Intestinal intraepithelial lymphocytes are primed for gamma interferon and MIP-1beta expression and display antiviral cytotoxic activity despite severe CD4(+) T-cell depletion in primary simian immunodeficiency virus infection

Immuno-modulatory Effects of Inactivated Dietzia Maris on the Selected Aspects of Cellular and Humoral Immune Responses in Mice

Background

The current study is an attempt to register the alterations in the immunological and histological parameters in mice arising from the administration of Dietza maris (D. maris) in order to confirm its protective properties.

Materials and Methods

Mice underwent 7 days of treatment with three doses of D. maris. Then, animals were scrutinized in terms of body weight, relative weight of organs, delayed type of hypersensitivity (DTH) response, and hemagglutination titer (HT). The determination of villus height, villus width, crypt depth, villus/crypt ratio (V/C), Goblet cells, and intestinal epithelial lymphocyte (IEL) density in villi was carried out.

Results

A boosted DTH response was observed as a result of bacteria at medium dose. A variation was noted between the hemagglutinin titer of the control group and that of the high-dose group. Crypt depth, villus width, and villus height manifested alterations. High-dose-treated mice demonstrated proliferation of Goblet cells in the villi, whereas both in medium- and high-dose-treated mice, a distribution of IELs in the villus epithelium was noted. Overall, D. maris showed a stimulatory effect on immune functions in mice. Thus, thanks to improved cellular and humoral immunity and the increased quality of intestine function, we believe that D. maris promises novel therapeutic applications in the future.

Conclusion

The attained findings lend credence to immuno-stimulatory effects arising from the capacity of D. maris to function as immunological adjuvants and to enhance humoral and cellular immunity as well as the intestinal structure and function.

Dietary pattern association with CD4 cells count in patients living with human immunodeficiency virus: A cross-sectional study

Background

Considering contradictory reports about the impact of dietary pattern on CD4 cell count in previous studies and the potential importance of diet on the immune system, this study aimed to assess the association between dietary patterns and CD4 count among HIV-infected patients.

Methods

This cross-sectional study was conducted among HIV-infected patients aged 18-60 who registered in the referral Voluntary Counseling and Testing Center of Shiraz, Iran. The principal component analysis identified nutritional patterns and factors. The association between the score of the dietary patterns and CD4 count was considered in two categories of CD4 more/less than 500 and using backward logistic regression after adjusting for confounders.

Results

A total of 226 participants were included in the analysis. CD4 was significantly lower in males (p < 0.001). Participants with illegal drug use (p < 0.001), HCV (p = 0.001), and HBV (p < 0.001) had lower serum CD4. Four extracted dietary patterns were a Plant-rich diet, Healthy animal-based proteins, a Western diet, and Affordable calorie and protein patterns. There was an association between CD4 and Western diet patterns in the best model in which age, gender, weight, and HBV were included. Each unit increase in Western diet score increased the odds of CD4 less than 500 by 57% (OR = 1.57; CI 95% 1.06-2.34, p = 0.02).

Conclusion

Among the four dietary patterns, the Western diet comprising a high intake of refined sugar and grain, saturated and trans fats, and animal protein sources, especially high-fat red meat, had a statistically significant relationship with a decrease in CD4 cell count.

Supplementation of Alhagi honey polysaccharides contributes to the improvement of the intestinal immunity regulating the structure of intestinal flora in mice

Alhagi honey polysaccharides (AH), a main active component of Alhagi honey, are known to possess excellent pharmacological activities and have been widely used as dietary supplements in traditional Chinese medicine for thousands of years. This study is aimed to investigate the heath effect of AH on murine intestinal mucosal immune function and composition of the gut microbiome. ICR mice received daily intragastric administration of AH (three dosages, 200 mg kg^-1, 400 mg kg^-1, and 800 mg kg^-1) or saline for 7 consecutive days. Results indicated an improvement in the intestinal barrier function through increases in secretory immunoglobulin A (sIgA) and β-defensins. Simultaneously, AH also significantly stimulated IL-2, IL-4, IL-6, IL-10, IL-17, IFN-γ, and TNF-α cytokine secretion as compared to the control samples. Moreover, hematoxylin and eosin staining showed that AH enhanced the number of intraepithelial lymphocytes (IELs) in the small intestine. An obvious increase in the ratio of IgA⁺ cells of AH-treatment samples in the lamina propria was also detected by immunohistochemical staining. In addition, the CD3⁺, CD4⁺ and CD8⁺ T-cell ratio in mesenteric lymph nodes and Peyer's patches in the AH-treatment was significantly higher than that in the control group. Furthermore, 16S rDNA gene sequencing was used to monitor the dynamic changes in the gut microbiota. The result revealed that AH significantly increased the indexes of Shannon and obviously decreased the indexes of Simpson, suggesting the enhancement of the diversity and richness of the intestinal microbiome. Moreover, AH modulated the gut microbiome via increasing the abundance of probiotics and decreasing the levels of pathogenic bacteria. In summary, these results indicated that AH could be used as a prebiotic to enhance murine intestinal mucosal immunity and to modulate the gut microbiome.

GALT CD4+PD-1hi T follicular helper (Tfh) cells repopulate after anti-retroviral therapy

Human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infections are characterized by dramatic alterations in the mucosal CD4 T cell compartment. Though viremia is effectively suppressed, and peripheral CD4 T cell numbers recover to near healthy levels after highly active anti-retroviral therapy (HAART), some of the dysfunctional consequences of HIV infection continue to persist during therapy. We hypothesized that CD4 T follicular helper (Tfh) cell deficiencies may play a role in this process. Using the macaque model we show that SIV infection was associated with a significant loss of Tfh cells in the GALT that drain the mesentery lining the gastrointestinal tract (GIT). Loss of Tfh cells significantly correlated with the depletion of the overall memory CD4 T cell compartment; most Tfh cells in the GALT expressed a CD95+CD28+ memory phenotype suggesting that infection of the memory compartment likely drives the loss of GALT Tfh cells during infection. Continuous anti-retroviral therapy (cART) was accompanied by a significant repopulation of Tfh cells in the GALT to levels similar to those of uninfected animals. Repopulating Tfh cells displayed significantly higher capacity to produce IL-21 as compared to SIV infected animals suggesting that cART fully restores Tfh cells that are functionally capable of supporting GC reactions in the GALT.

Gut Microbiome Homeostasis and the CD4 T- Follicular Helper Cell IgA Axis in Human Immunodeficiency Virus Infection

Human Immunodeficiency Virus (HIV) and Simian Immunodeficiency Virus (SIV) are associated with severe perturbations in the gut mucosal environment characterized by massive viral replication and depletion of CD4 T cells leading to dysbiosis, breakdown of the epithelial barrier, microbial translocation, immune activation and disease progression. Multiple mechanisms play a role in maintaining homeostasis in the gut mucosa and protecting the integrity of the epithelial barrier. Among these are the secretory IgA (sIgA) that are produced daily in vast quantities throughout the mucosa and play a pivotal role in preventing commensal microbes from breaching the epithelial barrier. These microbe specific, high affinity IgA are produced by IgA+ plasma cells that are present within the Peyer’s Patches, mesenteric lymph nodes and the isolated lymphoid follicles that are prevalent in the lamina propria of the gastrointestinal tract (GIT). Differentiation, maturation and class switching to IgA producing plasma cells requires help from T follicular helper (Tfh) cells that are present within these lymphoid tissues. HIV replication and CD4 T cell depletion is accompanied by severe dysregulation of Tfh cell responses that compromises the generation of mucosal IgA that in turn alters barrier integrity leading to commensal bacteria readily breaching the epithelial barrier and causing mucosal pathology. Here we review the effect of HIV infection on Tfh cells and mucosal IgA responses in the GIT and the consequences these have for gut dysbiosis and mucosal immunopathogenesis.

