Vaccine-Induced Protection from Homologous Tier 2 SHIV Challenge in Nonhuman Primates Depends on Serum-Neutralizing Antibody Titers.

Passive administration of HIV neutralizing antibodies (nAbs) can protect macaques from hard-to-neutralize (tier 2) chimeric simian-human immunodeficiency virus (SHIV) challenge. However, conditions for nAb-mediated protection after vaccination have not been established. Here, we selected groups of 6 rhesus macaques with either high or low serum nAb titers from a total of 78 animals immunized with recombinant native-like (SOSIP) Env trimers. Repeat intrarectal challenge with homologous tier 2 SHIVBG505 led to rapid infection in unimmunized and low-titer animals. High-titer animals, however, demonstrated protection that was gradually lost as nAb titers waned over time. An autologous serum ID50 nAb titer of ∼1:500 afforded more than 90% protection from medium-dose SHIV infection. In contrast, antibody-dependent cellular cytotoxicity and T cell activity did not correlate with protection. Therefore, Env protein-based vaccination strategies can protect against hard-to-neutralize SHIV challenge in rhesus macaques by inducing tier 2 nAbs, provided appropriate neutralizing titers can be reached and maintained.

Elicitation of Robust Tier 2 Neutralizing Antibody Responses in Nonhuman Primates by HIV Envelope Trimer Immunization Using Optimized Approaches.

The development of stabilized recombinant HIV envelope trimers that mimic the virion surface molecule has increased enthusiasm for a neutralizing antibody (nAb)-based HIV vaccine. However, there is limited experience with recombinant trimers as immunogens in nonhuman primates, which are typically used as a model for humans. Here, we tested multiple immunogens and immunization strategies head-to-head to determine their impact on the quantity, quality, and kinetics of autologous tier 2 nAb development. A bilateral, adjuvanted, subcutaneous immunization protocol induced reproducible tier 2 nAb responses after only two immunizations 8 weeks apart, and these were further enhanced by a third immunization with BG505 SOSIP trimer. We identified immunogens that minimized non-neutralizing V3 responses and demonstrated that continuous immunogen delivery could enhance nAb responses. nAb responses were strongly associated with germinal center reactions, as assessed by lymph node fine needle aspiration. This study provides a framework for preclinical and clinical vaccine studies targeting nAb elicitation.

Sequential and Simultaneous Immunization of Rabbits with HIV-1 Envelope Glycoprotein SOSIP.664 Trimers from Clades A, B and C.

We have investigated the immunogenicity in rabbits of native-like, soluble, recombinant SOSIP.664 trimers based on the env genes of four isolates of human immunodeficiency virus type 1 (HIV-1); specifically BG505 (clade A), B41 (clade B), CZA97 (clade C) and DU422 (clade C). The various trimers were delivered either simultaneously (as a mixture of clade A + B trimers) or sequentially over a 73-week period. Autologous, Tier-2 neutralizing antibody (NAb) responses were generated to the clade A and clade B trimers in the bivalent mixture. When delivered as boosting immunogens to rabbits immunized with the clade A and/or clade B trimers, the clade C trimers also generated autologous Tier-2 NAb responses, the CZA97 trimers doing so more strongly and consistently than the DU422 trimers. The clade C trimers also cross-boosted the pre-existing NAb responses to clade A and B trimers. We observed heterologous Tier-2 NAb responses albeit inconsistently, and with limited overall breath. However, cross-neutralization of the clade A BG505.T332N virus was consistently observed in rabbits immunized only with clade B trimers and then boosted with clade C trimers. The autologous NAbs induced by the BG505, B41 and CZA97 trimers predominantly recognized specific holes in the glycan shields of the cognate virus. The shared location of some of these holes may account for the observed cross-boosting effects and the heterologous neutralization of the BG505.T332N virus. These findings will guide the design of further experiments to determine whether and how multiple Env trimers can together induce more broadly neutralizing antibody responses.

Dynamic variation in the cellular origin of HIV type 1 during treatment of tuberculosis in dually infected subjects.

