Rapid SIV Env-specific mucosal and serum antibody induction augments cellular immunity in protecting immunized, elite-controller macaques against high dose heterologous SIV challenge

The immunological impact of adenovirus early genes on vaccine-induced responses in mice and nonhuman primates

Adenovirus (Ad) is being explored for use in the prevention and treatment of a variety of infectious diseases and cancers. Ad with a deletion in early region 3 (ΔE3) provokes a stronger immune response than Ad with deletions in early regions 1 and E3 (ΔE1/ΔE3). The ΔE1/ΔE3 Ads are more popular because they can carry a larger transgene and because of the deleted E1 (E1A and E1B), are perceived safer for clinical use. Ad with a deletion in E1B55K (ΔE1B55K) has been in phase III clinical trials for use in cancer therapy in the US and has been approved for use in head and neck tumor therapy in China, demonstrating that Ad containing E1A are safe for clinical use. We have shown previously that ΔE1B55K Ad, even while promoting lower levels of an inserted transgene, promoted similar levels of transgene-specific immune responses as a ΔE3 Ad. Products of the Ad early region 4 (E4) limit the ability of cells to mount an innate immune response. Using this knowledge, we deleted the Ad E4 open reading frames 1-4 (E4orf1-4) from the ΔE1B55K Ad. Here, we show that innate cytokine network genes are elevated in the ΔE4 Ad-infected cells beyond that of ΔE3 Ad-infected cells. Further, in immunized mice the IgG2a subclass was favored as was the IgG1 subclass in immunized nonhuman primates. Thus, Ad E4 impacts immune responses in cells, in immunized mice, and immunized nonhuman primates. These Ad may offer advantages that are beneficial for clinical use.Importance: Adenovirus (Ad) is being explored for use in the prevention and treatment of a variety of infectious diseases and cancers. Here we provide evidence in cells, mice, and nonhuman primates supporting the notion that Ad early gene-products limit specific immune responses. Ad constructed with deletions in early genes and expressing HIV envelope protein was shown to induce greater HIV-specific cellular immune responses and higher titer antibodies compared to the parental Ad with the early genes. In addition to eliciting enhanced immunity, the deleted Ad possesses more space for insertion of additional or larger transgenes needed for targeting other infectious agents or cancers.

A Prime/Boost Vaccine Regimen Alters the Rectal Microbiome and Impacts Immune Responses and Viremia Control Post-Simian Immunodeficiency Virus Infection in Male and Female Rhesus Macaques

An efficacious human immunodeficiency virus (HIV) vaccine will likely require induction of both mucosal and systemic immune responses. We compared the immunogenicity and protective efficacy of two mucosal/systemic vaccine regimens and investigated their effects on the rectal microbiome. Rhesus macaques were primed twice mucosally with replication-competent adenovirus type 5 host range mutant (Ad5hr)-simian immunodeficiency virus (SIV) recombinants and boosted twice intramuscularly with ALVAC-SIV recombinant plus SIV gp120 protein or with DNA for SIV genes and rhesus interleukin-12 plus SIV gp120 protein. Controls received empty Ad5hr vector and alum adjuvant only. Both regimens elicited strong, comparable mucosal and systemic cellular and humoral immunity. Prevaccination rectal microbiomes of males and females differed and significantly changed over the course of immunization, most strongly in females after Ad5hr immunizations. Following repeated low-dose intrarectal SIV challenges, both vaccine groups exhibited modestly but significantly reduced acute viremia. Male and female controls exhibited similar acute viral loads; however, vaccinated females, but not males, exhibited lower levels of acute viremia, compared to same-sex controls. Few differences in adaptive immune responses were observed between the sexes. Striking differences in correlations of the rectal microbiome of males and females with acute viremia and immune responses associated with protection were seen and point to effects of the microbiome on vaccine-induced immunity and viremia control. Our study clearly demonstrates direct effects of a mucosal SIV vaccine regimen on the rectal microbiome and validates our previously reported SIV vaccine-induced sex bias. Sex and the microbiome are critical factors that should not be overlooked in vaccine design and evaluation.IMPORTANCE Differences in HIV pathogenesis between males and females, including immunity postinfection, have been well documented, as have steroid hormone effects on the microbiome, which is known to influence mucosal immune responses. Few studies have applied this knowledge to vaccine trials. We investigated two SIV vaccine regimens combining mucosal priming immunizations and systemic protein boosting. We again report a vaccine-induced sex bias, with female rhesus macaques but not males displaying significantly reduced acute viremia. The vaccine regimens, especially the mucosal primes, significantly altered the rectal microbiome. The greatest effects were in females. Striking differences between female and male macaques in correlations of prevalent rectal bacteria with viral loads and potentially protective immune responses were observed. Effects of the microbiome on vaccine-induced immunity and viremia control require further study by microbiome transfer. However, the findings presented highlight the critical importance of considering effects of sex and the microbiome in vaccine design and evaluation.

