Male circumcision is associated with a lower prevalence of human papillomavirus-associated penile lesions among Kenyan men.

Human papillomavirus (HPV)-associated penile lesions in men may increase the risk of HPV transmission to their female partners. Risk factor data on HPV-associated penile lesions are needed from regions with a high burden of cervical cancer. Visual inspection of the penis was conducted using a colposcope at the 24-month visit among participants in a randomized controlled trial of male circumcision in Kenya, from May 2006 to October 2007. All photos were read independently by two observers for quality control. Penile exfoliated cells sampled from the glans/coronal sulcus and the shaft were tested for HPV DNA using GP5+/6+ PCR and for HPV16, 18 and 31 viral loads using a real time PCR assay. Of 275 men, 151 were circumcised and 124 uncircumcised. The median age was 22 years. Circumcised men had a lower prevalence of flat penile lesions (0.7%) versus uncircumcised (26.0%); adjusted odds ratio (OR) = 0.02; 95% confidence interval (CI) = 0.003-0.1. Compared to men who were HPV negative, men who were HPV DNA positive (OR = 6.5; 95% CI = 2.4-17.5) or who had high HPV16/18/31 viral load (OR = 5.2; 95% CI = 1.1-24.4) had higher odds of flat penile lesions. Among men with flat penile lesions, HPV56 (29.0%) and 16 (25.8%) were the most common types within single or multiple infections. Flat penile lesions are much more frequent in uncircumcised men and associated with higher prevalence of HPV and higher viral loads. This study suggests that circumcision reduces the prevalence of HPV-associated flat lesions and may ultimately reduce male-to-female HPV transmission.

"When I was circumcised I was taught certain things": risk compensation and protective sexual behavior among circumcised men in Kisumu, Kenya.

BACKGROUND: Male circumcision has been shown to reduce the transmission of HIV from women to men through vaginal sex by approximately 60%. There is concern that men may engage in risk compensation after becoming circumcised, diminishing the benefits of male circumcision. METHODS AND FINDINGS: We conducted qualitative interviews with 30 sexually active circumcised men in Kisumu, Kenya from March to November 2008. Most respondents reported no behavior change or increasing protective sexual behaviors including increasing condom use and reducing the number of sexual partners. A minority of men reported engaging in higher risk behaviors either not using condoms or increasing the number of sex partners. Circumcised respondents described being able to perform more rounds of sex, easier condom use, and fewer cuts on the penis during sex. CONCLUSIONS: Results illustrate that information about MC's protection against HIV has disseminated into the larger community and MC accompanied by counseling and HIV testing can foster positive behavior change and maintain sexual behavior.

Prevalence and risk factors of human papillomavirus infection by penile site in uncircumcised Kenyan men.

Human papillomavirus (HPV) prevalence was estimated from 2,705 sexually active, uncircumcised, human immunodeficiency virus seronegative men aged 17-28 years in Kisumu, Kenya. HPV prevalence was 51.1% (95% confidence interval: 49.2-53.0%) in penile cells from the glans/coronal sulcus and/or shaft. HPV prevalence varied by anatomical site, with 46.5% positivity in the glans/coronal sulcus compared with 19.1% in the shaft (p < 0.0001). High-risk HPV was detected in 31.2% of glans and 12.3% of shaft samples (p < 0.0001). HPV16 was the most common type and 29.2% of men were infected with more than one HPV type. Risk factors for HPV infection included presence of C. trachomatis, N. gonorrhea, self-reported sexually transmitted infections, and less frequent bathing. Lifetime number of sexual partners and herpes simplex virus type-2 seropositivity were also marginally associated with HPV infection.

Scaling sexual behavior or "sexual risk propensity" among men at risk for HIV in Kisumu, Kenya.

We present a scale to measure sexual risk behavior or "sexual risk propensity" to evaluate risk compensation among men engaged in a randomized clinical trial of male circumcision. This statistical approach can be used to represent each respondent's level of sexual risk behavior as the sum of his responses on multiple dichotomous and rating scale (i.e. ordinal) items. This summary "score" can be used to summarize information on many sexual behaviors or to evaluate changes in sexual behavior with respect to an intervention. Our 18 item scale demonstrated very good reliability (Cronbach's alpha of 0.87) and produced a logical, unidimensional continuum to represent sexual risk behavior. We found no evidence of differential item function at different time points (except for reporting a concurrent partners when comparing 6 and 12 month follow-up visits) or with respect to the language with which the instrument was administered. Further, we established criterion validity by demonstrating a statistically significant association between the risk scale and the acquisition of incident sexually transmitted infections (STIs) at the 6 month follow-up and HIV at the 12 month follow-up visits. This method has broad applicability to evaluate sexual risk behavior in the context of other HIV and STI prevention interventions (e.g. microbicide or vaccine trials), or in response to treatment provision (e.g., anti-retroviral therapy).

