A next-generation strategy for HIV-1 vaccination: computational design of a multi-epitope subunit vaccine targeting global circulating variants

HIV-1/AIDS vaccine development: are we in the darkness before the dawn?

In June this year, it was 30 years since the identification of the first AIDS patient (see the review in this issue 1). Despite rapid responses by scientists and doctors to understand this disease in both clinical and experimental systems 2, 3, human immunodeficiency virus type 1 (HIV-1), the causative agent of AIDS (Fig. 1), continues to feature among world's three major killers destroying millions of lives, families and communities. More than 30 drugs have been developed just for HIV-1 and there have been three successful trials showing their impressive preventive potential. However, because of the drug unavailability, particularly in resource poor settings, side effects and potential development of resistance, the best hope for a profound fall in the incidence of HIV-1 infection remains the development of an effective prophylactic HIV-1 vaccine. Here, we discuss T-cell vaccine designs mainly, briefly mentioning antibody vaccines. HIV © PhotoDisc, Inc. Even if a vaccine that actively stimulates broadly neutralizing antibodies (bNAbs) can be made 4, it will be hard to stop some HIV-1 infection occurring (e.g. through cell–cell transmission) and T-cell-mediated immune responses to control infection will be required. T cells function by killing HIV-1-infected cells and producing soluble factors that can directly and indirectly control HIV-1 spread. While T cells cannot prevent the transmitted virus from infecting host cells, potent vaccine-induced HIV-1-specific T-cell responses could increase the dose of incoming virus necessary to establish infection (i.e. decrease acquisition) 5, limit the extent of viral replication during primary viremia (i.e. reduce tissue damage), lower the virus load at set point (i.e. reduce further virus transmission) and slow the rate of CD4+ T-cell decline (i.e. delay the development of AIDS). The simian immunodeficiency virus/macaque challenge model strongly supports this view, showing that potent T-cell responses alone can lower virus load and delay the development of AIDS 6-8. Thus, ideally, a successful HIV-1 vaccine will induce both T-cell and antibody responses; however, an effective T- or B-cell vaccine alone is nonetheless likely to impact the epidemic 9. Scientists developing HIV-1 vaccines face a long list of challenges. Although these differ for the induction of effective T-cell responses in comparison with induction of the desired bNAb specificity by active immunization, one major hurdle is common, namely the extreme HIV-1 variability. The main HIV-1 group has diversified into 15 major clades, subclades and interclade recombinant circulating forms, whereby individual HIV-1 variants, even within clades, may differ by up to 20% of their amino acid sequence, which is more than enough to severely impair broad T-cell and antibody recognition. CD8+ T-cell recognition of epitopes is usually highly sensitive to even a single amino acid deviation from the well-recognized sequence and this decreases T-cell recognition efficacy. Thus, a successful vaccine has to effectively recognize diverse infecting HIV-1 strains circulating in the population and then must deal with ongoing virus escape in infected individuals. Although in acute HIV-1 infection, the founding virus is usually single, the first T-cell responses tend to focus on immunodominant, but highly variable epitopes, in which mutations are selected very rapidly, escaping the early T-cell responses. NAbs develop much later in infection after the damage to the immune system is already done. HIV-1 has an enormous capacity to change. Some HIV-1 proteins such as the envelope are more variable than e.g. the internal structural proteins. On a sub-molecular level, some protein regions have to remain more-or-less constant to maintain their structural or biological functions and, therefore, even HIV-1 has its Achilles heel and this can be exploited. Focusing the vaccine-elicited responses on the functionally conserved regions of the HIV-1 proteome has a number of advantages. First, conserved regions are common to the diverse virus strains and clades to which vaccines are exposed. Second, targeting the conserved regions reduces the chance of virus escape in infected individuals. If escape mutations do occur, and some have been documented in conserved regions 10, they may often decrease virus fitness as shown e.g. for a B57-restricted epitope 11, or may require compensating mutation(s) as in the case of a B27-restricted Gag epitope 12. Therefore, escape mutations in the conserved regions may be good for patient's clinical prognosis or may be very delayed. Third, T-cell immunogens based on the functionally conserved parts of HIV-1 proteins redirect the naturally induced hierarchy of epitope responses, which is non-protective, towards invariable regions, which are arguably more likely to be protective. Finally, conserved immunogens can be designed as a simple single insert, representative of the major global clades A, B, C, and D equally. Therefore, vaccines based on the conserved regions of the HIV-1 proteome can be tested and potentially deployed in Europe, America, Asia, and Africa; they are universal. The first conserved region vaccine entered clinical evaluation in HIV-1 seronegative volunteers in Oxford, UK, and the results are expected in summer 2012. Most initial vaccine strategies focused on the breadth, i.e. the number of different epitopes of the HIV-1 proteome recognized by vaccine-induced responses, rather than the depth defined as the number of variants of the same epitopes. Therefore, early vaccines often incorporated into their formulations almost a whole set of virus proteins. The rationale behind this was that, if a multiplicity of epitopes were recognized at the same time, this would prevent HIV-1 from changing all of these epitopes at the same time and escaping immune surveillance. An example of such a single clade vaccine is MRKAd5 developed by the Merck Research Laboratories, which showed no efficacy in the first T-cell vaccine STEP trial in 2007 13, 14. When the power of the virus variability became more appreciated and respected, many vaccine designs mixed variants of the same protein derived from several different HIV-1 clades into a single formulation. One such vaccine is currently in a recently expanded phase IIb proof-of-concept trial designated the HIV Vaccine Trials Network (HVTN) protocol 505 15. More advanced T-cell-based vaccine strategies have taken full advantage of the Los Alamos National Laboratory (LANL) HIV Sequence Database, which has the most complete data set of known HIV-1 isolates. The first in silico approach that emerged computed centralized sequences 16. This approach uses either consensus (average) or centre-of-phylogenetic tree whole protein sequences or extrapolates individual amino acid positions in the whole proteins to common clade or group ancestors. This captures the intraclade variation, but is likely to be too stretched to comprehensively cover the whole main group of HIV-1 variants. The best coverage of the ‘non-conserved’ strategies computes mosaic proteins, which are artificial sequences assembled in silico using an iterative algorithm 17. Known 9-amino acid stretches were chosen because this