Diversity and Complexity of the Large Surface Protein Family in the Compacted Genomes of Multiple Pneumocystis Species

Pneumocystis, a major opportunistic pathogen in patients with a broad range of immunodeficiencies, contains abundant surface proteins encoded by a multicopy gene family, termed the major surface glycoprotein (Msg) gene superfamily. This superfamily has been identified in all Pneumocystis species characterized to date, highlighting its important role in Pneumocystis biology. In this report, through a comprehensive and in-depth characterization of 459 msg genes from 7 Pneumocystis species, we demonstrate, for the first time, the phylogeny and evolution of conserved domains in Msg proteins and provide a detailed description of the classification, unique characteristics, and phylogenetic relatedness of five Msg families. We further describe, for the first time, the relative expression levels of individual msg families in two rodent Pneumocystis species, the substantial variability of the msg repertoires in P. carinii from laboratory and wild rats, and the distinct features of the expression site for the classic msg genes in Pneumocystis from 8 mammalian host species. Our analysis suggests multiple functions for this superfamily rather than just conferring antigenic variation to allow immune evasion as previously believed. This study provides a rich source of information that lays the foundation for the continued experimental exploration of the functions of the Msg superfamily in Pneumocystis biology.IMPORTANCEPneumocystis continues to be a major cause of disease in humans with immunodeficiency, especially those with HIV/AIDS and organ transplants, and is being seen with increasing frequency worldwide in patients treated with immunodepleting monoclonal antibodies. Annual health care associated with Pneumocystis pneumonia costs ∼$475 million dollars in the United States alone. In addition to causing overt disease in immunodeficient individuals, Pneumocystis can cause subclinical infection or colonization in healthy individuals, which may play an important role in species preservation and disease transmission. Our work sheds new light on the diversity and complexity of the msg superfamily and strongly suggests that the versatility of this superfamily reflects multiple functions, including antigenic variation to allow immune evasion and optimal adaptation to host environmental conditions to promote efficient infection and transmission. These findings are essential to consider in developing new diagnostic and therapeutic strategies.

Mucosal vaccine efficacy against intrarectal SHIV is independent of anti-Env antibody response

It is widely believed that protection against acquisition of HIV or SIV infection requires anti-envelope (anti-Env) antibodies, and that cellular immunity may affect viral loads but not acquisition, except in special cases. Here we provide evidence to the contrary. Mucosal immunization may enhance HIV vaccine efficacy by eliciting protective responses at portals of exposure. Accordingly, we vaccinated macaques mucosally with HIV/SIV peptides, modified vaccinia Ankara-SIV (MVA-SIV), and HIV-gp120-CD4 fusion protein plus adjuvants, which consistently reduced infection risk against heterologous intrarectal SHIVSF162P4 challenge, both high dose and repeated low dose. Surprisingly, vaccinated animals exhibited no anti-gp120 humoral responses above background and Gag- and Env-specific T cells were induced but failed to correlate with viral acquisition. Instead, vaccine-induced gut microbiome alteration and myeloid cell accumulation in colorectal mucosa correlated with protection. Ex vivo stimulation of the myeloid cell-enriched population with SHIV led to enhanced production of trained immunity markers TNF-α and IL-6, as well as viral coreceptor agonist MIP1α, which correlated with reduced viral Gag expression and in vivo viral acquisition. Overall, our results suggest mechanisms involving trained innate mucosal immunity together with antigen-specific T cells, and also indicate that vaccines can have critical effects on the gut microbiome, which in turn can affect resistance to infection. Strategies to elicit similar responses may be considered for vaccine designs to achieve optimal protective efficacy.

