Oliver Hoffmann

CD8 T-Cell Recognition of Multiple Epitopes within Specific Gag Regions Is Associated with Maintenance of a Low Steady-State Viremia in Human Immunodeficiency Virus Type 1-Seropositive Patients

ABSTRACT The importance of HLA class I-restricted CD8 T-cell responses in the control of human immunodeficiency virus (HIV) infection is generally accepted. While several studies have shown an association of certain HLA class I alleles with slower disease progression, it is not fully established whether this effect is mediated by HIV-specific CD8 T-cell responses restricted by these alleles. In order to study the influence of the HLA class I alleles on the HIV-specific CD8 T-cell response and on viral control, we have assessed HIV-specific epitope recognition, plasma viral load, and expression of HLA class I alleles in a cohort of HIV-seropositive bar workers. Possession of the HLA class I alleles B5801, B8101, and B0702 was associated with a low median viral load and simultaneously with a broader median recognition of Gag epitopes compared to all other HLA alleles (twofold increase) (P = 0.0035). We further found an inverse linear relationship between the number of Gag epitopes recognized and the plasma viral load (R = −0.36; P = 0.0016). Particularly, recognition of multiple epitopes within two regions of Gag (amino acids [aa] 1 to 75 and aa 248 to 500) was associated with the maintenance of a low steady-state viremia, even years after acute infection.

Decline in sexually transmitted infection prevalence and HIV incidence in female barworkers attending prevention and care services in Mbeya Region, Tanzania

Objective:To assess trends in sexually transmitted infection (STI) prevalence and HIV incidence and associated factors in a cohort of female barworkers exposed to behavioural interventions and STI screening and treatment. Methods:An open cohort of 600 female barworkers in Mbeya Region, Tanzania was offered 3-monthly information and education sessions on HIV/STI and reproductive health, voluntary HIV counselling and testing and clinical health check-ups including STI syndromic management with simple STI laboratory support. Outcome assessments included HIV, herpes simplex virus type 2 (HSV-2) and syphilis serology, polymerase chain reaction for Neisseria gonorrhoeae, Chlamydia trachomatis and ulcerative STI, microscopy for Trichomonas vaginalis, Candida albicans and bacterial vaginosis and interviews on sociodemographic and behavioural characteristics. Results:Over a period of 30 months 600 barworkers were enrolled at the baseline examination round and 153 thereafter as replacements for losses to follow-up. At 3-monthly examinations the prevalence of gonorrhoea declined steadily from 22.2 to 6.8% (odds ratio for trend per quarter: 0.81; P < 0.001). The prevalence of all other STI/RTI, except for genital herpes and bacterial vaginosis, also decreased significantly. HIV incidence declined from 13.9/100 to 5.0/100 person-years over three consecutive 9-month periods. HIV incidence was significantly associated with genital ulcers and positive syphilis serology, but not with genital herpes or HSV-2 seropositivity. Conclusion:A relatively simple intervention consisting of regular 3-monthly STI screening and syndromic management in combination with HIV/STI information and counselling sessions was well accepted and effective in reducing STI among barworkers. Such interventions should be implemented more widely in high-risk environments in sub-Saharan Africa.

HIV Type 1 Subtypes among Blood Donors in the Mbeya Region of Southwest Tanzania

HIV-1 is endemic in Tanzania where three different subtypes, A, C, and D, have been identified. Information on HIV-1 genetic diversity is crucial to define requirements for an effective vaccine, in regions where HIV-1 vaccine trials are planned. To define the subtype distribution of HIV-1 in the Mbeya region of southwest Tanzania, peripheral blood mononuclear cells (PBMC) and plasma were obtained from 36 discarded HIV seropositive blood units. Multiregion hybridization assay (MHA) was performed on both PBMC DNA and plasma RNA to determine the subtype distribution. Twenty virtually full-length HIV-1 sequences were amplified from the extracted DNA, sequenced, and phylogenetically analyzed. Subtype distribution determined by all three assays was comparable. More than 50% of the samples analyzed were subtype C, followed by a high proportion of subtype C-containing intersubtype recombinants. Based on this work, subtype C appears to be the prevalent subtype in southwest Tanzania, followed by a high proportion of intersubtype recombinants.