is the most typical length of an epitope recognized by CD8+ T killer cells and by computing mosaic proteins the coverage of all common variants of these sequences is maximized. For example, a tetravalent mosaic protein of Gag optimized on the main group sequences covers about 74% of the main group Gag-derived 9-mers as a perfect match. Both computed designs described are supported by a strong rationale; nevertheless, they do not refocus the immune responses away from the dominant, hypervariable regions towards the subdominant but invariant regions of HIV-1 18, 19. This means that the induced T-cell responses, although increased in depth, are just as likely to focus on variable regions and this opens the possibility of selecting novel escape variants not yet included in the LANL database. Recent deep sequencing of natural T-cell escape mutations showed that a very large number of alternative amino acids were generated by mutation during infection and ‘tested’ in these variable epitope positions 20. In essence, perhaps the best solution to a T-cell vaccine immunogen is one that consists of conserved regions made of mosaic sequences. The first mosaic vaccine is scheduled to enter clinical evaluation in year 2012. Even the most conserved regions of the HIV-1 proteome are not immunologically inert. By inspecting the LANL HIV-1 database, it can be seen that conserved regions contain their fair share of CD8+ T-cell epitopes, which are proportional to their amino acid length. These epitopes were identified mostly in chronically infected individuals, who had mounted T-cell responses against them. Moreover, preliminary immunogenicity results from the first trials of the conserved vaccines show encouraging immunogenicity. Nevertheless, as with any approach, vaccines based on the conserved regions have their theoretical caveats. First, conserved immunogens are chimeric proteins assembled from protein sub-regions and, as such, have sequence junctions where the sub-regions meet. These junctions may create novel irrelevant epitopes (not present in HIV-1), which could, for certain HLAs, be immunodominant and suppress induction of protective responses. However, based on the likelihood of creating such immunodominant interfering junctional epitopes, these will almost certainly be the exception rather than the rule. Second, CD4+ T cells, the main natural target cells for HIV-1 replication, do not have co-stimulatory molecules on their surface and, therefore, are not potent primers of T-cell responses. Thus, in natural HIV-1 infection, many or most T-cell responses are primed either by direct infection of ‘professional’ antigen-presenting cells or through cross-priming, for instance via the uptake of HIV-1-infected apoptotic cell debris by ‘professional’ antigen-presenting cells. While it is known that most immunodominant epitopes are expressed on HIV-1-infected cells, this has not been explored in great detail for subdominant epitopes such as those derived from the HIV-1 conserved regions. Thus, it is not guaranteed that HIV-1-infected cells express conserved epitopes on their surface in sufficient amounts for effective and timely killing by cytotoxic T cells, i.e. before the infected cells produce HIV-1 progeny, which is key for the success of conserved T-cell vaccines (Fig. 2). Both of these caveats are being investigated in the on-going clinical trials of the conserved vaccines by e.g. in vitro virus suppression assays utilising vaccine-induced T-cell effectors 21. Are subdominant epitopes from conserved regions of the HIV-1 proteome presented efficiently on the surface of HIV-1-infected cells? The strategy for controlling HIV-1 by the use of conserved T-cell epitopes has been proposed on several occasions 22-24. However, an actual T-cell vaccine employing conserved regions (rather than epitopes) of HIV-1, thus preserving the natural epitope adjacent sequences and also the possibility of inducing responses to as yet unidentified epitopes, was first reported by Letourneau et al., who employed the 14 most conserved regions of the proteome as 27- to 128-amino acid-long consensus sequences alternating the four major main global clades A, B, C, and D 25. At about the same time, such an approach was theoretically proposed by Rolland et al., who suggested the use of 45 conserved elements (CEs) at least 8 amino acids long that fulfilled stringent conservation criteria 26. Since then, there has been a flurry of papers addressing and discussing various aspects of universal vaccines based on conserved regions of HIV-1, including for example: conserved region vaccines being tested in rhesus macaques and found to be highly immunogenic 27; proposal of a universal peptide vaccine based on conserved regions of HIV-1 28; recognition of conserved and variable CD8+ T-cell epitopes with similar probabilities during both primary and chronic infections, whereby the conserved epitopes generally elicited subdominant responses 29; detection of an association between responses to conserved T-cell epitopes and lower virus loads 30; skewing of vaccine-elicited T-cell responses away from more conserved epitopes to the more variable and therefore possibly less protective epitopes, which did not match the infecting viruses, as detected in the failed STEP trial 31; a novel analysis of controllers who durably control HIV-1 without medications that revealed preferential targeting of a conserved sector in Gag and concluded that targeting regions with higher order evolutionary constraints provides a novel approach to immunogen design 32; Thus, support for T-cell vaccine strategies employing conserved regions of the HIV-1 proteome is growing. Many pathogens use antigenic variability of the most immunogenic regions on their surface to avoid host antibody-based defences. Thus, antibody-inducing vaccines have a much longer tradition in focusing on conserved regions 33. Indeed, even the most variable protein, Env, of HIV-1 has invariable regions, of which the most conserved is the CD4 receptor-binding site 34. Recently, there has been tremendous progress in understanding the mechanisms underlying potent and broad HIV-1 neutralization 35, 36. The roadblock of efficiently inducing such specificity by active vaccination remains, but conserved regions are once again at the centre of attention. This article has mainly concentrated on the theoretical arguments for and against the various HIV-1 immunogen platforms currently under evaluation; it provides only limited experimental evidence because this is only just starting to emerge. Vaccine success will depend significantly, but not exclusively on immunogens; it will also be critical to factor in how these immunogens are presented to the immune system, i.e. the choice of vaccine vectors and vector combinations, adjuvantation and routes of delivery 37. Which vaccine strategy is the best can be only decided by protection of humans against HIV-1 infection and/or AIDS and this, in turn, can only be answered in efficacy trials. These are expensive, but highly informative. Moreover, the very last one, RV144 38, even provided a moderate reason for optimism. Last but not least, vaccines will not be discovered without continued financial and political support, new scientific discoveries and human will and persistence. World AIDS day (http://www.worldaidsday.org/) on 1 December offers the perfect opportunity to ensure that such issues are highlighted globally.