The Hitchhiker Guide to CD4+ T-Cell Depletion in Lentiviral Infection. A Critical Review of the Dynamics of the CD4+ T Cells in SIV and HIV Infection

CD4⁺ T-cell depletion is pathognomonic for AIDS in both HIV and simian immunodeficiency virus (SIV) infections. It occurs early, is massive at mucosal sites, and is not entirely reverted by antiretroviral therapy (ART), particularly if initiated when T-cell functions are compromised. HIV/SIV infect and kill activated CCR5-expressing memory and effector CD4⁺ T-cells from the intestinal lamina propria. Acute CD4⁺ T-cell depletion is substantial in progressive, nonprogressive and controlled infections. Clinical outcome is predicted by the mucosal CD4⁺ T-cell recovery during chronic infection, with no recovery occurring in rapid progressors, and partial, transient recovery, the degree of which depends on the virus control, in normal and long-term progressors. The nonprogressive infection of African nonhuman primate SIV hosts is characterized by partial mucosal CD4⁺ T-cell restoration, despite high viral replication. Complete, albeit very slow, recovery of mucosal CD4+ T-cells occurs in controllers. Early ART does not prevent acute mucosal CD4⁺ T-cell depletion, yet it greatly improves their restoration, sometimes to preinfection levels. Comparative studies of the different models of SIV infection support a critical role of immune activation/inflammation (IA/INFL), in addition to viral replication, in CD4⁺ T-cell depletion, with immune restoration occurring only when these parameters are kept at bay. CD4⁺ T-cell depletion is persistent, and the recovery is very slow, even when both the virus and IA/INFL are completely controlled. Nevertheless, partial mucosal CD4⁺ T-cell recovery is sufficient for a healthy life in natural hosts. Cell death and loss of CD4⁺ T-cell subsets critical for gut health contribute to mucosal inflammation and enteropathy, which weaken the mucosal barrier, leading to microbial translocation, a major driver of IA/INFL. In turn, IA/INFL trigger CD4⁺ T-cells to become either viral targets or apoptotic, fueling their loss. CD4⁺ T-cell depletion also drives opportunistic infections, cancers, and comorbidities. It is thus critical to preserve CD4⁺ T cells (through early ART) during HIV/SIV infection. Even in early-treated subjects, residual IA/INFL can persist, preventing/delaying CD4⁺ T-cell restoration. New therapeutic strategies limiting mucosal pathology, microbial translocation and IA/INFL, to improve CD4⁺ T-cell recovery and the overall HIV prognosis are needed, and SIV models are extensively used to this goal.

Microbial Dysbiosis During Simian Immunodeficiency Virus Infection is Partially Reverted with Combination Anti-retroviral Therapy

Human immunodeficiency virus (HIV) infection is characterized by a massive loss of CD4 T cells in the gastrointestinal tract (GIT) that is accompanied by changes in the gut microbiome and microbial translocation that contribute to inflammation and chronic immune activation. Though highly active antiretroviral therapy (HAART) has led to better long-term outcomes in HIV infected patients, it has not been as effective at reverting pathogenesis in the GIT. Using the simian immunodeficiency virus (SIV) infection model, we show that combination antiretroviral therapy (c-ART) partially reverted microbial dysbiosis observed during SIV infection. Though the relative abundance of bacteria, their richness or diversity did not significantly differ between infected and treated animals, microbial dysbiosis was evident via multiple beta diversity metrics: Jaccard similarity coefficient, Bray-Curtis similarity coefficient, and Yue & Clayton theta similarity coefficient. Principal coordinates analysis (PCoA) clustered SIV-infected untreated animals away from healthy and treated animals that were clustered closely, indicating that c-ART partially reversed the gut dysbiosis associated with SIV infection. Metastats analysis identified specific operational taxonomic units (OTUs) falling within the Streptococcus, Prevotella, Acinetobacter, Treponema, and Lactobacillus genera that were differentially represented across the three groups. Our results suggest that complete viral suppression with c-ART could potentially revert microbial dysbiosis observed during SIV and HIV infections.

Gender differences in innate responses and gene expression profiles in memory CD4 T cells are apparent very early during acute simian immunodeficiency virus infection

Gender differences in Human immunodeficiency virus (HIV) disease progression and comorbidities have been extensively reported. Using the simian immunodeficiency virus (SIV) infected rhesus macaque model, we show that these differences are apparent very early during the course of infection. Though there were no major changes in the proportions of CD4 T cells or its subsets, central memory CD4 T cells from female macaques were found to differentially regulate a significantly larger number of genes at day 4 post-infection (PI) as compared to males. Pathway analysis revealed divergence of both canonical and biological pathways that persisted at day 10 PI. Changes in gene expression profiles were accompanied by a significant increase in plasma levels of pro-inflammatory mediators such as MCP-1/CCL2, I-TAC/CXCL11, and MIF. Though plasma levels of IFNα did not differ between male and female macaques, the expression levels of IFNα subtype-14, 16, IFNβ, and IFNω were significantly upregulated in the lymph nodes of female macaques at day 10 PI as compared to male macaques. Our results suggest that the pathogenic sequelae seen during chronic infection may be shaped by gender differences in immune responses induced very early during the course of HIV infection.

Mucosal T follicular helper cells in SIV-infected rhesus macaques: contributing role of IL-27

Mesenteric lymph nodes (MLNs), that drain the large and small intestine, are critical sites for the induction of oral tolerance. Although depletion of CD4 T cells in the intestinal lamina propria is a hallmark of HIV infection, CD4 T cell dynamics in MLNs is less known due to the lack of accessibility to these LNs. We demonstrate the early loss of memory CD4 T cells, including T follicular helper cells (Tfh) and a remodeling of MLN architecture in SIV-infected rhesus macaques (RMs). Along with the loss of Tfh cells, we observe the loss of memory B cells and of germinal center B cells. Tfh cells display a Th1 profile with increased levels of the transcription factors that negatively impact on Tfh differentiation and of Stat5 phosphorylation. MLNs of SIV-infected RMs display lower mRNA transcripts encoding for IL-12, IL-23, and IL-35, whereas those coding for IL-27 are not impaired in MLNs. In vitro, IL-27 negatively impacts on Tfh cells and recapitulates the profile observed in SIV-infected RMs. Therefore, early defects of memory CD4 T cells, as well of Tfh cells in MLNs, which play a central role in regulating the mucosal immune response, may have major implications for Aids.

Probiotic supplementation promotes a reduction in T-cell activation, an increase in Th17 frequencies, and a recovery of intestinal epithelium integrity and mitochondrial morphology in ART-treated HIV-1-positive patients

INTRODUCTION

HIV infection is characterized by a persistent immune activation associated to a compromised gut barrier immunity and alterations in the profile of the fecal flora linked with the progression of inflammatory symptoms. The effects of high concentration multistrain probiotic (Vivomixx®, Viale del Policlinico 155, Rome, Italy in EU; Visbiome®, Dupont, Madison, Wisconsin in USA) on several aspects of intestinal immunity in ART-experienced HIV-1 patients was evaluated.

METHODS

A sub-study of a longitudinal pilot study was performed in HIV-1 patients who received the probiotic supplement twice a day for 6 months (T6). T-cell activation and CD4+ and CD8+ T-cell subsets expressing IFNγ (Th1, Tc1) or IL-17A (Th17, Tc17) were stained by cytoflorimetric analysis. Histological and immunohistochemical analyses were performed on intestinal biopsies while enterocytes apoptosis index was determined by TUNEL assay.

RESULTS

A reduction in the frequencies of CD4+ and CD8+ T-cell subsets, expressing CD38+ , HLA-DR+ , or both, and an increase in the percentage of Th17 cell subsets, especially those with central or effector memory phenotype, was recorded in the peripheral blood and in gut-associated lymphoid tissue (GALT) after probiotic intervention. Conversely, Tc1 and Tc17 levels remained substantially unchanged at T6, while Th1 cell subsets increase in the GALT. Probiotic supplementation was also associated to a recovery of the integrity of the gut epithelial barrier, a reduction of both intraepithelial lymphocytes density and enterocyte apoptosis and, an improvement of mitochondrial morphology sustained in part by a modulation of heat shock protein 60.

CONCLUSIONS

These findings highlight the potential beneficial effects of probiotic supplementation for the reconstitution of physical and immunological integrity of the mucosal intestinal barrier in ART-treated HIV-1-positive patients.

