Effect of passive immunity to tetanus in DTP vaccinated infants.

Tetanus antitoxin levels in DTP unvaccinated and vaccinated infants whose mothers had either received no dose or two doses of absorbed tetanus toxoid at present pregnancy were determined by the enzyme immunosorbent assay (EIA). It was found that the percentage of protective infants born from non-immunized and immunized mothers were 95.4 and 100 respectively. The transplacental tetanus immunity in infants of immunized mothers was higher than those of non-immunized mothers, however, it was significantly reduced in both groups of infants within two months. After the first dose of DTP vaccine, infants born from non-immunized mothers were able to respond well in producing antibody whereas the infants from immunized mothers were not. In the second and third dose of DTP vaccine both groups of infants had a similar range of tetanus antitoxin.

Transfer rate of transplacental immunity to tetanus from non-immunized and immunized mothers.

Tetanus antitoxin was quantitatively measured in 912 pregnant women by indirect hemagglutination test. The mothers who received no dose, one dose and two doses of tetanus toxoid were 64.6%, 10.1% and 25.3% respectively. The percentage of mothers with protective antibodies in the groups receiving none, one, and two doses of tetanus toxoid were 95.4, 100 and 100. The level of protective antibody in the newborn and the magnitude of transfer rate of passive immunity to tetanus depended directly upon the level of tetanus antitoxin in maternal serum. Mothers who had tetanus antitoxin of 1.28 IU/ml or more could transfer protection to almost all of the newborns (97%-100%) irrespective of doses of tetanus toxoid administration. However, mothers who had received two doses of tetanus toxoid during pregnancy not only confer good protection but also transfer a high tetanus antitoxin levels to their newborns.

A simple and rapid diagnostic test for typhoid fever.

Barber protein sensitized latex particles were used in the latex agglutination test for the diagnosis of typhoid fever and the result compared with that of Widal 'O' and 'H' agglutination test. The latex agglutination test was positive in all 20 bacteriologically proved typhoid patients, in 81 of 85 (95.3%) typhoid suspected patients, and only in 2 of 85 (2.3%) blood donors. In contrast, the positive rates were 60% for both 'O' and 'H' Widal agglutinations in bacteriologically proved typhoid patients, 34.2% and 71.7% respectively in typhoid suspected patients, and none of blood donors were positive. The sensitivity and specificity of the latex agglutination test were 100% and 97.6% respectively with positive and negative predictive values of 90.9% and 100% respectively. The latex agglutination test may be particularly useful for the presumptive diagnosis of typhoid fever in remote health centres.

Diagnosis of typhoid fever by indirect hemagglutination with lyophilized cells.

An IHA test using stable sensitized red cells was developed for diagnosis of typhoid fever. The antibodies to LPS and CB coated cells were measured in 39 patients with typhoid fever and 79 healthy controls. The diagnostic titer greater than or equal to 1:80 of HA-LPS and Widal reaction; and greater than or equal to 1 : 320 of HA-CB were considered significant. It was found that either IHA or Widal test gave the same degree of sensitivity capable of diagnosing 87.2% of patients with typhoid fever. Antigenicities of lyophilized sensitized cells were retained for at least 6 months of preservation.

Immunological study of typhoid fever in man. II Cell-mediated immune response.

The development of cell-mediated immune response to lipopolysaccharide and Barber protein from Salmonella typhi was investigated in patients suffering from typhoid fever. The cell-mediated immunity as measured by the leukocyte adherence inhibition test, was demonstrable in 77% of patients with typhoid fever but only in 5.6% of healthy controls. It was found that cell-mediated immune response appeared after the first week of illness and persisted for at least 4 weeks. The time course development of cell-mediated immune response and humoral immune response was correlated but the magnitude of each response was independent on one another.

Surveillance of dengue hemorrhagic fever cases in Thailand.

A long-term surveillance system is necessary for planning and evaluation of hemorrhagic fever control Dry blood collection and using one dengue 2 antigen have been proved to be an efficient method to detect low and high level of HI antibody, determined to prove dengue infection. The percentage of dengue infection serologically proved from cases reported throughout a 3 year study was 52%. Dengue infected cases were reported outside epidemic period with lowest incidence in January. The majority of dengue proven cases occur at age 6 years. For chikungunya infection, studied in Bangkok metropolis and in this study in 72 provinces shows similar result indicating that chikungunya virus shows no significance in clinical and laboratory study in the surveillance programme. This study provides definite information for the planning and evaluation of hemorrhagic fever control.

Immunological study of typhoid fever in man: humoral immune response.

Widal and indirect haemagglutination test were used to study the humoral immune response of 45 patients with typhoid fever. The Widal and IHA tests were positive in 41 (91.1%) and 42 (93.3%) of patients with typhoid fever after the second week of illness. Comparison between the Widal and IHA test showed that the latter was more sensitive as assessed by Wilcoxon matched-pairs signed-ranks test (p less than 0.01). The anti-LPS antibody belongs to all three classes of immunoglobulins namely IgG, IgM and IgA with the confinement mostly to IgG and IgM. It was found that the level of haemagglutinating enhancement activity was strongest in IgG class. The low level of anti LPS-antibody was found in healthy persons with the pattern of immunoglobulin class of antibody similar to that in patients with typhoid fever.