Dermatophyte infections in primary school children in Kibera slums of Nairobi.

OBJECTIVE: To determine the prevalence and aetiology of dermatophyte infections in relation to social economic factors in primary school children in Kibera. DESIGN: A cross-sectional descriptive study. SETTING: City council sponsored schools namely Olympic, Kibera, Ayany and Mbagathi way all in Kibera, the largest of the informal settlement within Nairobi which is home to between 700,000-1,000,000 inhabitamts. The study was conducted between September 2006 and February 2007. SUBJECTS: A total of 422 primary school children from the ages of five years to 15 years were selected for the study. RESULTS: The prevalence of dermatophytoses was 11.2% with tinea capitis being the most common type while the grey patch form being the dominant clinical manifestation. There was a significant difference (p = 0.001) in dermatophytoses in different schools with Olympic primary school registering the highest prevalence (22.6%). The highest infection rate occurred among six to eight years age bracket in both sexes compared to other age brackets (p = 0.002). The genera of fungi associated with dermatophytoses were isolated indicating the number in each species as follows; T. violecium (35), T. mentagrophytes(3), T. terestre(3), T. schoenleinii(2), and T. interdigitale(1), M. canis(2), M. equinum(1) and E. flocossum(1). T. violecium was the predominant species isolated, at 35/48 (71%) followed by T. mentagrophytes and T. terrestre at 3/48 (6%) each. CONCLUSION: The study indicates high prevalence of 11.2% dermatophyte infection among the school children in Kibera. Factors contributing to the high frequency and chronic occurrences of ring worm in this area may include poor living environment, children interaction patterns and poor health seeking behaviour. There is need for health education and public awareness campaigns among the communities in urban informal settlements on healthy seeking behaviors and hygiene in order to reduce transmission and severe clinical manifestations.

A prospective study of risk factors for herpes simplex virus type 2 acquisition among high-risk HIV-1 seronegative women in Kenya.

OBJECTIVES: Several studies have demonstrated an association between herpes simplex virus type 2 (HSV-2) and HIV-1, but available data on risk factors for HSV-2 acquisition are limited. The objective of this analysis was to determine the incidence and risk factors for HSV-2 acquisition among HIV-1-seronegative female sex workers in Kenya. METHODS: Between February 1993 and December 2006, HIV-1-seronegative women attending a municipal sexually transmitted infection (STI) clinic were invited to enroll in a prospective cohort study. Screening for HIV-1 and STIs were done at monthly follow-up visits. Archived blood samples were tested for HSV-2. RESULTS: Of 1527 HIV-1-seronegative women enrolled, 302 (20%) were HSV-2 seronegative at baseline of whom 297 had at least one follow-up visit. HSV-2 incidence was high (23 cases/100 person-years; 115 cases). In multivariate analysis, HSV-2 was significantly associated with more recent entry into sex work, workplace and higher number of sex partners per week. Condom use was protective, although this was statistically significant only for the intermediate strata (25-75% condom use; HR 0.43; p = 0.05). There were statistical trends for bacterial vaginosis to increase HSV-2 risk (HR 1.56; p = 0.07) and for oral contraceptive use to decrease risk (HR 0.50; p = 0.08). The 23% annual HSV-2 incidence in this study is among the highest reported anywhere in the world. CONCLUSIONS: Women were at increased risk if they had recently entered sex work, had a higher number of sex partners or worked in bars. HSV-2 risk reduction interventions are urgently needed among high-risk African women.

Prospective study of correlates of vaginal Lactobacillus colonisation among high-risk HIV-1 seronegative women.