Many attempts to design prophylactic human immunodeficiency virus type 1 (HIV-1) vaccines have focused on the induction of neutralizing antibodies (Abs) that block infection by free virions. Despite the focus on viral particles, virus-infected cells, which can be found within mucosal secretions, are more infectious than free virus both in vitro and in vivo. Furthermore, assessment of human transmission couples suggests infected seminal lymphocytes might be responsible for a proportion of HIV-1 transmissions. Although vaccines that induce neutralizing Abs are sought, only some broadly neutralizing Abs efficiently block cell-to-cell transmission of HIV-1. As HIV-1 vaccines need to elicit immune responses capable of controlling both free and cell-associated virus, we evaluated the potential of natural killer (NK) cells to respond in an Ab-dependent manner to allogeneic T cells bearing HIV-1 antigens. This study presents data measuring Ab-dependent anti-HIV-1 NK cell responses to primary and transformed allogeneic T-cell targets. We found that NK cells are robustly activated in an anti-HIV-1 Ab-dependent manner against allogeneic targets and that tested target cells are subject to Ab-dependent cytolysis. Furthermore, the educated KIR3DL1(+) NK cell subset from HLA-Bw4(+) individuals exhibits an activation advantage over the KIR3DL1(-) subset that contains both NK cells educated through other receptor/ligand combinations and uneducated NK cells. These results are intriguing and important for understanding the regulation of Ab-dependent NK cell responses and are potentially valuable for designing Ab-dependent therapies and/or vaccines. NK cell-mediated anti-HIV-1 antibody-dependent functions have been associated with protection from infection and disease progression; however, their role in protecting from infection with allogeneic cells infected with HIV-1 is unknown. We found that HIV-1-specific ADCC antibodies bound to allogeneic cells infected with HIV-1 or coated with HIV-1 gp120 were capable of activating NK cells and/or trigging cytolysis of the allogeneic target cells. This suggests ADCC may be able to assist in preventing infection with cell-associated HIV-1. In order to fully utilize NK cell-mediated Ab-dependent effector functions, it might also be important that educated NK cells, which hold the highest activation potential, can become activated against targets bearing HIV-1 antigens and expressing the ligands for self-inhibitory receptors. Here, we show that with Ab-dependent stimulation, NK cells expressing inhibitory receptors can mediate robust activation against targets expressing the ligands for those receptors.

