Hepatitis E virus DNA vaccine elicits immunologic memory in mice.

Injection of an expression vector pJHEV containing hepatitis E virus (HEV) structural protein open reading frame 2 gene generates a strong antibody response in BALB/c mice that can bind to and agglutinate HEV. In this study, we tested for immunologic memory in immunized mice whose current levels of IgG to HEV were low or undetectable despite 3 doses of HEV DNA vaccine 18 months earlier. Mice previously vaccinated with vector alone were controls. All mice were administered a dose of HEV DNA vaccine to simulate an infectious challenge with HEV. The endpoint was IgG to HEV determined by ELISA. Ten days after the vaccine dose, 5 of 9 mice previously immunized with HEV DNA vaccine had a slight increase in IgG to HEV. By 40 days after the vaccine dose, the level of IgG to HEV had increased dramatically in all 9 mice (108-fold increase in geometric mean titer). In contrast, no control mice became seropositive. These results indicate that mice vaccinated with 3 doses of HEV DNA vaccine retain immunologic memory. In response to a small antigenic challenge delivered as DNA, possibly less than delivered by a human infective dose of virus, mice with memory were able to generate high levels of antibody in less time than the usual incubation period of hepatitis E. We speculate that this type of response could protect a human from overt disease.

TT virus infection in acute non-A to E hepatitis in northern Thailand.

TT virus is a novel DNA virus widely distributed in the general population. We examined the prevalence of TTV infection in a population with acute non-A to E hepatitis and in comparison groups located in Northern Thailand. The prevalence of TTV in subjects with non-A-E hepatitis was 19% (21/112), 6% (4/72) in healthy volunteers, 17% (12/72) in those with hepatitis A or B, and 17% (8/48) in hospitalized patients with non-hepatitis illnesses. A significant association with TTV infection and non-A-E hepatitis was seen in all groups (OR 3.9, p = 0.02) and in children (OR 25.8, p = 0.001). Among subjects with non-A-E hepatitis, TTV was associated with higher alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels (significant for AST, p = 0.02). Our observations suggest that TTV in our study population may be associated with non-A-E hepatitis and that children in particular may be at risk of hepatocellular injury as a result of TTV infection.

An accelerated schedule for tick-borne encephalitis vaccine: the American Military experience in Bosnia.

Tick-borne encephalitis (TBE) is a viral illness endemic to the Balkan region. United States military forces were deployed to Bosnia in early 1996 as part of Operation Joint Endeavor, a U.S.-led multinational peace-keeping operation. To counteract the TBE threat, an inactivated, parenteral vaccine (FSME-Immun Inject; Immuno AG, Vienna, Austria) was offered to soldiers at high risk on a volunteer basis in an accelerated, 3-dose schedule (0, 7, and 28 days). Passive adverse reaction surveillance was conducted on 3,981 vaccinated personnel. Paired sera from a randomly selected group of 1,913 deployed personnel (954 who received vaccine and 959 who were unvaccinated) were tested for antibodies to TBE by an ELISA. Three-dose recipients demonstrated an 80% seroconversion rate (4-fold or greater increase in anti-TBE titers). By comparison, the TBE infection rate in the unvaccinated cohort was found to be only 0.42% (4 of 959). Only 0.18% of vaccinees reported self-limited symptoms. An accelerated immunization schedule appears to be an acceptable option for military personnel or travelers on short-term notice to TBE-endemic areas.

Deployed US Army soldiers' knowledge and use of personal protection measures to prevent arthropod-related casualties.

The recommendation to use personal protection measures (PPMs) to prevent arthropod-related diseases and nuisance bites is a common element of travel medicine consultation.1-3 Prevention of arthropod-related casualties is especially important to the military, given the often intense exposure of service members to biting arthropods and the threat of personnel losses to mission success. In the 1980s, 75% deet (N,N-diethyl-m-toluamide) was the US military-issue insect repellent for use on skin and clothing. Collaboration between military and civilian researchers led to the implementation in 1991 of the current US military system of PPMs which has three components: topical application of 33% extended-duration deet, treatment of field uniforms with permethrin, and proper wearing of field uniforms.4-6 Compared to military-issue 75% topical deet, 33% extended-duration deet prevents bites up to three times longer (as long as 12 hours), is less greasy, and has lower plasticizing properties. Field uniforms treated with the contact toxicant, permethrin, are also necessary to minimize bites from crawling arthropods such as ticks and chiggers. Implementation of all three components of this system is a safe and effective means of reducing the threat posed by biting arthropods.7 We conducted a questionnaire survey to assess the degree of deployed soldiers' knowledge of the US military's system of PPMs and use of PPMs in general. Survey results may promote the development of better ways to advise and teach military and civilian travelers about the proper use of PPMs given the multitude of available products and practices.

Use of azithromycin for the treatment of Campylobacter enteritis in travelers to Thailand, an area where ciprofloxacin resistance is prevalent.

