Germinal centre and marginal zone B cells expand quickly in a second Plasmodium chabaudi malaria infection producing mature plasma cells.

Antibodies and B cells are critical in the protective immune response to the blood stage of the malaria parasite, Plasmodium chabaudi. However, little is known about the development of memory B cells and their differentiation into plasma cells during infection or after re-infection. Here we have shown that B cells with phenotypic characteristics of memory cells (CD19(+)IgD(-) CD38(+), IgG1(+)) are generated in a primary Plasmodium chabaudi chabaudi infection of mice. In addition, we observed that germinal centre cells (CD19(+), GL7(+), MHCII(hi)) and Marginal Zone B cells (CD19(+)CD23(-)IgD(-)) show faster expansion on re-infection than in the primary, though other subsets do not. Interestingly, though both IgM(-) and IgM(+) memory cells are produced, IgM(+) memory cells do not expand on second infection. The second infection quickly produced mature bone marrow plasma cells (intracellular Ig(hi), CD138(hi), CD9(+), B220(-)), compared to primary infection; which generates a very large population of immature splenic plasma cells (B220+). This analysis suggests that a memory B cell population is generated after a single infection of malaria, which on re-infection responds quickly producing germinal centres and generating long-lived plasma cells making the second encounter with parasite more efficient.

Regulation of immune response by Plasmodium-infected red blood cells.

During the asexual blood stage infection of the human malaria parasite, Plasmodium falciparum, parasite-derived proteins are inserted onto the surface of the host red blood cell membrane. These proteins are highly variable and were originally thought only to mediate antigenic variation, and sequestration of parasites from peripheral circulation, thus enabling immune evasion. Recent studies have revealed that PfEMP-1 and other molecules on the P. falciparum-infected red blood cell (PfRBC) activate and modulate the immune response. In this review, we discuss how PfRBCs interact with antigen-presenting cells (APCs) and other cells of the immune system, and how such interactions could modulate the host response to Plasmodium infections.

Oxidative stress and erythrocyte damage in Kenyan children with severe Plasmodium falciparum malaria.

Anaemia causes significant morbidity in children with Plasmodium falciparum malaria, but the mechanism(s) are unclear. During malarial infection, increased reactive oxygen species (ROS) are generated that may contribute to erythrocyte damage and anaemia. This study measured the concentrations of alpha-tocopherol in plasma and erythrocyte membranes, and the percentage polyunsaturated fatty acid composition (%PUFA) (an indirect marker of ROS damage) in erythrocyte membranes in children with severe P. falciparum malaria from Kilifi, Kenya, and asymptomatic children from the same district. Malarial subjects were stratified into complicated malaria and malaria anaemia. Results demonstrated significant reductions in erythrocyte membrane alpha-tocopherol concentration (1.63 +/- 0.16 versus 3.38 +/- 0.18 micromol/mg protein; P < 0.001) and total %PUFA (30.7 +/- 0.49 versus 32.8 +/- 0.44% P < 0.005) for the malarial subjects (non-stratified) compared with controls. Malarial subjects showed a significant positive correlation between membrane alpha-tocopherol and haemoglobin concentrations (P < 0.005 r = 0.63 complicated malaria group; P < 0.05 r = 0.36 non-stratified data). There were no significant differences in plasma alpha-tocopherol concentration between malaria patients and controls. In conclusion, malarial infection may be associated with oxidative damage and reduced alpha-tocopherol reserve in the erythrocyte membrane, suggesting that local antioxidant depletion may contribute to erythrocyte loss in severe malaria. Erythrocyte membrane alpha-tocopherol appeared a better indicator of ROS exposure than plasma.

Plasmodium falciparum-infected erythrocytes: agglutination by diverse Kenyan plasma is associated with severe disease and young host age.

The variant surface antigens (VSAs) of Plasmodium falciparum-infected red blood cells are potentially important targets of naturally acquired immunity to malaria. Natural infections induce agglutinating antibodies specific to the VSA variants expressed by the infecting parasites. Previously, when different parasite isolates were tested against a panel of heterologous plasma from Kenyan children, the proportion of plasma that agglutinated the parasites (the agglutination frequency [AF]) was highly variable among isolates, suggesting the existence of rare and prevalent variants. Here, the AF of 115 isolates from Kenyan children were compared. The results show that the AF of isolates causing severe malaria were significantly higher than those of isolates causing mild malaria; and AF decreased significantly with the increasing age of the infected child. We propose that parasites causing severe disease tend to express a subset of VSA variants that are preferentially associated with infections of children with low immunity.

Knowledge; Attitudes and Practices Towards HIV Positive and AIDS Patients among Public Service Dentists in Nairobi

The purpose of this study was to assess the knowledge; practices and attitudes towards HIV Positive/AIDS patients among 112 dentists from public institutions in Nairobi using a self-administered questionnaire. 94(83.9) responded. Over 74had managed HIV positive/AIDS patients. In general; respondents' knowledge and preventive measures against HIV infection were satisfactory. 8.5did not find use of protective eye wear absolutely necessary. 33used protective covers routinely. 52.1advocated for the screening of all suspected cases of AIDS before treatment. 27.7felt that HIV positive health workers and those with AIDS should not be allowed to treat patients. 53.2felt that they should be given the right to decide on treating HIV Positive/AIDS patients. 10.6supported the idea that AIDS patients be isolated from uninfected individuals. It is concluded that a substantial number of dentists were wanting in their attitudes towards HIV positive/AIDS patients

Occurrence and pattern of mandibular fractures at Kisii District Hospital, Kenya.

A retrospective study of the hospital records revealed that 39 cases of mandibular fractures presented at Kisii District Hospital during a two-year period. 27 cases were due to interpersonal violence while road traffic accidents and accidental falls accounted for 9 and 3 of the cases respectively. The male ratio was 2.9:1. Majority (26 cases) of the patients were aged between 20 and 39 years. The commonly involved fracture site was the left body of the mandible accounting for 20 of the fractures.

Oral hygiene habits and dental health awareness of Kenyan children aged 9-15 years in a peri-urban and urban school.

The oral hygiene habits and dental health awareness of 541 Kenyan children from a peri-urban and urban school and aged 9-15 years, were investigated. 80.2% of the urban children and 43.1% of the peri-urban children had visited a dentist before. 12.4% of the urban children and 9.2% of the peri-urban children knew that bacteria cause dental caries. Over 87% of the children from either school knew that dental caries and periodontitis can be prevented. The main reason for visiting a dentist was to have tooth extraction. Failure to brush teeth was believed to be the cause of gingival bleeding by 38.9% of the peri-urban children and 37.6% of the urban children. 67.2% of the peri-urban children and 39.5% of the urban children brushed their teeth thrice daily. 21.1% of the peri-urban children and 2% of the urban children used a chewing stick to brush their teeth. More urban children (96.5%) used a toothbrush than peri-urban children (64.8%). None of the children from either school admitted using traditional cleaning aids such as the finger and charcoal. It is concluded that there were no consistent differences in oral hygiene habits and dental health awareness between peri-urban and urban children.