Macrophage- and CD4+ T cell-derived SIV differ in glycosylation, infectivity and neutralization sensitivity.

The human immunodeficiency virus (HIV) envelope protein (Env) mediates viral entry into host cells and is the primary target for the humoral immune response. Env is extensively glycosylated, and these glycans shield underlying epitopes from neutralizing antibodies. The glycosylation of Env is influenced by the type of host cell in which the virus is produced. Thus, HIV is distinctly glycosylated by CD4+ T cells, the major target cells, and macrophages. However, the specific differences in glycosylation between viruses produced in these cell types have not been explored at the molecular level. Moreover, it remains unclear whether the production of HIV in CD4+ T cells or macrophages affects the efficiency of viral spread and resistance to neutralization. To address these questions, we employed the simian immunodeficiency virus (SIV) model. Glycan analysis implied higher relative levels of oligomannose-type N-glycans in SIV from CD4+ T cells (T-SIV) compared to SIV from macrophages (M-SIV), and the complex-type N-glycans profiles seem to differ between the two viruses. Notably, M-SIV demonstrated greater infectivity than T-SIV, even when accounting for Env incorporation, suggesting that host cell-dependent factors influence infectivity. Further, M-SIV was more efficiently disseminated by HIV binding cellular lectins. We also evaluated the influence of cell type-dependent differences on SIV's vulnerability to carbohydrate binding agents (CBAs) and neutralizing antibodies. T-SIV demonstrated greater susceptibility to mannose-specific CBAs, possibly due to its elevated expression of oligomannose-type N-glycans. In contrast, M-SIV exhibited higher susceptibility to neutralizing sera in comparison to T-SIV. These findings underscore the importance of host cell-dependent attributes of SIV, such as glycosylation, in shaping both infectivity and the potential effectiveness of intervention strategies.

Genetic barrier to resistance: a critical parameter for efficacy of neutralizing monoclonal antibodies against SARS-CoV-2 in a nonhuman primate model.

The potency of antibody neutralization in cell culture has been used as the key criterion for selection of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) for clinical development. As other aspects may also influence the degree of protection in vivo, we compared the efficacy of two neutralizing monoclonal antibodies (TRES6 and 4C12) targeting different epitopes of the receptor binding domain (RBD) of SARS-CoV-2 in a prophylactic setting in rhesus monkeys. All four animals treated with TRES6 had reduced viral loads in the upper respiratory tract 2 days after naso-oropharyngeal challenge with the Alpha SARS-CoV-2 variant. Starting 2 days after challenge, mutations conferring resistance to TRES6 were dominant in two of the rhesus monkeys, with both animals failing to maintain reduced viral loads. Consistent with its lower serum neutralization titer at the day of challenge, prophylaxis with 4C12 tended to suppress viral load at day 2 less efficiently than TRES6. However, a week after challenge, mean viral loads in the lower respiratory tract in 4C12-treated animals were lower than in the TRES6 group and no mutations conferring resistance to 4C12 could be detected in viral isolates from nasal or throat swabs. Thus, genetic barrier to resistance seems to be a critical parameter for the efficacy of prophylaxis with monoclonal antibodies against SARS-CoV-2. Furthermore, comparison of antibody concentrations in respiratory secretions to those in serum shows reduced distribution of the 4C12 antibody into respiratory secretions and a delay in the appearance of antibodies in bronchoalveolar lavage fluid compared to their appearance in secretions of the upper respiratory tract.IMPORTANCEMonoclonal antibodies are a powerful tool for the prophylaxis and treatment of acute viral infections. Hence, they were one of the first therapeutic agents licensed for the treatment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Oftentimes, the main criterion for the selection of antibodies for clinical development is their potency of neutralization in cell culture. By comparing two antibodies targeting the Spike protein of SARS-CoV-2, we now observed that the antibody that neutralized SARS-CoV-2 more efficiently in cell culture suppressed viral load in challenged rhesus monkeys to a lesser extent. Extraordinary rapid emergence of mutants of the challenge virus, which had lost their sensitivity to the antibody, was identified as the major reason for the reduced efficacy of the antibody in rhesus monkeys. Therefore, the viral genetic barrier to resistance to antibodies also affects their efficacy.