Distribution and Activation of CD8+ T Cells in the Duodenal Mucosa before and after HIV Seroconversion

CD8⁺ T cells in the intestinal mucosa influence the HIV-associated pathogenesis, but little is known about the dynamics of mucosal CD8⁺ T cell counts and activation of these cells during the course of infection. In this study, mucosal CD8⁺ T cells in the duodenum were studied at different stages of HIV infection, starting from the seronegative phase. In seronegative acute HIV infection, CD8⁺ T cell counts increased in the epithelium, but not in the lamina propria. Infiltration of the lamina propria by peripherally expanded CD8⁺ T cells was observed after seroconversion. Highest increase in the expression of perforin, the rate-limiting molecule for cytotoxic CD8⁺ T cell activity, was evident in the lamina propria of seronegative acutely HIV-infected patients. The number of perforin-expressing cells in the lamina propria of acutely HIV-infected patients was positively associated with biomarkers of enterocyte damage and microbial translocation. After seroconversion, perforin expression was downregulated in the lamina propria, but not in the epithelium. In conclusion, our findings demonstrate that intraepithelial and lamina propria CD8⁺ T cells exhibit different dynamics of numerical alteration and cytotoxic activity in HIV-infected patients. Moreover, our results suggest that perforin-dependent cytotoxic mechanisms by CD8⁺ T cells could impair the intestinal mucosal barrier already in the seronegative phase of acute HIV infection, thereby inducing microbial translocation as one of the earliest pathological events in HIV infection.

HIV-1 and hijacking of the host immune system: the current scenario

Human immunodeficiency virus (HIV) infection is a major health burden across the world which leads to the development of acquired immune deficiency syndrome (AIDS). This review article discusses the prevalence of HIV, its major routes of transmission, natural immunity, and evasion from the host immune system. HIV is mostly prevalent in Sub-Saharan Africa and low income countries. It is mostly transmitted by sharing syringe needles, blood transfusion, and sexual routes. The host immune system is categorized into three main types; the innate, the adaptive, and the intrinsic immune system. Regarding the innate immune system against HIV, the key players are mucosal membrane, dendritic cells (DCs), complement system, interferon, and host Micro RNAs. The major components of the adaptive immune system exploited by HIV are T cells mainly CD4+ T cells and B cells. The intrinsic immune system confronted by HIV involves (apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G) APOBEC3G, tripartite motif 5-α (TRIM5a), terherin, and (SAM-domain HD-domain containing protein) SAMHD1. HIV-1 efficiently interacts with the host immune system, exploits the host machinery, successfully replicates and transmits from one cell to another. Further research is required to explore evasion strategies of HIV to develop novel therapeutic approaches against HIV.

Small intestinal injury in mice infected with respiratory influenza A virus: evidence for virus induced gastroenteritis

OBJECTIVES

Influenza in humans is often accompanied by gastroenteritis-like symptoms such as diarrhea and abdominal pain nausea, but the underlying mechanism remains unclear.

RESULTS

Mice infected with three subtypes of respiratory influenza A virus (IAV), particularly H5N1 and H7N2, developed intestinal injury. The avian H5N1 and H7N2 IAV were detected in the small intestine, whereas the human H1N1 was not detected. Section staining with the sialic acid (SA) receptor demonstrated that the small intestine mainly expressed SA α2, 3 Gal instead of SA α2, 6 Gal which preferentially binds to avian IAV. The number of goblet and sIgA cells in the small intestine increased, whereas CD4(+) and CD8(+) T cells decreased in all infected mice except for CD8(+) T cells increased in H7N2 infected mice.

CONCLUSIONS

Respiratory IAV infection, particularly infected by avian IAV, can cause small intestine structural damage and modify the local immune response, thereby resulting in gastroenteritis-like symptoms.

Current understanding of HIV-1 and T-cell adaptive immunity: progress to date

The cellular immune response to human immunodeficiency virus (HIV) has different components originating from both the adaptive and innate immune systems. HIV cleverly utilizes the host machinery to survive by its intricate nature of interaction with the host immune system. HIV evades the host immune system at innate ad adaptive, allows the pathogen to replicate and transmit from one host to another. Researchers have shown that HIV has multipronged effects especially on the adaptive immunity, with CD4(+) cells being the worst effect T-cell populations. Various analyses have revealed that, the exposure to HIV results in clonal expansion and excessive activation of the immune system. Also, an abnormal process of differentiation has been observed suggestive of an alteration and blocks in the maturation of various T-cell subsets. Additionally, HIV has shown to accelerate immunosenescence and exhaustion of the overtly activated T-cells. Apart from causing phenotypic changes, HIV has adverse effects on the functional aspect of the immune system, with evidences implicating it in the loss of the capacity of T-cells to secrete various antiviral cytokines and chemokines. However, there continues to be many aspects of the immune- pathogenesis of HIV that are still unknown and thus required further research in order to convert the malaise of HIV into a manageable epidemic.

Comparison of viral burden and disease progression in Chinese-origin rhesus macaques infected with common experimentally applied chimeric virus: SHIV-1157ipd3N4, SHIV-162P3, or SHIV-KB9

BACKGROUND

Little is known about the comparative susceptibility and differential pathogenic characteristics of Chinese-origin rhesus macaques upon infection with the chimeric SHIVs most commonly applied in experimental research.

METHODS

In vivo infectivity, viral replication, and disease progression related to SHIV-1157ipd3N4, SHIV-162P3, and SHIV-KB9 infections were assessed after intravenous inoculation of Chinese-origin rhesus macaques (n = 10 each).

RESULTS

SHIV-KB9-infected monkeys had higher plasma viral loads than those infected with SHIV-1157ipd3N4 or SHIV-162P3 (P < 0.05). The SHIV-KB9 group had a member that progressed rapidly to simian acquired immunodeficiency syndrome and was moribund at 155 days post-inoculation. SHIV-KB9 and SHIV-162P3 showed reverse trends in the effects on levels of memory T-cell subpopulations.

CONCLUSIONS

This study provides foundational data for future efficacy testing of candidate vaccine and antiviral therapy using a Chinese-origin rhesus macaque system.

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.

Effects of epimedium polysaccharide-propolis flavone oral liquid on mucosal immunity in chickens

A previous study found that epimedium polysaccharide (EP)-propolis flavonoid (PF) injection (EPI) produced reliable immunoenhancement. In this study, we investigate the effects of EP-PF oral liquid (EFO) on mucosal immunity in the chicken small intestine while using EPI, EP and PF as controls. Groups of fourteen-day-old chickens were given EFO orally at one of the three doses when they were vaccinated with ND vaccine. On days 7, 21 and 35 after the first vaccination, six chickens were selected randomly from each group for measurements of the sIgA and IL-17 contents of the washing liquors of the duodenum and jejunum, counts of the lymphocytes in the duodenal endothelium and counts of the IgA(+) cells in the jejunal endothelium and cecum tonsil. The results indicated that EFO significantly promoted the secretion of sIgA and IL-17 and increased the numbers of lymphocyte and IgA(+) cells. Furthermore, EFO was more efficient than EPI at the high and medium doses. These findings indicate that EPO may enhance intestinal mucosal immunity and may be exploited as an oral immunopotentiator.

Repressive effect of primary virus replication on superinfection correlated with gut-derived central memory CD4(+) T cells in SHIV-infected Chinese rhesus macaques

A possible mechanism of susceptibility to superinfection with simian-human immunodeficiency virus (SHIV)-1157ipd3N4 was explored in twelve SHIV_SF162P3-infected Chinese rhesus macaques. Based on the kinetics of viral replication for the second infecting virus following SHIV-1157ipd3N4 inoculation, the monkeys were divided into two groups: those relatively resistant to superinfection (SIR) and those relatively sensitive to superinfection (SIS). We found that superinfection-resistant macaques had high primary viremia, whereas superinfection-sensitive macaques had low primary viremia, suggesting that primary SHIV_SF162P3 infection with a high viral-replication level would repress superinfection with a heterologous SHIV-1157ipd3N4. Although no correlation of protection against superinfection with virus-specific CD4⁺ T cell or CD8⁺ T cell immune responses from gut was observed prior to superinfection, superinfection susceptibility was strongly correlated with CD4⁺ Tcm cells from gut both prior to the second infecting virus inoculation and on day 7 after superinfection, but not with CD4⁺ Tem cells from gut or with CD4⁺ Tcm cells from peripheral blood and lymph node. These results point to the important roles of gut-derived CD4⁺ Tcm cells for the study of the mechanisms of protection against superinfection and the evaluation of the safety and efficacy of vaccines and therapies against acquired immune deficiency syndrome (AIDS).

