Dynamics of host blood effects inGlossina morsitans sspp. infected withTrypanosoma congolense andT. brucei

The pattern of infection inGlossina morsitans morsitans andG. m. centralis membrane-fed on eland, buffalo or goat blood mixed withTrypanosoma congolense orT. brucei was studied from day 1 to day 10. Tsetse were initially permissive vectors, with most flies harbouring infections of 10⁴–10⁵ parasites on day 3. However, after a second blood meal on day 3, flies cleared many infections withG. m. morsitans clearing more infections thanG. m. centralis. Infective feeds of goat blood consistently increased final infection rates by limiting the number of infections lost between days 3 and 6. In further experiments withG. m. morsitans only, this effect was replicated by feeding flies on erythrocytes but not on serum. These results suggest that compounds from some mammalian erythrocytes match the target specificity ofG. m. morsitans midgut lectins and, hence, have a protective effect on trypanosome establishment in the fly.     

Influence of D(+)-glucosamine on infection rates and parasite loads in tsetse flies (Glossina spp.) infected with Trypanosoma brucei.

Teneral Glossina morsitans centralis, G. m. morsitans and G. pallidipes were infected with three different clones of Trypanosoma brucei in blood containing D(+)-glucosamine, an inhibitor of tsetse midgut lectin. On average, 5 days of D(+)-glucosamine treatment tripled infection rates, without affecting the proportion of infections that matured. Total infection rates were equal in males and females, but twice as many infections matured in males. Counts of parasites in the guts and salivary glands of 277 flies revealed order of magnitude differences among flies, with females consistently having 2-3-times as many parasites as males. Parasite numbers varied in a sex-specific manner among tsetse-clone combinations, but these differences were not correlated with similar large differences in infection rates. D(+)-glucosamine treatment had no significant effect on parasite loads.     

Relationship between Plasma Interleukin-12 (IL-12) and IL-18 Levels and Severe Malarial Anemia in an Area of Holoendemicity in Western Kenya

In this study, we investigated whether levels of interleukin-12 (IL-12) and IL-18 in plasma are associated with severe malarial anemia outcomes in an area of holoendemicity in western Kenya. We compared plasma IL-12 and IL-18 levels in six groups of children grouped into the categories aparasitemic, asymptomatic, mild malaria, high-density uncomplicated malaria (UC), moderate malarial anemia (MMA), or severe malarial anemia (SMA). IL-12 levels were significantly reduced in children with SMA (P < 0.05) but not in other groups compared to children in the aparasitemic control group. IL-18, a cytokine known to be critical for the induction of gamma interferon along with IL-12, was produced more frequently (70%) in children with UC (P = 0.06) than in children in the aparasitemic control group (32%). However, in the SMA group the IL-18 response rate declined to 30%, which was similar to that in the aparasitemic control group, which showed a 32% response rate. This finding suggests that the IL-18 response may be impaired in children with SMA. In summary, the results from this study support the hypothesis that impairment of IL-12 and/or IL-18 response may contribute to the development of severe malarial anemia in areas of holoendemicity for malaria.     

Markers in HIV associated tuberculosis in Kenya

Tuberculosis is one of the most frequent opportunistic infections in HIV-infected patients in developing countries. In some instances, manifestations of pulmonary tuberculosis precede all other HIV related signs and symptoms because of the high virulence of M. tuberculosis. In order to characterise the interaction between these two pathogens, clinical and immunological parameters in pulmonary tuberculosis patients with and without HIV infection were compared. Amongst newly diagnosed pulmonary tuberculosis patients the association of some of these changes with the clinical outcome were evaluated. Of these, 44% were co-infected with HIV. Pulmonary tuberculosis patients with HIV-1 presented more frequently with lymphadenopathy and diarrhoea than those without HIV-1. Peripheral blood CD4+ counts were significantly lower in patients with pulmonary tuberculosis with HIV-1 than those with pulmonary tuberculosis alone, P= 0.0292. Low CD4+ lymphocyte counts, lymphadenopathy and BCG scar absence could serve as indicators of HIV-1 infection in pulmonary tuberculosis (PTB) patients.     

Levels of macrophage inflammatory protein 1 alpha (MIP-1 alpha) and MIP-1 beta in intervillous blood plasma samples from women with placental malaria and human immunodeficiency virus infection

Macrophage inflammatory protein-1 alpha (MIP-1 alpha) and MIP-1 beta play an important role in modulating immune responses. To understand their importance in immunity to placental malaria (PM) and in human immunodeficiency virus (HIV)-PM coinfection, we investigated levels of these chemokines in the placental intervillous blood plasma (IVB plasma) and cord blood plasma of HIV-negative PM-negative, HIV-negative PM-positive, HIV-positive PM-negative, and HIV-positive PM-positive women. Compared to HIV-negative PM-negative women, the MIP-1 beta concentration in IVB plasma was significantly elevated in HIV-negative PM-positive women and HIV-positive PM-positive women, but it was unaltered in HIV-positive PM-negative women. Also, PM-infected women, irrespective of their HIV status, had significantly higher levels of MIP-1 beta than HIV-positive PM-negative women. The MIP-1 alpha level was not altered in association with either infection. The IVB plasma levels of MIP-1 alpha and MIP-1 beta positively correlated with the cord blood plasma levels of these chemokines. As with IVB plasma, only cord plasma from PM-infected mothers had significantly elevated levels of MIP-1 beta compared to PM-negative mothers, irrespective of their HIV infection status. MIP-1 beta and MIP-1 alpha levels in PM-positive women were positively associated with parasite density and malaria pigment levels. Regardless of HIV serostatus, the IVB MIP-1 beta level was significantly lower in women with PM-associated anemia. In summary, an elevated level of MIP-1 beta was associated with PM. HIV infection did not significantly alter these two chemokine levels in IVB plasma.     