Urinary cytokine measurements do not reflect surgery-induced inflammation in rhesus macaques.

Measurement of the health and disease status of free-ranging primates is often limited by a lack of available biomarkers of immune activation and inflammation that can be applied noninvasively via the measurement of urine or fecal samples. Here, we evaluate the potential usefulness of noninvasive urinary measurements of a number of cytokines, chemokines, and other markers of inflammation and infection. We took advantage of surgery-associated inflammation in seven captive rhesus macaques, collecting urine samples before and after the medical interventions. We measured these urine samples for 33 different markers of inflammation and immune activation that are known to be responsive to inflammation and infection in rhesus macaque blood samples, via the Luminex platform. We also measured all samples for concentrations of the soluble urokinase plasminogen activator receptor (suPAR), which we had validated in a prior study as an effective biomarker of inflammation. Despite urine samples being collected in captivity under ideal conditions (clean, no contamination with feces or soil, frozen quickly), 13/33 biomarkers measured via Luminex were found at concentrations below detection limits in >50% of samples. Of the remaining 20 markers, only 2 showed significant increases in response to surgery-IL18 and MPO (myeloperoxidase). However, suPAR measurements of the same samples show a consistent marked increase in response to surgery that is absent from the patterns of IL18 and MPO measurement. Given that our samples were collected under conditions that are greatly preferable to those usually encountered in the field, urinary cytokine measurements via the Luminex platform seem overall unpromising for primate field studies.

SARS-CoV-2 and SARS-CoV Spike-Mediated Cell-Cell Fusion Differ in Their Requirements for Receptor Expression and Proteolytic Activation.

Severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) infects cells through interaction of its spike protein (SARS2-S) with angiotensin-converting enzyme 2 (ACE2) and activation by proteases, in particular transmembrane protease serine 2 (TMPRSS2). Viruses can also spread through fusion of infected with uninfected cells. We compared the requirements of ACE2 expression, proteolytic activation, and sensitivity to inhibitors for SARS2-S-mediated and SARS-CoV-S (SARS1-S)-mediated cell-cell fusion. SARS2-S-driven fusion was moderately increased by TMPRSS2 and strongly by ACE2, while SARS1-S-driven fusion was strongly increased by TMPRSS2 and less so by ACE2 expression. In contrast to that of SARS1-S, SARS2-S-mediated cell-cell fusion was efficiently activated by batimastat-sensitive metalloproteases. Mutation of the S1/S2 proteolytic cleavage site reduced effector cell-target cell fusion when ACE2 or TMPRSS2 was limiting and rendered SARS2-S-driven cell-cell fusion more dependent on TMPRSS2. When both ACE2 and TMPRSS2 were abundant, initial target cell-effector cell fusion was unaltered compared to that of wild-type (wt) SARS2-S, but syncytia remained smaller. Mutation of the S2 cleavage (S2') site specifically abrogated activation by TMPRSS2 for both cell-cell fusion and SARS2-S-driven pseudoparticle entry but still allowed for activation by metalloproteases for cell-cell fusion and by cathepsins for particle entry. Finally, we found that the TMPRSS2 inhibitor bromhexine, unlike the inhibitor camostat, was unable to reduce TMPRSS2-activated cell-cell fusion by SARS1-S and SARS2-S. Paradoxically, bromhexine enhanced cell-cell fusion in the presence of TMPRSS2, while its metabolite ambroxol exhibited inhibitory activity under some conditions. On Calu-3 lung cells, ambroxol weakly inhibited SARS2-S-driven lentiviral pseudoparticle entry, and both substances exhibited a dose-dependent trend toward weak inhibition of authentic SARS-CoV-2.IMPORTANCE Cell-cell fusion allows viruses to infect neighboring cells without the need to produce free virus and contributes to tissue damage by creating virus-infected syncytia. Our results demonstrate that the S2' cleavage site is essential for activation by TMPRSS2 and unravel important differences between SARS-CoV and SARS-CoV-2, among those, greater dependence of SARS-CoV-2 on ACE2 expression and activation by metalloproteases for cell-cell fusion. Bromhexine, reportedly an inhibitor of TMPRSS2, is currently being tested in clinical trials against coronavirus disease 2019. Our results indicate that bromhexine enhances fusion under some conditions. We therefore caution against the use of bromhexine in high dosages until its effects on SARS-CoV-2 spike activation are better understood. The related compound ambroxol, which similarly to bromhexine is clinically used as an expectorant, did not exhibit activating effects on cell-cell fusion. Both compounds exhibited weak inhibitory activity against SARS-CoV-2 infection at high concentrations, which might be clinically attainable for ambroxol.

