Human Parainfluenza virus (HPIV) causes lower respiratory tract infections (LRTI) mostly in young children. Respiratory viral infections may decline T cells in circulation and display enhanced pathogenicity. This study is aimed to analyze T cells alterations due to HPIV in children with LRTIs. Children (N = 152) with bronchitis or pneumonia, admitted in tertiary care hospitals were included in the study. Respiratory samples (throat or nasopharyngeal swabs) were taken and HPIV genotypes (1–4) were analyzed through RT-PCR. Peripheral blood T cells, CD3+, CD4+, CD8+, and CD19+, were analyzed in confirmed HPIV positive and healthy control group children through flow cytometry. The positivity rate of HPIV was 24.34% and the most prevalent genotype was HPIV-3 (20.40%). HPIV-1 and HPIV-2 were detected in 0.66% and 02% children respectively. The T lymphocyte counts were observed significantly reduced in children infected with HPIV-3. CD4+ cell (1580 ± 97.87) counts did not change significantly but the lowest CD8+ T cell counts (518.5 ± 74.00) were recorded. Similarly, CD3+ and CD19 cell ratios were also reduced. The CD4/CD8 ratio was significantly higher (3.12 ± 0.59) in the study population as compared to the control group (2.18 ± 0.654). Changes in the count of CD8+ T cells were more pronounced in patients with bronchiolitis and pneumonia. It is concluded that CD8+ T cells show a reduced response to HPIV-3 in children with severe LRTIs suggesting a strong association of these cells with disease severity.

人类副流感病毒（HPIV）主要在幼儿中引起下呼吸道感染（LRTI）。呼吸道病毒感染可能会减少循环中的 T 细胞并表现出更强的致病性。本研究旨在分析患有 LRTI 的儿童中由 HPIV 引起的 T 细胞改变。该研究纳入了三级医院收治的患有支气管炎或肺炎的儿童（N = 152）。采集呼吸道样本（喉咙或鼻咽拭子）并通过 RT-PCR 分析 HPIV 基因型 (1-4)。通过流式细胞术对确诊的 HPIV 阳性儿童和健康对照组儿童的外周血 T 细胞 CD3+、CD4+、CD8+ 和 CD19+ 进行分析。HPIV阳性率为24.34%，最常见的基因型为HPIV-3（20.40%）。HPIV-1 和 HPIV-2 分别在 0.66% 和 02% 的儿童中检出。感染 HPIV-3 的儿童中观察到 T 淋巴细胞计数显着减少。CD4+ 细胞 (1580 ± 97.87) 计数没有显着变化，但记录了最低的 CD8+ T 细胞计数 (518.5 ± 74.00)。同样，CD3+ 和 CD19 细胞比例也降低。研究人群的 CD4/CD8 比率 (3.12 ± 0.59) 显着高于对照组 (2.18 ± 0.654)。毛细支气管炎和肺炎患者的 CD8+ T 细胞计数变化更为明显。结论是，患有严重 LRTI 的儿童中 CD8+ T 细胞对 HPIV-3 的反应减弱，表明这些细胞与疾病严重程度密切相关。