The effects of aflatoxin exposure on Hepatitis B-vaccine induced immunity in Kenyan children.

BACKGROUND: Globally, approximately three million children die each year from vaccine preventable infectious diseases mainly in developing countries. Despite the success of the expanded immunization program, not all infants and children around the world develop the same protective immune response to the same vaccine. A vaccine must induce a response over the basal immune response that may be driven by population-specific, environmental or socio-economic factors. Mycotoxins like aflatoxins are immune suppressants that are confirmed to interfere with both cell-mediated and acquired immunity. The mechanism of aflatoxin toxicity is through the binding of the bio-activated AFB1-8, 9-epoxide to cellular macromolecules. METHODS: We studied Hepatitis B surface antibodies [anti-HBs] levels to explore the immune modulation effects of dietary exposure to aflatoxins in children aged between one and fourteen years in Kenya. Hepatitis B vaccine was introduced for routine administration for Kenyan infants in November 2001. To assess the effects of aflatoxin on immunogenicity of childhood vaccines Aflatoxin B1-lysine in blood serum samples were determined using High Performance Liquid Chromatography with Fluorescence detection while anti-HBs were measured using Bio-ELISA anti-HBs kit. RESULTS: The mean ± SD of AFB1-lysine adducts in our study population was 45.38 ± 87.03 pg/mg of albumin while the geometric mean was 20.40 pg/mg. The distribution of AFB1-lysine adducts was skewed to the right. Only 98/205 (47.8%) of the study population tested positive for Hepatitis B surface antibodies. From regression analysis, we noted that for every unit rise in serum aflatoxin level, anti-HBs dropped by 0.91 mIU/ml (-0.9110038; 95% C.I -1.604948, -0.21706). CONCLUSION: Despite high coverage of routine immunization, less than half of the study population had developed immunity to HepB. Exposure to aflatoxin was high and weakly associated with low anti-HBs antibodies. These findings highlight a potentially significant role for environmental factors that may contribute to vaccine effectiveness warranting further research.

Identification of preferential CD4+ T-cell targets for HIV infection in the cervix.

A better understanding of the cellular targets of HIV infection in the female genital tract may inform HIV prevention efforts. Proposed correlates of cellular susceptibility include the HIV co-receptor CCR5, peripheral homing integrins, and immune activation. We used a CCR5-tropic pseudovirus to quantify HIV entry into unstimulated endocervical CD4(+) T cells collected by cytobrush. Virus entry was threefold higher into cervix-derived CD4(+) T cells than blood, but was strongly correlated between these two compartments. Cervix-derived CD4(+) T cells expressing CD69, α(4)ß(7), or α(4)ß(1) were preferential HIV targets; this enhanced susceptibility was strongly correlated with increased CCR5 expression in α(4)ß(7)(+) and CD69(+) CD4(+) T cells, and to a lesser extent in α(4)ß(1)(+) CD4(+) T cells. Direct binding of gp140 to integrins was not observed, integrin inhibitors had no effect on virus entry, and pseudotypes with an env that preferentially binds α(4)ß(7) still demonstrated enhanced entry into α(4)ß(1)(+) cells. In summary, a rapid and sensitive HIV entry assay demonstrated enhanced susceptibility of activated endocervical CD4(+) T cells, and those expressing α(4)ß(7) or α(4)ß(1). This may relate to increased CCR5 expression by these cell subsets, but did not appear to be due to direct interaction of α(4)ß(7) or α(4)ß(1) with HIV envelope.

Serologic testing algorithm for recent HIV seroconversion in estimating incidence of HIV-1 among adults visiting a VCT centre at a Kenyan tertiary health institution.

OBJECTIVE: To determine HIV high risk groups among adults visiting Kenyatta National Hospital Voluntary Counselling and Testing Centre by use of Serologic Testing Algorithm for Recent HIV Seroconversion (STARHS). DESIGN: A cross-sectional study of adults. SETTING: Kenyatta National Hospital Voluntary and Counselling Centre. RESULTS: Of the 6,415 adults screened for antibodies to HIV at Kenyatta National Hospital VCT Centre between July 2002 and February 2003, 728 tested positive in the two HIV screening tests used at the center, indicating a prevalence of 11%. Of these seropositive cases, 355 consented to participate in the study. Using STARHS, 34 (9.6%) of the plasma samples were classified as being from individuals with recent infection (within 170 days), giving an annual estimated HIV-1 incidence in this population of 1.3 infections per 100 person-years with a 95% CI of 0.872-1.728%. Young adults had a higher rate of new infection than older adults. Young females were infected much earlier in life, with a peak age of new infections of 26 years, versus 31 years for young males. CONCLUSION: This study confirms our hypothesis that STARHS or Detuned assay can be used to determine HIV incidence in this population. The HIV high risk groups as identified by this study are young women between ages 16 to 26 years old and men between ages 45 to 55 years of age.