Identification and Functional Characterization of a Novel Fc Gamma-Binding Glycoprotein in Rhesus Cytomegalovirus.

Receptors recognizing the Fc part of immunoglobulin G (FcγRs) are key determinants in antibody-mediated immune responses. Members of the Herpesviridae interfere with this immune regulatory network by expressing viral FcγRs (vFcγRs). Human cytomegalovirus (HCMV) encodes four distinct vFcγRs that differ with respect to their IgG subtype specificity and their impact on antibody-mediated immune function in vitro The impact of vFcγRs on HCMV pathogenesis and immunomodulation in vivo is not known. The closest evolutionary animal model of HCMV is rhesus CMV (RhCMV) infection of rhesus macaques. To enable the characterization of vFcγR function in this model, we studied IgG binding by RhCMV. We show that lysates of RhCMV-infected cells contain an IgG-binding protein of 30 kDa encoded by the gene Rh05 that is a predicted type I glycoprotein belonging to the RL11 gene family. Upon deletion of Rh05, IgG-Fc binding by RhCMV strain 68-1 is lost, whereas ectopic expression of Rh05 results in IgG binding to transfected cells consistent with Rh05 being a vFcγR. Using a set of reporter cell lines stably expressing human and rhesus FcγRs, we further demonstrate that Rh05 antagonizes host FcγR activation. Compared to Rh05-intact RhCMV, RhCMVΔRh05 showed an increased activation of host FcγR upon exposure of infected cells to IgG from RhCMV-seropositive animals, suggesting that Rh05 protects infected cells from opsonization and IgG-dependent activation of host FcγRs. However, antagonizing host FcγR activation by Rh05 was not required for the establishment and maintenance of infection of RhCMV, even in a seropositive host, as shown by the induction of T cell responses to heterologous antigens expressed by RhCMV lacking the gene region encoding Rh05. In contrast to viral evasion of natural killer cells or T cell recognition, the evasion of antibody-mediated effects does not seem to be absolutely required for infection or reinfection. The identification of the first vFcγR that efficiently antagonizes host FcγR activation in the RhCMV genome will thus permit more detailed studies of this immunomodulatory mechanism in promoting viral dissemination in the presence of natural or vaccine-induced humoral immunity.IMPORTANCE Rhesus cytomegalovirus (RhCMV) offers a unique model for studying human cytomegalovirus (HCMV) pathogenesis and vaccine development. RhCMV infection of nonhuman primates greatly broadened the understanding of mechanisms by which CMVs evade or reprogram T cell and natural killer cell responses in vivo However, the role of humoral immunity and viral modulation of anti-CMV antibodies has not been studied in this model. There is evidence from in vitro studies that HCMVs can evade humoral immunity. By gene mapping and with the help of a novel cell-based reporter assay system we characterized the first RhCMV encoded IgG-Fcγ binding glycoprotein as a potent antagonist of rhesus FcγR activation. We further demonstrate that, unlike evasion of T cell immunity, this viral Fcγ receptor is not required to overcome anti-CMV immunity to establish secondary infections. These findings enable more detailed studies of the in vivo consequences of CMV evasion from IgG responses in nonhuman primate models.

Vaccination of Macaques with DNA Followed by Adenoviral Vectors Encoding Simian Immunodeficiency Virus (SIV) Gag Alone Delays Infection by Repeated Mucosal Challenge with SIV.