Breast milk cellular HIV-specific interferon γ responses are associated with protection from peripartum HIV transmission

OBJECTIVE

Breast milk is a major route of infant HIV infection, yet the majority of breast-fed, HIV-exposed infants escape infection by unknown mechanisms. This study aimed to investigate the role of HIV-specific breast milk cells in preventing infant HIV infection.

DESIGN

A prospective study was designed to measure associations between maternal breast milk HIV-specific interferon-γ (IFN-γ) responses and infant HIV-1 detection at 1 month of age.

METHODS

In a Kenyan cohort of HIV-infected mothers, blood and breast milk HIV-gag IFN-γ ELISpot responses were measured. Logistic regression was used to measure associations between breast milk IFN-γ responses and infant HIV infection at 1 month of age.

RESULTS

IFN-γ responses were detected in breast milk from 117 of 170 (69%) women. IFN-γ responses were associated with breast milk viral load, levels of macrophage inflammatory protein (MIP) 1α, MIP-1β, regulated upon activation, normal T-cell expressed, and secreted and stromal-cell derived factor 1 and subclinical mastitis. Univariate factors associated with infant HIV infection at 1 month postpartum included both detection and breadth of breast milk IFN-γ response (P = 0.08, P = 0.04, respectively), breast milk MIP-1β detection (P = 0.05), and plasma (P = 0.004) and breast milk (P = 0.004) viral load. In multivariate analyses adjusting for breast milk viral load and MIP-1β, breast milk IFN-γ responses were associated with an approximately 70% reduction in infant HIV infection [adjusted odds ratio (aOR) 0.29, 95% confidence interval (CI) 0.092-0.91], and each additional peptide pool targeted was associated with an approximately 35% reduction in infant HIV (aOR 0.65, 95% CI 0.44-0.97).

CONCLUSION

These data show breast milk HIV-gag-specific IFN-γ cellular immune responses are prevalent and may contribute to protection from early HIV transmission. More broadly, these data suggest breast milk cellular responses are potentially influential in decreasing mother-to-child transmission of viruses.

Distinct evolutionary pressures underlie diversity in simian immunodeficiency virus and human immunodeficiency virus lineages

Simian immunodeficiency virus (SIV) infection of rhesus macaques causes immune depletion and disease closely resembling human AIDS and is well recognized as the most relevant animal model for the human disease. Experimental investigations of viral pathogenesis and vaccine protection primarily involve a limited set of related viruses originating in sooty mangabeys (SIVsmm). The diversity of human immunodeficiency virus type 1 (HIV-1) has evolved in humans in about a century; in contrast, SIV isolates used in the macaque model evolved in sooty mangabeys over millennia. To investigate the possible consequences of such different evolutionary histories for selection pressures and observed diversity in SIVsmm and HIV-1, we isolated, sequenced, and analyzed 20 independent isolates of SIVsmm, including representatives of 7 distinct clades of viruses isolated from natural infection. We found SIVsmm diversity to be lower overall than HIV-1 M group diversity. Reduced positive selection (i.e., less diversifying evolution) was evident in extended regions of SIVsmm proteins, most notably in Gag p27 and Env gp120. In addition, the relative diversities of proteins in the two lineages were distinct: SIVsmm Env and Gag were much less diverse than their HIV-1 counterparts. This may be explained by lower SIV-directed immune activity in mangabeys relative to HIV-1-directed immunity in humans. These findings add an additional layer of complexity to the interpretation and, potentially, to the predictive utility of the SIV/macaque model, and they highlight the unique features of human and simian lentiviral evolution that inform studies of pathogenesis and strategies for AIDS vaccine design.

Acute HIV infection: it takes more than guts

PURPOSE OF REVIEW

To understand the cellular and molecular mechanisms of acute HIV pathogenesis.

RECENT FINDINGS

Recent studies have given us new insights into the mechanisms of acute HIV pathogenesis by demonstrating the 'systemic' destruction of the CD4 memory T cell compartment. This destruction occurs well before the emergence of a strong and broad immune response, highlighting the failure of the immune response to contain early viral infection and destruction. However, recent data also suggest that very few founder populations of cells are infected early, at the portal of entry, making them ideal targets for vaccine-induced immune responses that may aid in the effective control of early infection and transmission.

SUMMARY

HIV causes a massive destruction of memory CD4 T cells during the early acute phase of infection. This destruction proceeds largely in the absence of emerging antiviral immune responses, and severely disables the ability of the immune system to generate secondary immune responses. Early preservation of the memory CD4 compartment by shifting emphasis of antiretroviral therapeutic strategies to early treatment, and development of vaccines that can induce strong and broad immune responses, will be critical to prevent the destructive effects of early HIV infection.

Adoption of an "open" envelope conformation facilitating CD4 binding and structural remodeling precedes coreceptor switch in R5 SHIV-infected macaques

A change in coreceptor preference from CCR5 to CXCR4 towards the end stage disease in some HIV-1 infected individuals has been well documented, but the reasons and mechanisms for this tropism switch remain elusive. It has been suggested that envelope structural constraints in accommodating amino acid changes required for CXCR4 usage is an obstacle to tropism switch, limiting the rate and pathways available for HIV-1 coreceptor switching. The present study was initiated in two R5 SHIV(SF162P3N)-infected rapid progressor macaques with coreceptor switch to test the hypothesis that an early step in the evolution of tropism switch is the adoption of a less constrained and more "open" envelope conformation for better CD4 usage, allowing greater structural flexibility to accommodate further mutational changes that confer CXCR4 utilization. We show that, prior to the time of coreceptor switch, R5 viruses in both macaques evolved to become increasingly sCD4-sensitive, suggestive of enhanced exposure of the CD4 binding site and an "open" envelope conformation, and this correlated with better gp120 binding to CD4 and with more efficient infection of CD4(low) cells such as primary macrophages. Moreover, significant changes in neutralization sensitivity to agents and antibodies directed against functional domains of gp120 and gp41 were seen for R5 viruses close to the time of X4 emergence, consistent with global changes in envelope configuration and structural plasticity. These observations in a simian model of R5-to-X4 evolution provide a mechanistic basis for the HIV-1 coreceptor switch.

Effect of oral administration of ginseng stem-and-leaf saponins (GSLS) on the immune responses to Newcastle disease vaccine in chickens

This study was designed to evaluate the effect of oral administration of ginseng stem-and-leaf saponin (GSLS) on immune responses in chickens vaccinated with live Newcastle disease (ND) vaccines. In experiment 1, chickens were orally administered GSLS (2.5, 5, 10, and 20mg/kg) in drinking water for 3 days, and then intranasally vaccinated with ND vaccine. Hemagglutination inhibition (HI) test showed that the optimal dose of GSLS for enhancing HI titers was 5mg/kg. In experiment 2, chickens were fed with GSLS (5mg/kg) for 7, 5 or 3 days before vaccination. Result indicated that GSLS enhanced HI titers in a time-dependent manner. The order of the duration for drinking GSLS on increasing HI titers was 7 days>5 days>3 days. In experiment 3, chickens were fed with GSLS before or after immunization. Serum was sampled at a week interval for 5 weeks for HI test, splenic lymphocytes were prepared at weeks 2 and 4 after the booster immunization for lymphocyte proliferation test (LPT) and intestinal tissues were sampled at week 4 after the booster immunization for immunohistochemistry and histological examination. Results showed that HI titer, LPT, IgA+ cells and intestinal intraepithelial lymphocytes (iIELs) were significantly higher in chickens drinking GSLS before vaccination than those after vaccination. Therefore, oral administration of GSLS in drinking water at a dose of 5mg/kg for 7 days significantly increased systemic as well as gut mucosal immunity in chickens immunized with ND vaccine. Considering the immune potentiating effect of GSLS on ND vaccine, GSLS should be evaluated for its oral adjuvant effect on the immune response against other diseases such avian influenza and infectious bursal disease.

