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Abstract Background For more than three decades, Human Immunodeficiency Virus (HIV) infection and Acquired Immune Deficiency Syndrome (AIDS) continue to dominate the health agenda. In sub-Saharan African countries, women are at more risk of contracting HIV and AIDS compared with men due to biological, social, economic, socio-economic and cultural factors. Women in the uniformed services may be more vulnerable to HIV/AIDS because of their work context, mobility, age and other factors that expose them to a higher risk of infection than women in the general population. This article describes gender dimensions, motives and challenges towards HIV prevention amongst Police officers (POs) in Dar es Salaam, Tanzania. Methods This was a descriptive qualitative study conducted at Police stations in Dar es Salaam, Tanzania. Fifteen in-depth interviews were conducted on POs; seven men, and eight women. Content analysis approach was used to analyze data. Results Participants’ self-descriptions shed light on gender differences in relation to self -perceptions, job contexts, sexual relationships and HIV prevention. Both men and women perceived themselves as role models, and believed that the surrounding community perceived the same. Safe sexual behavior appeared crucial to avoid undesirable health outcomes. Risky sexual practices were considered avoidable. Under unavoidable sexual temptations, women in particular would be keen to avoid risky sexual practices. Some participants expressed positive views towards condoms use during extra-marital sexual relationships, while others had negative opinions. Early phases of HIV vaccine trials appeared to gain support from sexual partners. However, condom use during phase I/II HIV vaccine trials was deemed as difficult. Support from the spouse was reported to influence condom use outside the wedlock. However, religious beliefs, socio-cultural issues and individual reasons were perceived as difficulties to promote condoms use. Conclusions These findings increase understanding of gender differences and context specific efforts towards HIV prevention. Individuals’ assertiveness against risky sexual practices and the intention to participate in HIV vaccine trials to develop an effective vaccine are worth noting. Nevertheless, uncertainties towards condoms use underscore the importance of condoms’ marketing particularly in extra marital sexual relationships and during early HIV vaccine trials.

The secondary analyses for correlates of risk of infection in the RV144 HIV-1 vaccine trial implicated vaccine-induced antibody-dependent cellular cytotoxicity (ADCC) responses in the observed protection, highlighting the importance of assessing such responses in ongoing and future HIV-1 vaccine trials. However, in vitro assays that detect ADCC activity in plasma from HIV-1 infected seropositive individuals are not always effective at detecting ADCC activity in plasma from HIV-1 vaccine recipients. In vivo, ADCC-mediating antibodies must operate at the site of infection, where effector cells are recruited and activated by a local milieu of chemokines and cytokines. Based on previous findings that interleukin 15 (IL-15) secretion increases during acute HIV-1 infection and enhances NK cell-mediated cytotoxicity, we hypothesized that IL-15 pretreatment of NK effector cells could be used to improve killing of infected cells by vaccine-induced antibodies capable of mediating ADCC. Using the HIV-1 infectious molecular clone (IMC)-infected target cell assay along with plasma samples from HIV-1 vaccine recipients, we found that IL-15 treatment of effector cells improved the ability of the vaccine-induced antibodies to recruit effector cells for ADCC. Through immunophenotyping experiments, we showed that this improved killing was likely due to IL-15 mediated activation of NK effector cells and higher intracellular levels of perforin and granzyme B in the IL-15 pretreated NK cells. We also found that using a 4-fold dilution series of plasma and subtraction of pre-vaccination responses resulted in lowest response rates among placebo recipients and significant separation between treatment groups. This represents the first attempt to utilize IL-15-treated effector cells and optimized analytical approaches to improve the detection of HIV-1 vaccine-induced ADCC responses and will inform analyses of future HIV vaccine clinical trials.