Vaccines aimed at inducing T cell responses to protect against human immunodeficiency virus (HIV) infection have been under development for more than 15 years. Replication-defective adenovirus (rAd) vaccine vectors are at the forefront of this work and have been tested extensively in the simian immunodeficiency virus (SIV) challenge macaque model. Vaccination with rAd vectors coding for SIV Gag or other nonenvelope proteins induces T cell responses that control virus load but disappointingly is unsuccessful so far in preventing infection, and attention has turned to inducing antibodies to the envelope. However, here we report that Mauritian cynomolgus macaques (MCM), Macaca fascicularis, vaccinated with unmodified SIV gag alone in a DNA prime followed by an rAd boost exhibit increased protection from infection by repeated intrarectal challenge with low-dose SIVmac251. There was no evidence of infection followed by eradication. A significant correlation was observed between cytokine expression by CD4 T cells and delayed infection. Vaccination with gag fused to the ubiquitin gene or fragmented, designed to increase CD8 magnitude and breadth, did not confer resistance to challenge or enhance immunity. On infection, a significant reduction in peak virus load was observed in all vaccinated animals, including those vaccinated with modified gag These findings suggest that a nonpersistent viral vector vaccine coding for internal virus proteins may be able to protect against HIV type 1 (HIV-1) infection. The mechanisms are probably distinct from those of antibody-mediated virus neutralization or cytotoxic CD8 cell killing of virus-infected cells and may be mediated in part by CD4 T cells.IMPORTANCE The simian immunodeficiency virus (SIV) macaque model represents the best animal model for testing new human immunodeficiency virus type 1 (HIV-1) vaccines. Previous studies employing replication-defective adenovirus (rAd) vectors that transiently express SIV internal proteins induced T cell responses that controlled virus load but did not protect against virus challenge. However, we show for the first time that SIV gag delivered in a DNA prime followed by a boost with an rAd vector confers resistance to SIV intrarectal challenge. Other partially successful SIV/HIV-1 protective vaccines induce antibody to the envelope and neutralize the virus or mediate antibody-dependent cytotoxicity. Induction of CD8 T cells which do not prevent initial infection but eradicate infected cells before infection becomes established has also shown some success. In contrast, the vaccine described here mediates resistance by a different mechanism from that described above, which may reflect CD4 T cell activity. This could indicate an alternative approach for HIV-1 vaccine development.

The aging common marmoset's immune system: From junior to senior.

The social, health, and economic challenges of a steadily increasing aging population demand the use of appropriate translational animal models to address questions like healthy aging, vaccination strategies, or potential interventions during the aging process. Due to their genetic proximity to humans, especially nonhuman primates (NHPs) with a relatively short generation period compared to humans, qualify as excellent animal models for these purposes. The use of common marmosets (Callithrix jacchus) in gerontology research steadily increased over the last decades, yet important information about their aging parameters are still missing. We therefore aimed to characterize their aging immune system by comprehensive flow cytometric phenotyping of blood immune cells from juvenile, adult, aging, and geriatric animals. Aged and geriatric animals displayed clear signs of immunosenescence. A decline in CD4/CD8 ratio, increased expression of HLA-DR and PD-1, higher frequencies of CD95+ memory cells, alterations in cytokine secretion, and a decline in the proliferative capacity proved T cell senescence in aging marmosets. Also, the B cell compartment was affected by age-related changes: while overall B cell numbers remained stable with advancing age, expression of the activation marker CD80 increased and immunoglobulin M expression decreased. Interestingly, marmoset B cell memory subset distribution rather mirrored the human situation than that of other NHP. CD21+ CD27- naïve B cell frequencies decreased while those of CD21- CD27- tissue memory B cells increased with age. Furthermore, frequencies and numbers of NK cells as part of the innate immune system declined with advancing age. Thus, the observed immunological changes in common marmosets over their life span revealed several similarities to age-related changes in humans and encourages further studies to strengthen the common marmoset as a potential aging model.

Serological Analysis of Herpes B Virus at Individual Epitope Resolution: From Two-Dimensional Peptide Arrays to Multiplex Bead Flow Assays.

