Seroepidemiological correlations of antibodies to human herpesviruses and human immunodeficiency virus type 1 in African patients

Epstein-Barr virus (EBV) antibody changes over time in a general population cohort in rural Uganda, 1992-2008

BACKGROUND

Epstein-Barr virus (EBV) infection is ubiquitous and in sub-Saharan Africa, occurs early in life. In a population-based rural African cohort, we leveraged historical samples from the General Population Cohort (GPC) in Uganda to examine the epidemiology of infection with EBV over time, in the era of HIV.

METHODS

We used 9024 serum samples collected from the GPC in 1992, 2000, 2008, from 7576 participants across the age range (0-99 years of age) and tested for anti-EBV immunoglobulin G (IgG) antibodies to EAd, VCA, and EBNA-1 using a multiplex bead-based assay. The related gammaherpesvirus, Kaposi's sarcoma-associated herpesvirus (KSHV) seropositivity was also determined by detection of anti-KSHV IgG antibodies to K8.1 or ORF73 measured by recombinant protein enzyme-linked immunosorbent assay. Data on sex, age, and HIV serostatus were also collected. EBV seropositivity was modeled with age (excluding those under one year, who may have had maternal antibodies), sex, HIV serostatus, and KSHV serostatus using generalized linear mixed effects models to produce beta estimates.

RESULTS

More than 93% of children were EBV seropositive by one year of age. EBV seropositivity was significantly associated with KSHV seropositivity. Anti-EBNA-1 antibody levels decreased with increasing age and were lower on average in people living with HIV. In general, anti-EAd antibody levels increased with age, were higher in males and KSHV seropositive persons, but decreased over calendar time. Anti-VCA antibody levels increased with age and with calendar time and were higher in KSHV seropositive persons but lower in males.

CONCLUSIONS

This is the first study to identify factors associated with EBV antibodies across the entire life-course in rural sub-Saharan Africa. Consistent with other studies, EBV was near ubiquitous in the population by age one year. Patterns of antibodies show changes by age, sex and calendar time, but no association with HIV was evident, suggesting no relationship between EBV sero-epidemiology and the spread of HIV in the population over time in Uganda.

Of mice and men: Different functions of the murine and human 2B4 (CD244) receptor on NK cells

2B4 was initially discovered on murine NK cells and T cells displaying non-MHC dependent cytotoxicity. Human 2B4 was cloned based on sequence homology with mouse 2B4. Recent evidence suggests that the function of this receptor might be different in the two species. Human 2B4 activates NK cell cytotoxicity and interferon gamma production when engaged by CD48, its ligand, on target cells. This activating function of human 2B4 requires recruitment of the SH2 domain containing molecule, SLAM-associated protein or SAP. In the absence of SAP in human NK cells, as occurs in immature NK cells or NK cells from X-linked lymphoproliferative disorder (XLPD) patients, human 2B4 acts as an inhibitory receptor. In contrast, in vitro and in vivo studies using 2B4-deficient mice suggest that the major function of mouse 2B4 is to inhibit murine NK cell functions when triggered by CD48 on target cells, although there are reports of activating function of murine 2B4. This inhibitory function of murine 2B4 is mediated by EAT-2, ERT and possibly other phosphatases like SHP-1 and SHIP. 2B4-SAP interaction in mouse NK cells might be a low affinity one and might not be physiologically relevant considering the inhibitory function of 2B4. This suggests that mouse and human 2B4 diverged functionally with the evolution of greater affinity between 2B4 and SAP in the human species. We speculate that evolutionary pressure from viral infections, possibly EBV, might have led to the emergence of this association and activating function of 2B4 in humans.