Harnessing Antibody-Dependent Cellular Cytotoxicity To Control HIV-1 Infection

Passive administration of broadly neutralizing anti-human immunodeficiency virus type 1 (HIV-1) antibodies (bNAbs) has been recently suggested as a promising alternative therapeutic approach for HIV-1 infection. Although the success behind the studies that used this approach has been attributed to the potency and neutralization breadth of anti-HIV-1 antibodies, several lines of evidence support the idea that specific antibody-dependent effector functions, particularly antibody-dependent cellular cytotoxicity (ADCC), play a critical role in controlling HIV-1 infection. In this review, we showed that there is a direct association between the activation of ADCC and better clinical outcomes. This, in turn, suggests that ADCC could be harnessed to control HIV-1 infection. To this end, we addressed the passive administration of bNAbs capable of selectively activating ADCC responses to HIV-1 patients. Finally, we summarized the potential barriers that may impede the optimal activation of ADCC during HIV-1 infection and provided strategic solutions to overcome these barriers.

A flow cytometry based assay that simultaneously measures cytotoxicity and monocyte mediated antibody dependent effector activity

Antibody effector functions such as antibody dependent cellular cytotoxicity (ADCC) and antibody dependent cellular phagocytosis (ADCP) are considered important immunologic parameters following results from the RV144 clinical trial where a reduced risk of infection was associated with non-neutralizing antibody against the V1/V2 region of HIV envelope. The rapid and fluorometric ADCC (RFADCC) assay has been widely used to measure ADCC, however, the mechanism behind the activity measured remains unclear. Here, we demonstrate that monocytes acquire the PKH26 dye used in the RFADCC assay and that the commonly used RFADCC readout correlates with phagocytosis. The RFADCC assay was combined with an amine reactive dye staining to confirm target cell killing. Interestingly, the majority of RFADCC and amine indices were mutually exclusive. In fact, the amine reactive assay results correlated with results from another assays that directly measure NK cell antibody effector functions not associated with phagocytosis. Together, this combined assay offers the opportunity to discriminate monocytes and NK cell antibody effector functions simultaneously.

SIV-Specific Antibodies are Elicited by a Recombinant Fowlpox Virus Co-expressing SIV Gag and envT

Given the failures of past HIV-1 vaccine clinical trials, potential HIV-1 vaccine candidates should be rigorously screened in preclinical models including simian immunodeficiency virus (SIV) primate models and small animal models. In this study, we tested the immunogenicity of a recombinant fowlpox virus (rFPV) expressing the SIV gag and SIV envT (rFPV_sg-se) proteins in BALB/c mice, to establish a foundation for further development. rFPV_sg-se was constructed through homologous recombination techniques and purified through plaque screening assays using enhanced green fluorescent protein as the reporter gene. The integration, transcription, and translation of the SIV genes were measured by PCR (genomic DNA), RT-PCR (RNA), Western-blot, respectively. The levels of SIV-specific antibodies were assessed by ELISA following a single immunization (n = 18/group) or a prime-boost strategy (n = 24/group) with rFPV_sg-se and compared to FPV and PBS controls. Residual virus was measured in distant organs following immunization using PCR. SIV-specific IgG titers against gag and gp120 were detected following single vaccination and the prime-boost. As expected the titers were higher following the prime-boost approach. The levels of Gag- and gp120-specific antibodies were significantly higher than controls (p < 0.01) 14 days after the booster immunization. Residual rFPV_Sg-Se was detected in the muscle at the site of injection, but not in distant organs, from day 1-7 post immunization. In summary, rFPV_sg-se induced high levels of SIV-specific antibodies suggesting it may be a viable candidate for further development.

Mucosal B Cells Are Associated with Delayed SIV Acquisition in Vaccinated Female but Not Male Rhesus Macaques Following SIVmac251 Rectal Challenge