Macacine herpesvirus or B Virus (BV) is a zoonotic agent that leads to high mortality rates in humans if transmitted and untreated. Here, BV is used as a test case to establish a two-step procedure for developing high throughput serological assays based on synthetic peptides. In step 1, peptide microarray analysis of 42 monkey sera (30 of them tested BV positive by ELISA) revealed 1148 responses against 369 different peptides. The latter could be grouped into 142 different antibody target regions (ATRs) in six different glycoproteins (gB, gC, gD, gG, gH, and gL) of BV. The high number of newly detected ATRs was made possible inter alia by a new preanalytical protocol that reduced unspecific binding of serum components to the cellulose-based matrix of the microarray. In step 2, soluble peptides corresponding to eight ATRs of particularly high antigenicity were synthesized and coupled to fluorescently labeled beads, which were subsequently employed in immunochemical bead flow assays. Their outcome mirrored the ELISA results used as reference. Hence, convenient, fast, and economical screening of arbitrarily large macaque colonies for BV infection is now possible. The study demonstrates that a technology platform switch from two-dimensional high-resolution peptide arrays used for epitope discovery to a readily available bead array platform for serology applications is feasible.

Impairment of CCR6+ and CXCR3+ Th Cell Migration in HIV-1 Infection Is Rescued by Modulating Actin Polymerization.

CD4+ T cell repopulation of the gut is rarely achieved in HIV-1-infected individuals who are receiving clinically effective antiretroviral therapy. Alterations in the integrity of the mucosal barrier have been indicated as a cause for chronic immune activation and disease progression. In this study, we present evidence that persistent immune activation causes impairment of lymphocytes to respond to chemotactic stimuli, thus preventing their trafficking from the blood stream to peripheral organs. CCR6+ and CXCR3+ Th cells accumulate in the blood of aviremic HIV-1-infected patients on long-term antiretroviral therapy, and their frequency in the circulation positively correlates to levels of soluble CD14 in plasma, a marker of chronic immune activation. Th cells show an impaired response to chemotactic stimuli both in humans and in the pathogenic model of SIV infection, and this defect is due to hyperactivation of cofilin and inefficient actin polymerization. Taking advantage of a murine model of chronic immune activation, we demonstrate that cytoskeleton remodeling, induced by okadaic acid, restores lymphocyte migration in response to chemokines, both in vitro and in vivo. This study calls for novel pharmacological approaches in those pathological conditions characterized by persistent immune activation and loss of trafficking of T cell subsets to niches that sustain their maturation and activities.

Cell-Associated Simian Immunodeficiency Virus Accelerates Initial Virus Spread and CD4+ T-Cell Depletion in the Intestinal Mucosa.

Cell-free and cell-associated human immunodeficiency virus (HIV) may differently affect the immune system and the efficacy of prevention strategies. Here we examined mucosal events in simian immunodeficiency virus (SIV) infection, using infected cells together with cell-free virus and cell-free virus alone. Intravenously inoculated SIV-infected cells disseminated virus to the intestine within 16 hours. Infection with both virus forms accelerated viral dissemination in the intestinal mucosa and the loss of mucosal CD4+ T cells as compared to infection with cell-free virus only. As all natural sources of HIV infection contain both virus forms, future prevention studies should focus on efficacy against both cell-free and cell-associated virus.

Vector Order Determines Protection against Pathogenic Simian Immunodeficiency Virus Infection in a Triple-Component Vaccine by Balancing CD4+ and CD8+ T-Cell Responses.

An effective AIDS vaccine should elicit strong humoral and cellular immune responses while maintaining low levels of CD4+ T-cell activation to avoid the generation of target cells for viral infection. The present study investigated two prime-boost regimens, both starting vaccination with single-cycle immunodeficiency virus, followed by two mucosal boosts with either recombinant adenovirus (rAd) or fowlpox virus (rFWPV) expressing SIVmac239 or SIVmac251 gag/pol and env genes, respectively. Finally, vectors were switched and systemically administered to the reciprocal group of animals. Only mucosal rFWPV immunizations followed by systemic rAd boost significantly protected animals against a repeated low-dose intrarectal challenge with pathogenic SIVmac251, resulting in a vaccine efficacy (i.e., risk reduction per exposure) of 68%. Delayed viral acquisition was associated with higher levels of activated CD8+ T cells and Gag-specific gamma interferon (IFN-γ)-secreting CD8+ cells, low virus-specific CD4+ T-cell responses, and low Env antibody titers. In contrast, the systemic rFWPV boost induced strong virus-specific CD4+ T-cell activity. rAd and rFWPV also induced differential patterns of the innate immune responses, thereby possibly shaping the specific immunity. Plasma CXCL10 levels after final immunization correlated directly with virus-specific CD4+ T-cell responses and inversely with the number of exposures to infection. Also, the percentage of activated CD69+ CD8+ T cells correlated with the number of exposures to infection. Differential stimulation of the immune response likely provided the basis for the diverging levels of protection afforded by the vaccine regimen.IMPORTANCE A failed phase II AIDS vaccine trial led to the hypothesis that CD4+ T-cell activation can abrogate any potentially protective effects delivered by vaccination or promote acquisition of the virus because CD4+ T helper cells, required for an effective immune response, also represent the target cells for viral infection. We compared two vaccination protocols that elicited similar levels of Gag-specific immune responses in rhesus macaques. Only the animal group that had a low level of virus-specific CD4+ T cells in combination with high levels of activated CD8+ T cells was significantly protected from infection. Notably, protection was achieved despite the lack of appreciable Env antibody titers. Moreover, we show that both the vector and the route of immunization affected the level of CD4+ T-cell responses. Thus, mucosal immunization with FWPV-based vaccines should be considered a potent prime in prime-boost vaccination protocols.

