Plasma HIV viral load in relation to season and to Plasmodium falciparum parasitaemia

Elevated Inflammation Associated with Markers of Neutrophil Function and Gastrointestinal Disruption in Pilot Study of Plasmodium fragile Co-Infection of ART-Treated SIVmac239+ Rhesus Macaques

Human immunodeficiency virus (HIV) and malaria, caused by infection with Plasmodium spp., are endemic in similar geographical locations. As a result, there is high potential for HIV/Plasmodium co-infection, which increases the pathology of both diseases. However, the immunological mechanisms underlying the exacerbated disease pathology observed in co-infected individuals are poorly understood. Moreover, there is limited data available on the impact of Plasmodium co-infection on antiretroviral (ART)-treated HIV infection. Here, we used the rhesus macaque (RM) model to conduct a pilot study to establish a model of Plasmodium fragile co-infection during ART-treated simian immunodeficiency virus (SIV) infection, and to begin to characterize the immunopathogenic effect of co-infection in the context of ART. We observed that P. fragile co-infection resulted in parasitemia and anemia, as well as persistently detectable viral loads (VLs) and decreased absolute CD4+ T-cell counts despite daily ART treatment. Notably, P. fragile co-infection was associated with increased levels of inflammatory cytokines, including monocyte chemoattractant protein 1 (MCP-1). P. fragile co-infection was also associated with increased levels of neutrophil elastase, a plasma marker of neutrophil extracellular trap (NET) formation, but significant decreases in markers of neutrophil degranulation, potentially indicating a shift in the neutrophil functionality during co-infection. Finally, we characterized the levels of plasma markers of gastrointestinal (GI) barrier permeability and microbial translocation and observed significant correlations between indicators of GI dysfunction, clinical markers of SIV and Plasmodium infection, and neutrophil frequency and function. Taken together, these pilot data verify the utility of using the RM model to examine ART-treated SIV/P. fragile co-infection, and indicate that neutrophil-driven inflammation and GI dysfunction may underlie heightened SIV/P. fragile co-infection pathogenesis.

Subsequent malaria enhances virus-specific T cell immunity in SIV-infected Chinese rhesus macaques

Background

Coinfection with HIV and Plasmodium parasites is fairly common, but the sequence of infection with these two pathogens and their impact on disease progression are poorly understood.

Methods

A Chinese rhesus macaque HIV and Plasmodium coinfection model was established to compare the impact of pre-existing and subsequent malaria on the progression of SIV infection.

Results

We found that a pre-existing malaria caused animals to produce a greater number of CD4⁺CCR5⁺ T cells for SIV replication, resulting in higher viral loads. Conversely, subsequent malaria induced a substantially larger proportion of CD4⁺CD28^highCD95^high central memory T cells and a stronger SIV-specific T cell response, maintained the repertoire diversity of SIV-specific T cell receptors, and generated new SIV-specific T cell clonotypes to trace SIV antigenic variation, resulting in improved survival of SIV-infected animals.

Conclusion

The complex outcomes of this study may have important implications for research on human HIV and malaria coinfection. The infection order of the two pathogens (HIV and malaria parasites) should be emphasized.

Immune Human Antibody Libraries for Infectious Diseases

The incident of two children in Europe who died of diphtheria due to a shortage of anti-toxin drugs has highlighted the need for alternative anti-toxins. Historically, antiserum produced from immunised horses have been used to treat diphtheria. Despite the potential of antiserum, the economical and medial concerns associated with the use of animal antiserum has led to its slow market demise. Over the years, new and emerging infectious diseases have grown to be a major global health threat. The emergence of drug-resistant superbugs has also pushed the boundaries of available therapeutics to deal with new infectious diseases. Antibodies have emerged as a possible alternative to combat the continuous onslaught of various infectious agents. The isolation of antibodies against pathogens of infectious diseases isolated from immune libraries utilising phage display has yielded promising results in terms of affinities and neutralizing activities. This chapter focuses on the concept of immune antibody libraries and highlights the application of immune antibody libraries to generate antibodies for various infectious diseases.