Many viral infections, including HIV, exhibit sex-based pathogenic differences. However, few studies have examined vaccine-related sex differences. We compared immunogenicity and protective efficacy of monomeric SIV gp120 with oligomeric SIV gp140 in a pre-clinical rhesus macaque study and explored a subsequent sex bias in vaccine outcome. Each immunization group (16 females, 8 males) was primed twice mucosally with replication-competent Ad-recombinants encoding SIV_smH4env/rev, SIV₂₃₉gag and SIV₂₃₉nefΔ_1–13 and boosted twice intramuscularly with SIV_mac239 monomeric gp120 or oligomeric gp140 in MF59 adjuvant. Controls (7 females, 5 males) received empty Ad and MF59. Up to 9 weekly intrarectal challenges with low-dose SIV_mac251 were administered until macaques became infected. We assessed vaccine-induced binding, neutralizing, and non-neutralizing antibodies, Env-specific memory B cells and plasmablasts/plasma cells (PB/PC) in bone marrow and rectal tissue, mucosal Env-specific antibodies, and Env-specific T-cells. Post-challenge, only one macaque (gp140-immunized) remained uninfected. However, SIV acquisition was significantly delayed in vaccinated females but not males, correlated with Env-specific IgA in rectal secretions, rectal Env-specific memory B cells, and PC in rectal tissue. These results extend previous correlations of mucosal antibodies and memory B cells with protective efficacy. The gp140 regimen was more immunogenic, stimulating elevated gp140 and cyclic V2 binding antibodies, ADCC and ADCP activities, bone marrow Env-specific PB/PC, and rectal gp140-specific IgG. However, immunization with gp120, the form of envelope immunogen used in RV144, the only vaccine trial to show some efficacy, provided more significant acquisition delay. Further over 40 weeks of follow-up, no gp120 immunized macaques met euthanasia criteria in contrast to 7 gp140-immunized and 2 control animals. Although males had higher binding antibodies than females, ADCC and ADCP activities were similar. The complex challenge outcomes may reflect differences in IgG subtypes, Fc glycosylation, Fc-R polymorphisms, and/or the microbiome, key areas for future studies. This first demonstration of a sex-difference in SIV vaccine-induced protection emphasizes the need for sex-balancing in vaccine trials. Our results highlight the importance of mucosal immunity and memory B cells at the SIV exposure site for protection.

Viral infections can have different disease courses in men and women. Following HIV infection, women generally exhibit lower viral loads and higher CD4 counts than men, but paradoxically progress faster to AIDS. Sex differences result from effects of X-linked genes and hormonal influences, and are believed to be largely based on immune response differences. Nevertheless, little is known about potential sex differences following vaccination. Here we report for the first time a sex bias in response to a SIV vaccine in rhesus macaques, showing that female animals were better protected against acquisition of SIV compared to males. The vaccine-induced immune responses that contributed to this better protection were viral-specific antibodies and immune antibody-secreting B cells, both at the local rectal site of SIV exposure. These results suggest that HIV/SIV vaccines should be better designed to target mucosal exposure sites. Additionally, they indicate that more vaccine studies should include animals of both sexes to address potential differences. Our study also illustrates that inclusion of both sexes can lead to greater complexity in vaccine trial outcomes, necessitating more in depth analyses. However, we believe sex balancing to be particularly important, as approximately 50% of HIV infections worldwide occur in women.

Recombinant rubella vectors elicit SIV Gag-specific T cell responses with cytotoxic potential in rhesus macaques

Live-attenuated rubella vaccine strain RA27/3 has been demonstrated to be safe and immunogenic in millions of children. The vaccine strain was used to insert SIV gag sequences and the resulting rubella vectors were tested in rhesus macaques alone and together with SIV gag DNA in different vaccine prime-boost combinations. We previously reported that such rubella vectors induce robust and durable SIV-specific humoral immune responses in macaques. Here, we report that recombinant rubella vectors elicit robust de novo SIV-specific cellular immune responses detectable for >10 months even after a single vaccination. The antigen-specific responses induced by the rubella vector include central and effector memory CD4(+) and CD8(+) T cells with cytotoxic potential. Rubella vectors can be administered repeatedly even after vaccination with the rubella vaccine strain RA27/3. Vaccine regimens including rubella vector and SIV gag DNA in different prime-boost combinations resulted in robust long-lasting cellular responses with significant increase of cellular responses upon boost. Rubella vectors provide a potent platform for inducing HIV-specific immunity that can be combined with DNA in a prime-boost regimen to elicit durable cellular immunity.