Elevated granzyme B+ B-cell level in SIV-infection correlate with viral load and low CD4 T-cell count.

Granzyme B-expressing (GrB+) B cells are thought to contribute to immune dysfunctions in HIV patients, but so far their exact role is unknown. This report demonstrates for the first time the existence of GrB+ B cells in SIV-infected rhesus macaques, which represent the most commonly used nonhuman primate model for HIV research. Similar to HIV patients, we found significantly higher frequencies of these cells in the blood of chronically SIV-infected rhesus monkeys compared with uninfected healthy ones. These frequencies correlated with plasma viral load and inversely with absolute CD4 T-cell counts. When investigating GrB+ B cells in different compartments, levels were highest in blood, spleen and bone marrow, but considerably lower in lymph nodes and tonsils. Analysis of expression of various surface markers on this particular B-cell subset in SIV-infected macaques revealed differences between the phenotype in macaques and in humans. GrB+ B cells in SIV-infected rhesus macaques exhibit an elevated expression of CD5, CD10, CD25 and CD27, while expression of CD19, CD185 and HLA-DR is reduced. In contrast to human GrB+ B cells, we did not observe a significantly increased expression of CD43 and CD86. B-cell receptor stimulation in combination with IL-21 of purified B cells from healthy animals led to the induction of GrB expression. Furthermore, initial functional analyses indicated a regulatory role on T-cell proliferation. Overall, our data pave the way for longitudinal analyses including studies on the functionality of GrB+ B cells in the nonhuman primate model for AIDS.

Long-term efficient control of SIV infection in macaques is associated with an intact intestinal barrier.

Hallmarks of SIV infection are early depletion of gut CD4 T cells and diminished intestinal integrity. Comprehensive studies on colon biopsies of SIV-infected macaques efficiently controlling infection revealed that in contrast to viremic and failing controllers, elite controllers show preserved CD4 T cells, and low viral load, apoptosis, and inflammation.

Pre-infection transcript levels of FAM26F in peripheral blood mononuclear cells inform about overall plasma viral load in acute and post-acute phase after simian immunodeficiency virus infection.

CD8+ cells from simian immunodeficiency virus (SIV)-infected long-term non-progressors and some uninfected macaques can suppress viral replication in vitro without killing the infected cells. The aim of this study was to identify factors responsible for non-cytolytic viral suppression by transcriptional profiling and to investigate their potential impact on SIV replication. Results of microarray experiments and further validation with cells from infected and uninfected macaques revealed that FAM26F RNA levels distinguished CD8+ cells of controllers and non-controllers (P=0.001). However, FAM26F was also expressed in CD4+ T-cells and B-cells. FAM26F expression increased in lymphocytes after in vitro IFN-γ treatment on average 40-fold, and ex vivo FAM26F RNA levels in peripheral blood mononuclear cells correlated with plasma IFN-γ but not with IFN-α. Baseline FAM26F expression appeared to be stable for months, albeit the individual expression levels varied up to tenfold. Investigating its role in SIV-infection revealed that FAM26F was upregulated after infection (P<0.0008), but did not directly correlate with viral load in contrast to MX1 and CXCL10. However, pre-infection levels of FAM26F correlated inversely with overall plasma viral load (AUC) during the acute and post-acute phases of infection (e.g. AUC weeks post infection 0-8; no AIDS vaccine: P<0.0001, Spearman rank correlation coefficient (rs)=-0.89, n=16; immunized with an AIDS vaccine: P=0.033, rs=-0.43; n=25). FAM26F transcript levels prior to infection can provide information about the pace and strength of the antiviral immune response during the early stage of infection. FAM26F expression represented, in our experiments, one of the earliest prognostic markers, and could supplement major histocompatibility complex (MHC)-typing to predict disease progression before SIV-infection.