OBJECTIVE: Vaginal colonisation with Lactobacillus species is characteristic of normal vaginal ecology. The absence of vaginal lactobacilli, particularly hydrogen peroxide (H(2)O(2))-producing isolates, has been associated with symptomatic bacterial vaginosis (BV) and increased risk for HIV-1 acquisition. Identification of factors associated with vaginal Lactobacillus colonisation may suggest interventions to improve vaginal health. METHODS: We conducted a prospective cohort study of correlates of vaginal Lactobacillus colonisation among Kenyan HIV-1 seronegative female sex workers. At monthly follow-up visits, vaginal Lactobacillus cultures were obtained. Generalised estimating equations were used to examine demographic, behavioural and medical correlates of Lactobacillus isolation, including isolation of H(2)O(2)-producing strains. RESULTS: Lactobacillus cultures were obtained from 1020 women who completed a total of 8896 follow-up visits. Vaginal washing, typically with water alone or with soap and water, was associated with an approximately 40% decreased likelihood of Lactobacillus isolation, including isolation of H(2)O(2)-producing strains. Recent antibiotic use, excluding metronidazole and treatments for vaginal candidiasis, reduced Lactobacillus isolation by approximately 30%. H(2)O(2)-producing lactobacilli were significantly less common among women with Trichomonas vaginalis infection and those who were seropositive for herpes simplex virus type 2. In contrast, H(2)O(2)-producing lactobacilli were significantly more common among women with concurrent vaginal candidiasis. CONCLUSIONS: Modifiable biological and behavioural factors are associated with Lactobacillus colonisation in African women. Our results suggest intervention strategies to improve vaginal health in women at high risk for HIV-1.

Herpes simplex virus type 2 antibody detection performance in Kisumu, Kenya, using the Herpeselect ELISA, Kalon ELISA, Western blot and inhibition testing.

BACKGROUND: In certain parts of Africa, type-specific herpes simplex virus type 2 (HSV-2) ELISAs may have limited specificity. To date, no study has been conducted to validate HerpeSelect and Kalon type-specific HSV-2 ELISAs using both the Western blot and recombinant gG ELISA inhibition testing as reference standards. METHODS: A total of 120 men who were HIV seronegative (aged 18-24 years) provided blood samples. HSV-2 IgG serum antibodies were detected using four different methods: HerpeSelect HSV-2 ELISA (n = 120), Kalon HSV-2 ELISA (n = 120), University of Washington Western blot (n = 101) and a recombinant inhibition test (n = 93). RESULTS: HSV-2 seroprevalence differed significantly by HSV-2 detection method, ranging from 24.8% with the Western blot to 69.8% with the HerpeSelect ELISA. Using the Western blot as the reference standard, the HerpesSelect had the highest sensitivity for HSV-2 antibody detection (100%) yet lowest specificity (40%). Similar results were obtained using the inhibition test as the reference standard. The sensitivity and specificity of the Kalon test versus the Western blot were 92% and 79%, respectively, and 80% and 82% versus the inhibition test. Using the inhibition test as the reference standard, the sensitivity of the Western blot appeared low (49%). CONCLUSIONS: In men in western Kenya who were HIV seronegative, the HerpeSelect and Kalon type-specific ELISAs had high sensitivities yet limited specificities using the Western blot as reference standard. Overall, the Kalon ELISA performed better than the HerpeSelect ELISA in these young men from Kisumu. Further understanding is needed for the interpretation of HSV-2 inhibition or ELISA test positive/ Western blot seronegative results. Before HSV-2 seropositivity may be reliably reported in selected areas of Africa, performance studies of HSV-2 serological assays in individual geographical areas are recommended.

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.

Risk compensation is not associated with male circumcision in Kisumu, Kenya: a multi-faceted assessment of men enrolled in a randomized controlled trial.