The gut mucosal viral reservoir in HIV-infected patients is not the major source of rebound plasma viremia following interruption of highly active antiretroviral therapy

Interruption of suppressive highly active antiretroviral therapy (HAART) in HIV-infected patients leads to increased HIV replication and viral rebound in peripheral blood. Effects of therapy interruption on gut-associated lymphoid tissue (GALT) have not been well investigated. We evaluated longitudinal changes in viral replication and emergence of viral variants in the context of T cell homeostasis and gene expression in GALT of three HIV-positive patients who initiated HAART during primary HIV infection but opted to interrupt therapy thereafter. Longitudinal viral sequence analysis revealed that a stable proviral reservoir was established in GALT during primary HIV infection that persisted through early HAART and post-therapy interruption. Proviral variants in GALT and peripheral blood mononuclear cells (PBMCs) displayed low levels of genomic diversity at all times. A rapid increase in viral loads with a modest decline of CD4(+) T cells in peripheral blood was observed, while gut mucosal CD4(+) T cell loss was severe following HAART interruption. This was accompanied by increased mucosal gene expression regulating interferon (IFN)-mediated antiviral responses and immune activation, a profile similar to those found in HAART-naive HIV-infected patients. Sequence analysis of rebound virus suggested that GALT was not the major contributor to the postinterruption plasma viremia nor were GALT HIV reservoirs rapidly replaced by HIV rebound variants. Our data suggest an early establishment and persistence of viral reservoirs in GALT with minimal diversity. Early detection of and therapy for HIV infection may be beneficial in controlling viral evolution and limiting establishment of diverse viral reservoirs in the mucosal compartment.

Correlation between CD4+ T-cell loss and Gag-specific T cells in different intestinal sites of chronically SIV-infected rhesus monkeys

OBJECTIVE

To determine the loss of CD4+ T cells and virus-specific cytotoxic T cells (CTL) in different mucosal sites of rhesus monkeys infected with simian immunodeficiency virus (SIV).

DESIGN

A cross-sectional comparative investigation of seven different mucosal sites from chronically SIV-infected rhesus monkeys was performed by analyzing blood and mucosal lymphocytes.

METHODS

Mucosal lymphocytes were isolated from duodenum, jejunum, ileum and colon as well as from vagina, cervix and uterus of SIV-infected rhesus monkeys at necropsy. CD4+ T cells and SIV-Gag-specific CTL were determined in blood and mucosal samples by flow cytometry.

RESULTS

A significant depletion of CD4+ T cells was observed in blood and all mucosal sites of SIV-infected rhesus monkeys compared to uninfected animals. But the mean percentage loss of CD4+ T cells varied between 66 and 95% between the different mucosal tissues. The frequency of CTL ranged between 0.4 and 2.4% with the highest proportions in vagina and cervix. Among the intestinal sites the mean levels of CTL correlated with mean percentage loss of CD4+ T cells.

CONCLUSION

A discriminative pronounced loss of CD4+ T cells among the mucosal tissues confirmed that viral replication affects different mucosal sites in a distinct way. Despite high levels of CTL, especially in vagina and cervix, the severe loss of mucosal CD4+ T cells could not be prevented during chronic SIV infection. However, within the four sites of the intestine a high virus-specific cellular immune response correlated with better preservation of CD4+ T cells.

Coreceptor use in nonhuman primate models of HIV infection

SIV or SHIV infection of nonhuman primates (NHP) has been used to investigate the impact of coreceptor usage on the composition and dynamics of the CD4+ T cell compartment, mechanisms of disease induction and development of clinical syndrome. As the entire course of infection can be followed, with frequent access to tissue compartments, infection of rhesus macaques with CCR5-tropic SHIVs further allows for study of HIV-1 coreceptor switch after intravenous and mucosal inoculation, with longitudinal and systemic analysis to determine the timing, anatomical sites and cause for the change in envelope glycoprotein and coreceptor preference. Here, we review our current understanding of coreceptor use in NHPs and their impact on the pathobiological characteristics of the infection, and discuss recent advances in NHP studies to uncover the underlying selective pressures for the change in coreceptor preference in vivo.

R5 clade C SHIV strains with tier 1 or 2 neutralization sensitivity: tools to dissect env evolution and to develop AIDS vaccines in primate models

Background

HIV-1 clade C (HIV-C) predominates worldwide, and anti-HIV-C vaccines are urgently needed. Neutralizing antibody (nAb) responses are considered important but have proved difficult to elicit. Although some current immunogens elicit antibodies that neutralize highly neutralization-sensitive (tier 1) HIV strains, most circulating HIVs exhibiting a less sensitive (tier 2) phenotype are not neutralized. Thus, both tier 1 and 2 viruses are needed for vaccine discovery in nonhuman primate models.

Methodology/Principal Findings

We constructed a tier 1 simian-human immunodeficiency virus, SHIV-1157ipEL, by inserting an “early,” recently transmitted HIV-C env into the SHIV-1157ipd3N4 backbone [1] encoding a “late” form of the same env, which had evolved in a SHIV-infected rhesus monkey (RM) with AIDS. SHIV-1157ipEL was rapidly passaged to yield SHIV-1157ipEL-p, which remained exclusively R5-tropic and had a tier 1 phenotype, in contrast to “late” SHIV-1157ipd3N4 (tier 2). After 5 weekly low-dose intrarectal exposures, SHIV-1157ipEL-p systemically infected 16 out of 17 RM with high peak viral RNA loads and depleted gut CD4⁺ T cells. SHIV-1157ipEL-p and SHIV-1157ipd3N4 env genes diverge mostly in V1/V2. Molecular modeling revealed a possible mechanism for the increased neutralization resistance of SHIV-1157ipd3N4 Env: V2 loops hindering access to the CD4 binding site, shown experimentally with nAb b12. Similar mutations have been linked to decreased neutralization sensitivity in HIV-C strains isolated from humans over time, indicating parallel HIV-C Env evolution in humans and RM.

Conclusions/Significance

SHIV-1157ipEL-p, the first tier 1 R5 clade C SHIV, and SHIV-1157ipd3N4, its tier 2 counterpart, represent biologically relevant tools for anti-HIV-C vaccine development in primates.

Relative transmissibility of an R5 clade C simian-human immunodeficiency virus across different mucosae in macaques parallels the relative risks of sexual HIV-1 transmission in humans via different routes

BACKGROUND

Worldwide, approximately 90% of all human immunodeficiency virus (HIV) transmissions occur mucosally; almost all involve R5 strains. Risks of sexual HIV acquisition are highest for rectal, then vaginal, and finally oral exposures.

METHODS

Mucosal lacerations may affect the rank order of susceptibility to HIV but cannot be assessed in humans. We measured relative virus transmissibility across intact mucosae in macaques using a single stock of SHIV-1157ipd3N4, a simian-human immunodeficiency virus encoding a primary R5 HIV clade C env (SHIV-C).

RESULTS

The penetrability of rhesus macaque mucosae differed significantly, with rectal challenge requiring the least virus, followed by vaginal and then oral routes (P = .031, oral vs vaginal; P < .001 rectal vs vaginal). These findings imply that intrinsic mucosal properties are responsible for the differential mucosal permeability. The latter paralleled the rank order reported for humans, with relative risk estimates within the range of epidemiological human studies. To test whether inflammation facilitates virus transmission--as predicted from human studies--we established a macaque model of localized buccal inflammation. Systemic infection occurred across inflamed but not normal buccal mucosa.

CONCLUSION

Our primate data recapitulate virus transmission risks observed in humans, thus establishing R5 SHIV-1157ipd3N4 in macaques as a robust model system to study cofactors involved in human mucosal HIV transmission and its prevention.