Exclusive Decoration of Simian Immunodeficiency Virus Env with High-Mannose Type N-Glycans Is Not Compatible with Mucosal Transmission in Rhesus Macaques.

Human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) envelope (Env) proteins are extensively decorated with N-glycans, predominantly of the high-mannose type. However, it is unclear how high-mannose N-glycans on Env impact viral spread. We show that exclusive modification of SIV Env with these N-glycans reduces viral infectivity and abrogates mucosal transmission, despite increasing viral capture by immune cell lectins. Thus, high-mannose N-glycans have opposed effects on SIV infectivity and lectin reactivity, and a balance might be required for efficient mucosal transmission.

Comprehensive panel of cross-reacting monoclonal antibodies for analysis of different immune cells and their distribution in the common marmoset (Callithrix jacchus).

BACKGROUND: Common marmosets are extensively used in immunological and pharmacological research, and the usage of methods such as flow cytometry gain increasing importance. METHODS: Using multicolor flow cytometry cross-reactivity of monoclonal antibodies with cells of common marmosets was analyzed. Furthermore, frequencies of immune cells and immunological parameters were assessed in healthy common marmosets. RESULTS: A total of 97 clones of monoclonal antibodies raised against CD markers, chemokine receptors, and miscellaneous markers were tested. Additionally, baseline frequencies of different innate and adaptive immune cells as well as certain parameters, such as activation and memory T-cell and B-cell distribution, are provided. CONCLUSION: Our study gives an extended overview of cross-reactive antibodies for flow cytometric analysis of immune cells as well as baseline values for different immune parameters in healthy common marmosets.

Novel vaccine regimen elicits strong airway immune responses and control of respiratory syncytial virus in nonhuman primates.

UNLABELLED: Induction of long-lasting immunity against viral respiratory tract infections remains an elusive goal. Using a nonhuman primate model of human respiratory syncytial virus (hRSV) infection, we compared mucosal and systemic immune responses induced by different DNA delivery approaches to a novel parenteral DNA prime-tonsillar adenoviral vector booster immunization regimen. Intramuscular (i.m.) electroporation (EP) of a DNA vaccine encoding the fusion protein of hRSV induced stronger systemic immune responses than intradermal EP, tattoo immunization, and conventional i.m. DNA injection. A single EP i.m., followed by two atraumatic tonsillar immunizations with the adenoviral vector, elicited strong systemic immune responses, an unique persistent CD4(+) and CD8(+) T cell response in the lower respiratory tract and protection from intranasal hRSV challenge. Thus, parenteral DNA priming followed by booster immunization targeted to a mucosal inductive site constitutes an effective vaccine regimen for eliciting protective immune responses at mucosal effector sites. IMPORTANCE: The human respiratory syncytial virus (hRSV) is the most common cause of severe respiratory tract disease in infancy and leads to substantial morbidity and morality in the elderly. In this study, we compared the immunogenicity and efficacy of several gene-based immunization protocols in rhesus macaques. Thereby, we found that the combination of an initially parenterally delivered DNA vaccine with a subsequent atraumatic tonsillar adenoviral vector immunization results in a strong systemic immune response accompanied by an exceptional high T-cell response in the mucosa. Strikingly, these animals were protected against a RSV challenge infection controlling the viral replication indicated by a 1,000-fold-lower viral load in the lower respiratory tract. Since mucosal cellular responses of this strength had not been described in earlier RSV vaccine studies, this heterologous DNA prime-tonsillar boost vaccine strategy is very promising and should be pursued for further preclinical and clinical testing.