Rapid Spread and Diversification of Respiratory Syncytial Virus Genotype ON1, Kenya

Respiratory syncytial virus genotype ON1, which is characterized by a 72-nt duplication in the attachment protein gene, has been detected in >10 countries since first identified in Ontario, Canada, in 2010. We describe 2 waves of genotype ON1 infections among children admitted to a rural hospital in Kenya during 2012. Phylogenetic analysis of attachment protein gene sequences showed multiple introductions of genotype ON1; variants distinct from the original Canadian viruses predominated in both infection waves. The genotype ON1 dominated over the other group A genotypes during the second wave, and some first wave ON1 variants reappeared in the second wave. An analysis of global genotype ON1 sequences determined that this genotype has become considerably diversified and has acquired signature coding mutations within immunogenic regions, and its most recent common ancestor dates to ≈2008–2009. Surveillance of genotype ON1 contributes to an understanding of the mechanisms of rapid emergence of respiratory viruses.     

Expression of fibrinogen receptors during activation and subsequent desensitization of human platelets by epinephrine

Epinephrine causes platelet aggregation and secretion by interacting with alpha 2-adrenergic receptors on the platelet surface. Platelet aggregation requires the binding of fibrinogen to a specific receptor on the membrane glycoprotein IIb-IIIa complex. Although the IIb-IIIa complex is identifiable on the surface of resting platelets, the fibrinogen receptor is expressed only after platelet activation. The current studies were designed to examine the effect of occupancy of platelet alpha 2-adrenergic receptors by epinephrine on the expression of fibrinogen receptors and on the aggregation of platelets. The ability of epinephrine to induce the expression of fibrinogen receptors was studied under two different conditions: acute stimulation (less than 1 min) and prolonged stimulation (50 to 90 min), the latter of which is associated with a reduction or "desensitization" of the platelet aggregation response. Expression of the fibrinogen receptor was monitored with 125I-fibrinogen as well as with 125I-PAC-1 (PAC-1), a monoclonal antibody that binds to the glycoprotein IIb-IIIa complex only after platelets are activated. Epinephrine caused an immediate increase in PAC-1 and fibrinogen binding that was dependent on occupancy of the alpha 2-receptor by epinephrine and on the presence of extracellular free Ca (KCa = 30 mumol/L). By itself, 1 mmol/L Mg was unable to support induction of the fibrinogen receptor by epinephrine. However, it did decrease the Ca requirement by about two orders of magnitude. Prolonged stimulation of unstirred platelets by epinephrine led to a 70% decrease in the aggregation response when the platelets were subsequently stirred. Despite their decreased aggregation response, desensitized platelets bound PAC-1 and fibrinogen normally, indicating that the loss of aggregation was not due simply to a decrease in fibrinogen receptor expression. Although desensitization was not affected by pretreatment of the platelets with aspirin, it was partially prevented when extracellular Ca was chelated by EDTA during the long incubation with epinephrine. These studies demonstrate that once platelet alpha 2-adrenergic receptors are occupied by epinephrine, extracellular Ca is involved in initiating the aggregation response by supporting the induction of the fibrinogen receptor and the binding of fibrinogen. Furthermore. Ca-dependent reactions subsequent to fibrinogen binding may be necessary for maximal platelet aggregation and are impaired when platelets become desensitized to epinephrine.     

The investigation of Trypanosoma brucei isolates obtained from Glossina pallidipes in South Nyanza, Kenya

During studies to determine the main Trypanosoma brucei rhodesiense transmission sites in Lambwe Valley, Western Kenya, Glossina pallidipes were collected from two areas in the valley and examined for trypanosome infection. T. brucei isolated from infected flies were tested for their response to the lethal effects of human blood (Blood Incubation Infectivity Test, BIIT) and also characterized using isoenzyme electrophoresis. Six of the 26 T. brucei tested were BIIT positive, two of which had enzyme profiles identical to human isolates. The 26 isolates were grouped into 10 zymodemes. Two zymodemes were identical to T. b. rhodesiense isolated from sleeping sickness patients, one of which was identical to the predominant zymodemes among patients from Lambwe Valley area. The other zymodeme was identical to an isolate from a patient from the Busoga (Uganda) sleeping sickness epidemic focus. These two Zymodemes were BIIT positive. It is suggested that there has been an exchange of human infecting organisms between the Kenya and the Uganda foci.