Evidence for spleen dysfunction in malaria-HIV co-infection in a subset of pediatric patients

The spleen has an important role in the clearance of malaria parasites, and the role of HIV co-infection on this process is yet to be described. Using a combination of histological and molecular methods, we systematically evaluated parasite load across multiple organs from HIV-positive and HIV-negative cases of an autopsy study of pediatric comatose children with malaria infection (n=103) in Blantyre, Malawi. Quantification of parasite load across organs was done using histology. A subset of cases was further characterized for parasite localization and stage of development using immunohistochemistry-based labeling of parasite and host cells (5 HIV-positive, 10 HIV-negative), and quantitative RT-PCR (qRT-PCR) of asexual and sexual-specific genes (4 HIV-positive, 5 HIV-negative). The results were compared with clinical information including HIV status. The HIV-positive rate was 21% for the group studied (20 of 95) and HIV-positive patients had a significantly shorter duration of time between onset of illness and death, and were significantly older than HIV-negative patients. We found that spleens of HIV-positive cases had significantly higher parasite loads compared with those of HIV-negative cases in each of the three methods we used: (i) standard histology, (ii) immunohistochemistry-based labeling of Plasmodium lactate dehydrogenase (pLDH), and (iii) molecular detection of asexual parasite transcript apical membrane antigen 1 (AMA1). Immunohistochemistry-based labeling of macrophage marker CD163 in a subset of spleens revealed fewer activated macrophages containing engulfed parasites and a greater number of free unphagocytosed parasites in the HIV-positive cases. The mechanism by which HIV infection is associated with more rapid progression to severe cerebral malaria disease is possibly impairment of parasite destruction by splenic macrophages, supported by published in vitro studies showing inefficient phagocytosis of malaria parasites by HIV-infected macrophages.

Plasmodium falciparum Infection Does Not Affect Human Immunodeficiency Virus Viral Load in Coinfected Rwandan Adults

In contrast to prior studies, mild malaria infection had no impact on HIV Viral Loads(VL) in Rwanda. Over fifty percent of patients prescribed ARV had detectable VL; 25% had genotypic resistance. Eleven percent of patients with mild malaria were newly diagnosed with HIV.

Background

 Plasmodium falciparum infection has been reported to increase human immunodeficiency virus (HIV) viral load (VL), which can facilitate HIV transmission. We prospectively studied the impact of mild P falciparum coinfection on HIV VL in Rwanda.

Methods

 We measured plasma HIV VL at presentation with malaria infection and weekly for 4 weeks after artemether-lumefantrine treatment in Rwandan adults infected with HIV with P falciparum malaria. Regression analyses were used to examine associations between malaria infection and HIV VL changes. Samples with detectable virus underwent genotypic drug-resistance testing.

Results

 We enrolled 28 HIV-malaria coinfected patients and observed 27 of them for 5 weeks. Three patients (11%) were newly diagnosed with HIV. Acute P falciparum infection had no significant effect on HIV VL slope over 28 days of follow-up. Ten patients with VL <40 copies/mL at enrollment maintained viral suppression throughout. Seventeen patients had a detectable VL at enrollment including 9 (53%) who reported 100% adherence to ARVs; 3 of these had detectable genotypic drug resistance.

Conclusions

 Unlike studies from highly malaria-endemic areas, we did not identify an effect of P falciparum infection on HIV VL; therefore, malaria is not likely to increase HIV-transmission risk in our setting. However, routine HIV testing should be offered to adults presenting with acute malaria in Rwanda. Most importantly, we identified a large percentage of patients with detectable HIV VL despite antiretroviral (ARV) therapy. Some of these patients had HIV genotypic drug resistance. Larger studies are needed to define the prevalence and factors associated with detectable HIV VL in patients prescribed ARVs in Rwanda.