We evaluated the use of azithromycin (500 mg) or ciprofloxacin (500 mg) daily for 3 days for the treatment of acute diarrhea among United States military personnel in Thailand. Stool cultures were obtained and symptoms were recorded on study days 0, 1, 2, 3, and 10. Campylobacter species were the most common pathogen isolated (44 isolates from 42 patients). All Campylobacter isolates were susceptible to azithromycin; 22 were resistant to ciprofloxacin. Among the 42 patients with campylobacter infection, there were 2 clinical and 6 bacteriologic treatment failures in the ciprofloxacin group and no treatment failures in the azithromycin group (P = .021 for bacteriologic failures). Overall, azithromycin was as effective as ciprofloxacin in decreasing the duration of illness (36.9 hours vs. 38.2 hours, respectively) and the number of stools (6.4 vs. 7.8, respectively). Among those not infected with Campylobacter species (n = 30), the duration of illness was 32.9 hours vs. 20.7 hours (P = .03) for the azithromycin and ciprofloxacin groups, respectively. Azithromycin is superior to ciprofloxacin in decreasing the excretion of Campylobacter species and as effective as ciprofloxacin in shortening the duration of illness. Azithromycin therapy may be an effective alternative to ciprofloxacin therapy in areas where ciprofloxacin-resistant Campylobacter species are prevalent.

Experimental human gonococcal urethritis: 250 Neisseria gonorrhoeae MS11mkC are infective.

Neisseria gonorrhoeae MS11mkA (mkA) expresses one 3.6-kDa lipooligosaccharide (LOS). Variant MS11mkC (mkC), expressing four larger LOSs, occurs in vitro among mkA at a frequency of 10(-3). Infectivity of these variants was compared in 2 groups of volunteers inoculated with approximately 40,000 piliated, Opa- gonococci of either strain. The mkC variant infected 5 of 5 while mkA infected only 2 (40%) of 5. Gonococci recovered from the mkA infections showed a transition toward the mkC LOS phenotype. The mkA inoculum contained approximately 40 mkC gonococci. These data confirmed earlier studies and suggested that small numbers of mkC gonococci would be infective. This hypothesis was tested in three more experiments. In two, volunteers were inoculated with 250 or 1250 mkC, infecting 3 of 7 in each group, and in the third, 1600 mkC infected 2 of 6, resulting in a total of 8 of 20 infected by < or = 1600 mkC. Gonococci shed by infected volunteers maintained the mkC LOS phenotype but shifted from Opa- to Opa+. Thus, LOS and opacity protein, as well as pilus, are gonococcal virulence factors.

Inflammatory cytokines produced in response to experimental human gonorrhea.

Inflammatory cytokine production in men was examined after intraurethral challenge of volunteers with Neisseria gonorrhoeae MS11mkA or MS11mkC. Increased interleukin (IL)-8, IL-6, and tumor necrosis factor-alpha (TNF-alpha) were detected in urine before the onset of symptoms and peaked simultaneously with the detection of IL-1 beta at the onset of symptoms. Urine cytokine levels returned to baseline or near baseline within 48 h after antibiotic therapy. In plasma, IL-8, TNF-alpha, IL-1 beta, and IL-6 were elevated at the onset of symptoms in 9, 5, 4, and 3 of 10 subjects, respectively, and returned to near normal within 48 h after treatment. IL-1 alpha and granulocyte-macrophage colony-stimulating factor were not consistently detected in urine or plasma after challenge. Cytokine mRNA transcripts in peripheral blood mononuclear cells were not altered by the infection. The findings suggest that IL-8, IL-6, and possibly TNF-alpha were produced at the local site of infection, whereas IL-1 beta was derived from infiltrating leukocytes.

Azithromycin prophylaxis against a chloroquine-resistant strain of Plasmodium falciparum.

Azithromycin has antimalarial activity and favourable pharmacokinetic properties for a prophylactic antimalarial agent. We investigated the ability of azithromycin to prevent malaria in volunteers infected with a chloroquine-resistant strain of Plasmodium falciparum. 4 volunteers received oral azithromycin 500 mg followed by 250 mg daily for 7 further days. Subjects were infected on the third day of azithromycin. 3 subjects were protected compared with none of 15 controls. The volunteer not protected by azithromycin had unquantifiable plasma levels of azithromycin, probably because of poor absorption. Azithromycin could be a promising prophylactic agent for P falciparum malaria.

Safety and immunogenicity of the oral, whole cell/recombinant B subunit cholera vaccine in North American volunteers.

A newly formulated, oral, inactivated whole cell plus recombinant B subunit (WC/rBS) cholera vaccine was evaluated in US military personnel. In the first study, 74 subjects were given two doses 14 days apart. In the second study, 186 subjects were randomized into four groups; two groups received vaccine with either full (4 g) or half (2 g) strength bicarbonate buffer, and two groups received either full or half strength buffer without vaccine. Mild gastrointestinal symptoms were associated with full buffer (P = .02) but not with the vaccine. In the first study, 36% of all subjects and 55% with low prevaccination titers (< 1:40) had a > or = 2-fold rise in vibriocidal antibody level; > 80% of subjects developed a 4-fold rise in anti-cholera toxin (CT) titers. Post-vaccination IgA and IgG anti-CT titers were approximately 1.5-fold higher among persons receiving full strength buffer (P = .05). The WC/rBS vaccine is safe and immunogenic in North Americans, although some mild gastrointestinal symptoms occur with the high concentration of buffer necessary to protect the B subunit from gastric acid denaturation. Prior immunity to cholera conferred by parenteral vaccine decreased vibriocidal antibody response.