Balance of cellular and humoral immunity determines the level of protection by HIV vaccines in rhesus macaque models of HIV infection

A guiding principle for HIV vaccine design has been that cellular and humoral immunity work together to provide the strongest degree of efficacy. However, three efficacy trials of Ad5-vectored HIV vaccines showed no protection. Transmission was increased in two of the trials, suggesting that this vaccine strategy elicited CD4+ T-cell responses that provide more targets for infection, attenuating protection or increasing transmission. The degree to which this problem extends to other HIV vaccine candidates is not known. Here, we show that a gp120-CD4 chimeric subunit protein vaccine (full-length single chain) elicits heterologous protection against simian-human immunodeficiency virus (SHIV) or simian immunodeficiency virus (SIV) acquisition in three independent rhesus macaque repeated low-dose rectal challenge studies with SHIV162P3 or SIVmac251. Protection against acquisition was observed with multiple formulations and challenges. In each study, protection correlated with antibody-dependent cellular cytotoxicity specific for CD4-induced epitopes, provided that the concurrent antivaccine T-cell responses were minimal. Protection was lost in instances when T-cell responses were high or when the requisite antibody titers had declined. Our studies suggest that balance between a protective antibody response and antigen-specific T-cell activation is the critical element to vaccine-mediated protection against HIV. Achieving and sustaining such a balance, while enhancing antibody durability, is the major challenge for HIV vaccine development, regardless of the immunogen or vaccine formulation.

HIV-1 CD4-induced (CD4i) gp120 epitope vaccines promote B and T-cell responses that contribute to reduced viral loads in rhesus macaques

To target the HIV CD4i envelope epitope, we primed rhesus macaques with replicating Ad-rhFLSC (HIV-1BaLgp120 linked to macaque CD4 D1 and D2), with or without Ad-SIVgag and Ad-SIVnef. Macaques were boosted with rhFLSC protein. Memory T-cells in PBMC, bronchoalveolar lavage and rectal tissue, antibodies with neutralizing and ADCC activity, and Env-specific secretory IgA in rectal secretions were elicited. Although protective neutralizing antibody levels were induced, SHIVSF162P4 acquisition following rectal challenge was not prevented. Rapid declines in serum ADCC activity, Env-specific memory B cells in PBMC and bone marrow, and systemic and mucosal memory T cells were observed immediately post-challenge together with delayed anamnestic responses. Innate immune signaling resulting from persisting Ad replication and the TLR-4 booster adjuvant may have been in conflict and reoriented adaptive immunity. A different adjuvant paired with replicating Ad, or a longer post-prime interval allowing vector clearance before boosting might foster persistent T- and B-cell memory.

Comparative analysis of SIV-specific cellular immune responses induced by different vaccine platforms in rhesus macaques

To identify the most promising vaccine candidates for combinatorial strategies, we compared five SIV vaccine platforms including recombinant canary pox virus ALVAC, replication-competent adenovirus type 5 host range mutant RepAd, DNA, modified vaccinia Ankara (MVA), peptides and protein in distinct combinations. Three regimens used viral vectors (prime or boost) and two regimens used plasmid DNA. Analysis at necropsy showed that the DNA-based vaccine regimens elicited significantly higher cellular responses against Gag and Env than any of the other vaccine platforms. The T cell responses induced by most vaccine regimens disseminated systemically into secondary lymphoid tissues (lymph nodes, spleen) and effector anatomical sites (including liver, vaginal tissue), indicative of their role in viral containment at the portal of entry. The cellular and reported humoral immune response data suggest that combination of DNA and viral vectors elicits a balanced immunity with strong and durable responses able to disseminate into relevant mucosal sites.

Humoral immunity induced by mucosal and/or systemic SIV-specific vaccine platforms suggests novel combinatorial approaches for enhancing responses

Combinatorial HIV/SIV vaccine approaches targeting multiple arms of the immune system might improve protective efficacy. We compared SIV-specific humoral immunity induced in rhesus macaques by five vaccine regimens. Systemic regimens included ALVAC-SIVenv priming and Env boosting (ALVAC/Env); DNA immunization; and DNA plus Env co-immunization (DNA&Env). RepAd/Env combined mucosal replication-competent Ad-env priming with systemic Env boosting. A Peptide/Env regimen, given solely intrarectally, included HIV/SIV peptides followed by MVA-env and Env boosts. Serum antibodies mediating neutralizing, phagocytic and ADCC activities were induced by ALVAC/Env, RepAd/Env and DNA&Env vaccines. Memory B cells and plasma cells were maintained in the bone marrow. RepAd/Env vaccination induced early SIV-specific IgA in rectal secretions before Env boosting, although mucosal IgA and IgG responses were readily detected at necropsy in ALVAC/Env, RepAd/Env, DNA&Env and DNA vaccinated animals. Our results suggest that combined RepAd priming with ALVAC/Env or DNA&Env regimen boosting might induce potent, functional, long-lasting systemic and mucosal SIV-specific antibodies.

