Application of transdermal patches with new skin test reagents for detection of latent tuberculosis.

Introduction. Current intradermal tuberculin skin tests for latent tuberculosis infection (LTBI) based on purified protein derivative (PPD) have poor specificity.Aims. Developing a better skin test antigen as well as a simple skin patch test may improve and facilitate diagnostic performance.Methodology. Defined recombinant antigens that were unique to Mycobacterium tuberculosis (MTB), including two potential latency-associated antigens (ESAT-6 and Rv2653c) and five DosR-encoded latency proteins (Rv1996, Rv2031c, Rv2032, DevR and Rv3716c), were used as diagnostic skin test reagents in comparison with a standard PPD. The performance of the skin tests based on the detection of delayed-type hypersensitivity (DTH) reaction in guinea pigs sensitized to MTB and M. bovis bacille Calmette-Guérin (BCG) vaccine was evaluated.Results. The latency antigens Rv1996, Rv2031c, Rv2032 and Rv2653c and the ESAT-6 protein elicited less reactive DTH skin responses in MTB-sensitized guinea pigs than those resulting from PPD, but elicited no response in BCG-vaccinated guinea pigs. The remaining two latency antigens (DevR and Rv3716c) elicited DTH responses in both groups of animals, as did PPD. The reactivity of PPD in BCG-vaccinated guinea pigs was greater than that of any of the selected skin test reagents. Using stronger concentrations of selected skin test reagents in the patch test led to increased DTH responses that were comparable to those elicited by PPD in guinea pigs sensitized with MTB.Conclusion. Transdermal application of defined purified antigens might be a promising method for LTBI screening.

Molecular analysis of the mutational effects of Thai street rabies virus with increased virulence in mice after passages in the BHK cell line.

QS-BHK-P7, street rabies virus, after passages in the BHK cell line, had an in vitro phenotype that distinguished it from its parental virus. Both viruses caused lethal infection in mice by central nervous system inoculation; however, only QS-BHK-P7 killed mice by the intramuscular route. We found four mutations, S23R and H424P in ectodomain of the glycoprotein (G), I1711 V in the polymerase genes, and another at the non-coding region between the phosphoprotein and matrix protein genes of QS-BHK-P7. None of the mutations in the G gene occurred in previously reported pathogenic determinants. The roles of mutations in particular non-coding regions remain to be elucidated.

One clinic visit for pre-exposure rabies vaccination (a preliminary one year study).

We performed an abbreviated prospective study of rabies pre-exposure (PREP) vaccination in 109 volunteers. Group 1, the control group, received the conventional 3 intradermal injections on days 0, 7 and 21. Group 2 received one rabies vaccine injection (0.1 ml intradermally) at 2 sites on a single day. Group 3 was given one full ampule intramuscularly. One year later, all 3 groups received booster injections (0.1 ml at 4 sites) intradermally at one time or 2 injections intramuscularly on days 0 and 3. All subjects achieved a vigorous anamnestic antibody response 7 days after the boosters. These data suggest that one time immunization of one full dose intramuscularly or 2 site injections of 0.1 intradermally on a single day are adequate to prime immune memory and obtain an accelerated immune response one year later.

Postexposure rabies prophylaxis completed in 1 week: preliminary study.

BACKGROUND: Patients exposed to a rabid animal often travel long distances to receive postexposure prophylaxis (PEP), which requires 4 or 5 visits. Reducing the number of clinic visits would not only reduce costs for the patient but may also help increase compliance to receive complete PEP. We made an effort to develop PEP completed in 1 week. METHODS: We administered the 4-site intradermal injections of 0.1 mL of purified Vero cell rabies vaccine to the deltoids and thighs on days 0, 3, and 7, with and without equine rabies immunoglobulin (40 IU/kg). A control group received the World Health Organization-approved and widely used Thai Red Cross regimen (2-site intradermal injections on days 0, 3, and 7 and 1 injection on days 28 and 90) with equine rabies immunoglobulin. We then determined rabies neutralizing antibody (NAb) up to day 360. RESULTS: Geometric mean titers for subjects receiving the 4-site intradermal regimen, with or without equine rabies immunoglobulin, had significantly higher NAb values than did the control group on day 14 and 28 (P<.001). All subjects in all groups had a NAb value > or =0.5 IU/mL on days 14 and 28. The percentages of subjects who had a NAb value > or =0.5 IU/mL from days 0 through 360 were not significantly different among the 3 groups. CONCLUSIONS: After any PEP regimen, World Health Organization recommendations require a NAb value > or =0.5 IU/mL on days 14 and 28. The 1-week PEP regimen, therefore, appears promising. It increased immunogenicity over the 2-site intradermal schedule, and it is convenient and can be used in small clinics, because it consumes almost the entire supplied vaccine ampoule volume.