Safety and immunogenicity of a mutagenized, live attenuated Rift Valley fever vaccine, MP-12, in a Phase 1 dose escalation and route comparison study in humans.

Rift Valley fever (RVF) poses a risk as a potential agent in bioterrorism or agroterrorism. A live attenuated RVF vaccine (RVF MP-12) has been shown to be safe and protective in animals and showed promise in two initial clinical trials. In the present study, healthy adult human volunteers (N=56) received a single injection of (a) RVF MP-12, administered subcutaneously (SQ) at a concentration of 10(4.7) plaque-forming units (pfu) (SQ Group); (b) RVF MP-12, administered intramuscularly (IM) at 10(3.4)pfu (IM Group 1); (c) RVF MP-12, administered IM at 10(4.4)pfu (IM Group 2); or (d) saline (Placebo Group). The vaccine was well tolerated by volunteers in all dose and route groups. Infrequent and minor adverse events were seen among recipients of both placebo and RVF MP-12. One subject had viremia detectable by direct plaque assay, and six subjects from IM Group 2 had transient low-titer viremia detectable only by nucleic acid amplification. Of the 43 vaccine recipients, 40 (93%) achieved neutralizing antibodies (measured as an 80% plaque reduction neutralization titer [PRNT80]) as well as RVF-specific IgM and IgG. The highest peak geometric mean PRNT80 titers were observed in IM Group 2. Of 34 RVF MP-12 recipients available for testing 1 year following inoculation, 28 (82%) remained seropositive (PRNT80≥1:20); this included 20 of 23 vaccinees (87%) from IM Group 2. The live attenuated RVF MP-12 vaccine was safe and immunogenic at the doses and routes studied. Given the need for an effective vaccine against RVF virus, further evaluation in humans is warranted.

Short report: Isolation and identification of Venezuelan equine encephalitis virus from a human in Panama.

Venezuelan equine encephalitis (VEE) virus was isolated from a febrile human in Panama. The patient became febrile approximately 10 days after returning from Gatun Lake in Panama. The virus was isolated from the acute phase serum and identified as VEE, subtype ID virus by monoclonal antibodies, and was confirmed by cross plaque-reduction neutralization tests.

An outbreak of West Nile virus in a New York City captive wildlife population.

An outbreak of West Nile virus (WNV) in and around New York City during the late summer of 1999 was the cause of extensive mortality among free-ranging birds. Within the Bronx Zoo/Wildlife Conservation Park, viral activity was also observed and produced some morbidity and mortality among specimens in the zoo's bird collection and probably caused morbidity in at least one specimen from the zoo's mammal collection. To determine the extent of the outbreak and attempt to ascertain the temporal appearance of virus within the park, a serologic survey of birds and mammals was performed. The survey showed that 34% of tested birds (125 of 368; 124 species) were positive for antibody to WNV. The virus caused a disease to infection ratio of 22% (27 of 125) among birds with a 70% (19 of 27) case fatality rate. In contrast, only 8% of the mammals (9 of 117; 35 species) possessed antibody to WNV and there was no virus-associated mortality. Testing of banked and fresh sera obtained from both birds and mammals revealed that there was no evidence of WNV circulation before the 1999 outbreak and that birds introduced into the park were not the source of the New York outbreak. West Nile virus RNA was detected in tissues from one bird that died in February 2000, long after the end of the mosquito transmission season. The potential importance of zoologic parks as possible sentinels for emerging diseases is discussed.

Department of Defense West Nile virus surveillance in 2002.

The Department of Defense (DoD) has engaged in West Nile virus (WNV) surveillance and response since 1999. In 2002, the three Services continued their cooperative, multidisciplinary approach to the WNV outbreak. Activities included a doubling of mosquito surveillance and vector control responses, extension of and doubling of bird and nonhuman mammal surveillance to all four continental United States regions, expanded diagnostic testing by DoD laboratories, and installation environmental clean up and personnel protection campaigns. Medical treatment facilities conducted passive surveillance and reported possible cases in DoD health care beneficiaries. Efforts were coordinated through active communication within installations, with commands, and with surrounding communities. Undertaken activities complemented each other to maximize surveillance coverage. The surveillance detected WNV on 44 DoD installations. It led directly to vector control and prevention activities, and there were no confirmed cases of WNV reported in the DoD force. This multi-Service effort is a surveillance template for future outbreaks that threaten DoD force health.

Immune interference after sequential alphavirus vaccine vaccinations.

We compared the effect of order of administration of investigational alphavirus vaccines on neutralizing antibody response. Volunteers who received the inactivated eastern and western equine encephalitis (EEE and WEE) vaccines before live attenuated Venezuelan (VEE) vaccine had significantly lower rates of antibody response than those receiving VEE vaccine before EEE and WEE vaccines (66.7% vs. 80.6%; p=0.026). The odds of having a VEE antibody non-response among those initially receiving EEE and WEE vaccines, adjusted for gender, were significant (odds ratio [OR]=2.20; 95% CI=1.2-4.1 [p=0.0145]) as were the odds of non-response among females adjusted for group (OR=1.81; 95% CI=1.2-2.7 [p=0.0037]). Antibody interference and gender effect have major implications for vaccine strategy among those receiving multiple alphavirus vaccines and those developing next generation vaccines for these threats.

Antibody response to a delayed booster dose of anthrax vaccine and botulinum toxoid.

We evaluated the prevalence and concentration of serum antibodies 18-24 months after primary inoculation with anthrax and botulinum vaccines, and assessed the reactogenicity and immunogenicity of a significantly delayed booster dose of these vaccines. Five hundred and eight male active-duty military personnel received one, two or three inoculations with anthrax vaccine and/or botulinum toxoid in 1990/1991 in preparation for Operations Desert Shield/Desert Storm. Subjects were vaccinated with the licensed anthrax vaccine, adsorbed (AVA) and pentavalent (ABCDE) botulinum toxoid (PBT) BB-IND 3723. Anthrax protective antigen (PA) IgG antibody was measured in serum using an immunocapture enzyme-linked immunosorbent assay (ELISA). A mouse neutralization test was used to determine the titer of Clostridium botulinum type A antitoxin in serum samples. The prevalence of anti-PA IgG was 30% in individuals 18-24 months after priming with one, two or three doses of AVA. After boosting, 99% of volunteers had detectable anti-PA IgG; only two individuals failed to respond. The prevalence of antibodies against botulinum toxin type A was 28% 18-24 months after initial priming. Following boosting, 99% of volunteers had serum titers >0.02IU/ml, and 97% responded with titers > or =0.25IU/ml. Systemic reactions to booster vaccinations could not be specifically ascribed to one or the other vaccine, but were generally mild and of brief duration. Forty-five percent of volunteers reported one or more systemic reactions over the course of 7 days. Injection site reactions of any kind occurred in 25% of AVA recipients and in 16% of PBT recipients; persistence of local reactions beyond 7 days was infrequent. While the kinetics and durability of immune responses must be studied, these findings suggest that booster doses of anthrax vaccine and botulinum toxoid sufficient to stimulate a robust anamnestic response may be given at times distant from receipt of the primary inoculations.