The secondary analyses for correlates of risk of infection in the RV144 HIV-1 vaccine trial implicated vaccine-induced antibody-dependent cellular cytotoxicity (ADCC) responses in the observed protection, highlighting the importance of assessing such responses in ongoing and future HIV-1 vaccine trials. However, in vitro assays that detect ADCC activity in plasma from HIV-1 infected seropositive individuals are not always effective at detecting ADCC activity in plasma from HIV-1 vaccine recipients. In vivo , ADCC-mediating antibodies must operate at the site of infection, where effector cells are recruited and activated by a local milieu of chemokines and cytokines. Based on previous findings that interleukin 15 (IL-15) secretion increases during acute HIV-1 infection and enhances NK cell-mediated cytotoxicity, we hypothesized that IL-15 pretreatment of NK effector cells could be used to improve killing of infected cells by vaccine-induced antibodies capable of mediating ADCC. Using the HIV-1 infectious molecular clone (IMC)-infected target cell assay along with plasma samples from HIV-1 vaccine recipients, we found that IL-15 treatment of effector cells improved the ability of the vaccine-induced antibodies to recruit effector cells for ADCC. Through immunophenotyping experiments, we showed that this improved killing was likely due to IL-15 mediated activation of NK effector cells and higher intracellular levels of perforin and granzyme B in the IL-15 pretreated NK cells. We also found that using a 4-fold dilution series of plasma and subtraction of pre-vaccination responses resulted in lowest response rates among placebo recipients and significant separation between treatment groups. This represents the first attempt to utilize IL-15-treated effector cells and optimized analytical approaches to improve the detection of HIV-1 vaccine-induced ADCC responses and will inform analyses of future HIV vaccine clinical trials. [ABSTRACT FROM AUTHOR]

Abstract Background The search for an efficacious HIV vaccine is a global priority. To date only one HIV vaccine trial (RV144) has shown modest efficacy in a phase III trial. With existing different HIV-1 subtypes and frequent mutations, multiple trials are needed from different geographical sites particularly in sub-Saharan Africa where most HIV infections occur. Thus, motivations to participate in HIV vaccine trials among Tanzanians need to be assessed. This paper describes the motives of Police Officers who showed great interest to volunteer in HIVIS-03 in Dar es Salaam, Tanzania. Methods A descriptive cross-sectional study was conducted among Police Officers who showed interest to participate in the HIVIS-03, a phase I/II HIV vaccine trial in Dar es Salaam. Prior to detailed training sessions about HIV vaccine trials, the potential participants narrated their individual motives to participate in the trial on a piece of paper. Descriptive analysis using content approach and frequency distributions were performed. Results Of the 265 respondents, 242 (91.3 %) provided their socio-demographic characteristics as well as reasons that would make them take part in the proposed trial. Majority, (39.7 %), cited altruism as the main motive. Women were more likely to volunteer due to altruism compared to men (P

For survival data, mark variables are only observed at uncensored failure times, and it is of interest to investigate whether there is any relationship between the failure time and the mark variable. The additive hazards model, focusing on hazard differences rather than hazard ratios, has been widely used in practice. In this article, we propose a mark-specific additive hazards model in which both the regression coefficient functions and the baseline hazard function depend nonparametrically on a continuous mark. An estimating equation approach is developed to estimate the regression functions, and the asymptotic properties of the resulting estimators are established. In addition, some formal hypothesis tests are constructed for various hypotheses concerning the mark-specific treatment effects. The finite sample behavior of the proposed estimators is evaluated through simulation studies, and an application to a data set from the first HIV vaccine efficacy trial is provided. [ABSTRACT FROM AUTHOR]

Questions arise concerning participants’ motives in risky studies, such as HIV vaccine trials (HVTs). We interviewed in-depth 20 gay/bisexual men. Participants described both altruistic and nonaltruistic motives. Altruistic motivations emerged primarily, with nine typologies: (a) cultural, (b) community related, (c) familial, (d) religious, (e) professional, (f) political (e.g., HIV activism), (g) moral (e.g., making up for past wrongs), (h) existential (e.g., providing sense of meaning), and (i) other psychological (e.g., emotional gratification). Views of compensation varied: not a factor (55%), added incentive (25%), main motivator, but in conjunction with altruism (15%), and primary motivator (5%). HVT participants thus often have both altruistic and financial motives, and related typologies emerged. These findings have critical implications for studies on HIV, other conditions, and research ethics. [ABSTRACT FROM AUTHOR]

