Perinatally acquired HIV-2 infection diagnosed at 15 and 24 years of age

Evolution of the human immunodeficiency virus type 2 envelope in the first years of infection is associated with the dynamics of the neutralizing antibody response

BACKGROUND

Differently from HIV-1, HIV-2 disease progression usually takes decades without antiretroviral therapy and the majority of HIV-2 infected individuals survive as elite controllers with normal CD4⁺ T cell counts and low or undetectable plasma viral load. Neutralizing antibodies (Nabs) are thought to play a central role in HIV-2 evolution and pathogenesis. However, the dynamic of the Nab response and resulting HIV-2 escape during acute infection and their impact in HIV-2 evolution and disease progression remain largely unknown. Our objective was to characterize the Nab response and the molecular and phenotypic evolution of HIV-2 in association with Nab escape in the first years of infection in two children infected at birth.

RESULTS

CD4⁺ T cells decreased from about 50% to below 30% in both children in the first five years of infection and the infecting R5 viruses were replaced by X4 viruses within the same period. With antiretroviral therapy, viral load in child 1 decreased to undetectable levels and CD4+ T cells recovered to normal levels, which have been sustained at least until the age of 12. In contrast, viral load increased in child 2 and she progressed to AIDS and death at age 9. Beginning in the first year of life, child 1 raised high titers of antibodies that neutralized primary R5 isolates more effectively than X4 isolates, both autologous and heterologous. Child 2 raised a weak X4-specific Nab response that decreased sharply as disease progressed. Rate of evolution, nucleotide and amino acid diversity, and positive selection, were significantly higher in the envelope of child 1 compared to child 2. Rates of R5-to-X4 tropism switch, of V1 and V3 sequence diversification, and of convergence of V3 to a β-hairpin structure were related with rate of escape from the neutralizing antibodies.

CONCLUSION

Our data suggests that the molecular and phenotypic evolution of the human immunodeficiency virus type 2 envelope are related with the dynamics of the neutralizing antibody response providing further support for a model in which Nabs play an important role in HIV-2 pathogenesis.

Evolutionary and structural features of the C2, V3 and C3 envelope regions underlying the differences in HIV-1 and HIV-2 biology and infection

Background

Unlike in HIV-1 infection, the majority of HIV-2 patients produce broadly reactive neutralizing antibodies, control viral replication and survive as elite controllers. The identification of the molecular, structural and evolutionary footprints underlying these very distinct immunological and clinical outcomes may lead to the development of new strategies for the prevention and treatment of HIV infection.

Methodology/Principal Findings

We performed a side-by-side molecular, evolutionary and structural comparison of the C2, V3 and C3 envelope regions from HIV-1 and HIV-2. These regions contain major antigenic targets and are important for receptor binding. In HIV-2, these regions also have immune modulatory properties. We found that these regions are significantly more variable in HIV-1 than in HIV-2. Within each virus, C3 is the most entropic region followed by either C2 (HIV-2) or V3 (HIV-1). The C3 region is well exposed in the HIV-2 envelope and is under strong diversifying selection suggesting that, like in HIV-1, it may harbour neutralizing epitopes. Notably, however, extreme diversification of C2 and C3 seems to be deleterious for HIV-2 and prevent its transmission. Computer modelling simulations showed that in HIV-2 the V3 loop is much less exposed than C2 and C3 and has a retractile conformation due to a physical interaction with both C2 and C3. The concealed and conserved nature of V3 in the HIV-2 is consistent with its lack of immunodominancy in vivo and with its role in preventing immune activation. In contrast, HIV-1 had an extended and accessible V3 loop that is consistent with its immunodominant and neutralizing nature.

Conclusions/Significance

We identify significant structural and functional constrains to the diversification and evolution of C2, V3 and C3 in the HIV-2 envelope but not in HIV-1. These studies highlight fundamental differences in the biology and infection of HIV-1 and HIV-2 and in their mode of interaction with the human immune system and may inform new vaccine and therapeutic interventions against these viruses.

