Defaecation pattern and intestinal transit in Nigerian children.

The defaecation pattern and intestinal transit time of 410 apparently healthy children aged between 6 months and 5 years were studied by questionnaire and carmine red marker. The majority of the children ate a predominantly high residue diet. Stool frequency varied from once every other day to 5 times a day, with 95% of the children opening their bowels one to three times a day. There was a gradual decline in mean stool frequency with increasing age. The stool produced was usually soft and between 50 and 75 ml in size. Mean mouth to anus transit time in 98 randomly selected children from the study group was 18.3 hours. The information obtained from this study should facilitate early identification of diarrhoea and constipation in the Nigerian pre-school child.

Two enzyme linked immunosorbent assays for detecting antibodies against meningococcal capsular polysaccharides A and C.

AIMS: To evaluate two of the recent methods of coating microtitre plates in the enzyme linked immunosorbent assay (ELISA) for detecting human antibodies against meningococcal capsular polysaccharides A and C with a view to validating a specific meningococcal antibody assay for routine clinical use. METHODS: Two four-layer ELISA protocols were standardised: one method utilised meningococcal polysaccharides conjugated to poly-L-lysine polypeptide for coating the microtitre plates; another used polysaccharides mixed with methylated human serum albumin (mHSA). Titration curves were plotted for the ELISAs and the squared Pearson correlation coefficient (R2) was used to determine the degree of accuracy of fit of the curves. Specificity tests were performed by inhibition and adsorption studies. RESULTS: Both methods gave good titration curves with a high R2 of > 0.98, indicating a high degree of accuracy in forming the curves. The titration end point after vaccination, obtained by the mHSA method, was 20 times higher, however, than that obtained by the poly-L-lysine method. Specificity tests showed that in the ELISA using polysaccharide/poly-L-lysine, antibody activity of a pre-vaccination serum sample was inhibited by 37%, and of post-vaccination serum by 50% with 1000-fold excess antigen. Antibody activity (post-vaccination) was reduced by 51% and 59%, respectively, by adsorption with antigen-coated Sepharose beads or adsorption with suspensions of killed meningococci. In contrast, antibody activity of a pre-vaccination serum was inhibited by 60% and a post-vaccination serum by 90% in ELISA employing polysaccharides mixed with mHSA. Reproducibility was better with the use of methylated human serum albumin than with poly-L-lysine; the former showed intrabatch and interbatch coefficients of variation of 4% and 2%, respectively, compared with 43% (intrabatch) and 16% (interbatch) obtained with the poly-L-lysine. CONCLUSION: It is concluded that the antibody assay using meningococcal polysaccharides groups A and C mixed with mHSA is much better than that using polysaccharides coupled with poly-L-lysine.

Low seroconversion rates to measles vaccine among children in Nigeria.

The Nigerian Expanded Programme on Immunization (EPI) was assessed with particular reference to measles immunization. Of 150 children who received measles vaccine at the Institute of Child Health, University of Ibadan, Nigeria, 82 (54.7%) seroconverted. The immune response was directly related to the titre of the vaccines used. Vaccines whose titres were 10(-1) to 10(1.7) stimulated immune responses in 0-25% of vaccinees, those with titres in the range 10(-2.1) to 10(-2.5) stimulated responses in 12-47.6%, while those with titres of 10(-2.7) to 10(-3.4) stimulated responses in 87.5-100% of vaccinees. Only one of the vaccines used had a titre that met the minimum WHO required standard of log 10(-3) TCID50 at the point of vaccination.

PIP: During April 1989-February 1990, in Nigeria, health workers took blood samples from 284 children aged at least 9 months from across the socioeconomic spectrum who received measles vaccine at the Institute of Child Health of University College Hospital in Ibadan to examine seroconversion rates to lyophilized and diluted measles vaccines. This was done to evaluate the Nigerian Expanded Programme on Immunization (EPI). 16 (5.6%) had measles antibodies before vaccination. 52.8% (150) of the children returned for post-vaccination screening. 54.7% seroconverted. 86.5% of children who seroconverted had low-level antibody titers. Five of the seven children who had measles antibodies before vaccination and who had returned for post-vaccination screening had a reduced antibody titer. The other two had an increased titer. Only one of the vaccines had a titer meeting the minimum standard set by the World Health Organization (log 10-3TCID50). The immune response depended on the titer of the vaccine. For example, the Morbilvax vaccine of batch 33A13 had the highest titer (10-3.4) and stimulated the greatest immune response (93.3%), while all the batches with a titer of 10-1-1.7 (except one) stimulated no immune response. The vaccines were not stable at 45 degrees Celsius but were relatively stable at 37 degrees Celsius and -70 degrees Celsius. These findings show that low vaccine titers were responsible for the low seroconversion rates. The researchers advise EPI managers to evaluate the cold chain, to examine storage conditions, to randomly test vaccines before use, and to use highly heat-stable vaccines.

Safety and efficacy of yellow fever vaccine in children less thanone-year-old.

