Review of immunological and virological aspects as contributory factors in Sudden Unexpected Death in Infancy (SUDI).

Currently in South Africa research into sudden unexpected death in infancy (SUDI) is limited. The causes of sudden infant death syndrome (SIDS) remain obscure despite full medico-legal investigations inclusive of autopsy, scene visit and ancillary studies. Viral infections play an important role as a multitude of respiratory viruses have been detected in autopsy specimens and are implicated in these deaths. The specific contribution of viruses in the events preceding SIDS still warrants deciphering. Infancy is characterised by marked vulnerability to infections due to immaturities of the immune system that may only resolve by the age of 24 months. Routine viral screening of all SUDI cases at Tygerberg Forensic Pathology Service (FPS) Mortuary in Cape Town focuses on only a portion of respiratory viruses from lung and liver tissue. This review highlights important virological and immunological aspects regarding investigations into the infectious nature of SUDI, including the lack of national standardised guidelines for appropriate specimen collection at autopsy and subsequent laboratory analysis.

Antibody responses to vaccination among South African HIV-exposed and unexposed uninfected infants during the first 2 years of life.

HIV-exposed but uninfected (HEU) infants born to HIV-infected mothers from areas in the world with a high burden of infectious disease suffer higher infectious morbidity and mortality than their HIV unexposed uninfected (HUU) peers. Vaccination provides protection from infection. The possibility exists that altered response to vaccination contributes to the higher rate of infection in HEU than in HUU infants. While short-term, cross-sectional studies support this notion, it is unclear whether or not HEU infants develop long-term protective immune responses following the WHO extended program on immunization (EPI). Vaccine-specific antibody responses were compared between HEU and HUU infants from 2 weeks until 2 years of age in a longitudinal South African cohort. Total IgG and antibodies specific for Bordetella pertussis, Haemophilus influenzae type b (Hib), tetanus toxoid, hepatitis B virus (HepB), and measles virus were measured at multiple time points throughout the first 2 years of life. Prevaccine antibodies (maternal antibodies passively acquired) specific for tetanus were lower in HEU than in HUU infants, while prevaccine antibodies to HepB were higher in HEU than in HUU infants. Both groups responded similarly to tetanus, Hib, and HepB vaccination. HEU demonstrated stronger pertussis vaccine responses, developing protective titers 1 year earlier than HUU patients, and maintained higher anti-tetanus titers at 24 months of age. Vaccine-induced antibodies to measles virus were similar in both groups at all time points. Our results suggest that the current EPI vaccination program as practiced in South Africa leads to the development of vaccine-specific antibody responses that are equivalent in HEU and HUU infants. However, our data also suggest that a large fraction of both HEU and HUU South African infants have antibody titers for several infectious threats that remain below the level of protection for much of their first 2 years of life.