HIV-1 diversity and prevalence differ between urban and rural areas in the Mbeya region of Tanzania

Objective:To characterize HIV-1 strains in a potential vaccine trial cohort (CODE) in the Mbeya region of southwest Tanzania. Design:Study volunteers (n = 3096) were recruited from urban areas in Mbeya Town, using two different recruitment strategies, and in a nearby rural village. Methods:Cryopreserved plasma from 507 HIV-1 prevalent cases was the source of viral RNA for HIV-1 genotyping by the Multi-region Hybridization Assay, the MHAacd, and selected strains were confirmed by complete genome sequencing. Results:The overall HIV-1 prevalence was 16.6% [95% confidence interval (CI), 15.3–17.9] within the cohort. HIV-1 prevalence was higher among women, and in urban areas. Recruitment through advertisement targeted a high-risk urban male population for HIV-1 infection [adjusted odds ratio (adj. OR), 1.68; 95% CI, 1.13–2.51] when compared with men recruited door-to-door. The complexity of the HIV-1 epidemic was also higher in urban areas evidenced by the high-risk of HIV-1 infection with a recombinant strain (adj. OR, 2.69; 95% CI, 1.08–6.69) and HIV-1 dual infection (adj. OR, 5.16; 95% CI, 1.07–24.9), mainly driven by urban men recruited through advertisement. Conclusions:Overall the urban epidemic was more genetically complex, with higher prevalence and more recombinants and dual infections. Vaccine trials in Mbeya region can assess a complex HIV-1 population dynamic and determine vaccine efficacy in relationship to the genetic diversity of HIV-1 strains that challenge vaccines.

In-Depth, Longitudinal Analysis of Viral Quasispecies from an Individual Triply Infected with Late-Stage Human Immunodeficiency Virus Type 1, Using a Multiple PCR Primer Approach

ABSTRACT Coinfections with more than one human immunodeficiency virus type 1 (HIV-1) subtype appear to be the source of new recombinant strains and may be commonplace in high-risk cohorts exposed to multiple subtypes. Many potential dual infections have been identified during the HIV Superinfection Study in Mbeya, Tanzania, where 600 female bar workers who are highly exposed to subtypes A, C, and D have been evaluated every 3 months for over 3 years by use of the MHAacd HIV-1 genotyping assay. Here we describe an in-depth, longitudinal analysis of the viral quasispecies in a woman who was triply infected with HIV-1 and who developed AIDS and passed away 15 months after enrollment. The MHA results obtained at 0, 3, 6, 9, and 12 months revealed dual-probe reactivities and shifts in subtype over time, indicating a potential dual infection and prompting further investigation. The multiple infection was confirmed by PCR amplification of three genome regions by a multiple primer approach, followed by molecular cloning and sequencing. A highly complex viral quasispecies was found, including several recombinant forms, with vpu/gp120 being the most diverse region. A significant fluctuation in molecular forms over time was observed, showing that the serial sample format is highly desirable, if not essential, for the identification of multiple infections. In a separate experiment, we confirmed that the detection of coinfections is more efficient with the use of multiple amplification primers to overcome the primer bias that results from the enormous diversity in the HIV-1 genome.

Viral and host factors associated with the HIV-1 viral load setpoint in adults from Mbeya region, Tanzania.

Background:The viral load setpoint (VLS) is an important predictor of HIV disease progression, but there is a lack of information regarding the VLS and its possible determinants in African populations. Methods:Initially HIV-negative adults from 3 distinct groups (female bar workers, females, and males from the general population) were followed for up to 4 years. The VLS was calculated for 108 seroconverters and associations of the VLS with possible risk factors were analyzed using univariate and multivariate regression. Results:The median VLS for female bar workers, females, and males from the general population were 69,850, 28,600, and 158,000 RNA copies per milliliter, respectively. Significant associations with an elevated viral load were observed for male gender [risk ratio (RR) = 1.83, 95% confidence interval (95% CI) = 1.14 to 2.93], the expression of harmful HLA I alleles (RR = 1.73, 95% CI = 1.13 to 2.66) and multiple infection with different HIV-1 subtypes (RR = 1.65, 95% CI = 1.03 to 2.66). Bar workers were considerably more often infected with different HIV-1 subtypes than participants from the general population. Conclusions:Our study confirms that gender and the expression of different HLA class I alleles are important determinants of the viremia at VLS, and it also corroborates an earlier finding that multiple infection with different HIV-1 subtypes is associated with a higher VLS.

Risk factors for HIV-1 infection in a longitudinal, prospective cohort of adults from the Mbeya Region, Tanzania.

