Graphene oxide nanocapsules within silanized hydrogels suitable for electrochemical pseudocapacitors

Soft biocompatible gels comprised of rolled up graphene oxide nanocapsules within the pores of silanized hydrogels may be used as electrochemical pseudocapacitors with physiological glucose or KOH as a reducing agent, affording a material suitable for devices requiring pulses with characteristic time less than a second.

The pattern of childhood hepatitis B infection in two Gambian villages

Serologic markers of hepatitis B virus (HBV) infection were measured in children from Manduar and Keneba, two adjacent villages in The Gambia, in 1980 and in 1984. The rate of HBV infection over the 4 years differed markedly: in Manduar 71% of children who were less than 5 years of age in 1980 became infected, whereas in Keneba only 37% became infected. Male children were more frequent carriers of either HBs or e antigen than were female children. Marked clustering of hepatitis B surface antigen (HBsAg) antigenemia within sibling relationships was shown in both villages. The chance of the youngest child in a household being a carrier of HBsAg was strongly related to the number of antigen-positive siblings. Four years later, 53% of children who were initially positive for HBsAg and 33% who were positive for hepatitis B e antigen still carried these antigens. Jaundice was not observed.

The effects of Plasmodium falciparum malaria on immune control of B lymphocytes in Gambian children

Children living in hyperendemic malarious regions have high immunoglobulin levels and an increased frequency of Burkitt's lymphoma. In a study of Gambian children which endeavours to explain these findings we showed that acute P. falciparum malaria caused spontaneous activation and growth of their B lymphocytes in vitro. A high proportion of these cells contained Epstein-Barr nuclear antigen (EBNA). In ancillary experiments aimed at explaining these findings. CD4 helper cells from adult donors were destroyed with monoclonal antibody and complement. This manoeuvre resulted in loss of cytotoxic T cell control of their B lymphocytes when infected with Epstein-Barr virus (EBV). In children with acute malaria, both spontaneous immunoglobulin and antibody production by B cells was increased yet CD4 helper cell control over these cells, as measured by responses to pokeweed mitogen, was found to be intact. Spontaneous and concanavalin A-driven lymphocyte proliferation was depressed. We infer from these findings that in patients with P. falciparum malaria loss of cytotoxic T cell control of the EBV in B cells, possibly due to destruction or dysfunction of a subset of CD4 cells responsible for induction of suppressor/cytotoxic CD8 cells, leads to activation and proliferation of foci of B cells containing EBV. The expanded pool and rapid turnover of these cells may increase chances of malignant transformation leading to the genesis of Burkitt's tumor. Partial loss of suppressor mechanisms coupled with normal CD4 helper/inducer activity may result in high serum levels of immunoglobulin which are characteristic of persons living in malarious regions.

Anti-sporozoite antibodies and immunity to malaria in a rural Gambian population

A conserved repeated epitope, (NANP)3, of the circumsporozoite protein of Plasmodium falciparum has been identified previously as a putative target for artificially induced immunity to malaria. We examined the role of humoral responses to this epitope in acquired immunity to malaria in a rural African population. Seropositivity to (NANP)3 was slow to develop (9% positive in subjects aged 1-11 years; 88% in those of 30 years and above), and responses in younger subjects were transient. The poor response in younger subjects did not appear to be due to immunosuppression by concomitant blood stage parasitization. The relationship between levels of anti-(NANP)3 antibodies and parasitaemia changed from positive to negative with age. 126 subjects age 1-11 years were followed through an entire transmission season; those who were seropositive at the beginning ended the season with lower parasite rates (20% vs 59%) and experienced fewer episodes of clinical malaria (0.43 vs 0.67). However, the trend towards increasing susceptibility to clinical malaria in subjects entering the transmission season with lower levels of anti-(NANP)3 antibodies was modest, and combined cross-sectional and longitudinal data indicated that the humoral response to (NANP)3 did not play a major role in the development of immunity to clinical malaria in the population we studied.

Epidemiology of rotavirus in a periurban Gambian community

Short, well demarcated epidemics of rotavirus diarrhoea were observed during two consecutive cool, dry seasons in The Gambia. This seasonal pattern has now been documented for 4 consecutive years. During the 1985/86 epidemic, transmission was intense, with a clinical attack rate for infants of 36%. During this outbreak it was estimated that asymptomatic virus-shedding was two-thirds as common as symptomatic infection. Rotavirus diarrhoea was more severe than diarrhoea due to all other causes and clinical rotavirus infection was associated with weight loss in the post-infection period. Non-epidemic periods were characterized by very occasional mild cases and asymptomatic virus-shedding in neonates. There was a change in RNA electropherotypes from a predominantly long pattern in 1983/84 and 1984/85 to short patterns in 1985/86.

Ethnic differences in the prevalence of splenomegaly and malaria in The Gambia

Significant variations in the prevalence of splenomegaly were found among members of the three main ethnic groups resident in North Bank Division, The Gambia. Among young children splenomegaly and malaria were less prevalent in Mandinkas than in Wollofs or Fulas, suggesting that some genetic or environmental factors protect Mandinka children from this infection. Among older children and adults splenomegaly was found most frequently in Fulas. Six of 22 adults with very large spleens had a high serum IgM level and probably had the hyperreactive malarial splenomegaly (tropical splenomegaly) syndrome. Four of these six subjects were Fulas. This finding, together with the results of a previous study in Nigeria, suggest that Fulas have a predisposition to this condition.

Trial of an attenuated bovine rotavirus vaccine (RIT 4237) in Gambian infants

A randomised, controlled trial of bovine rotavirus vaccine was undertaken in Gambian infants. Three doses were administered, from the age of ten weeks, concurrently with oral or killed polio vaccine. Prevaccination rotavirus neutralising antibody levels were high. 84/185 infants (45%) showed an increase in neutralising antibody titre after receiving rotavirus vaccine, compared with 20/91 (22%) unvaccinated infants. Clinical rotavirus infection was detected in 24/78 (31%) children in the rotavirus/oral polio group, 34/83 (41%) children in the placebo/oral polio group, and 23/92 (25%) children in the rotavirus/killed polio group, giving an overall vaccine efficacy of 33% (95% CI 4-53%). RIT 4237 did not appear to reduce the severity of clinical infections. Most cases (92%) were caused by rotaviruses with short RNA electropherotypes. Serological responses to rotavirus vaccination appeared unaffected by the concurrent administration of oral polio vaccine. Lower types 1 and 3 polio antibody levels were found in children who received oral polio and rotavirus vaccines but the differences were not statistically significant.