Frequencies of lymphoid T-follicular helper cells obtained longitudinally by lymph node fine-needle aspiration correlate significantly with viral load in SIV-infected rhesus monkeys.

BACKGROUND: T-follicular helper (T(FH)) cells are an important population in lymph nodes (LNs) contributing to the generation of highly specific B cells. For SIV studies in rhesus macaques (RM), analysis of LN is necessary, but restricted due to invasive sampling. We applied the minimally invasive LN fine-needle aspiration (LN-FNA) and examined dynamics of T(FH) cells during SIV infection. MATERIALS AND METHODS: LN-FNA and LN resection were carried out on uninfected RM. Lymphocytes were analyzed by flow cytometry. Additionally, cells obtained by LN-FNA over time from SIV-infected RM were analyzed. RESULTS: Percentages of lymphocyte subsets were similar in LN aspirates and whole LNs. Analysis of LN aspirates from SIV-infected RM demonstrated a decrease of CD4(+) T cells, while T(FH) cell frequencies increased over time and correlated significantly with plasma viral load. CONCLUSIONS: By applying LN-FNA, we showed that T(FH) cell expansion in chronic SIV infection is associated with viral load.

Evaluating noninvasive markers of nonhuman primate immune activation and inflammation.

OBJECTIVES: Health, disease, and immune function are key areas of research in studies of ecology and evolution, but work on free-ranging primates has been inhibited by a lack of direct noninvasive measures of condition. Here, we evaluate the potential usefulness of noninvasive measurement of three biomarkers, the acute-phase proteins C-reactive protein (CRP) and haptoglobin, and neopterin, a by-product of macrophage activity. MATERIALS AND METHODS: We took advantage of veterinary checks on captive rhesus (24) and long-tailed (3) macaques at the German Primate Center (DPZ) to analyze serum marker measures, before measuring concentrations in feces and urine, and evaluating relationships between matched serum, urine, and fecal concentrations. In a second study, we monitored excretion of these markers in response to simian immunodeficiency virus (SIV) infection and surgical tissue trauma, undertaken for a separate study. RESULTS: We found that each biomarker could be measured in each matrix. Serum and urinary concentrations of neopterin were strongly and significantly correlated, but neither haptoglobin nor CRP concentrations in excreta proxied circulating serum concentrations. Our infection study confirmed that urinary neopterin, in particular, is a reliable marker of viral infection in macaques, but also indicated the potential of urinary and fecal CRP and haptoglobin as indicators of inflammation. DISCUSSION: We highlight the potential of noninvasive markers of immune function, especially of urinary neopterin, which correlates strongly with serum neopterin, and is highly responsive to infection.

Host factors determine differential disease progression after infection with nef-deleted simian immunodeficiency virus.

Infection of macaques with live attenuated simian immunodeficiency virus (SIV) usually results in long-lasting efficient protection against infection with pathogenic immunodeficiency viruses. However, attenuation by deletion of regulatory genes such as nef is not complete, leading to a high viral load and fatal disease in some animals. To characterize immunological parameters and polymorphic host factors, we studied 17 rhesus macaques infected with attenuated SIVmac239ΔNU. Eight animals were able to control viral replication, whereas the remaining animals (non-controllers) displayed variable set-point viral loads. Peak viral load at 2 weeks post-infection (p.i.) correlated significantly with set-point viral load (P<0.0001). CD4(+) T-cell frequencies differed significantly soon after infection between controllers and non-controllers. Abnormal B-cell activation previously ascribed to Nef function could already be observed in non-controllers 8 weeks after infection despite the absence of Nef. Two non-controllers developed an AIDS-like disease within 102 weeks p.i. Virus from these animals transmitted to naïve animals replicated at low levels and the recipients did not develop immunodeficiency. This suggested that host factors determined differential viral load and subsequent disease course. Known Mhc class I alleles associated with disease progression in SIV WT infection only marginally influenced the viral load in Δnef-infected animals. Protection from SIVmac251 was associated with homozygosity for MHC class II in conjunction with a TLR7 polymorphism and showed a trend with initial viral replication. We speculated that host factors whose effects were usually masked by Nef were responsible for the different disease courses in individual animals upon infection with nef-deleted viruses.