Background: The search for an efficacious HIV vaccine is a global priority. To date only one HIV vaccine trial (RV144) has shown modest efficacy in a phase III trial. With existing different HIV-1 subtypes and frequent mutations, multiple trials are needed from different geographical sites particularly in sub-Saharan Africa where most HIV infections occur. Thus, motivations to participate in HIV vaccine trials among Tanzanians need to be assessed. This paper describes the motives of Police Officers who showed great interest to volunteer in HIVIS-03 in Dar es Salaam, Tanzania.Methods: A descriptive cross-sectional study was conducted among Police Officers who showed interest to participate in the HIVIS-03, a phase I/II HIV vaccine trial in Dar es Salaam. Prior to detailed training sessions about HIV vaccine trials, the potential participants narrated their individual motives to participate in the trial on a piece of paper. Descriptive analysis using content approach and frequency distributions were performed.Results: Of the 265 respondents, 242 (91.3%) provided their socio-demographic characteristics as well as reasons that would make them take part in the proposed trial. Majority, (39.7%), cited altruism as the main motive. Women were more likely to volunteer due to altruism compared to men (P < 0.01). Researchers' explanations about HIV/AIDS vaccine studies motivated 15.3%. More men (19.6%) than women (1.7%) were motivated to volunteer due to researchers' explanations (P < 0.001). Also, compared to other groups, those unmarried and educated up to secondary level of education were motivated to volunteer due to researchers' explanation (P < 0.05). Other reasons were: desire to become a role model (18.6%); to get knowledge for educating others (14.0%); to cooperate with researchers in developing an HIV vaccine (9.5%); to get protection against HIV infection (7.0%), and severity of the disease within families (6.2%). These results were supported by testimonies from both men and women.Conclusions: Participation in an HIV vaccine trial in a Tanzanian context is likely to be influenced by altruism and comprehensive education about the trial. Gender differences, marital status and education level need to be considered to enhance participation in future HIV vaccine trials. [ABSTRACT FROM AUTHOR]

Background: HIV/AIDS continues to destroy the lives of young people especially in low-income countries. The inclusion of youths in HIV vaccine trials is of utmost importance in obtaining an effective vaccine that is acceptable to them. Objective: To characterize the willingness of young adults in Tanzania to participate in an HIV vaccine trial and the factors that influence this willingness. Design: Four hundred and fifty young adults who visited a youth-friendly Infectious Diseases Clinic (IDC) from February 2012 to September 2012 completed a self-administered questionnaire concerning sociodemographic information, their knowledge about and perception of HIV vaccine studies, and the availability of social support. Result: Of our participants, 50.6% expressed willingness to participate in HIV vaccine trials, and this willingness was positively correlated with having some knowledge about HIV vaccine studies (AOR, 2.2; 95% CI: 1.4-3.4), a positive perception toward such studies (AOR, 2.3; 95% CI: 1.5-3.6), having a relationship with someone who could help them make a decision (AOR, 2.5; 95% CI: 1.3-4.9), and age at the time of sexual debut (AOR, 2.6; 95% CI 1.0-6.7) for 15- to 19-year-olds and (AOR, 2.7; 95% CI 1.0-7.1) for older participants. Conclusion: The participants exhibited a moderate willingness to participate in HIV vaccine trials, which was associated with a positive perception of and some knowledge about such trials, having a relationship with someone who might influence their decision as well as age at time of sexual debut. More efforts should be made to inform the youths about specific HIV vaccine trials and related matters, as well as to engage significant others in the decision-making process. [ABSTRACT FROM AUTHOR]

For time-to-event data with finitely many competing risks, the proportional hazards model has been a popular tool for relating the cause-specific outcomes to covariates (Prentice and others, 1978. The analysis of failure time in the presence of competing risks. Biometrics 34, 541–554). Inspired by previous research in HIV vaccine efficacy trials, the cause of failure is replaced by a continuous mark observed only in subjects who fail. This article studies an extension of this approach to allow a multivariate continuum of competing risks, to better account for the fact that the candidate HIV vaccines tested in efficacy trials have contained multiple HIV sequences, with a purpose to elicit multiple types of immune response that recognize and block different types of HIV viruses. We develop inference for the proportional hazards model in which the regression parameters depend parametrically on the marks, to avoid the curse of dimensionality, and the baseline hazard depends nonparametrically on both time and marks. Goodness-of-fit tests are constructed based on generalized weighted martingale residuals. The finite-sample performance of the proposed methods is examined through extensive simulations. The methods are applied to a vaccine efficacy trial to examine whether and how certain antigens represented inside the vaccine are relevant for protection or anti-protection against the exposing HIVs. [ABSTRACT FROM PUBLISHER]

A psychometric scale assessing inhibitors and facilitators of willingness to participate (WTP) in an HIV vaccine trial has not yet been developed. This study aimed to construct and derive the exploratory factor structure of such a scale. The 35-item Inhibitors and Facilitators of Willingness to Participate Scale (WPS) was developed and administered to a convenience sample of 264 Black females between the ages of 16 and 49 years living in an urban-informal settlement near Cape Town. The subscales of the WPS demonstrated good internal consistency with Cronbach's alpha coefficients ranging between 0.69 and 0.82. A principal components exploratory factor analysis revealed the presence of five latent factors. The factors, which accounted for 45.93% of the variance in WTP, were (1) personal costs, (2) safety and convenience, (3) stigmatisation, (4) personal gains and (5) social approval and trust. Against the backdrop of the study limitations, these results provide initial support for the reliability and construct validity of the WPS among the most eligible trial participants in the Western Cape of South Africa. [ABSTRACT FROM AUTHOR]