Pregnancy rates among female participants in phase I and phase IIA AIDS vaccine clinical trials in Kenya.

BACKGROUND: Female participants in AIDS candidate vaccine clinical trials must agree to use effective contraception to be enrolled into the studies, and for a specified period after vaccination, since the candidate vaccines' effects on the embryo or foetus are unknown. OBJECTIVES: To review data on female participants' pregnancy rates from phase I and IIA AIDS vaccine clinical trials conducted at the Kenya AIDS Vaccine Initiative (KAVI) and to discuss the challenges of contraception among female participants. DESIGN: Descriptive observational retrospective study. SETTING: KAVI clinical trial site, Kenyatta National Hospital and University of Nairobi, Kenya. SUBJECTS: Thirty nine female participants were enrolled into these trials. They received family planning counselling and were offered a choice of different contraceptive methods, as per the protocols. All contraception methods chosen by the participants were offered at the study site at no cost to the participant. RESULTS: Four women conceived during the study period when pregnancies were to be avoided. All four had opted for sexual abstinence as a contraceptive method, but reported having been coerced by their partners to have unprotected sexual intercourse. CONCLUSION: Abstinence is clearly not a reliable contraceptive option for women in developing-country settings. Effective female-controlled contraceptives, administered at the clinical trial site, may empower female participants to better control their fertility, leading to more complete clinical trial data.

Sensitivity and specificity of HIV rapid tests used for research and voluntary counselling and testing.

BACKGROUND: HIV rapid tests (RT) are a quick and non-technically demanding means to perform HIV voluntary counselling and testing (VCT) but understanding their limitations is vital to delivering quality VCT. OBJECTIVE: To determine the sensitivity and specificity of HIV rapid tests used for research and voluntary counselling and testing at four sites in East Africa. DESIGN: Cross-sectional study. SETTING: Masaka District, Uganda; a sugar plantation in Kakira, Uganda; Coastal Villages in the Kilifi District of Kenya; and the Urban slum of Kangemi located West of Nairobi, Kenya. SUBJECTS: Six thousands two hundred and fifty five consenting volunteers were enrolled into the study, and 675 prevalent HIV infections were identified. RESULTS: The RT sensitivity tended to be high for all assays at all sites (97.63-100%) with the exception of the Uni-Gold assay (90.24% in Kangemi, 96.58% in Kilifi). Twenty four RT results were recorded as 'weak positives', 22 (92%) of which were negative by ELISA. There was a high rate of RT false positives in Uganda (positive predictive values ranging from 45.70% to 86.62%). CONCLUSIONS: The sensitivity and specificity of the RT varied significantly across sites. The rate of RT misclassification in Uganda suggests that a multiple test algorithm may be preferable to a single test as screener for HIV VCT.

Total lymphocyte count as a surrogate marker for CD4+ t cell count in initiating antiretroviral therapy at Kenyatta National Hospital, Nairobi.

OBJECTIVE: To evaluate the utility of Total Lymphocyte Count (TLC) as a surrogate marker for CD4 + T cell count in antiretroviral (ARV) treatment initiation in a Kenyan population of HIV seropositive patients at Kenyatta National Hospital. DESIGN: Cross-sectional descriptive study. SETTING: Kenyatta National Hospital, HIV treatment and follow-up outpatient facility; Comprehensive Care Centre, Nairobi, Kenya. SUBJECTS: Two hundred and twenty five HIV Elisa positive, ARV naive patients visiting the Comprehensive Care Centre between January 2006 to March 2006. RESULTS: A significant linear correlation was found between TLC and CD4 cell count for the whole group with a Spearman rank correlation of 0.761 (p < 0.01); and was also independently observed in the four WHO clinical stages. The classification utility of TLC 1200 cells/mm3 cut-off was suboptimal; sensitivity 37% specificity of 99% and the NPV of 56%. The receiver operator characteristics (ROC) curve generated an optimal TLC cut-off of 1900 cells/mm3 cut-off to be of greatest utility with a sensitivity of 81.1%, specificity of 90.3%, PPV of 90.8% and NPV of 80.2%. This implies that a TLC cut-off of 1900 cells/mm3 correctly classify eight out of ten HIV positive patients as having a CD4 < 200 cells/mm3 and only misclassify two such patients. Serial CD4 testing can then be performed on the minority of patients who despite a TLC > or = 1900 cells/mm3 are, on basis of clinical data, suspect of more advanced disease warranting ARV therapy. This would reduce the number of patients tested for and focus the application of CD4 testing and thus reduce attendant cost in care provision in CD4 resource poor settings. CONCLUSION: Our data showed a good positive correlation between TLC and CD4 cell count, however the WHO recommended TLC cuto-ff of 1200/mm3 was found to be of low sensitivity in classifying patients as having a CD4 counts < 200 cells/mm3. This would result in underestimation of advanced stage of disease and to withholding ARVs treatment to persons who need treatment. We recommend a TLC cut-off of 1900 cells/mm3 for our population to classify patients as either above or below the CD4 count cut-off of 200 cells/mm3 as an indicator of when to start antiretroviral therapy.