Mother-to-child HIV-1 transmission accounts for more than 700 000 new paediatric HIV-1 infections in developing countries each year [1]. This comprises less than one-third of the infants born to human immunodeficiency virus type 1 (HIV-1) infected mothers, the majority of whom remain uninfected despite recurrent risk for contact with the virus in utero, during delivery and through breastfeeding. A comprehensive approach to studying infant immunity against HIV-1 may provide insight into the determinants of HIV-1 acquisition, promote an understanding of resistance to infection in the setting of repeated exposure to the virus and contribute to the development of therapeutic interventions or vaccines against HIV-1 transmission. Several unique features of mother-to-child HIV-1 transmission provide advantages in determining correlates of HIV-1 acquisition and viral immunity when compared to sexual HIV-1 transmission models. Both HIV-1 infected mothers and their exposed infants can be evaluated for viral and immunological factors associated with transmission. HIV-1 exposure can be characterized by quantifying maternal HIV-1 viral load in plasma, breast milk and genital tract secretions, and infant immune responses can be defined simultaneously or near the time of exposure. Timing of transmission can be estimated using HIV-1 polymerase chain reaction (PCR) at birth and at regular intervals after exposure during delivery and breastfeeding. Vertical HIV-1 transmission risk is also higher than sexual transmission risk. Per sexual act, it is estimated that the risk of heterosexual transmission is approximately 0·1% in an antiretroviral naive population [2]. The risk of HIV-1 acquisition during delivery ranges from 10 to 20%, more than 100-fold higher than heterosexual transmission rates. Disparities between heterosexual and vertical HIV-1 transmission rates persist in the setting of antiretroviral therapy. This enables mother–child transmission studies to provide robust epidemiological data regarding specific immune mechanisms and combinations of immune responses that may constitute protective immunity against HIV-1. This review examines the spectrum of innate, humoral and cellular immune responses and genetic factors that have been studied in infants who are HIV-1 infected or HIV-1 exposed and uninfected (Fig. 1). Fig. 1 Immune responses and genetic factors associated with mother-to-child HIV-1 transmission and paediatric HIV-1 disease progression. *May be maternally acquired in utero or via breast milk. †Alloimmunity is dependent on degree of maternal–infant ... INNATE IMMUNITY Innate immune responses are generated rapidly and are important in preventing and containing infections with a variety of viral pathogens. Broad innate immunity may also be capable of protecting against immune-escape viruses generated by more narrow adaptive immune responses. In HIV-1 transmission and disease progression, relevant innate mechanisms of immunity include the activity of natural killer (NK) cells and antiviral proteins such as the CC chemokines, CD8+ antiviral factor (CAF) and secretory leucocyte protease inhibitor (SLPI). Natural killer (NK) cell activity Natural killer (NK) cells induce inflammation and lyse infected cells without prior sensitization and in a non-HLA restricted manner. NK cells from HIV-1 infected individuals release the CC chemokines MIP-1α, MIP-1β and RANTES, three factors that have been shown to inhibit HIV-1 independently in vitro by blocking the CCR5 HIV-1 coreceptor [3,4]. NK cells also act by lysing HIV-1 infected cells via antibody-dependent cellular cytotoxicity (ADCC). This is initiated by binding of NK cell Fc receptors (CD16) to target cells coated with HIV-specific antibodies of the subclass IgG1 [5–7]. HIV-specific ADCC antibodies are directed against the viral envelope glycoproteins gp120 and gp41 and are distinct from virus-neutralizing antibodies [8]. There is conflicting evidence regarding the role of NK cells in containing HIV-1 in chronically infected children and in preventing vertical HIV-1 transmission. Several studies have evaluated HIV-specific ADCC antibody titres in sera of infants born to HIV-1 infected mothers and found that these antibodies are transferred efficiently across the placenta from mother to fetus [9,10]. However, there was no significant correlation between antibody titres at birth and either HIV-1 disease progression during 2 years of follow-up or mother-to-child HIV-1 transmission [9,10]. Active production of HIV-specific ADCC antibodies was observed in the majority of HIV-infected infants only after 12 months of age [10] and effector cells from HIV-1 infected children appear unable to generate NK cell-mediated cytotoxicity [11]. Thus, an immature immune system may account for the absence of ADCC-mediated NK protection against HIV-1 infection in neonates and young infants, despite adequate levels of passively transferred ADCC antibodies. This may contribute to rapid HIV-1 progression in children infected with HIV-1 early in life [10,11].