BACKGROUND: Three randomized controlled trials (RCTs) have confirmed that male circumcision (MC) significantly reduces acquisition of HIV-1 infection among men. The objective of this study was to perform a comprehensive, prospective evaluation of risk compensation, comparing circumcised versus uncircumcised controls in a sample of RCT participants. METHODS AND FINDINGS: Between March 2004 and September 2005, we systematically recruited men enrolled in a RCT of MC in Kenya. Detailed sexual histories were taken using a modified Timeline Followback approach at baseline, 6, and 12 months. Participants provided permission to obtain circumcision status and laboratory results from the RCT. We evaluated circumcised and uncircumcised men's sexual behavior using an 18-item risk propensity score and acquisition of incident infections of gonorrhea, chlamydia, and trichomoniasis. Of 1780 eligible RCT participants, 1319 enrolled (response rate = 74%). At the baseline RCT visit, men who enrolled in the sub-study reported the same sexual behaviors as men who did not. We found a significant reduction in sexual risk behavior among both circumcised and uncircumcised men from baseline to 6 (p<0.01) and 12 (p = 0.05) months post-enrollment. Longitudinal analyses indicated no statistically significant differences between sexual risk propensity scores or in incident infections of gonorrhea, chlamydia, and trichomoniasis between circumcised and uncircumcised men. These results are based on the most comprehensive analysis of risk compensation yet done. CONCLUSION: In the context of a RCT, circumcision did not result in increased HIV risk behavior. Continued monitoring and evaluation of risk compensation associated with circumcision is needed as evidence supporting its' efficacy is disseminated and MC is widely promoted for HIV prevention.

Herpes simplex virus type 2 infection among young uncircumcised men in Kisumu, Kenya.

OBJECTIVES: To identify factors associated with herpes simplex virus type 2 (HSV-2) infection among men aged 18-24 in Kisumu, Kenya. METHODS: Baseline data from a randomised trial of male circumcision were analysed. Participants were interviewed for sociodemographic and behavioural risks. The outcome was HSV-2 by antibody status. Risk factors were considered singly and in combination through logistic regression models. RESULTS: Among 2771 uncircumcised men, 766 (27.6%; 95% confidence interval (CI) 26.0% to 29.3%) tested antibody positive for HSV-2. The median age at first sex was 16 years, and the median number of lifetime sexual partners was four. HSV-2 seroprevalence increased from 19% among 18-year-olds to 43% among 24-year-olds (p<0.001). In multivariable analysis, statistically significant risks for infection were increasing age (adjusted odds ratio (AOR) = 1.22-2.58), being married or having a live-in female partner (AOR = 1.80; 95% CI 1.28 to 2.53), preferring "dry" sex (AOR = 1.39; 95% CI 1.14 to 1.69), reported penile cuts or abrasions during sex (AOR = 1.58; 95% CI 1.32 to 1.91), increasing lifetime sex partners (multiple response categories; AORs ranging from 1.65 to 1.97), and non-student occupation (multiple response categories; AORs ranging from 1.44 to 1.93). Risk decreased with reported condom used at last sex (AOR = 0.82; 95% CI 0.68 to 0.99). CONCLUSION: Primary prevention efforts should be initiated at an early age. The same behavioural interventions used currently for HIV prevention-abstinence, reducing the number of sex partners and increasing condom use-should be effective for HSV-2 prevention.

Human papillomavirus detection by penile site in young men from Kenya.

BACKGROUND: Limited data are available on whether sampling from the penile shaft or urethra increases detection of penile HPV infection in men beyond that found in the glans and coronal sulcus. METHODS: Within a randomized clinical trial, a validation study of penile sampling was conducted in Kisumu, Kenya. Young men (18-24 years) were invited to provide penile exfoliated cells using prewetted Dacron swabs to determine the best site for HPV detection. beta-Globin gene PCR and HPV DNA type GP5+/6+ PCR status were ascertained from 3 anatomical sites. RESULTS: A total of 98 young HIV-seronegative, uncircumcised men participated. Penile HPV prevalence varied by anatomical site: 50% in penile exfoliated cells from the glans, coronal sulcus, and inner foreskin tissue; 43% in the shaft and external foreskin tissue; and 18% in the urethra (P <0.0001). For each anatomical site, over 87% of samples were beta-globin positive. Beyond that found in the glans/coronal sulcus, urethral sampling resulted in no increase in HPV positivity and shaft sampling resulted in an additional 7.3% of overall HPV positivity. The prevalence of high-risk HPV positivity varied by anatomical site: 39% in glans/coronal sulcus, 31% in shaft, and 13% in the urethra (P <0.0001). HPV 16 was the most common type identified. DISCUSSION: Penile HPV prevalence was approximately 50% among young men in Kisumu, Kenya. Urethral sampling for HPV detection in men added no sensitivity for HPV detection over that found from sampling the glans/coronal sulcus and penile shaft. These data will help inform studies on HPV transmission dynamics, and on the efficacy of HPV prophylactic vaccines on penile HPV carriage in men.