Rhesus macaque rectal and duodenal tissues exhibit B-cell sub-populations distinct from peripheral blood that continuously secrete antigen-specific IgA in short-term explant cultures

It is becoming increasingly obvious that evaluation of a vaccine aimed at preventing HIV infection should include assessment of induced immunity at mucosal sites of viral entry. Among the most salient immune responses are viral-specific antibodies. A recent report on IgA-secreting plasma cells in human duodenal explants prompted us to examine similar duodenal and rectal biopsies of rhesus macaques, a key animal model for pre-clinical HIV/SIV vaccine studies, and characterize the local resident B-cells. Here we report that non-human primate rectal explants possess similar levels of B-cells as duodenal explants. We characterize the antibody isotype expression on mucosal memory B-cells and show for the first time that the B-cell memory subsets of the duodenum and rectum are distinct from those of PBMC, not only by essentially lacking CD27(+) cells, as previously reported for uninfected macaques (Titanji et al., 2010), but also in being mostly IgD(-). SIV- and SHIV-infected macaques had fewer total IgA-secreting cells in rectal tissue compared to naïve macaques. As expected, the fractions of B-cells with surface expression of IgA were dominant in the rectal and duodenal explants whereas in PBMC IgG surface expression was dominant among IgD(-) B-cells. Mucosal antibody secreting cells were found to be predominantly plasma cells/plasma blasts based on their lack of response to stimulation. Importantly, short-term culture of rectal explants of SIV- and SHIV-positive animals led to secretion of Env-specific IgA into the culture supernatant which could be easily measured by ELISA. Collection of such culture supernatant over several days allows for accumulation of mucosal antibody in amounts that should enable antibody purification, characterization, and use in functional assays. Rectal explants can be readily obtained and unequivocally identify the mucosal tissue as the source of antibody. Overall they facilitate evaluation of mucosal vaccines.

High-throughput profiling of anti-glycan humoral responses to SIV vaccination and challenge

Recent progress toward an HIV vaccine highlights both the potential of vaccines to end the AIDS pandemic and the need to boost efficacy by incorporating additional vaccine strategies. Although many aspects of the immune response can contribute to vaccine efficacy, the key factors have not been defined fully yet. A particular area that may yield new insights is anti-glycan immune responses, such as those against the glycan shield that HIV uses to evade the immune system. In this study, we used glycan microarray technology to evaluate anti-glycan antibody responses induced by SIV vaccination and infection in a non-human primate model of HIV infection. This comprehensive profiling of circulating anti-glycan antibodies found changes in anti-glycan antibody levels after both vaccination with the Ad5hr-SIV vaccine and SIV infection. Notably, SIV infection produced generalized declines in anti-glycan IgM antibodies in a number of animals. Additionally, some infected animals generated antibodies to the Tn antigen, which is a cryptic tumor-associated antigen exposed by premature termination of O-linked glycans; however, the Ad5hr-SIV vaccine did not induce anti-Tn IgG antibodies. Overall, this study demonstrates the potential contributions that glycan microarrays can make for HIV vaccine development.

Haplessly hoping: macaque major histocompatibility complex made easy

Major histocompatibility complex (MHC) gene products control the repertoire of T cell responses that an individual may create against pathogens and foreign tissues. This text will review the current understanding of MHC genetics in nonhuman primates, with a focus on Mauritian-origin cynomolgus macaques (Macaca fascicularis) and Indian-origin rhesus macaques (Macaca mulatta). These closely related macaque species provide important experimental models for studies of infectious disease pathogenesis, vaccine development, and transplantation research. Recent advances resulting from the application of several cost effective, high-throughput approaches, with deep sequencing technologies have revolutionized our ability to perform MHC genotyping of large macaque cohorts. Pyrosequencing of cDNA amplicons with a Roche/454 GS Junior instrument, provides excellent resolution of MHC class I allelic variants with semi-quantitative estimates of relative levels of transcript abundance. Introduction of the Illumina MiSeq platform significantly increased the sample throughput, since the sample loading workflow is considerably less labor intensive, and each instrument run yields approximately 100-fold more sequence data. Extension of these sequencing methods from cDNA to genomic DNA amplicons further streamlines the experimental workflow and opened opportunities for retrospective MHC genotyping of banked DNA samples. To facilitate the reporting of MHC genotypes, and comparisons between groups of macaques, this text also introduces an intuitive series of abbreviated rhesus MHC haplotype designations based on a major Mamu-A or Mamu-B transcript characteristic for ancestral allele combinations. The authors believe that the use of MHC-defined macaques promises to improve the reproducibility, and predictability of results from pre-clinical studies for translation to humans.