The microbiome is an integral and dynamic component of the host and is emerging as a critical determinant of immune responses; however, its influence on vaccine immunogenicity is largely not well understood. Here, we examined the pivotal relationship between the mucosal microbiome and vaccine-induced immune responses by assessing longitudinal changes in vaginal and rectal microbiome profiles after intradermal immunization with a human immunodeficiency virus type 1 (HIV-1) DNA vaccine in adult rhesus macaques that received two prior DNA primes. We report that both vaginal and rectal microbiomes were dominated by Firmicutes but were composed of distinct genera, denoting microbiome specialization across mucosal tissues. Following immunization, the vaginal microbiome was resilient, except for a transient decrease in Streptococcus In contrast, the rectal microbiome was far more responsive to vaccination, exhibiting an increase in the ratio of Firmicutes to Bacteroidetes Within Bacteroidetes, multiple genera were significantly decreased, including Prevotella, Alloprevotella, Bacteroides, Acetobacteroides, Falsiporphyromonas, and Anaerocella. Decreased abundance of Prevotella correlated with induction of gut-homing α4β7+ effector CD4 T cells. Prevotella abundance also negatively correlated with rectal HIV-1 specific IgG levels. While rectal Lactobacillus was unaltered following DNA vaccination, baseline Lactobacillus abundance showed strong associations with higher rectal HIV-1 gp140 IgA induced following a protein boost. Similarly, the abundance of Clostridium in cluster IV was associated with higher rectal HIV-1 gp140 IgG responses. Collectively, these data reveal that the temporal stability of bacterial communities following DNA immunization is site dependent and highlight the importance of host-microbiome interactions in shaping HIV-1 vaccine responses. Our findings have significant implications for microbial manipulation as a strategy to enhance HIV vaccine-induced mucosal immunity.IMPORTANCE There is considerable effort directed toward evaluating HIV-1 vaccine platforms to select the most promising candidates for enhancing mucosal HIV-1 antibody. The most successful thus far, the RV144 trial provided partial protection due to waning HIV-1 antibody titers. In order to develop an effective HIV vaccine, it may therefore be important to understand how biological factors, such as the microbiome, modulate host immune responses. Furthermore, as intestinal microbiota antigens may generate antibodies cross-reactive to the HIV-1 envelope glycoprotein, understanding the relationship between gut microbiota composition and HIV-1 envelope antibody responses after vaccination is important. Here, we demonstrate for the first time in rhesus macaques that the rectal microbiome composition can influence HIV-1 vaccine immunogenicity, and we report temporal changes in the mucosal microbiome profile following HIV-1 vaccination. Our results could inform findings from the HIV Vaccine Trials Network (HVTN) vaccine studies and contribute to an understanding of how the microbiome influences HIV-1 antibody responses.