HIV-1 replication remains elevated in dually infected HIV-1/TB subjects at completion of antituberculosis therapy. A viral immunocapture assay was used to examine the cellular origin of HIV-1 within plasma from HIV-1/TB subjects at time of diagnosis of pulmonary TB, at end of TB treatment, and 6 months after completion of treatment. Asymptomatic HIV-1-infected subjects without TB (HIV-1/C) served as controls. Both activated immature macrophage (CD36(+)) and CD4 T cell (CD26(+)) compartments contributed to viral load. Changes in the activation status of either cellular compartment paralleled their contribution to viral load. Levels of HIV-1 originating from activated (HLA-DR(+)) cells and from CD36(+) and CD26(+) mononuclear cells resolved to levels observed in HIV-1/C by the end of treatment. HIV-1 isolated by anti-CD3 immunocapture from HIV-1/TB patients remained significantly higher than from HIV-1/C patients at the end of TB treatment and at 12 months follow-up. Therefore, viral production by lymphocytes extends well beyond the completion of TB treatment.

GB virus-C--a virus without a disease: we cannot give it chronic fatigue syndrome.

BACKGROUND: Chronic fatigue syndrome (CFS) is an illness in search of an infectious etiology. GB virus-C (GBV-C) virus is a flavivirus with cell tropism and host defense induction qualities compatible with a role in producing the syndrome. The GBV-C genome is detectable in 4% of the population and 12% of the population is seropositive. The present study evaluated the association between infection with GBV and CFS. METHODS: We used a commercial EIA to detect antibodies against the GBV-C E2 protein and a quantitative real-time RT-PCR assay to detect active GBV-C infection. Sera were from a case control study of CFS in Atlanta, Georgia. The Fisher's exact two-tailed test was used for statistical analysis. RESULTS: Two of 12 CFS patients and one of 21 controls were seropositive for prior GBV-C infection and one control had viral RNA detected, indicating active infection. The results are not statistically different. CONCLUSION: We found no evidence that active or past infection with GBV is associated with CFS.

Resistance to HIV-1 infection: lessons learned from studies of highly exposed persistently seronegative (HEPS) individuals.

The medical, social, and economic impact of the human immunodeficiency virus (HIV) epidemic has underscored the need to quickly develop effective control strategies. Vigorous efforts to develop a vaccine and therapeutic agents have not yet succeeded in containing the spread of the virus. Studies of persons who remain uninfected despite extensive exposure to HIV continue to provide valuable information on mechanisms of natural protection, which can then be applied to vaccine design. Natural resistance to infection has been studied in multiple high-risk cohorts, with resistance attributed to a combination of innate, genetic, and acquired immune system-mediated mechanisms. The relative contributions of these factors to natural resistance to HIV-1 infection and possible ways in which they can be applied to vaccine design are discussed.

Immune activation and induction of HIV-1 replication within CD14 macrophages during acute Plasmodium falciparum malaria coinfection.

OBJECTIVES: To determine the impact of Plasmodium falciparum malaria coinfection and its treatment on cellular reservoirs of viral replication in HIV-1-infected persons and to relate this to changes in systemic immune activation. METHODS: Plasma samples were obtained from HIV-1-infected individuals (n = 10) at diagnosis of acute malaria, 4 weeks after parasite clearance and from HIV-infected aparasitemic controls (n = 10). Immunomagnetic HIV-1 capture analysis was used to determine the cellular origin of cell-free virus particles present in all 30 plasma samples and indices of immune activation were measured using enzyme-linked immunosorbent assays. RESULTS: Compared with controls, the detectable proportion of HIV-1 particles derived from CD14 macrophages and CD26 lymphocytes was increased in persons with acute malaria coinfection and correlated with markedly increased plasma concentrations of both proinflammatory cytokines and soluble markers of macrophage and lymphocyte activation. Parasite clearance following treatment with antimalarial drugs resulted in decreased detection of HIV-1 particles derived from the CD14 macrophage cell subset and correlated with a marked diminution in systemic immune activation. CONCLUSIONS: Acute P. falciparum malaria coinfection impacts virus-host dynamics in HIV-1-infected persons at the cellular level, notably showing a reversible induction of HIV-1 replication in CD14 macrophages that is associated with changes in immune activation.

Tuberculosis unleashed: the impact of human immunodeficiency virus infection on the host granulomatous response to Mycobacterium tuberculosis.

The granuloma plays a critical role in the host immune response to Mycobacterium tuberculosis, containing the organism and confining it in a latent state in most infected individuals. Indeed, approximately one-third of the world's population has latent M. tuberculosis infection. However, over the past decade, the human immunodeficiency virus type 1 (HIV-1) pandemic has profoundly affected the incidence and clinicopathological features of tuberculosis. This review examines the immunological mechanisms whereby HIV-1 impairs the establishment, maintenance and function of the tuberculous granuloma.