Role of monocytes in mediating HIV-specific antibody-dependent cellular cytotoxicity

Antibodies (Abs) that mediate antibody-dependent cellular cytotoxicity (ADCC) activity against HIV-1 are of major interest. A widely used method to measure ADCC Abs is the rapid and fluorometric antibody-dependent cellular cytotoxicity (RFADCC) assay. Antibody-dependent killing of a labelled target cell line by PBMC is assessed by loss of intracellular CFSE but retention of membrane dye PKH26 (CFSE-PKH26+). Cells of this phenotype are assumed to be derived from CFSE+PKH26+ target cells killed by NK cells. We assessed the effector cells that mediate ADCC in this assay. Backgating analysis and phenotyping of CFSE-PKH26+ revealed that the RFADCC assay's readout mainly represents CD3-CD14+ monocytes taking up the PKH26 dye. This was confirmed for 53 HIV+plasma-purified IgG samples when co-cultured with PBMC from three separate healthy donors. Emergence of the CFSE-PKH26+ monocyte population was observed upon co-culture of targets with purified monocytes but not with purified NK cells. Image flow cytometry and microscopy showed a monocyte-specific interaction with target cells without typical morphological changes associated with phagocytosis, suggesting a monocyte-mediated ADCC process. We conclude that the RFADCC assay primarily reflects Ab-mediated monocyte function. Further studies on the immunological importance of HIV-specific monocyte-mediated ADCC are warranted.

NK and CD4+ T cell cooperative immune responses correlate with control of disease in a macaque simian immunodeficiency virus infection model

Control of infectious disease may be accomplished by successful vaccination or by complex immunologic and genetic factors favoring Ag-specific multicellular immune responses. Using a rhesus macaque model, we evaluated Ag-specific T cell-dependent NK cell immune responses in SIV-infected macaques, designated "controlling" or "noncontrolling" based on long-term chronic viremia levels, to determine whether NK cell effector functions contribute to control of SIV infection. We observed that Gag stimulation of macaque PBMCs induced subset-specific NK cell responses in SIV-controlling but not SIV-noncontrolling animals, as well as that circulatory NK cell responses were dependent on Ag-specific IL-2 production by CD4(+) central memory T cells. NK cell activation was blocked by anti-IL-2-neutralizing Ab and by CD4(+) T cell depletion, which abrogated the Gag-specific responses. Among tissue-resident cells, splenic and circulatory NK cells displayed similar activation profiles, whereas liver and mucosal NK cells displayed a decreased activation profile, similar in SIV-controlling and -noncontrolling macaques. Lack of T cell-dependent NK cell function was rescued in SIV-noncontrolling macaques through drug-mediated control of viremia. Our results indicate that control of disease progression in SIV-controlling macaques is associated with cooperation between Ag-specific CD4(+) T cells and NK cell effector function, which highlight the importance of such cell-to-cell cooperativity in adaptive immunity and suggest that this interaction should be further investigated in HIV vaccine development and other prophylactic vaccine approaches.

Replicating adenovirus-simian immunodeficiency virus (SIV) vectors efficiently prime SIV-specific systemic and mucosal immune responses by targeting myeloid dendritic cells and persisting in rectal macrophages, regardless of immunization route

Although priming with replicating adenovirus type 5 host range mutant (Ad5hr)-human immunodeficiency virus (HIV)/simian immunodeficiency virus (SIV) recombinants, followed by HIV/SIV envelope boosting, has proven highly immunogenic, resulting in protection from SIV/simian-human immunodeficiency virus (SHIV) challenges, Ad5hr recombinant distribution, replication, and persistence have not been examined comprehensively in nonhuman primates. We utilized Ad5hr-green fluorescent protein and Ad5hr-SIV recombinants to track biodistribution and immunogenicity following mucosal priming of rhesus macaques by the intranasal/intratracheal, sublingual, vaginal, or rectal route. Ad recombinants administered by all routes initially targeted macrophages in bronchoalveolar lavage (BAL) fluid and rectal tissue, later extending to myeloid dendritic cells in BAL fluid with persistent expression in rectal mucosa 25 weeks after the last Ad immunization. Comparable SIV-specific immunity, including cellular responses, serum binding antibody, and mucosal secretory IgA, was elicited among all groups. The ability of the vector to replicate in multiple mucosal sites irrespective of delivery route, together with the targeting of macrophages and professional antigen-presenting cells, which provide potent immunogenicity at localized sites of virus entry, warrants continued use of replicating Ad vectors.