Toll-like receptors (TLRs) are a family of pattern recognition receptors and part of the first line of defense against invading microbes. In humans, we know of 10 different TLRs, which are expressed to varying degrees in immune cell subsets. Engaging TLRs through their specific ligands leads to activation of the innate immune system and secondarily priming of the adaptive immune system. Because of these unique properties, TLR agonists have been investigated as immunotherapy in cancer treatment for many years, but in recent years there has also been growing interest in the use of TLR agonists in the context of human immunodeficiency virus type 1 (HIV-1) cure research. The primary obstacle to curing HIV-1 is the presence of a latent viral reservoir in transcriptionally silent immune cells. Due to the very limited transcription of the integrated HIV-1 proviruses, latently infected cells cannot be targeted and cleared by immune effector mechanisms. TLR agonists are very interesting in this context because of their potential dual effects as latency reverting agents (LRAs) and immune modulatory compounds. Here, we review preclinical and clinical data on the impact of TLR stimulation on HIV-1 latency as well as antiviral and HIV-1-specific immunity. We also focus on the promising role of TLR agonists in combination strategies in HIV-1 cure research. Different combinations of TLR agonists and broadly neutralizing antibodies or TLRs agonists as adjuvants in HIV-1 vaccines have shown very encouraging results in non-human primate experiments and these concepts are now moving into clinical testing.

After decades of its epidemic, the human immunodeficiency virus type 1 (HIV-1) is still rampant worldwide. An effective vaccine is considered to be the ultimate strategy to control and prevent the spread of HIV-1. To date, hundreds of clinical trials for HIV-1 vaccines have been tested. However, there is no HIV-1 vaccine available yet, mostly because the immune correlates of protection against HIV-1 infection are not fully understood. Currently, a variety of recombinant viruses-vectored HIV-1 vaccine candidates are extensively studied as promising strategies to elicit the appropriate immune response to control HIV-1 infection. In this review, we summarize the current findings on the immunological parameters to predict the protective efficacy of HIV-1 vaccines, and highlight the latest advances on HIV-1 vaccines based on viral vectors.

While abundant sequence information is available from human immunodeficiency virus type 1 (HIV-1) subtypes A, B, C and CRF01_AE for HIV-1 vaccine design, sequences from West Africa are less represented. We sought to augment our understanding of HIV-1 variants circulating in 6 Nigerian cities as a step to subsequent HIV-1 vaccine development.The G/CRF02_AG multi-region hybridization assay (MHA) was developed to differentiate subtype G, CRF02_AG and their recombinants from other subtypes based on 7 HIV-1 segments. Plasma from 224 HIV-1 infected volunteers enrolled in a cohort examining HIV-1 prevalence, risk factor, and subtype from Makurdi (30), Abuja (18), Enugu (11), Kaduna (12), Tafa (95), and Ojo/Lagos (58) was analyzed using MHA. HIV-1 genomes from 42 samples were sequenced to validate the MHA and fully explore the recombinant structure of G and CRF02_AG variants.The sensitivity and specificity of MHA varied between 73-100% and 90-100%, respectively. The subtype distribution as identified by MHA among 224 samples revealed 38% CRF02_AG, 28% G, and 26% G/CRF02_AG recombinants while 8% remained nontypeable strains. In envelope (env) gp120, 38.84% of the samples reacted to a G probe while 31.25% reacted to a CRF02 (subtype A) probe. Full genome characterization of 42 sequences revealed the complexity of Nigerian HIV-1 variants.CRF02_AG, subtype G, and their recombinants were the major circulating HIV-1 variants in 6 Nigerian cities. High proportions of samples reacted to a G probe in env gp120 confirms that subtype G infections are abundant and should be considered in strategies for global HIV-1 vaccine development.