Parenteral transmission during excision and treatment of tuberculosis and trypanosomiasis may be responsible for the HIV-2 epidemic in Guinea-Bissau

BACKGROUND AND OBJECTIVE

The factors that led to the simultaneous emergence, decades ago, of HIV-1 in central Africa and HIV-2 in West Africa remain unclear. The low HIV-2-associated mortality enables epidemiological assessment of risk factors potentially relevant in the early stages of the epidemic. In Guinea-Bissau, its epicentre, HIV-2 became highly prevalent (approximately 15%) in cohorts of individuals born before 1962, but is now disappearing whereas HIV-1 prevalence is increasing. We sought to verify the hypothesis that parenteral transmission was the key factor in the building-up of the HIV-2 epidemic.

DESIGN

Cross-sectional community survey of 1608 individuals aged > or = 50 years in Bissau.

METHODS

Capillary blood was obtained for HIV serology. Associations between HIV-2 (alone or in dual HIV-1/HIV-2 infections) and exposures were measured with crude and adjusted odds ratios (AOR) and 95% confidence intervals (CI).

RESULTS

Prevalence of HIV-2 was higher in women (160/1063; 15.1%) than men (45/545; 8.3%, P < 0.001). Among women, excision (AOR, 1.54; 95% CI, 1.08-2.18) was independently associated with HIV-2, as were age and being widowed (AOR, 1.88; 95% CI, 1.29-2.74). Among men, HIV-2 was not associated with sexually transmitted infections or transactional sex. In an analysis comprising men and women that was adjusted for age, sex, ethnic group and marital status, HIV-2 was associated with having received injections for the treatment of tuberculosis (AOR, 2.12; 95% CI, 1.11-4.05) or trypanosomiasis (AOR, 1.75; 95% CI, 1.03-2.97).

CONCLUSIONS

Parenteral transmission through ritual excision and multiple injections during treatment of tuberculosis and trypanosomiasis contributed to the emergence of HIV-2 in Guinea-Bissau.

Phylogenetic demonstration of two cases of perinatal human immunodeficiency virus type 2 infection diagnosed in adulthood

HIV-2 infection was diagnosed in two patients 15 and 24 years of age and, thereafter, in their mothers. Epidemiological data suggested that vertical transmission was the most probable mode of infection in both patients (Mota-Miranda A, et al.: AIDS 2001;15:2460-2461). Phylogenetic analysis of env C2-C3 sequences from the patients and their mothers was used in an attempt to confirm or exclude the events of perinatal HIV-2 transmission. Sequences from each putative transmission pair formed monophyletic clusters in phylogenetic analysis, a clear indication of common ancestry. Interpatient nucleotide distances increased with the period of infection being consistent with long-term infection. In conclusion, the results are consistent with an epidemiological linkage between the viruses infecting each mother-child pair and support the occurrence of perinatal HIV-2 infection in both cases. Application of similar phylogeny methods to other suspected transmission cases may permit a better understanding of the epidemiology and molecular evolution of HIV-2.

Survival of HIV-1 and HIV-2 perinatally infected children in The Gambia

BACKGROUND

The risk of mother-to-child transmission (MTCT) of HIV-2 is much lower than that of HIV-1, but the long-term prognosis of perinatally infected HIV-2 children is unknown. We re-visited children who were part of a large MTCT study in The Gambia (conducted during 1993-1997), in order to compare the long-term survival of children perinatally infected with HIV-2 with that of seronegative and of HIV-1 infected children.

METHODS

Five to eight years' follow-up of a cohort of children born to HIV-negative, HIV-1 positive, and HIV-2 positive mothers.

RESULTS

Seven hundred and seventy-four children were followed up for a median of 6.6 years. Of 17 perinatally HIV-1 infected children, three were still alive on 1 July 2001, two had been lost to follow-up, and 12 had died. The median survival was 2.5 years. Of eight HIV-2 infected children five were still alive, none were lost to follow-up and three had died. The mortality hazards ratio of both HIV-1 [9.9; 95% confidence interval (CI), 5.2-19], and of HIV-2 infected children (3.9; CI, 1.2-12) was significantly increased compared with children of seronegative mothers. The mortality hazards ratio of HIV uninfected children of HIV-1 or HIV-2 infected mothers was not significantly increased compared to that of children of seronegative mothers (P = 0.17 and P = 0.5 respectively).

CONCLUSIONS

Children with perinatally acquired HIV-2 infection have a higher mortality than children of seronegative mothers. Guidelines for treatment of HIV-1 infected children should be used for treatment of HIV-2 infected children.