Background:To control the global HIV epidemic, targeted interventions to reduce the incidence of HIV infections are urgently needed until an effective HIV vaccine is available. This study describes HIV-1 incidence and associated risk factors in a general population cohort of adults from Mbeya region, Tanzania, who participated in a vaccine preparedness study. Methods:We conducted a closed prospective cohort study with 6-monthly follow-up from 2002 to 2006 enrolling adults from the general population. HIV-1 incidence and risk factors for HIV-1 acquisition were analyzed using Cox regression. Results:We observed 2578 seronegative participants for a mean period of 3.06 person years (PY) (7471 PY in total). Overall HIV-1 incidence was 1.35 per 100 PY (95% confidence interval [CI], 1.10-1.64/100 PY). The highest overall HIV-1 incidence was found in females from Itende village (1.55 per 100 PY; 95% CI, 0.99-2.30/100 PY); the highest age-specific incidence was observed in semiurban males aged 30 to 34 years (2.75 per 100 PY; 95% CI, 0.75-7.04). HIV-1 acquisition was independently associated with female gender (hazard ratio [HR], 1.64; 95% CI, 1.05-2.57), younger age at enrollment (age 18-19 versus 35-39 years: HR, 0.29; 95% CI, 0.11-0.75), alcohol consumption (almost daily versus none: HR, 2.01; 95% CI, 1.00-4.07), education level (secondary school versus none: HR, 0.39; 95% CI, 0.17-0.89), and number of lifetime sex partners (more than five versus one: HR, 2.22; 95% CI, 1.13-4.36). Conclusions:A high incidence of HIV was observed in this cohort, and incident infection was strongly associated with young age, alcohol consumption, low school education level, and number of sex partners. Targeted interventions are needed to address the elevated risk associated with these factors.

A high viral burden predicts the loss of CD8 T-cell responses specific for subdominant gag epitopes during chronic human immunodeficiency virus infection.

ABSTRACT Human immunodeficiency virus (HIV)-specific CD8 T-cell responses targeting products encoded within the Gag open reading frame have frequently been associated with better viral control and disease outcome during the chronic phase of HIV infection. To further clarify this relationship, we have studied the dynamics of Gag-specific CD8 T-cell responses in relation to plasma viral load and time since infection in 33 chronically infected subjects over a 9-month period. High baseline viral loads were associated with a net loss of breadth (P < 0.001) and a decrease in the total magnitude of the Gag-specific T-cell response in general (P = 0.03). Most importantly, the baseline viral load predicted the subsequent change in the breadth of Gag recognition over time (P < 0.0001, r2 = 0.41). Compared to maintained responses, lost responses were low in magnitude (P < 0.0001) and subdominant in the hierarchy of Gag-specific responses. The present study indicates that chronic exposure of the human immune system to high levels of HIV viremia is a determinant of virus-specific CD8 T-cell loss.

Defining the human immunodeficiency virus type 1 transmission genetic bottleneck in a region with multiple circulating subtypes and recombinant forms

The Mbeya region of Tanzania has a genetically complex HIV epidemic with multiple subtypes and recombinant forms circulating, together with a high frequency of dual infections with more than one subtype. This study aimed to determine whether this impacted the HIV-1 transmission bottleneck. A total of 210 env sequences from 22 participants were generated from recently infected women from Mbeya using the single genome amplification approach. Participants were infected with subtypes C (n=9), A (n=4), or D (n=1), and recombinants AC (n=4), CD (n=2), AD (n=1), or ACD (n=1). Sixteen participants (73%) were infected with a single variant; five (23%) with multiple variants; and one (4%) was dually infected. Thus the frequency of single variant infections was similar to cohorts located in genetically restricted subtype B or C epidemics, suggesting that multiple circulating subtypes and unique recombinant forms do not have a significant impact on the transmission bottleneck.

Possible reasons for an increase in the proportion of genital ulcers due to herpes simplex virus from a cohort of female bar workers in Tanzania

Objectives: To determine trends in the prevalence and aetiological distribution of genital ulcer syndrome (GUS) in a cohort of female bar workers and to assess factors associated with these trends. Methods: An open cohort of 600 women at high risk of HIV and sexually transmitted infection (STI) was offered screening and treatment for STI at 3-month intervals. The prevalence of GUS and associated aetiological agents (Herpes simplex virus (HSV), Treponema pallidum and Haemophilus ducreyi) were monitored over 27 months through clinical examination, dry lesion swabbing and multiplex polymerase chain reaction. The effects of HIV status and other factors on the prevalence trends of STI were assessed. Results: A total of 753 women were recruited into the cohort over 10 examination rounds. At recruitment, the seroprevalence was 67% for HIV and 89% for HSV type 2 (HSV-2). During follow-up, 57% of ulcers had unknown aetiology, 37% were due to genital herpes and 6% to bacterial aetiologies, which disappeared completely in later rounds. The absolute prevalence of genital herpes remained stable at around 2%. The proportion of GUS caused by HSV increased from 22% to 58%, whereas bacterial causes declined. These trends were observed in both HIV-negative and HIV-positive women. Conclusions: The changes observed in the frequency and proportional distribution of GUS aetiologies suggest that regular STI screening and treatment over an extended period can effectively reduce bacterial STI and should therefore be sustained. However, in populations with a high prevalence of HSV-2, there remains a considerable burden of genital herpes, which soon becomes the predominant cause of GUS. Given the observed associations between genital herpes and HIV transmission, high priority should be given to the evaluation of potential interventions to control HSV-2 either through a vaccine or through episodic or suppressive antiviral therapy and primary prevention.