Effect of superimposed infections on viral replication in human immunodeficiency virus type 1-infected children

Clinical measles after measles virus challenge in simian immunodeficiency virus-infected measles virus-vaccinated rhesus monkeys

Understanding the impact of human immunodeficiency virus (HIV) infection on the clinical manifestations and kinetics of measles virus (MV) replication in MV-vaccinated and unvaccinated individuals is important for developing successful vaccine strategies for measles eradication. To model the pathogenesis of MV infection in MV-vaccinated and unvaccinated individuals infected with HIV, previously vaccinated and unvaccinated rhesus monkeys infected with simian immunodeficiency virus (SIV) were challenged with MV and monitored for clinical, virologic, and immunologic sequelae of infection. The magnitude and duration of MV viremia were unchanged by SIV infection. Nevertheless, clinical manifestations of MV infection were altered in animals with significant CD4(+) T lymphocyte loss. Importantly, 2 of the 3 SIV-infected monkeys with high titers of vaccine-induced MV-neutralizing antibody developed clinical evidence of MV infection. Thus, in this experimental animal model, a high-titer vaccine-induced MV-neutralizing antibody response does not protect against clinical manifestations of measles in the setting of a chronic acquired immunodeficiency syndrome virus infection.

Immunogenicity and effect of a virosomal influenza vaccine on viral replication and T-cell activation in HIV-infected children receiving highly active antiretroviral therapy

In order to evaluate the immunogenicity and the effect of a virosomal influenza vaccine on viral replication and T-cell activation in HIV-infected children receiving highly active antiretroviral therapy (HAART), 29 children infected with HIV-1 vertically (19 primed with a previous influenza vaccination and 10 who were not been immunized against influenza) were immunized with an intramuscular virosome-adjuvanted influenza vaccine. According to the European Agency for Evaluation of Medical Products (EMEA) criteria, the immunogenicity of the vaccine was adequate against all three influenza strains (A H1N1, A H3N2, and B) in the primed children, and against A H1N1 and A H3N2 in the unprimed children. After in vitro stimulation with vaccine antigens, the IFN-gamma levels in the peripheral blood mononuclear cells cultures increased significantly from a baseline level of 103.0 +/- 229.8 pg/ml to a 30-day level of 390.7 +/- 606.3 pg/ml (P < 0.05), with concentrations significantly higher (P < 0.05) in the primed children than in the unprimed children. No increase in plasma HIV-1 RNA or HIV-1 proviral DNA was observed in either subgroup, and the immunophenotype analyses demonstrated that the CD4+ cell counts and percentages, the CD4/CD8 ratio and activated lymphocytes remained stable in either group from baseline to 1 month after each vaccine dose. This study showed that the virosomal influenza vaccine does seem to be immunogenic in the majority of HIV-infected children receiving HAART and does not induce viral replication or T-cell activation. Given the possible influenza-related complications in children infected with HIV, these results support the use of this influenza vaccine in such patients.

The effect of Plasmodium falciparum malaria on peripheral and placental HIV-1 RNA concentrations in pregnant Malawian women

OBJECTIVE

To investigate the effect of placental Plasmodium falciparum malaria infection on peripheral and/or placental HIV-1 viral load.

DESIGN

A cross-sectional study of HIV-infected pregnant women, with and without placental malaria, delivering at Queen Elizabeth Central Hospital in Malawi.

METHODS

Peripheral blood samples were collected from consenting women and tested for HIV. HIV-infected women received nevirapine at the onset of labor. At delivery, placental blood and tissue specimens were collected. HIV-1 RNA concentrations were measured in peripheral and placental plasma samples, and malaria infection was determined by placental histopathology.

