To develop a non-human primate model of LACV infection for pathogenesis studies and for testing of future vaccine candidates, rhesus monkeys were inoculated with 10 5 PFU of biologically cloned (terminally diluted) human or mosquito LACV (LACV/human/1978-clone, LACV/mosquito/1978-clone). Illness was not observed following virus administration, and virus was not detected at any time in serum samples ( Table 2 ). Virus was present at a low titer in lymph nodes on days 6, 8, and 12, however, virus replication in these tissues could not be identified by IHC staining. Despite the low level (or absence) of viremias and highly restricted replication in the tissues sampled, all monkeys developed neutralizing antibody responses that were first detected on days 6-8 indicating that the each monkey was infected. Twenty-eight days after inoculation, neutralizing antibody titers (PRNT 60 ) for each group were in the range of 1:560 -1:2186 (Table  2) . Low-level cross-reactive antibodies were present in two monkeys (CL6E and DBOH) at the start of the experi-ment. A boost in antibody titer in these monkeys was not observed compared to other monkeys, suggesting that this experimental LACV infection was a primary infection.