Human herpesvirus 6

Human herpesvirus 6 variant A (HHV-6A) and human herpesvirus 6 variant B (HHV-6B) are two closely related yet distinct viruses. These visuses belong to the Roseolovirus genus of the betaherpesvirus subfamily; they are most closely related to human herpesvirus 7 and then to human cytomegalovirus. Over 95% of people older than 2 years of age are seropositive for either or both HHV-6 variants, and current serologic methods are incapable of discriminating infection with one variant from infection with the other. HHV-6A has not been etiologically linked to any human disease, but such an association will probably be found soon. HHV-6B is the etiologic agent of the common childhood illness exanthem subitum (roseola infantum or sixth disease) and related febrile illnesses. These viruses are frequently active and associated with illness in immunocompromised patients and may play a role in the etiology of Hodgkin's disease and other malignancies. HHV-6 is a commensal inhabitant of brains; various neurologic manifestations, including convulsions and encephalitis, can occur during primary HHV-6 infection or in immunocompromised patients. HHV-6 and distribution in the central nervous system are altered in patients with multiple sclerosis; the significance of this is under investigation.

No direct relationship between HIV1/2 infection and HHV-6 antibody response in a large-scale European and African trial

BACKGROUND

Tropism of both human herpesvirus-6 (HHV-6) and human immunodeficiency virus (HIV) for CD4+ lymphocytes, and several studies on HIV enhancer transactivation by HHV-6 have suggested that HHV-6 could be implicated as a cofactor in the progression of HIV infection to AIDS.

OBJECTIVES

To determine if there is any relationship between HHV-6 infection and the course of HIV infection.

STUDY DESIGN

527 French and 558 African sera (210 from Senegal, 348 from Ivory Coast) were tested for HHV-6 titers by immunofluorescence assay (IFA). For each country, patients studied were divided into several groups; those with AIDS, those who were HIV-seropositive but symptomless, and HIV-seronegative patients.

RESULTS

No statistical difference could be found between HHV-6 prevalences or HHV-6 geometric mean titers obtained for each geographical area in the different HIV-1- and/or HIV-2-positive and HIV-negative groups. HIV patients with clinical manifestations of AIDS did not differ in percent seropositivity or distribution of titers from the HIV-asymptomatic patients or HIV-seronegative patients.

CONCLUSION

These findings suggest that there is no correlation between HHV-6 antibodies and HIV seropositivity or with the stage of HIV infection.

Evaluation of a new reagent for anti-cytomegalovirus and anti-Epstein-Barr virus immunoglobulin G

The Enzygnost alpha method was tested against the complement fixation test and anti-VCA immunofluorescence to determine the respective titers of anti-cytomegalovirus and anti-Epstein-Barr virus immunoglobulin G antibodies. For cytomegalovirus, the Enzygnost results showed 97.99% agreement with the readings obtained by the alternative method, with 100% sensitivity and 93.7% specificity. For Epstein-Barr virus, Enzygnost showed 97.71% agreement, 100% sensitivity, and 91.11% specificity.

HIV-1 and parasitic infections in rural Tanzania

A sample of 300 sexually-active adults was selected at random from patients, from the rural area of Malenga Makali, Tanzania, who were attending a dispensary because they had diarrhoea of at least 2 weeks' duration. The potential associations between the patient's health (in terms of the World Health Organization's clinical definition of AIDS), HIV-1 seroprevalence and malaria and other parasitic infections were then investigated. Although, HIV-1 seroprevalence was 20.6% overall, the level of seroprevalence was directly correlated with the distance between the patients' home villages and the nearest main road. Strict application of the clinical definition of AIDS gave 98.7% specificity, 46% sensitivity and a predictive value of 90.6% when validated by HIV-1 seropositivity. Although malaria infection was more common in HIV-1 seropositives than in the seronegatives, the intensity of the Plasmodium falciparum infections, intestinal amoebiasis and giardiasis did not appear to be correlated with HIV-1 infection. In contrast, intestinal infections with Cryptosporidium parvum and Isospora belli were virtually restricted to HIV-1 seropositive individuals who had had diarrhoea for a relatively long time.