Human leukocyte antigen (HLA) molecules regulate the cellular immune system and may be determinants of infant susceptibility to human immunodeficiency virus type 1 (HIV-1) infection. Molecular HLA typing for class I alleles was performed on infants followed in a Kenyan perinatal cohort. Early HIV-1 infection status was defined as infection occurring at birth or month 1, while late infection via breast milk was defined as first detection of HIV-1 after 1 month of age. Likelihood ratio tests based on a proportional hazards model adjusting for maternal CD4 T cell count and HIV-1 viral load at 32 weeks of gestation were used to test associations between infant allelic variation and incident HIV-1 infection. Among 433 infants, 76 (18%) were HIV-1 infected during 12 months of follow-up. HLA B*18 was associated with a significantly lower risk of early HIV-1 transmission [relative risk (RR) = 0.26; 95% confidence interval (CI) 0.04-0.82], and none of the 24 breastfeeding infants expressing HLA B*18 who were uninfected at month 1 acquired HIV-1 late via breast milk. We observed a trend toward increased early HIV-1 acquisition for infants presenting HLA A*29 (RR = 2.0; 95% CI 1.0-3.8) and increased late HIV-1 acquisition via breast milk for both Cw*07 and Cw*08 (RR = 4.0; 95% CI 1.0-17.8 and RR = 7.2; 95% CI 1.2-37.3, respectively). HLA B*18 may protect breast-feeding infants against both early and late HIV-1 acquisition, a finding that could have implications for the design and monitoring of HIV-1 vaccines targeting cellular immune responses against HIV-1.

BackgroundThe human immunodeficiency virus type 1(HIV-1) epidemic in Chongqing, China, is increasing rapidly with the dominant subtype of CRF07_BC over the past 3 years. Since human leukocyte antigen (HLA) polymorphisms have shown strong association with susceptibility/resistance to HIV-1 infection from individuals with different ethnic backgrounds, a recent investigation on frequencies of HLA class I and class II alleles in a Chinese cohort also indicated that similar correlation existed in HIV infected individuals from several provinces in China, however, such information is unavailable in Chongqing, southwest China.MethodsIn this population-based study, we performed polymerase chain reaction analysis with sequence-specific oligonucleotide probes (PCR-SSOP) for intermediate-low-resolution HLA typing in a cohort of 549 HIV-1 infected individuals, another 2475 healthy subjects from the Han nationality in Chongqing, China, were selected as population control. We compared frequencies of HLA-A, B, DRB1 alleles, haplotypes and genotypes between the two groups, and analyzed their association with HIV-1 susceptibility or resistance.ResultsThe genetic profile of HLA (A, B, DRB1) alleles of HIV-1 infected individuals from Chongqing Han of China was obtained. Several alleles of HLA-B such as B*46 (P = 0.001, OR = 1.38, 95%CI = 1.13-1.68), B*1501G(B62) (P = 0.013, OR = 1.42, 95%CI = 1.08-1.88), B*67 (P = 0.022, OR = 2.76, 95%CI = 1.16-6.57), B*37 (P = 0.014, OR = 1.93, 95%CI = 1.14-3.28) and B*52 (P = 0.038, OR = 1.64, 95%CI = 1.03-2.61) were observed to have association with susceptibility to HIV-1 infection in this population. In addition, the haplotype analysis revealed that A*11-B*46, A*24-B*54 and A*01-B*37 for 2-locus, and A*11-B*46-DRB1*09, A*02-B*46-DRB1*08, A*11-B*4001G-DRB1*15, A*02-B*4001G-DRB1*04, A*11-B*46-DRB1*08 and A*02-B*4001G-DRB1*12 for 3-locus had significantly overrepresented in HIV-1 infected individuals, whereas A*11-B*1502G, A*11-B*1502G-DRB1*12 and A*33-B*58-DRB1*13 were underrepresented. However, the low-resolution homozygosity of HLA-A, B, DRB1 loci and HLA-Bw4/Bw6 genotypes did not differ significantly between the two groups.ConclusionThese results may contribute to the database of HLA profiles in HIV-1 infected Chinese population, consequently, the association of certain HLA alleles with susceptibility or resistance to HIV-1 infection would provide with clues in choosing proper preventive strategies against HIV-1 infection and developing effective HIV-1 vaccines in Chinese population, especially for those in southwest China.

