Seroprevalence of non-typhoidal Salmonella disease and associated factors in children in Mukuru settlement in Nairobi County, Kenya.

Non-typhoidal Salmonella (NTS) infections remain a significant public health challenge especially in sub-Saharan Africa. NTS disease is endemic in Kenya and is associated with sporadic fatal outbreaks in several regions of the country with poor resource setting. Data is limited on background exposure of NTS in the population in endemic areas and the general immune status of the community most affected by NTS. The aim of the study was to determine the proportion of children exposed to Salmonella Enteritidis or Salmonella Typhimurium O antigen among the apparently healthy children and patients and the associated host and environmental factors among children attending selected healthcare facilities in Mukuru, Nairobi County, Kenya. A cross-sectional case-control study was conducted among patients and apparently healthy participants aged 0-5 years. Blood was collected and centrifuged to obtain serum. The serum was used to test for the presence of antibodies (IgA, IgG, IgM) against NTS using ELISA. A questionnaire was administered to obtain relevant demographic, socio-economic and healthcare utilization information. A total of 382 children were recruited into the study. The NTS seroprevalence was 12.6%. Among the apparently healthy participants, mean age of those exposed to NTS was 36 months and those not exposed was 27 months. Among patients, the mean age was 39 months and those not exposed was 30 months. The seroprevalence of NTS infection among the apparently healthy was significantly associated with cooking water, washing water and age of the child. Treating water using chlorine or boiling method was identified as being protective against contracting Salmonella Typhimurium/Enteritidis. Among the patients, the proportion of exposure was significantly associated with keeping animals and the chicken count. There is a high exposure to NTS among young children below five years of age and the population has developed immunity to the disease.

In vitro activity and in vivo efficacy of a combination therapy of diminazene and chloroquine against murine visceral leishmaniasis.

The present study evaluated the in vitro activity and in vivo efficacy of diminazene combined with chloroquine as a potential drug against Leishmania donovani. Amphotericin B was used as a positive control drug. In vitro activity involved incubation of various drug concentrations with promastigotes or vero cells in culture before determination of parasite growth inhibition or cell death while in vivo evaluations involved infection of various mice groups with virulent L. donovani parasites and treatment with test drug compounds following disease establishment. Weight changes in experimental mice were also evaluated before infection and throughout the experiment. The results indicated that the diminazene-chloroquine combination was at least nine times more efficacious than individual drugs in killing promastigotes in culture. The diminazene-chloroquine combination was safer (Ld50 = 0.03±0.04) than Amphotericin B (Ld50 = 0.02±0.01). Body weight in infected mice increased significantly (P = 0.0007) from day 7 to day 37 following infection (P = 0.026). However, body weight remained comparable in all mice groups during treatment (P = 0.16). The diminazene-chloroquine combination significantly reduced splenic parasite numbers as compared to individual drug therapies (P = 0.0001) although Amphotericin B was still more efficacious than any other treatment (P = 0.0001). Amongst the test compounds, the diminazene-chloroquine combination showed the lowest level of IgG antibody responses with results indicating significant negative correlation between antileishmanial antibody responses and protection against disease. These findings demonstrate the positive advantage and the potential use of a combined therapy of diminazene-chloroquine over the constituent drugs. Further evaluation is recommended to determine the most efficacious combination ratio of the two compounds.

Experimental therapeutic studies of Solanum aculeastrum Dunal. on Leishmania major infection in BALB/c mice.

OBJECTIVES: Solanum acueastrum Dunal. has been shown to have some chemotherapeutic value. Leaf and berry water and methanol compounds of S. acueastrum were evaluated for possible antileishmanial activity In vivo on BALB/c mice and in vitro against Leishmania major promastigotes, amastigotes and vero cells. MATERIALS AND METHODS: Dry S. aculeastrum berry and leaf material were extracted in methanol and water. L. major parasites were exposed to different concentrations of S. aculeastrum fruit and leaf compounds and the IC50 on the promastigotes, percentage of infection rate of macrophages by amastigotes and the toxicological effect on vero cells were determined. BALB/c mice were infected subcutaneously with 1×10(6) promastigotes and kept for four weeks to allow for disease establishment. Infected mice were treated with fruit and leaf methanolic and water compounds, amphotericin B (AmB), and sterile phosphate buffered saline (PBS). RESULTS: Fruit methanol compound was most effective in inhibiting the growth of promastigotes with IC5078.62 µg/ml. Fruit water compound showed the best activity in inhibiting infection of macrophages by amastigotes. Fruit methanol compound was more toxic at Ld50=8.06 mg/ml to vero cells than amphotericin B. Analysis of variance computation indicated statistically significant difference in lesion sizes between experimental and control mice groups (P=0.0001). Splenic impression smears ANOVA indicated a highly significant difference in parasitic numbers between the experimental and the control groups (P=0.0001). CONCLUSION: The results demonstrate that compounds from S. aculeastrum have potential anti-leishmanial activities and the medicinal use of the plant poses considerable toxicity against dividing vero cells.