CD4 T cell subsets in the mucosa are CD28+Ki-67-HLA-DR-CD69+ but show differential infection based on alpha4beta7 receptor expression during acute SIV infection

BACKGROUND

CD4 T cell depletion in the mucosa has been well documented during acute HIV and SIV infections. The demonstration the HIV/SIVcan use the alpha4beta7 receptor for viral entry suggests that these viruses selectively target CD4 T cells in the mucosa that express high levels of alpha4beta7 receptor.

METHODS

Mucosal samples obtained from SIV infected rhesus macaques during the early phase of infection were used for immunophenotypic analysis. CD4 T cell subsets were sorted based on the expression of beta7 and CD95 to quantify the level of SIV infection in different subsets of CD4 T cells. Changes in IL-17, IL-21, IL-23 and TGFbeta mRNA expression was determined using Taqman PCR.

RESULTS

CD4 T cells in the mucosa were found to harbor two major population of cells; -25% of CD4 T cells expressed the alpha4(+)beta7(hi) phenotype, whereas the rest of the 75% expressed an alpha4(+)beta7(int) phenotype. Both the subsets were predominantly CD28(+)Ki-67(-)HLA-DR(-) but CD69(+), and expressed detectable levels of CCR5 on their surface. Interestingly, however, alpha4(+)beta7(hi)CD4 T cells were found to harbor more SIV than the alpha4(+)beta7(int) subsets at day 10 pi. Early infection was associated with a dramatic increase in the expression of IL-17, and IL-17 promoting cytokines IL-21, IL-23, and TGFbeta that stayed high even after the loss of mucosal CD4 T cells.

CONCLUSIONS

Our results suggest that the differential expression of the alpha4beta7 receptor contributes to the differences in the extent of infection in CD4 T cell subsets in the mucosa. Early infection is associated dysregulation of the IL-17 network in mucosal tissues involves other non-Th-17 cells that likely contributes to the pro-inflammatory environment in the mucosa during acute stages of SIV infection.

Treatment interruption to boost specific HIV immunity in acute infection

PURPOSE OF REVIEW

To understand the potential benefits and limitations of the treatment of acute, or primary, HIV infection followed by supervised treatment interruptions as a strategy to augment immune responses.

RECENT FINDINGS

Although this strategy led to the short-term control of virus replication after treatment interruption, follow-up data showed limited durability of control, and additional studies of short-term treatment in primary HIV infection show either a modest or no long-term benefit on CD4 cell counts and viral loads when compared with no therapy. Studies of gut-associated lymphatic tissue provide insights into the limitations of this approach because there has already been a massive destruction of the CD4 memory T-cell compartment by the time of symptomatic primary HIV infection by AIDS-associated retroviruses, which occurs before the emergence of cellular immune responses.

SUMMARY

There is currently no confirmed benefit of treatment of primary HIV infection by antiviral therapy alone in terms of disease progression and HIV-specific T-cell responses once therapy is interrupted. Supervised treatment interruption in acute HIV infection treated by antiviral therapy alone should probably not be used as a therapeutic strategy. This approach should be differentiated from early treatment itself, with or without immune augmentation, which deserves further investigation.

Mucosa and vaccine-induced immune protection in nonhuman primates

PURPOSE OF REVIEW

The purpose of this article is to review some of the recent progress in the development of HIV vaccines that induce immune responses in mucosal tissues that may correlate with protection of the mucosal CD4 T cell compartment.

RECENT FINDINGS

Mucosal tissues are the primary sites for viral entry and the resident CD4 T cells serve as readily available target cells for active infection. Viral entry is associated with a massive destruction of these cells. The resident CD4 cells are memory T cells and hence play an important role in the generation of secondary immune responses. Protecting these CD4 T cells is critical for controlling viral infection and for preserving immune competence. Numerous mucosal vaccine regimens currently under development have been shown to induce both B and T cell responses in mucosal tissues. Though induction of neutralizing antibodies still remains an elusive goal, the demonstration that antibodies can have a protective role through alternative mechanisms offers hope that humoral responses can be harnessed to yield a protective response in mucosal tissues.

SUMMARY

The mucosal immune system is highly compartmentalized and hence immunization regimens need to target mucosal tissues to be successful in inducing protective immune responses in mucosal tissues.

Multiple roles for chemokines in the pathogenesis of SIV infection

Chemokines are small chemoattractant cytokines involved in homeostatic and inflammatory immune cell migration. These small proteins have multiple functional properties that extend beyond their most recognized role in controlling cellular migration. The complex immunobiology of chemokines, coupled with the use of subsets of chemokine receptors as HIV-1 and SIV entry co-receptors, suggests that these immunomodulators could play important roles in the pathogenesis associated with infection by HIV-1 or SIV. This review provides an overview of the effects of pathogenic infection on chemokine expression in the SIV/macaque model system, and outlines potential mechanisms by which changes in these expression profiles could contribute to development of disease. Key challenges faced in studying chemokine function in vivo and new opportunities for further study and development of therapeutic interventions are discussed. Continued growth in our understanding of the effects of pathogenic SIV infection on chemokine expression and function and the continuing development of chemokine receptor targeted therapeutics will provide the tools and the systems necessary for future studies of the roles of chemokines in HIV-1 pathogenesis.

Mucosal T-cell responses to HIV: responding at the front lines

Mucosal surfaces of the body serve as the major portal of entry for human immunodeficiency virus (HIV). These tissues also house a majority of the body's lymphocytes, including the CD4(+) T cells that are the major cellular target for HIV infection. Mucosal surfaces are defended by innate and adaptive immune mechanisms, including secreted antibodies and CD8(+) cytotoxic T cells (CTL). CTL in mucosal lymphoid tissues may serve to limit viral replication, decreasing the host's viral burden as well as reducing the likelihood of sexual transmission to a naïve host. This review summarizes recent literature on HIV-specific T-cell responses in mucosal tissues, with an emphasis on the gastrointestinal tract.

Neutralization-sensitive R5-tropic simian-human immunodeficiency virus SHIV-2873Nip, which carries env isolated from an infant with a recent HIV clade C infection

Human immunodeficiency virus clade C (HIV-C) accounts for >56% of all HIV infections worldwide. To investigate vaccine safety and efficacy in nonhuman primates, a pathogenic, R5-tropic, neutralization-sensitive simian-human immunodeficiency virus (SHIV) carrying HIV-C env would be desirable. We have constructed SHIV-2873Ni, an R5-tropic SHIV carrying a primary pediatric HIV-C env gene isolated from a 2-month-old Zambian infant, who died within 1 year of birth. SHIV-2873Ni was constructed using SHIV-1157ipd3N4 (R. J. Song, A. L. Chenine, R. A. Rasmussen, C. R. Ruprecht, S. Mirshahidi, R. D. Grisson, W. Xu, J. B. Whitney, L. M. Goins, H. Ong, P. L. Li, E. Shai-Kobiler, T. Wang, C. M. McCann, H. Zhang, C. Wood, C. Kankasa, W. E. Secor, H. M. McClure, E. Strobert, J. G. Else, and R. M. Ruprecht. J. Virol. 80:8729-8738, 2006) as the backbone, since the latter contains additional NF-kappaB sites in the long terminal repeats to enhance viral replicative capacity. The parental virus, SHIV-2873Ni, was serially passaged through five rhesus monkeys (RMs); SHIV-2873Nip, the resulting passaged virus, was reisolated from the fourth recipient about 1 year postinoculation. SHIV-2873Nip was replication competent in RM peripheral blood mononuclear cells of all random donors tested and was exclusively R5 tropic, and its env gene clustered with HIV-C by phylogenetic analysis; its moderate [corrected] sensitivity to neutralization led to classification as a tier 2 [corrected] virus. Indian-origin RMs were inoculated by different mucosal routes, resulting in high peak viral RNA loads. Signs of virus-induced disease include depletion of gut CD4(+) T lymphocytes, loss of memory T cells in blood, and thrombocytopenia that resulted in fatal cerebral hemorrhage. SHIV-2873Nip is a highly replication-competent, mucosally transmissible, pathogenic R5-tropic virus that will be useful to study viral pathogenesis and to assess the efficacy of immunogens targeting HIV-C Env.