IntroductionHuman leukocyte antigen (HLA) molecules regulate the cellular immune system and may be determinants of infant susceptibility to human immunodeficiency virus type 1 (HIV-1) infection. Molecular HLA typing for class...

Vaccination of infants against human immunodeficiency virus type 1 (HIV-1) may prevent mother-to-child HIV-1 transmission. Successful trials and immunization efforts will depend on the willingness of individuals to participate in pediatric vaccine research and acceptance of infant HIV-1 vaccines. In a cross-sectional study, pregnant women presenting to a Nairobi antenatal clinic for routine care were interviewed regarding their attitudes toward participation in research studies and HIV-1 vaccine acceptability for their infants. Among 805 women, 782 (97%) reported they would vaccinate their infant against HIV-1 and 729 (91%) reported willingness to enroll their infant in a research study. However, only 644 (80%) would enroll their infants if HIV- 1 testing was required every 3 months and 513 (64%) would agree to HIV-1 vaccine trial participation. Reasons for not wanting to enroll in a pediatric HIV-1 vaccine trial included concerns about side effects (75%), partner objection (34%), and fear of discrimination (10%), HIV-1 acquisition (8%), or false-positive HIV-1 results (5%). The strongest correlate of pediatric vaccine trial participation was maternal willingness to be a vaccine trial participant herself; in univariate and multivariate models this was associated with a 17-fold increased likelihood of participation (HR 17.1; 95% CI 11.7-25; p < 0.001). We conclude from these results that immunizing infants against HIV-1 and participation in pediatric vaccine trials are generally acceptable to women at high risk for HIV-1 infection. It will be important to address barriers identified in this study and to include male partners when mobilizing communities for pediatric HIV-1 vaccine trials and immunization programs.

Vaccine-induced cytotoxic T lymphocytes against human immunodeficiency virus type 1 using two complementary in vitro stimulation strategies

Safety and immunogenicity of an adjuvanted protein therapeutic HIV-1 vaccine in subjects with HIV-1 infection: A randomised placebo-controlled study

ABSTRACTVaccine-elicited humoral immune responses comprise an array of antibody forms and specificities, with only a fraction contributing to protective host immunity. Elucidation of antibody effector functions responsible for protective immunity against human immunodeficiency virus type 1 (HIV-1) acquisition is a major goal for the HIV-1 vaccine field. Immunoglobulin A (IgA) is an important part of the host defense against pathogens; however, little is known about the role of vaccine-elicited IgA and its capacity to mediate antiviral functions. To identify the antiviral functions of HIV-1-specific IgA elicited by vaccination, we cloned HIV-1 envelope-specific IgA monoclonal antibodies (MAbs) by memory B cell cultures from peripheral blood mononuclear cells from an RV144 vaccinee and produced two IgA clonal cell lines (HG129 and HG130) producing native, nonrecombinant IgA MAbs. The HG129 and HG130 MAbs mediated phagocytosis by monocytes, and HG129 blocked HIV-1 Env glycoprotein binding to galactosylceramide, an alternative HIV-1 receptor. These findings elucidate potential antiviral functions of vaccine-elicited HIV-1 envelope-specific IgA that may act to block HIV-1 acquisition at the portal of entry by preventing HIV-1 binding to galactosylceramide and mediating antibody Fc receptor-mediated virion phagocytosis. Furthermore, these findings highlight the complex and diverse interactions of vaccine-elicited IgA with pathogens that depend on IgA fine specificity and form (e.g., multimeric or monomeric) in the systemic circulation and mucosal compartments.IMPORTANCE Host-pathogen interactions in vivo involve numerous immune mechanisms that can lead to pathogen clearance. Understanding the nature of antiviral immune mechanisms can inform the design of efficacious HIV-1 vaccine strategies. Evidence suggests that both neutralizing and nonneutralizing antibodies can mediate some protection against HIV in animal models. Although numerous studies have characterized the functional properties of HIV-1-specific IgG, more studies are needed on the functional attributes of HIV-1-specific IgA, specifically for vaccine-elicited IgA. Characterization of the functional properties of HIV-1 Env-specific IgA monoclonal antibodies from human vaccine clinical trials are critical toward understanding the capacity of the host immune response to block HIV-1 acquisition.