Replicating adenovirus-simian immunodeficiency virus (SIV) recombinant priming and envelope protein boosting elicits localized, mucosal IgA immunity in rhesus macaques correlated with delayed acquisition following a repeated low-dose rectal SIV(mac251) challenge

We have shown that sequential replicating adenovirus type 5 host range mutant human immunodeficiency virus/simian immunodeficiency virus (HIV/SIV) recombinant priming delivered first intranasally (i.n.) plus orally and then intratracheally (i.t.), followed by envelope protein boosting, elicits broad cellular immunity and functional, envelope-specific serum and mucosal antibodies that correlate with protection from high-dose SIV and simian/human immunodeficiency virus (SHIV) challenges in rhesus macaques. Here we extended these studies to compare the standard i.n./i.t. regimen with additional mucosal administration routes, including sublingual, rectal, and vaginal routes. Similar systemic cellular and humoral immunity was elicited by all immunization routes. Central and effector memory T cell responses were also elicited by the four immunization routes in bronchoalveolar lavage fluid and jejunal, rectal, and vaginal tissue samples. Cellular responses in vaginal tissue were more compartmentalized, being induced primarily by intravaginal administration. In contrast, all immunization routes elicited secretory IgA (sIgA) responses at multiple mucosal sites. Following a repeated low-dose intrarectal (i.r.) challenge with SIV(mac251) at a dose transmitting one or two variants, protection against acquisition was not achieved except in one macaque in the i.r. immunized group. All immunized macaques exhibited reduced peak viremia compared to that of controls, correlated inversely with prechallenge serum antienvelope avidity, antibody-dependent cellular cytotoxicity (ADCC) titers, and percent antibody-dependent cell-mediated viral inhibition. Both antibody avidity and ADCC titers were correlated with the number of exposures required for infection. Notably, we show for the first time a significant correlation of vaccine-induced sIgA titers in rectal secretions with delayed acquisition. Further investigation of the characteristics and properties of the sIgA should elucidate the mechanism leading to this protective effect.

Strong viremia control in vaccinated macaques does not prevent gradual Th17 cell loss from central memory

It has been proposed that microbial translocation might play a role in chronic immune activation during HIV/SIV infection. Key roles in fighting bacterial and fungal infections have been attributed to Th17 and Tc17 cells. Th17 cells can be infected with HIV/SIV, however whether effective vaccination leads to their maintenance following viral challenge has not been addressed. Here we retrospectively investigated if a vaccine regimen that potently reduced viremia post-challenge preserved Th17 and Tc17 cells, thus adding benefit in the absence of sterilizing protection. Rhesus macaques were previously vaccinated with replication-competent Adenovirus recombinants expressing HIVtat and HIVenv followed by Tat and gp140 protein boosting. Upon SHIV(89.6P) challenge, the vaccines exhibited a significant 4 log reduction in chronic viremia compared to sham vaccinated controls which rapidly progressed to AIDS [39]. Plasma and cryopreserved PBMC samples were examined pre-challenge and during acute and chronic infection. Control macaques exhibited a rapid loss of CD4(+) cells, including Th17 cells. Tc17 cells tended to decline over the course of infection although significance was not reached. Immune activation, assessed by Ki-67 expression, was associated with elevated chronic viremia of the controls. Significantly increased plasma IFN-γ levels were also observed. No increase in plasma LPS levels were observed suggesting a lack of microbial translocation. In contrast, vaccinated macaques had no evidence of immune activation within the chronic phase and preserved both CD4(+) T-cells and Tc17 cells in PBMC. Nevertheless, they exhibited a gradual, significant loss of Th17 cells which concomitantly displayed significantly higher CCR6 expression over time. The gradual Th17 cell decline may reflect mucosal homing to inflammatory sites and/or slow depletion due to ongoing low levels of SHIV replication. Our results suggest that potent viremia reduction during chronic SHIV infection will delay but not prevent the loss of Th17 cells.