Scientific Publications

An optimally effective AIDS vaccine would likely require the induction of both neutralizing antibody and cell-mediated immune responses, which has proven difficult to obtain in previous clinical trials. Here we report on the induction of Human Immunodeficiency Virus Type-1 (HIV-1)-specific immune responses in healthy adult volunteers that received the multi-gene, polyvalent, DNA prime-protein boost HIV-1 vaccine formulation, DP6-001, in a Phase I clinical trial conducted in healthy adult volunteers of both genders. Robust cross-subtype HIV-1-specific T cell responses were detected in IFNgamma ELISPOT assays. Furthermore, we detected high titer serum antibody responses that recognized a wide range of primary HIV-1 Env antigens and also neutralized pseudotyped viruses that express the primary Env antigens from multiple HIV-1 subtypes. These findings demonstrate that the DNA prime-protein boost approach is an effective immunization method to elicit both humoral and cell-mediated immune responses in humans, and that a polyvalent Env formulation could generate broad immune responses against HIV-1 viruses with diverse genetic backgrounds.

In Zambia the HIV/AIDS epidemic has resulted in many single female-headed households. Strong patriarchal laws and customs prevent widows and children from maintaining economic assets. This study examines the impact of a video-based motivational intervention promoting future planning in 1,504 HIV-infected couples in Lusaka, Zambia. Following a group video session, couples randomized to the motivational arm could choose to write a will, identify a guardian for their children and make financial plans. Desirable behaviours modelled in the motivational video were measured at quarterly intervals for a year and compared in intervention and control arms. Demographic measures including age, income and educational status were not associated with planning behaviours. Participation in the intervention was associated with will writing (23% versus 5%) and naming a guardian (32% versus 17%) but not with other planning behaviours. The study demonstrates the ability of motivational messages integrated into HIV VCT to encourage future planning behaviour and points to the need to expand existing HIV and VCT services to meet other non-health needs of those living with HIV.

The ability to elicit broadly neutralizing antibody responses against HIV-1 is a crucial goal for a prophylactic HIV-1 vaccine. Here, we discuss the difficulties of achieving broad HIV-1 neutralization in the context of both the effective annual human influenza virus vaccine and the need to develop a pandemic influenza vaccine. Immunogen-design strategies are underway to target functionally conserved regions of the HIV-1 envelope glycoproteins, and similar strategies might be applicable to pandemic influenza virus vaccine development. Efforts to develop broadly neutralizing vaccines against either HIV-1 or influenza virus might establish a paradigm for future vaccines against highly variable pathogens.

Most HIV-1 transmission in Africa occurs among HIV-1-discordant couples (one partner HIV-1 infected and one uninfected) who are unaware of their discordant HIV-1 serostatus. Given the high HIV-1 incidence among HIV-1 discordant couples and to assess efficacy of interventions for reducing HIV-1 transmission, HIV-1 discordant couples represent a critical target population for HIV-1 prevention interventions and prevention trials. Substantial regional differences exist in HIV-1 prevalence in Africa, but regional differences in HIV-1 discordance among African couples, has not previously been reported.

Recombinant adeno-associated viral vectors (rAAV) are being developed as gene therapy delivery vehicles and as genetic vaccines, and some of the most scaleable manufacturing methods for rAAV use live adenovirus to induce production. One aspect of establishing safety of rAAV products is therefore demonstrating adequate and reliable clearance of this helper virus by the vector purification process. The ICH Q5A regulatory guidance on viral safety provides recommendations for process design and characterization of viral clearance for recombinant proteins, and these principles were adapted to a rAAV serotype 1 purification process for clinical vectors. Specific objectives were to achieve overall adenovirus clearance factors significantly greater than input levels by using orthogonal separation and inactivation methods, and to segregate adenovirus from downstream operations by positioning a robust clearance step early in the process. Analytical tools for process development and characterization addressed problematic in-process samples, and a viral clearance validation study was performed using adenovirus and two non-specific model viruses. Overall clearance factors determined were >23 LRV for adenovirus, 11 LRV for BVDV, and >23 LRV for AMuLV.

Human immunodeficiency virus type 1 (HIV-1) infection encounters an early block in the cells of New World monkeys because the CD4 receptor does not efficiently support HIV-1 entry. We adapted HIV-1(NL4-3) and HIV-1(KB9), two HIV-1 variants with different envelope glycoproteins, to replicate efficiently in cells expressing the CD4 and CXCR4 proteins of the common marmoset, a New World monkey. The HIV-1(NL4-3) adaptation involves three gp120 changes that result in a specific increase in affinity for the marmoset CD4 glycoprotein. The already high affinity of the HIV-1(KB9) envelope glycoproteins for marmoset CD4 did not significantly change as a result of the adaptation. Instead, changes in the gp120 variable loops and gp41 ectodomain resulted in improved replication in cells expressing the marmoset receptors. HIV-1(KB9) became relatively sensitive to neutralization by soluble CD4 and antibodies as a result of the adaptation. These results demonstrate the distinct mechanistic pathways by which the HIV-1 envelope glycoproteins can adapt to less-than-optimal CD4 molecules and provide HIV-1 variants that can overcome some of the early blocks in New World monkey cells.

Biased enrollment and attrition compromise the power of clinical trials and limit generalizability of findings. We identify predictors of enrollment and retention for HIV-discordant couples enrolled in prospective studies in Zambia.

An AIDS vaccine could play a very significant role in reversing the HIV pandemic, saving millions of lives. For a vaccine to have such an impact, it must be widely available and adopted and taken up rapidly in the countries most affected. A demand-forecasting model provides a valuable tool that can guide R&D spending decisions and identify policy actions to help achieve these goals.

: We describe promotional strategies for couples' voluntary HIV counseling and testing (CVCT) and demographic risk factors for couples in Lusaka, Zambia, where an estimated two thirds of new infections occur in cohabiting couples.

Trimers of the HIV-1 envelope glycoprotein (Env) effectuate viral entry into susceptible cells. Therefore Env trimers are the targets for neutralizing antibodies. This study models the number of trimers required for virion infectivity. It also delineates the minimum number of antibody molecules that would neutralize a virion. First, Env function was assumed to be incremental (all envelope glycoprotein units contribute equally) or liminal (characterized by thresholds). Then, such models were combined and shown to fit published data on phenotypically mixed pseudotype viruses. Virions with 9 trimers would require around a median of 5 of them for strong infectivity; the proportion varies among strains and mutants. In addition, the models account for both liminal and incremental protomeric effects at the trimer level: different inert Env mutants may affect trimer function in different degrees. Because of compensatory effects at the virion and trimer levels, however, current data cannot differentiate between all plausible models. But the biophysically and mathematically rationalized blurring of thresholds yields candidate models that fit different data excellently.

Most new HIV infections in Africa are acquired from cohabiting heterosexual partners. Couples' Voluntary Counselling and Testing (CVCT) is an effective prevention strategy for this group. We present our experience with a community-based program for the promotion of CVCT in Kigali, Rwanda and Lusaka, Zambia.

The role of homosexuality and anal sex practices in the African HIV -1 epidemic is not well described. We aimed to assess the risk factors for prevalent HIV-1 infection among men who have sex with men (MSM) to guide HIV-1 prevention efforts.