A nested case-control study of sexual practices and risk factors for prevalent HIV-1 infection among young men in Kisumu, Kenya.

OBJECTIVES: To investigate sexual practices and risk factors for prevalent HIV infection among young men in Kisumu, Kenya. GOAL: The goal of this study was to identify behaviors associated with HIV in Kisumu to maximize the effectiveness of future prevention programs. STUDY DESIGN: Lifetime sexual histories were collected from a nested sample of 1337 uncircumcised participants within the context of a randomized controlled trial of male circumcision to reduce HIV incidence. RESULTS: Sixty-five men (5%) tested positive for HIV. Multiple logistic regression revealed the following independent predictors of HIV: older age, less education, being married, being Catholic, >4 lifetime sex partners, prior treatment for an STI, sex during partner's menstruation, ever practicing bloodletting, and receipt of a medical injection in the last 6 months. Prior HIV testing and postcoital cleansing were protective. CONCLUSIONS: This analysis confirms the importance of established risk factors for HIV and identifies practices that warrant further investigation.

Adult male circumcision outcomes: experience in a developing country setting.

INTRODUCTION: We examined male circumcision outcomes among young adults in an African setting. MATERIALS AND METHODS: Participants were healthy, sexually active, uncircumcised, HIV-seronegative males aged 18-24 years. The main outcomes measured included complications, healing, satisfaction and resumption of activities. RESULTS: Of 1,475 procedures, 26 (1.8%) were associated with 27 adverse events, most commonly wound disruption/delayed healing (0.6%), wound infection (0.4%), and bleeding (0.3%). Adverse events per clinician averaged 3.8 and 2.1% for procedures 1-100 and 101-200, respectively, and <1% for procedures 201-300, 301-400 and >400, respectively (p < 0.001). Participants resumed normal general activities after a median of 1 postoperative day and 93% with regular employment resumed working within 1 week. After 30 days, 99% of participants reported being very satisfied. After 90 days, 65% reported having had sex, 45% reported that their partners had expressed an opinion, 92% of whom were very satisfied with the outcome. CONCLUSIONS: Safe and acceptable adult male circumcision services can be delivered in developing country settings.

HIV-1 target cells in foreskins of African men with varying histories of sexually transmitted infections.

Numerous epidemiologic studies have found significant associations between lack of circumcision and HIV-1 acquisition in men. To our knowledge, this is the first study of human foreskin tissue that examines biologic mechanisms that increase susceptibility of uncircumcised African men to HIV-1. Foreskin specimens from 20 men with and 19 men with no history of sexually transmitted infections were examined for HIV-1 target cells. Most Langerhans cells were found in the epithelium; most CD4+ T cells and macrophages were in the submucosa. There were no differences in HIV-1 target cells between men with and those without history of sexually transmitted infections. However Langerhans cells and macrophages were more abundant in the group with a history of infection. The densities and positions of HIV-1 target cells in the foreskin tissue of these Kenyan men indicate that the inner mucosal surface of the human foreskin contains cells that make it highly susceptible to HIV infection.

No evidence for rapid subtype C spread within an epidemic in which multiple subtypes and intersubtype recombinants circulate.

There are multiple subtypes of HIV-1 circulating worldwide, but recently, subtype C has become highly prevalent, particularly in certain geographic regions. It is unclear whether the dominance of subtype C or other subtypes is due to increased fitness of certain subtypes for transmission, or a founder effect in new, rapidly growing epidemics. To examine whether the prevalence of one subtype increases over the course of an expanding epidemic that includes several circulating subtypes, we examined the distribution of HIV-1 subtypes in Kenya from 1986 to 2000. We found no evidence for an increase in the prevalence of subtype C, which remained low throughout this approximately 15-year period. Interestingly, the percentage of subtype D present in the population decreased significantly over that period, with a slight increase in subtype A. Throughout that period, intersubtype recombinant viruses were detected, including at the early stages of the epidemic. This latter finding suggests that reinfection may have occurred in high-risk groups early in the epidemic, leading to intersubtype recombinant viruses that underwent secondary spread.

Traditional healers and the management of sexually transmitted diseases in Nairobi, Kenya.