In the past decade, several principal stratification–based statistical methods have been developed for testing and estimation of a treatment effect on an outcome measured after a postrandomization event. Two examples are the evaluation of the effect of a cancer treatment on quality of life in subjects who remain alive and the evaluation of the effect of an HIV vaccine on viral load in subjects who acquire HIV infection. However, in general the developed methods have not addressed the issue of missing outcome data, and hence their validity relies on a missing completely at random (MCAR) assumption. Because in many applications the MCAR assumption is untenable, while a missing at random (MAR) assumption is defensible, we extend the semiparametric likelihood sensitivity analysis approach of Gilbert and others (2003) and Jemiai and Rotnitzky (2005) to allow the outcome to be MAR. We combine these methods with the robust likelihood–based method of Little and An (2004) for handling MAR data to provide semiparametric estimation of the average causal effect of treatment on the outcome. The new method, which does not require a monotonicity assumption, is evaluated in a simulation study and is applied to data from the first HIV vaccine efficacy trial. [ABSTRACT FROM PUBLISHER]

Aims To determine if incarceration was associated with human immunodeficiency virus (HIV) infection and identify risk factors for incarceration among injection drug users (IDUs) participating in an HIV vaccine trial in Bangkok. Design The AIDSVAX B/E HIV vaccine trial was a randomized, double-blind, placebo-controlled study. A proportional hazards model was used to evaluate demographic characteristics, risk behavior and incarceration as predictors of HIV infection and generalized estimation equation logistic regression analysis to investigate demographic characteristics and risk behaviors for predictors of incarceration. Setting The trial was conducted in Bangkok Metropolitan Administration drug-treatment clinics, 1999–2003. Participants A total of 2546 HIV-uninfected IDUs enrolled in the trial. Measurements HIV testing was performed and an interviewer-administered questionnaire was used to assess risk behavior and incarceration at baseline and every 6 months for a total of 36 months. Findings HIV incidence was 3.4 per 100 person-years [95% confidence interval (CI), 3.0–3.9] and did not differ among vaccine and placebo recipients. In multivariable analysis, being in jail ( P < 0.04), injecting ( P < 0.0001), injecting daily ( P < 0.0001) and sharing needles ( P = 0.02) were associated with HIV infection and methadone maintenance was protective ( P = 0.0006). Predictors of incarceration in multivariable analysis included: male sex ( P = 0.04), younger age ( P < 0.0001), less education ( P = 0.001) and being in jail ( P < 0.0001) or prison ( P < 0.0001) before enrollment. Conclusions Among IDUs in the AIDSVAX B/E trial, incarceration in jail was associated with incident HIV infection. IDUs in Thailand remain at high risk of HIV infection and additional prevention tools are needed urgently. HIV prevention services, including methadone, should be made available to IDUs. [ABSTRACT FROM AUTHOR]

Objectives To assess willingness to participate in HIV vaccine trials and possible barriers to participation. Methods Questionnaire survey of participants completing a 2-year community-based HIV Vaccine Preparedness Study, followed by cross sectional analysis of data. Results 95% of participants were willing to participate in a trial with similar attributes to the Vaccine Preparedness Study. Certain hypothetical trial attributes significantly reduced willingness to participate: The requirement to delay pregnancy (for females) had the largest effect, reducing willingness to participate from 97% to 23% ( P < 0.0001). Larger blood draws had the second largest effect: 95–55% ( P < 0.0001). The possibility of receiving either candidate vaccine or placebo had the third largest effect: 95–73% ( P < 0.0001). Monthly study visits had the fourth largest effect: 95–92% ( P < 0.0001). Trial duration longer than 2 years had the least effect: 95–93% ( P = 0.0025). Combined attributes reduced willingness to participate from 95% to 43% (McNemar’s χ2 = 521.00; P < 0.0001) overall and 97–11% (McNemar’s χ2 = 531.00; P < 0.0001) for female participants. Physical harm concerns (adjusted OR = 34.9; 95% CI, 10.4–118) and a low risk behaviour index (adjusted OR = 0.09; 95% CI, 0.01–0.73) were associated with unwillingness to participate. Conclusions We found a high level of willingness to participate in HIV vaccine trials in this population. However, certain HIV vaccine trial requirements were associated with reduced willingness to participate. Community as well as individual concerns will have to be carefully addressed in planned HIV vaccine trials. [ABSTRACT FROM AUTHOR]

