean peak virus titer² (log₁₀ PFU/ml ± SE)	Geometric mean serum neutralizing antibody titer (reciprocal dilution)³			Post-challenge⁵
					Day 0	Day 28	% sero-conversion⁴	% of monkeys with viremia	Mean peak virus titer² (log₁₀ PFU/ml ± SE)
DEN1 Puerto Rico/94	4	100	2.8	2.0 ± 0.1	< 5	103	100	0	< 1.0
rDEN1/4 (CME)	4	100	2.0	1.5 ± 0.1	< 5	56	100	0	< 1.0
rDEN1/4Δ30 (CME)	4	50	0.5	1.1 ± 0.1	< 5	< 5	0	75	1.7 ± 0.3
rDEN1/4 (ME)	4	100	4.0	2.1 ± 0.1	< 5	65	100	0	< 1.0
rDEN1/4Δ30 (ME)	6	50	0.7	1.1 ± 0.2	< 5	23	66	0	< 1.0
Mock infected	2	0	0	< 1.0	< 5	< 5	0	100	2.1 ± 0.2

¹ Groups of rhesus monkeys were inoculated subcutaneously on day 0 with 5.0 log₁₀ PFU of the indicated virus in a 1 ml dose. Serum was collected daily for 10 days to detect viremia and on day 28 for determination of neutralizing antibodies.
² Virus titer in serum was determined by plaque assay in Vero cells.
³ Plaque reduction (60%) neutralizing antibody titers were determined using DEN1 Puerto Rico/94 as test virus.
⁴ Percentage of monkeys with a four-fold or greater rise in neutralizing antibody levels between day 0 and 28.
⁵ Monkeys were challenged after 35 days with DEN1 (Puerto Rico/94) administered subcutaneously in a 1 ml dose containing 5.0 log₁₀ PFU. Serum was collected daily for 10 days to detect viremia.

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