Safety and skin delayed-type hypersensitivity response in vervet monkeys immunized with Leishmania donovani sonicate antigen delivered with adjuvants.

In this study, we report on the safety and skin delayed-type hypersensitivity (DTH), responses of the Leishmania donovani whole cell sonicate antigen delivered in conjunction with alum-BCG (AlBCG), Montanide ISA 720 (MISA) or Monophosphoryl lipid A (MPLA) in groups of vervet monkeys. Following three intradermal injections of the inoculums on days 0, 28 and 42, safety and DTH responses were assessed. Preliminary tumor necrosis factor alpha (TNF-α) and interferon gamma (IFN-γ) levels were also measured and these were compared with DTH. Only those animals immunized with alum-BCG reacted adversely to the inoculum by producing ulcerative erythematous skin indurations. Non-parametric analysis of variance followed by a post-test showed significantly higher DTH responses in the MISA+Ag group compared with other immunized groups (p < 0.001). The MPLA+Ag group indicated significantly lower DTH responses to the sonicate antigen compared with the AlBCG+Ag group. There was a significant correlation between the DTH and cytokine responses (p < 0.0001). Based on this study we conclude that Leishmania donovani sonicate antigen containing MISA 720 is safe and is associated with a strong DTH reaction following immunization.

Safety and skin delayed-type hypersensitivity response in vervet monkeys immunized with Leishmania donovani sonicate antigen delivered with adjuvants / Segurança e reação de hipersensibilidade tardia na pele de macacos vervet imunizados com antígeno sonicado de Leishmania donovani junto com adjuvantes

In this study, we report on the safety and skin delayed-type hypersensitivity (DTH), responses of the Leishmania donovani whole cell sonicate antigen delivered in conjunction with alum-BCG (AlBCG), Montanide ISA 720 (MISA) or Monophosphoryl lipid A (MPLA) in groups of vervet monkeys. Following three intradermal injections of the inoculums on days 0, 28 and 42, safety and DTH responses were assessed. Preliminary tumor necrosis factor alpha (TNF-α) and interferon gamma (IFN-γ) levels were also measured and these were compared with DTH. Only those animals immunized with alum-BCG reacted adversely to the inoculum by producing ulcerative erythematous skin indurations. Non-parametric analysis of variance followed by a post-test showed significantly higher DTH responses in the MISA+Ag group compared with other immunized groups (p < 0.001). The MPLA+Ag group indicated significantly lower DTH responses to the sonicate antigen compared with the AlBCG+Ag group. There was a significant correlation between the DTH and cytokine responses (p < 0.0001). Based on this study we conclude that Leishmania donovani sonicate antigen containing MISA 720 is safe and is associated with a strong DTH reaction following immunization.

Neste estudo reportamos segurança e resposta de hipersensibilidade tardia (DTH) do antígeno sonicado de células totais de Leishmania donovani introduzidos juntamente com alume-BCG (AIBCG) Montanide ISA 720 (MISA) ou lípide A monofosforilado (MPLA) em grupos de macacos vervet. Depois de três injeções intradérmicas do inóculo nos dias 0, 28 e 42 segurança e resposta DTH foram avaliados. Preliminarmente níveis de fator de necrose tumoral alfa (TNF-α) e interferon gama (IFN-γ) foram também medidos e comparados com o DTH. Somente os animais imunizados com alume-BCG reagiram de maneira diversa ao inóculo produzindo indurações ulceradas e eritematosas na pele. Análise não paramétrica de variação seguida por um teste posterior mostraram resposta significantemente mais alta do DTH no grupo MISA + Ag quando comparado com outros grupos imunizados (p < 0.001). O grupo MPLA + Ag demonstrou resposta DTH significantemente menor do antígeno sonicado comparado com o grupo AIBCG + Ag. Houve correlação significante entre o DTH e a resposta às citocinas (p < 0.0001). Baseados neste estudo concluímos que o antígeno sonicado de Leishmania donovani contendo MISA 720 é seguro e está associado com forte reação DTH após imunização.

Subcutaneous immunization against Leishmania major - infection in mice: efficacy of formalin-killed promastigotes combined with adjuvants.