Polymorphisms in the CCR5 coding and noncoding regions among HIV type 1-exposed, persistently seronegative female sex-workers from Thailand.

Resistance to HIV-1 infection despite repeated exposures has been associated with one or more HIV-specific responses, enhanced nonspecific immune modifications, and/or host genetic polymorphisms in certain individuals (highly exposed, persistently seronegative, HEPS). In the present investigation, we focused on the CCR5 gene polymorphisms and the association of such mutations to resistance to HIV-1 infection among 12 HEPS women in Chiang Rai, northern Thailand, and compared our findings with data from 10 HIV-1-infected and 9 HIV-1-uninfected unexposed women from the same geographic area. Although we have previously shown that none of the Thai women carried the Delta32 mutation, further analysis of the CCR5 coding gene region revealed that none of the women had other mutations that affect coreceptor activity (C101X or FS299) or chemokine responses (C20S, A29S, L55Q, C178R). Analysis of the CCR5 promoter region revealed that the CCR5 haplogroup C (HHC; 60%) was the predominant haplogroup among these women. Comparative analysis of the frequencies of different haplogroups among the three groups did not reveal any statistically significant differences (p > 0.05). However, we did find that two individuals from the HEPS group were homozygous for HHF*2 (the CCR2b- 64I bearing haplogroup) compared to none from the HIV-1-infected and -uninfected groups. There was no detectable difference in specific CCR5 haplogroups and their ability to mediate env fusion or to mediate HIV-1 infection in vitro. These data suggest that homozygosity of the HHF*2 haplogroup may be one of the factors that mediate resistance to HIV-1 infection in this cohort of HEPS women.

DNA/MVA vaccine for HIV type 1: effects of codon-optimization and the expression of aggregates or virus-like particles on the immunogenicity of the DNA prime.

Recently, a vaccine consisting of DNA priming followed by boosting with modified vaccinia Ankara (MVA) has provided long-term protection of rhesus macaques against a virulent challenge with a chimera of simian and human immunodeficiency viruses. Here, we report studies on the development of the DNA component for a DNA/MVA HIV vaccine for humans. Specifically, we assess the ability of a codon-optimized Gag-expressing DNA and two noncodon-optimized Gag-Pol-Env-expressing DNAs to prime the MVA booster dose. The codon-optimized DNA expressed virus-like particles (VLPs), whereas one of the noncodon-optimized DNAs expressed VLPs and the other expressed aggregates of HIV proteins. The MVA boost expressed Gag-Pol and Env and produced VLPs. Immunogenicity studies in macaques used one intramuscular prime with 600 microg of DNA and two intramuscular boosts with 1 x 10(8) pfu of MVA at weeks 8 and 30. The codon-optimized and noncodon-optimized DNAs proved similar in their ability to prime anti-Gag T cell responses. The aggregate and VLP-expressing Gag-Pol-Env DNAs also showed no significant differences in their ability to prime anti-Env Ab responses. The second MVA booster dose did not increase the peak CD4 and CD8 T cell responses, but increased anti-Env Ab titers by 40- to 90-fold. MVA-only immunizations elicited 10-100 times lower frequencies of T cells and 2-4 lower titers of anti-Env Ab than the Gag-Pol-Env DNA/MVA immunizations. Based on the breadth of the T cell response and a trend toward higher titers of anti-Env Ab, we are moving forward with human trials of the noncodon-optimized VLP-expressing DNA.

Multiprotein HIV type 1 clade B DNA/MVA vaccine: construction, safety, and immunogenicity in Macaques.

Recently, a simian/human immunodeficiency virus (SHIV) vaccine consisting of priming with a Gag-Pol-Env-expressing DNA and boosting with a Gag-Pol-Env-expressing recombinant modified vaccinia Ankara (rMVA) has successfully controlled a virulent SHIV challenge in a macaque model. In this, and the accompanying paper, we report on the construction and testing of a Gag-Pol-Env DNA/MVA vaccine for HIV-1/AIDS. The DNA vaccine, pGA2/JS2, expresses aggregates of Gag proteins and includes safety mutations that render it integration, reverse transcription, and packaging defective. The rMVA vaccine, MVA/HIV 48, is integration and reverse transcription defective and has a truncated Env to enhance expression on the plasma membrane. In a study in rhesus macaques, priming with pGA2/JS2 and boosting with MVA/HIV 48 raised high frequencies of T cells for Gag and Env and lower frequencies of T cells for PR, RT, and Tat. Stimulations with five peptide pools for Gag and seven peptide pools for Env revealed epitopes for cellular immune responses throughout Gag and Env. On average, CD4 T cells from the vaccinated animals recognized 7.1 peptide pools and CD8 T cells, 3.2 peptide pools. Both the height and the breadth of the elicited cellular response provide hope that this multiprotein DNA/MVA vaccine will successfully control clade B isolates of HIV-1, as well as contribute to the control of other clades and recombinant forms of HIV-1/AIDS.