To describe the role of traditional healers in STD case management, in-depth interviews were held with 16 healers (seven witchdoctors, five herbalists and four spiritual healers) in four slum areas in Nairobi, Kenya. All healers believed that STDs are sexually transmitted and recognized the main symptoms. The STD-caseload varied largely, with a median of one patient per week. Witchdoctors and herbalists dispensed herbal medication for an average of seven days, whereas spiritual healers prayed. Thirteen healers gave advice on sexual abstinence during treatment, 11 on contact treatment, four on faithfulness and three on condom use. All healers asked patients to return for review and 13 reported referring patients whose conditions persist to public or private health care facilities. Thus, traditional healers in Nairobi play a modest but significant role in STD management. Their contribution to STD health education could be strengthened, especially regarding the promotion of condoms and faithfulness.

Prevalence of methicillin-resistant Staphylococcus aureus in eight African hospitals and Malta.

Methicillin-resistant Staphylococcus aureus (MRSA) poses a serious therapeutic problem worldwide, and its frequency in most African countries has not been reported. This study was aimed at determining the prevalence and antibiotic susceptibility patterns of MRSA in eight large hospitals (>500 beds) in Africa and Malta, from 1996 to 1997. Susceptibility to methicillin (oxacillin) and to other drugs was determined by E test (AB Biodisk, Solna, Sweden) on a total of 1440 clinical isolates of S. aureus. Methicillin resistance was detected in 213 (15%) of the 1440 isolates tested. The rate of MRSA was relatively high in Nigeria, Kenya, and Cameroon (21-30%), and below 10% in Tunisia, Malta, and Algeria. All MRSA isolates were sensitive to vancomycin, with MICs 60%) of MRSA strains were multiresistant. There is a need to maintain surveillance and control of MRSA infections in Africa.

Evaluation of a proposed clinical case definition of paediatric acquired immune deficiency syndrome.

OBJECTIVE: To evaluate the proposed criteria against the laboratory parameters and to identify the clinical features with the highest predictive value in the diagnosis of paediatric AIDS. DESIGN: A cross sectional study. SETTING: Kenyatta National Hospital, Nairobi. RESULTS: More than twenty three per cent of the children studied were seropositive and 14% were diagnosed as having AIDS. Almost 70% of the children studied were below 24 months. AIDS was significantly associated with mouth lesions, both ulcers and oral candidiasis, skin lesions especially eczema and generalised pruritic dermatitis, prolonged cough, prolonged fever and generalised lymphadenopathy. The WHO criteria had a sensitivity of 60%, a specificity of 94%, positive predictive value of 60%, and negative predictive value of 94%. The Nairobi diagnostic criteria had a sensitivity of 80%, a specificity of 79%, a positive predictive value of 38% and a negative predictive value of 96%. CONCLUSION: The Nairobi Diagnostic Criteria are superior to the WHO criteria as a screening test due to their higher sensitivity, 80% against 60% for WHO.

HLA-A and HLA-B in Kenya, Africa: allele frequencies and identification of HLA-B*1567 and HLA-B*4426.

HLA-A and HLA-B alleles of a population from Kenya, Africa were examined by sequencing exon 2 and exon 3 DNA and typing using a Taxonomy-based Sequence-analysis (TBSA) method. Extensive diversities were observed at both HLA-A and HLA-B loci in this population. Forty-one HLA-A alleles were identified from 159 unrelated individuals. The most frequently observed alleles were A*6802 (11.64%), A*02011/09 (9.75%), A*7401/02 (9.43%), A*3001 (7.86%), A*3002 (7.23%) and A*3601 (6.6%). Forty-nine HLA-B alleles were identified in 161 unrelated individuals, including two novel alleles, B*1567 and B*4426. The most frequently observed HLA-B alleles were B*5301 (9.01%), B*5801 (8.38%), B*4201 (7.76%), B*1503 (7.14%), B*1801 (6.21%), and B*5802 (5.90%). The most frequently observed HLA-A-B haplotypes were A*3601-B*5301 (3.55%) and A*3001-B*4201 (3.19%), followed by A*7401/02-B*5801 (2.84%), A*7401/02-B*5802 (2.84%) and A*02011/09-B*1503 (2.13%). Linkage disequilibrium and chi2 analysis showed the association of these HLA-A-B haplotypes at the antigen level to be significant. The frequencies of HLA-A and HLA-B alleles from the Kenyan population were compared with that of a population from Cameroon. The difference in allele and haplotype frequency distributions partly reflected the different ethnic composition of these two African populations.