Role of immune activation in CD4+ T-cell depletion in HIV-1 infected Indian patients

OBJECTIVES

The correlation of immune activation with CD4(+) depletion and HIV-1 disease progression has been evidenced by several studies involving mainly clade B virus. However, this needs to be investigated in developing countries such as India predominately infected with clade C virus.

MATERIALS AND METHODS

In a cross-sectional study of 68 antiretroviral treatment naïve, HIV-1 infected Indian patients, we studied the association between CD4(+) T cells, plasma HIV-1 RNA levels, and immune activation markers using unadjusted and adjusted correlative analyses.

RESULTS

Significant negative correlations of higher magnitude were observed between the CD4(+) T cell percentages and plasma HIV-1 RNA levels in the study population when adjusted for the effects of immune activation markers. However, the negative association of CD4(+) T cells with immune activation markers remained unaffected when controlled for the effects of plasma HIV-1 RNA levels.

CONCLUSIONS

Our results support the important role of immune activation in CD4(+) T cell depletion and disease progression during untreated HIV-1 infection.

R5X4 viruses are evolutionary, functional, and antigenic intermediates in the pathway of a simian-human immunodeficiency virus coreceptor switch

To examine the pathway of the coreceptor switching of CCR5-using (R5) virus to CXCR4-using (X4) virus in simian-human immunodeficiency virus SHIV(SF162P3N)-infected rhesus macaque BR24, analysis was performed on variants present at 20 weeks postinfection, the time when the signature gp120 V3 loop sequence of the X4 switch variant was first detected by PCR. Unexpectedly, circulating and tissue variants with His/Ile instead of the signature X4 V3 His/Arg insertions predominated at this time point. Phylogenetic analysis of the sequences of the C2 conserved region to the V5 variable loop of the envelope (Env) protein showed that viruses bearing HI insertions represented evolutionary intermediates between the parental SHIV(SF162P3N) and the final X4 HR switch variant. Functional analyses demonstrated that the HI variants were phenotypic intermediates as well, capable of using both CCR5 and CXCR4 for entry. However, the R5X4 intermediate virus entered CCR5-expressing target cells less efficiently than the parental R5 strain and was more sensitive to both CCR5 and CXCR4 inhibitors than either the parental R5 or the final X4 virus. It was also more sensitive than the parental R5 virus to antibody neutralization, especially to agents directed against the CD4 binding site, but not as sensitive as the late X4 virus. Significantly, the V3 loop sequence that determined CXCR4 use also conferred soluble CD4 neutralization sensitivity. Collectively, the data illustrate that, similar to human immunodeficiency virus type 1 (HIV-1) infection in individuals, the evolution from CCR5 to CXCR4 usage in BR24 transitions through an intermediate phase with reduced virus entry and coreceptor usage efficiencies. The data further support a model linking an open envelope gp120 conformation, better CD4 binding, and expansion to CXCR4 usage.

Immune activation and inflammation in HIV-1 infection: causes and consequences

Thorough research on HIV is progressively enabling us to understand the intricate mechanisms that link HIV-1 infection to the onset of immunodeficiency. The infection and depletion of CD4(+) T cells represent the most fundamental events in HIV-1 infection. However, in recent years, the role played by chronic immune activation and inflammation in HIV pathogenesis has become increasingly apparent: quite paradoxically, immune activation levels are directly associated with HIV-1 disease progression. In addition, HIV-1-infected patients present intriguing similarities with individuals of old age: their immune systems are characterized by a loss of regenerative capacity and an accumulation of ageing T cells. In this review, we discuss the potential reasons for the establishment of sustained immune activation and inflammation from the early stages of HIV-1 infection, as well as the long-term consequences of this process on the host immune system and health. A simplified model of HIV pathogenesis is proposed, which links together the three major facets of HIV-1 infection: the massive depletion of CD4(+) T cells, the paradoxical immune activation and the exhaustion of regenerative capacity.

Gastrointestinal disease in simian immunodeficiency virus-infected rhesus macaques is characterized by proinflammatory dysregulation of the interleukin-6-Janus kinase/signal transducer and activator of transcription3 pathway

Gastrointestinal disease and inflammation are common sequelae of human and simian immunodeficiency virus (SIV) infection. Nevertheless, the molecular mechanisms that lead to gastrointestinal dysfunction remain unclear. We investigated regulation of the interleukin (IL)-6-JAK-STAT3 pathway in jejunum and colon, collected at necropsy, from 10 SIV-infected macaques with diarrhea (group 1), 10 non-SIV-infected macaques with diarrhea (group 2), and 7 control uninfected macaques (group 3). All group 1 and 2 macaques had chronic diarrhea, wasting, and colitis, but group 1 animals had more frequent and severe lesions in the jejunum. A significant increase in IL-6 and SOCS-3 gene expression along with constitutive STAT3 activation was observed in the colon of all group 1 and 2 macaques and in the jejunum of only group 1 macaques compared to controls. Further, in colon, histopathology severity scores correlated significantly with IL-6 (groups 1 and 2) and SOCS-3 (group 2) gene expression. In jejunum, a similar correlation was observed only in group 1 animals. Phosphorylated STAT3 (p-STAT3) was localized to lymphocytes (CD3+) and macrophages (CD68+), with fewer CD3+ lymphocytes expressing p-STAT3 in group 1 macaques. Despite high SOCS-3 expression, STAT3 remained constitutively active, providing a possible explanation for persistent intestinal inflammation and immune activation that may favor viral replication and disease pro-gression.

Do most lymphocytes in humans really reside in the gut?

It is widely believed that the gut, and particularly the lamina propria (LP) of the gut, contains most of the lymphocytes in humans. The strong depletion of CD4(+) T cells from the gut LP of HIV-infected patients was, therefore, suggested to be such a large, irreversible insult that it could explain HIV disease progression. However, reviewing data from different mammalian species, we found that only 5%-20% of all lymphocytes reside in the gut, and that only 1%-9% of the total lymphocyte number is located in the gut LP. Our findings suggest that spleen and lymph nodes, rather than the gut, are the largest immune compartments in mammals.

IFN-gamma-producing dendritic cells are important for priming of gut intraepithelial lymphocyte response against intracellular parasitic infection

The importance of intraepithelial lymphocytes (IEL) in immunoprotection against orally acquired pathogens is being increasingly recognized. Recent studies have demonstrated that Ag-specific IEL can be generated and can provide an important first line of defense against pathogens acquired via oral route. However, the mechanism involved in priming of IEL remains elusive. Our current study, using a microsporidial model of infection, demonstrates that priming of IEL is dependent on IFN-gamma-producing dendritic cells (DC) from mucosal sites. DC from mice lacking the IFN-gamma gene are unable to prime IEL, resulting in failure of these cells to proliferate and lyse pathogen-infected targets. Also, treatment of wild-type DC from Peyer's patches with Ab to IFN-gamma abrogates their ability to prime an IEL response against Encephalitozoon cuniculi in vitro. Moreover, when incubated with activated DC from IFN-gamma knockout mice, splenic CD8(+) T cells are not primed efficiently and exhibit reduced ability to home to the gut compartment. These data strongly suggest that IFN-gamma-producing DC from mucosal sites play an important role in the generation of an Ag-specific IEL response in the small intestine. To our knowledge, this report is the first demonstrating a role for IFN-gamma-producing DC from Peyer's patches in the development of Ag-specific IEL population and their trafficking to the gut epithelium.

Immunophenotypic alterations in acute and early HIV infection

To understand the extent of immune dysregulation in primary HIV infection (PHI) and the impact of antiretroviral therapy (ART) on restoring these abnormalities, we longitudinally evaluated 52 subjects (Acute-Treated (AT); Early-Treated (ET); Early Untreated (EU)) for markers of activation, proliferation, and function on T cells. ET and AT patients differed by 0.54 log viral load (VL) at baseline but did not differ thereafter by more than 0.34 log10 VL. AT subjects had higher CD8(+) T cell counts and expression of markers indicative of CD8(+) T cell activation (CD38), and proliferation (Ki67), at baseline, than ET subjects but were not different 48 weeks post-ART. Although acute PHI is marked by higher level of immune activation than early PHI, virologic and immunologic responses were similar post-ART, suggesting that the extent of immunologic recovery is not negatively impacted by a delay of treatment beyond the acute stage of disease.