RESULTS

Of the 480 HIV-infected women enrolled, 304 had placental histopathology performed, of whom 74 (24.3%) had placental malaria. Compared with women without placental malaria, those with placental malaria had a 2.5-fold higher geometric mean peripheral HIV-1 RNA concentration (62,359 versus 24 814 copies/ml; P = 0.0007) and a 2.4-fold higher geometric mean placental HIV-1 RNA concentration (11,733 versus 4919 copies/ml; P = 0.008). In multivariate analyses, after adjusting for CD4 cell count and other covariates, placental malaria was associated with a 1.7-fold increase in geometric mean peripheral HIV-1 RNA concentration (47,747 versus 27,317 copies/ml; P = 0.02) and a 2.0-fold increase in geometric mean placental HIV-1 RNA concentration (9670 versus 4874 copies/ml; P = 0.03).

CONCLUSION

Placental malaria infection is associated with an increase in peripheral and placental HIV-1 viral load, which might increase the risk of mother-to-child transmission of HIV.

HIV-1 RNA and viral load

Viral load monitoring has become the standard of care in clinical practice to assess risk for disease progression and to monitor treatment response. Furthermore, viral load monitoring has contributed greatly to the understanding of HIV disease pathogenesis and response to various antiretroviral regimens, and has broadened its applications to include blood bank screening. The assays that are currently available are more sensitive, precise, and robust. There is now a better understanding of their limitations and the clinical scenarios and assay performance issues that result in variations of viral load results.

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.

Plasma HIV burden in Malawian children co-infected with rotavirus

Fifty-eight HIV-infected children with acute rotavirus diarrhea were tested for plasma HIV RNA. There was no difference between acute and convalescent mean viral loads, and little change in CD4 cell counts. Compared with the 16 children who died within 4 weeks, 31 survivors had slightly lower viral loads at presentation and significantly higher CD4 cell counts. Low CD4 cell counts, but not HIV-1-RNA concentrations, were predictive of Death. Local, enteric rotavirus infection did not appear to affect blood HIV viral load or CD4 cell counts in this small group of children.

Effect of clinical events on plasma HIV-1 RNA levels in persons with CD4+ T-lymphocyte counts of more than 500 x 10(6) cells/l

OBJECTIVE

Immune stimulation of CD4 lymphocytes is thought to enhance HIV-1 replication in vivo. Therefore, we sought to define the impact of clinical events identified as putative immune activators on the variability of plasma HIV-1 RNA levels in persons with CD4 cell counts greater than 500 x 10(6) cells/l.

DESIGN

We prospectively recorded clinical events and measured plasma HIV-1 RNA levels weekly for 24 weeks in 16 HIV-1-infected adults who were not receiving antiretroviral therapy and who had CD4 cell counts greater than 500 x 10(6) cells/l.

METHODS

Standard weekly interviews were conducted to capture potential immune activators (e.g., infections, immunizations, and allergic reactions). All plasma HIV-1 RNA levels were measured using the Amplicor HIV-1 Monitor assay (Roche Diagnostics, Branchburg, New Jersey, USA) according to the manufacturer's instructions.

RESULTS

Participants had remarkably stable viral loads during the 6 month study period. Infections were significantly more frequent during the 7 days prior to individual HIV-1 RNA measurements that exceeded the assay variation thresholds determined for this study (+/- 0.324 log) than during the comparable time periods preceding stable measurements (P = 0.023). As a group, the eight participants who had one to four HIV-1 RNA measurements that exceeded the thresholds experienced more infections and declining CD4 cell counts over the study course compared to the eight participants whose measurements all fell within the thresholds (P = 0.058 and 0.053 respectively).

CONCLUSIONS

Our study suggests that in untreated HIV-1-infected persons with CD4 cell count greater than 500 x 10(6) cells/l, viral load is generally quite stable, although acute minor infections are associated with transient fluctuations generally lasting no more than 1 week.

Viral Load Monitoring in HIV Infection

Measurement of HIV-1 viral load is now an accepted part of clinical practice for the determination of clinical prognosis and antiretroviral effectiveness in HIV infection. Consensus guidelines have been published on the appropriate use of this testing. Furthermore, recent advances in molecular technology have improved the sensitivity and reproducibility of viral load assays, and these improved assays have provided new insight into the pathogenesis of HIV disease. This article reviews new issues affecting viral load quantification, including viral subtypes, sex, compartmental differences, and other covariables.