Validation of night blindness reports among children and women in a vitamin A deficient population in rural Tanzania

Prenatal vitamin A deficiency impairs adaptive immune responses to pentavalent rotavirus vaccine (RotaTeq®) in a neonatal gnotobiotic pig model

Vitamin A deficiency (VAD) is associated with increased childhood mortality and morbidity in impoverished Asian and African countries, but the impact of VAD on rotavirus (RV) vaccine or infection is poorly understood. We assessed effects of gestational and dietary induced pre- and post-natal VAD and vitamin A supplementation on immune responses to a pentavalent rotavirus vaccine, RotaTeq(®) in a neonatal gnotobiotic pig model. Vaccine efficacy was assessed against virulent G1P[8] human rotavirus (HRV) challenge. VAD and vitamin A sufficient (VAS) piglets were derived from dietary VAD and VAS sows, respectively. VAD piglets had significantly lower levels of hepatic vitamin A compared to that of VAS piglets. RotaTeq(®)-vaccinated VAD piglets had 350-fold higher fecal virus shedding titers compared to vaccinated VAS piglets post-challenge. Only 25% of vaccinated non-vitamin A supplemented VAD piglets were protected against diarrhea compared with 100% protection rate in vaccinated non-supplemented VAS piglets post-challenge. Intestinal HRV specific immune responses were compromised in VAD piglets. Vaccinated VAD piglets had significantly lower ileal HRV IgG antibody secreting cell (ASC) responses (pre-challenge) and duodenal HRV IgA ASC responses (post-challenge) compared to vaccinated VAS piglets. Also, intestinal HRV IgA antibody titers were 11-fold lower in vaccinated VAD compared to vaccinated VAS piglets post-challenge. Persistently elevated levels of IL-8, a pro-inflammatory mediator, and lower IL-10 responses (anti-inflammatory) in vaccinated VAD compared to VAS piglets suggest more severe inflammatory responses in VAD piglets post-challenge. Moreover higher IFN-γ responses pre-challenge were observed in VAD compared to VAS piglets. The impaired vaccine-specific intestinal antibody responses and decreased immunoregulatory cytokine responses coincided with reduced protective efficacy of the RV vaccine against virulent HRV challenge in VAD piglets. In conclusion, VAD impaired antibody responses to RotaTeq(®) and vaccine efficacy. Oral supplementation of 100,000 IU vitamin A concurrent with RV vaccine failed to increase the vaccine efficacy in VAD piglets.

Serum retinol and xerophthalmia among a prison population in Papua New Guinea

PURPOSE

To estimate the prevalence of vitamin A deficiency (VAD) and one of its clinical manifestations, xerophthalmia, and examine the predictive value of nyctalopia and ocular signs for serum retinol concentrations among a prison population in Papua New Guinea.

METHODS

A cross-sectional study of 148 prisoners and 9 guards; all males aged ≥18 years. Interview-based questionnaire; ocular examination; serum retinol concentration determination.

RESULTS

Two guards had marginal (retinol <1.05-≥0.70 µmol/L) VAD. For prisoners: mean retinol was 0.84 ± 0.49 µmol/L; 43.9% (95% CI 35.9, 52.2) had VAD (retinol <0.70 µmol/L); 9.6% (95% CI 5.1, 17.0) self-reported nyctalopia prior to, and 36.1% (95% CI 27.7, 45.5) after incarceration; 10.9% (95% CI 6.7, 17.0) exhibited at least one sign of xerophthalmia (2 had fundus changes; all 4 with more than conjunctival xerosis alone had severe [<0.35 µmol/L] retinol deficiency). Prisoners with ocular signs were more likely than those without to have VAD (OR 10.4; 95% CI 2.5, 70.3; P < 0.001) and severe retinol deficiency (OR 19.1; 95% CI 5.5, 77.2; P < 0.001). Positive (PPV) and Negative (NPV) Predictive Values: of nyctalopia for any (PPV 62.9%; NPV 32.8%) and severe (PPV 25.7%; NPV 85.9%) retinol deficiency; of ocular signs for any (PPV 93.3%; NPV 38.2%) and severe (PPV 73.1%; NPV 87.8%) retinol deficiency, and VAD (PPV 86.5%, NPV 38.2%).

CONCLUSIONS

VAD and xerophthalmia were present in this prison population. There may be VAD in the wider community. The former needs remedy and the latter deserves investigation. Self-reported nyctalopia was not a useful indicator of retinol deficiency. Absence of ocular signs was unhelpful for ruling out VAD.

A investigação da cegueira noturna no grupo materno-infantil: uma revisão histórica

Objetivou-se neste estudo apresentar uma revisão histórica sobre a cegueira noturna, um indicador funcional da deficiência de vitamina A. Realizou-se uma revisão da literatura científica publicada no período de 1929 a 2005, nas bases de dados Medline, Lilacs, SciELO e dos comitês nacionais e internacionais de saúde e de micronutrientes, utilizando-se os termos night blindness, xerophthalmia, pregnancy, post partum women, newborn, children, vitamin A deficiency, micronutrient, deficiência de vitamina A, micronutriente, cegueira noturna, gestação, xeroftalmia. O reconhecimento da importância do indicador funcional da deficiência de vitamina A foi consagrado em 1996 pela Organização Mundial de Saúde, a partir da recomendação de uma entrevista padronizada para investigação da cegueira noturna. O método se caracteriza por apresentar facilidades operacionais, ser de baixo custo, além de permitir a sua aplicação tanto para o monitoramento do estado nutricional de pessoas e comunidades, quanto para a avaliação da eficácia de programas de intervenção. Entre gestantes e nutrizes, estudos recentes sugerem a utilidade deste indicador no diagnóstico dos casos de deficiência de vitamina A ainda no estágio subclínico da deficiência, sendo grande a sua concordância com indicadores bioquímicos. Ao longo dos anos, verifica-se também o reconhecimento deste indicador como um instrumento importante para a predição do risco de morbimortalidade no grupo materno-infantil.