Coreceptor utilization of HIV type 1 subtype E viral isolates from Thai men with HIV type 1-infected and uninfected wives.

HIV-1 coreceptors CCR5 and CXCR4 play an important role in viral entry and pathogenesis. To better understand the role of viral tropism in HIV-1 transmission, we examined the coreceptor utilization of viral isolates obtained from men enrolled in a study of heterosexual transmission in northern Thailand. Viral isolates were obtained from HIV-1-positive males who had either HIV-1-infected spouses (RM; n = 5) or HIV-1-uninfected spouses (HM; n = 10). Viral isolates from 1 of the 5 RM males and 2 of the 10 HM males were CCR5 tropic, whereas isolates from 3 RM males and 6 of the HM male isolates were CXCR4 tropic. Of the nine X4-tropic isolates, seven also used at least one of the following coreceptors: CCR8, CCR1, CCR2b, or CX3CR1, and none employed CCR5 as an additional coreceptor. More importantly, three isolates, RM-15, HM-13, and HM-16 (one from a transmitter and two from nontransmitter), did not infect GHOST4.cl.34 cells expressing any of the known coreceptors. Further analysis using MAGI-plaque assays, which allow visualization of infected cells, revealed that RM-15 had low numbers of infected cells in MAGI-R5 and MAGI-X4 cultures, whereas HM-13 and HM-16 had high levels of plaques in MAGI-X4 cultures. Replication kinetics using activated lymphocytes revealed that these three isolates replicated in CCR5(+/+) as well as CCR5(-/-) peripheral blood mononuclear cells, suggesting that these isolates did not have an absolute requirement of CCR5 for viral entry. All three isolates were sensitive to the X4-antagonistic compounds T-22 and AMD3100. Analysis of the C2V3 region did not reveal any significant structural differences between any of the Thai subtype E isolates. Thus, there was no association between the pattern of coreceptor usage and transmissibility among these subtype E HIV-1 isolates.

A Blueprint for HIV Vaccine Discovery.

Despite numerous attempts over many years to develop an HIV vaccine based on classical strategies, none has convincingly succeeded to date. A number of approaches are being pursued in the field, including building upon possible efficacy indicated by the recent RV144 clinical trial, which combined two HIV vaccines. Here, we argue for an approach based, in part, on understanding the HIV envelope spike and its interaction with broadly neutralizing antibodies (bnAbs) at the molecular level and using this understanding to design immunogens as possible vaccines. BnAbs can protect against virus challenge in animal models, and many such antibodies have been isolated recently. We further propose that studies focused on how best to provide T cell help to B cells that produce bnAbs are crucial for optimal immunization strategies. The synthesis of rational immunogen design and immunization strategies, together with iterative improvements, offers great promise for advancing toward an HIV vaccine.

Highly complex neutralization determinants on a monophyletic lineage of newly transmitted subtype C HIV-1 Env clones from India.

Little is known about the neutralization properties of HIV-1 in India to optimally design and test vaccines. For this reason, a functional Env clone was obtained from each of ten newly acquired, heterosexually transmitted HIV-1 infections in Pune, Maharashtra. These clones formed a phylogenetically distinct genetic lineage within subtype C. As Env-pseudotyped viruses the clones were mostly resistant to IgG1b12, 2G12 and 2F5 but all were sensitive to 4E10. When compared to a large multi-subtype panel of Env-pseudotyped viruses (subtypes B, C and CRF02_AG) in neutralization assays with a multi-subtype panel of HIV-1-positive plasma samples, the Indian Envs were remarkably complex. With the exception of the Indian Envs, results of a hierarchical clustering analysis showed a strong subtype association with the patterns of neutralization susceptibility. From these patterns we were able to identify 19 neutralization cluster-associated amino acid signatures in gp120 and 14 signatures in the ectodomain and cytoplasmic tail of gp41. We conclude that newly transmitted Indian Envs are antigenically complex in spite of close genetic similarity. Delineation of neutralization-associated amino acid signatures provides a deeper understanding of the antigenic structure of HIV-1 Env.