Formalin-killed promastigotes (FKP) of Leishmania major, in combination with Montanide ISA 720 (MISA), BCG or alum were used in vaccination of an inbred murine model against cutaneous leishmaniasis (CL). Significant and specific increases in anti-FKP IgG responses were detected for both alum-FKP and BCG-FKP compared to MISA-FKP (p < 0.001). Significant increases in splenic lymphocyte recall proliferation was obtained in the MISA-FKP vaccinated mice compared to alum-FKP or BCG-FKP vaccinated groups (p < 0.01). The highest interferon-gamma responses were observed in the BCG-FKP group followed by the MISA-FKP while the alum-FKP gave the least responses. Significantly reduced lesion sizes were obtained in the MISA-FKP group compared to the BCG/alum adjuvants-FKP vaccinated groups. Although the BCG-FKP group showed the highest IFN-gamma responses, it failed to control cutaneous lesions. Significant reductions in parasite numbers were observed in the MISA-FKP and BCG-FKP vaccinated groups (p < 0.001). There was a good correlation between parasite burden and IFN-gamma level indicating IFN-gamma response as a sensitive parameter of the immune status. In conclusion, MISA-FKP is the most efficacious vaccine formulation against murine cutaneous leishmaniasis.

Subcutaneous immunization against Leishmania major - infection in mice: efficacy of formalin-killed promastigotes combined with adjuvants / Imunização subcutânea na infecção do camundongo pela Leishmania major: eficácia dos promastigotos mortos pela formalina combinada com adjuvantes

Formalin-killed promastigotes (FKP) of Leishmania major, in combination with Montanide ISA 720 (MISA), BCG or alum were used in vaccination of an inbred murine model against cutaneous leishmaniasis (CL). Significant and specific increases in anti-FKP IgG responses were detected for both alum-FKP and BCG-FKP compared to MISA-FKP (p < 0.001). Significant increases in splenic lymphocyte recall proliferation was obtained in the MISA-FKP vaccinated mice compared to alum-FKP or BCG-FKP vaccinated groups (p < 0.01). The highest interferon-ã responses were observed in the BCG-FKP group followed by the MISA-FKP while the alum-FKP gave the least responses. Significantly reduced lesion sizes were obtained in the MISA-FKP group compared to the BCG/alum adjuvants-FKP vaccinated groups. Although the BCG-FKP group showed the highest IFN-ã responses, it failed to control cutaneous lesions. Significant reductions in parasite numbers were observed in the MISA-FKP and BCG-FKP vaccinated groups (p < 0.001). There was a good correlation between parasite burden and IFN-ã level indicating IFN-ã response as a sensitive parameter of the immune status. In conclusion, MISA-FKP is the most efficacious vaccine formulation against murine cutaneous leishmaniasis.

Promastigotos mortos pela formalina (FKP) de Leishmania major combinados com Montanide ISA 720 (MISA), BCG ou alumen foram usados na vacinação de modelo murino cutâneo de leishmaniose (CL). Aumento significante e específico de resposta IgG anti FKP foram detectados tanto no FKP com alumen como naquele com BCG comparados ao MISA-FKP (p < 0,001). Aumento significante da proliferação esplênica de linfócitos de memória foi obtida nos camundongos vacinados com MISA-FKP quando comparados aos grupos vacinados com alumen-FKP ou BCG-FKP (p < 0,01). As maiores respostas por interferon-gama foram observadas no grupo BCG-FKP seguido pelo MISA-FKP enquanto que o alumen-FKP deu a menor resposta. No grupo MISA-FKP foram obtidas reduções significantes do tamanho das lesões quando comparado aos grupos vacinados com BCG/adjuvante de alumen-FKP. Embora o grupo BCG-FKP tenha mostrado a maior resposta por interferon-gama, não houve controle das lesões cutâneas. Redução significante no número de parasitas foi observada tanto no grupo vacinado com MISA-FKP como no BCG-FKP (p < 0,001). Houve boa correlação entre a carga parasitária e o nível de interferon-gama indicando que a resposta do interferon-gama é parâmetro sensível do estado imunológico. Em conclusão, MISA-FKP é a forma mais eficaz de vacina contra a leishmaniose cutânea murina.

A review of adjuvants for Leishmania vaccine candidates.

Over the last decade, there has been a flurry of research on adjuvants for vaccines, and several novel adjuvants are now licensed products or in late stage clinical development. The success of adjuvants in enhancing the immune response to antigens has led many researchers to re-focus their vaccine development programs. Although several vaccine candidates have been tested against leishmaniasis, there is yet no effective vaccine against this parasitic disease. Recent research has documented that efforts to develop effective Leishmania vaccine have been limited due to lack of an appropriate adjuvant. In view of this, this review paper outlines some of the adjuvants that have been used in Leishmania vaccine candidates and cites a few of the responses obtained from these studies. The aim of the present review is to consolidate these findings to facilitate the application of these adjuvants in general and experimental vaccinology.