HIV-1 Genetic Variability and Clinical Implications

Despite advances in antiretroviral therapy that have revolutionized HIV disease management, effective control of the HIV infection pandemic remains elusive. Beyond the classic non-B endemic areas, HIV-1 non-B subtype infections are sharply increasing in previous subtype B homogeneous areas such as Europe and North America. As already known, several studies have shown that, among non-B subtypes, subtypes C and D were found to be more aggressive in terms of disease progression. Luckily, the response to antiretrovirals against HIV-1 seems to be similar among different subtypes, but these results are mainly based on small or poorly designed studies. On the other hand, differences in rates of acquisition of resistance among non-B subtypes are already being observed. This different propensity, beyond the type of treatment regimens used, as well as access to viral load testing in non-B endemic areas seems to be due to HIV-1 clade specific peculiarities. Indeed, some non-B subtypes are proved to be more prone to develop resistance compared to B subtype. This phenomenon can be related to the presence of subtype-specific polymorphisms, different codon usage, and/or subtype-specific RNA templates. This review aims to provide a complete picture of HIV-1 genetic diversity and its implications for HIV-1 disease spread, effectiveness of therapies, and drug resistance development.

Effect of malaria on HIV/AIDS transmission and progression

Malaria and HIV are among the two most important global health problems of developing countries. They cause more than 4 million deaths a year. These two infections interact bidirectionally and synergistically with each other. HIV infection increases the risk of an increase in the severity of malaria infection and burdens of malaria, which in turn facilitates the rate of malaria transmission. Malaria infection is also associated with strong CD4+ cell activation and up-regulation of proinflammatory cytokines and it provides an ideal microenvironment for the spread of the virus among the CD4+ cells and for rapid HIV-1 replication. Additionally, malaria increases blood viral burden by different mechanisms. Therefore, high concentrations of HIV-1 RNA in the blood are predictive of disease progression, and correlate with the risk of blood-borne, vertical, and sexual transmission of the virus. Therefore, this article aims to review information about HIV malaria interactions, the effect of malaria on HIV transmission and progression and the implications related to prevention and treatment of coinfection.

Evidence for an increased risk of transmission of simian immunodeficiency virus and malaria in a rhesus macaque coinfection model

In sub-Saharan Africa, HIV-1 infection frequently occurs in the context of other coinfecting pathogens, most importantly, Mycobacterium tuberculosis and malaria parasites. The consequences are often devastating, resulting in enhanced morbidity and mortality. Due to the large number of confounding factors influencing pathogenesis in coinfected people, we sought to develop a nonhuman primate model of simian immunodeficiency virus (SIV)-malaria coinfection. In sub-Saharan Africa, Plasmodium falciparum is the most common malaria parasite and is responsible for most malaria-induced deaths. The simian malaria parasite Plasmodium fragile can induce clinical symptoms, including cerebral malaria in rhesus macaques, that resemble those of P. falciparum infection in humans. Thus, based on the well-characterized rhesus macaque model of SIV infection, this study reports the development of a novel rhesus macaque SIV-P. fragile coinfection model to study human HIV-P. falciparum coinfection. Using this model, we show that coinfection is associated with an increased, although transient, risk of both HIV and malaria transmission. Specifically, SIV-P. fragile coinfected macaques experienced an increase in SIV viremia that was temporarily associated with an increase in potential SIV target cells and systemic immune activation during acute parasitemia. Conversely, primary parasitemia in SIV-P. fragile coinfected animals resulted in higher gametocytemia that subsequently translated into higher oocyst development in mosquitoes. To our knowledge, this is the first animal model able to recapitulate the increased transmission risk of both HIV and malaria in coinfected humans. Therefore, this model could serve as an essential tool to elucidate distinct immunological, virological, and/or parasitological parameters underlying disease exacerbation in HIV-malaria coinfected people.