Molecular mechanisms of primary and secondary mucosal immunity using avian infectious bronchitis virus as a model system

Although mucosal immune responses are critical for protection of hosts from clinical illness and even mortality caused by mucosal pathogens, the molecular mechanism of mucosal immunity, which is independent of systemic immunity, remains elusive. To explore the mechanistic basis of mucosal protective immunity, gene transcriptional profiling in mucosal tissues was evaluated after the primary and secondary immunization of animals with an attenuated avian infectious bronchitis virus (IBV), a prototype of Coronavirus and a well-characterized mucosal pathogen. Results showed that a number of innate immune factors including toll-like receptors (TLRs), retinoic-acid-inducible gene-1 (RIG-1), type I interferons (IFNs), complements, and interleukin-1 beta (IL-1β) were activated locally after the primary immunization. This was accompanied or immediately followed by a potent Th1 adaptive immunity as evidenced by the activation of T-cell signaling molecules, surface markers, and effector molecules. A strong humoral immune response as supported by the significantly up-regulated immunoglobulin (Ig) gamma chain was observed in the absence of innate, Th1 adaptive immunity, or IgA up-regulation after the secondary immunization, indicating that the local memory response is dominated by IgG. Overall, the results provided the first detailed kinetics on the molecular basis underlying the development of primary and secondary mucosal immunity. The key molecular signatures identified may provide new opportunities for improved prophylactic and therapeutic strategies to combat mucosal infections.

A decline in CCL3-5 chemokine gene expression during primary simian-human immunodeficiency virus infection

BACKGROUND

The CC-chemokines CCL3, CCL4 and CCL5 have been found to block the entry of CCR5-tropic HIV into host cells and to suppress the viral replication in vitro, but the in vivo role of endogenous CC-chemokines in HIV-1 infection is still incompletely understood.

METHODOLOGY/PRINCIPLE FINDINGS

In this study, the primate host CCL3, CCL4 and CCL5 gene expression was evaluated in response to simian-human immunodeficiency virus (SHIV) infection in rhesus macaque model. Five rhesus macaques were inoculated with CCR5-tropic SHIV(SF162P4). The mRNA levels of CCL3, CCL4 and CCL5 were measured by real-time PCR at post inoculation day (PID) 0, 7, 14, 21, 35, 56 and 180 in peripheral blood. In addition, a selected subset of samples from CXCR4-tropic SHIV(Ku1)-infected macaques was included with objective to compare the differences in CC-chemokine down-regulation caused by the two SHIVs. Gut-associated lymphoid tissues (GALT) collected from SHIV(SF162P4)-infected animals were also tested by flow cytometry and confocal microscopy to corroborate the gene expression results. Predictably, higher viral loads and CD4+ T cell losses were observed at PID 14 in macaques infected with SHIV(Ku1) than with SHIV(SF162P4). A decline in CC-chemokine gene expression was also found during primary (PID 7-21), but not chronic (PID 180) stage of infection.

CONCLUSIONS

It was determined that A) SHIV(SF162P4) down-regulated the CC-chemokine gene expression during acute stage of infection to a greater extent (p<0.05) than SHIV(Ku1), and B) such down-regulation was not paralleled with the CD4+ T cell depletion. Evaluation of CC-chemokine enhancing immunomodulators such as synthetic CpG-oligonucleotides could be explored in future HIV vaccine studies.

Estimating the infectivity of CCR5-tropic simian immunodeficiency virus SIV(mac251) in the gut

CD4+ T-cell depletion during acute human immunodeficiency virus infection occurs predominantly in the gastrointestinal mucosa. Using experimental data on SIV(mac251) viral load in blood and CD4+ T cells in the jejunum, we modeled the kinetics of CD4+ T-cell infection and death and estimated the viral infectivity. The infectivity of SIV(mac251) is higher than previously estimated for SHIV89.6P infection, but this higher infectivity is offset by a lower average peak viral load in SIV(mac251). Thus, the dynamics of target cell infection and death are remarkably similar between a CXCR4- and a CCR5-tropic infection in vivo.

FIV infection induces unique changes in phenotype and cellularity in the medial iliac lymph node and intestinal IEL

Studies of human immunodeficiency virus-1 (HIV-1)-infected patients and simian immunodeficiency virus (SIV)-infected macaques have identified profound depletion of CD4(+) T cells and expansion of CD8(+) T cells in the gastrointestinal lamina propria. Less attention has been given to CD8(+) intraepithelial lymphocytes (IEL), and no studies have concurrently examined inductive sites such as draining lymph nodes. Our preliminary data in the feline immunodeficiency virus (FIV) animal model suggested additional changes in IEL, and marked differences in the responses of lymph nodes draining different mucosal sites. To address this, we quantified the absolute leukocyte yield and examined the phenotype of cells from small intestinal IEL, mesenteric lymph node (MLN), and medial iliac lymph node (ILN) from chronically FIV-infected cats. The cellularity of the ILN was increased 530% in FIV-infected animals with an expansion of CD62L(+) cells, suggesting an increased population of naive T cells. The number of CD4(+), as well as CD8(+), T cells was increased in the ILN, resulting in a CD4:CD8 ratio greater than 1:1. In contrast, reduced cellularity, specific loss of CD4(+) T cells, and inversion of the CD4:CD8 ratio was observed in the MLN, which drains the intestine. In IEL, loss of CD8alpha, CD8beta, and CD4-expressing T cells was found in FIV-infected cats. Furthermore, expression intensity of CD8alpha and CD5, markers known to be important in T cell function, was markedly decreased on IEL. These findings expand the array of immune alterations induced by lentiviral infection and indicate that characterization of multiple mucosal sites will be necessary to fully understand the pathogenesis of HIV-1 infection.

Pathogenesis of HIV in the gastrointestinal tract

Gut-associated lymphoid tissue (GALT) is an important site for early HIV replication and severe CD4+ T-cell depletion. Initiation of highly active antiretroviral therapy leads to incomplete suppression of viral replication and substantially delayed and only partial restoration of CD4+ T cells in GALT compared with peripheral blood. Persistent viral replication in GALT leads to replenishment and maintenance of viral reservoirs. Increased levels of inflammation, immune activation, and decreased levels of mucosal repair and regeneration contribute to enteropathy. Assessment of gut mucosal immune system will provide better insights into the efficacy of highly active antiretroviral therapy in immune restoration and suppression of viral reservoirs.

SIV-specific CD8+ T cells express high levels of PD1 and cytokines but have impaired proliferative capacity in acute and chronic SIVmac251 infection

Programmed death-1 (PD-1) is a critical mediator of virus-specific CD8+ T-cell exhaustion. Here, we examined the expression of PD-1 on simian immunodeficiency virus (SIV)-specific CD8+ T cells and its possible involvement in regulation of cytokine production, proliferation, and survival of these cells. The majority of SIV-specific CD8+ T cells expressed a PD-1(high) phenotype, independent of their differentiation status, in all tissues tested. PD-1 expression gradually declined on CD8+ T cells specific for SIV-derived epitopes that had undergone mutational escape, indicating that antigen-specific TCR stimulation is the primary determinant of PD-1 expression. SIV-specific PD-1(high)CD8+ T cells produced IFN-gamma, TNF-alpha, and IL-2 under cognate peptide stimulation. While CD8+ T cells that proliferated in response to antigen had a PD-1(high) phenotype, it was determined that there was a reduced proliferative capacity of PD-1(high) compared with PD-1(low) SIV-specific CD8+ T cells. PD-1(high) SIV-specific CD8+ T cells were highly susceptible to cell death leading to loss of such cells after in vitro stimulation. Thus, PD-1 is a negative regulator of SIV-specific CD8+ T cells, operating predominantly through the induction of cell death. Manipulation of the interaction of PD-1 with its ligands could thus potentially restore the CD8+ T-cell responses in SIV infection.