METHODS: To determine Zika virus (ZIKV) seroprevalence in Kuala Lumpur, Malaysia, 1085 serum samples from 2012, 2014-2015 and 2017 were screened for anti-ZIKV antibodies using a ZIKV NS1 blockade-of-binding assay. Reactive samples were confirmed using neutralization assays against ZIKV and the four dengue virus (DENV) serotypes. A sample was possible ZIKV seropositive with a ZIKV 50% neutralization (NT50) titre ≥20. A sample was probable ZIKV seropositive if, in addition, all DENV NT50 titres were <20 or the ZIKV NT50 titre was >4-fold greater than the highest DENV NT50 titre.
RESULTS: We found low rates of possible ZIKV seropositivity (3.3% [95% confidence interval {CI} 2.4 to 4.6]) and probable ZIKV seropositivity (0.6% [95% CI 0.3 to 1.4]). Possible ZIKV seropositivity was independently associated with increasing age (odds ratio [OR] 1.04 [95% CI 1.02 to 1.06], p<0.0001) and male gender (OR 3.5 [95% CI 1.5 to 8.6], p=0.005).
CONCLUSIONS: The low ZIKV seroprevalence rate, a proxy for population immunity, does not explain the low incidence of Zika in dengue-hyperendemic Kuala Lumpur. Other factors, such as the possible protective effects of pre-existing flavivirus antibodies or reduced transmission by local mosquito vectors, should be explored. Kuala Lumpur is at high risk of a large-scale Zika epidemic.
METHODS: Girls received 2 (months 0 and 6 [0, 6]: n = 301; months 0 and 12 [0, 12]: n = 151) or 3 doses (months 0,2, and 6 [0, 2, 6]: n = 301); boys received 2 doses ([0, 6]: n = 301; [0, 12]: n = 150); and young women received 3 doses ([0, 2, 6]: n = 314) of 9vHPV vaccine. Anti-HPV geometric mean titers (GMTs) were assessed by competitive Luminex immunoassay (cLIA) and immunoglobulin G-Luminex immunoassay (IgG-LIA) through month 36.
RESULTS: Anti-HPV GMTs were highest 1 month after the last 9vHPV vaccine regimen dose, decreased sharply during the subsequent 12 months, and then decreased more slowly. GMTs 2 to 2.5 years after the last regimen dose in girls and boys given 2 doses were generally similar to or greater than GMTs in young women given 3 doses. Across HPV types, most boys and girls who received 2 doses (cLIA: 81%-100%; IgG-LIA: 91%-100%) and young women who received 3 doses (cLIA: 78%-98%; IgG-LIA: 91%-100%) remained seropositive 2 to 2.5 years after the last regimen dose.
CONCLUSIONS: Antibody responses persisted through 2 to 2.5 years after the last dose of a 2-dose 9vHPV vaccine regimen in girls and boys. In girls and boys, antibody responses generated by 2 doses administered 6 to 12 months apart may be sufficient to induce high-level protective efficacy through at least 2 years after the second dose.
METHODS: A sandwich ELISA using B. malayi soluble antigen was employed to detect antifilarial IgG4 antibodies in serum samples of 330 individuals who comprised 88 healthy individuals from nonendemic areas, 15 B. malayi microfilaraemic cases, 22 individuals with soil-transmitted helminthiases, 9 elephantiasis cases and 196 residents from a B. malayi-endemic area. An O.D. value of > 0.420 at serum dilution of 1:400 was used as the cut-off point. This cut-off point was obtained by taking the mean optical density (0.252 + 4 S.E.) of 36 negative sera which had O.D. values greater than 0.1 at serum dilution of 1:400.
RESULTS: All 15 microfilaraemic persons were positive for antifilarial IgG4 antibody. Non-endemic normals, soil-transmitted helminth infected persons and chronic elephantiasis cases were negative for antifilarial IgG4 antibody. Of the 196 individuals from the filaria endemic area, 37 (18.8%) demonstrated presence of antifilarial IgG4 antibodies; and only eight individuals (4.1%) were positive for microfilariae. All eight microfilaraemic individuals were also positive for antifilarial IgG4 antibodies.
CONCLUSION: Antifilarial IgG4-ELISA could detect 4.6 times more positive cases than the microfilaria detection method. With appropriate cut-off values that eliminate cross-reactivities, this serological tool is very useful for Brugia malayi prevalence surveys and diagnosis.
RESULTS: The LACV was evaluated for its colonization potential, reactogenicity, immunogenicity and protective efficacy in animal models after its storage at room temperature for 140 days. In suckling mice colonization assay, the LACV recorded the highest recovery of (7.2 × 107 CFU/mL) compared to those of unformulated VCUSM14P (5.6 × 107 CFU/mL) and the WT O139 strain (3.5 × 107 CFU/mL). The LACV showed no reactogenicity even at an inoculation dose of 104-106 CFU/mL in a rabbit ileal loop model. The rabbits vaccinated with the LACV or unformulated VCUSM14P survived a challenge with WT O139 and showed no signs of diarrhoea or death in the reversible intestinal tie adult rabbit diarrhoea (RITARD) model. Vaccinated rabbits recorded a 275-fold increase in anti-CT IgG and a 15-fold increase in anti-CT IgA antibodies compared to those of rabbits vaccinated with unformulated VCUSM14P. Vibriocidal antibodies were increased by 31-fold with the LACV and 14-fold with unformulated VCUSM14P.
CONCLUSION: The vaccine formulation mimics a natural infection, is non-reactogenic and highly immunogenic in vivo and protects animals from lethal wild-type V. cholerae O139 challenge. The single dose LACV formulation was found to be stable at room temperature (25 ± 2 °C) for 140 days and it would result in significant cost savings during mass cholera vaccination campaigns.