Effect of treating co-infections on HIV-1 viral load: a systematic review

Co-infections contribute to HIV-related pathogenesis and often increase viral load in HIV-infected people. We did a systematic review to assess the effect of treating key co-infections on plasma HIV-1-RNA concentrations in low-income countries. We identified 18 eligible studies for review: two on tuberculosis, two on malaria, six on helminths, and eight on sexually transmitted infections, excluding untreatable or non-pathogenic infections. Standardised mean plasma viral load decreased after the treatment of co-infecting pathogens in all 18 studies. The standardised mean HIV viral-load difference ranged from -0.04 log(10) copies per mL (95% CI -0.24 to 0.16) after syphilis treatment to -3.47 log(10) copies per mL (95% CI -3.78 to -3.16) after tuberculosis treatment. Of 14 studies with variance data available, 12 reported significant HIV viral-load differences before and after treatment. Although many of the viral-load reductions were 1.0 log(10) copies per mL or less, even small changes in plasma HIV-RNA concentrations have been shown to slow HIV progression and could translate into population-level benefits in lowering HIV transmission risk.

Maintenance of HIV-specific CD4+ T cell help distinguishes HIV-2 from HIV-1 infection

Unlike HIV-1-infected people, most HIV-2-infected subjects maintain a healthy CD4+ T cell count and a strong HIV-specific CD4+ T cell response. To define the cellular immunological correlates of good prognosis in HIV-2 infection, we conducted a cross-sectional study of HIV Gag-specific T cell function in HIV-1- and HIV-2-infected Gambians. Using cytokine flow cytometry and lymphoproliferation assays, we show that HIV-specific CD4+ T cells from HIV-2-infected individuals maintained proliferative capacity, were not terminally differentiated (CD57-), and more frequently produced IFN-gamma or IL-2 than CD4+ T cells from HIV-1-infected donors. Polyfunctional (IFN-gamma+/IL-2+) HIV-specific CD4+ T cells were found exclusively in HIV-2+ donors. The disparity in CD4+ T cell responses between asymptomatic HIV-1- and HIV-2-infected subjects was not associated with differences in the proliferative capacity of HIV-specific CD8+ T cells. This study demonstrates that HIV-2-infected donors have a well-preserved and functionally heterogeneous HIV-specific memory CD4+ T cell response that is associated with delayed disease progression in the majority of infected people.

Interactions between malaria and HIV infection-an emerging public health problem?

Recent evidence demonstrates interactions between malaria and HIV infection. HIV-infected people are more likely to experience clinical malaria, and acute malaria can up-regulate HIV replication, leading to higher plasma viral loads. This is most serious in pregnant women, where HIV infection increases the risk of placental malaria, leading to increased infant morbidity and mortality.

Contribution of immune activation to the pathogenesis and transmission of human immunodeficiency virus type 1 infection

The life cycle of human immunodeficiency virus type 1 (HIV-1) is intricately related to the activation state of the host cells supporting viral replication. Although cellular activation is essential to mount an effective host immune response to invading pathogens, paradoxically the marked systemic immune activation that accompanies HIV-1 infection in vivo may play an important role in sustaining phenomenal rates of HIV-1 replication in infected persons. Moreover, by inducing CD4+ cell loss by apoptosis, immune activation may further be central to the increased rate of CD4+ cell turnover and eventual development of CD4+ lymphocytopenia. In addition to HIV-1-induced immune activation, exogenous immune stimuli such as opportunistic infections may further impact the rate of HIV-1 replication systemically or at localized anatomical sites. Such stimuli may also lead to genotypic and phenotypic changes in the virus pool. Together, these various immunological effects on the biology of HIV-1 may potentially enhance disease progression in HIV-infected persons and may ultimately outweigh the beneficial aspects of antiviral immune responses. This may be particularly important for those living in developing countries, where there is little or no access to antiretroviral drugs and where frequent exposure to pathogenic organisms sustains a chronically heightened state of immune activation. Moreover, immune activation associated with sexually transmitted diseases, chorioamnionitis, and mastitis may have important local effects on HIV-1 replication that may increase the risk of sexual or mother-to-child transmission of HIV-1. The aim of this paper is to provide a broad review of the interrelationship between immune activation and the immunopathogenesis, transmission, progression, and treatment of HIV-1 infection in vivo.