Grouped failure time data arise often in HIV studies. In a recent preventive HIV vaccine efficacy trial, immune responses generated by the vaccine were measured from a case–cohort sample of vaccine recipients, who were subsequently evaluated for the study endpoint of HIV infection at prespecified follow-up visits. Gilbert et al. (2005, Journal of Infectious Diseases 191, 666–677) and Forthal et al. (2007, Journal of Immunology 178, 6596–6603) analyzed the association between the immune responses and HIV incidence with a Cox proportional hazards model, treating the HIV infection diagnosis time as a right-censored random variable. The data, however, are of the form of grouped failure time data with case–cohort covariate sampling, and we propose an inverse selection probability-weighted likelihood method for fitting the Cox model to these data. The method allows covariates to be time dependent, and uses multiple imputation to accommodate covariate data that are missing at random. We establish asymptotic properties of the proposed estimators, and present simulation results showing their good finite sample performance. We apply the method to the HIV vaccine trial data, showing that higher antibody levels are associated with a lower hazard of HIV infection. [ABSTRACT FROM AUTHOR]

The article discusses a study which examines the negative social impacts among volunteers in the phase three trial of an HIV vaccine in North America. A modest portion of volunteers reported problems in interpersonal relationships. Serious social problems involving insurance and employment were rare.

The article explores perceived barriers and motivators that may limit HIV vaccine trial participation among low-socioeconomic Latino and African communities at elevated risk for HIV. Perceived barriers and motivators suggest for the increasing cultural relevance of HIV vaccine preparation to facilitate participation. Recruitment and implementation strategies must focus on family perspective, cultural gender norms, mistrust, low perceived HIV risk and misconceptions on gaining protection against HIV infection.

Identifies the determinants of enrollment in a preventive HIV vaccine trial. Demographic and risk characteristics of enrollees; Potential social harms; Vaccine-induced seropositivity; Mistrust of government safety concerns.

This report evaluates long-term safety data from 3189 human immunodeficiency virus type 1 (HIV-1) uninfected, healthy volunteers who were enrolled into 51 National Institute of Allergy and Infectious Diseases (NIAID)-sponsored Phase I and II multicentred, randomized, double-blind trials of recombinant HIV-1 subunit vaccines (23 studies), synthetic peptide vaccines (7 studies), live vaccinia-vector recombinant envelope vaccines (7 studies), canarypox vector recombinant vaccines (13 studies), a DNA vaccine (1 study), and a Salmonella-vector vaccine (1 study). During the 12,340 person-years of follow-up, participants were monitored for adverse events including immune dysfunction/autoimmunity, anaphylaxis, cancer, death, and vaccine allergy. The analysis provides evidence that a preparation of a C4-V3 polypeptide vaccine emulsified in incomplete Freund’s caused serious toxicity, but otherwise no safety problems considered serious were identified for any of the vaccines and adjuvants studied. These data serve to solidify the growing safety base of current vaccine technologies utilized in candidate vaccines for HIV-1 infection. [Copyright &y& Elsevier]

An objective of randomized placebo-controlled preventive HIV vaccine efficacy trials is to assess the relationship between the vaccine effect to prevent infection and the genetic distance of the exposing HIV to the HIV strain represented in the vaccine construct. Motivated by this objective, recently a mark-specific proportional hazards model with a continuum of competing risks has been studied, where the genetic distance of the transmitting strain is the continuous `mark' defined and observable only in failures. A high percentage of genetic marks of interest may be missing for a variety of reasons, predominantly due to rapid evolution of HIV sequences after transmission before a blood sample is drawn from which HIV sequences are measured. This research investigates the stratified mark-specific proportional hazards model with missing marks where the baseline functions may vary with strata. We develop two consistent estimation approaches, the first based on the inverse probability weighted complete-case (IPW) technique, and the second based on augmenting the IPW estimator by incorporating auxiliary information predictive of the mark. We investigate the asymptotic properties and finite-sample performance of the two estimators, and show that the augmented IPW estimator, which satisfies a double robustness property, is more efficient.

South Africa has more people living with HIV than any other nation. The HIV epidemic in South Africa is being driven by new infections among adolescents. Inclusion of adolescents in HIV vaccine trials is essential for successful vaccine development, however, recruitment and retention of at-risk South African adolescents into these trials poses a number of legal, ethical and operational challenges. This article discusses the South African ethico-legal context in which future adolescent HIV vaccine trials would be conducted followed by a review of available data regarding strategies for recruitment into these trials and retention of trial participants.