In a clinical trial of stabilized yellow fever vaccine from Institute Pasteur in 77 children aged seven to eight months, fever was the most significant immediate and delayed side effect. Fever occurred in 12 (15.6%) children with in 48 hours of vaccination while it occurred in 10 (12.9%) children within ten days of vaccination. Other recorded side effects were pain at innoculation site in four (5.2%) children and vomiting in one (1.3%) child. Temperature recorded in 20 of the 22 febrile episodes ranged from 37.8 degrees C to 38.6 degrees C. One of the two patients who had temperatures of 39 degrees C and above had malaria parasites in her blood film. All episodes of fever except one responded to antipyretic. There was no episode of febrile convulsion and no feature suggestive of encephalitis. Of the 20 children who had neutralization test carried out against yellow fever virus six weeks after vaccination, the test was positive in post vaccination sera of 12 (60%) children whose pre-vaccination sera were negative. Two others showed evidence of partial protection. Although the seroconversion rate of 60% is less than reported in adults and older children, the result of this study shows that yellow fever vaccine is safe and fairly effective in infants. It is our suggestion that if a larger trial confirms our findings, the vaccine may be incorporated into the expanded programme on immunization (EPI) to be given at the age of seven months after completion of diptheria, tetanus, pertussis and poliomyelitis vaccinations and before measles vaccination is due.

Serum immunoglobulin concentration in Nigerian infants.

Serum immunoglobulin (Ig) G, M and A were determined at 3-monthly intervals during the first year of life in 35 healthy Nigerian infants. The neonatal IgG values were high, but dropped rapidly by 3 months to about 37% of the neonatal value, and thereafter rose steadily. The neonatal IgM values dropped slightly (10%) by 3 months and then rose steadily to reach a level above the neonatal value after 1 year. IgA was not detected in most of the children during the neonatal period, but where it was detected and was measurable, the values were very low and then rose steadily until the age of 1 year. There was a suggestion that the pattern of immunoglobulin in infancy might be influenced by the level of maternal education.

Immunity in malaria: II. Heterophile and malarial antibodies in acute Plasmodium falciparum infection.

The sera of 55 Nigerian children (30 malarious and 25 healthy) were analysed for heterophile antibodies against normal sheep erythrocytes by the passive haemagglutination technique. Fluorescent antibodies to Plasmodium falciparum were quantified by the indirect immunofluorescence method while the three major immunoglobulins (IgG, IgA and IgM) were estimated by the radial immunodiffusion technique. An increasing age gradient was demonstrated in the heterophile antibody titres within the malarious and control groups, but there was no significant difference in the levels of immunoglobulins and malarial antibodies between the two groups. An indication of higher malarial antibody titre was only observed in the malarious group, particularly in late childhood. These results show an increasing level of heterophile antibodies with age. It is concluded that malarial antigens may play a contributory, but not a dominant role in the acquisition of heterophile antibodies. There is also a need to define the exact serum factors (antibody or non-antibody) which are associated with clinical immunity to malaria in Nigerian children.

Serum immunoglobulins in Nigerian neonates.

Serum immunoglobulins G, M and A levels were studied in 187 Nigerian neonates. Estimations were done by the radial immunodifusion method of Mancini. Immunoglobulin G shows a fall in value in the first few days of life to about 62% of the value in the last days of the neonatal period. There is however a gradual increase in the level of IgM to about double at the end of the neonatal period. IgA level remained relatively constantly low throughout this period. The effect of maternal education on the levels of immunoglobulins of their neonates was also investigated. This had a positive influence at the secondary educational level, affecting only the IgG and IgA.

Immunity in malaria: depression of delayed hypersensitivity reaction in acute Plasmodium falciparum infection.

The effect of acute Plasmodium falciparum malaria infection on the cell-mediated immune response of 30 Nigerian children attending the General Out-patient (GOP) Clinic of the University College Hospital, Ibadan, Nigeria, was assessed in a controlled study. Delayed-type hypersensitivity skin reaction to five tuberculin units (5 TU) of purified protein derivative (PPD) was used as an indicator of cell-mediated immunity. The results showed marked depression of delayed hypersensitivity reaction to PPD in 27 (90%) of the malarious children, compared with four (16%) of the 25 control healthy subjects (P less than 0.0005). This depression was observed despite evidence of previous BCG vaccination in 38 (69.1%) of the 55 children in the study. The possible clinical significance of these observations in tropical paediatric practice, and the immunopathological implications, are discussed.

Depressed natural killer cell activity in children with protein--calorie malnutrition. II. Correction of the impaired activity after nutritional recovery.

Natural killer (NK) cell activity and responsiveness to interferon (IFN) were measured in the peripheral blood of infants having kwashiorkor or marasmus and of nutritionally recovered malnourished children. Depression of NK activity in the peripheral blood lymphocytes (PBLs) of the malnourished children was noted, while normal levels of activity were observed in the nutritionally recovered infants. Addition of exogeneous interferon in vitro potentiated the NK levels of PBLs from well-nourished and nutritionally recovered infants, but had either a nonsignificant impact on cells from the marasmic infants or a suppressive effect on the cells from infants with kwashiorkor. The success of exogenous interferon to potentiate the NK levels of PBLs from nutritionally recovered infants suggests that nutritional repletion corrects the impaired cellular responsiveness in these patients.

Positive correlation between degree of parasitemia, interferon titers, and natural killer cell activity in Plasmodium falciparum-infected children.

Natural killer (NK) cell activity and interferon levels have been measured in the peripheral blood of children acutely ill with Plasmodium falciparum infection. The NK cell levels were found to be raised in the malaria-infected children, with a positive correlation between the degree of parasitemia and lytic activity. Comparatively high titers of antiviral activity was discovered in sera from the majority of P. falciparum-infected children, again positively correlating with the degree of parasitemia and NK levels. The characteristics of the antiviral factor indicated alpha-type interferon to be the dominating agent involved. Addition of exogenous interferon in vitro potentiated the NK levels of PBL from normal children while having no significant impact on cells from malaria-infected children.