Prevalence of HCV and HIV/HCV co-infection among volunteer blood donors and VCT clients.

OBJECTIVE: To determine the prevalence of HCV infection and HCV/HIV co-infection among voluntary blood donors at the National Blood Transfusion Centre and clients at the Kenyatta National Hospital HIV-Voluntary Counseling and Testing (VCT) Centre. DESIGN: A prospective cross-sectional descriptive study. SETTING: Kenyatta National Hospital, a tertiary referral and teaching hospital and the National Blood Transfusion Services Centre, Nairobi. SUBJECTS: Volunteer blood donors and VCT attendants. RESULTS: The prevalence of HCV/HIV co-infection among 6154 blood donors in the NBTSC was very low, at 0.02. The HIV prevalence among the 353 KNH HIV-VCT clients was 9.3%, none of the clients tested positive for HCV. The incidence of risk factors in the persons with HCV and/or HIV infection(s) was low. CONCLUSION: The prevalence of HCV infection among pre-screened volunteer blood donors was low. However the current practice of screening all donated blood for HCV remains indispensable to prevent its transmission to blood recipients.

Prevalence of HCV and HCV/HIV co-infection among in-patients at the Kenyatta National Hospital.

OBJECTIVE: To determine the prevalence of HCV and HCV/HIV co-infection among medical in-patients at the Kenyatta National Hospital. DESIGN: Prospective cross-sectional descriptive study. SETTING: Kenyatta National Hospital, a tertiary referral and teaching hospital, in-patient department SUBJECTS: HIV/AIDS and HIV negative in-patients at KNH medical wards. RESULTS: Among 458 HIV/AIDS medical in-patients, the prevalence of HCV was 3.7% while in the 518 HIV negative patients, it was 4.4%. The prevalence of co-infection with HCV and HIV was 3.7%. The incidence of risk factors in persons with HCV and/or HIV infection(s) was low. CONCLUSION: This study found the prevalence of HCV infection among medical in-patients to be similar in HIV positive and HIV negative group of patients. The co-infection rates were low, as were the risk factors for transmission of these infections.

Genetic analysis of human immunodeficiency virus type 1 strains in Kenya: a comparison using phylogenetic analysis and a combinatorial melting assay.

We surveyed human immunodeficiency virus (HIV) subtype distribution from peripheral blood mononuclear cells (PBMCs) collected in 1995 from 24 HIV-1-infected Kenyan residents (specimens from predominantly male truck drivers and female sex workers near Mombasa and Nairobi). Processed lysates from the PBMC samples were used for env amplification, directly sequenced, and analyzed by phylogenetic analysis. Envelope amplification products were also used for analysis in a polymerase chain reaction (PCR)-based assay, called the combinatorial melting assay (COMA). Results of the two tests were compared for assignment of subtype for this Kenyan cohort. The COMA, a PCR capture technique with colorimetric signal detection, was used with HIV reference subtype strains as well as regional (East Africa) HIV strains for subtype identification. Performance of the COMA was at 100% concordance (24 of 24) as compared with DNA sequencing analysis. Phylogenetic analysis showed 17 isolates to be subtype A, 3 subtype D, and 4 subtype C viruses. This may represent an increase in subtype C presence in Kenya compared with previously documented reports. The COMA can offer advantages for rapid HIV-1 subtype screening of large populations, with the use of previously identified regional strains to enhance the identification of local strains. When more detailed genetic information is desired, DNA sequencing and analysis may be required.

Rapid progression to disease in African sex workers with human immunodeficiency virus type 1 infection.

From a cohort of female sex workers in Nairobi, Kenya, 163 women were observed to seroconvert to human immunodeficiency virus type 1 (HIV-1) and followed to study progression to HIV-1-related disease. The effect of several covariables on disease progression was studied using a Weibull proportional hazards model. The Weibull survival model was fitted to the observed incubation times. Estimates of the median duration to CDC stage IV-A and IV-C disease were 3.5 and 4.4 years, respectively. Condom use before seroconversion was associated with a reduced risk of CDC stage IV-A disease (relative risk = .64, P < .05). The incubation time of HIV-1-related disease is extremely short in this population.