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. 2024 Jul 23;16(8):1178.
doi: 10.3390/v16081178.

Elucidating the Immune Response to SARS-CoV-2: Natural Infection versus Covaxin/Covishield Vaccination in a South Indian Population

Agalya Vanamudhu  1 , Renuka Devi Arumugam  1 , Arul Nancy  2 , Nandhini Selvaraj  2 , Kadar Moiden  2 , Syed Hissar  1 , Uma Devi Ranganathan  1 , Ramalingam Bethunaickan  1 , Subash Babu  2 , Nathella Pavan Kumar  1
Affiliations

Elucidating the Immune Response to SARS-CoV-2: Natural Infection versus Covaxin/Covishield Vaccination in a South Indian Population

Agalya Vanamudhu et al. Viruses. .

Abstract

A natural infection or a vaccination can initially prime the immune system to form immunological memory. The immunity engendered by vaccination against COVID-19 versus natural infection with SARS-CoV-2 has not been well studied in the Indian population. In this study, we compared the immunity conferred by COVID-19 vaccines to naturally acquired immunity to SARS-CoV-2 in a South Indian population. We examined binding and neutralizing antibody (NAb) levels against the ancestral and variant lineages and assessed the ex vivo cellular parameters of memory T cells, memory B cells, and monocytes and finally measured the circulating cytokine response. COVID-19 vaccination stimulates heightened levels of IgG antibodies against the original strain of SARS-CoV-2, as well as increased binding to the spike protein and neutralizing antibody levels. This enhanced response extends to variant lineages such as B.1.617.2 (Delta, India), B.1.1.529 (Omicron, India), B.1.351 (Beta, South Africa), and B.1.1.7 (Alpha, UK). COVID-19 vaccination differs from SARS-CoV-2 infection by having increased frequencies of classical memory B cells, activated memory B and plasma cells, CD4/CD8 T cells of effector memory, effector cells, stem cell-like memory T cells, and classical and intermediate monocytes and diminished frequencies of CD4/CD8 T cells of central memory and non-classical monocytes in vaccinated individuals in comparison to those with natural infection. Thus, COVID-19 vaccination is characterized by enhanced humoral responses and robust activation of innate and memory T cell responses in comparison to natural infection in a South Indian population.

Keywords: B cells; COVID-19; Covaxin; Covishield; SARS-CoV-2; T cells; monocytes and cytokines.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as potential conflicts of interest.

Figures

Figure 1
Figure 1
COVID-19 vaccinated and infected cohorts. Study cohort characteristics. The timeline of immunizations and immune assays performed.
Figure 2
Figure 2
SARS-CoV-2 binding and neutralizing antibody response to COVID-19 vaccines and in individuals with COVID-19 infection. The plasma levels of SARS-CoV-2 binding antibodies of IgG [S] and Surrogate Virus Neutralization for wild-type and variant lineages of B.1.617.2 (Delta), B.1.1.529 (Omicron), B.1.351 (Beta, SA), and B.1.1.7 (Alpha, UK) in those with COVID-19 vaccination and COVID-19 infection. The data are represented as scatter plots, with each circle representing a single individual. The p-values were calculated using the non-parametric Mann–Whitney U test and with Holms correction for multiple comparisons.
Figure 3
Figure 3
Elevated B cell subsets in COVID-19 vaccinated individuals. Frequencies of B cell subsets in those with COVID-19 vaccination and COVID-19 infection. The data are represented as scatter plots, with each circle representing a single individual. The p-values were calculated using the non-parametric Mann–Whitney U test and with Holms correction for multiple comparisons.
Figure 4
Figure 4
Frequencies of T cell subsets in COVID-19 vaccinated individuals and in individuals with COVID-19 infection. The data are represented as scatter plots, with each circle representing a single individual. The p-values were calculated using the non-parametric Mann–Whitney U test and with Holms correction for multiple comparisons.
Figure 5
Figure 5
Frequencies of monocyte subsets in COVID-19 vaccinated individuals and individuals with COVID-19 infection. The data are represented as scatter plots, with each circle representing a single individual. The p-values were calculated using the non-parametric Mann–Whitney U test and with Holms correction for multiple comparisons.
Figure 6
Figure 6
Diminished inflammatory cytokine responses in COVID-19 vaccinated individuals. Plasma levels of a panel of inflammatory cytokines were measured in individuals with COVID-19 vaccination or COVID-19 infection. The data are represented as scatter plots, with each circle representing a single individual. The p-values were calculated using the non-parametric Mann–Whitney U test and with Holms correction for multiple comparisons.
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